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Title: Building And Flying An Aeroplane
Author: Hayward, Charles B.
Language: English
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AEROPLANE ***
This file was produced from page images at the Internet Archive.
Transcriber’s Note
This book was transcribed from scans of the original found at the
Internet Archive and at Google Books. I have rotated some images. Tables
are treated as images. There are two versions of this book: the first
contains both parts and the second is published as two volumes with
Examination Papers at the end of each, which the student would return to
the American School of Correspondence for credit. I have included these
Examination Papers at the end of each part.
[Illustration: TWENTY HORSEPOWER NEUPORT MONOPLANE MAKING A LANDING
_This Photograph Protected By International Copyright_]
BUILDING AND FLYING
AN AEROPLANE
A PRACTICAL HANDBOOK COVERING THE DESIGN,
CONSTRUCTION, AND OPERATION OF
AEROPLANES AND GLIDERS
By
CHARLES B. HAYWARD
MEMBER, THE AERONAUTICAL SOCIETY; MEMBER, SOCIETY OF AUTOMOBILE
ENGINEERS; FORMERLY SECRETARY, SOCIETY OF AUTOMOBILE ENGINEERS;
FORMERLY ENGINEERING EDITOR, THE AUTOMOBILE
ILLUSTRATED
CHICAGO
AMERICAN SCHOOL OF CORRESPONDENCE
1912
Copyright 1912 by
American School of Correspondence
Entered at Stationers’ Hall, London
All Rights Reserved
BUILDING AND FLYING AN AEROPLANE
INTRODUCTION
The field of aviation has, from the inception of successful flight by
the Wright Brothers, had a wonderful fascination for the amateur
mechanic. At first the strong element of mystery in the movements of
this monster man-ridden bird appalled him, but an examination of
approved designs has removed the mystery and has assured him that he
can, with his own hands and at a cost well within his reach, build his
own machine in his own back yard.
But in this ease of accomplishment lies a danger, namely, the belittling
of the value of accurate design and the misjudging of the true
importance of small things. The inventive mind usually believes itself
capable of making improvements in almost anything, and the aeroplane
inventor is no exception to the rule. Filled with the confidence born of
ignorance, and with only the knowledge he has gleaned from newspaper and
magazine accounts of the popular types of machines, he works out a brand
new design. The usual, in fact, the invariable result is failure,
discouragement, and a loss of time and money. How much more sensible for
the young inventor to build his first machine without varying in one
particular from a tried and proved model, leaving his flights of
inventive fancy to his later years of maturer knowledge and judgment.
The author of this little book has followed, in both biplane and
monoplane models, the well-known types of Curtiss and Bleriot, choosing
each as the simplest representative of its class in construction and
design. It is hoped that the book may not only be of assistance to the
amateur builder, but may also be the means of turning the too confident
inventor into safer and more established paths.
[Illustration: HARRY ATWOOD IN HIS BURGESS HYDROAEROPLANE SKIMMING OVER
THE SURFACE OF MARBLEHEAD BAY]
BUILDING AND FLYING AN AEROPLANE ..................................
INTRODUCTION ....................................................
PART 1 ..........................................................
BUILDING AEROPLANE MODELS .....................................
BUILDING A GLIDER .............................................
BUILDING A CURTISS BIPLANE ....................................
DETAILS OF CONSTRUCTION .......................................
PART II .........................................................
BUILDING A BLERIOT MONOPLANE ..................................
ART OF FLYING .................................................
ACCIDENTS AND THEIR LESSONS ...................................
AMATEUR AVIATORS ..............................................
PART 1
One of the commonest phases of interest in aviation is the desire to
build a flying machine. In fact, this is very frequently the first thing
the experimenter undertakes after having gone into the theory of flight
to some extent. Only too often, no effort whatever is made to get beyond
theory and the machine is an experiment in every sense of the word. An
experience of this nature is costly—far more so than is agreeable for
the student, and is likely to result in disgusting him with aviation
generally. There are hundreds of schemes and principles in the art that
have been tried again and again with the same dismal failure in the end.
Refer to the story of the Wright Brothers and note how many things they
mention having tried and rejected as worse than useless. About once in
so often someone "rediscovers" some of these things and, having no
facilities for properly investigating what patent attorneys term the
"prior art" (everything that has gone before, from the beginning of
invention, or at least patented invention) becomes possessed of the idea
that he has hit upon something entirely novel and wholly original. There
is no desire in the present work to discourage the seeker after new
principles—undoubtedly there are many yet to be discovered. The art of
flight is in its infancy and there is still a great deal to be learned
about it, but there is no more discouraged inventor than he
who-discovers a principle and, after having experimented with it at
great expense, finds that it is only one of many things that numerous
others have spent considerable money in proving fallacious, a great many
years ago.
If it be your ambition to build a flying machine and you believe that
you have discovered something new of value, it will be to your interest
to retain a responsible patent attorney to advise you as to the prior
art, before expending any money on its construction. You will find it
very much more economical in the end. There are probably not more than
half a dozen men alive in this country today who "know all the schemes
that won’t work." The average seeker after knowledge is assuredly not
likely to be one of these few, so that until he knows he is working
along new and untried lines that give promise of success, it will pay
him to stick to those that have proved successful in actual practice. In
other words, to confine his efforts in the building line to a machine
that experience has demonstrated will fly if properly constructed and,
what is of equal importance, skilfully handled. Build a machine, by all
means, if you have the opportunity. It represents the best possible
experience. But as is pointed out under the "Art of Flying," take a few
lessons from some one who knows how to fly, before risking your neck in
what is to you a totally untried element. Even properly designed and
constructed machines are not always ready to fly. An aeroplane needs
careful inspection of every part and adjustment before it is safe to
take to the air in it, and to be of any value this looking-over must be
carried out by an experienced eye.
BUILDING AEROPLANE MODELS
The student may enter upon the business of building to any extent that
his inclination or his financial resources or his desire to experiment
may lead him. The simplest stage, of course, is that of model building
and there is a great deal to be learned from the construction and flying
of experimental models. This has become quite a popular pastime in the
public schools and some very creditable examples of work have been
turned out. The apparent limitations of these rubber-band driven models
need not discourage the student, as some of the school-boy builders have
succeeded in constructing models capable of flying a quarter mile in
still air and their action in the air is wonderfully like the full-sized
machines.
*Models with Rubber-Band Motor*. The limitations of the available power
at command must be borne in mind, as the rubber-band motor is at best
but a poor power plant. It is accordingly not good practice to have the
spread of the main planes exceed 24 inches, though larger successful
models have been built. In attempting to reproduce any of the well-known
models, difficulty is often experienced in accommodating the rubber-band
motor to them, as even where the necessary space is available, its
weight throws the balance out entirely, and the result is a model that
will not fly. This has led to the production of many original creations,
but these, while excellent flyers, would not serve as models for larger
machines, as of necessity they have been designed around their power
plants. The rubber bands for this purpose may be purchased of any
aeronautic supply house. The most practical method of mounting the motor
is to attach it to the rear end of the fuselage, usually a single stick,
which is accordingly made extra long for that purpose. At the other end
it is attached to a bent wire fastened to the propeller in order to
revolve the latter. An easy way to wand up the motor is to employ an
ordinary egg beater, modified as described below, or a hand drill,
inserting a small wire yoke in the jaws in place of the usual drill, or
bit. This yoke is placed so as to engage the propeller blades, and the
latter is then turned in the opposite direction, storing energy in the
rubber band by twisting its strands tightly.
[Illustration: Fig. 1. Details of Main Frame of Rubber-Band Driven
Aeroplane Model]
For those students who do not care to undertake an original design at
the outset, or who would prefer to have the experience gained by
building from a plan that has already been tried, before attempting to
originate, the following description of a successful model is given.
This model can not only be made for less than the models sold at three
to five dollars, but is a much more efficient flyer, having frequently
flown 700 feet.
_Main Frame_. The main frame of the model monoplane consists of two
strips A of spruce, each 28 inches long, and measuring in cross section
1/4 by 3/8 of an inch. As shown in Fig. 1, the two strips are tied
together at the front with strong thread and are then glued, the glue
being spread over and between the windings of the thread, Figs. 1 and 2.
The rear ends of these strips are spread apart 4 1/4 inches to form a
stout triangular frame, and are tied together by cross bars of bamboo B
and C which are secured to the main strips A by strong thread and glue.
[Illustration: Fig. 2. Details of Forward Skids of Aeroplane Model]
_Propellers_. The propellers _D_ are two in number and are carried by
the two long strips _A_. Each propeller is 5 inches in diameter, and is
whittled out of a single block of white pine. The propellers have a
pitch of about 10 inches. After the whittling is done they are
sandpapered and coated with varnish. The thickness of the wood at the
hub _E₂_, Fig. 3, of the propeller should be about 5/8 inch. At the rear
ends of the strips _A_, bearing blocks _E₁_ are secured. These bearing
blocks are simply small pieces of wood projecting about 5/8 inch
laterally from the strips _A_. They are drilled to receive a small metal
tube _T₂_ (steel, brass, or copper), through which tube the propeller
shaft _T₁_ passes.
[Illustration: Fig. 3. Details of Propeller and Rudder of Aeroplane
Model]
The propeller shaft itself consists of a piece of steel wire passing
through the propeller hub and bent over the wood, so that it can not
turn independently of the propeller. Any other expedient for causing the
propeller to turn with the shaft may obviously be employed. Small metal
washers _T₃_, at least three in number, are slipped over the propeller
shaft so as to lie between the propeller and the bearing block.
That portion of the propeller shaft which projects forwardly through the
bearing block _E₁_ is bent to form a hook _T₄_. To the hook _T₁_ rubber
strips _T₂_ by which the propellers are driven, are secured. The rubber
strips are nearly as long as the main strips _A_. At their forward ends
they are secured to a fastening consisting of a double hook _G H_, the
hook _G_ lying in a horizontal plane, the hook _H_ in a vertical plane.
The hook holds the rubber strips, as shown in Figs. 1 and 4, while the
hook _H_ engages a hook _T_. This hook is easily made by passing a strip
of steel wire through the meeting ends of the main strips _A_, the
portions projecting from each side of the strips being bent into the
hooks _I_.
_Skids_. Three skids are provided, on which the model slides, one at the
forward end, and two near the rear end. All are made of bamboo. As shown
in Fig. 2 the front skid may be of any length that seems desirable. A
6-inch piece of bamboo will probably answer most requirements. This
piece _N_ is bent in opposite directions at the ends to form arms _Z_
and _U_, The arm _Z_ is secured to the forward ends of the two strips
_A_, constituting the main frame, by means of thread and glue. The
strips and skid are not held together by the same thread, but the skid
is attached to the two strips after they have been wound. Hence, there
are two sets of windings of thread, one for the two strips _A_
themselves, and another for the skid and the strips. Strong thread and
glue should be used, as before. In order to stiffen the skid, two bamboo
struts _W_ will be found necessary. These are bent over at the ends to
form arms _V₁_, Fig. 2. Each of the arms is secured to the under side of
a strip _A_ by strong thread and glue. The arms _X_ are superimposed and
tied to the bamboo skid _V_ with strong thread and glue.
[Illustration: Fig. 4. Details of Rear Skids on Aeroplane Model]
The two rear skids, of which one is shown in Fig. 5, consist each of two
5-inch strips of bamboo _S_, likewise bent at either end in opposite
directions to form arms _S₂_ and _S₃_, The arms _S₂_ are fastened to the
strips _A_ by strong thread and glue. To stiffen the skids a strut _C₁_
is provided for each skid. Each strut consists of a 3-inch strip of
bamboo bent over so as to form arms _C₂_. Strong thread and glue are
employed to fasten each strut in position on the strip and the skid. In
the crotch of the triangular space _B₁_, a tie bar _J_, Figs. 4 and 5,
is secured by means of thread and glue. This tie bar connects the two
skids, as shown in Figs. 1 and 4, and serves to stiffen them. The
triangular space _B₁_ is covered with paper, preferably bamboo paper. If
bamboo paper is not available, parchment or stiff light paper of some
kind may be used. It does not need to be waterproof. Thus triangular
fins are formed which act as stabilizing surfaces.
[Illustration: Fig. 5. Enlarged Details of One Rear Skid, Aeroplane
Model]
_Main Planes_. The main planes are two in number, but are different in
size. Contrary to the practice followed in large man-carrying
monoplanes, the front supporting surface is comparatively small in area
and the rear supporting surface comparatively large. These supporting
surfaces _L_ and _P_ are shown in detail in Figs. 6 and 7. It has been
found that a surface of considerable area is required at the rear of the
machine to support it, hence, the discrepancy in size. Although the two
supporting surfaces differ in size, they are made in exactly the same
manner, each consisting of a thin longitudinal piece of spruce _R_, to
which cross pieces of bamboo _Q_ are attached. In the smaller plane,
Fig. 7, all the cross pieces are of the same size. In the larger plane,
Fig. 6, the outer strips _S_ are somewhat shorter than the others. Their
length is 2 1/2 inches, whereas the length of the strips _Q_ is 3 1/2
inches. In order to allow for the more gradual tapering of the plane,
around the outer ends of the longitudinal strips _R_ and the ribs _Q_ a
strip of bamboo is tied. The frame, composed of the longitudinal strip
and cross strips, is then covered with bamboo paper, parchment paper, or
any other style light paper, which is glued in place.
[Illustration: Fig. 6. Details of Main Plane of Aeroplane Model]
[Illustration: Fig. 7. Details of Smaller Plane of Aeroplane Model]
The forward or smaller plane has a spread of 8 1/2 inches and a depth of
3 1/4 inches. The main plane has a spread of 20 inches and a depth of 3
1/2 inches at the widest portion. The author has made experiments which
lead him to believe that the tapering form given to the outer edge of
the plane improves both the stability and endurance of the machine.
The planes are slightly arched, although it will be found that flat
planes will also give good results. The rear edge of the main plane
should be placed 4 1/4 inches distant from the forward edge of the
propeller block _E₁_.
The front plane must have a slight angle of incidence, just how much
depends upon the weight of the machine, the manner in which it is made,
and various other factors. This angle of incidence is obtained by
resting the front portion of the plane on two small blocks N, Figs. 1
and 2, which are fastened to the top of the main strip _A_ by strong
thread and glue.
[Illustration: Fig. 8. Device for Winding up Rubber-Band Motors]
The height of the blocks N should be about 1/4 inch, although this will
necessarily vary with the machine. The blocks should be placed
approximately 4 inches from the forward end of the machine. The front
end of the forward plane should be elevated about 1/4 inch above the
rear end, which rests directly on the main strips.
Both the front and rear planes _L_ and _P_ are removably lashed to the
frame by means of ordinary rubber bands, which may be obtained at any
stationery store. These rubber bands are lettered _M_ in Fig. 1.
_Winding the Rubber Strips_. The rubber strips can be most conveniently
wound up by means of an egg beater, slightly changed for the purpose.
Fig. 8. The beater and the frame in which it is carried are entirely
removed, leaving only the main rod _E_, which is cut off at the lower
end so that the total length is not more than 2 or 3 inches. The two
brass strips _D_ on either side of the rod, which are attached to the
pinion _Q_ meshing with the large driving wheel _H_, are likewise
retained. A washer _F_ is soldered to the rod near its upper end, so as
to limit the motion of the small pinion and the brass strips _D_
attached to the pinion. Next a wire _B_ is bent in the form of a loop,
through which loop the central rod passes. The ends of the wire are
soldered to the side strips _D_. Lastly, a piece of wire _C_ is bent and
soldered to the lower ends of the side strips. In order to wind up a
rubber strip, the strip is detached from the forward end of the model,
and the hook _A_ slipped over the wire _C_. The opposite end of the
rubber band is held in any convenient manner. Naturally the two strips
must be wound in opposite directions, so that the two propellers will
turn in opposite directions. By stretching the rubber while it is being
wound, more revolutions can be obtained. It is not safe to have the
propeller revolve more than 700 times. The ratio of the gears of the
egg-beater winder can be figured out so that the requisite number of
twists can be given to the rubber bands for that particular number of
revolutions.
_Model with Gasoline Motor_. The next and somewhat more ambitious stage
is the building of a power-driven model, which has been made possible by
the manufacture of miniature gasoline motors and propellers for this
purpose. Motors of this kind, weighing but a few pounds and capable of
developing 1/4 horse-power or more, may be had complete with an 18-inch
aluminum propeller and accessories for about $45. As is the case with
the rubber-band driven model, the monoplane is the simplest type to
construct, and the dimensions and details of an aeroplane of this type
are given here. It will be found that a liberal-sized machine is
required to support even such a small motor. The planes, Fig. 9, have a
spread of 7 feet 8 inches from tip to tip, each wing measuring 3 1/2
feet by a chord of 15 inches. They are supported on a front and rear
wing spar of spruce, 1/2 by 3/8 inch in section, while the ribs in both
the main plane and the rear stabilizing plane measure 1/8 by 1/2 inch in
cross section. There are eight of these spruce ribs in the main plane,
and they are separately heated and curved over a Bunsen burner, or over
a gas stove, which is the same tiling. They are then nailed to the wing
spars 6 inches apart. The main spars of the fuselage are 7 feet long and
they are made of 1/2 by 3/8 inch spruce, the struts being placed 1 1/2
feet apart, measuring from the rear, with several intermediate struts to
brace the engine bed. Instead of using strut sockets for the fuselage,
which would increase the cost of construction unnecessarily, a simple
combination of a three-way wire fastener and a wire nail may be resorted
to. The shape of these fasteners is shown at _A_ in Fig. 9. They may be
cut out of old cracker boxes or tin cans (sheet iron) with a pair of
shears, the holes in the ends being made either with a small drill or by
driving a wire nail through the metal placed on a board, and filing the
burrs off smooth. A central hole must also be made for the 1 1/2 inch
wire nail which is driven through the main spar and the fastener then
slipped over it. As indicated, this nail also serves to hold the strut.
A drop of solder will serve to attach the fastener to the nail. The
front of the fuselage is 9 inches square, tapering down to 6 inches at
the rear. The height of the camber of the main planes is 1 1/2 inches
and the angle of incidence is 7 degrees, measured with relation to the
fuselage. The non-lifting tail plane at the rear which is to give the
machine longitudinal stability, measures 4 feet in span by 14 inches in
depth.
[Illustration: Fig. 9. Details of Power-Driven Aeroplane Model]
The running gear or front landing frame is made of 1/2 inch square
spruce, all joints being made with 1/16 by 1 inch bolts. Aluminum
sleeves, procurable at an aeronautic supply house, are employed for the
attachment of the rubber springs and the radius rods running down to the
wheels, which may also be purchased ready to install. Old bicycle wheels
will serve the purpose admirably. Light steel tubes 1/2 inch in diameter
are used to run these aluminum sleeves on. Two other steel tubes are
joined to the lower corner of the frame by flattening them at the ends
and drilling with a small hole for a nail. These are run diagonally up
to the fuselage and serve as buffers to take the shocks of landing. For
bracing the wings, two similar tubes are fastened to form a pyramid on
top of the main plane just back of the engine. From these, guys are run
to the wings as shown. The engine bed is made of 1/2 by 3/4-inch white
pine, and to make it solid it is carried as far back as the rear edge of
the main plane. The batteries and coil are directly attached to this
plane, care being taken in their placing to preserve the balance of the
machine. The rudder measures 14 inches square and is made of 3/8-inch
square spruce, reinforced with tin at the joints, as it is necessary to
make the frame perfectly rigid. Both sides are covered with fabric. In
this case a 1-horse-power motor furnishes the necessary energy and it is
fitted with an 18-inch aluminum propeller which it is capable of turning
at 2,400 r.p.m. The carbureter and gas tank are made integral, and the
gasoline and oil are both placed in this tank in the proportion of about
four parts to one, in order to save the weight of an extra tank for oil.
Flights of half a mile are possible with this model in calm weather, but
a great deal of measuring and testing of the fuel is necessary in order
to regulate the flight, and "grass-cutting" should be practiced by the
builder in order to properly regulate the machine. Trials have shown
that the flat non-lifting tail on the fuselage gives excellent
longitudinal stability, the machine rising nicely and making its descent
very easy angle, so that it is seldom damaged by violent collisions in
landing.
BUILDING A GLIDER
The building of hand- or power-driven models does not suffice to give
that personal experience that most students are desirous of obtaining.
The best method of securing this is to build a glider and practice with
it. Any flying machine without a motor is a glider and the latter is the
basis of the successful aeroplane. In the building of an aeroplane the
first thing constructed is the glider, _i.e._ the frame, main planes,
stabilizing planes, elevators, rudders, etc. It is only by the
installation of motive power that it becomes a flying machine. The
biplane will be found the most satisfactory type of glider as it is more
compact and therefore more easily handled, which is of great importance
for practicing in a wind. The generally accepted rule is that 152 square
feet of surface will sustain the weight of the average man, about 170
pounds, and it will be apparent that the length of the glider will have
to be greater if this surface is to be in the form of a single plane
than if the same amount is obtained by incorporating it in two
planes—the biplane. A glider with a span of 20 feet and a chord of 4
feet will have a surface of 152 square feet. So far as learning to
balance and guide the machine are concerned, this may be mastered more
readily in a small glider than in a large one, so that there is no
advantage in exceeding these dimensions—in fact, rather the reverse, as
the larger construction would be correspondingly more difficult to
handle. The materials necessary consist of a supply of spruce, linen
shoe thread, metal sockets, piano wire, turnbuckles, glue, and
closely-woven, light cotton fabric for the covering of the planes.
*Main Frame*. The main frame or box cell is made of four horizontal
beams of spruce 20 feet long and 1 1/2 by 3/4 inch in section. They must
be straight-grained and perfectly free from knots or other defects. If
it be impossible to obtain single pieces of this length, they may be
either spliced or the glider may be built in three sections, consisting
of a central section 8 feet long, and two end sections each 6 feet in
length, this form of construction also making the glider much easier to
dismantle and stow in a small space. In this case, the ends of the beams
of each end section are made to project beyond the fabric for 10 inches
and are slipped into tubes bolted to corresponding projections of the
central section. These tubes are drilled with three holes each and bolts
are passed through these holes and corresponding holes in the projecting
ends after they have been fitted into the tubes, and drawn up tightly
with two nuts on each bolt to prevent shaking loose. Ordinary 3/16-inch
stove bolts will serve very nicely for this purpose. The upper and lower
planes forming the box cell, are held apart by 12 struts, 4 feet long by
7/8 inch diameter, preferably of rounded or oval form with the small
edge forward to minimize the head resistance. It is only necessary to
space these equally, starting from both ends; this will bring the
splices of the demountable sections in the center of the square on
either side of the central section. The main ribs are 3 feet long by 1
1/4- by 1/2-inch section and their placing should coincide with the
position of the struts. Between these main ribs are placed 41 small
ribs, equally spaced and consisting of pieces 4 feet long by 1/2 inch
square. These, as well as all the other pieces, should have the sharp
edges of the square rounded off with sand paper. The ribs should have a
camber of 2 inches in their length and the simplest method of giving
them this is to take a piece of plank, draw the desired curve on it, and
then nail blocks on both sides of this curve, forming a simple mould.
The rib pieces should then be steamed, bent into this mould, and allowed
to dry, when they will be found to have permanently assumed the desired
curvature. Meanwhile, all the other pieces may be shellaced and allowed
to dry.
[Illustration: Fig 10. Wrong and Right way of Making a Wire Joint]
_Assembling the Planes_. To assemble the glider, the beams are laid out
on a floor, spaced the exact distance apart, _i.e._, 3 feet, and exactly
parallel—in the demountable plan, each section is assembled
independently. The main ribs are then glued in place and allowed to set,
after which they are strongly bound in place with the linen thread, and
the various layers of thread given a coating of hot glue as they are put
on. This method is not arbitrary, but it is simple and gives the
lightest form of construction. If desired, tie-plates, clamps, or any
other light method of fastening may be employed. This also applies to
the ribs. They are assembled by placing them flush with the front beam
and allowing them to extend back a foot beyond the rear beam, arched
side up in every case. They may be glued and bound with thread, held by
clamps, or nailed or screwed into place, care being taken to first start
a hole in the beam with an awl and to dip the nails in soft soap to
prevent splitting the wood. Twenty-one ribs, spaced one foot apart, are
used in the upper plane, and 20 in the lower, owing to the space left
for the operator in the latter. For fastening the two planes together,
whether as a whole or in sectional units, 24 aluminum sockets will be
required. These may be purchased either ready to fit, or an effective
substitute made by sawing short lengths of steel tubing, slitting them
with the hack saw an inch from the bottom, and then flattening out and
drilling the right-angle flanges thus formed to take screws for
attaching the sockets to the beams. In case these sockets are bought,
they will be provided with eye bolts for the guy wires; if homemade,
they may have extra holes drilled in the edges of the flanges for this
purpose or some simple wire fastener such as that described in
connection with the power-driven model may be used, heavier metal,
however, being employed to make them. The sockets should all be screwed
to the beams at the proper points and then the struts should be forced
into them. The next move is to "tie" the frame together with guy wires.
No. 12 piano wire being employed for this purpose. Each rectangle is
trussed by running diagonal guy wires from each corner to its opposite.
To pull these wires taut, a turnbuckle should be inserted in each and
after the wire has been pulled as tightly as possible by hand, it should
be wound upon itself to make a good strong joint, as shown at _B_, Fig.
6. A fastening as shown at _A_ will pull out under comparatively little
strain and is not safe. As is the case with most of the other fittings,
these turnbuckles may be bought or made at home, the simple bicycle type
of turnbuckle mentioned in connection with "Building a Curtiss," being
admirably adapted to this purpose. In fact, the construction of the
latter will be found to cover the requirements of the glider, except
that the ribs are simpler and lighter, as already described, and no
provision for the engine or similar details is necessary. All the guy
wires must be tightened until they are rigid, and the proper degree of
tension for them may be simply determined in the following manner:
After the entire frame is wired, place each end of it on a saw horse so
as to lift it two or three feet clear of the floor. Stand in the opening
of the central section, as if about to take a glide, and by grasping the
forward central struts, raise yourself from the floor so as to bring
your entire weight upon them. If properly put together the frame will be
rigid and unyielding, but should it sag even slightly, the guy wires
must be uniformly tightened until even the faintest perceptible tendency
to give under the weight is overcome.
_Stretching the Fabric_. The method of attaching the fabric will be
determined by whether the glider is to be one piece or sectional, and
the expense for this important item of material may be as little or as
much as the builder wishes to make it. Some employ rubberized silk,
others special aeronautic fabrics, but for the purposes of the amateur,
ordinary muslin of good quality, treated with a coat of light varnish
after it is in place, will be found to serve all purposes. The cloth
should be cut into 4-foot strips, glued to the front horizontal beams,
stretched back tightly, and tacked to both the rear horizontal beams and
to the ribs. Tacks should also supplement the glue on the forward beams
and the upholstery style should be used to prevent tearing through the
cloth. In case the glider is built in sections, the abutting edges of
the cloth will have to be reinforced by turning it over and stitching
down a strip one inch wide, and it will make this edge stronger if an
extra strip of loose fabric be inserted under the turn before sewing it
down. Eyelets must then be made along these edges and the different
sections tightly laced together when assembling the glider. It is also
desirable to place a strip of cloth or light felt along the beams under
the tacks to prevent the cloth from tearing out under the pressure.
To form a more comfortable support for the operator, two arm pieces of
spruce, 3 feet by 1 inch by 1 3/4 inches, should be bolted to the front
and rear beams about 14 inches apart over the central opening left in
the lower plane. These will be more convenient than holding on to the
struts for support, as it will not be necessary to spread the arms so
much and there will be more freedom for manipulating the weight to
control the glider in flight. In using the struts, it is customary to
grasp them with the hands, while with the arm pieces, as the name
implies, the operator places his arms over them, one of the strips
coming under each armpit. After the fabric has been given a coat of
varnish on the upper side and allowed to dry, the glider is ready for
use. The cost of the material should be about $30 to $40, depending upon
the extent to which the builder has relied upon his own ingenuity in
fashioning the necessary fittings—in any case, it will be less than the
amount required for the purchase of the engine alone for a power-driven
model.
*Glider with Rudder and Elevator*. It will be noted that this is the
simplest possible form of glider in that it is not even provided with a
rudder, but for the beginning of his gliding education the novice will
not require this, as first attempts should be confined to glides over
level ground in moderate, steady wind currents and at a modest
elevation. Some of the best gliding flights made by Herring, Chanute’s
co-worker, were in a rudderless glider. After having mastered the
rudiments of the art, the student may go as far as the dictates of his
ambition impel him in the direction of improvements in his glider, by
adding a rudder, elevator, and warping control. In fact, it is not
necessary to confine himself to the simple design of glider here
outlined at all. He may take either the Wright or Curtiss machines as a
model and build a complete glider, following the dimensions and general
methods of construction here given, though these may also be improved
upon by the man handy with tools, bearing in mind that the object to be
achieved is the minimum weight consistent with the maximum strength.
*Learning to Glide*. The first trials should be made on level ground and
the would-be aviator should be assisted by two companions to help him in
getting under way. The operator takes a position in the center
rectangle, back far enough to tilt up slightly the forward edges of the
planes. A start and run forward is made at a moderate pace, the keepers
carrying the weight of the glider and overcoming its head resistance by
running forward at the same speed. As the glider cuts into the air, the
wind caused by running will catch under the uplifted edges of the curved
planes and will buoy it up, causing it to rise in the air taking the
operator with it. This rise will be probably only sufficient to lift him
clear of the ground a foot or two. Now he projects his legs slightly
forward so as to shift the center of gravity a trifle and bring the
edges of the glider on an exact level, parallel with the ground. This,
with the momentum acquired at the start, will keep the glider moving
forward for some distance. When the weight of the operator is slightly
back of the center of gravity, the leading edges of the planes are
tilted up somewhat, increasing the angle of incidence and in consequence
the pressure under the planes, causing the glider to rise, and if the
glide is being made into a wind, as should always be the case, quite a
height may be reached as the result of this energy. Once it ceases, the
tendency to a forward and upward movement is lost, and it is to prolong
this as much as possible that the operator shifts the center of gravity
to bring the machine on an even keel, or where at a little height,
slightly below this, giving it a negative angle of incidence, which
permits him to coast down the air until sufficient speed is acquired to
reverse the angle of incidence and again rise so as to provide a "hill"
for another coast, thus prolonging the flight considerably. To put it in
the simplest language, when the operator moves backward, shifting the
center of gravity to the rear, the planes are tilted so that they catch
or "scoop up" the advancing air and rise upon it, whereas when he moves
forward and the planes tilt downward, this air is "spilled" out behind
and no longer acts as a support, and the glider coasts, either until the
ground is reached or enough momentum is gained to again mount upon the
wind. A comparatively few flights will suffice to make the student
proficient in the control of his apparatus by his body movements, not
only as concerns the elevating and depressing of the planes to ascend or
descend, corresponding to the use of the elevator on a power machine,
but also actual steering, which is accomplished by lateral movement to
the left or right.
Stable equilibrium is one of the chief essentials to successful flight
and this can not be maintained in an uncertain, gusty wind, especially
by the novice. The beginner should certainly not attempt a glide unless
the conditions are right. These are a clear, level space without
obstructions such as trees, and a steady wind not exceeding 12 miles per
hour. When a reasonable amount of proficiency has been attained in the
handling of the glider over level ground, the field of practice may be
changed to some gentle slope. In starting from this, it will be found
easier to keep the glider afloat, but the experience at first will prove
startling to the amateur, for as the glider sails away from the top of
the slope, the distance between him and the ground increases so rapidly
that he will imagine himself at a tremendous height, but by preserving
the balance and otherwise manipulating his weight in the manner taught
by the practice over the level, a nice flight of much greater distance
will be made and the machine will gradually settle down to the ground
much farther away from the starting place than was possible in the
earlier trials, this being one of the great advantages of starting from
an elevation. There is nothing that will fit the beginner so well for
the actual handling of a power machine as a thorough course of gliding
flights, and it is recommended that those who build gliders become
proficient in their use before attempting to pilot an aeroplane, whether
of their own make or not.
A further step in advance is the actual building of a full-fledged power
machine, and for those who desire a simple and comparatively inexpensive
type, requiring very little work that can not be performed in the home
workshop, a description of the construction of a Curtiss biplane is
given, while for those who are more ambitious and also have greater
financial resources, the details of the building of a Bleriot monoplane
are given.
BUILDING A CURTISS BIPLANE
Cost. First of all, the prospective builder will want to know the cost.
The best answer to this is that the machine will cost all its builder
can afford to spend upon it and probably a little more, as the man to
whom the expense is not of vital consideration will doubtless not
undertake its construction. Speaking generally, and there can be nothing
very definite about it, in view of the great difference in the
conditions, an expenditure of three to four hundred dollars will cover
the complete outlay for everything but the motor. If the builder has the
time and facilities for doing all the work himself, this amount may be
reduced very materially. On the other hand, if he finds it necessary to
purchase most of the material in form ready to assemble, it may exceed
this. But it will be a great aid to many to know that there is
practically nothing about the modern aeroplane which can not be found in
stock at one of the aeronautic supply houses. This makes it possible for
many to undertake the construction of a machine to whom it would not be
feasible, or at least not an attractive project in view of the time
involved, were it necessary to make every part at home. So far as
becoming involved in any legal difficulties is concerned owing to
existing patents, the student need not worry himself about this in
attempting the construction of a Curtiss biplane, so long as he
restricts the use of his machine to experimental purposes and does not
try to compete with the patentees in their own field—that of exhibiting
and selling machines.
[Illustration: Fig 11. Detailed Front View of Curtiss Biplane]
*General Specifications*. Just how long it will take to complete such a
machine will depend very largely upon the skill of the builder and the
extent of his resources for, as already mentioned, the expense may be
cut down by making all the necessary parts at home, but it will
naturally be at the sacrifice of a great deal of time. For instance, the
oval struts and beams may be bought already shaped from the local
planing mill, or they may be shaved down from the rough by hand.
Turnbuckles can be made from bicycle spokes and nipples and strips of
sheet steel, or they can be bought at 12 to 15 cents each. As a hundred
or more of them are needed, their cost is quite a substantial item.
[Illustration: Fig 12. Plan and Side Elevation of Curtiss Biplane]
Aeroplane construction doubtless impresses the average observer as being
something shrouded in considerable mystery—something about which there
is no little secrecy. Quite the contrary is the case in reality. Any man
who is fairly proficient as a carpenter and knows how to use the more
common machinist’s tools, such as taps and dies, drills, hacksaw, and
the like, will find no difficulty in constructing the machine of which
the details are given here. Having completed its building, he will have
to draw upon his capital to supply the motor. One capable of developing
25 to 30 horse-power at 1,000 to 1,200 r.p.m. will give the machine
considerable speed, as it will be recalled that Curtiss made a number of
his first flights with a 25-horse-power motor. As to the weight, the
lighter the better, but 400 pounds for the complete power plant will not
be excessive. The machine can sustain itself in the air with less power
than that mentioned, but with a heavy, low-power motor it will be
sluggish in action. This is an advantage for the amateur, rather than
otherwise, as it will provide him with an aeroplane that will not be apt
to get away from him during his first trials, thus making it safer to
learn on.
[Illustration: Fig 13. Details of Main and Small Ribs, Curtiss Biplane]
The Curtiss biplane has a spread of 30 feet, the main planes or wings
being divided into sections of a length equal to the distance between
struts, Figs. 11 and 12. There are five of these sections, each
measuring six feet. The struts can be taken out and the sections laid
flat on each other for storage. The framework for the front and rear
rudders can also be jointed, if desired, making it possible to store the
machine in small compass. The longest parts of the machine, when taken
apart, are the two diagonal beams running from the front wheel back to
the engine bed, and the skid. The horizontal front rudder is packed
intact. The vertical rear rudder is unhung and laid flat on the tail.
Two men can take the machine apart in a few hours, and can reassemble it
in a day. Whether these particular features of construction are covered
by patents can not be said, as Curtiss has declined to commit himself
regarding any rights he may have to them.
_Ribs_. Two distinct types of ribs are used, main ribs and small ribs,
both of the same curvature, Fig. 13. The main ribs are used between
pairs of struts, to hold apart the front and rear beams; they are heavy
enough to be quite rigid. Three to four small ribs are laid across each
section of the planes, between the pairs of main ribs, to give the cloth
the proper curvature, and to maintain it in the form desired. The main
ribs are built up of six 1/4-inch laminations of wood 7/8 inch wide and
securely glued together. The small ribs are made of three layers 1/2
inch wide.
The first part of the actual construction will be the making of these
laminated ribs, but before describing this detail, the question of
suitable material should be well considered. Both weight and strength
must be figured on and this limits the choice to a few kinds of wood. Of
these _spruce_ and _elm_ are the best available, with the occasional use
of _ash_ to give greater rigidity. Spruce is, of course, the first
choice. This wood was once considered as having no great strength, but a
series of careful tests shows this belief to be unfounded. With the
exception of the bed, or support for the motor and a few other parts,
the Wright machines are constructed wholly of spruce.
Table I gives results of tests made with spruce from Washington and
Oregon, and with elm from Michigan and Indiana. Testing scales were
employed, the pieces being supported at their ends with the load in the
center.
These tests were made with clear wood in each case, as knots naturally
decrease the strength of a piece greatly, this depending on their size
and location.
[Illustration: Fig. 14. Details of Rib Press, Curtiss Biplane]
Before proceeding with the ribs themselves, the press for giving them
the proper curvature must be made. Take a good piece of oak, ash, or
other solid wood, 8 inches wide by 5 feet long, and dressed all over. On
the side of the piece lay out the curve, the dimensions of which are
illustrated in Fig. 14. First, rule the horizontal, or chord line, on
it, marking off 4 feet 6 inches on this line, equidistant from each end.
Then divide the chord into 6-inch sections and, at the point of each
6-inch section, erect perpendiculars beginning at the rear, 3/4 inch, 1
3/8 inches, 2 inches, and so on, as indicated on the drawing. The upper
ends of these perpendiculars will form locating points for the curve.
Through them draw a smooth curve as shown, continuing it down through
the chord at each end. Take the piece with the curve thus marked on it
to the local planing, sash and blind, or sawmill—any plant equipped with
a band saw—and have it cut apart along the curve. This will cost little
or nothing—acquaintance will obtain it as a favor, and acquaintance with
any wood-working concern in the aeroplane builder’s home town will be of
great aid. Failing this aid, the operation may be carried out with a
hand saw (rip), but the job will not be as neat and will have to be
cleaned up with a draw knife and sand paper, taking care to preserve the
outline of the curve as drawn. As the rib press is really a mould or
pattern from which all the ribs are to be bent to a uniform curvature,
care must be taken in its construction.
To clamp the two halves of the press together, a dozen machine bolts
will be required; they should measure 3/4 X 15 inches. If obtainable,
eye bolts will be found more convenient as they may be turned up with
but one wrench and a bar. The steel straps are 3/8 by 1 1/2 by 10 inches
long with 3/4-inch holes drilled 9 inches apart to centers, to enclose
the 8-inch pieces.
Obtain a sufficient supply of boards of reasonably clear spruce, 1/4
inch thick, 6 to 7 inches wide, and at least 4 feet 9 inches long
(dressed both sides), to make all the ribs necessary both small and
large. This material should be purchased from the mill as it is out of
the question to attempt to cut the ribs from larger sizes by hand. Buy
several pounds of good cabinet makers’ glue and a water-jacketed
gluepot. This glue comes in sheets and in numerous grades—a good quality
should be used, costing from 40 to 50 cents a pound if bought in a large
city. Laminating the ribs in this manner and gluing them together is not
only the quickest and easiest method of giving them the proper curve,
being much superior to steam bending, but is also stronger when well
done, as the quality of the material can be watched more closely.
Start with the making of the small ribs; apply the glue thin and piping
hot in a generous layer to three boards with a good-sized flat paint or
varnish brush. Omit on the upper surface of third board and apply
between three others, Fig. 13. This will give two series of three each
in the press. Tighten up the end bolts first, as the upper part of the
press near the top of the curve is likely to be weak unless liberally
proportioned. Then turn down the nuts on the other bolts. Do not attempt
to turn any one of them as far as it will go the first time, but tighten
each one a little at a time, thus gradually making the compression over
the whole surface as nearly uniform as possible. This should be
continued until the glue will no longer ooze out from between the
boards, indicating that they are in close contact. Twenty-four hours
should be allowed for drying, and when taken out the cracks between the
boards should be almost invisible in the finished ribs.
Have the laminated boards cut by a power rip saw at the planing mill, to
the dimensions shown in the drawing, making an allowance of 1/4 inch for
the width of the saw blade at each cut in calculating the number of ribs
which can be cut from each board. In addition, a margin should be
allowed at each side, as it is impractical to get all the thin boards
squarely in line. For the main ribs, apply the glue between all six
boards, clamp and dry in the same manner. Thirty small ribs will be
required, if three are used in each section, and forty if four are
specified, while twelve main ribs will be needed for standard
construction, and sixteen if the quick-demountable plan referred to is
followed. It is advisable to make several extra ribs of each kind in
addition. If the builder has not sufficient faith in spruce alone,
despite the figures given in Table I, one of the laminations, preferably
the center, or if two be employed, the outer ones, may be of ash, though
this will add considerably to the weight.
To prevent the ribs from splitting open at the ends, they are protected
by light steel ferrules, shown in Fig. 15. When received in the
rough-sawed condition from the mill, the ribs must be tapered at the
ends with a plane or spoke shave to fit these ferrules, and the sharp
edges should be rounded off. In doing this, it must be remembered that
the upper surface of the small ribs gives the curvature to the cloth
surface, so that any tapering must be done on the lower side. The main
ribs may be tapered from both sides, as it is the center line, or crack
between the third and fourth laminations, that determines the curve.
Every inch along this line A-inch holes are to be drilled for the
lacing, Fig. 15.
The ferrules for the front ends of the small ribs are light 1/2-inch
seamless steel tubing; they may be flattened to the proper shape in a
vise without heating and are drilled with a 1/8-inch hole. They are
driven tight on to the tapered ends of the ribs and fastened in place
with a small screw. The rear-end ferrules are 1/2-inch lengths of
3/8-inch tubing, driven on and drilled with a 1/32-inch hole for the
rear-edge wire. The rear ferrules of the main ribs may be the same
1/2-inch tubing used for the front of the small ribs; they should be cut
off so that their ends will come in the same line as the holes in the
ends of the small ribs. If the quick-demountable plan be followed, the
second main rib from each end may be left long and drilled with a hole
like the small ribs. The front ferrules of the main ribs should be
3/4-inch tubing of heavier gauge, drilled with a 1/4-inch hole. The
finished ribs are sandpapered smooth and shellaced or coated with spar
varnish. The latter is much more expensive and slower in drying but has
the great advantage of being weather-proof and will protect the glue
cracks from moisture. The ferrules may be painted with black enamel.
[Illustration: Fig. 15. Details of Ribs and Struts, Curtiss Biplane]
_Struts_. Before going into the detail of the construction of the
remainder of the _main cell_ and its attached framing, a brief
description of its parts and their relation to one another will make
matters clearer. The upright struts, Fig. 15, which hold the two planes
apart, fit at each end into sockets, which are simply metal cups with
bolts projecting through their ends. Fig. 16. Those at the bottom of the
front row of struts pass through the eyes of the turnbuckles and
connections for the wire trussing, then through the flattened ferrules
of the main ribs, and finally through the beam, all being clamped
together with a nut. Those at the top go through the turnbuckles first,
then through the beam, and finally the rib ferrule. The bolts at the
back row of struts must go through the full thickness of the main ribs,
and so must be longer. The drawings. Figs. 15 and 16, show the method of
attachment of both the main and the small ribs and illustrate a neat
method of attaching the turnbuckles—instead of being strung on the
socket bolt one after another, they are riveted to the corners of a
steel plate which alone is clamped under the socket.
[Illustration: Fig. 16. Details of Metal Parts of Curtiss Biplane]
_Beams_. The beams are jointed at each strut connection, the ends being
cut square and united by a sheet-steel sleeve, a pattern of which is
shown in Fig. 16, clamped on by two small bolts. The hole for the socket
bolt is drilled half in each of the two abutting beams. As it is very
difficult to obtain long pieces of wood sufficiently straight grained
and free from knots for the purpose, this jointed system considerably
cheapens the construction. Both beams and struts are of spruce, but to
give additional strength, the beams of the middle section may be ash.
Special aero cloth, rubberized fabrics, or light, closely-woven duck
(racing yacht sail cloth of fine quality, this being employed at first
by the Wright Brothers in their machines) forms the surfaces of the
wings. The front edge of each section of the surface is tacked to the
beam and the rear edge is laced over the rear wire already referred to,
this wire being stretched taut through the holes in the rear tips of the
ribs, both main and small. After the cloth is stretched tight, it is
tacked to the small ribs, a strip of tape being laid under the tack
heads to prevent the cloth from pulling away from under them. If the
aeroplane is intended to be taken apart very often, the standard design
as shown by the large drawings, Figs. 11 and 12, may be modified so as
to make it unnecessary to unlace the cloth each time. This is arranged
by regarding the two outer sections at each end of the plane as one, and
never separating them. Additional main ribs are then provided at the
inner ends of these sections, and are attached directly to the beams,
instead of being clamped under the strut sockets. In taking the machine
apart, the struts are pulled from the sockets, leaving the latter in
place. It will then be an advantage to shorten the main planes somewhat,
say 3 inches on each section, so that the outer double sections will
come under the "12-foot rule" of the Express Companies.
_Running Gear_. Three wheels are provided—one in front under the
outrigger and two under the main cell for starting and landing. Two
beams extend from the front wheel to the engine bed and serve to carry
the pilot’s seat, as will be seen from the elevator, Fig. 12. A third
beam runs back horizontally from the front wheel and on rough ground
acts as a skid. The rest of the running gear is made of steel tubing,
the pieces being joined simply by flattening the ends, drilling and
clamping with bolts; no sockets or special connections of any kind are
necessary here. If desired, the wheels may be carried in bicycle forks
and may be fitted with shock absorbers, some idea of the various
expedients adopted by different builders for this purpose being
obtainable from the sketches. Fig. 40 in "Types of Aeroplanes." Two
separate tubes, one on each side of the wheel make a simple construction
and will probably serve just as well. The details of the running gear
will be given later.
_Outrigging and Rudders_. For the outriggers and the frames carrying the
front horizontal or elevating rudder and the rear vertical rudder and
tail, or horizontal keel, either spruce or bamboo may be employed.
Bamboo will be found on machines turned out by the Curtiss factory, and
while it is the lighter of the two, it is not generally favored, as
spruce is easier to obtain in good quality and is far easier to work. At
their ends, these outriggers are fitted with ferrules of steel tubing,
flattened and drilled through. The outriggers are attached to the main
framework of the machine by slipping the ferrules over the socket bolts
of the middle section struts, above and below the beams. It is
preferable, however, to attach the rear outriggers to extra bolts
running through the beams, so that when the machine is to be housed the
tail and rudder can be unshipped and the triangular frames swung around
against the main frame, considerably reducing the space required.
The tail, horizontal and vertical rudders, and the ailerons are light
frames of wood, covered on both sides with the same kind of cloth as the
main planes or wings. These frames are braced with piano wire in such a
manner that no twisting strains can be put on them. The front horizontal
rudder, which is of biplane construction like the main cell, is built up
with struts in the same way. Instead of being fitted with sockets,
however, the struts are held by long screws run through the planes and
into their ends, passing through the eyes of the turnbuckles.
DETAILS OF CONSTRUCTION
*Main Planes and Struts*. It is preferable to begin with the
construction of the main planes and their struts and truss wires, the
ribs already described being the first step.
The main beams offer no special difficulties. They are ovals 1 1/4 by 1
5/8 inches, all 6 feet long except the eight end ones, which are 6 feet
2 inches. The beams of the central section should be of ash, or should
be thicker than the others. In the latter case, they must be tapered at
the ends so that the clamping sleeves will fit and the additional wood
must be all on the lower side, so that the rib will not be thrown out of
alignment. The spruce used for the other beams should be reasonably
clear and straight grained, but a small knot or two does not matter,
provided it does not come near the ends of the beam. The beams may be
cut to the oval shape by the sawmill or planed down by hand.
"Fish-shaped" or "stream-line" section, as it is more commonly termed,
is used for the struts, Fig. 15. It is questionable whether this makes
any material difference in the wind resistance, but it is common
practice to follow it in order to minimize this factor. It is more
important that the struts be larger at their centers than at the ends,
as this strengthens them considerably. At their ends the struts have
ferrules of the 1-inch brass or steel tubing, and fit into the sockets
which clamp the ribs and beams together. The material is spruce but the
four central struts which carry the engine bed should either be ash or
of larger size, say 1 1/4 by 3 inches.
_Care Necessary to Get Planes Parallel_. The front struts must be longer
than the rear ones by the thickness of a main rib at the point where the
rear strut bolt passes through it, less the thickness of the rib ferrule
through which the bolt of the front strut must pass. However, the first
distance is not really the actual thickness of the rib, but the distance
between the top of the rear beam and the bottom of the strut socket. In
the drawings the difference in length between the front and rear struts
is given as 2 inches, but it is preferable for the builder to leave the
rear struts rather long and then measure the actual distance when
assembling, cutting the struts to fit. The ends of the struts should
also be countersunk enough to clear the head of the socket bolt.
One of the items which the builder can not well escape buying in
finished form is the strut sockets. These are cup-shaped affairs of
pressed steel which sell at 20 cents each. Sixteen of them will be
required for the main frame, and a dozen more can advantageously be used
in the front and rear controls, though for this purpose they are not
absolutely necessary. They can also be obtained in a larger oval size
suitable for the four central struts that carry the engine bed, as well
as in the standard 1-inch size. The bolts which project through the
bottom of the sockets are ordinary 1/4-inch stove bolts, with their
heads brazed to the sockets.
For the rear struts, where the bolt must pass through the slanting main
rib, it is advisable to make angle washers to put under the socket and
also between the beam and rib. These washers are made by sawing up a
piece of heavy brass tubing, or a bar with a 1/4-inch hole drilled in
its center, the saw cuts being taken alternately at right angles and at
60 degrees to the axis of the tube.
The sleeves which clamp together the ends of the beams are made of sheet
steel of about 20 gauge. The steel is cut out on the pattern given in
the drawing, Fig. 16, and the 3/16-inch bolt holes drilled in the
flanges. The flanges are bent over by clamping the sheet in a vise along
the bending line and then beating down with a hammer. Then the sleeves
can be bent into shape around a stray end of the beam wood. The holes
for the strut socket bolts should not be drilled until ready to
assemble. Ordinarily, 3/16-inch stove bolts will do to clamp the flanges
together.
Having reached this stage, the amateur builder must now supply himself
with turnbuckles. As already mentioned, these may either be purchased or
made by hand. It is permissible to use either one or two turnbuckles on
each wire. One is really sufficient, but two—one at each end—add but
little weight and give greater leeway in making adjustments. As there
are about 115 wires in the machine which need turnbuckles, the number
required will be either 115 or 230, depending upon the plan which is
followed. Those of the turnbuckles to be used on the front and rear
controls and the ailerons, about one-fifth of the total number, may be
of lighter stock than those employed on wires which carry part of the
weight of the machine.
*Making Turnbuckles for the Truss Wires*. On the supposition that the
builder will make his own turnbuckles, a simple form is described here.
As will be seen from Fig. 16, the turnbuckles are simply bicycle spokes,
with the nipple caught in a loop of sheet steel and the end of the spoke
itself twisted into an eye to which the truss wire can be attached. The
sheet steel used should be 18 or 16 gauge, and may be cut to pattern
with a heavy pair of tin snips. The spokes should be 3/32 inch over the
threaded portion. The eye should be twisted up tight and brazed so that
it can not come apart. The hole in the middle of each strip is, of
course, drilled the same size as the spoke nipple. The holes in the ends
are 3/16 inch.
In the original Curtiss machines, the turnbuckles were strung on the
socket bolts one after another, sometimes making a pack of them half an
inch thick. A much neater construction is shown in the drawings, in
which the bolt pierces a single plate with lugs to which to make the
turnbuckles fast by riveting. The plates are of different shapes, with
two, three, or four lugs, according to the places where they are to be
used. They are cut from steel stock 3/32 inch thick, with 1/4-inch holes
for the socket bolts and 3/16 inch, or other convenient size, for the
rivets that fasten on the turnbuckles.
The relative merits of cable and piano wire for trussing have not been
thoroughly threshed out. Each has its advantages and disadvantages. Most
of the well-known builders use cable; yet if the difference between
1,000 feet of cable at 2 1/4 cents per foot (the price for 500-foot
spools), and 8 pounds of piano wire at 70 cents a pound, looks
considerable to the amateur builder, let him by all means use the wire.
The cable, if used, should be the 3/32-inch size, which will stand a
load of 800 pounds; piano wire should be 24 gauge, tested to 745 pounds.
It should be noted that there is a special series of gauges for piano
wire, known as the music wire gauge, in which the size of the wire
increases with the gauge numbers, instead of the contrary, as is usual
with machinery wire gauges.
One by no means unimportant advantage of the piano wire is that it is
much easier to fasten into the turnbuckles. A small sleeve or ferrule, a
1/4-inch length of 1/8-inch tubing, is first strung on the wire. The end
of the wire is then passed through the turnbuckle eye, bent up, thrust
through the sleeve, and again bent down. When the machine is taken
apart, the wire is not disconnected from the eye, but instead the
turnbuckle spoke is unscrewed from the nipple. The shape of the
sheet-steel loop should be such as to hold the latter in place. Cable,
on the other hand, must be cut with about 2 inches to spare. After being
threaded through the turnbuckle eye, the end is wound back tightly on
itself and then soldered, to make certain that it can not loosen.
With a supply of turnbuckles and cable or piano wire at hand, the
builder may go ahead with the main box-like structure or cell, which
should be completed except for the cloth covering, and in proper
alignment, before taking up the construction of the running gear and
controls.
*Running Gear*. The running gear of the machine is built of seamless
steel tubing, those parts which carry the weight of the machine direct
being of 3/4-inch outside diameter, 16-gauge tubing, while the others
are 5/8-inch outside diameter, either 18 or 20 gauge. About 25 feet of
the heavy and 45 feet of the light tubing will be required, in lengths
as follows: Heavy, four 3-foot, three 4-foot; light, one 6-foot, two
4-foot 6-inch, and seven 4-foot pieces. Referring to Fig. 17, two
diagonal braces from the rear beam to the engine bed, the V-shaped piece
under the front engine bed struts and all of the rear frame except the
horizontal piece from wheel to wheel, are of heavy tubing. The
horizontal in the rear frame, diagonals from the rear wheels and the
rear end of the skid to the front beam, the two horizontals between the
front and rear beam, and the forward V are of light tubing.
[Illustration: Fig. 17. Details of Curtiss Running Gear]
Three ash beams are used in the running gear. Two of these run
diagonally from the rear end of the engine bed to the front wheel. These
are about 10 feet long and 1 by 1 3/4 inches section. The third, which
on rough ground acts as a skid, is 8 1/2 feet long and about 2 inches
square. Between the joints where the tubing frames are attached to it,
the upper corners may be beveled off with a spoke shave an inch or more
down each side. The beams are attached to the front wheel with strips of
steel stock 1 1/2 inches wide and 1/8 inch thick. The engine bed beams
are also ash about 1 by 1 3/4 inches section. Their rear ends are bolted
to the middle of the rear engine bed struts and the front ends may be
1/2 inch higher.
[Illustration: SCENE AT AVIATION MEET AT ROUEN, FRANCE, SHOWING AN
ANTOINETTE MONOPLANE MAKING A TURN
_This Photograph Protected By International Copyright_]
[Illustration: A FRENCH MONOPLANE TRAVELLING SIXTY-FIVE MILES AN HOUR
_This Photograph Protected By International Copyright_]
The wheels are usually 20 by 2 inches, and of the bicycle type, but
heavier and wider in the hub; the tires are single tube. These wheels,
complete with tires, cost about $10 each. This size is used on the
standard Curtiss machines, but novice operators, whose landings are not
quite as gentle as they might be, find them easily broken. Therefore, it
may be more economical in the end to pay a little more and get heavier
tires—at least to start with.
For working the tubing into shape, a plumber’s blow torch is almost
indispensable—most automobilists will already possess one of these. The
oval, flat variety, holding about one pint, is very handy and packs away
easily, but on steady work requires filling somewhat too frequently.
With a dozen bricks a shield can be built in front of the torch to
protect the flame and concentrate the heat. Whenever it is to be
flattened and bent, the tubing should be brought to a bright red or
yellow heat. Screwing the vise down on it will then flatten it quickly
without hammer marks. Where the bend is to be made in the middle of the
piece, however, it may be necessary to resort to the hammer and anvil.
It is convenient to start with the framework under the rear beam. This
may be drawn accurately to full size on the workshop floor, and the
tubes bent to fit the drawing. With this framework once in place, a
definite starting point for the remainder of the running gear is
established. Here and in all other places, when boring through wood, the
holes should be drilled out full, and larger washers should be placed
under the bolt head and nut. All nuts should be provided with some sort
of locking device The perspective drawing. Fig. 17, should show the
general arrangement clearly enough to enable the builder to finish the
running gear.
*Outriggers*. Both the front and rear control members, or "outriggers"
as they are termed, Fig. 12, may be conveniently built up on the central
section of the main frame, which, it is assumed, has now been fitted
with the running gear.
The horizontal rudder, or "elevator," is a biplane structure like the
main cell of the machine, but with fewer struts; it is carried in front
of the main planes on two *A*-shaped frames. The vertical rudder, at the
rear, is split along the middle and straddles a fixed horizontal plane,
or _tail_. This also is carried on two *A*-shaped frames. Lateral
stability is controlled by two auxiliary planes or ailerons, one at each
side of the machine and carried on the two outer front struts. These
three control units—_elevator_, _tail_ and _rudder_, and _ailerons_—will
now be taken up separately and their construction, location on the
machine, and operation will be described.
[Illustration: Fig. 18. Details of Rudders and Ailerons, Curtiss
Biplane]
_Horizonal Rudder or Elevator_. The two planes of the elevator are 2
feet wide by 5 feet 8 inches long and are spaced 2 feet apart, being
held in this position by ten struts. The frames of the planes are built
of spruce sticks 1/2 by 1 inch, each plane having two sticks the full
length and five evenly spaced crosspieces or ribs. These are joined
together with squares of X-sheet tin, as shown in the detailed drawing,
Fig. 18. With a little experimenting, paper patterns can be made from
which the tin pieces can be cut out. The sticks are then nailed through
the tin with 3/4-inch brads.
It is convenient to draw the frames out accurately on a smooth wood
floor and then work over this drawing. The first few brads will hold the
sticks in place. When all the brads have been driven, a little drop of
solder should be run in around the head of each one. This is a tedious
job. One must be careful to use no more solder than necessary as it
increases the weight very rapidly. Two pounds of wire solder should be
sufficient for all the control members which are built in this way. When
the top side is soldered, pry the frame loose from the floor with a
screwdriver and turn it over. Then the projecting points of the brads
must be clinched and the soldering repeated.
At this stage, the two frames should be covered on both sides with the
prepared cloth used for covering the main planes. The method of
preparing this cloth is detailed a little farther along.
The struts, so-called, to continue the analogy with the main planes, are
turned sticks of spruce 3/8 inch in diameter. They are fitted at each
end with ferrules of thin 3/8-inch brass, or steel tubing, driven on
tight. Instead of using sockets, the struts are held at each end, simply
by a long wood screw driven through the tin and wood of the plane frame
and into the strut. These screws also hold the turnbuckles for the truss
wires. For trussing purposes, the elevator is regarded as consisting of
two sections only, the intermediate struts being disregarded.
The turnbuckles and wire used here and in the other control members may
well be of lighter stock than those used in the main planes. Piano wire,
No. 18, or 1/16-inch cable is amply strong. The sheet steel may be about
22 gauge, instead of 16, and the bicycle spokes smaller in proportion.
No turnbuckle plates are necessary. The screws running into the struts
may be passed directly through the eyes of the turnbuckles, where they
would have been attached to the turnbuckle plate. In order to secure a
square and neat structure, those struts which have turnbuckles at their
ends should be made a trifle shorter than the others.
At each end, the elevator has an *X*-shaped frame of 1/4-inch steel
tubing; at the intersection of the *X*’s are pivots on which the
elevator is supported. Each *X* is made of two tubes, bent into a y and
flattened and brazed together at the points. The ends of the *X*’s are
flattened and bent over so that the screws which hold the struts in
place may pass through them.
[Illustration: Fig. 19. Curtiss Biplane Ready for Flight]
To the front middle strut is attached an extension which acts as a lever
for operating the elevator. This is a stick of spruce 3/4 inch in
diameter and 3 feet 3 inches long. At its upper end it has a ferrule of
steel tubing, flattened at the end. The lower part of the stick may be
fastened to the strut by wrapping the tube with friction tape, or by
improvising a couple of sheet steel clamps. The upper end of the stick
is braced by a 1/4-inch steel tube, extending to the top of the rear
middle strut, and held by the same screw as the strut. This extension
lever is connected to the steering column by a bamboo rod, 1 inch in
diameter and about 10 feet long, provided with flattened ferrules of
steel tubing at each end. Each ferrule should be held on by a 1/8-inch
stove bolt passing through it.
_Front and Rear Outrigger Frames_. Both the front elevator and the tail
and rudder at the rear, are carried, as mentioned above, each on a pair
of *A*-shaped frames, similar to one another, except that those in the
rear are longer than those in the front. Both are made of spruce of
about the same section as used for the struts of the main frame. These
pieces may either be full length, or they may be jointed at the
intersection of the crosspieces, the ends being clamped in a sheet-steel
sleeve, just like that used on the beams of the main frame. In this
case, it is advisable to run a 1/8-inch stove bolt through each of the
ends.
[Illustration: Fig. 20. Details of Outriggers and Front Elevating Planes
as Seen from Driver’s Seat]
The crosspieces of the *A*-frames are spruce of the same section, or a
little smaller. At their ends may be used strut sockets like those of
the main frame; or, if it is desired to save this expense, they may be
fastened by strips of 1/16-inch steel stock with through bolts.
The front outrigger has, besides the two A-frames, a rather complicated
arrangement of struts designed to brace the front wheel against the
shocks of landing. This arrangement does not appear very plain in a plan
or elevation, and may best be understood by reference to the photograph,
Fig. 19, and the perspective drawing, Fig. 20. Fig. 20 is a view from
the driver’s seat. The elevator is seen in front, the *A*-frames at each
side, and at the bottom the two diagonal beams to the engine bed and the
skid.
Reference to this drawing will show the two diagonals run from the front
wheel up and back to the top of the main frame, and two more from the
wheel forward to the short crosspieces near the apexes of the *A*-frame:
there is also a vertical strut which intersects two horizontal pieces
running between the ends of the longer crosspieces of the *A*-frames.
Altogether, there are five attachments on each side of the front wheel,
through which the axle bolt must pass, viz, the connections to the skid,
to one of the diagonals to the engine bed, to one of the rear diagonals,
to one of the front diagonals, and to one side of the fork carrying the
vertical strut. Of these the skid attachments should be on the inside
closest to the wheel, and the engine bed diagonals next.
The four additional diagonals running to the front wheel may be spruce
of the same section used in the *A*-frames, or turned one inch round. At
each end they have flattened ferrules of steel tubing. The beams of the
*A*-frames have similar ferrules at the ends where they attach to the
main frames. These attachments should be made on the socket bolts of the
struts on either side of the middle 6-foot section and on the outer side
of the main beams—not between the beam and the socket itself.
It is possible, of course, to make all the *A*-frames and diagonal
braces of bamboo, if desired, the qualities of this material already
having been referred to. Bamboo rods for this purpose should be between
1 and 1 1/4 inches in diameter. Where ferrules are fitted on the ends,
the hole of the bamboo should be plugged with wood glued in place.
Generally, in the construction of the outrigger frames, the builder can
use his own discretion to a considerable extent. There tire innumerable
details which can be varied—far too many to consider even a part of the
possibilities in this connection. If the builder runs across any detail
which he does not see mentioned here, he may safely assume that any
workmanlike job will suffice. Often, the method may be adapted to the
materials on hand. The diagonal wires from the crosspieces of the
A-frames to the struts should be crossed.
_Rudder and Tail Construction_. The frame for the rudder and tail are
constructed in much the same way as those for the elevator, Fig. 18.
Spruce sticks 1 by 1/2 inch are used throughout, except for the piece at
the back edge of the rudder and the long middle piece across the tail;
these should be 1 1/2 by 1/2 inch. This long middle piece of the tail is
laid across on top of the rest of the framework. When the cloth is put
on, this makes the upper surface slightly convex while the lower surface
remains flat. The ends of this piece should be reinforced with sheet
steel, fairly heavy and drilled for 1/4-inch bolts, attaching the tail
to the *A*-frames.
The rudder is hung from two posts extending above and below the tail.
These posts may be set in cast aluminum sockets, such as may be obtained
from any supply house for 20 cents apiece. The posts need not be more
than 3/4 inch in diameter. At their outer ends, they should have
ferrules of steel tubing, and the turnbuckles or other attachments for
the truss wires should be attached by a wood screw running into the end
of each. From these posts the rudder may be hung on any light hinges the
builder may find convenient, or on hinges improvised from screw eyes or
eye bolts, with a bolt passing through the eyes of each.
In steering, the rudder is controlled by a steering wheel carried on a
hinged post in front of the pilot. This post should be ash about 1 by 1
1/4 inches. It hinges at the bottom on a steel tube of 1/2-inch diameter
which passes through it and is supported at the ends on diagonal beams
to the engine bed. Two diagonals of lighter tubing may be put in to hold
the posts centered between the two beams.
The post is, of course, upright, and the hub of the wheel is horizontal.
The wheel may be conveniently mounted on a piece of tubing of the same
size as the hub hole, run through the post and held by a comparatively
small bolt, which passes through it and has a big washer on either end.
The wheel is preferably of the motor-boat variety with a groove around
the rim for the steering cable.
The rear edge of the tail should be about 1 inch lower than the front.
To make the rudder post stand approximately vertical, wedge-shaped
pieces of wood may be set under the sockets.
The steering connections should be of flexible cables of steel such as
are made for this purpose. There should be a double pulley on the post
just under the wheel, and the cables should be led off the post just at
the hinge at the bottom, so that swinging the post will not affect them.
The cable is then carried under the lower main plane and out the lower
beams of the *A*-frames. It is attached to the rudder at the back edge;
snap hooks should be used for easy disconnection in packing. Perhaps the
best way of guiding the cable, instead of using pulleys, is to run it
through short pieces of tubing lashed to the beams with friction tape.
The tubing can be bent without flattening by first filling it with
melted lead, which, after the bending, can be melted out again.
*Ailerons for Lateral Stability*. The framework of the ailerons is made
in the same way as that for the elevator, tail, and rudder, Fig. 18. The
pieces around the edges should be 1 1/2 by 1/2 inch, as also the long
strip laid over the top of the ribs. The ribs should be 1/2 by 3/4 inch.
Each aileron has two holes, one for the strut to pass through, and the
other for the diagonal truss wires at their intersection. The back edge
also has a notch in it to clear the fore and aft wires. Each aileron is
hung on four strips of soft steel about 1/2 by 3/16 inch, twisted so
that one end is at right angles to the other. These are arranged one on
each side of the strut which passes through the aileron, and one at each
end. Bolts through the struts carry three of them and the outer one is
trussed by wires to each end of the outer strut.
A frame of 1/4-inch steel tubing fits around the aviator’s shoulders and
is hinged to the seat, so that he can move it by leaning from one side
to the other. This is connected by flexible cable to the rear edges of
the ailerons, so that when the aviator leans to the left, he will raise
the left and lower the right aileron. The upper edges of the ailerons
are directly connected to each other by a cable running along the upper
front beam, so that they must always move together.
*Covering of the Planes*. Mention has already been made of the fact, in
the general description of the machine, that light sail cloth, as
employed on the Wright machines, may be used for the planes or wings. As
a matter of fact, many different materials may be successfully employed,
the selection depending upon the builder himself and his financial
resources. About 55 square yards of material will be required, and in
comparing prices always compare the width as this may vary from 28 to 55
inches. Rubberized silk which is used on the standard Curtiss machines
is the most expensive covering, its cost running up to something like
two hundred dollars. There are also several good aero fabrics on the
market which sell at 60 cents a square yard, as well as a number of
brands of varnish for the cloth—most of them, however, quite expensive.
The most economical method is to employ a strong linen cloth coated with
shellac, which will be found very satisfactory.
The covering of the frames with the cloth may well be postponed until
after the engine has been installed and tested, thus avoiding the
splashing of oil and dirt which the fabric is apt to receive during this
operation. The wire to which the cloth is laced, must be strung along
the rear ends of the ribs of each plane. The wires pass through holes in
the ends of the small ribs and are attached to the main ribs with
turnbuckles. At the ends of the planes the main ribs must be braced
against the pull of the wire by a piece of 1/4-inch tubing running from
the end of the rib diagonally up to the rear beam. Both turnbuckles and
tube are fastened with one wood screw running into the end of the rib.
The cloth should be cut to fit the panels between the main ribs and
hemmed up, allowing at least an inch in each direction for stretch.
Small eyelets should be put along the sides and rear edges an inch apart
for the lacing. At the front edge, the cloth is tacked directly to the
beam, the edge being taken well under and around to the back. Strong
fish line is good material for the lacing.
After the cloth is laced on, it must be tacked down to the small ribs.
For this purpose, use upholstery tacks as they have big cup-shaped heads
which grip the cloth and do not tear out. As an extra precaution a strip
of heavy tape must be run over each rib under the tack heads. All the
control members are covered on both sides, the edges being folded under
and held by tacks.
*Making the Propeller*. If the completed biplane is to fly properly and
also have sufficient speed to make it safe, considerable care must be
devoted to the design and making of the propeller. Every aeroplane has a
safe speed, usually referred to in technical parlance as its _critical
speed_. In the case of the Curtiss biplane under consideration, this
speed is about 40 miles an hour. By speeding up the motor considerably,
it may be able to make 42 to 43 miles an hour in a calm, such a
condition representing the only true measure of an aeroplane’s ability
in this direction, while on the other hand, it would not be safe to let
its speed with relation to the wind (not to the ground) fall much below
35 miles an hour. At any slower rate of travel, its dynamic stability
would be precarious and the machine would be likely to dive to the
ground unexpectedly. The reasons for this have been explained more in
detail under the heading of "The Internal Work of the Wind."
The necessity of making the propeller need not discourage the ambitious
builder—if he can spare the time to do it right, it will be excellent
experience. If not, propellers designed for driving a machine of this
size can be purchased ready to mount from any one of quite a number of
manufacturers. But as the outlay required will be at least $50,
doubtless most experimenters will prefer to undertake this part of the
work as well as that of building the framework and main cell,
particularly as more than 90 per cent of the sum mentioned is
represented by labor. The cost of the material required is insignificant
by comparison.
_True-Screw Design_. First it will be necessary to design the propeller
to meet the requirements of the biplane itself. As this is a matter that
has already been gone into in considerable detail under the appropriate
heading, no further explanation of propeller characteristics or of the
technical terms employed, should be needed here. We will assume that the
biplane is to have a speed of 40 miles per hour in still air with the
motor running at 1,200 r.p.m. With this data, it will not be difficult
to calculate the correct pitch of the propeller to give that result.
Thus
40 X 5,280 X 100 / 60 X 1,200 X 85 = 3.45
or in round numbers a pitch of 3 1/2 feet. 40 (the speed in miles per
hour) times 5,280 (feet per mile) divided by 00 (minutes in an hour)
gives the speed of the aeroplane in feet per minute. Dividing this by
1,200 (revolutions per minute) gives the number of feet the aeroplane is
to advance per revolution of the propeller. The "100/85" part of the
equation represents the efficiency of the propeller which can safely be
figured on, _i.e._, 85 per cent, or an allowance for slip of 15 per
cent. Forty miles an hour is the maximum speed to be expected, while the
r.p.m. rate of the engine should be that at which it operates to the
best advantage.
The merits of the _true-screw_ and _variable-pitch_ propellers have
already been dwelt upon. The former is not only more simple to build,
but experience has shown that, as generally employed, it gives better
efficiency. Hence, the propeller under consideration will, be of the
true-screw type. Its pitch has already been calculated as 3 1/2 feet.
For a machine of this size and power, it should be 6 feet in diameter.
Having worked out the pitch and decided upon the diameter, the next and
most important thing is to calculate the pitch angle. It will be evident
that no two points on the blade will travel through the air at the same
speed. Obviously, a point near the tip of the propeller moves faster
than one near the hub, just as in rounding a curve, the outer wheel of
an automobile has to travel faster than the inner, because it has to
travel farther to cover the same ground. For instance, taking the
dimensions of the propeller in question it will be seen that its tips
will be traveling through the air at close to 4.3 miles per minute, that
is,
6 X π X 1200 / 5,280 = 4.28
in which 6, the diameter of the propeller in feet, times π gives the
circumference of the circle which is traveled by the blade tips 1,200
times per minute; this divided by the number of feet per mile gives the
miles per minute covered. On the other hand, a point on the blade but 6
inches from the hub will turn at only approximately 3,500 feet per
minute. Therefore, if every part of the blade is to advance through the
air equally, the inner part must be set at a greater angle than the
outer part. Each part of the blade must be set at such an angle that at
each revolution it will move forward through the air a distance equal to
the pitch. This is known as the pitch angle. The pitch divided by the
circumference of the circle described by any part of the blade, will
give a quantity known as the tangent of an angle for that particular
part. The angle corresponding to that tangent may most easily be found
by referring to a book of trigonometric tables.
For example, take that part of the blade of a 3 1/2-foot pitch propeller
which is 6 inches from the center of the hub. Then
3.5 X 12 / 6 X 2 π = 1.1141 tangent of 48 degrees 5 minutes
in which 3.5 X 12 reduces the pitch to inches, while 6 X 2π is the
circumference of the circle described by the point 6 inches from the
hub. However, in order to give the propeller blade a proper hold on the
air, it must be set at a greater angle than these figures would
indicate. That is, it must be given an angle of incidence similar to
that given to every one of the supporting planes of the machine. This
additional angle ranges from 2 degrees 30 minutes, to 4 degrees,
depending upon the speed at which the particular part of the blade
travels; the greater the speed, the less the angle. This does not apply
to that part of the blade near the hub as the latter is depended upon
solely for strength and is not expected to add to the effective thrust
of the propeller.
Table II shows the complete set of figures for a blade of 3 1/2-foot
pitch, the angles being worked out for sections of the blade 3 inches
apart.
These angles are employed in Fig. 21, which shows one blade of the
propeller and its cross sections.
It should be understood that these calculations apply only to the type
of propeller known as the _true screw_, as distinguished from the
_variable pitch_. The design of the latter is a matter of personal skill
and experience in its making which is hardly capable of expression in
any mathematical formula. There are said to be only about three men in
this country who know how to make a proper variable-pitch propeller, and
it naturally is without advantage when made otherwise.
[Illustration: Fig. 21. Details of Propeller Construction, Curtiss
Biplane]
_Shaping the Blades_. Like the ribs, the propeller is made up of a
number of laminations of boards finished true and securely glued,
afterward being cut to the proper shape, though this process, of course,
involves far more skill than in the former case. Spruce is the strongest
wood for its weight, but it is soft and cracks easily. Maple, on the
other hand, is tough and hard, so that it will be an advantage to
alternate the layers of these woods with an extra maple board, in order
to make both outside strips of the harder wood, so as to form a good
backing for the steel flanges at the hub, the rear layer extending the
full length of the thin rear edges of the blades. Other woods may be
employed and frequently are used by propeller manufacturers, such as
mahogany (not the grained wood used for furniture, but a cheaper grade
which is much stronger), walnut, alternate spruce and whitewood, and
others.
The boards should be selected with the greatest care so as to insure
their being perfectly clear, _i.e._, absolutely free of knots,
cross-grained streaks, or similar flaws, which would impair their
strength and render them difficult to work smoothly. They should measure
6 inches wide by 6 feet 1 inch in length. Their surfaces must be
finished perfectly true, so that they will come together uniformly all
over the area on which they bear on one another, and the various pieces
must be glued together with the most painstaking care. Have the glue
hot, so that it will spread evenly, and see that it is of a uniform
consistency, in order that it may be smoothly applied to every bit of
the surface. They must then be clamped together under as much pressure
as it is possible to apply to them with the means at hand, the rib press
already described in detail forming an excellent tool for this purpose.
Tighten up the nuts evenly a little at a time, avoiding the application
of excessive or uneven pressure at one point, continuing the gradual
tightening up process until it can not be carried any farther. This is
to prevent the boards from assuming a curve in drying fast. Allow at
least twenty-four hours for drying, during which period the laminated
block should be kept in a cool, dry place at as even a temperature as
possible.
Before undertaking the remainder of the work, all of which must be
carried out by hand, with the exception of cutting the block to the
outline of the propeller, which may be done with a band saw, a set of
templates or gauges should be made from the drawings. These will be
necessary as guides for finishing the propeller accurately. Draw the
sections out full size on sheets of cardboard or tin and cut out along
the curves, finally dividing each sheet into two parts, one for the
upper side and one for the lower. Care must be taken to get the sides of
the template square, and when they are used, the propeller should be
laid on a perfectly true and flat block. Each template should be marked
as it is finished, to indicate what part of the blade it is a gauge for.
The work of cutting the laminated block down to the lines represented by
the templates is carried out with the aid of the plane, spoke shave, and
gouge. After the first _roughing out_ to approximate the curvature of
the finished propeller is completed, the cuts taken should be very fine,
as it will be an easy matter to go too deep, thus spoiling the block and
necessitating a new start with fresh material. For finishing, pieces of
broken glass are employed to scrape the wood to a smooth surface,
followed by coarse and finally by fine sandpaper.
_Mounting_. The hub should be of the same diameter as the flange on the
engine crank shaft to which the flywheel was bolted, and should have its
bolt holes drilled to correspond. To strengthen the hub, light steel
plates of the same diameter are screwed to it, front and back, and the
bolt holes drilled right through the metal and wood. This method of
fastening is recommended where it is possible to substitute the
propeller for the flywheel formerly on the engine, it being common
practice to omit the use of the flywheel altogether. The writer does not
recommend this, however, as the advantages of smoother running and more
reliable operation gained by the use of a flywheel in addition to the
propeller far more than offset any disadvantage represented by its
weight. It will be noted that the Wright motors have always been
equipped with a flywheel of ample size and weight and this is
undoubtedly responsible, in some measure at least, for the fact that the
Wright biplanes fly with considerably less power than is ordinarily
employed for machines of the same size. If the motor selected be
equipped with an unusually heavy flywheel, and particularly where the
wheel is of comparatively small diameter, making it less effective as a
balancer, it may be replaced with one of lighter weight and larger
diameter. It may be possible to attach it by keying to the forward end
of the crank shaft, thus leaving the flange from which the flywheel was
taken free for mounting the propeller. An ordinary belt pulley will
serve excellently as the new flywheel, as most of its weight is centered
in its rim, but as the common cast-iron belt pulley of commerce is
seldom intended to run at any such speed as that of an automobile motor,
it should be examined carefully for flaws. Otherwise, there will be
danger of its blunting with disastrous results under the influence of
centrifugal force. Its diameter should not exceed 16 inches in order to
keep its peripheral speed within reasonable limits. Where the mounting
of the motor permits of its use, a wood pulley 18 to 20 inches in
diameter with a steel band about 1/8 to 1/4-inch thick, shrunk on its
periphery, may be employed. Most builders will ridicule the idea of a
flywheel other than the propeller itself. "You do not need it; so why
carry the extra weight?" will be their query. It is not absolutely
necessary, but it is an advantage.
In case the flywheel of the engine selected is keyed to the crank shaft,
or in case it is not possible to mount both the flywheel and the
propeller on different ends of the crank shaft, some other expedient
rather than that of bolting to the flange must be adopted. In such a
case, the original flywheel, where practical to retain it, may be
drilled and tapped and the propeller attached directly to it. Where the
flywheel can not be kept, it will usually be found practical to cut off
its rim and bolt the propeller either to the web or spokes, or to the
flywheel hub, if it be cut down to the latter.
The drawing. Fig. 21, shows the rear or concave side of the propeller.
From the viewpoint of a man standing in its wind and facing forward, it
turns to the left, or anti-clockwise. On many of the propellers now on
the market, the curved edge is designed to go first. This type may have
greater advantages over that described, but the straight front edge
propeller is easier for the amateur to make.
*Mounting the Engine*. Having completed the propeller, the next step is
the mounting of the engine. Reference to the types available to the
amateur aeroplane builder has already been made. There are a number of
motors now on the market that have been designed specially for this
purpose and not a few of them are of considerable merit. Their cost
ranges from about $250 up to $2,500, but it may be possible to pick up a
comparatively light-weight automobile motor second hand which will serve
all purposes and which will cost far less than the cheapest aeronautic
motor on the market. It must be capable of developing 30 actual
horse-power at 1,000 to 1,200 r.p.m. and must not exceed 400 pounds
complete with all accessories, such as the radiator and piping, magneto,
water, oil, etc. Considerable weight may be saved on an automobile motor
by removing the exhaust manifold and substituting a lighter flywheel for
the one originally on the engine—or omitting it altogether, as just
mentioned. A light-weight aeronautic radiator should be used in
preference to the usual automobile radiator.
When placing the engine in position on the ash beams forming its bed or
support, it must be borne in mind that the complete machine, with the
operator in the aviator’s seat, is designed to balance on a point about
1 1/2 feet back of the front edge of the main planes. As the operator
and the motor represent much the larger part of the total weight, the
balance may easily be regulated by moving them slightly forward or
backward, as may be required. It will be necessary, of course, to place
the engine far enough back in any case to permit the propeller blades to
clear the planes. The actual installation of the engine itself will be
an easy matter for anyone who has had any experience in either
automobile or marine gasoline motor work. It is designed to be bolted to
the two engine beams in the same manner as on the side members of the
frame of an automobile, or the engine bed in a boat. Just in front of
the engine is the best place for the gasoline tank, which should be
cylindrical with tapering ends, to cut down its wind resistance. If the
designer is not anxious to carry out points as fine as this, a light
copper cylindrical tank may be purchased from stock. It should hold at
least ten gallons of gasoline. In front of the tank is the radiator.
*Controls*. The controls may be located to conform to the builder’s own
ideas of accessibility and convenience. Usually the switch is placed on
the steering column, and it may be of the ordinary _knife_ variety, or
one of the special switches made for this purpose, as taste may dictate.
The throttle control and spark advance may either be in the form of
pedals, working against springs, or of small levers working on a notched
sector, at the side of the seat. The complete control, levers, and
sector may be purchased ready to mount whenever desired, as they are
made in this form for both automobile and marine work. This likewise
applies to the wheel, which it would not pay the amateur to attempt to
make.
Another pedal should work a brake on the front wheel, the brake shoe
consisting of a strip of sheet steel, fastened at one end to the fore
part of the skid and pressed against the wheel by a bamboo rod directly
connected with the brake pedal. An emergency brake can also be made by
loosely bolting a stout bar of steel on the skid near its rear end; one
end of this bar is connected to a lever near the seat, so that when this
lever is pulled back the other end of the bar tends to dig into the
ground. As making a landing is one of the most difficult feats for the
amateur aviator to master and sufficient space for a long run after
alighting is not always available, these brakes will be found a very
important feature of the machine.
[Illustration: Fig. 22. Method of Starting the Engine of an Aeroplane]
The engine is started by swinging the propeller, and this is an
operation requiring far more caution than cranking an automobile motor.
Both hands should be placed on the same blade. Fig. 22, and the latter
should always be pulled downward—never upward. With the switch off,
first turn the propeller over several times to fill the cylinders with
gas, leaving it just ahead of dead center of one of the cylinders, and
with one blade extending upward and to the left at a 45-degree angle.
After closing the switch, take the left blade with both hands and swing
it downward sharply, getting out of the way of the following blade as
quickly as possible.
*Tests*. The first thing to be done after the propeller is finished and
mounted on the engine is to test the combination, or power plant of the
biplane, for speed and thrust, or pulling power. From these two
quantities it will be easy to figure the power that the engine is
delivering. The only instruments necessary are a spring balance reading
to 300 pounds or over; a revolution counter, such as may be procured at
any machinist’s supply house for a dollar or two; and a watch. One end
of the spring balance is fastened to the front end of the skid and the
other to a heavy stake firmly driven in the ground a few feet back. The
wheels of the biplane should be set on smooth boards so that they will
not offer any resistance to the forward thrust. When the engine is
started the spring balance will give a direct reading of the pull of the
propeller.
With one observer noting the thrust, another should check the number of
revolutions the engine is turning per minute. To do this, a small hole
should previously have been countersunk in the hub of the propeller to
receive the conical rubber tip of the revolution counter. The observer
stands behind the propeller, watch in one hand and revolution counter in
the other. At the beginning of the minute period, the counter is pressed
firmly against the hub, and quickly withdrawn at the end of the minute.
A stop watch is naturally an advantage for the purpose. The horse-power
is figured as follows, assuming, for example, a thrust of 250 pounds at
1,200 r.p.m.
250 X 1200 X 3.5 X 100 / 33.000 X 85 = 37 h. p.
As before, the "100/85" allows for the slip and represents the
efficiency of the propeller; 33,000 is the number of foot pounds per
minute or the equivalent of one horse-power, and 3.5 is the pitch of the
propeller.
*Assembling the Biplane*. Assembling the machine complete requires more
space than is available in the average workshop. However, it is possible
to assemble the sections of the planes in a comparatively small room,
carrying the work far enough to make sure that everything will go
together properly when the time comes for complete assembly at the
testing ground. In this case, it is preferable to assemble the end
sections first, standing them away when complete to make room for the
central section, on which the running gear and outriggers are to be
built up.
The builder will have decided by this time whether he will make his
machine on the regular plan, with one main rib between each section, or
on the quick-detachable plan, which has two main ribs on either side of
the central section, as previously explained.
It is desirable to be able to assemble two sections at once and this
should be possible anywhere as it requires a space only about 6 by 13
feet. Two wood 2X4’s, about 12 feet long, should be nailed down on the
blocks on the floor; make these level and parallel to each other at a
distance of 3 feet 6 inches on centers, one being 3 inches higher than
the other. Strips of wood should be nailed on them, so as to hold the
main beams of the frame in place while assembling.
The two front and two rear beam sections are laid in place and joined
with the sheet-steel sleeves, the flanges of the sleeves on the inner
side of the beams. Then through the sleeves in the front beams, which
are, of course, those on the higher bed, drill the holes for the strut
socket bolts (1/4 inch). The holes for the outer ones go through the
projecting ends of the beams; those for the inner ones are half in each
of the two abutting beams. At the end where the central section joins
on, a short length of wood of the same section may be inserted in the
sleeve while drilling the hole. An assistant should hold the beams
firmly together while the holes are being drilled.
Now lay in place the three main ribs belonging to the two sections under
construction and fasten them at the front ends by putting in place the
strut sockets for which the holes have been drilled, with a turnbuckle
plate under each socket, Fig. 16. The strut socket bolt passes through
the main rib and the beam. The bed on which the assembling is being
done, should be cut when sufficiently under the joints to leave room for
the projecting bolt ends. Set the ribs square with the front beams, then
arrange the rear beams so that their joints come exactly under the ribs;
clamp the ribs down and drill a true, vertical hole through the rib
beam, holding the two sections of the beam together as before. Then put
the rear strut sockets in place, using the angle washers previously
described, above and below the rib.
When the quick-detachable plan is followed, the ribs at the inner ends
of the double section, where they join the central section, should be
bolted on an inch from the ends of the beam, using 1/4-inch stove bolts
instead of the socket bolts. The sleeves should be slotted, so that they
can slide off without removing these bolts, as the sleeves and ribs
which occupy the position over the joints of the beams, belong to the
central section.
The sections should now be strung up with the diagonal truss wires which
will make them rigid enough to stand handling. The wires are attached at
each end to the flange bolts of the sleeves. Either one or two
turnbuckles may be used on each wire, as already explained; if but one
turnbuckle be used, the other end of the wire may be conveniently
attached to a strip of sheet steel bent double and drilled for the bolt,
like the sheet-steel slip of a turnbuckle. The attachment, of whatever
nature, should be put between the end and the flange of the sleeve, not
between the two flanges.
Three or four ribs can be used on each section; four are preferable on
sections of full 6-foot length. They are, of course, evenly spaced on
centers. At the front ends, they are attached to the beam by wood screws
through their flattened ferrules. The attachment to the rear beam is
made with a slip of sheet steel measuring 1/2 by 3 inches, bent over the
rib and fastened to the beam at each side with a wood screw. A long wire
nail is driven through the rib itself on the beam.
Four double sections should be built up in this manner, the right and
left upper and the right and left lower sections. Uppers and lowers are
alike except for the inversion of the sockets in the upper sections.
Rights and lefts differ in that the outer beams are long enough to fill
up the sleeves, not leaving room for another beam to join on.
Inserting the struts in their sockets between the upper and lower
sections of the same side will now form either of the two sides of the
machine complete. Care should be taken to get the rear struts the proper
length with respect to the front ones to bring the upper and lower
planes parallel. The distance from the top of the lower front beam to
the top of the upper front beam should be the same as the distance
between the rows of bracing holes in the upper and lower main ribs just
above and below the rear struts—about 4 feet 6 inches. It should hardly
be necessary to mention that the thick edges of the struts come to the
front—they are fish-shaped and a fish is thicker at the head than at the
tail.
The truss wires may now be strung on in each square of the struts,
beams, and main ribs, using turnbuckles as previously described. The
wires should be taut enough to sing a low note when plucked between the
thumb and forefinger. If the construction is carried out properly, the
framework will stand square and true with an even tension on all the
wires. It is permissible for the struts to slant backward a little as
seen from the side, but all should be perfectly in line.
For adjusting the turnbuckles, the builder should make for himself a
handy little tool usually termed a nipple wrench. It is simply a strip
of steel 1 1/2 by 1/2 by 3/32 inches, with a notch cut in the middle of
the long sides to fit the flattened ends of the turnbuckle nipples. This
is much handier than the pliers and does not burr up the nipples.
It has been assumed in this description of the assembling that the
builder is working in a limited space; if, on the contrary, he has room
enough to set up the whole frame at once, the work will be much simpler.
In this case, the construction bed should be 30 feet long. First build
up the upper plane complete, standing it against the wall when finished;
then build the lower plane, put the struts in their sockets, and lay on
the upper plane complete.
Returning to the plan of assembly by sections, after the side sections
or wings of the machine have been completed, the struts may be taken out
and the sections laid aside. The middle section, to which the running
gear and outriggers will be attached, is now to be built up in the same
way. If the builder is following the plan in which there is one main rib
between each section, it will be necessary to take off the four inner
main ribs from the sections already completed, to be used at the ends of
the central section. The plan drawing of the complete machine shows that
the ribs of the central section are cut off just back of the rear beam
to make room for the propeller. This is necessary in order to set the
motor far enough forward to balance the machine properly. The small ribs
in this section have the same curve but are cut off 10 inches shorter at
their rear ends, and the stumps are smoothed down for ferrules like
those for the other small ribs. In the plan which has one main rib
between each section, the main rib on each side of the central section
must be left full length. In the quick-detachable plan with two main
ribs on each side of the central section, the inner ones, which really
belong to this section, are cut off short like the small ribs.
In the drawing of the complete machine, the distance between the struts
which carry the engine bed is shown as 2 feet. This is only approximate,
as the distance must be varied to suit the motor employed. By this time,
the builder will have decided what engine he is going to use—or can
get—and should drill the holes for the sockets of these struts with due
respect to the width of the engine’s supporting feet or lugs,
remembering that the engine bed beams go on the inside of the struts. In
the drawing of the running gear. Fig. 17, the distance between the
engine-bed struts has been designated _A_. The distances, _B_, on each
side are, of course, approximately (6’— 2*A*), whatever _A_ may be.
[Illustration: VIEW OF THE FRENCH AVIATION GROUNDS SHOWING THE HANGARS
RANGED ALONG THE EDGES OF THE FIELD
_This Photograph Protected By International Copyright_]
EXAMINATION PAPER
BUILDING AND FLYING AN
AEROPLANE
*PART I*
*Read Carefully*: Place your name and full address at the head of the
paper. Any cheap, light paper like the sample previously sent you may be
used. Do not crowd your work, but arrange it neatly and legibly. _Do not
copy the answers from the Instruction Paper; use your own words so that
we may be sure that you understand the subject_.
1. What type of machine, biplane or monoplane, makes the best glider
and why?
2. Give the dimensions of a glider which will support a man’s weight.
3. In a glider which has no rudder, how is the machine controlled?
4. Give carefully the details of the start in making a glide.
5. In what direction relative to the wind should a glide be made?
Justify your answer.
6. How must the stability and balance of a glider in flight be
controlled?
7. State the proper conditions for a successful glide.
8. Give the essential characteristics of a Curtiss aeroplane,
defining the various parts.
9. Describe briefly the details of construction of the main
supporting surfaces of a Curtiss.
10. Draw a diagram of the assembled planes showing how the struts and
cross wires are placed to give the required rigidity.
11. Give the details of the running gear of the Curtiss.
12. What is the office of the Curtiss ailerons and how are they
controlled from the operator’s seat? Draw sketch.
13. Describe the details of the front and rear outriggers.
14. What type of propeller is advised for the Curtiss? Give the
details of its construction.
15. Describe carefully the manner in which a propeller should move
through the air in order to give the maximum propulsion.
16. What determines the exact location of the motor in the aeroplane?
17. Give correct method of starting the motor when ready for a flight.
18. What tests should be conducted before a flight is undertaken?
*After completing the work, add and sign the following statement:*
I hereby certify that the above work is entirely my own.
(Signed)
PART II
BUILDING A BLERIOT MONOPLANE
As mentioned in connection with the description of its construction, the
Curtiss biplane was selected as a standard of this type of aeroplane
after which the student could safely pattern for a number of reasons. It
is not only remarkably simple in construction, easily built by anyone
with moderate facilities and at a slight outlay, but it is likewise the
easiest machine to learn to drive. The monoplane is far more _difficult_
and _expensive_ to build.
The Bleriot may be regarded as the most typical example in this field,
in view of its great success and the very large numbers which have been
turned out. In fact, the Bleriot monoplane is the product of a factory
which would compare favorably with some of the large automobile plants.
Its construction requires skillful workmanship both in wood and metal,
and a great many special castings, forgings, and stampings are
necessary. Although some concerns in this country advertise that they
carry these fittings as stock parts, they are not always correct in
design and, in any case, are expensive. Wherever it is possible to avoid
the use of such parts by any expedient, both forms of construction are
described, so that the builder may take his choice.
Bleriot monoplanes are made in a number of different models, the
principal ones being the 30-horse-power "runabout," Figs. 23 and 24, the
50- and 70-horse-power passenger-carrying machines, and the 50-, 70-,
and 100-horse-power racing machines. Of these the first has been chosen
as best adapted to the purpose. Its construction is typical of the
higher-power monoplanes of the same make, and it is more suitable for
the beginner to fly as well as to build. It is employed exclusively by
the Bleriot schools.
[Illustration: Fig. 23. Details of Bleriot Monoplane]
*Motor*. The motor regularly employed is the 30-horse-power,
three-cylinder Anzani, a two-cylinder type of which is shown in
"Aeronautical Motors" Fig. 40. From the amateur’s standpoint, a
disadvantage of the Bleriot is the very short space allowed for the
installation of the motor. For this reason, the power plant must be fan
shaped, like the Anzani; star form, like the Gnome; or of the
two-cylinder opposed type. It must likewise be air-cooled, as there is
no space available for a radiator.
[Illustration: Fig. 24. Side Elevation of Bleriot Monoplane]
[Illustration: Fig. 25. Top and Side View of Bleriot Fuselage on Which
Machine Is Assembled]
*Fuselage*. Like most monoplanes, the Bleriot has a long central body,
usually termed "fuselage," to which the wings, running gear, and
controls are all attached. A drawing of the fuselage with all dimensions
is reproduced in Fig. 25, and as the machine is, to a large extent,
built up around this essential, its construction is taken up first. It
consists of four long beams united by 35 crosspieces. The beams are of
ash, 1 3/16 inches square for the first third of their length and
tapering to 7/8 inch square at the rear ends. Owing to the difficulty of
securing good pieces of wood the full length, and also to facilitate
packing for shipment, the beams are made in halves, the abutting ends
being joined by sleeves of 1 1/8-inch, 20-gauge steel tubing, each held
on by two 1/8-inch bolts. Although the length of the fuselage is 21 feet
11 1/4 inches, the beams must be made of two 11-foot halves to allow for
the curve at the rear ends.
[Illustration: Fig. 26. Details of U-bolt Which is a Feature of Bleriot
Construction]
The struts are also of ash, the majority of them being 7/8 by 1 1/4
inches, and oval in section except for an inch and a half at each end.
But the first, second, and third struts (counting from the forward end)
on each side, the first and second on the top, and the first strut on
the bottom are 1 3/16 inches square, of the same stock as the main
beams. Practically all of the struts are joined to the main beams by
U-bolts, as shown by the detail drawing, Fig. 26, this being one of
Louis Bleriot’s inventions. The small struts are held by 1/8-inch bolts
and the larger ones by 3/16-inch bolts. The ends of the struts must be
slotted for these bolts, this being done by drilling three holes in a
row with a 5/32- or 7/32-inch drill, according to whether the slot is
for the smaller or larger size bolt. The wood between the holes is cut
out with a sharp knife and the slot finished with a coarse, flat file.
All of the U-bolts measure 2 inches between the ends. The vertical
struts are set 1 inch forward of the corresponding horizontal struts, so
that the four holes through the beam at each joint are spaced 1 inch
apart, alternately horizontal and vertical. To the projecting angles of
the U-bolts are attached the diagonal truss wires, which cross all the
rectangles of the fuselage, except that in which the driver sits. This
trussing should be of 20-gauge piano wire (music-wire gauge) or
1/10-inch cable, except in the rectangles bounded by the large struts,
where it should be 25-gauge piano wire or 3/32-inch cable. Each wire, of
course, should have a turnbuckle. About 100 of these will be required,
either of the spoke type or the regular type, with two screw eyes—the
latter preferred.
Transverse squares, formed by the two horizontal and two vertical struts
at each point, are also trussed with diagonal wires. Although
turnbuckles are sometimes omitted on these wires, it takes considerable
skill to get accurate adjustments without them. The extreme rear strut
to which the rudder is attached, is not fastened in the usual way. It
should be cut with tongues at top and bottom, fitting into notches in
the ends of the beams, and the whole bound with straps of 20-gauge sheet
steel, bolted through the beams with 1/8-inch bolts.
Continuing forward, the struts have no peculiarity until the upper
horizontal one is reached, just behind the driver’s seat. As it is
impossible to truss the quadrangle forward of this strut, owing to the
position of the driver’s body, the strut is braced with a U-shaped
half-round strip of 1/2 by 1 inch of ash or hickory bolted to the beams
at the sides and to the strut at the rear, with two 1/8-inch bolts at
each point. The front side of the strut should be left square where this
brace is in contact with it. The brace should be steam bent with the
curves on a 9-inch radius, and the half-round side on the inside of the
curve.
The vertical struts just forward of the driver’s seat carry the inner
ends of the rear wing beams. Each beam is attached with a single bolt,
giving the necessary freedom to rock up and down in warping the wings.
The upper 6 inches of each of these struts fits into a socket designed
to reinforce it. In the genuine Bleriot, this socket is an aluminum
casting. However, a socket which many would regard as even better can be
made from a 7-inch length of 20-gauge 1 1/8-inch square tubing. One end
of the tube is sawed one inch through the corners; two opposite sides
are then bent down at right angles to form flanges, and the other two
sides sawed off. A 1- by 3-inch strip of 20-gauge sheet steel, brazed
across the top and flanges completes the socket. With a little care, a
very creditable socket can be made in this way. Finally, with the strut
in place, a 3/8-inch hole is drilled through 4 inches from the top of
the socket for the bolt securing the wing beam.
The upper horizontal strut at this point should be arched about six
inches to give plenty of elbow room over the steering wheel. The bending
should be done in a steam press. The strut should be 1 3/16 inches
square, cut sufficiently long to allow for the curve, and fitted at the
ends with sockets as described above, but set at an angle by sawing the
square tube down further on one side than on the other.
On the two lower beams, is laid a floor of half-inch boards, extending
one foot forward and one foot back of the center line of the horizontal
strut. This floor may be of spruce, if it is desired to save a little
weight, or of ordinary tongue-and-grooved floor boards, fastened to the
beams with wood screws or bolts. The horizontal strut under this floor
may be omitted, but its presence adds but little weight and completes
the trussing. Across the top of the fuselage above the first upper
horizontal strut, lies a steel tube which forms the sockets for the
inner end of the front wing beams. This tube is 1 3/4 inches diameter,
18 gauge, and 26 3/4 inches long. It is held fast by two steel straps,
16 gauge and 1 inch wide, clamped down by the nuts of the vertical strut
U-bolts. The center of the tube is, therefore, in line with the center
of the vertical struts, not the horizontal ones. The U-bolts which make
this attachment are, of course, the 3/16-inch size, and one inch longer
on each end than usual. To make a neat job, the tube may be seated in
wood blocks, suitably shaped, but these must not raise it more than a
small fraction of an inch above the top of the fuselage, as this would
increase the angle of incidence of the wings.
The first vertical struts on each side are extras, without corresponding
horizontal ones; they serve only to support the engine. When the Gnome
motor is used, its central shaft is carried at the centers of two
*X*-shaped, pressed-steel frames, one on the front side, flush with the
end of the fuselage and one on the rear.
*Truss Frame Built on Fuselage*. In connection with the fuselage may be
considered the overhead truss frame and the warping frame. The former
consists of two inverted *V*’s of 20-gauge, 1- by 3/8-inch oval tubing,
joined at their apexes by a 20-gauge, 3/4-inch tube. Each *V* is formed
of a single piece of the oval tubing about 5 feet long. The flattened
ends of the horizontal tube are fastened by a bolt in the angles of the
*V*’s. The center of the horizontal tube should be 2 feet above the top
of the fuselage. The flattened lower ends of the rear *V* should be
riveted and brazed to strips of 18-gauge steel, which will fit over the
bolts attaching the vertical fuselage struts at this point. The legs of
the front *V* should be slightly shorter, as they rest on top of the
wing socket tube. Each should be held down by a single 3/16-inch bolt,
passing through the upper wall of the tube and its retaining strap;
these bolts also serve the purpose of preventing the tube from sliding
out from under the strap. Each side of the frame is now braced by
diagonal wires (No. 20 piano wire, or 1/14-inch cable) with turnbuckles.
At the upper corners of this frame are attached the wires which truss
the upper sides of the wings. The front wires are simply fastened under
the head and nut of the bolt which holds the frame together at this
corner. The attachment of the rear wires, however, is more complex, as
these wires must run over pulleys to allow for the rocking of the rear
wing beams when the wings are warped. To provide a suitable place for
the pulleys, the angle of the rear *V* is enclosed by two plates of
20-gauge sheet steel, one on the front and one on the rear, forming a
triangular box 1 inch thick fore and aft, and about 2 inches on each
side, only the bottom side being open. These plates are clamped together
by a 3/16-inch steel bolt, on which are mounted the pulleys. There
should be sufficient clearance for pulleys 1 inch in diameter. The wires
running over these pulleys must then pass through holes drilled in the
tube. The holes should not be drilled until the wings are on, when the
proper angle for them can be seen. The cutting and bending of the steel
plates is a matter of some difficulty, and should not be done until the
frame is otherwise assembled, so that paper patterns can be cut for
them. They should have flanges bent around the tube, secured by the
bolts which hold the frame together, to keep them from slipping off.
The oval tubing is used in the vertical parts of this frame, principally
to reduce the wind resistance, being placed with the narrow side to the
front. However, if this tubing be difficult to obtain, or if price is a
consideration, no harm will be done by using 3/4-inch round tubing.
Beneath the floor of the driver’s cockpit in the fuselage is the warping
frame, the support for the wires which truss the rear wing beams and
also control the warping.
This frame is built up of four 3/4-inch, 20-gauge steel tubes, each
about 3 feet long, forming an inverted, 4-sided pyramid. The front and
back pairs of tubes are fastened to the lower fuselage beams with
3/16-inch bolts at points 15 inches front and back of the horizontal
strut. At their lower ends the tubes are joined by a fixture which
carries the pulleys for the warping wires and the lever by which the
pulleys are turned. In the genuine Bleriot, this fixture is a special
casting. However, a very neat connection can be made with a piece of
1/16-inch steel stock, 1 1/4 by 6 inches, bent into a *U*-shape with the
legs 1 inch apart inside. The flattened ends of the tubes are riveted
and brazed to the outside upper corners of the *U*, and a bolt to carry
the pulleys passes through the lower part, high enough to give clearance
for 2-inch pulleys. This frame needs no diagonal wires.
*Running Gear*. Passing now to the running gear, the builder will
encounter the most difficult part of the entire machine, and it is
impossible to avoid the use of a few special castings. The general plan
of the running gear is shown in the drawing of the complete machine.
Figs. 23 and 24, while some of the details are illustrated in Fig. 27,
and the remainder are given in the detail sheet, Fig. 28. It will be
seen that each of the two wheels is carried in a double fork, the lower
fork acting simply as a radius rod, while the upper fork is attached to
a slide which is free to move up and down on a 2-inch steel tube. This
slide is held down by two tension springs, consisting of either rubber
tubes or steel coil springs, which absorb the shocks of landing. The
whole construction is such that the wheels are free to pivot sideways
around the tubes, so that when landing in a quartering wind the wheels
automatically adjust themselves to the direction of the machine.
[Illustration: A FRENCH DEVELOPMENT OF THE WRIGHT MACHINE BUILT UNDER
THE WRIGHT PATENTS
There is Little Resemblance to the Original Except in Wing Form and
Warping]
_Framework_. The main framework of the running gear consists of two
horizontal beams, two vertical struts, and two vertical tubes. The beams
are of ash, 4 3/4 inches wide in the middle half, tapering to 3 3/4
inches at the ends, and 5 feet 2 3/4 inches long overall. The upper beam
is H inch thick and the lower 1 inch. The edges of the beams are rounded
off except at the points where they are drilled for bolt holes for the
attachment of other parts. The two upper beams of the fuselage rest on
these beams and are secured to them by two 3/16-inch bolts each.
The vertical struts are also of ash, 1 3/16 inch by 3 inches and 4 feet
2 inches long overall. They have tenons at each end which fit into
corresponding square holes in the horizontal beams. The two lower
fuselage beams are fastened to these struts by two 3/16-inch through
bolts and steel angle plates formed from 1/16-inch sheet steel. The
channel section member across the front sides of these struts is for the
attachment of the motor, and will be taken up later. The general
arrangement at this point depends largely on what motor is to be used,
and the struts should not be rounded or drilled for bolt holes until
this has been decided.
From the lower ends of these struts _CC_, Fig. 27, diagonal struts _DD_
run back to the fuselage. These are of ash, 1 3/16 by 2 1/2 inches and 2
feet inches long. The rear ends of the struts _DD_ are fastened to the
fuselage beams by the projecting ends of the *U*-bolts of the horizontal
fuselage struts, and also by angle plates of sheet steel. At the lower
front ends the struts _DD_ are fastened to the struts _CC_ and the beam
_E_ by steel angle plates, and the beam is reinforced by other plates on
its under side.
_Trussing_. In the genuine Bleriot, the framework is trussed by a single
length of steel tape, 1 1/8 by 1/16 inch and about 11 feet long,
fastened to U-bolts in the beam _A_, Fig. 27. This tape runs down one
side, under the beam _E_, and up the other side, passing through the
beam in two places, where suitable slots must be cut. The tape is not
made in this country, but must be imported at considerable expense.
Ordinary sheet steel will not do. If the tape can not be obtained, a
good substitute is 1/8-inch cable, which then would be made in two
pieces and fastened to eye bolts at each end.
[Illustration: Fig. 27. Details of Bleriot Running Gear]
[Illustration: Fig. 28. Details of Various Fittings for Bleriot
Monoplane]
The two steel tubes are 2 inches in diameter, 18-gauge, and about 4 feet
10 inches long. At their lower ends they are flattened, but cut away so
that a 2-inch ring will pass over them. To these flattened ends are
attached springs and wires which run from each tube across to the hub of
the opposite wheel. The purpose of these is simply to keep the wheels
normally in position behind the tubes. The tubes, it will be noticed,
pass through the lower beam, but are sunk only 1/8 inch into the upper
beam. They are held in place by sheet-steel sockets on the lower side of
the upper beam and the upper side of the lower beam. The other sides of
the beams are provided with flat plates of sheet steel. The genuine
Bleriot has these sockets stamped out of sheet steel, but as the amateur
builder will not have the facilities for doing this, an alternative
construction is given here.
In this method, the plates are cut out to pattern, the material being
sheet steel 1/16 inch thick, and a 1/2-inch hole drilled through the
center, a 2-inch circle then being drawn around this. Then, with a cold
chisel a half dozen radial cuts are made between the hole and the
circle. Finally this part of the plate is heated with a blow-torch and a
2-inch piece of pipe driven through, bending up the triangular corners.
These bent up corners are then brazed to the tubes, and a strip of light
sheet steel is brazed on to cover up the sharp edges. Of course, the
brazing should not be done until the slides _GG_, Figs. 27 and 28, have
been put on. When these are once in place, they have to stay on and a
breakage of one of them, means the replacement of the tube as well. This
is a fault of the Bleriot design that can not well be avoided. It should
be noticed that the socket at the upper end, as well as its
corresponding plate on the other side of the beam, has extensions which
reinforce the beam where the eye bolts or *U*-bolts for the attachment
of the steel tape pass through.
_Forks_. Next in order are the forks which carry the wheels. The short
forks _JJ_, Figs. 27 and 28, which act simply as radius rods, are made
of 1- by 3/8-inch oval tubing, a stock size which was specified for the
overhead truss frame. It will be noticed that these are in two parts,
fastened together with a bolt at the front end. The regular Bleriot
construction calls for forged steel eyes to go in the ends of tubes, but
these will be hard to obtain. The construction shown in the drawings is
much simpler. The ends of the tubes are heated and flattened until the
walls are about 1/16 inch apart inside. Then a strip of 1/16-inch sheet
steel is cut the right width to fit in the flattened end of the tube,
and brazed in place. The bolt holes then pass through the combined
thickness of the tube and the steel strip, giving a better bearing
surface, which may be further increased by brazing on a washer.
The long forks _FF_, which transmit the landing shocks to the springs,
are naturally made of heavier material. The proper size tubing for them
is 1 1/8 by 5/8 inches, this being the nearest equivalent to the 14 by
28 mm French tubing. However, this is not a stock size in this country
and can only be procured by order, or it can be made by rolling out
15/16-inch round tubing. If the oval tubing can not be secured, the
round can be employed instead, other parts being modified to correspond.
The ends are reinforced in the same way as described for the small
forks.
These forks are strengthened by aluminum clamps _H_, Figs. 27 and 28,
which keep the tubes from spreading apart. Here, of course, is another
call for special castings, but a handy workman may be able to improvise
a satisfactory substitute from sheet steel. On each tube there are four
fittings: At the bottom, the collar _M_ to which the fork _J_ is
attached, and above, the slide _G_ and the clamps _K_ and _L_, which
limit its movement. The collar and slide should be forged, but as this
may be impossible, the drawings have been proportioned for castings. The
work is simple and may be done by the amateur with little experience.
The projecting studs are pieces of 3/4-inch, 14-gauge steel tubing
screwed in tight and pinned, though if these parts be forged, the studs
should be integral.
The clamps which limit the movement of the slides are to be whittled out
of ash or some other hard wood. The upper clamp is held in place by four
bolts, which are screwed up tight; but when the machine makes a hard
landing the clamp will yield a little and slip up the tube, thus
deadening the shock. After such a landing, the clamps should be
inspected and again moved down a bit, if necessary. The lower clamps,
which, of course, only keep the wheels from hanging down too far, have
bolts passing clear through the tubes.
To the projecting lugs on the slides _GG_ are attached the rubber tube
springs, the lower ends connecting with eye bolts through the beam _E_.
These rubber tubes, of which four will be needed, are being made by
several companies in this country and are sold by supply houses. They
should be about 14 inches long, unstretched, and 1 1/4 inches in
diameter, with steel tips at the ends for attachment.
_Hub Attachments_. The hubs of the two wheels are connected with the
link _P_, with universal joints _N N_ at each end. In case the machine
lands while drifting sidewise, the wheel which touches the ground first
will swing around to head in the direction in which the machine is
actually moving, and the link will cause the other wheel to assume a
parallel position; thus the machine can run diagonally on the ground
without any tendency to upset.
This link is made of the same 1- by 3/8-inch oval tubing used elsewhere
in the machine. In the original Bleriot, the joints are carefully made
up with steel forgings. But joints which will serve the purpose can be
improvised from a 1-inch cube of hard wood and three steel straps, as
shown in the sketch, Fig. 27. From each of these joints a wire runs
diagonally to the bottom of the tube on the other side, with a spring
which holds the wheel in its normal position. This spring should be
either a rubber tube, like those described above, but smaller, or a
steel coil spring. In the latter case, it should be of twenty 3/4-inch
coils of No. 25 piano wire.
_Wheels_. The wheels are regularly 28 by 2 inches, corresponding to the
700 by 50 mm French size, with 30 spokes of 12-gauge wire. The hub
should be 5 1/4 inches wide, with a 5/8-inch bolt. Of course, these
sizes need not be followed exactly, but any variations will involve
corresponding changes in the dimensions of the forks. The long fork goes
on the hub inside of the short fork, so that the inside measurement of
the end of the big fork should correspond to the width of the hub, and
the inside measurement of the small fork should equal the outside
measurement of the large fork.
_Rear Skid_. Several methods are employed for supporting the rear end of
the fuselage when the machine is on the ground. The first Bleriot
carried a small wheel in a fork provided with rubber springs, the same
as the front wheels. The later models, however, have a double *U*-shaped
skid, as shown in Figs. 23 and 24. This skid is made of two 8-foot
strips of ash or hickory 1/2 by 3/4 inches, steamed and bent to the
*U*-shape as shown in the drawing of the complete machine.
[Illustration: Fig. 29. Details of Framework of Bleriot Main Supporting
Planes]
*Wings*. Having completed the fuselage and running gear, the wings are
next in order. These are constructed in a manner which may seem
unnecessarily complicated, but which gives great strength for
comparatively little weight. Each wing contains two stout ash beams
which carry their share of the weight of the machine, and 12 ribs which
give the proper curvature to the surfaces and at the same time reinforce
the beams. These ribs in turn are tied together and reinforced by light
strips running parallel to the main beams.
[Illustration: Fig. 30. Complete Rib of Bleriot Wing and Pattern from
Which Web Is Cut]
In the drawing of the complete wing. Fig. 29, the beams are designated
by the letters _B_ and _E_. _A_ is a sheet aluminum member intended to
hold the cloth covering in shape on the front edge. _C_, _D_, and _F_
are pairs of strips (one strip on top, the other underneath) which tie
the ribs together. _G_ is a strip along the rear edge, and _H_ is a bent
strip which gives the rounded shape to the end of the wing. The ribs are
designated by the numbers 1 to 12 inclusive.
_Ribs_. The first and most difficult operation is to make the ribs.
These are built up of a spruce board 3/16 inch thick, cut to shape on a
jig saw, with 3/16- by 5/8-inch spruce strip stacked and glued to the
upper and lower edges. Each rib thus has an I-beam section, such as is
used in structural steel work and automobile front axles. Each of the
boards, or webs as they are usually called, is divided into three parts
by the main beams which pass through it. Builders sometimes make the
mistake of cutting out each web in three pieces, but this makes it very
difficult to put the rib together accurately. Each web should be cut out
of a single piece, as shown in the detail drawing. Fig. 30, and the
holes for the beams should be cut in after the top and bottom strips
have been glued on.
The detail drawing, Fig. 30, gives the dimensions of a typical rib. This
should be drawn out full size on a strip of tough paper, and then a
margin of 3/16 inch should be taken off all round except at the front
end where the sheet aluminum member _A_ goes on. This allows for the
thickness of the top and bottom strips. In preparing the pattern for the
jig saw, the notches for strips _C_, _D_, and _F_ should be disregarded;
neither should it be expected that the jig-saw operator will cut out the
oval holes along the center of the web, which are simply to lighten it.
The notches for the front ends of the top and bottom strips should also
be smoothed over in the pattern.
When the pattern is ready, a saw or planing mill provided with a saw
suitable for the work, should cut out the 40 ribs (allowing a sufficient
number for defective pieces and breakage) for about $2. The builder then
cuts the notches and makes the oval openings with an auger and keyhole
saw. Of course, these holes need not be absolutely accurate, but at
least 3/4 inch of wood should be left all around them.
Nine of the twelve ribs in each wing are exactly alike. No. 1, which
forms the inner end of the wing, does not have any holes cut in the web,
and instead of the slot for the main beam _B_, has a 1 3/4-inch round
hole, as the stub end of the beam is rounded to fit the socket tube.
(See Fig. 23.) Rib No. 11 is 5 feet 10 1/2 inches long, and No. 12 is 3
feet long. These can be whittled out by hand, and the shape for them
will be obvious as soon as the main part of the wing is put together.
The next step is to glue on the top and bottom strips. The front ends
should be put on first and held, during the drying, in a screw clamp,
the ends setting close up into the notches provided for them. Thin
1/2-inch brads should be driven in along the top and bottom at 1- to
2-inch intervals. The rear ends of the strips should be cut off to the
proper length and whittled off a little on the inside, so that there
will be room between them for the strip _G_, 1/4 inch thick. Finally,
cut the slots for the main beams, using a bit and brace and the keyhole
saw, and the ribs will be ready to assemble.
_Beams and Strips_. The main beams are of ash, the front beam in each
wing being 3 1/4 by 3/4 inches and the rear beam 2 1/2 by 5/8 inches.
They are not exactly rectangular but must be planed down slightly on the
top and bottom edges, so that they will fit into the irregularly-shaped
slots left for them in the ribs. The front beams, as mentioned above,
have round stubs which fit into the socket tube on the fuselage. These
stubs may be made by bolting short pieces of ash board on each side of
the end of the beam and rounding down the whole.
To give the wings their slight inclination, or dihedral angle, which
will be apparent in the front view of the machine, the stubs must lie at
an angle of 2 1/2 degrees with the beam itself. This angle should be
laid out very carefully, as a slight inaccuracy at this point will
result in a much larger error at the tips. The rear beams project about
2 inches from the inner ribs. The ends should be reinforced with bands
of sheet steel to prevent splitting, and each drilled with a 3/8-inch
hole for the bolt which attaches to the fuselage strut. A strip of heavy
sheet steel should be bent to make an angle washer to fill up the
triangular space between the beam and the strut; the bolt hole should be
drilled perpendicularly to the beam, and not to the strut. The outer
ends of the beams, beyond rib No. 10, taper down to 1 inch deep at the
ends.
The aluminum member _A_, Fig. 29, which holds the front edge of the wing
in shape, is made of a 4-inch strip of fairly heavy sheet aluminum,
rolled into shape round a piece of half-round wood, 2 1/4 inches in
diameter. As sheet aluminum usually comes in 6-foot lengths, each of
these members will have to be made in two sections, joined either by
soldering (if the builder has mastered this difficult process) or by a
number of small copper rivets.
No especial difficulties are presented by the strips, _C_, _D_, and _F_,
which are of spruce 3/16 by 5/8 inch, or by the rear edge strip _G_, of
spruce 1/4 by 1 1/2 inches. Each piece _H_ should be 1 by 1/2 inch
half-round spruce, bent into shape, fitted into the aluminum piece at
the front, and at the rear flattened down to 1/4 inch and reinforced by
a small strip glued to the back, finally running into the strip _G_. The
exact curve of this piece does not matter, provided it is the same on
both wings.
_Assembling the Wings_. Assembling the wings is an operation which
demands considerable care. The main beams should first be laid across
two horses, set level so that there will be no strain on the framework
as it is put together. Then the 12 ribs should be slipped over the beams
and evenly spaced 13 inches apart to centers, care being taken to see
that each rib stands square with the beams, Fig. 31. The ribs are not
glued to the beams, as this would make repairs difficult, but are
fastened with small nails.
Strips _C_, _D_, and _F_, Fig, 29, are next put in place, simply being
strung through the rows of holes provided for them in the ribs, and
fastened with brads. Then spacers of 3/16-inch spruce, 2 or 3 inches
long, are placed between each pair of strips halfway between each rib,
and fastened with glue and brads. This can be seen in the broken-off
view of the wing in the front view drawing, Fig. 23. The rear edge strip
fits between the ends of the top and bottom strips of the ribs, as
mentioned above, fastened with brads or with strips of sheet-aluminum
tacked on.
[Illustration: Fig. 31. Assembling the Main Planes of a Bleriot
Monoplane]
Each wing is trussed by eight wires, half above and half below; half
attached to the front and half to the rear beam. In the genuine Bleriot
steel tape is used for the lower trussing of the main beams, similar to
the tape employed in the running gear, but American builders prefer to
use 1/8-inch cable. The lower rear trussing should be 3/32- or 7/64-inch
cable, and the upper trussing 3/32-inch.
The beams are provided with sheet-steel fixtures for the attachment of
the cables, as shown in the broken-off wing view, Fig. 23. These are cut
from fairly-heavy metal, and go in pairs, one on each side of the end
beam, fasten with three 3/16-inch bolts. They have lugs top and bottom.
They are placed between the fifth and sixth and ninth and tenth ribs on
each side.
To resist the backward pressure of the air, the wings are trussed with
struts of 1-inch spruce and 1/16-inch cable, as shown in Fig. 23. The
struts are placed between the cable attachments, being provided with
ferrules of flattened steel tubing arranged to allow the rear beam
freedom to swing up and down. The diagonal cables are provided with
turnbuckles and run through the open spaces in the ribs.
*Control System*. The steering gear and tail construction of the Bleriot
are as distinctive as the swiveling wheels and the *U*-bolts, and the
word "cloche" applied to the bell-like attachment for the control wires,
has been adopted into the international vocabulary of aeroplaning. The
driver has between his knees a small steering wheel mounted on a short
vertical post. This wheel does not turn, but instead the post has a
universal joint at the bottom which allows it to be swung backward and
forward or to either side. The post is really a lever, and the wheel a
handle. Encircling the lower part of the post is a hemispherical
bell—the cloche—with its bottom edge on the same level as the universal
joint.
Four wires are attached to the edge of the cloche. Those at the front
and back are connected with the elevator, and those at the sides with
the wing-warping lever. The connections are so arranged that pulling the
wheel back starts the machine upward, while pushing it forward causes it
to descend, and pulling to either side lowers that side and raises the
other. The machine can be kept on a level keel by the use of the wheel
and cloche alone; the aviator uses them just as if they were rigidly
attached to the machine, and by them he could move the machine bodily
into the desired position.
In practice, however, it has been found that lateral stability can be
maintained more easily by the use of the vertical rudder than by
warping. This is because the machine naturally tips inward on a turn,
and, consequently, a tip can be corrected by a partial turn in the other
direction. If, for example, the machine tips to the right, the aviator
steers slightly to the left, and the machine comes back to a level keel
without any noticeable change in direction. Under ordinary circumstances
this plan is used altogether, and the warping is used only on turns and
in bad weather.
It will be noticed that the Bleriot control system is almost identical
with that of the Henri Farman biplane, the only difference being that in
the Farman the cloche and wheel are replaced by a long lever. The
movements, however, remain the same, and as there are probably more
Bleriot and Farman machines in use than all other makes together, this
control may be regarded almost as a standard. It is not as universal as
the steering wheel, gear shift, and brake levers of the automobile, but
still it is a step in the right direction.
[Illustration: Fig. 32. Control Device of Steel Tubing instead of
Bleriot "Cloche"]
In the genuine Bleriot, the cloche is built up of two bells, one inside
the other, both of sheet aluminum about 1/16 inch thick. The outer bell
is 11 inches in diameter and 3 1/2 inches deep, and the inner one 10
inches in diameter and 2 inches deep. A ring of hard wood is clamped
between their edges and the steering column, an aluminum casting passing
through their centers. This construction is so complicated and requires
so many special castings and parts that it is almost impossible for the
amateur.
_Steering Gear_. While not so neat, the optional construction shown in
the accompanying drawing, Fig. 32, is equally effective. In this plan,
the cloche is replaced by four *V*-shaped pieces of 1/2-inch, 20-gauge
steel tubing, attached to a steering post of 1-inch, 20-gauge tubing. At
the lower end, the post has a fork, made of pieces of smaller tubing
bent and brazed into place, and this fork forms part of the universal
joint on which the post is mounted. The cross of the universal joint,
which is somewhat similar to those employed on automobiles, can best be
made of two pieces of heavy tubing, 1/2 inch by 12 gauge, each cut half
away at the middle. The two pieces are then fastened together by a small
bolt and brazed for greater security. The ends which are to go into the
fork of the steering post must then be tapped for 3/8-inch machine
screws. The two other ends of the cross are carried on *V*’s of
1/2-inch, 20-gauge tubing, spread far enough apart at the bottom to make
a firm base, and bolted to the floor of the cockpit.
The steering wheel itself is comparatively unimportant. On the genuine
Bleriot it is a solid piece of wood 8 inches in diameter, with two holes
cut in it for hand grips. On the post just under the wheel are usually
placed the spark and throttle levers. It is rather difficult, however,
to arrange the connections for these levers in such a way that they will
not be affected by the movements of the post, and for this reason many
amateur builders place the levers at one side on one of the fuselage
beams.
From the sides of the cloche, or from the tubing triangles which may be
substituted for it, two heavy wires run straight down to the ends of the
warping lever. This lever, together with two pulleys, is mounted at the
lower point of the warping frame already described. The lever is 12
inches long, 11 inches between the holes at its ends, and 2 inches wide
in the middle; it should be cut from a piece of sheet steel about 1/16
inch thick. The pulleys should be 2 1/2 inches in diameter, one of them
bolted to the lever, the other one running free. The wires from the
outer ends of the rear wing beams are joined by a piece of flexible
control cable, which is given a single turn over the free pulley. The
inner wires, however, each have a piece of flexible cable attached to
their ends, and these pieces of cable, after being given a turn round
the other pulley, are made fast to the opposite ends of the warping
lever. These cables should be run over the pulleys, not under, so that
when the cloche is pulled to the right, the left wing will be warped
downward.
It is a common mistake to assume that both pulleys are fastened to the
warping lever; but when this is done the outer wire slackens off and
does not move in accord with the inner wire, on account of the different
angles at which they work.
_Foot Levers_. The foot lever for steering is cut from a piece of wood
22 inches long, hollowed out at the ends to form convenient rests for
the feet. The wires connecting the lever to the rudder may either be
attached to this lever direct, or, if a neater construction is desired,
they may be attached to another lever under the floor of the cockpit. In
the latter case, a short piece of 1-inch steel tubing serves as a
vertical shaft to connect the two levers, which are fastened to the
shaft by means of aluminum sockets such as may be obtained from any
supply house. The lower lever is 12 inches long and 2 inches wide, cut
from 1/16-inch steel similar to the warping lever.
Amateur builders often cross the rudder wires so that pressing the lever
to the right will cause the machine to steer to the left. This may seem
more natural at first glance, but it is not the Bleriot way. In the
latter, the wires are not crossed, the idea being to facilitate the use
of the vertical rudder for maintaining lateral equilibrium. With this
arrangement, pressing the lever with the foot on the high side of the
machine tends to bring it back to an even keel.
_Tail and Elevator_. The tail and elevator planes are built up with ribs
and tie strips in much the same manner as the wings. However, it will
hardly pay to have these ribs cut out on a jig saw unless the builder
can have this work done very cheaply. It serves the purpose just as well
to clamp together a number of strips of 3/16-inch spruce and plane them
down by hand. The ribs when finished should be 24 1/4 inches long. The
greatest depth of the curve is 1 1/4 inches, at a point one-third of the
way back from the front edge, and the greatest depth of the ribs
themselves 2 1/4 inches, at the same point. Sixteen ribs are required.
A steel tube 1 inch by 20 gauge, _C_, Fig. 33, runs through both tail
and elevators, and is the means of moving the latter. Each rib at the
point where the tube passes through, is provided with an aluminum
socket. Those on the tail ribs act merely as bearings for the tube, but
those on the elevator ribs are bolted fast, so that the elevators must
turn with the tube. At its center the tube carries a lever _G_, of
1/16-inch steel 12 by 2 inches, fastened on by two aluminum sockets, one
on each side. From the top of the lever a wire runs to the front side of
the cloche, and from the bottom a second wire runs to the rear side of
the cloche.
[Illustration: Fig. 33. Construction Details of Bleriot Tail, Elevators,
and Rudder]
[Illustration: AN OLD DUTCH WINDMILL AND A MODERN FRENCH AEROPLANE
_This Photograph Protected By International Copyright_]
[Illustration: VIEW OF THE R. E. P. MOTOR AND LANDING GEAR
This Machine is the Work of One of the Cleverest Aeroplane Designers in
Europe]
The tube is carried in two bearings _HH_, attached to the lower beams of
the fuselage. These are simply blocks of hard wood, fastened by steel
strips and bolts. The angle of incidence of the tail is adjustable, the
tail itself being held in place by two vertical strips of steel rising
from the rear edge and bolted to the fuselage, as shown in the drawing,
Fig. 33. To prevent the tail from folding up under the air pressure to
which it is subjected, it is reinforced by two 3/4-inch, 20-gauge steel
tubes running down from the upper sides of the fuselage, as shown in the
drawing of the complete machine, Fig. 23.
The tail and elevators have two pairs of tie strips, _B_ and _D_, Fig.
33, made of 3/16- by 5/8-inch spruce. The front edge _A_ is half round,
1- by 1/2-inch spruce, and the rear edge _E_ is a spruce strip 1/4- by 1
1/2-inches. The end pieces are curved.
_Rudder_. The rudder is built up on a piece of 1-inch round spruce _M_,
corresponding in a way to the steel tube used for the elevators. On this
are mounted two long ribs _KK_, and a short rib _J_, made of spruce 3/8
inch thick and 1 3/8 inches wide at the point where _M_ passes through
them. They are fastened to _M_ with 1/8-inch through bolts. The rudder
lever _N_, of 1/16-inch steel, 12 by 2 inches, is laid flat on _J_ and
bolted in place; it is then trussed by wires running from each end to
the rear ends of _KK_. From the lever other wires also run forward to
the foot lever which controls the rudder.
The wires to the elevator and rudder should be of the flexible cable
specially made for this purpose, and should be supported by fairleaders
attached to the fuselage struts. Fairleaders of different designs may be
procured from supply houses, or may be improvised. Ordinary screw eyes
are often used, or pieces of copper tubing, bound to the struts with
friction tape.
*Covering the Planes*. Covering the main planes, tail, elevators, and
rudder may well be left until the machine is otherwise ready for its
trial trip, as the cloth will not then be soiled by the dust and grime
of the shop. The cloth may be any of the standard brands which are on
the market, preferably in a rather light weight made specially for
double-surfaced machines of this type; or light-weight sail cloth may be
used, costing only 25 or 30 cents a yard. About 80 yards will be
required, assuming a width of 36 inches.
[Illustration: Fig. 34. Method of Mounting Fabric on Main Supporting
Frame]
Except on the rudder, the cloth is applied on the bias, the idea being
that with this arrangement the threads act like diagonal truss wires,
thus strengthening and bracing the framework. When the cloth is to be
put on in this way it must first be sewed together in sheets large
enough to cover the entire plane. Each wing will require a sheet about
14 feet square, and two sheets each 6 feet square will be required for
the elevators and tail. The strips of cloth run diagonally across the
sheets, the longest strips in the wing sheets being 20 feet long.
Application of the cloth to the wings, Fig. 34, is best begun by
fastening one edge of a sheet to the rear edge of the wing, stretching
the cloth as tight as can be done conveniently with one hand. The cloth
is then spread forward over the upper surface of the wing and is made
fast along the inner end rib. Small copper tacks are used, spaced 2
inches apart on the upper side and 1 inch on the lower side. After the
cloth has been tacked to the upper sides of all the ribs, the wing is
turned over and the cloth stretched over the lower side. Finally the raw
edges are trimmed off and covered with light tape glued down, tape also
being glued over all the rows of tacks along the ribs, making a neat
finish and at the same time preventing the cloth from tearing off over
the tack heads.
*Installation of Motor*. As stated previously, the ideal motor for a
Bleriot-type machine is short along the crank shaft, as the available
space in the fuselage is limited, and air-cooled for the same reason.
Genuine Bleriots are always fitted with one of the special types of
radial or rotary aeronautic motors, which are always air-cooled. Next in
popularity to these is the two-cylinder, horizontal-opposed motor,
either air- or water-cooled. However, successful machines have been
built with standard automobile-type, four-cylinder, water-cooled motors,
and with four-cylinder, two-cycle, aeronautic motors.
When the motor is water-cooled, there will inevitably be some difficulty
in finding room for a radiator of sufficient size. One scheme is to use
twin radiators, one on each side of the fuselage, inside of the main
frame of the running gear. Another plan is to place the radiator
underneath the fuselage, using a supplementary water tank above the
cylinders to facilitate circulation. These two seem to be about the only
practicable arrangements, as behind the motor the radiator would not get
enough air, and above it would obstruct the view of the operator.
It is impossible to generalize to much effect about the method of
supporting the motor in the fuselage, as this must differ with the
motor. Automobile-type motors will be carried on two heavy ash beams,
braced by lengths of steel tubing of about 1 inch diameter and 16 gauge.
When the seven-cylinder rotary Gnome motor is used, the crank shaft
alone is supported; it is carried at the center of two X-shaped frames
of pressed steel, one in front of and the other behind the motor. The
three-cylinder Anzani motors are carried on four lengths of channel
steel bent to fit around the upper and lower portions of the crank case,
which is of the motorcycle type.
Considerable care should be taken to prevent the exhaust from blowing
back into the operator’s face as this sometimes carries with it drops of
burning oil, besides disagreeable smoke and fumes. The usual plan is to
arrange a sloping dashboard of sheet aluminum so as to deflect the gases
down under the fuselage.
The three sections of the fuselage back of the engine section are
usually covered on the sides and bottom with cloth like that used on the
wings. Sometimes sheet aluminum is used to cover the section between the
wing beams. However, those who are just learning to operate machines and
are a little doubtful about their landings often leave off the covering
in order to be able to see the ground immediately beneath their front
wheels.
[Illustration: Fig. 35. Running Gear of Morane Type of Bleriot
Monoplane]
*New Features*. _Morane Landing Gear_. Although the regular Bleriot
landing gear already described, has many advantages and ha.s been in use
with only detail changes for several years, some aviators prefer the
landing gear of the new Morane monoplane, which in other respects
closely resembles the Bleriot. This gear, Fig. 35, is an adaptation of
that long in use on the Henri Farman and Sommer biplanes, combining
skids and wheels with rubber-band springs. In case a wheel or spring
breaks, whether due to a defect or to a rough landing, the skids often
save an upset. Besides, the tension of the springs is usually such that
on a rough landing the wheels jump up and allow the skids to take the
shock; this also prevents the excessive rebound of the Bleriot springs
under similar conditions.
Another advantage which may have some weight with the amateur builder,
is that the Morane running gear is much cheaper and easier to construct.
Instead of the two heavy tubes, the four forks of oval tubing, and the
many slides, collars, and blocks—most of them special forgings or
castings—the Morane gear simply requires two short laminated skids, four
ash struts, and some sheet steel.
The laminated skids are built up of three boards each of 5/8 by 2-inch
ash, 3 1/2 feet long. These must be glued under heavy pressure in forms
giving the proper curve at the front end. When they are taken from the
press, three or four 1/2-inch holes should be bored at equal distances
along the center line and wood pins driven in; these help in retaining
the curve. The finished size of the skids should be 1 3/4 by 1 3/4
inches.
Four ash struts 1 1/4 by 2 1/2 inches support the fuselage. They are
rounded off to an oval shape except at the ends, where they are attached
to the skids and the fuselage beams with clamps of 1/16 inch sheet
steel. The ends of the struts must be beveled off carefully to make a
good fit; they spread out 15 degrees from the vertical, and the rear
pair have a backward slant of 30 degrees from vertical.
Additional fuselage struts must be provided at the front end of the
fuselage to take the place of the struts and beams of the Bleriot
running gear. The two vertical struts at the extreme front end may be of
the same 1 1/4- by 2 1/2-inch ash used in the running gear, planed down
to 1 3/16 inches thick to match the thickness of the fuselage beams. The
horizontal struts should be 1 3/16 by 1 3/4 inches.
The wheels run on the ends of an axle tube, and usually have plain
bearings. The standard size bore of the hub is 15/16 inch, and the axle
tube should be 15/16 inch diameter by 11 gauge. The tube also has
loosely mounted on it two spools to carry the rubber band springs. These
are made of 2 1/4-inch lengths of 1 3/8-inch tubing, with walls of
sufficient thickness to make an easy sliding fit on the axle tube. To
the ends of each length of tube are brazed 2 1/2-inch washers of 3/16
inch steel, completing the spool.
The ends of the rubber bands are carried on rollers of 3/4-inch,
16-gauge tubing, fastened to the skids by fittings bent up from
3/16-inch sheet steel. Each fitting is bolted to the skid with two
3/8-inch bolts.
Some arrangement must now be made to keep the axle centered under the
machine, as the rubber bands will not take any sidewise strain. A clamp
of heavy sheet steel should be made to fit over the axle at its center,
and from this heavy wires or cables run to the bottom ends of the
forward struts. These wires may be provided with stiff coil springs, if
it is desired to allow a little sidewise movement.
[Illustration: Fig. 36. Details of Bleriot Inverse Curve Tail]
_New Bleriot Inverse Curve Tail_. Some of the latest Bleriot machines
have a new tall which seems to add considerable to their speed. It
consists of a fixed tail, Fig. 36, nearly as large as the old-style tail
and elevators combined, with two elevator flaps hinged to its rear edge.
The peculiarity of these elevators, from which the tail gets its name,
is that the curve is concave above and convex below—at first glance
seeming to have been attached upside down. In this construction, the
1-inch, 20-gauge tube, which formerly passed through the center of the
tail, now runs along the rear edge, being held on by strips of 1/2- by
1/16-inch steel bent into *U*-shape and fastened with screws or bolts to
the ribs. Similar strips attach the elevators to the tube, but these
strips are bolted to the tube. The construction is otherwise like that
previously described. It is said that fitting this tail to a Bleriot in
place of the old-style tail adds 5 miles an hour to the speed, without
any other changes being made.
Another slight change which distinguishes the newer Bleriots is in the
overhead frame, which now consists of a single inverted *V* instead of
two *V*’s connected by a horizontal tube. The single *V* is set slightly
back of the main wing beam, and is higher and, of course, of heavier
tubing than in the previous construction. Its top should stand 2 feet 6
inches above the fuselage, and the tubing should be 1 inch 18 gauge. It
also requires four truss wires, two running to the front end of the
fuselage and two to the struts to which the rear wing beams are
attached. All of the wires on the upper side of the wings converge to
one point at the top of this *V*, the wires from the wing beams, of
course, passing over pulleys.
These variations from the form already described may be of interest to
those who wish to have their machines up-to-date in every detail, but
they are by no means essential. Hundreds of the old-style Bleriots are
flying every day and giving perfect satisfaction.
ART OF FLYING
Knowledge of the science of aeronautics and ability to fly are two
totally different things. Long-continued study of the problem from its
scientific side enabled the Wright Brothers to learn how to build a
machine that would fly, but it did not teach them how to fly with it.
That came as the result of persistent attempts at flying itself. A study
of the theoretic laws of balancing does not form a good foundation for
learning how to ride a bicycle—practice with the actual machine is the
only road to success. The best evidence of this is to be found in the
fact that several of the most successful aviators today have but a
slight knowledge of the science of aeronautics. They are not
particularly well versed in what makes flight possible, but they know
how to fly because they have learned it in actual practice.
Reference to the early work of the Wright Brothers shows that during a
period of several years they spent a large part of their time in actual
experiments in the air, and it was not until these had proved entirely
satisfactory that they attempted to build a power-driven machine.
*Methods Used in Aviation Schools*. Aviation schools are springing up
all over this country and there are a number of well-established
institutions of this kind abroad. In the course of instruction, the
student must first learn the use of the various controls on a dummy
machine. In the case of an English school, this dummy, Fig. 37, is a
motorless aeroplane mounted on a universally-jointed support so as to
swing about a pivot as desired. This is employed for the purpose of
familiarizing the beginner with the means of maintaining equilibrium in
the air.
[Illustration: Fig. 37. Monoplane Dummy Used for Practice in Aviation
School]
[Illustration: Fig. 38. Aerocycle with Treadle Power for Practice Work]
A French school, on the other hand, employs a wingless machine, which is
otherwise complete, as it consists of a regulation chassis with motor
and propeller, all steering and elevating controls. On this, the student
may practice what has come to be familiarly known as "grass-cutting," to
his heart’s content, without any danger of the machine taking to the air
unexpectedly, as has frequently been the case where first attempts have
been made on a full-fledged machine. Usually, most of such attempts
result disastrously, often destroying in a moment the result of months
of work in building the machine.
[Illustration: Fig. 39. Voisin Biplane with Double Control for Teaching
Beginners]
A French aerocycle, Fig. 38, a comparatively inexpensive machine, is
also useful for practice in balancing and in short, low flights. The
French apparatus in question may accordingly be considered an advance,
not only over the English machine, even of the type shown in Fig. 39,
which has a double control, and is especially designed for the teaching
of beginners, but very much over the practice of attempting to actually
fly for the first time in a strange machine, as it provides the
necessary practice in the handling of the motor and the lateral
steering. The machine can make high speed over the ground, but is
perfectly safe for the beginner, as it is incapable of rising. Having
gone through the stages represented by either of these contrivances, the
best course for the learner to follow is to try gliding, taking short
glides to attain the ability to quickly meet varying conditions of the
atmosphere.
The fact that these glides are of extremely short duration at first need
not be discouraging when it is recalled that, after several years of
work, the Wright Brothers considered that great progress had been made
when, in 1902, they were able to make glides of 26 seconds. During six
days of the practice season of that year, they made 375 gliding flights
of various distances, most of them comparatively short, but each one of
value in familiarizing the glider with the conditions to be met. It is
not material whether gliding or manipulation of the control levers is
taken up first, as both should be mastered as far as possible before
attempting to fly a regular machine.
*Use of the Elevating Plane*. So many things are necessary to the
control of an aeroplane that thinking becomes entirely too slow a
process—the aviator must be endowed with something approaching the
instinct of the bird; he must be so familiar with his machine and its
peculiarities that a large part of the work of controlling it is the
result of subconscious movement. The control levers of many machines are
so arranged that this subconscious movement on the part of the aviator
directly operates the balancing mechanism. There is no time to think.
When a machine rises from the ground, facing the wind as it should, its
path of flight should be a gradual upward inclination, this being
something difficult to accomplish at first, owing to the sensitiveness
of the elevating rudder, the tendency almost invariably being to give
the latter too great an angle of incidence. At this stage, the maximum
velocity of flight has not yet been attained and care must be taken to
keep the angle of ascent small. Otherwise, the power of the engine,
which may not have reached its maximum, would not be sufficient to cause
the machine to ascend an inclined path at the starting speed. If the
speed of flight be reduced by the increased resistance at this point,
the whole machine will slide back in the air, and if a sudden gust of
wind happens to coincide with the attempt to rise at too great an angle,
there is danger of it being blown over backward.
Where the machine is just leaving the ground and the elevator has been
set at an excessive angle, the rear end of the skids or the tail may
slap the ground hard and break off, or they will impose so much
resistance upon its movement by scraping over the turf that the machine
can not attain its soaring speed. It must be borne in mind, of course,
that remarks such as the present can be only of the most general nature,
every type of machine having its own peculiarities—in some instances,
the extreme opposite of those characterizing similar machines. For
example, in the Voisin 1910 type, the very large and powerful light tail
tends to lift before the main planes, and if this be not counteracted,
the whole machine may turn up on its end. In order to offset this
tendency, the elevator must be raised so as to keep sufficient pressure
beneath it; the moment of this pressure about the center of gravity must
be at least equal to the pressure under the tail planes about the center
of gravity of the machine, or the tail will rise unduly in the air. At
least that is the theory of it—naturally, only practice with that
particular machine would suffice to enable an aviator to familiarize
himself with that particular peculiarity. Again, some machines are "tail
heavy." But there is great difficulty in even approximating the degree
of relative motion, for which reason it has been suggested, under
"Accidents and Their Lessons," that a gradometer, or small spirit level,
in plain sight of the aviator, should form part of the equipment of
every machine. The Wrights long ago adopted the expedient of attaching a
strip of ribbon to the elevator to provide an indication of motion
relative to the wind.
*Aeroplane in Flight*. The sensation of motion after the machine leaves
the ground is almost imperceptible, and it is likewise extremely
difficult to tell at just what moment the aeroplane ceases running on
the solid ground and takes to the air. There is a feeling of
exhilaration but very little of motion. Whereas 40 miles an hour over
the ground, particularly in an automobile, brings with it a lively
appreciation of the speed of travel, the same speed in an aeroplane is a
very gentle motion when high above the ground. If there be no objects
close at hand, with which to compare the speed, the sense of motion is
almost entirely lost.
*Center of Gravity*. The static balance of a machine should be carefully
tried before commencing to fly, and particularly that of a biplane of
the Wright type, in which the aviator sits behind the engine. When
provision is made for carrying a passenger, his seat is placed in the
center line of the machine, so that his presence or absence does not
materially affect the question of lateral balance. As men are not all of
the same weight, in cases in which the aviator only partly balances the
engine about the center line, his weight being insufficient for the
purpose, extra weights should be placed on the wing tip at the lightest
end until the true balance is secured, otherwise a permanent warping, or
_gauchissement_ as the French term it, is required at this side in order
to keep the machine on an even keel. In other words, the machine will
carry what sailors term a port helm where the left side of the machine
is lighter than the right, and _vice versa_, and it will be necessary to
keep the rudder over to that side slightly during the entire flight to
counteract this tendency.
In aeroplanes fitted with tails, the center of gravity is usually in the
vicinity of the trailing edge of the main planes and, of course, should
be on the center line of the machine. The center of gravity of the
aviator on a monoplane should approximately coincide with that of the
machine. If this be not the case, the stabilizers or the elevator must
be permanently set to produce longitudinal balance. Much downward set,
or the increase of the angle of incidence of the tail, will create undue
resistance to flight and should be avoided when possible by bringing the
weight farther forward. The center of pressure should coincide with the
center of gravity, and balance will result.
Before even ground work is attempted, the position of the center of
gravity should be determined in the manner shown in Fig. 40, the
approximate location for four types of machines being shown. At what
point the machine must be suspended, so that it can tip only frontward
and backward and be evenly balanced, is a question that must be answered
in order to ascertain the probability of the machine’s pitching forward
whenever mud, grass, or rough ground is encountered in alighting. If the
center of gravity should lie in front of the axles of the ground wheels
in a machine of the Farman type, trouble is sure to follow. Always
consider the relation of the center of gravity to the wheels, in order
that you may gain some idea of the distribution of the weight on the
running gear when the machine is tipped forward 10 degrees. If the
wheels are not forward far enough there will be trouble in running on
the ground. The elevators must correct whatever variance there may be
from the correct center of gravity and position of the wheels, and the
manipulation of the elevators for that purpose requires skill. If the
tail be very heavy, the elevator may not be able to counteract that
defect.
[Illustration: Fig. 40. Method of Determining Center of Gravity of
Different Types of Machines]
The position of the center of gravity of a machine in regard to lateral
stability in flight is a matter of far greater importance than untried
aviators realize. Having it too low is quite as bad as too high, as in
either case there is a tendency to upset. Although the dihedral angle is
considered wasteful of power, it seems to do more to secure inherent
stability than any other device. Devices for maintaining stability
automatically are to be frowned upon in the present state of the art.
The sensitive perception and quick response which come with intimate
knowledge of a machine’s peculiarities, are at present worth more than
gyroscopes and pendulums. To acquire this intimate knowledge, the
aviator must familiarize himself thoroughly with the machine; he must
become so accustomed to controls that he and the machine are literally
one. A practiced bicycle rider does not have to think about balance,
neither does the practiced aviator, yet he must always be prepared to
meet motor stoppages, unusual air disturbances, and breakages. A leap
from the ground directly into the air, without preliminary practice,
means certain accident, to put it mildly.
*Center of Pressure*. But although the center of gravity remains
approximately constant, the center of pressure is continually varying
and is never constant for many seconds. The center of pressure on an
aerocurve constructed to Phillips’ design, Fig. 41, is about one-third
of the chord from the leading edge of the plane under normal conditions,
_i.e._, when the angle of incidence is about 8 degrees between the
direction of motion of the plane and that of the air. At the moment this
angle is increased the center of pressure moves toward the rear, and
_vice versa_. The center of gravity must be moved to coincide with this
new position, or the center of pressure must be artificially restored by
the use of supplementary planes or elevators, moving in a contrary
direction. A forward movement of the center of pressure tends to lower
the tail of the machine, when the intensity of the pressure is
unchanged, and to counterbalance this the rear elevator must have its
angle of incidence increased in order to increase the lift at the rear
of the machine, or it will slide down backward. The alternative to be
adopted in case of temporary lack of engine power is to decrease the
angle of the elevator and allow the aeroplane to sweep downward, thus
gaining momentum. The increase of speed will then be sufficient probably
to enable the machine to continue in a horizontal flight, when the
center of pressure is again restored to its normal position.
[Illustration: Fig. 41. Aerocurve of Phillip’s Design]
*Ground Practice*. First of all, the aviator should familiarize himself
with his seat for it is from that place that he must judge wind effects,
vibration, motor trouble, and the thousand and one little creaks and
hums that will ultimately mean so much to him. Not until he has
thoroughly accustomed himself to his seat, should he try to run along
the ground. This done, hours should be spent running up and down and
around the field to learn the use of the rudder, particularly on rough
ground. The runs should be straight so that when the time comes to leap
into the air, the aviator may be sure that he is on an even keel, and
flying straightaway. In order to prevent the possibility of leaving the
ground unexpectedly in practice, trials should be made only in calm
weather and with the motor well throttled down so that the machine will
be reduced to a speed of not more than 15 miles per hour. After a time
this may be increased to 20, but the latter is the maximum for ground
practice, as the machine will rise at speeds slightly exceeding this. In
these practice rims on the ground, the student should learn to gauge the
rush of air against his face, as when aloft his best gauge will be the
wind pressure on his cheeks, as that will tell him whether he is moving
with sufficient speed to keep up or not. It will also tell him
ultimately whether he is moving along the ground fast enough to leap up.
[Illustration: VEDRINES, ONE OF THE MOST FAMOUS AND SUCCESSFUL OF
EUROPEAN AEROPLANE PILOTS, SEATED
IN A DEPERDUSSIN MONOPLANE]
[Illustration: AIRSHIP CROSSING ONE OF THE NATIONAL ROADS IN RURAL
FRANCE
_This Photograph Protected by International Copyright_]
In this stage of experimenting on the ground, the elevator is kept
neutral as far as possible. With increasing skill its use may be
ventured, but only sparingly, for it takes very little to lift the
machine from the ground with a speed in excess of 20 miles per hour. It
will soon be discovered that the elevator can be used as a brake to
prevent pitching forward. The tail elevators on the Farman or Bleriot
running gear are very effective owing to the blast of the propeller,
even when the main planes are not moving forward at lifting speed. With
the Curtiss type of running gear and a front elevator only, it is often
possible at 18 to 20 miles per hour to raise the front wheel off the
ground for a second or two—facts which indicate that at 25 to 28 miles
per hour, the elevator is far more effective.
*First Flight*. The first actual flight should be confined to a short
trip parallel to the ground and not more than one or two feet above it.
At first, the student should see how close he can fly to the ground
without actually touching it, which he can do by gradually increasing
his forward speed. This must be done in an absolute calm as an
appreciable amount of wind will bring in too many other factors for the
student to master at so early a stage. This practice should be continued
in calm air until short, straight flights can be made a foot or two from
the ground with the motor wide open. If it be found that the machine
barely flies straightaway with the full power of the motor, the latter
is either badly out of adjustment, or a more powerful engine is
required. In an under-powered machine turning would be suicidal.
Moreover, the resistance encountered in the air is greater than on the
ground and may be such that the speed is not sufficient for
sustentation. Fig. 42, (a) and (b), show why it is possible to run along
the ground faster than it is possible to travel in the air, under
certain conditions, and why the ground can be left at low speed. If it
were possible to drive a machine with such enormous projected areas as
_BB_, shown in Fig. 42 (b), a man could fly slowly for an indefinite
period. But the projected area is greater than the air displaced by the
propeller, and it is impossible to fly except with a moderate angle of
incidence, giving projected areas _A A_, Fig. 42 (a). The student, as he
increases in skill, may venture to a height of 10 feet, which should be
maintained as accurately as before, and after making a run of 100 yards,
the machine should be pointed down, but ever so slightly. The wind
pressure on the face immediately becomes greater. Within a foot or two
of the ground the motor should be cut off or throttled. This should be
tried ten or fifteen times, and the height increased to 30 or 40 feet,
in order that the student may familiarize himself with the sensation of
coasting. At the end of each glide the machine will seem to become more
responsive, as indeed it does, for gliding down greatly increases the
efficiency of the elevator and other controls, because of the increased
speed. Gliding down steep angles is often the aviator’s salvation in a
tight place, particularly when the motor fails, a side gust threatens or
an air pocket is encountered.
[Illustration: Fig. 42. Diagrams Showing Greater Projected Area of Main
Plane when
Running along Ground]
*Warping the Wings*. When sufficient confidence has been attained at a
height of 30 to 40 feet, the ailerons or warping devices may be tried
judiciously. Here the intention should be to correct any tendency to
side tipping, and not purposely to incline the machine as far as
possible without actually causing a wreck. The use of the lateral
control may cause the machine to swerve a little, but that may be
ignored. Before landing, a straight course should be taken so that the
machine will always come down on an even keel. With increasing practice,
the student may fly higher, but always with the understanding that there
is a limit to the angle of incidence. An automobile is retarded when it
strikes a short, steep hill; so is an aeroplane. No aeroplane has yet
been built that can take a steep angle and climb right up that grade
continuously. Altitude is reached by a series of small steps and at
comparatively low angles, as unless the course is straightened out at
regular intervals, a machine will lose its speed and tend to plunge tail
first, just as is the case when an attempt is made to rise from the
ground at too sharp an angle.
In warping the wings an increase of lift imparted to one wing of the
machine is produced by increasing the angle of incidence of the whole or
part of the wing, or by an increase of pressure under that wing, and
will tend to cause that side of the machine to rise and the other side
to lower, the result being that the machine will be liable to slide
through the air diagonally. In the majority of aeroplanes there are no
fins or keels to counteract this movement, and lateral stability must be
restored by artificially increasing the lift of the depressed wing. This
can be done by warping, or lowering the trailing edge of the depressed
wing and increasing its lift, and simultaneously raising the trailing
edge of the other wing, thus decreasing the angle of incidence of the
latter and reducing its lifting effect. This applies to flight on a
straight course, whatever the cause may be that tends to upset lateral
stability. It will be seen, therefore, that the center of gravity
remains constant and the center of pressure must be manipulated to
restore stability. This manipulation is much more rapid and positive
than the alteration of the center of gravity by the movement of the
aviator’s body resorted to in the early gliding flights of pioneer
experimenters.
*Making a Turn*. The first turn should be made over a large field and
the diameter of the turn should be at least half a mile. The height
should be not less than 50 feet. After that level has been maintained,
the rudder should be moved very gingerly. The machine will lean in
almost immediately, because the outer end travels at a higher speed than
the inner and therefore has a greater lift. Warping or working the
ailerons should be resorted to as a means of counteracting this
tendency, and the rudder swung to the opposite direction, if necessary.
It is obvious that if the rudder will cause the machine to bank when
swung in one direction, it will right the machine again when swung in
the opposite direction. It is even possible to turn the machine on an
even keel by anticipating the banking, simply by correctly using the
rudder, which was necessary in the old Voisin machine flown by Farman in
1908, because it had no mechanical lateral control. The student should
learn the correct angle of banking, _i.e._ the angle at which the
machine will neither skid nor slide down and which is most economical of
power because it requires less use of the lateral controls. The
necessity of "feeling the air" is greater in turning than in any other
phase of flying. By "feeling the air" is meant the ability to meet any
contingency intuitively and not until this is acquired can the student
become an expert aviator. When it has been acquired, safe flying is
assured and is dependent only upon the integrity of the planes, motor,
and controls. By using the rudder discreetly and by banking simply far
enough to partially offset the centrifugal force of turning, the use of
the lateral control will not be necessary in still air. Even too short a
turn can be corrected by a quick use of the rudder.
The peculiarities existing between different types of monoplanes become
even more marked than between the biplane and the monoplane. For
example, in piloting a Bleriot monoplane, Fig. 43, it is necessary to
take into account the effect of the engine torque. As the engine rotates
in a right-hand direction, from the point of view of the pilot, the left
wing tends to rise in the air, owing to the depression of the right side
of the machine. The machine also tends to turn to the right, and this
must be counteracted by putting the rudder over to the left. An
aeroplane answers its controls with comparative slowness, with the
exception, perhaps, of the Wright machine, which is noted for its
sensitive and quick response to every movement of the levers. All
control movements must, therefore, be very gentle, as the behavior of an
aeroplane is more like that of a boat than that of an automobile. The
action of the elevator has already been described, and it is, perhaps,
the most difficult of all the controls to manipulate, in that it
requires the exercise of a new sense. The direction rudder is naturally
a more familiar type of control, and in action is similar to the rudder
of a boat.
The torque of the motor renders it advisable for a novice to turn his
machine to the right, if a right-hand propeller be used, and _vice
versa_. If two propellers, turning in opposite directions, are employed,
as in the Wright biplane, there is no inequality from the torque of the
motor. Since torque is not noticeable in straight flying, straightening
out again will always serve the student when he finds himself in trouble
on a turn. When the use of the rudders and ailerons has reduced the
speed, a downward glide will increase it again, and if the motor should
stop on a turn, such a downward glide is immediately imperative. When
the machine is thus gliding, a change in the fore-and-aft balance
becomes at once apparent, because the blast of the propeller no longer
acts on the tail, and the elevator must then be used with greater
amplitude to obtain the same effect.
[Illustration: Fig. 43. Making a Start with Bleriot Monoplane]
Only by constant practice in calm air can the student familiarize
himself with exactly the amount of warping and rudder control to employ
to property offset the lowering of the inner wing in rounding a turn. If
this be not corrected, the whole machine tends to bank excessively and
will be apt to slide downward in a diagonal direction, Fig. 44. This is
a perilous position for the aviator and must be guarded against by the
manipulation of the warping control so as to increase the lift of the
inner wing of a biplane, at the same time, employing the rudder to
counteract this tendency. The use of the rudder is of even greater
importance on the monoplane, as, in this case, warping the inner wing
tends to direct the whole machine downward instead of raising the inner
wing itself. Several bad accidents have resulted from monoplanes
refusing to respond to the warping of the inner wing when making a turn.
In such machines, the rudder must be practically always employed in
connection with the warping of the wings in order to keep the machine on
an even keel, although the controls may not actually be interconnected,
this being one of the grounds on which foreign manufacturers are trying
to make use of the Wright principle, without infringing the Wright
patents, as while they employ warping in connection with the
simultaneous use of the rudder, the controls are not attached to the
same lever as in the Wright machine.
[Illustration: Fig. 44. An Aeroplane "Banking" as it Rounds a Pylon]
Lateral resistance must also be taken into consideration in turning,
otherwise the machine, if kept on an even keel, will tend to skid
through the air and turn about its center of gravity as a pivot. In the
case of an automobile, the resistance to lateral displacement is great,
though on a greasy surface it may be small, as when the machine skids
sideways, a suitable banking of the road being necessary to prevent this
on turns. Many hold that the banking of the aeroplane on turns is only
the direct effect of the turning itself, but the fallacy of this will be
apparent upon a consideration of the law of centrifugal force. It is
obvious that to make a turn, some force must be imparted to the machine
to counteract the effect of the centrifugal force upon the machine as a
whole. And as the sidewise projection of the machine is small, a
compensating force must be introduced. This can be done only by
previously banking up the machine on the outer wing, so that the
pressure of the air under the main plane can counteract the tendency to
lateral displacement. The force then acting under the planes is in a
diagonal direction, and the angle at which it is inclined vertically
depends upon the banking of the planes, it being normal to their greater
dimension. This force can be resolved into two forces, one perpendicular
and one horizontal, the magnitude of each being dependent upon the
degree of banking. When the speed of the machine is higher, the amount
of banking must be greater in order to increase the value of the
horizontal component in proportion to the increase of the value of the
centrifugal force at the higher speed, in spite of the fact that the
forces acting under the planes are also greater due to the higher speed.
As the curve commences, the rudder being put over, the difference of the
pressures on the two wings, owing to their different flying speeds comes
into account, as already explained, and care must be taken that the
banking does not increase abnormally. When the turn is completed, the
rudder is straightened and the machine is again brought to an even keel
with the aid of the wing-warping control, or the ailerons. The effect of
a reverse warping to prevent excessive banking, lowering the inside wing
tip incidentally, puts a slight drag on that wing and assists in the
action of turning, as does also the provision of small vertical planes
between the elevator planes of the original Wright machine. Since the
adoption of the headless type, these surfaces are placed between the
forward ends of the skids and the braces leading down to them.
In making a turn, say, to the left, the outside or right-hand wing is
first raised by lowering the wing tip on that side and the rudder is
then put over to the left. When the correct amount of banking is
acquired, the wing tip is restored to its normal position, and probably
the left wing tip may have to be lowered slightly to increase the lift
on that side owing to its reduced speed. When the turn is completed, the
rudder is straightened out and the left wing tip lowered to restore the
machine to an even keel. Both Glenn Curtiss in this country and R. E.
Pelterie in France have shown that it is possible to maneuver without
using the rudder at all, the ailerons or wing tips alone being relied
upon for this purpose.
Before flights in other than calm air are attempted, much practice is
required. The machine must be inspected over and over again, and the
wind variations studied with a watchful eye. Not until this familiarity
with machine and atmosphere be acquired should flying in a wind be
attempted. To the man on the ground, wind is simply air moving
horizontally, but to the man in the air it is quite different. Not only
must he consider horizontal movement, but vertical draughts and vortices
as well. A rising current of air lifts a machine, a downward current
depresses it, and he must learn to take advantage of the former as the
birds do. Horizontal currents affect forward speed over the ground;
swirls and vortices create inequalities in wind pressure on the planes
and disturb lateral balance. Familiarity with all these atmospheric
conditions can be acquired only after long practice. Against every tree,
house, hill, fence, and hedge beats an invisible surf of air; upward
currents on one side and downward on the other. The upward draught is
not usually dangerous, for it simply lifts the machine; but the down
draught will cause it to drop. A swift downward glide under the full
power of the motor must then be made, to increase the forward speed and
consequently the lift. This explains why it is dangerous to fly near the
ground in a wind; likewise why the beginner should never attempt flying
at first in anything but a dead calm.
_Turning in a Wind_. When turning in a wind, two velocities must be
borne in mind, that of the machine relative to the air and that relative
to the earth. The former is limited at its lower value to that of the
flying speed of the machine, and the latter must be considered on
account of the momentum of the machine as a whole. Change of momentum is
a matter of horse-power and weight and is the governing factor in flying
in a wind on a circular course. Suppose the flying speed of a machine is
a minimum of 30 miles an hour relative to the air, and a wind of 20
miles an hour is blowing. The actual speed of the machine relative to
the earth in flying against the wind will be 10 miles an hour. If it be
desired to turn down the wind, the speed of the machine relative to the
earth must be increased from 10 miles to 50 miles an hour during the
turn and a corresponding change of momentum must be overcome. There are
two ways of accomplishing this, either by speeding up the motor to give
the maximum power, or by rising just previous to making the turn and
then sweeping down as the turn is made, thus utilizing the acceleration
due to gravity to assist the motor. The wind’s velocity will assist the
machine also and during the turn it will make considerable leeway, a
small amount of which is deducted to counteract the centrifugal force of
the machine.
Turning in a contrary direction, _i.e._, up into the wind when running
with it, requires considerable skill, as when flying 50 miles an hour,
the tendency on rounding a corner into a 20-mile-an-hour wind would be
for the machine to rise rapidly in the air. The centrifugal force at
such a speed is also considerable, causing the machine to make much
leeway with the wind during the turn. Turning under such circumstances
should be commenced early, particularly if there are any obstructions in
the vicinity, and considerable skill should be acquired before an
attempt is made to fly in such a wind.
*Starting and Landing*. A machine should always be started and landed in
the teeth of the wind, and no one but the most experienced aviators can
afford to disregard this advice, certainly not the novice. The
precaution is necessary because in landing the machine should always
travel straight ahead without the possibility of lurching and
consequently breaking a wing, as frequently happens. Contact with the
ground is necessarily made at a time when the machine is traveling over
it at a speed of 30 to 40 miles per hour and skidding sideways at 10 to
15 miles per hour, all circumstances which tend to wreck an aeroplane.
*Planning a Flight*. It is easy to lose one’s way in the air. For that
reason it is best to follow the Wright idea of starting out with a
definite plan, and of landing in some predetermined spot, as aimless
wandering about may prove disastrous to the inexperienced aviator, he
may forget which way the wind was blowing, or how much fuel he had, or
the character of the ground beneath him. Should the motor stop, he may
make an all too hasty decision in landing. It is an easy matter to lose
one’s bearings in the air, not only because the vehicle is completely
immersed in the medium in which it is traveling, but also because the
earth assumes a new aspect from the seat of an aeroplane. Cecil Grace
was one of those who lost his bearings and, as a consequence, his life.
Ordinary winds blowing over a level country can be negotiated with
comparative safety. Not so the puffy wind. To cope with that, constant
vigilance is required, particularly in turning. In a circular flight in
a steady wind, the only apparent effect is that the earth is swept over
faster in one direction than in the other. Before a cross-country flight
is attempted, the starting field should be circled over at a great
height, as not until then may the long distance flight be started in
safety. Cross-country flying is, of course, fascinating, and it is a
sore temptation, at an altitude of a few hundred feet, to throw off all
caution and fly off over that strange country below, which is, indeed, a
new land as viewed from aloft. To quote a professional aviator: "Here
the greatest self-restraint must be exercised. Not until the necessary
practice has been acquired, not until the right kind of confidence has
been gained, may one of these trips be attempted, and then only after it
has been properly planned."
*Training the Professional Aviator*. Look back over the achievements in
the air during the comparatively short time that man has actually been
flying, and it will be noted that the beginners, burning up with the
enthusiasm of the novice, have performed the most spectacular feats and
flown with the greatest fearlessness. Curtiss was comparatively new at
aviation when he won the Gordon-Bennett at Rheims in 1909. John B.
Moisant, the sixth time he ever went up in an aeroplane, flew from Paris
to London with a 187-pound passenger and 302 pounds of fuel, oil, and
spare parts. Hamilton made his successful flight from New York to
Philadelphia and return when he was hardly more than a novice, while
Atwood’s great flights from St. Louis to New York and Boston to
Washington were made before his name had become known, and Beachey had
been flying only a few months when he broke the world’s altitude record
at Chicago, while more recent achievements, notably Dixon’s flight
across the Rockies, have emphasized the work of the beginner. All of
this substantiates the belief held at every aviation headquarters in the
country—namely, that the older men already in aviation may improve the
art by executive ability and scientific experiments, but most of them
will degenerate as flyers. Beyond a certain point, frequency of flight
does not necessarily create a feeling of confidence and safety; rather
it brings a fuller appreciation of the dangers, and the men who best
know how to fly are most content to stay upon the ground.
Professional aviators are drawn from every walk of life, but trick
bicycle performers, acrobats, parachute jumpers, and racing automobile
drivers make the most promising applicants. By a kind of sixth sense,
both the Wrights and Curtiss weed out the promising ones after a brief
examination. They select men who have an almost intuitive sense of
balance. Most of these, provided they have nerve, have in them the stuff
of which aviators are made, even though they may have had no experience
in any line akin to aviation. Neither Curtiss nor the Wrights will
accept women under any condition. The Moisant school does not share this
discrimination and trained three women for pilot’s licenses during 1911.
Curtiss and the Wrights are keen in their realization that recklessness
is pulling a wing feather from aviation every time a man is killed, and
they are doing their utmost to promote conservatism. Curtiss said in an
interview:
I do not encourage and never have encouraged fancy flying. I
regard the spectacular gyrations of several aviators I know as
foolhardy and unnecessary. I do not believe that fancy or trick
flying demonstrates anything except an unlimited amount of a
certain kind of nerve and perhaps the possibilities of what is
valueless—aerial acrobatics. Some aviators develop the sense of
balance very rapidly, while others acquire it only after long
practice. It may be developed to a large extent by going up as a
passenger with an experienced man. Therefore, in teaching a
beginner, I make it a point to have him make as many trips as
possible with someone else operating the machine. In this way
the pupil gains confidence, becomes accustomed to the sensation
of flying, and is soon ready for a flight on his own hook. This
is the method used in training army and navy officers to fly. I
have never seen novices more cautious and yet more eager to fly
than these young officers. They have always learned every detail
of their machines before going aloft, and largely because of
this they have developed into great flyers. Perhaps it is due to
the military bent of their minds; at any rate, they have made
good almost without exception.
ACCIDENTS AND THEIR LESSONS
*Press Reports*. Whenever an industry, profession, or what not, is
prominently before the public, every event connected with it is regarded
as "good copy" by the daily press. Happenings of so insignificant a
nature that in any commonplace calling would not be considered worthy of
mention at all, are "played up." This is particularly the case with
fatalities, and the eagerness to cater to the morbid streak in human
nature has been responsible for the unusual amount of attention devoted
to any or all accidents to flying machines, and more especially where
they have a fatal ending. In fact, this has led to the chronicling of
many deaths in the field of aviation that have not happened—some of them
where there was not even an accident of any kind. For instance, in many
of the casualty lists published abroad from time to time, such flyers as
Hamilton, Brookins, and others have figured among those who have been
killed, ever since the date of mishaps that they had months ago.
It will be recalled that five years ago, when the automobile began to
assume a very prominent position, every fatality for which it was
responsible was heralded broadcast where deaths caused by other vehicles
would not be accorded more than local notice. To a large extent, this is
still true and will probably continue to be the case until the
automobile assumes a role in our daily existence as commonplace as the
horse-drawn wagon and trolley car. There is undoubtedly ample
justification for this and particularly for the editorial comment always
accompanying it, where the number of lives sacrificed to what can be
regarded only as criminal recklessness is concerned. Still, the fact
that in a city like New York the truck and the trolley car are
responsible for an annual death roll more than twice as large as that
caused by the automobile, does not call for any particular mention.
Horses and wagons, we have always had with us, and the trolley car long
since became too commonplace an institution around which to build a
sensation.
As the most novel and recent of man’s accomplishments, the conquest of
the air and everything pertaining to it is a subject on which the public
is exceedingly keen for news and nothing appears to be of too trivial
import to merit space. Where an aviator of any prominence is injured, or
succumbs to an accident, the event is accorded an amount of attention
little short of that given the death of some one prominent in official
life. During the four years that aviation has been to the fore, about
104 men and one woman have been killed, not including the deaths of
three or four spectators resulting from accidents to aeroplanes, during
this period—_i.e._, from the beginning of 1908 to the end of 1911. In
view of the lack of corroboration in some cases, the figures are made
thus indefinite. Naturally most of these deaths have occurred in 1910
and 1911—in fact, 50 per cent took place from 1908 to the end of 1910,
and the remainder during 1911, since these years were responsible for a
far greater development, and particularly for a greater increase in the
number engaged, than ever before. More was accomplished in these two
years than in the entire period intervening between that day in
December, 1903, when the Wright Brothers first succeeded in leaving the
ground in a power-driven machine, and the beginning of 1910.
*Fatal Accidents*. Conceding that the maximum number mentioned, 105,
were killed during the four years in question, throughout the world, it
will doubtless come as a surprise to many to learn that this is probably
not quite twice the number who have succumbed to football accidents
during the same time in the United States alone. Authentic statistics
place the number thus killed at 13 during 1908, 23 in 1909, 14 during
1910, and 17 in 1911, or a total of 67. But we have been playing
football for a couple of centuries or more and this is regarded as a
matter of course. The death of a football player occurring in some
small, out-of-the-way place would not receive more than local attention,
unless there were other reasons for giving it prominence, so that, in
all probability, the statistics in question fall far short of the truth,
rather than otherwise.
The object of mentioning this phase of the matter is to place the
question of accidents in its true light. That the development of any new
art is bound to be attended by numerous mishaps, many of them fatal,
goes without saying and it is something that can not be ignored. Nothing
could be worse than attempting to gloss over or belittle the loss of
life for which aviation has been responsible and doubtless will continue
to be. Progress invariably takes its toll and it is more often founded
upon failure than unvarying success, for every accident is a failure, in
a sense, and every accident carries with it its own lesson.
Where the cause is apparent, it gives an indication of the remedy which
will bring about the prevention of its recurrence. In other words, it
serves to point out weaknesses and shows what is necessary to overcome
them. For that reason alone is the question of accidents taken up here,
as a study of those that have occurred points the way to improvement.
Table III gives a resume of the more important fatalities that have
resulted from the use of a heavier-than-air machine during the _past
four years_:
Fatalities greatly increased in number during 1911, but not out of
proportion to the greatly augmented number of aviators. With
comparatively few exceptions, however, the accidents were more or less
similar in their nature to those already tabulated, so that it would be
of no particular value to extend the comparison in this manner to cover
them. Many of the fatalities during that year were not of the aviators
themselves, but of the spectators, a fact which calls attention to a
danger that has not been fully appreciated before. At the start of the
Paris-Madrid race, the French minister of war and another official were
killed by a monoplane plunging into the crowd, and on the same day, May
21, 1911, five people were killed at Odessa, Russia, in the same manner.
An unusual type of mishap, not mentioned in the tabulation and in which
three or four aviators lost their lives during 1911, was the burning of
the aeroplane in midair, or the explosion of the gasoline, setting fire
to the wings and either burning the aviator at his post or killing him
by the fall. One such accident occurred in France in September, another
in Spain two days later, and a third in Germany, in which two men were
killed. Accidents of an even more unusual nature were the collision of
two biplanes in midair at St. Petersburg, the collision of a motorcycle
with a biplane as it swooped down on a race track, and the partial
wrecking of Fowler’s biplane by a bull upon landing near Fort Worth,
Texas, but these, of course, had no bearing on the design of the
machines.
Apart from those specially referred to, the great majority of accidents
during 1911 may be ascribed to two or three of the causes detailed in
connection with the comparative table. Of these, lack of experience and
foolhardiness stand out prominently, the latter undoubtedly causing the
double fatality at Chicago when two aeroplanes plunged into Lake
Michigan, drowning one of the aviators, while a third machine collapsed
in mid-air, hurling the aviator to his death on the field. Careful
reading of the reports of a large number of these accidents usually
brings to light the statement "in attempting to make a quick turn," or
similar phrase, showing that the moving cause of the accident was due to
subjecting the parts of the machine to excessive stresses, as outlined
in the following pages.
*Causes*. _Lack of Experience_. It will be at once noticeable by Table
III that out of a total of 28, no less than 16, or considerably more
than half of the accidents, were due in one way or another to lack of
experience. In other words, the aviators had not fully complied with the
cardinal principle for success in flying upon which the Wright Brothers
have always laid so much stress, _i.e._, you must first learn to fly
before you can attempt to go aloft safely. Nothing short of a thorough
mastery of the machine can suffice to give the aviator the ability to do
the right thing at the right moment, in the great majority of cases.
There will always be occasions when even the most skilled aviator will
make errors of judgment and frequently they cost him his life. But this
is equally true of every dangerous calling, whether it be running an
automobile, driving a locomotive, or doing any of the thousand and one
things where the responsibility for his own and other lives is placed in
one man’s hands and depends to a large extent on his discretion and
judgment in cases of emergency, so that there will be fatalities from
this cause as long as man continues to fly. This involves the personal
equation that must always be reckoned with. Just how many of the
accidents that have resulted in the fatalities set forth, have been due
to the fallibility of the operator and for how much the design of the
current types of machines is responsible, would be hard to say. Fig. 45,
for example, which shows H. V. Roe in the act of striking the ground in
his triplane, illustrates an accident due to bad design. Methods of
control will be improved and simplified and made as nearly "fool-proof"
as human ingenuity can accomplish, but experience in other fields has
demonstrated unmistakably that they can never be developed to a point
where it is impossible to do the wrong thing. With skill at such a
premium in callings of responsibility which involve only conditions that
have been familiar for years, how much more so must it be in the air
about which so little is known? Consequently, the real danger is to be
found in the personal equation, just as it is in every other mode of
conveyance, despite the fact that it has been perfected to a point which
apparently admits of little further development where safe-guarding it
is concerned.
[Illustration: Fig. 45. Roe’s Multiplane as it Struck the Ground. An
Accident Due to Poor Design]
[Illustration: Fig. 46. DeLessep’s Machine after Striking an
Obstruction]
[Illustration: Fig. 47. Overturned Monoplane Due to a Start in a Gale]
*Obstructions*. Obstructions are bound to play a prominent part in
accidents to any method of conveyance, but less so in aviation than in
any other, as it is only in rising and alighting that this danger is
present. Of the two fatal accidents ascribed to this cause, one resulted
from colliding with an obstruction while running along the ground
preparatory to rising, and the other from striking an obstruction in
flight, Fig. 46. In view of the numerous cross-country flights that have
been made, trips across cities and the like, it is to be marveled at
that up to the present writing no fatalities have been caused by what
the aviator most dreads when leaving the safety of the open field, that
is, being compelled to make a landing through stoppage of the motor,
whether from a defection or lack of fuel. While no fatalities have as
yet to be put down to this ever-present danger in extended flights, an
accident that might have had a fatal termination, occurred to Le Blanc
during the competition for the Gordon-Bennett trophy, which was the
chief event of the International Meet in October, 1010, at Belmont Park,
near New York. Le Blanc and his fellow compatriots who were eligible
were all experienced cross-country flyers, the former having won the
_Circuit de L’Est_, a race around France, and by far the most ambitious
of its kind which had been attempted up to that time. They accordingly
protested most vigorously against flying over the American course to
compete for the cup which Curtiss had captured at Rheims the year
before, owing to the fact that it presented numerous dangerous
obstructions in the form of trees and telegraph poles. But as it was
impossible to provide any other convenient five-kilometer circuit (3.11
miles) as called for by the conditions, the protest was of no avail.
After having covered 19 of the 20 laps necessary to complete the
distance of 100 kilometers in time that had never been approached
before, Le Blanc was compelled to descend through lack of fuel, and as
he had not risen more than 80 to 100 feet at any time during the race,
this meant coming down the moment the motor stopped. The result was a
collision with a telegraph pole, breaking it off and wrecking the
monoplane, the aviator fortunately escaping any serious injury. During
the same meet Moisant demolished his Bleriot monoplane by trying to
start in the face of a high wind, Figs. 47 and 48.
[Illustration: Fig. 48. View of Moisant Monoplane after a Bad Spill]
*Stopping of Motor*. The mere fact that the motor stops does not
necessarily mean a disastrous ending to a flight, as is very commonly
believed, this having been strikingly illustrated by Brookins’ glide to
earth from an altitude of 5,000 feet with the motor dead, and Moisant’s
glide from an even greater height in France. But it does mean a wreck
unless a suitable landing place can be reached with the limited ability
to control the machine that the aviator has when he can no longer
command its power. Motors will undoubtedly become more and more reliable
as development progresses, but the human equation—the partly-filled fuel
tank, the loose adjustment that is overlooked before starting, and a
hundred and one things of a similar nature—will always play their role,
so that compulsory landing in unsuitable places will always constitute a
source of danger as flights become more and more extended.
*Breakage of Parts of Aeroplanes*. In studying the foregoing table, it
can only be a source of satisfaction to the intelligent student and
believer in aerial navigation, to note how large a proportion of the
accidents is due to the breakage of parts of the machine. This implies a
fault in construction, but not in principle. It reveals the fact that,
in the attempt to secure lightness, strength has sometimes been
sacrificed, chiefly through lack of appreciation of the stresses to
which the machine is subjected in operation. At a time when weight is
regarded almost as the paramount factor by so many builders, it is
inevitable that some should err by shaving things too fine. Lightness is
an absolute necessity and failure to achieve it in every instance
without eliminating the factor of safety has been due more to the crude
methods of construction and lack of suitable materials, than any other
cause—conditions that are bound to obtain in the early days of any art.
Construction is improving rapidly, but progress is bound to be attended
with accidents of this nature. The fact that their proportion is greatly
diminishing despite the rapidly increasing number of aviators is the
best evidence of what is being accomplished. When machines are built
with such a high factor of safety in every part that breakage is an
almost unheard-of thing, failures from this cause will have been reduced
to an unsurpassable minimum.
*Failure of the Control Mechanism*. Under the general classification B,
are included not alone those accidents directly due to breakage of some
vital part, but also those instances in which some element of the
control, such as the elevator, has become inoperative through jamming.
When an accident happens in the air, it takes place so quickly and the
machine is so totally wrecked by falling to the ground, that it is
usually difficult to determine the exact nature of the cause through a
subsequent examination of the parts, so that it can seldom be stated
with certainty just what the initial defection consisted of, though it
may be regarded as a foregone conclusion that, in the case of
experienced aviators who have previously demonstrated their ability to
cope with all ordinary emergencies, nothing short of the failure of some
vital part could have caused their fall.
This was the case with Johnstone’s accident at Denver—an occurrence
illustrating another phase of the personal equation that must be taken
into consideration when noting the lessons to be learned from a study of
accidents and their causes. It is simply the old, old story of
familiarity breeding contempt—the miner thawing out sticks of dynamite
before an open fire. Due to the rarefied air of Denver, which is at an
elevation of more than 5,000 feet, Johnstone had underestimated the
braking powers of the air on the machine in landing the day previous and
had crashed into a fence, breaking one of the right outermost struts
between the supporting planes.
Proper regard for safety should naturally have called for its
replacement by an entirely new strut, but conditions at flying meets as
at present conducted make quick repairs to damaged machines imperative.
The damaged upright was accordingly glued and braced by placing iron
rings around it, the rings themselves being held in place by ordinary
nails passing through holes in the iron large enough to let the nail
head slip through. The vibration of the motor and the straining of the
strut in warping the wings caused the nails to work out of the holes,
permitting the rings to slide out of place as well. Johnstone was an
accomplished aviator, much given to the execution of aerial maneuvers
only possible to the skilled flyer of quick and ready judgment. But such
performances impose excessive stresses on the supporting planes and
their braces, and one of Johnstone’s quick turns caused the repaired
struts to collapse through the strain of sharply warping the wing tips
on that side. He immediately attempted to restore the balance of the
machine by bringing the left wing down with the control, then tried to
force the twisting on the right side, succeeding momentarily, and a few
seconds later losing all control and crashing to the ground. It appeared
to demonstrate that even when disabled an aeroplane is not entirely
without support, but has more or less buoyancy—something which is really
more of an optical illusion than anything else due to underestimating
the speed at which a body falls from any great height. Johnstone’s
accident was the first of its kind, in that he fell from a height of
about 800 feet, during the first 500 of which he struggled to regain
control of the machine, finally dropping the remaining 300 feet
apparently as so much dead weight. It showed in a most striking manner
the vital importance of the struts connecting the supporting surfaces of
the biplane, any damage to them resulting in the crippling of the
balancing devices and the end of all aerial support.
*Biplane vs. Monoplane*. It requires only a glance at Table III to show
that the greater number of accidents have happened to the biplane, yet
the latter is generally regarded as the safer of the two. Prior to
Delagrange’s fatal fall in January, 1910, there had been only four
fatalities with modern flying machines: Selfridge and Lefebre were
killed in Wright machines, the latter of French manufacture, Ferber lost
control of his Voisin biplane, and Fernandez was killed flying a biplane
of his own design. In one case at least, that of Lieutenant Selfridge,
the accident appears to have been due to the failure of a vital part—the
propeller. It has since become customary to cover the tips of propellers
for at least a foot or so with fabric tightly fitted and varnished so as
to become practically an integral part of the wood. This prevents
splintering as well as avoiding the danger of the laminations succumbing
to centrifugal force and flying apart. At the extremely high speeds,
particularly at which direct-driven propellers are run, the stress
imposed on the outer portion of the blades by this force is tremendous.
In making any attempt to compare the number of accidents to the biplane
and the monoplane, it must also be borne in mind that the former has
been in the majority.
Delagrange’s accident offers two special features of technical interest.
It was the first fatality to happen with the monoplane and was likewise
the first fatal accident which appeared to be distinctly due to a
failure of the main structure of the machine. For obvious reasons, it is
usually difficult to definitely fix the cause of an accident, but in
this case there seemed good reason to suppose that the main framing of
one of the wings gave way altogether. Curiously enough, Santos-Dumont
had an accident the day following from an exactly similar cause, the
machine plunging to the ground. But with the good fortune that has
attended the experimenter throughout his long aerial career, he was
uninjured. It was definitely established that the cause was the fracture
of one of the wires taking the upward thrust of the wing. In the case of
the biplane, the top and bottom members are both of wood, with wooden
struts, the whole being braced with numerous ties of wire. In the
monoplane, however, the main spars are trussed to a strut below by a
comparatively small number of wires. The structure of each wing is, in
fact, very much like the rigging of a sailboat, the main spars taking
the place of the mast while the wire stays take that of the shrouds,
with this very important difference, that the mast of the boat is
provided with a forestay to take the longitudinal pressure when going
head to the wind, while the wing of an aeroplane often has no such
provision, the longitudinal pressure due to air resistance being taken
entirely by the spar.
It is quite possible that this had something to do with Delagrange’s
accident, as, in the effort to make a new record, his Bleriot had just
been fitted with a very much more powerful motor. In fact, double that
for which the machine was originally designed, and this was given by the
maker as the probable cause of the mishap. As the new motor was of a
very light type, the extra weight, if any, was quite a negligible
proportion of the total weight of the machine. The vertical stresses on
the wings and their supporting wires would, therefore, not be materially
increased. But as the more powerful engine drove the wings through the
air a great deal faster, the stresses brought upon them by the increased
resistance would be substantially augmented and, unless provision were
made for this, the factor of safety would be much reduced. Whether the
failure of the wing was actually from longitudinal stress or the
breaking of a supporting wire, as in Santos-Dumont’s case, will never be
known, but it is quite clear that the question of ample strength to
resist longitudinal stresses should be carefully considered, especially
when increasing the power of an existing machine.
The question of the most suitable materials and fastenings for the
supporting wires is, moreover, a matter which requires very careful
consideration. In the case of the biplane, the wires are so numerous
that the failure of one, or even more, may not endanger the whole
structure, but those of the monoplane are so few that the breaking of
but one may mean the loss of the wing. In this respect, as in others,
the conditions are parallel to the mast of the sailboat. It is only
reasonable to expect, therefore, that similar materials would be best
adapted to the purpose. At present, however, the stays of aeroplane
wings are almost invariably solid steel wire, or ribbon, while marine
shrouds are always of stranded wire rope, solid wire not having been
found satisfactory. Weight for weight, the solid wire will stand a
greater strain when tried in a testing machine than will the stranded
rope, but practice has always demonstrated that it is not so reliable.
The stranded rope never breaks without warning, and sometimes several of
its wires may go before the whole gives way. As the breakage of the
strands can be easily seen, it is possible to replace a damaged stay
before it becomes unsafe. In the case of a single wire, there is nothing
to show whether it has deteriorated or not. It seems a doubtful policy
to use in an aeroplane what experience has shown not to be good enough
for a boat, and stranded wire cables particularly designed for
aeronautic use are now being placed on the market in this country.
*Record Breaking*. Striving after records has undoubtedly proved one of
the most prolific causes of accident. What is wanted to make the
aeroplane of the greatest practical use is that it should be safe and
reliable. The tendency of record-breaking machines is the exact opposite
of this, as the weights of all the most essential parts must be cut down
to the finest limits possible in order to provide sufficient power and
fuel-carrying capacity for the record flight. It is, in fact, generally
the case in engineering that the design and materials which will give
the best results for a short time are essentially different from those
which are the most reliable, and striving after speed records consists
simply in disregarding safety and reliability to the greatest extent to
which the pilots are willing to risk their necks, and there is no
difficulty in getting men to take practically any risk for the
substantial rewards offered.
The performance of specially sensational feats in the air is likewise a
fertile source of accidents. One noted aviator who has the reputation of
being a most conservative and expert operator, while endeavoring to land
within a set space, made too sudden a turn, which resulted in the tail
of the machine giving way, precipitating him to the ground. In fact, the
number of failures resulting from abrupt turns shows conclusively that
there is too small a factor of safety in the construction, not because
the added weight could not be carried, but because the extreme lightness
alone made possible the stunts for which there is always applause or
financial reward. It may seem strange to the man whose only interest in
aeronautics is that of an observer, that so many should be willing to
take such unheard-of chances; that an aeronaut will rise to great
heights, knowing in advance that a vital part of his machine has been
deranged, or is only temporarily repaired; and that many others will
attempt ambitious flights with engines or other parts that have never
been tested previously in operation in the air. Many young and
inexperienced aviators are not content to thoroughly test out each new
part on the ground, or close to it, but must go aloft at once to do
their experimenting, with the usual result of such foolhardiness. If in
other sports safe conditions were absolutely disregarded in this
manner—take football as an instance—the resulting fatalities would not
be charged against the sport itself. But aviation is so extremely novel
and likewise so mysterious to the uninitiated that this is never taken
into consideration.
*Excessive Lightness of Machines*. If, even at the present early stage
of aviation, machines are being made excessively light for purposes of
competition, it is time that the contest committees of organizations in
charge of meetings formulate rules as to the size of engines, weight of
machines, and similar factors, so that accidents will not only be
reduced to a minimum, but competition along proper lines will develop
types of machines which are useful and not merely racing freaks, as has
already been done in the automobile field. Hair-raising performances
also should be prohibited, at least until such time as improvements in
the construction of machines make it reasonably certain that they are
able, to withstand the terrific strains imposed upon them in this
manner. Suddenly attempting to bring the machine to a horizontal plane
after a long dip at an appalling angle is an extremely dangerous
maneuver, whether it be taken in the upper air or is one of the now
familiar long glides to earth, which require pulling up short when
within a few feet of the ground and after the dropping machine has
acquired considerable inertia. The aviator is simply staking his life
against the ability of the struts and stays to withstand the terrific
stresses imposed upon them every time this is done.¹
As at present constructed, many of the machines are not sufficiently
strong to withstand the utmost in the way of speed and sudden turns
which the skilled operator is likely to put on them. They should be made
heavier, or of materials providing greatly increased strength with the
same weight. That they can be made heavier without seriously damaging
their flying ability has been clearly demonstrated by the numerous
flights with one and two passengers, and on one occasion in which three
passengers besides the driver were taken up on an ordinary machine. This
was likewise tempting fate by overloading, but it served to show the
possibilities.
[Illustration: Fig. 49. Monoplane is Liable to Stand on its Head if
Landing is Not Properly Made]
*Landings*. Then there is a class of accidents for which neither the
aviator nor the machine is responsible, as where spectators have crowded
on the field, causing the flyers to make altogether too sudden or
impromptu landings at angles which would otherwise not be considered for
a moment. This, of course, refers solely to exhibition meets, and the
comparative immunity of cross-country flights from fatal accidents as
compared with the latter, speaks for itself in this respect. In the
open, even the novice seems to be able to pick a safe landing,
especially if high enough to glide some distance before reaching the
ground. This brings out the fact that, as a rule, the machines are safer
in the air—a large part of the danger lies in making a landing. Starting
places are usually smooth, but landing places may be the reverse. When
alighting directly against the wind, which is the only safe practice,
most of the machines will remain on an even keel until they come to a
stop, but the slightest bump or depression, in connection with a side
gust of wind, may swerve it around and capsize it, as demonstrated by
the illustration of a bad landing by De Lesseps, Fig. 49. This was
emphasized by some of the minor accidents at the International Meet near
New York. There is no precision or accuracy in the movements of a flying
machine when rolling slowly over the ground after the engine has been
shut off, and the aviator is, to a certain extent, helpless. The wheels
on most machines are placed too near the center and too close together.
When an attempt is made to land with the wind on the quarter or side,
although the machine may strike the ground safely, owing to the accuracy
with which it may be controlled in the air while at speed, it is apt to
turn after rolling a short distance and the wind will then easily
capsize it, breaking a wing, smashing a propeller, and sometimes
injuring the motor or the aviator. Accidents from this cause have been
common.
These accidents and collisions with obstructions make plain the fact
that brakes are quite as necessary on an aeroplane as on any other
vehicle intended to run on the ground. Practically all aeroplanes are
fitted with pneumatic tires and ball-bearing wheels and, as there is
very little head resistance, they will run a considerable distance after
alighting at a speed of 20 to 30 miles an hour. The employment of a
brake on the wheels would have averted one of the fatal accidents
abroad, as noted in Table III. They would have enabled Johnstone to stop
his machine before colliding with the fence surrounding the aviation
grounds at Denver, and they would have prevented several minor accidents
at various meets, which, though not endangering the aviator in every
instance, have often seriously damaged his machine. Every exhibition
field is obstructed by fences, posts, buildings, and the like, and to
avoid coming in contact with these, as well as with the irrepressible
spectator, the aviator should certainly have an effective means of
bringing the machine to a standstill when it is running along the
ground. How much more so is this necessary for cross-country flying when
the choice of a landing place is a difficult matter at best. Ability to
come to a stop quickly would make it possible to land in restricted
places where only a very limited run along the ground could be had.
*Lack of Sufficient Motor Control*. Another class of accidents that take
place on the ground suggests the necessity for improving the motor
control. In alighting, the motor is usually stopped by cutting off the
ignition—ordinarily by grounding or short-circuiting. Throttling to stop
appears to be seldom resorted to, but as several instances have occurred
in which the aviator found it impossible to cut off the ignition,
resulting in a collision with another machine or a building, it is
evident that the control should be arranged so that both methods could
be employed. With the increasing use of air-cooled motors that may
continue to run through self-ignition after the spark has been cut off,
this is more necessary than ever.
While it has been demonstrated that the stoppage of the motor does not
necessarily involve a fall, most aviators will naturally prefer to
command the assistance of the motor at all times, and in the case of
motors using a carbureter this should be jacketed either from the
cooling water or the exhaust, and means provided for increasing the air
supply to prevent the motor stopping at a great height owing to the cold
and the rarefied air. The reasons for this have been gone into more at
length under the heading of "Altitude." With these and similar
improvements that will be suggested by experience and further accidents,
there appears to be no reason why aviation can not be made as safe as
the personal equation will permit it to be. There will always be
reckless flyers. Ignorance and incompetence can not be altogether
eliminated any more than they can in sailing, hunting, or any other
sport. The annual hunting fatalities from these causes in this country
alone make a total beside which the aggregate of four years in aviation
the world over, is but an insignificant fraction.
*Parachute Garment as a Safeguard*. To save as many as possible of these
reckless ones from themselves, so to speak, a parachute garment has been
devised to ease the shock of the fall. It will be recalled that Voisin
would not fly in his biplane until he had provided himself with a
heavily-padded helmet, somewhat on the order of the football headpiece.
But neither a padded headpiece nor padded clothing would avail much
against a fall of any kind from an aeroplane; hence, the parachute
garment. Its object is not to take the shock of a fall, as are the pads,
nor is it to prevent a fall, but to reduce the rate of drop by
interposing sufficient air resistance to make the fall safe. This new
parachute is in the form of a loose flowing garment, securely fastened
to the body and fitted over a framework carried on the aviator’s back.
The lower ends of the garment are secured to the ankles. The arrangement
is such that when the aviator throws out his arms, the garment is
extended somewhat in umbrella or parachute form, thus creating
sufficient resistance to prevent too rapid a descent. Experiments have
been made with this parachute dress in which the wearer has jumped from
buildings, cliffs, and other heights, and the garment has assumed its
role of parachute at once, permitting a safe and easy descent.
*Study of Stresses in Fancy Flying*. To sum up, it will be seen that the
most prolific cause of fatalities is the personal equation. Of all the
many dangers encountered in aeroplaning, one of the most clearly
defined, as well as one of the most seductive, results from fancy
flying: from wheeling round sharp, horizontal curves; from conic
spiraling; from cascading, swooping, and undulating in vertical plane
curves, popularly dubbed "stunts." These are forms of flying in which
aviators constantly vie with one another. They frequently result in
imposing stresses upon the machine which are far beyond its capacity to
withstand. The danger is particularly alluring to reckless young
aviators engaged in public exhibitions. The death of St. Croix
Johnstone, at the Chicago Meet in the summer of 1911, affords a typical
illustration of what may be expected as the result of such performances.
Nevertheless, partly because they do not adequately appreciate the risk,
and largely, no doubt, because of the liberal applause accorded by an
admiring throng which also fails to realize the hazardous nature of the
fascinating maneuvers, there will doubtless always be aviators to
undertake such feats.
Singularly enough, the exact magnitude of such hazards, or more
accurately, the extent of the increased stress in the machine, though
beyond even the approximate guess of the aviator, is capable of nice
computation in terms of the speed and curvature of flight. During an
exhibition meet in Washington, D. C, during the summer of 1911, Glenn H.
Curtiss found difficulty in restraining one of his young pupils from
executing various hair-raising maneuvers. He would plunge from a great
elevation to acquire the utmost speed, then suddenly rebound and shoot
far aloft. He would undulate about the field, and on turns would bank
the machine until the wings appeared to stand vertical. Curtiss solemnly
warned the young aviator and earnestly restrained him, pointing out the
dangers of sweeping sharp curves at high speed, of swooping at such
dangerous angles, and the like. Curtiss then turned to A. F. Zahm and
expressed the wish that someone would determine exactly the amount of
the added stress in curvilinear flight. The following, published by
Zahm, in the _Scientific American_, gives the method of calculating
this:
When a body pursues a curvilinear path in space, the centripetal force
urging it at any instant may be expressed by the equation
Fn = m(V/R)² (absolute units) = (m/g)(V²/R) (gravitational units)
in which _Fn_ is the centripetal force, _m_ the mass of the body, _V_
its velocity, and _R_ the instantaneous radius of curvature of the path
followed by its center of mass. Since the mass may be regarded as
constant for any short period, the equation may be expressed by the
following simple law:
_The centripetal force varies directly as the square of the velocity of
flight and inversely as the instantaneous radius of the curvature of its
path._
In applying the above equation to compute the stress in an aeroplane of
given mass _m_, we may assume a series of values for _V_ and _R_,
compute the corresponding values for _Fn_, and tabulate the results for
reference. Table IV has been obtained in this manner. It may be noted
that on substituting in the equation, _V_ is taken as representing miles
per hour, _R_ as feet, and _g_ as 22 miles an hour, in order to simplify
the figuring, this being 32.1 feet per second. The table shows at a
glance the centripetal force acting on an aeroplane to be a fractional
part of the gravitational force, of weight of the machine and its load.
For example, if the aviator is rounding a curve of 300 feet radius at 60
miles per hour, the centripetal force is 0.55 of the total weight. At
the excessively high speed of 100 miles per hour and the extremely short
radius of 100 feet, the centripetal force would be 4.55 times the weight
of the moving mass. The pilot would then feel heavier on his seat than
he would sitting still with a man of his own weight on either shoulder.
For speeds below 60 miles per hour and radii of curvature above 500
feet, the centripetal force is less than one third of the weight. The
table gives values for speeds of 30 to 100 miles per hour, by increments
of 10 miles and for radii of curvature of 100 to 500 feet, by increments
of 100 feet, so that intermediate speeds and radii may readily be
calculated.
The entire stress on the aeroplane in horizontal flight, being
substantially the resultant of the total weight and the centripetal
force, can readily be figured by compounding them. Thus in horizontal
wheeling, the resultant force as shown in the diagram, Fig. 50, is
approximately
_F = √(Fn²+W²)_
In swooping, or undulating in a vertical plane, the resultant force at
the bottom of the curve has its maximum value
_F = (Fn+W)_
and at any other part of the vertical path, it has a more complex though
smaller value, which need not be given in detail.
It is obvious that the greatest stress on the machine occurs at the
bottom of a swoop, if the machine be made to rebound on a sharp curve.
The total force _(Fn+W)_ sustained at this point may be found from the
table, if _V_ and _R_ be known, simply by adding 1 to the figures given,
then multiplying by the weight of the machine. For example, if the speed
be 90 miles per hour and the radius of curvature 200 feet, the total
force on the sustaining surface would be 2.84 times the total weight of
the machine. In this case, the stress on all parts of the framing would
be 2.84 times its value in level flight, when only the weight has to be
sustained. The pilot would feel nearly three times his usual weight.
[Illustration: Fig. 50. Force Diagram in Horizontal Wheeling]
From the foregoing, it is apparent that in ordinary banking at moderate
speeds on moderate curves, the additional stress due to centripetal
force is usually well below that due to the weight of the machine, and
that in violent flying, the added stress may considerably exceed that
due to the weight of the machine and may accordingly be dangerous,
unless the aeroplane be constructed with a specially high factor of
safety. But there is nothing in the results here obtained that seems to
make sharp curving and swooping prohibitive. If the framing of the
machine be given an extra factor of safety, at the expense perhaps of
endurance and speed, it may be made practically unbreakable by such
maneuvers, and still afford to the pilot and spectators alike all the
pleasures of fantastic flying.
*Methods of Making Tests*. In order to obtain actual data for the
fluctuations of stress in an aeroplane in varied flying, it is suggested
that the stress or strain of some tension or compression member of the
machine be recorded when in action; or simpler still, perhaps, that a
record of the aeroplane’s acceleration be taken and particularly its
transverse acceleration. A very simple device to reveal the transverse
acceleration of an aeroplane in flight would be a massive index
elastically supported. A lath or flat bar stretching lengthwise of the
machine, one end fixed, the other free to vibrate, and carrying a pencil
along a vertical chronograph drum, would serve the purpose. This could
be protected from the wind by a housing as shown in the sketch, Fig. 51.
[Illustration: Fig. 51. Method of Boxing an Acceleration Recorder]
An adjustable sliding weight could be set to increase or diminish the
amplitude of the tracing, and an aerial or liquid damper could be added
to smooth the tracing. The zero line would be midway between the
tracings made on the drum by the stationary instrument when resting
alternately in its normal position and upside down; the distance between
this zero line to the actual tracing of the stationary instrument would
be proportional to the aeroplane stresses in level, rectilinear flight;
while in level flight on a curve, either horizontal or vertical, the
deviation of the mean tracing from the zero line would indicate the
actual stress during such accelerated flight. Of course, the drum could
be omitted and a simple scale put in its place, so that the pilot could
observe the mean excursion of the pencil or pointer from instant to
instant; also, the damper of such excursion could be adjusted to any
amount in the proposed instrument if the vibrating lath fitted its
encasing box closely with an adjustable passage for the air as it moved
to and fro; or if light damping wings were added to the lath, or flat
pencil bar.
Another method would be to obtain by instantaneous photography the
position of the centroid of the aeroplane at a number of successive
instants, from which could be determined its speed and path, or _V_ and
_R_ of the first equation, by which data, therefore, the stress could be
read from Table IV.
Perhaps the simplest plan would be to add an acceleration penholder,
with its spring and damper, to any recording drum the aeroplane may
carry for recording air pressure, temperature, speed, and so forth.
Indeed, all such records could be taken on a single drum.
A score of devices, more or less simple, but suitable for revealing the
varying stress in an aeroplane, will occur to any engineer who may give
the subject attention. And it is desirable in the interests both of
aeroplane design and of prudent manipulation that someone obtain roughly
accurate data for the stresses developed in actual flight.
*Increment of Speed in Driving*. It is commonly supposed by aviators
that the _increment_ of speed due to driving is very prodigious. An easy
formula will determine the major limit of such speed increment. If the
initial and natural speed of the aeroplane be _v_, and the change of
level in diving be _h_, while the speed at the end of the dive be _V_,
the minimum change of level necessary to acquire any increment of speed,
_V—v_, may be found from the equation
h = (V - v)/2g
If, as before, _g_ be taken as 22 miles per hour, the equation reduces
to the convenient formula
h = (V-v)/30
in which _V_ and _v_ are taken in miles per hour. Assuming various
values for _V_ and _v_, Table V has been found for the corresponding
values of _h_ in feet: For example, if the natural speed of the
aeroplane in level flight be 50 miles per hour, and the aviator wishes
to increase the speed by 20 miles per hour, he must dive at least 80
feet, assuming that the aeroplane falls freely, like a body in vacuo, or
that its propeller overcomes the air resistance completely; otherwise
the fall must be rather more than 80 feet.
It has been suggested that a contest be arranged to determine which
aviator could dive most swiftly and rebound most suddenly, the prize
going to the one who should stress his machine most as indicated by the
accelerograph above proposed. But to avoid danger, the contest would
have to be supervised by competent experimentalists, and would be best
conducted over water. It is safe to say that more than one well-known
aeroplane would be denied entry in such a contest because of lack of a
sufficient factor of safety in its construction.
*Dirigible Accidents*. Because its wrecks are spectacular and the loss
involved tremendous, the dirigible has probably earned an undeserved
reputation, though it must be admitted that the big airships have come
to grief with surprising regularity. The fact must be noted, however,
that when an airplane is wrecked, the aviator seldom escapes with his
life, while the spectators’ lives are endangered to an even greater
extent, whereas in the case of the dirigible, the loss is simply
financial, both the crew and passengers usually escaping without a
scratch. This is largely due to the fact that the majority of accidents
to dirigibles have happened on the ground, and have been caused by lack
of facilities for properly handling or "docking" the huge gas bag. Of
course, lack of flotation or an accident to the motors, or both
combined, have brought two of the numerous Zeppelins to earth in a very
hazardous manner, though no one was killed, while four French army
officers lost their lives in the Republique disaster, the exact cause of
which was never definitely ascertained. This was likewise the case with
Erbsloeh and his companion who were dropped from the sky, their airship
having taken fire. It was thought that ignition was caused by
atmospheric electricity, in this instance.
By far the great majority of later dirigible accidents have been due
solely to the crude methods of handling the airships on the ground, and
the frequency with which these have occurred should certainly have been
responsible for the adoption of improvements in this respect at an
earlier day.
For instance, the Morning Post, a big Lebaudy type bought for English
use, had the envelope ripped open by an iron girder projecting from its
shed. Repairs took several months, and at the end of the first trial
thereafter, the ship was again Wrecked in landing. A company of soldiers
failed to hold the big craft and it drifted broadside into a clump of
trees, hopelessly wrecking it. In attempting to dock the Deutschland I,
200 men were unable to hold it down, a heavy gust of wand catching the
big airship and pounding it down on top of a wind break that had been
specially erected at the entrance of the shed for protection. A similar
accident happened to the big Parseval, a violent gust of wind casting it
against the shed and tearing such a hole in the envelope that the gas
rushed out and the car dropped 30 feet to the ground. The big British
naval dirigible of the rigid type, the Mayfly, was broken in half in
attempting to take it out of the shed the first time. A cross wind was
blowing and the gas bag of one of the central sections was torn,
deflating it and showing in a striking manner that the solidity of a
rigid dirigible results chiefly from the aerostatic pressure of the gas
in its various compartments. Without the gas lift, a rigid frame is so
in reality only for certain limited distances, as was shown by the total
collapse of the Mayfly’s frame after having been subjected to the
opposed leverage of the parts on either side of the original break.
This, of course, was an error in design, as the frame of a rigid
dirigible should certainly not be so weak in itself as to collapse upon
the deflation of a single one of the central compartments. The incident
on the trip of the Zeppelin III to Berlin, in 1909, when the flying
blades of a broken propeller pierced the hull without causing an
accident, shows how much resistance it may offer.
¹ This is exactly what occured at the Chicago Meet, August 15, 1911,
when Badger’s Baldwin biplane collapsed at the end of a long dive,
causing the death of the aviator.
AMATEUR AVIATORS
It will probably come as a surprise to the average reader to learn that
at the end of 1910, there were more than a thousand amateur aviators in
this country, though all the flights which form the subject of newspaper
reports have been the work of not more than a dozen flyers and doubtless
half the population has not as yet seen an aeroplane in flight. The
desire to fly, whether it be to satisfy one’s desire to soar above the
world in seeming defiance of natural laws, or merely to obtain the
financial reward that is won by successful flight, attracts a great many
from all stations and walks of life. This is particularly true among
older boys who look on aviation as an advanced form of kite-flying. An
example of rather serious work along this line may be cited of two high
school boys of Chicago, Harold Turner and Fred Croll, who built a
monoplane weighing 125 pounds, Fig. 52. This machine, although too small
for a motor, was equipped with rudder and other operating planes and
levers, the elevating plane and ailerons being automatically operated by
an electrical device. On one of its flights the machine, carrying a 120
pound operator, was started and propelled by attaching it to an
automobile; it rose to a height of 15 feet, and remained in the air 43
seconds.
Contrary to all precedent, the average amateur is bent upon achieving
what the skilled professional considers as beyond even his talent and
resources—that of building his own flying machine. With every other
mechanical vehicle, the amateur learns to drive first and the majority
are content with that achievement—for example, very few chauffeurs have
any great ambition to build their own automobiles. With flying machines
(one of the most difficult of mechanical contrivances), nearly all
amateurs want to construct new types for themselves and all confidently
expect to fly with no more knowledge than that gained in constructing
them. We all have to be apprentices before becoming masters, so all
aviators necessarily have to be learners and "grass cutters" before
being professionals. Charles K. Hamilton was an exception, but he was
already an expert pilot of dirigible balloons, and he did not try to
build his own aeroplane. Willard, Mars, and Ely, all Curtiss pupils,
flew after a very short training, but they did not attempt to construct
aeroplanes for themselves. This is also true of Clifford B. Harmon, the
champion amateur.
[Illustration: Fig. 52. What an Amateur Aviator Can Do in Building an
Aeroplane]
*Classes of Amateurs*. _Inventors_. Generally speaking, amateurs are of
two classes. Those of the _first class_ believe they have conceived some
entirely new system or invention, or an improvement on some machine that
has previously proved a failure; they think they have discovered the
secret which other inventors who preceded them failed to grasp. They
expend their meager capital in trying to realize high hopes. A
comparatively small number ever get as far as completing the machine and
one trial on the field is usually sufficient to put a quietus on those
who do, as it is disappointing, to say the least, to see the result of a
number of months’ work undone in a twinkling without the machine having
shown the least disposition or ability to get off terra firma.
_Would Be Performers_. _The second class_ finds its chief incentive in
the munificent reward to be gained with what appears to be comparatively
little effort or expenditure, and the amateur who is seeking financial
returns has no alternative except to build his own machine, or enter
either the Wright or Curtiss school of flying and secure a berth with
one of these companies.
*Wright and Curtiss Patents*. This is the result of conditions at
present obtaining in the field of aviation. The only generally
successful types of American aeroplanes are the Wright and Curtiss, and
the acquirement of a biplane of either type means the expenditure of at
least $5,000 for the machine alone, and they are sold only to
individuals on the express condition that the machines are not to be
used for exhibition or as a means of profit to the owner. The
manufacturers have expert flyers of their own who attend meets and fairs
throughout the country. It would make their monopoly impossible to allow
outsiders to fly their aeroplanes publicly or to exhibit them. By this
restriction the price of the machines is kept up and large returns are
gained by exhibitions and flying.
To break this monopoly by importing European machines is not possible.
All the successful aeroplanes made abroad such as the Farman, Cody, and
Sommer biplanes; and the Bleriot, Antoinette, and Grade monoplanes are
fitted with devices of control or stability, or both, covered by the
Wright patents and can not be flown in this country without legal
trouble. The numerous foreign aviators who brought over their machines
in the fall of 1910 to compete at the International Meet, did so only on
being granted a concession by the Wright Company to the effect that they
would not be considered as infringers and sued. Similar arrangements
were made at subsequent meets and this handicap will always be present
where foreign machines are used.
_Evasion by Invention of New Types_. But when he thinks of the
unprecedented sums paid professionals for simply exhibiting their
machines and making short flights, the amateur is anxious to obtain a
share of the profits. No thought is given the fact that were he and all
his kind permitted to fly, the achievement would soon be commonplace and
the aviator’s golden age would be over. There are accordingly hundreds
of would-be aviators in this country today who are striving to evade the
Wright basic patents by either devising entirely new types of
aeroplanes, or by inventing new methods of control and stability that
will not infringe. Others, reasoning that the old aeroplanes built
before the advent of the Wright machine cannot be held as infringements
owing to priority, propose to develop Maxim, Langley, and Ader machines,
though the dictum in the New York Court of Appeals decision referred to
under the head of "Legal Status of Wright Patent," which states that a
prior machine which _had never been known to fly_ would not be
considered an anticipation of a modern successful machine, may prove a
stumbling block in their case as well. Thus, a round of the workshops of
these enthusiasts reveals a host of heavier-than-air machines of every
conceivable type and shape, every one of which, according to its
builder, is _an aeroplane that will fly_. Mineola and Garden City, Long
Island, harbor a score of these little shops the year round, but the
same scenes are being enacted on a smaller scale in almost every state
in the Union, and particularly in California, Ohio, Kansas,
Massachusetts, and Arizona, in addition to which there are many who are
carrying their experiments on in secret. Each believes deep in his heart
that he will succeed where a master failed.
"Maxim failed with this type of machine," quotes one. "How did he expect
to fly when his control was not proportionate to the machine’s lift
capacity?" Seemingly, nobody ever thought of that and our friend will
make a fortune by going Maxim one better, but he does not. After months
of labor and a great deal of expense he finds that some unforeseen
difficulty develops which keeps his machine to earth as if it were part
and parcel of it. Another has conceived a type of monoplane that is
entirely new—different from any existing type—and as the latter are all
foreign, he prides himself on having developed a monoplane that will be
entirely American—the first and only American monoplane. Theoretically,
it is a wonder; mechanically it is correct; and it speeds over the turf
with surprising velocity; but when the elevating rudder is operated to
make the machine rise, it balks and plunges head first into the ground.
Again and again, the propeller and other broken parts are replaced at no
small expense; again and again the inventor goes over every part of the
machinery and computes the dimensions of the supporting surface to see
if it all corresponds with the formula of his special theory. But time
after time, the aeroplane acts like a jumping frog and lands head first.
At last, its builder becomes convinced that there is something radically
wrong and begins to depart from his original plans, involving changes
that simply mean a waste of effort and money, since the inventor does
not himself know what he is trying to correct and no one else knows
better than he what the trouble is.
_Evasion by Acquiring European Types_. Others still, realizing from the
foregoing experiences that it is almost impossible to construct an
entirely new type of aeroplane off-hand, acquire European types and
propose to fit them with new control and stability devices, such as are
not covered by the Wright patents. So far, none has succeeded. Somehow,
the Wrights seem to have covered all the conceivable working devices for
control and stability, and the numerous attempts have accordingly
resulted in failure. Undoubtedly, some of these aeroplanes built by
amateurs may really be capable of flight; but how is the inventor to
know it when he lacks the ability to operate it? To know how to fly an
aeroplane is a condition precedent to success in the field of aviation
that can not be met by building of a machine. The beginner is thus badly
handicapped. Even though his machine may embody the elements essential
to successful flight, he may never be able to establish the fact, since
his first blundering attempt or two frequently ends by wrecking the
machine, and many have neither the means nor the stamina to persevere
further after a few bad wrecks, involving weeks and weeks of rebuilding
each time. He can not engage an expert to fly his machine for him, as
the expert’s time per minute figures out a price that makes him gasp,
and even at that the expert professional’s time is pretty much all
taken. Furthermore, very few would run the risk of attempting to fly an
untried aeroplane—they have more to lose through accidental injury than
the builder has through the failure of his theories.
And so it is with most inventors. They may have conceived something
really good, but it is not complete, and an aeroplane is hardly worth
its weight as junk unless it is. Hundreds of patents are taken out every
year on devices to be used on heavier-than-air machines; inventors by
scores make daily rounds trying to interest financiers in some seemingly
wonderful mechanical scheme, and dozens of companies are organized each
year to exploit some especially promising inventions. Numbers of
aeroplanes are constructed and hailed as marvels, but, somehow, when a
successful flight is made by an amateur it is always with some standard
aeroplane, either of the Curtiss or Farman types, and mostly the former.
In fact, the Curtiss has become a favorite with the amateur since the
Federal court refused to sustain the granting of a preliminary
injunction in favor of the Wright Company against Glenn H. Curtiss. It
is accordingly being taken for granted in general that the outcome of
the Wright vs. Curtiss litigation will be to declare the Curtiss machine
non-infringing. Should it be the other way about, there will certainly
be gloom and despair in the amateur camps throughout the country.
However, neither the Wrights nor Curtiss impose any restriction upon the
building of machines of their types for experimental purposes, so that
the amateur who wishes to copy them may safely do so, provided no
attempt be made to employ the machine for purposes of public exhibition
or financial gain.
EXAMINATION PAPER
BUILDING AND FLYING AN
AEROPLANE
*PART II*
*Read Carefully*: Place your name and full address at the head of the
paper. Any cheap, light paper like the sample previously sent you may be
used. Do not crowd your work, but arrange it neatly and legibly. _Do not
copy the answers from the Instruction Paper; use your own words so that
we may be sure that you understand the subject_.
1. Contrast the Bleriot with the Curtiss in every essential
particular.
2. Give details of the Bleriot running gear.
3. How is the supporting plane of the Bleriot built and reinforced?
4. What sort of fabric is used to cover the plane and how is it
fastened on?
5. Describe by sketch the Bleriot control system.
6. How does the location of the motor in the Bleriot compare with its
location in the Curtiss?
7. What is “grass-cutting” and why is it practiced?
8. Describe some of the devices used in aviation schools.
9. How is the elevating plane manipulated to start the aeroplane from
the ground?
10. How is the static balance of a machine determined?
11. How does warping the wings affect the behavior of an aeroplane?
How should this be practiced?
12. Give the process of making a turn in an aeroplane.
13. What is “banking”? What must be done to prevent excessive banking
on a turn?
14. How can a turn be made in a wind?
15. Why should the start and the landing always be made in the teeth
of the wind?
16. What is the attitude of the masters of aviation toward fancy
flying?
17. Classify the most common sources of accidents.
18. What must an aviator do in case his motor stops in midair? Is this
considered a dangerous situation?
19. What are the relative merits of biplane and monoplane as regards
the avoidance of accidents?
20. What are some of the devices used to protect the aviator in case
his machine collapses?
21. Analyze rather carefully the additional stresses put upon an
aeroplane when an aviator suddenly swoops and then rights his
machine by a quick movement of the control.
*After completing the work, add and sign the following statement:*
I hereby certify that the above work is entirely my own.
(Signed)
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