Flying Machines: Construction and Operation

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Flying Machine: Construction and Operation
W.J. Jackman and Thos. H. Russell

FLYING MACHINES: CONSTRUCTION and OPERATION

A Practical Book Which Shows, in Illustrations,
Working Plans and Text, How to Build and Navigate the
Modern Airship.

By
W.J. Jackman, M.E.,
Author of "A B C of the Motorcycle,"
"Facts for Motorists," etc. etc.

AND

THOS. H. RUSSELL, A.M., M.E.,
Charter Member of the Aero Club of Illinois, Author of
"History of the Automobile," "Motor Boats: Construction
and Operation," etc. etc.

WITH INTRODUCTORY CHAPTER BY
OCTAVE CHANUTE, C.E.,
President Aero Club of Illinois

1912

PREFACE.

This book is written for the guidance of the novice in
aviation--the man who seeks practical information as to
the theory, construction and operation of the modern
flying machine. With this object in view the wording
is intentionally plain and non-technical. It contains some
propositions which, so far as satisfying the experts is
concerned, might doubtless be better stated in technical
terms, but this would defeat the main purpose of its preparation.
Consequently, while fully aware of its shortcomings
in this respect, the authors have no apologies to make.

In the stating of a technical proposition so it may be
clearly understood by people not versed in technical matters
it becomes absolutely necessary to use language
much different from that which an expert would employ,
and this has been done in this volume.

No man of ordinary intelligence can read this book
without obtaining a clear, comprehensive knowledge of
flying machine construction and operation. He will
learn, not only how to build, equip, and manipulate an
aeroplane in actual flight, but will also gain a thorough
understanding of the principle upon which the suspension
in the air of an object much heavier than the air is made
possible.

This latter feature should make the book of interest
even to those who have no intention of constructing or
operating a flying machine. It will enable them to better
understand and appreciate the performances of the
daring men like the Wright brothers, Curtiss, Bleriot,
Farman, Paulhan, Latham, and others, whose bold experiments
have made aviation an actuality.

For those who wish to engage in the fascinating pastime
of construction and operation it is intended as a
reliable, practical guide.

It may be well to explain that the sub-headings in the
articles by Mr. Chanute were inserted by the authors
without his knowledge. The purpose of this was merely
to preserve uniformity in the typography of the book.
This explanation is made in justice to Mr. Chanute.
THE AUTHORS.

IN MEMORIAM.

Octave Chanute, "the father of the modern flying machine,"
died at his home in Chicago on November 23, 1910,
at the age of 72 years. His last work in the interest of
aviation was to furnish the introductory chapter to the first
edition of this volume, and to render valuable assistance
in the handling of the various subjects. He even made the
trip from his home to the office of the publishers one
inclement day last spring, to look over the proofs of the
book and, at his suggestion, several important changes were
made. All this was "a labor of love" on Mr. Chanute's
part. He gave of his time and talents freely because he
was enthusiastic in the cause of aviation, and because he
knew the authors of this book and desired to give them
material aid in the preparation of the work--a favor that
was most sincerely appreciated.

The authors desire to make acknowledgment of many courtesies
in the way of valuable advice, information, etc., extended by Mr.
Octave Chanute, C. E., Mr. E. L. Jones, Editor of Aeronautics,
and the publishers of, the New England Automobile Journal and
Fly.

CONTENTS

Chapter

I. Evolution of the Two-Surface Flying Machine
Introductory Chapter by Octave Chanute, C. E.
II. Theory Development and Use
Origin of the Aeroplane--Developments by Chanute
and the Wrights--Practical Uses and Limits.
III. Mechanical Bird Action
What the Motor Does--Puzzle in Bird Soaring.
IV. Various Forms of Flying Machines
Helicopters, Ornithopters and Aeroplanes--
Monoplanes, Biplanes and Triplanes.
V. Constructing a Gliding Machine
Plans and Materials Required--Estimate of Cost--
Sizes and Preparation of Various Parts--Putting the
Parts Together
VI. Learning to Fly
How to Use the Glider--Effect of Body Movements
--Rules for Beginners--Safest Place to Glide.
VII. Putting On the Rudder
Its Construction, Application and Use.
VIII. The Real Flying Machine
Surface Area Required--Proper Size of Frame and
Auxiliaries--Installation of Motor--Cost of
Constructing Machine.
IX. Selection of the Motor
Essential Features--Multiplicity of Cylinders--Power
Required--Kind and Action of Propellers--Placing
of the Motor
X. Proper Dimensions of Machines
Figuring Out the Details--How to Estimate Load
Capacity--Distribution of the Weight--Measurements
of Leading Machines.
XI. Plane and Rudder Control
Various Methods in Use--Wheels and Hand and
Foot Levers
XII. How to Use the Machine
Rules of Leading Aviators--Rising from the Ground
--Reasonable Altitude--Preserving Equilibrium--
Learning to Steer.
XIII. Peculiarities of Aeroplane Power
Pressure of the Wind--How to Determine Upon
Power--Why Speed Is Required--Bird find Flying
Machine Areas.
XIV. About Wind Currents, Etc.
Uncertainty of Direct Force--Trouble With Gusty
Currents--Why Bird Action Is Imitated.
XV. The Element of Danger
Risk Small Under Proper Conditions--Two Fields
of Safety--Lessons in Recent Accidents.
XVI. Radical Changes Being Made
Results of Recent Experiments--New Dimensions
--Increased Speed--The One Governing Rule.
XVII. Some of the New Designs
ù Automatic Control of Plane Stability--Inventor
Herring's Devices--Novel Ideas of Students.
XVIII. Demand for Flying Machines
Wonderful Results in a Year--Factories Over-
crowded with Orders.
XIX. Law of the Airship
Rights of Property Owners--Some Legal
Peculiarities--Danger of Trespass.
XX. Soaring Flight
XXI. Flying Machines vs. Balloons
XXII. Problems of Aerial Fligh
XXIII. Amateurs May Use Wright Patents
XXIV. Hints on Propeller Construction
XXV. New Motors and Devices
XXVI. Monoplanes, Triplanes, Multiplanes
XXVII. Records of Various Kinds

FLYING MACHINES: CONSTRUCTION and OPERATION

CHAPTER I.

EVOLUTION OF TWO-SURFACE FLYING MACHINE.

By Octave Chanute.

I am asked to set forth the development of the "two-
surface" type of flying machine which is now used with
modifications by Wright Brothers, Farman, [1]Delagrange,
Herring and others.

[1] Now dead.

This type originated with Mr. F. H. Wenham, who
patented it in England in 1866 (No. 1571), taking out
provisional papers only. In the abridgment of British
patent Aeronautical Specifications (1893) it is described
as follows:

"Two or more aeroplanes are arranged one above the
other, and support a framework or car containing the
motive power. The aeroplanes are made of silk or canvas
stretched on a frame by wooden rods or steel ribs.
When manual power is employed the body is placed
horizontally, and oars or propellers are actuated by the
arms or legs.

"A start may be obtained by lowering the legs and
running down hill or the machine may be started from
a moving carriage. One or more screw propellers may
be applied for propelling when steam power is employed.

On June 27, 1866, Mr. Wenham read before the
"Aeronautical Society of Great Britain," then recently
organized, the ablest paper ever presented to that society, and
thereby breathed into it a spirit which has continued to
this day. In this paper he described his observations of
birds, discussed the laws governing flight as to the
surfaces and power required both with wings and screws,
and he then gave an account of his own experiments with
models and with aeroplanes of sufficient size to carry
the weight of a man.

Second Wenham Aeroplane.

His second aeroplane was sixteen feet from tip to tip.
A trussed spar at the bottom carried six superposed
bands of thin holland fabric fifteen inches wide, connected
with vertical webs of holland two feet apart, thus
virtually giving a length of wing of ninety-six feet and
one hundred and twenty square feet of supporting surface.
The man was placed horizontally on a base board
beneath the spar. This apparatus when tried in the wind
was found to be unmanageable by reason of the fluttering
motions of the fabric, which was insufficiently stiffened
with crinoline steel, but Mr. Wenham pointed out that
this in no way invalidated the principle of the apparatus,
which was to obtain large supporting surfaces without
increasing unduly the leverage and consequent weight
of spar required, by simply superposing the surfaces.

This principle is entirely sound and it is surprising that
it is, to this day, not realized by those aviators who are
hankering for monoplanes.

Experiments by Stringfellow.

The next man to test an apparatus with superposed
surfaces was Mr. Stringfellow, who, becoming much impressed
with Mr. Wenham's proposal, produced a largish
model at the exhibition of the Aeronautical Society in
1868. It consisted of three superposed surfaces aggregating 28
square feet and a tail of 8 square feet more.
The weight was under 12 pounds and it was driven by a
central propeller actuated by a steam engine overestimated
at one-third of a horsepower. It ran suspended
to a wire on its trials but failed of free flight, in
consequence of defective equilibrium. This apparatus has
since been rebuilt and is now in the National Museum
of the Smithsonian Institution at Washington.
Linfield's Unsuccessful Efforts.

In 1878 Mr. Linfield tested an apparatus in England
consisting of a cigar-shaped car, to which was attached
on each side frames five feet square, containing each
twenty-five superposed planes of stretched and varnished
linen eighteen inches wide, and only two inches apart,
thus reminding one of a Spanish donkey with panniers.
The whole weighed two hundred and forty pounds. This
was tested by being mounted on a flat car behind a
locomotive going 40 miles an hour. When towed by a line
fifteen feet long the apparatus rose only a little from the
car and exhibited such unstable equilibrium that the
experiment was not renewed. The lift was only about one-
third of what it would have been had the planes been
properly spaced, say their full width apart, instead of
one-ninth as erroneously devised.

Renard's "Dirigible Parachute."

In 1889 Commandant Renard, the eminent superintendent
of the French Aeronautical Department, exhibited
at the Paris Exposition of that year, an apparatus
experimented with some years before, which he termed
a "dirigible parachute." It consisted of an oviform body
to which were pivoted two upright slats carrying above
the body nine long superposed flat blades spaced about
one-third of their width apart. When this apparatus
was properly set at an angle to the longitudinal axis of
the body and dropped from a balloon, it travelled back
against the wind for a considerable distance before
alighting. The course could be varied by a rudder. No
practical application seems to have been made of this
device by the French War Department, but Mr. J. P.
Holland, the inventor of the submarine boat which bears
his name, proposed in 1893 an arrangement of pivoted
framework attached to the body of a flying machine
which combines the principle of Commandant Renard
with the curved blades experimented with by Mr. Phillips,
now to be noticed, with the addition of lifting screws
inserted among the blades.

Phillips Fails on Stability Problem.

In 1893 Mr. Horatio Phillips, of England, after some
very interesting experiments with various wing sections,
from which he deduced conclusions as to the shape of
maximum lift, tested an apparatus resembling a Venetian
blind which consisted of fifty wooden slats of
peculiar shape, 22 feet long, one and a half inches wide,
and two inches apart, set in ten vertical upright boards.
All this was carried upon a body provided with three
wheels. It weighed 420 pounds and was driven at 40
miles an hour on a wooden sidewalk by a steam engine
of nine horsepower which actuated a two-bladed screw.
The lift was satisfactory, being perhaps 70 pounds per
horsepower, but the equilibrium was quite bad and the
experiments were discontinued. They were taken up
again in 1904 with a similar apparatus large enough to
carry a passenger, but the longitudinal equilibrium was
found to be defective. Then in 1907 a new machine was
tested, in which four sets of frames, carrying similar sets
of slat "sustainers" were inserted, and with this
arrangement the longitudinal stability was found to be very
satisfactory. The whole apparatus, with the operator,
weighed 650 pounds. It flew about 200 yards when
driven by a motor of 20 to 22 h.p. at 30 miles an hour,
thus exhibiting a lift of about 32 pounds per h.p., while
it will be remembered that the aeroplane of Wright
Brothers exhibits a lifting capacity of 50 pounds to
the h.p.

Hargrave's Kite Experiments.

After experimenting with very many models and
building no less than eighteen monoplane flying model
machines, actuated by rubber, by compressed air and by
steam, Mr. Lawrence Hargrave, of Sydney, New South
Wales, invented the cellular kite which bears his name
and made it known in a paper contributed to the Chicago
Conference on Aerial Navigation in 1893, describing
several varieties. The modern construction is well
known, and consists of two cells, each of superposed surfaces
with vertical side fins, placed one behind the other
and connected by a rod or frame. This flies with great
steadiness without a tail. Mr. Hargrave's idea was to
use a team of these kites, below which he proposed to
suspend a motor and propeller from which a line would
be carried to an anchor in the ground. Then by actuating
the propeller the whole apparatus would move
forward, pick up the anchor and fly away. He said:
"The next step is clear enough, namely, that a flying
machine with acres of surface can be safely got under
way or anchored and hauled to the ground by means of
the string of kites."

The first tentative experiments did not result well and
emphasized the necessity for a light motor, so that Mr.
Hargrave has since been engaged in developing one, not
having convenient access to those which have been produced
by the automobile designers and builders.

Experiments With Glider Model.

And here a curious reminiscence may be indulged in.
In 1888 the present writer experimented with a two-cell
gliding model, precisely similar to a Hargrave kite, as
will be confirmed by Mr. Herring. It was frequently
tested by launching from the top of a three-story house
and glided downward very steadily in all sorts of breezes,
but the angle of descent was much steeper than that of
birds, and the weight sustained per square foot was less
than with single cells, in consequence of the lesser support
afforded by the rear cell, which operated upon air
already set in motion downward by the front cell, so
nothing more was done with it, for it never occurred to
the writer to try it as a kite and he thus missed the
distinction which attaches to Hargrave's name.

Sir Hiram Maxim also introduced fore and aft superposed
surfaces in his wondrous flying machine of 1893,
but he relied chiefly for the lift upon his main large surface
and this necessitated so many guys, to prevent distortion,
as greatly to increase the head resistance and
this, together with the unstable equilibrium, made it
evident that the design of the machine would have to
be changed.

How Lilienthal Was Killed.

In 1895, Otto Lilienthal, the father of modern aviation,
the man to whose method of experimenting almost all
present successes are due, after making something like
two thousand glides with monoplanes, added a superposed
surface to his apparatus and found the control of
it much improved. The two surfaces were kept apart
by two struts or vertical posts with a few guy wires, but
the connecting joints were weak and there was nothing
like trussing. This eventually cost his most useful life.
Two weeks before that distressing loss to science, Herr
Wilhelm Kress, the distinguished and veteran aviator
of Vienna, witnessed a number of glides by Lilienthal
with his double-decked apparatus. He noticed that it
was much wracked and wobbly and wrote to me after
the accident: "The connection of the wings and the
steering arrangement were very bad and unreliable. I
warned Herr Lilienthal very seriously. He promised
me that he would soon put it in order, but I fear that he
did not attend to it immediately."

In point of fact, Lilienthal had built a new machine,
upon a different principle, from which he expected great
results, and intended to make but very few more flights
with the old apparatus. He unwisely made one too
many and, like Pilcher, was the victim of a distorted
apparatus. Probably one of the joints of the struts
gave way, the upper surface blew back and Lilienthal,
who was well forward on the lower surface, was pitched
headlong to destruction.

Experiments by the Writer.

In 1896, assisted by Mr. Herring and Mr. Avery, I
experimented with several full sized gliding machines,
carrying a man. The first was a Lilienthal monoplane
which was deemed so cranky that it was discarded after
making about one hundred glides, six weeks before
Lilienthal's accident. The second was known as the
multiple winged machine and finally developed into five
pairs of pivoted wings, trussed together at the front and
one pair in the rear. It glided at angles of descent of
10 or 11 degrees or of one in five, and this was deemed
too steep. Then Mr. Herring and myself made computations
to analyze the resistances. We attributed much
of them to the five front spars of the wings and on a
sheet of cross-barred paper I at once drew the design for
a new three-decked machine to be built by Mr. Herring.

Being a builder of bridges, I trussed these surfaces
together, in order to obtain strength and stiffness. When
tested in gliding flight the lower surface was found too
near the ground. It was taken off and the remaining
apparatus now consisted of two surfaces connected together
by a girder composed of vertical posts and diagonal
ties, specifically known as a "Pratt truss." Then
Mr. Herring and Mr. Avery together devised and put
on an elastic attachment to the tail. This machine
proved a success, it being safe and manageable. Over
700 glides were made with it at angles of descent of 8
to 10 degrees, or one in six to one in seven.

First Proposed by Wenham.

The elastic tail attachment and the trussing of the
connecting frame of the superposed wings were the only
novelties in this machine, for the superposing of the
surfaces had first been proposed by Wenham, but in
accordance with the popular perception, which bestows
all the credit upon the man who adds the last touch
making for success to the labors of his predecessors, the
machine has since been known by many persons as the
"Chanute type" of gliders, much to my personal gratification.

It has since been improved in many ways. Wright
Brothers, disregarding the fashion which prevails among
birds, have placed the tail in front of their apparatus and
called it a front rudder, besides placing the operator in
horizontal position instead of upright, as I did; and also
providing a method of warping the wings to preserve
equilibrium. Farman and Delagrange, under the very
able guidance and constructive work of Voisin brothers,
then substituted many details, including a box tail for
the dart-like tail which I used. This may have increased
the resistance, but it adds to the steadiness. Now the
tendency in France seems to be to go back to the monoplane.

Monoplane Idea Wrong.

The advocates of the single supporting surface are
probably mistaken. It is true that a single surface
shows a greater lift per square foot than superposed
surfaces for a given speed, but the increased weight due
to leverage more than counterbalances this advantage by
requiring heavy spars and some guys. I believe that
the future aeroplane dynamic flier will consist of superposed
surfaces, and, now that it has been found that by
imbedding suitably shaped spars in the cloth the head
resistance may be much diminished, I see few objections
to superposing three, four or even five surfaces properly
trussed, and thus obtaining a compact, handy, manageable
and comparatively light apparatus.[2]

[2] Aeronautics.

CHAPTER II.

THEORY, DEVELOPMENT, AND USE.

While every craft that navigates the air is an airship,
all airships are not flying machines. The balloon,
for instance, is an airship, but it is not what is known
among aviators as a flying machine. This latter term
is properly used only in referring to heavier-than-air
machines which have no gas-bag lifting devices, and are made to
really fly by the application of engine propulsion.

Mechanical Birds.

All successful flying machines--and there are a number
of them--are based on bird action. The various
designers have studied bird flight and soaring, mastered
its technique as devised by Nature, and the modern flying
machine is the result. On an exaggerated, enlarged
scale the machines which are now navigating the air
are nothing more nor less than mechanical birds.

Origin of the Aeroplane.

Octave Chanute, of Chicago, may well be called "the
developer of the flying machine." Leaving balloons and
various forms of gas-bags out of consideration, other
experimenters, notably Langley and Lilienthal, antedated
him in attempting the navigation of the air on
aeroplanes, or flying machines, but none of them were
wholly successful, and it remained for Chanute to demonstrate
the practicability of what was then called the
gliding machine. This term was adopted because the
apparatus was, as the name implies, simply a gliding
machine, being without motor propulsion, and intended
solely to solve the problem of the best form of
construction. The biplane, used by Chanute in 1896, is
still the basis of most successful flying machines, the
only radical difference being that motors, rudders, etc.,
have been added.

Character of Chanute's Experiments.

It was the privilege of the author of this book to be
Mr. Chanute's guest at Millers, Indiana, in 1896, when,
in collaboration with Messrs. Herring and Avery, he was
conducting the series of experiments which have since
made possible the construction of the modern flying
machine which such successful aviators as the Wright
brothers and others are now using. It was a wild
country, much frequented by eagles, hawks, and similar
birds. The enthusiastic trio, Chanute, Herring and
Avery, would watch for hours the evolutions of some
big bird in the air, agreeing in the end on the verdict,
"When we master the principle of that bird's soaring
without wing action, we will have come close to solving
the problem of the flying machine."

Aeroplanes of various forms were constructed by Mr.
Chanute with the assistance of Messrs. Herring and
Avery until, at the time of the writer's visit, they had
settled upon the biplane, or two-surface machine. Mr.
Herring later equipped this with a rudder, and made
other additions, but the general idea is still the basis of
the Wright, Curtiss, and other machines in which, by
the aid of gasolene motors, long flights have been made.

Developments by the Wrights.

In 1900 the Wright brothers, William and Orville, who were then
in the bicycle business in Dayton, Ohio,
became interested in Chanute's experiments and
communicated with him. The result was that the Wrights
took up Chanute's ideas and developed them further,
making many additions of their own, one of which was
the placing of a rudder in front, and the location of the
operator horizontally on the machine, thus diminishing
by four-fifths the wind resistance of the man's body.
For three years the Wrights experimented with the
glider before venturing to add a motor, which was not
done until they had thoroughly mastered the control of
their movements in the air.

Limits of the Flying Machine.

In the opinion of competent experts it is idle to look
for a commercial future for the flying machine. There
is, and always will be, a limit to its carrying capacity
which will prohibit its employment for passenger or
freight purposes in a wholesale or general way. There
are some, of course, who will argue that because a
machine will carry two people another may be constructed
that will carry a dozen, but those who make
this contention do not understand the theory of weight
sustentation in the air; or that the greater the load the
greater must be the lifting power (motors and plane
surface), and that there is a limit to these--as will be
explained later on--beyond which the aviator cannot go.

Some Practical Uses.

At the same time there are fields in which the flying
machine may be used to great advantage. These are:

Sports--Flying machine races or flights will always
be popular by reason of the element of danger. It is
a strange, but nevertheless a true proposition, that it is
this element which adds zest to all sporting events.

Scientific--For exploration of otherwise inaccessible
regions such as deserts, mountain tops, etc.

Reconnoitering--In time of war flying machines may
be used to advantage to spy out an enemy's encampment,
ascertain its defenses, etc.

CHAPTER III.

MECHANICAL BIRD ACTION

In order to understand the theory of the modern flying
machine one must also understand bird action and wind
action. In this connection the following simple experiment
will be of interest:

Take a circular-shaped bit of cardboard, like the lid of
a hat box, and remove the bent-over portion so as to
have a perfectly flat surface with a clean, sharp edge.
Holding the cardboard at arm's length, withdraw your
hand, leaving the cardboard without support. What is
the result? The cardboard, being heavier than air, and
having nothing to sustain it, will fall to the ground.
Pick it up and throw it, with considerable force, against
the wind edgewise. What happens? Instead of falling
to the ground, the cardboard sails along on the wind,
remaining afloat so long as it is in motion. It seeks
the ground, by gravity, only as the motion ceases, and
then by easy stages, instead of dropping abruptly as in
the first instance.

Here we have a homely, but accurate illustration of
the action of the flying machine. The motor does for
the latter what the force of your arm does for the cardboard--
imparts a motion which keeps it afloat. The
only real difference is that the motion given by the
motor is continuous and much more powerful than that
given by your arm. The action of the latter is limited
and the end of its propulsive force is reached within a
second or two after it is exerted, while the action of the
motor is prolonged.

Another Simple Illustration.

Another simple means of illustrating the principle of
flying machine operation, so far as sustentation and the
elevation and depression of the planes is concerned, is
explained in the accompanying diagram.

A is a piece of cardboard about 2 by 3 inches in size.
B is a piece of paper of the same size pasted to one edge
of A. If you bend the paper to a curve, with convex
side up and blow across it as shown in Figure C, the
paper will rise instead of being depressed. The dotted
lines show that the air is passing over the top of the
curved paper and yet, no matter how hard you may
blow, the effect will be to elevate the paper, despite the
fact that the air is passing over, instead of under the
curved surface.

In Figure D we have an opposite effect. Here the
paper is in a curve exactly the reverse of that shown in
Figure C, bringing the concave side up. Now if you
will again blow across the surface of the card the action
of the paper will be downward--it will be impossible to
make it rise. The harder you blow the greater will be
the downward movement.

Principle In General Use.

This principle is taken advantage of in the construction
of all successful flying machines. Makers of monoplanes
and biplanes alike adhere to curved bodies, with
the concave surface facing downward. Straight planes
were tried for a time, but found greatly lacking in the
power of sustentation. By curving the planes, and placing
the concave surface downward, a sort of inverted bowl
is formed in which the air gathers and exerts a buoyant
effect. Just what the ratio of the curve should be is a
matter of contention. In some instances one inch to the
foot is found to be satisfactory; in others this is doubled,
and there are a few cases in which a curve of as much as
3 inches to the foot has been used.

Right here it might be well to explain that the word
"plane" applied to flying machines of modern construction
is in reality a misnomer. Plane indicates a flat,
level surface. As most successful flying machines have
curved supporting surfaces it is clearly wrong to speak
of "planes," or "aeroplanes." Usage, however, has made
the terms convenient and, as they are generally accepted
and understood by the public, they are used in like manner
in this volume.

Getting Under Headway.

A bird, on first rising from the ground, or beginning
its flight from a tree, will flap its wings to get under
headway. Here again we have another illustration of
the manner in which a flying machine gets under headway--
the motor imparts the force necessary to put the
machine into the air, but right here the similarity ceases.
If the machine is to be kept afloat the motor must be
kept moving. A flying machine will not sustain itself;
it will not remain suspended in the air unless it is
under headway. This is because it is heavier than air,
and gravity draws it to the ground.

Puzzle in Bird Soaring.

But a bird, which is also heavier than air, will remain
suspended, in a calm, will even soar and move in a
circle, without apparent movement of its wings. This
is explained on the theory that there are generally vertical
columns of air in circulation strong enough to sustain
a bird, but much too weak to exert any lifting power
on a flying machine, It is easy to understand how a
bird can remain suspended when the wind is in action,
but its suspension in a seeming dead calm was a puzzle
to scientists until Mr. Chanute advanced the proposition
of vertical columns of air.

Modeled Closely After Birds.

So far as possible, builders of flying machines have
taken what may be called "the architecture" of birds as
a model. This is readily noticeable in the form of
construction. When a bird is in motion its wings (except
when flapping) are extended in a straight line at right
angles to its body. This brings a sharp, thin edge
against the air, offering the least possible surface for
resistance, while at the same time a broad surface for
support is afforded by the flat, under side of the wings.
Identically the same thing is done in the construction of
the flying machine.

Note, for instance, the marked similarity in form as
shown in the illustration in Chapter II. Here A is the
bird, and B the general outline of the machine. The
thin edge of the plane in the latter is almost a duplicate
of that formed by the outstretched wings of the bird,
while the rudder plane in the rear serves the same purpose
as the bird's tail.

CHAPTER IV.

VARIOUS FORMS OF FLYING MACHINES.

There are three distinct and radically different forms
of flying machines. These are:

Aeroplanes, helicopters and ornithopers.

Of these the aeroplane takes precedence and is used
almost exclusively by successful aviators, the helicopters
and ornithopers having been tried and found lacking in
some vital features, while at the same time in some
respects the helicopter has advantages not found in the
aeroplane.

What the Helicopter Is.

The helicopter gets its name from being fitted with
vertical propellers or helices (see illustration) by the
action of which the machine is raised directly from the
ground into the air. This does away with the necessity
for getting the machine under a gliding headway before
it floats, as is the case with the aeroplane, and consequently
the helicopter can be handled in a much smaller
space than is required for an aeroplane. This, in many
instances, is an important advantage, but it is the only
one the helicopter possesses, and is more than overcome
by its drawbacks. The most serious of these is that the
helicopter is deficient in sustaining capacity, and requires
too much motive power.

Form of the Ornithopter.

The ornithopter has hinged planes which work like
the wings of a bird. At first thought this would seem
to be the correct principle, and most of the early experimenters
conducted their operations on this line. It
is now generally understood, however, that the bird in
soaring is in reality an aeroplane, its extended wings
serving to sustain, as well as propel, the body. At any
rate the ornithoper has not been successful in aviation,
and has been interesting mainly as an ingenious toy.
Attempts to construct it on a scale that would permit
of its use by man in actual aerial flights have been far
from encouraging.

Three Kinds of Aeroplanes.

There are three forms of aeroplanes, with all of which
more or less success has been attained. These are:

The monoplane, a one-surfaced plane, like that used
by Bleriot.

The biplane, a two-surfaced plane, now used by the
Wrights, Curtiss, Farman, and others.

The triplane, a three-surfaced plane This form is
but little used, its only prominent advocate at present
being Elle Lavimer, a Danish experimenter, who has not
thus far accomplished much.

Whatever of real success has been accomplished in
aviation may be credited to the monoplane and biplane,
with the balance in favor of the latter. The monoplane
is the more simple in construction and, where weight-
sustaining capacity is not a prime requisite, may
probably be found the most convenient. This opinion is
based on the fact that the smaller the surface of the
plane the less will be the resistance offered to the air,
and the greater will be the speed at which the machine
may be moved. On the other hand, the biplane has a
much greater plane surface (double that of a monoplane
of the same size) and consequently much greater weight-
carrying capacity.

Differences in Biplanes.

While all biplanes are of the same general construction
so far as the main planes are concerned, each aviator
has his own ideas as to the "rigging."

Wright, for instance, places a double horizontal rudder
in front, with a vertical rudder in the rear. There
are no partitions between the main planes, and the
bicycle wheels used on other forms are replaced by skids.

Voisin, on the contrary, divides the main planes with
vertical partitions to increase stability in turning; uses
a single-plane horizontal rudder in front, and a big box-
tail with vertical rudder at the rear; also the bicycle
wheels.

Curtiss attaches horizontal stabilizing surfaces to the
upper plane; has a double horizontal rudder in front,
with a vertical rudder and horizontal stabilizing surfaces
in rear. Also the bicycle wheel alighting gear.

CHAPTER V.

CONSTRUCTING A GLIDING MACHINE.

First decide upon the kind of a machine you want--
monoplane, biplane, or triplane. For a novice the biplane
will, as a rule, be found the most satisfactory as
it is more compact and therefore the more easily handled.
This will be easily understood when we realize that the
surface of a flying machine should be laid out in proportion
to the amount of weight it will have to sustain.
The generally accepted rule is that 152 square feet of
surface will sustain the weight of an average-sized man,
say 170 pounds. Now it follows that if these 152 square
feet of surface are used in one plane, as in the monoplane,
the length and width of this plane must be greater
than if the same amount of surface is secured by using
two planes--the biplane. This results in the biplane
being more compact and therefore more readily manipulated
than the monoplane, which is an important item
for a novice.

Glider the Basis of Success.

Flying machines without motors are called gliders. In
making a flying machine you first construct the glider.
If you use it in this form it remains a glider. If you
install a motor it becomes a flying machine. You must
have a good glider as the basis of a successful flying
machine.

It will be well for the novice, the man who has never
had any experience as an aviator, to begin with a glider
and master its construction and operation before he
essays the more pretentious task of handling a fully-
equipped flying machine. In fact, it is essential that he
should do so.

Plans for Handy Glider.

A glider with a spread (advancing edge) of 20 feet, and
a breadth or depth of 4 feet, will be about right to begin
with. Two planes of this size will give the 152 square
yards of surface necessary to sustain a man's weight.
Remember that in referring to flying machine measurements
"spread" takes the place of what would ordinarily
be called "length," and invariably applies to the long
or advancing edge of the machine which cuts into the air.
Thus, a glider is spoken of as being 20 feet spread, and
4 feet in depth. So far as mastering the control of the
machine is concerned, learning to balance one's self in
the air, guiding the machine in any desired direction by
changing the position of the body, etc., all this may be
learned just as readily, and perhaps more so, with a 20-
foot glider than with a larger apparatus.

Kind of Material Required.

There are three all-important features in flying machine
construction, viz.: lightness, strength and extreme
rigidity. Spruce is the wood generally used for glider
frames. Oak, ash and hickory are all stronger, but they
are also considerably heavier, and where the saving of
weight is essential, the difference is largely in favor of
spruce. This will be seen in the following table:

Weight Tensile Compressive
per cubic ft. Strength Strength
Wood in lbs. lbs. per sq. in. lbs. per sq in.
Hickory 53 12,000 8,500
Oak 50 12,000 9,000
Ash 38 12,000 6,000
Walnut 38 8,000 6,000
Spruce 25 8,000 5,000
Pine 25 5,000 4,500

Considering the marked saving in weight spruce has
a greater percentage of tensile strength than any of the
other woods. It is also easier to find in long, straight-
grained pieces free from knots, and it is this kind only
that should be used in flying machine construction.

You will next need some spools or hanks of No. 6
linen shoe thread, metal sockets, a supply of strong
piano wire, a quantity of closely-woven silk or cotton
cloth, glue, turnbuckles, varnish, etc.

Names of the Various Parts.

The long strips, four in number, which form the front
and rear edges of the upper and lower frames, are called
the horizontal beams. These are each 20 feet in length.
These horizontal beams are connected by upright strips,
4 feet long, called stanchions. There are usually 12 of
these, six on the front edge, and six on the rear. They
serve to hold the upper plane away from the lower one.
Next comes the ribs. These are 4 feet in length (projecting
for a foot over the rear beam), and while intended
principally as a support to the cloth covering of
the planes, also tend to hold the frame together in a
horizontal position just as the stanchions do in the vertical.
There are forty-one of these ribs, twenty-one on
the upper and twenty on the lower plane. Then come
the struts, the main pieces which join the horizontal
beams. All of these parts are shown in the illustrations,
reference to which will make the meaning of the
various names clear.

Quantity and Cost of Material.

For the horizontal beams four pieces of spruce, 20 feet
long, 1 1/2 inches wide and 3/4 inch thick are necessary.
These pieces must be straight-grain, and absolutely free
from knots. If it is impossible to obtain clear pieces
of this length, shorter ones may be spliced, but this is
not advised as it adds materially to the weight. The
twelve stanchions should be 4 feet long and 7/8 inch in
diameter and rounded in form so as to offer as little
resistance as possible to the wind. The struts, there
are twelve of them, are 3 feet long by 11/4 x 1/2 inch. For
a 20-foot biplane about 20 yards of stout silk or unbleached
muslin, of standard one yard width, will be
needed. The forty-one ribs are each 4 feet long, and
1/2 inch square. A roll of No. 12 piano wire, twenty-four
sockets, a package of small copper tacks, a pot of glue,
and similar accessories will be required. The entire
cost of this material should not exceed $20. The wood
and cloth will be the two largest items, and these should
not cost more than $10. This leaves $10 for the varnish,
wire, tacks, glue, and other incidentals. This estimate
is made for cost of materials only, it being taken for
granted that the experimenter will construct his own
glider. Should the services of a carpenter be required
the total cost will probably approximate $60 or $70.

Application of the Rudders.

The figures given also include the expense of rudders,
but the details of these have not been included as the
glider is really complete without them. Some of the best
flights the writer ever saw were made by Mr. A. M. Herring in a
glider without a rudder, and yet there can
be no doubt that a rudder, properly proportioned and
placed, especially a rear rudder, is of great value to the
aviator as it keeps the machine with its head to the
wind, which is the only safe position for a novice. For
initial educational purposes, however, a rudder is not
essential as the glides will, or should, be made on level
ground, in moderate, steady wind currents, and at a
modest elevation. The addition of a rudder, therefore,
may well be left until the aviator has become reasonably
expert in the management of his machine.

Putting the Machine Together.

Having obtained the necessary material, the first move
is to have the rib pieces steamed and curved. This curve
may be slight, about 2 inches for the 4 feet. While
this is being done the other parts should be carefully
rounded so the square edges will be taken off. This
may be done with sand paper. Next apply a coat of
shellac, and when dry rub it down thoroughly with fine
sand paper. When the ribs are curved treat them in
the same way.

Lay two of the long horizontal frame pieces on the
floor 3 feet apart. Between these place six of the strut
pieces. Put one at each end, and each 4 1/2 feet put
another, leaving a 2-foot space in the center. This will
give you four struts 4 1/2 feet apart, and two in the center
2 feet apart, as shown in the illustration. This makes
five rectangles. Be sure that the points of contact are
perfect, and that the struts are exactly at right angles
with the horizontal frames. This is a most important
feature because if your frame "skews" or twists you
cannot keep it straight in the air. Now glue the ends
of the struts to the frame pieces, using plenty of glue,
and nail on strips that will hold the frame in place while
the glue is drying. The next day lash the joints together
firmly with the shoe thread, winding it as you would to
mend a broken gun stock, and over each layer put a
coating of glue. This done, the other frame pieces and
struts may be treated in the same way, and you will thus
get the foundations for the two planes.

Another Way of Placing Struts.

In the machines built for professional use a stronger
and more certain form of construction is desired. This
is secured by the placing the struts for the lower plane
under the frame piece, and those for the upper plane
over it, allowing them in each instance to come out flush
with the outer edges of the frame pieces. They are then
securely fastened with a tie plate or clamp which passes
over the end of the strut and is bound firmly against
the surface of the frame piece by the eye bolts of the
stanchion sockets.

Placing the Rib Pieces.

Take one of the frames and place on it the ribs, with
the arched side up, letting one end of the ribs come
flush with the front edge of the forward frame, and the
other end projecting about a foot beyond the rear frame.
The manner of fastening the ribs to the frame pieces is
optional. In some cases they are lashed with shoe
thread, and in others clamped with a metal clamp fastened
with 1/2-inch wood screws. Where clamps and
screws are used care should be taken to make slight
holes in the wood with an awl before starting the screws
so as to lessen any tendency to split the wood. On the
top frame, twenty-one ribs placed one foot apart will be
required. On the lower frame, because of the opening
left for the operator's body, you will need only twenty.

Joining the Two Frames.

The two frames must now be joined together. For this
you will need twenty-four aluminum or iron sockets
which may be purchased at a foundry or hardware shop.
These sockets, as the name implies, provide a receptacle
in which the end of a stanchion is firmly held, and have
flanges with holes for eye-bolts which hold them firmly
to the frame pieces, and also serve to hold the guy wires.
In addition to these eye-bolt holes there are two others
through which screws are fastened into the frame pieces.
On the front frame piece of the bottom plane place six
sockets, beginning at the end of the frame, and locating
them exactly opposite the struts. Screw the sockets into
position with wood screws, and then put the eye-bolts in
place. Repeat the operation on the rear frame. Next
put the sockets for the upper plane frame in place.

You are now ready to bring the two planes together.
Begin by inserting the stanchions in the sockets in the
lower plane. The ends may need a little rubbing with
sandpaper to get them into the sockets, but care must
be taken to have them fit snugly. When all the stanchions
are in place on the lower plane, lift the upper
plane into position, and fit the sockets over the upper
ends of the stanchions.

Trussing with Guy Wires.

The next move is to "tie" the frame together rigidly
by the aid of guy wires. This is where the No. 12 piano
wire comes in. Each rectangle formed by the struts and
stanchions with the exception of the small center one,
is to be wired separately as shown in the illustration.
At each of the eight corners forming the rectangle the
ring of one of the eye-bolts will be found. There are
two ways of doing this "tieing," or trussing. One is to
run the wires diagonally from eye-bolt to eye-bolt, depending
upon main strength to pull them taut enough,
and then twist the ends so as to hold. The other is to
first make a loop of wire at each eye-bolt, and connect
these loops to the main wires with turn-buckles. This
latter method is the best, as it admits of the tension being
regulated by simply turning the buckle so as to draw
the ends of the wire closer together. A glance at the
illustration will make this plain, and also show how the
wires are to be placed. The proper degree of tension
may be determined in the following manner:

After the frame is wired place each end on a saw-horse
so as to lift the entire frame clear of the work-shop
floor. Get under it, in the center rectangle and, grasping
the center struts, one in each hand, put your entire
weight on the structure. If it is properly put together
it will remain rigid and unyielding. Should it sag ever
so slightly the tension of the wires must be increased
until any tendency to sag, no matter how slight it may
be, is overcome.

Putting on the Cloth.

We are now ready to put on the cloth covering which
holds the air and makes the machine buoyant. The kind
of material employed is of small account so long as it is
light, strong, and wind-proof, or nearly so. Some aviators
use what is called rubberized silk, others prefer
balloon cloth. Ordinary muslin of good quality, treated
with a coat of light varnish after it is in place, will answer
all the purposes of the amateur.

Cut the cloth into strips a little over 4 feet in length.
As you have 20 feet in width to cover, and the cloth is
one yard wide, you will need seven strips for each plane,
so as to allow for laps, etc. This will give you fourteen
strips. Glue the end of each strip around the front
horizontal beams of the planes, and draw each strip back,
over the ribs, tacking the edges to the ribs as you go
along, with small copper or brass tacks. In doing this
keep the cloth smooth and stretched tight. Tacks should
also be used in addition to the glue, to hold the cloth to
the horizontal beams.

Next, give the cloth a coat of varnish on the clear, or
upper side, and when this is dry your glider will be
ready for use.

Reinforcing the Cloth.

While not absolutely necessary for amateur purposes,
reinforcement of the cloth, so as to avoid any tendency
to split or tear out from wind-pressure, is desirable. One
way of doing this is to tack narrow strips of some
heavier material, like felt, over the cloth where it laps
on the ribs. Another is to sew slips or pockets in the
cloth itself and let the ribs run through them. Still another
method is to sew 2-inch strips (of the same material
as the cover) on the cloth, placing them about one
yard apart, but having them come in the center of each
piece of covering, and not on the laps where the various
pieces are joined.

Use of Armpieces.

Should armpieces be desired, aside from those afforded
by the center struts, take two pieces of spruce, 3 feet
long, by 1 x 1 3/4 inches, and bolt them to the front and
rear beams of the lower plane about 14 inches apart.
These will be more comfortable than using the struts,
as the operator will not have to spread his arms so
much. In using the struts the operator, as a rule, takes
hold of them with his hands, while with the armpieces,
as the name implies, he places his arms over them, one
of the strips coming under each armpit.

Frequently somebody asks why the ribs should be
curved. The answer is easy. The curvature tends to
direct the air downward toward the rear and, as the air
is thus forced downward, there is more or less of an impact
which assists in propelling the aeroplane upwards.

CHAPTER VI.

LEARNING TO FLY.

Don't be too ambitious at the start. Go slow, and
avoid unnecessary risks. At its best there is an element
of danger in aviation which cannot be entirely eliminated, but it
may be greatly reduced and minimized by
the use of common sense.

Theoretically, the proper way to begin a glide is from
the top of an incline, facing against the wind, so that
the machine will soar until the attraction of gravitation
draws it gradually to the ground. This is the manner in
which experienced aviators operate, but it must be kept
in mind that these men are experts. They understand
air currents, know how to control the action and direction
of their machines by shifting the position of their
bodies, and by so doing avoid accidents which would be
unavoidable by a novice.

Begin on Level Ground.

Make your first flights on level ground, having a couple
of men to assist you in getting the apparatus under
headway. Take your position in the center rectangle,
back far enough to give the forward edges of the glider
an inclination to tilt upward very slightly. Now start
and run forward at a moderately rapid gait, one man at
each end of the glider assisting you. As the glider cuts
into the air the wind will catch under the uplifted edges
of the curved planes, and buoy it up so that it will rise
in the air and take you with it. This rise will not be
great, just enough to keep you well clear of the ground.
Now project your legs a little to the front so as to shift
the center of gravity a trifle and bring the edges of the
glider on an exact level with the atmosphere. This, with
the momentum acquired in the start, will keep the machine
moving forward for some distance.

Effect of Body Movements.

When the weight of the body is slightly back of the
center of gravity the edges of the advancing planes are
tilted slightly upward. The glider in this position acts
as a scoop, taking in the air which, in turn, lifts it off the
ground. When a certain altitude is reached--this varies
with the force of the wind--the tendency to a forward
movement is lost and the glider comes to the ground.
It is to prolong the forward movement as much as possible
that the operator shifts the center of gravity slightly,
bringing the apparatus on an even keel as it were by
lowering the advancing edges. This done, so long as
there is momentum enough to keep the glider moving, it
will remain afloat.

If you shift your body well forward it will bring the
front edges of the glider down, and elevate the rear ones.
In this way the air will be "spilled" out at the rear, and,
having lost the air support or buoyancy, the glider comes
down to the ground. A few flights will make any ordinary
man proficient in the control of his apparatus by his
body movements, not only as concerns the elevating and
depressing of the advancing edges, but also actual steering. You
will quickly learn, for instance, that, as the
shifting of the bodily weight backwards and forwards
affects the upward and downward trend of the planes, so
a movement sideways--to the left or the right--affects
the direction in which the glider travels.

Ascends at an Angle.

In ascending, the glider and flying machine, like the
bird, makes an angular, not a vertical flight. Just what
this angle of ascension may be is difficult to determine.
It is probable and in fact altogether likely, that it varies
with the force of the wind, weight of the rising body,
power of propulsion, etc. This, in the language of physicists,
is the angle of inclination, and, as a general thing,
under normal conditions (still air) should be put down as
about one in ten, or 5 3/4 degrees. This would be an ideal
condition, but it has not, as vet been reached. The force
of the wind affects the angle considerably, as does also
the weight and velocity of the apparatus. In general
practice the angle varies from 23 to 45 degrees. At
more than 45 degrees the supporting effort is overcome
by the resistance to forward motion.

Increasing the speed or propulsive force, tends to
lessen the angle at which the machine may be successfully
operated because it reduces the wind pressure.
Most of the modern flying machines are operated at an
angle of 23 degrees, or less.

Maintaining an Equilibrium.

Stable equilibrium is one of the main essentials to
successful flight, and this cannot be preserved in an
uncertain, gusty wind, especially by an amateur. The
novice should not attempt a glide unless the conditions
are just right. These conditions are: A clear, level
space, without obstructions, such as trees, etc., and a
steady wind of not exceeding twelve miles an hour. Always
fly against the wind.

When a reasonable amount of proficiency in the handling
of the machine on level ground has been acquired
the field of practice may be changed to some gentle
slope. In starting from a slope it will be found easier
to keep the machine afloat, but the experience at first is
likely to be very disconcerting to a man of less than iron
nerve. As the glider sails away from the top of the
slope the distance between him and the ground increases
rapidly until the aviator thinks he is up a hundred miles
in the air. If he will keep cool, manipulate his apparatus
so as to preserve its equilibrium, and "let nature take its
course," he will come down gradually and safely to the
ground at a considerable distance from the starting place.
This is one advantage of starting from an elevation--
your machine will go further.

But, if the aviator becomes "rattled"; if he loses control
of his machine, serious results, including a bad fall
with risk of death, are almost certain. And yet this
practice is just as necessary as the initial lessons on
level ground. When judgment is used, and "haste made
slowly," there is very little real danger. While experimenting
with gliders the Wrights made flights innumerable
under all sorts of conditions and never had an accident
of any kind.

Effects of Wind Currents.

The larger the machine the more difficult it will be to
control its movements in the air, and yet enlargement is
absolutely necessary as weight, in the form of motor,
rudder, etc., is added.

Air currents near the surface of the ground are diverted
by every obstruction unless the wind is blowing
hard enough to remove the obstruction entirely. Take,
for instance, the case of a tree or shrub, in a moderate
wind of from ten to twelve miles an hour. As the wind
strikes the tree it divides, part going to one side and
part going to the other, while still another part is directed
upward and goes over the top of the obstruction.
This makes the handling of a glider on an obstructed
field difficult and uncertain. To handle a glider successfully
the place of operation should be clear and the wind
moderate and steady. If it is gusty postpone your flight.
In this connection it will be well to understand the velocity
of the wind, and what it means as shown in the
following table:

Miles per hour Feet per second Pressure per sq. foot
10 14.7 .492
25 36.7 3.075
50 73.3 12.300
100 146.6 49.200

Pressure of wind increases in proportion to the square
of the velocity. Thus wind at 10 miles an hour has four
times the pressure of wind at 5 miles an hour. The
greater this pressure the large and heavier the object
which can be raised. Any boy who has had experience
in flying kites can testify to this, High winds, however,
are almost invariably gusty and uncertain as to direction,
and this makes them dangerous for aviators. It
is also a self-evident fact that, beyond a certain stage,
the harder the wind blows the more difficult it is to
make headway against it.

Launching Device for Gliders.

On page 195 will be found a diagram of the various
parts of a launcher for gliders, designed and patented
by Mr. Octave Chanute. In describing this invention
in Aeronautics, Mr. Chanute says:

"In practicing, the track, preferably portable, is
generally laid in the direction of the existing wind and
the car, preferably a light platform-car, is placed on the
track. The truck carrying the winding-drum and its motor
is placed to windward a suitable distance--say from
two hundred to one thousand feet--and is firmly blocked
or anchored in line with the portable track, which is
preferably 80 or 100 feet in length. The flying or gliding
machine to be launched with its operator is placed on
the platform-car at the leeward end of the portable track.
The line, which is preferably a flexible combination
wire-and-cord cable, is stretched between the winding-
drum on the track and detachably secured to the flying
or gliding machine, preferably by means of a trip-hoop,
or else held in the hand of the operator, so that the
operator may readily detach the same from the flying-
machine when the desired height is attained.

How Glider Is Started.

"Then upon a signal given by the operator the engineer
at the motor puts it into operation, gradually increasing
the speed until the line is wound upon the drum
at a maximum speed of, say, thirty miles an hour. The
operator of the flying-machine, whether he stands upright and
carries it on his shoulders, or whether he sits
or lies down prone upon it, adjusts the aeroplane or
carrying surfaces so that the wind shall strike them on
the top and press downward instead of upward until
the platform-car under action of the winding-drum and
line attains the required speed.

"When the operator judges that his speed is sufficient,
and this depends upon the velocity of the wind as well
as that of the car moving against the wind, he quickly
causes the front of the flying-machine to tip upward, so
that the relative wind striking on the under side of the
planes or carrying surfaces shall lift the flying machine
into the air. It then ascends like a kite to such height
as may be desired by the operator, who then trips the
hook and releases the line from the machine.

What the Operator Does.

"The operator being now free in the air has a certain
initial velocity imparted by the winding-drum and line
and also a potential energy corresponding to his height
above the ground. If the flying or gliding machine is
provided with a motor, he can utilize that in his further
flight, and if it is a simple gliding machine without
motor he can make a descending flight through the air
to such distance as corresponds to the velocity acquired
and the height gained, steering meanwhile by the devices
provided for that purpose.

"The simplest operation or maneuver is to continue
the flight straight ahead against the wind; but it is possible
to vary this course to the right or left, or even to
return in downward flight with the wind to the vicinity
of the starting-point. Upon nearing the ground the
operator tips upward his carrying-surfaces and stops his
headway upon the cushion of increased air resistance
so caused. The operator is in no way permanently
fastened to his machine, and the machine and the operator
simply rest upon the light platform-car, so that
the operator is free to rise with the machine from the
car whenever the required initial velocity is attained.

Motor For the Launcher.

"The motor may be of any suitable kind or construction,
but is preferably an electric or gasolene motor.
The winding-drum is furnished with any suitable or customary
reversing-guide to cause the line to wind smoothly
and evenly upon the drum. The line is preferably a
cable composed of flexible wire and having a cotton or
other cord core to increase its flexibility. The line
extends from the drum to the flying or gliding machine.
Its free end may, if desired, be grasped and held by the
operator until the flying-machine ascends to the desired
height, when by simply letting go of the line the operator
may continue his flight free. The line, however, is preferably
connected to the flying or gliding machine
directly by a trip-hook having a handle or trip lever
within reach of the operator, so that when he ascends
to the required height he may readily detach the line
from the flying or gliding machine."

CHAPTER VII.

PUTTING ON THE RUDDER.

Gliders as a rule have only one rudder, and this is in
the rear. It tends to keep the apparatus with its head to
the wind. Unlike the rudder on a boat it is fixed and
immovable. The real motor-propelled flying machine,
generally has both front and rear rudders manipulated
by wire cables at the will of the operator.

Allowing that the amateur has become reasonably expert
in the manipulation of the glider he should, before
constructing an actual flying machine, equip his glider
with a rudder.

Cross Pieces for Rudder Beam.

To do this he should begin by putting in a cross piece,
2 feet long by 1/4x3/4 inches between the center struts,
in the lower plane. This may be fastened to the struts
with bolts or braces. The former method is preferable.
On this cross piece, and on the rear frame of the plane
itself, the rudder beam is clamped and bolted. This
rudder beam is 8 feet 11 inches long. Having put these
in place duplicate them in exactly the same manner and
dimensions from the upper frame The cross pieces on
which the ends of the rudder beams are clamped should
be placed about one foot in advance of the rear frame
beam.

The Rudder Itself.

The next step is to construct the rudder itself. This
consists of two sections, one horizontal, the other vertical.
The latter keeps the aeroplane headed into the wind,
while the former keeps it steady--preserves the equilibrium.

The rudder beams form the top and bottom frames of
the vertical rudder. To these are bolted and clamped
two upright pieces, 3 feet, 10 inches in length, and 3/4
inch in cross section. These latter pieces are placed about
two feet apart. This completes the framework of the
vertical rudder. See next page (59).

For the horizontal rudder you will require two strips
6 feet long, and four 2 feet long. Find the exact center
of the upright pieces on the vertical rudder, and at this
spot fasten with bolts the long pieces of the horizontal,
placing them on the outside of the vertical strips. Next
join the ends of the horizontal strips with the 2-foot
pieces, using small screws and corner braces. This done
you will have two of the 2-foot pieces left. These go in
the center of the horizontal frame, "straddling" the
vertical strips, as shown in the illustration.

The framework is to be covered with cloth in the
same manner as the planes. For this about ten yards
will be needed.

Strengthening the Rudder.

To ensure rigidity the rudder must be stayed with
guy wires. For this purpose the No. 12 piano wire is
the best. Begin by running two of these wires from the
top eye-bolts of stanchions 3 and 4, page 37, to rudder
beam where it joins the rudder planes, fastening them
at the bottom. Then run two wires from the top of the
rudder beam at the same point, to the bottom eye-bolts
of the same stanchions. This will give you four diagonal
wires reaching from the rudder beam to the top
and bottom planes of the glider. Now, from the outer
ends of the rudder frame run four similar diagonal wires
to the end of the rudder beam where it rests on the
cross piece. You will then have eight truss wires
strengthening the connection of the rudder to the main
body of the glider.

The framework of the rudder planes is then to be
braced in the same way, which will take eight more
wires, four for each rudder plane. All the wires are
to be connected at one end with turn-buckles so the
tension may be regulated as desired.

In forming the rudder frame it will be well to mortise
the corners, tack them together with small nails, and
then put in a corner brace in the inside of each joint.
In doing this bear in mind that the material to be thus
fastened is light, and consequently the lightest of nails,
screws, bolts and corner pieces, etc., is necessary.

CHAPTER VIII.

THE REAL FLYING MACHINE.

We will now assume that you have become proficient
enough to warrant an attempt at the construction of a
real flying machine--one that will not only remain suspended
in the air at the will of the operator, but make
respectable progress in whatever direction he may desire to go.
The glider, it must be remembered, is not
steerable, except to a limited extent, and moves only in
one direction--against the wind. Besides this its power
of flotation--suspension in the air--is circumscribed.

Larger Surface Area Required.

The real flying machine is the glider enlarged, and
equipped with motor and propeller. The first thing to
do is to decide upon the size required. While a glider
of 20 foot spread is large enough to sustain a man it
could not under any possible conditions, be made to rise
with the weight of the motor, propeller and similar
equipment added. As the load is increased so must the
surface area of the planes be increased. Just what this
increase in surface area should be is problematical as
experienced aviators disagree, but as a general proposition
it may be placed at from three to four times the area of
a 20-foot glider.[3]

[3] See Chapter XXV.

Some Practical Examples.

The Wrights used a biplane 41 feet in spread, and 6 1/2
ft. deep. This, for the two planes, gives a total surface
area of 538 square feet, inclusive of auxiliary planes.
This sustains the engine equipment, operator, etc., a total
weight officially announced at 1,070 pounds. It shows
a lifting capacity of about two pounds to the square
foot of plane surface, as against a lifting capacity of
about 1/2 pound per square foot of plane surface for the
20-foot glider. This same Wright machine is also reported
to have made a successful flight, carrying a total
load of 1,100 pounds, which would be over two pounds
for each square foot of surface area, which, with auxiliary
planes, is 538 square feet.

To attain the same results in a monoplane, the single
surface would have to be 60 feet in spread and 9 feet
deep. But, while this is the mathematical rule, Bleriot
has demonstrated that it does not always hold good.
On his record-breaking trip across the English channel,
July 25th, 1909, the Frenchman was carried in a
monoplane 24 1/2 feet in spread, and with a total sustaining
surface of 150 1/2 square feet. The total weight of
the outfit, including machine, operator and fuel sufficient
for a three-hour run, was only 660 pounds. With
an engine of (nominally) 25 horsepower the distance of
21 miles was covered in 37 minutes.

Which is the Best?

Right here an established mathematical quantity is
involved. A small plane surface offers less resistance
to the air than a large one and consequently can attain
a higher rate of speed. As explained further on in this
chapter speed is an important factor in the matter of
weight-sustaining capacity. A machine that travels one-
third faster than another can get along with one-half the
surface area of the latter without affecting the load. See
the closing paragraph of this chapter on this point. In
theory the construction is also the simplest, but this is
not always found to be so in practice. The designing
and carrying into execution of plans for an extensive
area like that of a monoplane involves great skill and
cleverness in getting a framework that will be strong
enough to furnish the requisite support without an undue excess
of weight. This proposition is greatly simplified
in the biplane and, while the speed attained by the latter
may not be quite so great as that of the monoplane, it
has much larger weight-carrying capacity.

Proper Sizes For Frame.

Allowing that the biplane form is selected the construction
may be practically identical with that of the
20-foot glider described in Chapter V., except as to size
and elimination of the armpieces. In size the surface
planes should be about twice as large as those of the
20-foot glider, viz: 40 feet spread instead of 20, and 6 feet
deep instead of 3. The horizontal beams, struts, stanchions,
ribs, etc., should also be increased in size proportionately.

While care in the selection of clear, straight-grained
timber is important in the glider, it is still more important
in the construction of a motor-equipped flying
machine as the strain on the various parts will be much
greater.

How to Splice Timbers.

It is practically certain that you will have to resort to
splicing the horizontal beams as it will be difficult, if not
impossible, to find 40-foot pieces of timber totally free
from knots and worm holes, and of straight grain.

If splicing is necessary select two good 20-foot pieces,
3 inches wide and 1 1/2 inches thick, and one 10-foot long,
of the same thickness and width. Plane off the bottom
sides of the 10-foot strip, beginning about two feet back
from each end, and taper them so the strip will be about
3/4 inch thick at the extreme ends. Lay the two 20-foot
beams end to end, and under the joint thus made place
the 10-foot strip, with the planed-off ends downward.
The joint of the 20-foot pieces should be directly in the
center of the 10-foot piece. Bore ten holes (with a 1/4-
inch augur) equi-distant apart through the 20-foot
strips and the 10-foot strip under them. Through these
holes run 1/4-inch stove bolts with round, beveled heads.
In placing these bolts use washers top and bottom, one
between the head and the top beam, and the other between
the bottom beam and the screw nut which holds
the bolt. Screw the nuts down hard so as to bring the
two beams tightly together, and you will have a rigid
40-foot beam.

Splicing with Metal Sleeves.

An even better way of making a splice is by tonguing
and grooving the ends of the frame pieces and enclosing
them in a metal sleeve, but it requires more mechanical
skill than the method first named. The operation of
tonguing and grooving is especially delicate and calls
for extreme nicety of touch in the handling of tools, but
if this dexterity is possessed the job will be much more
satisfactory than one done with a third timber.

As the frame pieces are generally about 1 1/2 inch in
diameter, the tongue and the groove into which the
tongue fits must be correspondingly small. Begin by
sawing into one side of one of the frame pieces about 4
inches back from the end. Make the cut about 1/2 inch
deep. Then turn the piece over and duplicate the cut.
Next saw down from the end to these cuts. When the
sawed-out parts are removed you will have a "tongue"
in the end of the frame timber 4 inches long and 1/2 inch
thick. The next move is to saw out a 5/8-inch groove in
the end of the frame piece which is to be joined. You
will have to use a small chisel to remove the 5/8-inch bit.
This will leave a groove into which the tongue will fit
easily.

Joining the Two Pieces.

Take a thin metal sleeve--this is merely a hollow tube
of aluminum or brass open at each end--8 inches long,
and slip it over either the tongued or grooved end of one
of the frame timbers. It is well to have the sleeve fit
snugly, and this may necessitate a sand-papering of the
frame pieces so the sleeve will slip on.

Push the sleeve well back out of the way. Cover the
tongue thoroughly with glue, and also put some on the
inside of the groove. Use plenty of glue. Now press
the tongue into the groove, and keep the ends firmly
together until the glue is thoroughly dried. Rub off the
joint lightly with sand-paper to remove any of the glue
which may have oozed out, and slip the sleeve into place
over the joint. Tack the sleeve in position with small
copper tacks, and you will have an ideal splice.

The same operation is to be repeated on each of the
four frame pieces. Two 20-foot pieces joined in this
way will give a substantial frame, but when suitable
timber of this kind can not be had, three pieces, each 6
feet 11 inches long, may be used. This would give 20
feet 9 inches, of which 8 inches will be taken up in the
two joints, leaving the frame 20 feet 1 inch long.

Installation of Motor.

Next comes the installation of the motor. The kinds
and efficiency of the various types are described in the
following chapter (IX). All we are interested in at
this point is the manner of installation. This varies
according to the personal ideas of the aviator. Thus one
man puts his motor in the front of his machine, another
places it in the center, and still another finds the rear of
the frame the best. All get good results, the comparative
advantages of which it is difficult to estimate. Where
one man, as already explained, flies faster than another,
the one beaten from the speed standpoint has an advantage
in the matter of carrying weight, etc.

The ideas of various well-known aviators as to the
correct placing of motors may be had from the following:

Wrights--In rear of machine and to one side.

Curtiss--Well to rear, about midway between upper
and lower planes.

Raich--In rear, above the center.

Brauner-Smith--In exact center of machine.

Van Anden--In center.

Herring-Burgess--Directly behind operator.

Voisin--In rear, and on lower plane.

Bleriot--In front.

R. E. P.--In front.

The One Chief Object.

An even distribution of the load so as to assist in
maintaining the equilibrium of the machine, should be
the one chief object in deciding upon the location of the
motor. It matters little what particular spot is selected
so long as the weight does not tend to overbalance the
machine, or to "throw it off an even keel." It is just
like loading a vessel, an operation in which the expert
seeks to so distribute the weight of the cargo as to keep
the vessel in a perfectly upright position, and prevent a
"list" or leaning to one side. The more evenly the cargo
is distributed the more perfect will be the equilibrium of
the vessel and the better it can be handled. Sometimes,
when not properly stowed, the cargo shifts, and this at
once affects the position of the craft. When a ship
"lists" to starboard or port a preponderating weight of
the cargo has shifted sideways; if bow or stern is unduly
depressed it is a sure indication that the cargo has shifted
accordingly. In either event the handling of the craft
becomes not only difficult, but extremely hazardous.
Exactly the same conditions prevail in the handling of a
flying machine.

Shape of Machine a Factor.

In placing the motor you must be governed largely by
the shape and construction of the flying machine frame.
If the bulk of the weight of the machine and auxiliaries
is toward the rear, then the natural location for the motor
will be well to the front so as to counterbalance the
excess in rear weight. In the same way if the
preponderance of the weight is forward, then the motor
should be placed back of the center.

As the propeller blade is really an integral part of the
motor, the latter being useless without it, its placing
naturally depends upon the location selected for the
motor.

Rudders and Auxiliary Planes.

Here again there is great diversity of opinion among
aviators as to size, location and form. The striking
difference of ideas in this respect is well illustrated in
the choice made by prominent makers as follows:

Voisin--horizontal rudder, with two wing-like planes,
in front; box-like longitudinal stability plane in rear,
inside of which is a vertical rudder.

Wright--large biplane horizontal rudder in front at
considerable distance--about 10 feet--from the main
planes; vertical biplane rudder in rear; ends of upper
and lower main planes made flexible so they may be
moved.

Curtiss--horizontal biplane rudder, with vertical damping
plane between the rudder planes about 10 feet in
front of main planes; vertical rudder in rear; stabilizing
planes at each end of upper main plane.

Bleriot--V-shaped stabilizing fin, projecting from rear
of plane, with broad end outward; to the broad end of
this fin is hinged a vertical rudder; horizontal biplane
rudder, also in rear, under the fin.

These instances show forcefully the wide diversity of
opinion existing among experienced aviators as to the
best manner of placing the rudders and stabilizing, or
auxiliary planes, and make manifest how hopeless would
be the task of attempting to select any one form and
advise its exclusive use.

Rudder and Auxiliary Construction.

The material used in the construction of the rudders
and auxiliary planes is the same as that used in the main
planes--spruce for the framework and some kind of
rubberized or varnished cloth for the covering. The
frames are joined and wired in exactly the same manner
as the frames of the main planes, the purpose being to
secure the same strength and rigidity. Dimensions of
the various parts depend upon the plan adopted and the
size of the main plane.

No details as to exact dimensions of these rudders and
auxiliary planes are obtainable. The various builders,
while willing enough to supply data as to the general
measurements, weight, power, etc., of their machines,
appear to have overlooked the details of the auxiliary
parts, thinking, perhaps, that these were of no particular
import to the general public. In the Wright machine, the
rear horizontal and front vertical rudders may be set
down as being about one-quarter (probably a little less)
the size of the main supporting planes.

Arrangement of Alighting Gear.

Most modern machines are equipped with an alighting
gear, which not only serves to protect the machine and
aviator from shock or injury in touching the ground, but
also aids in getting under headway. All the leading
makes, with the exception of the Wright, are furnished
with a frame carrying from two to five pneumatic rubber-
tired bicycle wheels. In the Curtiss and Voisin
machines one wheel is placed in front and two in the
rear. In the Bleriot and other prominent machines the
reverse is the rule--two wheels in front and one in the
rear. Farman makes use of five wheels, one in the,
extreme rear, and four, arranged in pairs, a little to the
front of the center of the main lower plane.

In place of wheels the Wright machine is equipped
with a skid-like device consisting of two long beams
attached to the lower plane by stanchions and curving
up far in front, so as to act as supports to the horizontal
rudder.

Why Wood Is Favored.

A frequently asked question is: "Why is not aluminum,
or some similar metal, substituted for wood."
Wood, particularly spruce, is preferred because, weight
considered, it is much stronger than aluminum, and this
is the lightest of all metals. In this connection the following
table will be of interest:

Compressive
Weight Tensile Strength Strength
per cubic foot per sq. inch per sq. inch
Material in lbs. in lbs. in lbs.
Spruce . . . . 25 8,000 5,000
Aluminum 162 16,000 ......
Brass (sheet) 510 23,000 12,000
Steel (tool) 490 100,000 40,000
Copper (sheet) 548 30,000 40,000

As extreme lightness, combined with strength,
especially tensile strength, is the great essential in flying-
machine construction, it can be readily seen that the
use of metal, even aluminum, for the framework, is
prohibited by its weight. While aluminum has double the
strength of spruce wood it is vastly heavier, and thus
the advantage it has in strength is overbalanced many
times by its weight. The specific gravity of aluminum
is 2.50; that of spruce is only 0.403.

Things to Be Considered.

In laying out plans for a flying machine there are five
important points which should be settled upon before
the actual work of construction is started. These are:

First--Approximate weight of the machine when finished
and equipped.

Second--Area of the supporting surface required.

Third--Amount of power that will be necessary to
secure the desired speed and lifting capacity.

Fourth--Exact dimensions of the main framework
and of the auxiliary parts.

Fifth--Size, speed and character of the propeller.

In deciding upon these it will be well to take into
consideration the experience of expert aviators regarding
these features as given elsewhere. (See Chapter X.)

Estimating the Weights Involved.

In fixing upon the probable approximate weight in
advance of construction much, of course, must be assumed.
This means that it will be a matter of advance
estimating. If a two-passenger machine is to be built
we will start by assuming the maximum combined
weight of the two people to be 350 pounds. Most of
the professional aviators are lighter than this. Taking
the medium between the weights of the Curtiss and
Wright machines we have a net average of 850 pounds
for the framework, motor, propeller, etc. This, with
the two passengers, amounts to 1,190 pounds. As the
machines quoted are in successful operation it will be
reasonable to assume that this will be a safe basis to
operate on.

What the Novice Must Avoid.

This does not mean, however, that it will be safe to
follow these weights exactly in construction, but that
they will serve merely as a basis to start from. Because
an expert can turn out a machine, thoroughly equipped,
of 850 pounds weight, it does not follow that a novice
can do the same thing. The expert's work is the result
of years of experience, and he has learned how to construct
frames and motor plants of the utmost lightness
and strength.

It will be safer for the novice to assume that he can
not duplicate the work of such men as Wright and Curtiss
without adding materially to the gross weight of
the framework and equipment minus passengers.

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