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Model Flying Machines
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       :PG.Title: Model Flying Machines
       :PG.Id: 64296
       :PG.Rights: Public Domain
       :PG.Producer: James Simmons
       :PG.Credits: This file was produced from page images at Google Books.
       :DC.Creator: Alfred Powell Morgan
       :DC.Title: Model Flying Machines
       :DC.Language: en
       :DC.Created: 1913
       :PG.Released: 2021-01-14
       :coverpage: images/CoverImage.jpg

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.. topic:: Transcriber's Note

    This book was transcribed from scans of the original found at Google Books. There was no book cover image, so I made one by
    enlarging a black and white picture of the book from an advertisement found in another Cole & Morgan title and tried to 
    make it look presentable, including adding color. The author uses a variant spelling of the word "fuselage" which I have
    left as is.
        
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       Model Flying Machines 

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       HOW TO BUILD AND FLY
       
       THEM

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       BY

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       \A. P. MORGAN 

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       NEWARK, N. J.

       COLE & MORGAN

       1913

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   COPYRIGHT, 1913

   By

   COLE & MORGAN

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INTRODUCTION.
-------------

The construction of model aeroplanes is essentially 
simple and for those wishing to experiment it is 
an ideal method of gaining practical knowledge of the 
new science of aeronautics.

Aside from the utilitarian standpoint, there is another 
aspect hardly second or less important. A well balanced 
little machine which will leave the hand and soar away 
under its own power is a source of fascination and delight 
not only to its maker, but to the spectators of the flight as well.

This little volume has been planned to present the 
material it contains in such a manner that it will aid 
the judgment of the experimenter and assist him in developing 
his own ideas. To make it of immediate value 
to the novice a number of detailed plans for building 
various machines have been included. For the greater 
part these machines have been designed rather to fly 
greater distances than to appear like some man carrying 
prototype.

.. figure:: images/Plate1.jpg
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   :alt: PLATE I. Launching a Model Aeroplane.
   
   PLATE I. Launching a Model Aeroplane.

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CHAPTER I. GENERAL PRINCIPLES UNDERLYING AEROPLANE FLIGHT.
----------------------------------------------------------

To enter deeply into a discussion of the theory of the 
aeroplane would not only tire the reader but would 
waste valuable space in endeavoring to explain that 
which has been more adequately dealt with in more 
notable works.

In order to gain a clear understanding of the following 
chapters, however, it will be necessary to first 
grasp the elementary principles underlying the flight 
of an aeroplane. In setting these forth, I shall try, 
as far as possible, not to hamper or confuse with 
unnecessary terms or technicalities, except where 
such might be of worth in rendering a better 
conception of that to which they apply.


.. figure:: images/Image1.jpg
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   :alt: FIG. 1. Diagram showing a kite held in the air by the action of a wind.
   
   FIG. 1. Diagram showing a kite held in the air by the action of a wind. The dotted lines and arrow heads represent the direction and force of the wind.

An ordinary kite is one of the best examples of the 
action of an aeroplane. It is scarcely necessary to 
define the kite; it is a rigid frame of wooden 
sticks, on which is stretched a surface of cloth 
or paper. A string attached to the kite by means of 
a "bridle" serves to hold the apparatus to the ground.

In Fig. 1 is represented a kite against which the wind 
is blowing as indicated by the dotted lines. The string 
is so arranged that the kite is inclined at an angle 
to the wind and thus is sustained in the air by the 
force of the wind, viz., the molecules of air in 
striking against the slanting surface exert a pressure 
upon it which both calculation and experiment show 
to be perpendicular to the surface and tending to 
lift it. The kite also exerts a strong pull on the 
string which holds it in position.

But on days when there is no breeze or when the wind 
suddenly dies out; what is to be done then?

Wind is not an absolute thing. It is a *relative* movement 
of the surrounding air in *comparison* to a body. The 
effect is the same, and the relative movement takes 
place whether the air is still and the body in motion, 
or the air is in motion and the body motionless.

It is therefore an easy matter to "create a breeze" 
and a kite can be kept in the air providing the 
person flying the kite and holding the string 
commences to run.

Although no wind is blowing, the pressure 
of the air through which the kite is moving 
will cause it to remain in the air. In 
other words, the kite would be sustained 
in the air by virtue of *its own relative 
motion to the wind*. In order that the kite 
may fly, it makes no difference whether 
the wind moves against the kite or the 
kite moves against the wind.

An aeroplane, in fact, is nothing but a 
kite which creates its own breeze. If 
an aeroplane were attached to a strong 
wire serving as the string in the case 
of the kite, it would fly in the same manner 
as the kite, providing of course that 
the wind were sufficiently powerful. 
If the wind were not blowing at all, or 
not blowing hard enough, the other end 
of the wire could be attached to an automobile 
and by driving the automobile fast enough the 
required *relative motion* of the air would 
be produced and the aeroplane would fly.

There could be no direct benefit derived, 
however, from an aeroplane which must remain 
attached to a machine running over the 
earth and travel in its wake. Some other 
means of producing the required relative 
motion is necessary so that the aeroplane may 
be free to fly in any direction and either 
with or against the wind. This is accomplished 
by a *propeller* driven by a motor revolving 
at high speed in the aeroplane itself.

The action of an aerial propeller is similar 
to that of its marine prototype employed 
for driving ships through the water. Each 
depends for its action upon the imparting of 
a sternward motion to a column of fluid, in 
the one case air and in the other water. A 
propeller screws itself forward into the 
surrounding media in identically the same manner 
that an ordinary screw forces itself into a block 
of wood. An aeroplane therefore essentially 
consists of the wings or supporting surfaces, 
also sometimes called planes, driven through 
the air in an *oblique* manner by the propeller 
and motor.

.. figure:: images/Image2.jpg
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   :alt: FIG. 2. Diagram representing a typical monoplane.
   
   FIG. 2. Diagram representing a typical monoplane. The only remaining requisition is that the aeroplane may be guided at will, caused to rise or fall or be steered to the right and left. The devices used to accomplish this are two rudders called respectively the "elevator" and the "steering rudder." The "elevator" takes the form of a small surface carried either in front or behind the main supporting surfaces and enables the machine to take an upward, a horizontal or downward course accordingly as it is adjusted. It acts as a rudder to steer the aeroplane up or down or to hold it to its course in exactly the same manner that a ship's rudder steers it to the right or left. When it is desired to direct the aeroplane upwards, the front edge of the elevator is raised so as to set it at a greater angle with the horizontal. If the aeroplane's course is required to be downward, the front edge of the elevator is lowered.

Aeroplanes are usually of two general types, *monoplanes* 
and *biplanes*. A monoplane, as its name implies, is a 
machine having a single pair of wings or supporting surfaces. 
The Bleriot, Antoinette and Santos Dumont machines are 
the most prominent representatives of this type of aeroplane.

The "elevator" on a monoplane is usually in the rear of 
the main supporting surfaces. When in this position it also 
acts as a tail to furnish longitudinal stability to the 
machine in the same way that a feather on an arrow steadies 
its flight.

.. figure:: images/Image3.jpg
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   :alt: FIG 3. Diagram showing the makeup of a biplane (Wright).
   
   FIG 3. Diagram showing the makeup of a biplane (Wright).

The most prominent machines of the biplane group are 
the Voisin, Wright, Curtiss and Farman aeroplanes. The 
old practice of placing the elevator in the front of a 
biplane is gradually being abandoned and it is safe to 
say that by the time this book has been printed all 
these machines will be of the "headless" variety with 
the elevator in the rear.

The vertical fins shown between the planes of the elevator 
in the old type of biplane, counterbalance the effect of 
gusts of wind striking the vertical rudder from the sides 
and also act as a pivot for turning to the right and left. 
Together with the steering rudder, they constitute a sort 
of keel which keeps the machine straight to its course.

In order for an aeroplane to fly in the accepted sense of 
the word, it must possess supporting surfaces, an elevator 
or tail and a propeller driven by a motor. These are 
essentially the sustaining, propelling and steering members 
of the machine.

.. figure:: images/Image4.jpg
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   :alt: FIG. 4. Two methods of controlling the lateral stability of an aeroplane.
   
   FIG. 4. Two methods of controlling the lateral stability of an aeroplane.

The machine must, however, also possess "lateral 
stability," that is, the wings of the apparatus must not incline 
from the right to left or vice versa during the flight. The 
machine must be so constructed at it rights itself by its 
own effort or is under the immediate control of the aviator.

This is accomplished by "warping the wings," that is, the 
extreme tips of the planes can be moved up and down so as 
to present a greater or lesser angle and corresponding increase 
or decrease the lifting capacity of those portions.

The same result is also reached by means of small subsidiary 
moving planes attached to the rear of the main supporting 
surfaces called "aileron." When one aileron is lowered, the 
other is raised. The action of the air on the ailerons is 
to depress the one which is raised and to raise the one which 
is lowered as shown by the arrows in the illustration.

CHAPTER II. GENERAL REMARKS REGARDING MODEL AEROPLANE CONSTRUCTION. THE QUESTION OF RESISTANCE. WEIGHT. STABILITY. 
------------------------------------------------------------------------------------------------------------------

**The first requirement** of a model aeroplane is that 
it shall fly. The first essential for a machine to fly 
well is that it must be simple. Simplicity usually 
insures success and is synonymous with efficiency. A 
complicated scale model having as its prototype one of 
the most successful man-carrying machines usually will 
not fly. If it does fly, *it does not do so well*. Miniature 
steam engines, motors, etc., can be constructed to 
exact scale and will justify their existence by actually 
working and performing duty, but in most cases a model 
aeroplane made to scale will not fly well until it begins 
to approach full size.

The next indispensable feature might be called *lightness*, 
but at the same time it must be borne in mind that strength is 
also "second to none" and it would be fatal to sacrifice 
the one for the other. The hard knocks and battering which 
a model usually receives at the hands of a novice will 
soon wreck any flimsy construction.

**To design model aeroplanes will at first seem like**
"robbing Peter to pay Paul," that is, no one part can be 
developed to an extreme without seriously affecting the 
efficiency of the other parts. The successful machine 
is a sort of "happy medium" arrived at solely through 
experiment. A thorough understanding, however, of the 
part played by each individual member of a model and its 
characteristics will make it possible to avoid much 
unnecessary work in that connection. It is therefore well 
to carefully read the following chapters before commencing 
to carry out any original ideas or to make any radical 
departure from the designs offered in this book.

From these statements it must not be inferred that the 
successful model aeroplane builder is necessarily an 
individual possessed of consummate skill in the handling 
of tools or a person of unusual judgment. A few simple 
tools and trifling mechanical ability will enable any one
to build the simple little machines herein described. The 
greatest asset required in the work is patience, patience 
spelled with a capital "P." Not only patience in building 
the machines, but patience in adjusting them and patience 
in flying them. Making haste with a model aeroplane is 
poor policy. It never pays to use slipshod methods. Take 
the time to make sure every part is the best that you can 
make it. Care with the little details will insure success.

Model aeroplanes are exasperating to the extreme. A new model 
will swerve to the right and left or dive with unerring 
precision to the ground or nearest object. They seem to defy 
all attempts to make them behave and in the first few flights 
usually perform a "new one" every time. This is the point where 
success comes to the model aeroplanist who possesses patience 
and perseverance. One must learn to adjust and fly a model 
aeroplane by practice just as he must also learn to swim or 
ride a bicycle by repeated trials. A little persuasion will 
soon make a model soar in a surprising manner.

**The question of resistance** is the first consideration of the 
model aeroplane designer. An aeroplane should pass through the 
air in such a manner that it leaves that medium in as motionless 
a state as possible. All motion of the surrounding air represents 
so much power wasted. It is obvious that a boat with a square 
prow will offer more resistance than a ship having a sharp bow. 
The latter causes considerably less disturbance of the fluid 
in which it moves than the former.

.. figure:: images/Image5.jpg
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   :alt: FIG. 5. The disturbance created in the air by a square object.

   FIG. 5. The disturbance created in the air by a square object. The arrow points in the direction of motion. The space in the rear of the object is the scene of violent eddy.

The resistance of an aeroplane is made up of: 
 
1. *Aerodynamic* resistance. 
2. Head resistance. 
3. Surface resistance. 

The first is offered by the planes of the machine itself 
and results directly from the pressure of the air 
supporting the model during flight.

The second is set up by the framework, the edges of the 
planes, the wires, etc., while the last is caused solely 
by the air in traveling over the surfaces of the various 
members composing the machines.

.. figure:: images/Image6.jpg
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   :scale: 85 %
   :alt: FIG. 6. The disturbance caused by a triangular body moving through the atmosphere.
   
   FIG. 6. The disturbance caused by a triangular body moving through the atmosphere.

The head and surface or *skin* resistance, as it is sometimes 
called, can be reduced, but the aerodynamical resistance cannot.

Air is no less a fluid than water, and the same considerations 
apply to it, subject, of course, to certain conditions and 
with due regard for such factors as density, viscoscity, etc.

.. figure:: images/Plate2.jpg
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   :scale: 85 %
   :alt: Plate II.
   
   Plate II.

When an object, such as a square stick of wood, is moved through the 
air, the latter flows around it leaving behind a region of "dead air." 
The dead air represents so much waste energy or unnecessary resistance 
to overcome because it requires an expenditure of power to drag it along.

.. figure:: images/Image7.jpg
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   :alt: FIG. 7. Showing the disturbance created by a small spar on the back of a plane.
   
   FIG. 7. Showing the disturbance created by a small spar on the back of a plane.

It is obvious then that bodies which are to move through the air with 
the least resistance possible should be given such a shape that the 
stream lines of air will flow around it smoothly and not leave a dead 
region behind. In other words, the stream line flow of the air shall 
keep the same contour as the surface.

**The ichthyoid or fish-like form** is of such a shape. This is illustrated 
in Fig. 8. Its greatest diameter should be about two-fifths of its entire 
length from the head. All struts, stanchions, etc., should be given this shape.

.. figure:: images/Image8.jpg
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   :alt: FIG. 8. Diagram illustrating the ichthyoid shape and how smoothly it slips through the air without creating an eddy.
   
   FIG. 8. Diagram illustrating the ichthyoid shape and how smoothly it slips through the air without creating an eddy.

This shape is very interesting because of its probable origin, for a 
glance is sufficient to tell that it not only resembles a fish but 
also the body of a bird.

**Weight** is an all-important item in model aeroplaning. How to obtain the 
maximum strength with the minimum of weight is undoubtedly the most 
difficult problem which the aviator has to solve. Weight is a much 
more important factor in model aeroplanes than in the case of 
full-size machines because models do not fly fast enough to possess 
a high weight-carrying capacity.

.. figure:: images/Image9.jpg
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   :alt: FIG. 9. Of the three shapes shown above, the round one will slip through the air with the least disturbance and resistance.
   
   FIG. 9. Of the three shapes shown above, the round one will slip through the air with the least disturbance and resistance. A bar of wood like (A), 2 inches square, showed a "drift" of 5.16 lbs. when placed in a breeze blowing 49 miles per hour. Turning it as shown by (B) changed the "drift" to 5.47 lbs. A round bar, 2 inches in diameter, like (C) showed 2.97 lbs. "drift" under the same conditions.

It is only by the constant use of a pair of scales and an accurate 
knowledge of materials with the ability to combine them in the most 
efficient manner that the weight and strength may be kept in harmony. 
Such knowledge and experience come only with practice. They may, 
however, be acquired by any one. In this regard, a notebook forms 
an almost indispensable aid to the experimenter. After a machine has 
been built an accurate record of every flight and of every 
alteration or change in material should be made.

.. figure:: images/Image10.jpg
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   :alt: FIG. 10. The figures given above each shape show the "drift" in lbs. of wooden bars of those shapes when placed in a wind blowing 40 miles an hour.
   
   FIG. 10. The figures given above each shape show the "drift" in lbs. of wooden bars of those shapes when placed in a wind blowing 40 miles an hour. The bars experimented with had a depth of 9 inches in the direction of the arrows and were 2 inches wide.

**Automatic stability** without doubt has attracted more attention 
from engineers and aviators than any other one problem connected 
with aviation. Since it is not possible for a model aeroplane 
to carry a pilot it is much more important that it should be 
naturally stable than any of its man-carrying prototypes. Automatic 
stability in a model of only two or three feet spread at the most, 
is quite a different proposition from that offered by a full-size machine.

.. figure:: images/Image11.jpg
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   :alt: FIG. 11. Flat and dihedral planes. 
   
   FIG. 11. Flat and dihedral planes. 

It would at first seem, that by placing the centre of gravity of 
the machine very low such stability could be secured. This is 
accomplished to a certain extent by setting the wings or planes 
at a dihedral angle. But if the angle is excessive, the 
aeroplane will fly with a pitching motion known as accentricity.

The centres of gravity, of pressure and of head resistance 
*should be at the same point*. The centre of thrust of the 
propeller should also pass through this point. *In this will 
be found the secret of the successful model aeroplane*. It 
is only arrived at by careful experiment and calculation.

Head resistance increases stability while weight and speed 
lessen it. When an aeroplane is gliding (traveling downwards) 
its stability is greater than when it is rising or flying 
horizontally. It is the *least stable* when *rising*.

CHAPTER III. PLANES AND RUDDERS. ELEVATORS AND TAILS.
-----------------------------------------------------

In Chapter I it was explained that an aeroplane is fundamentally 
composed of a supporting surface, divided into one or two 
parts, usually the planes or wings, which cut the air in 
an oblique manner, driven by a propeller and motor. Before 
going further it is perhaps best to understand more exactly 
how the planes operate and support the machine in the air 
than it was possible to explain in the first chapter without 
confusion. A theoretical aeroplane consists of a flat surface 
or plane. When the propeller is set into motion the plane is 
driven through the air in an oblique manner and compels 
the gaseous molecules to glide under its surface. Since the 
plane is at an angle, the front edge being higher than the back, 
the air must necessarily leave at the rear in a downward direction. 
The air molecules in traveling under the surface exercise a 
resistance upon it which is really a pressure against the 
plane. When this pressure is resolved into its components, 
it is found to be made up of two forces, one horizontal, 
tending to retard the forward motion, and called the 
*drift*; the other, vertical and tending to *lift* the plane.

The centre of these forces is not as might be supposed at the 
centre of the plane, but at a point between the centre and the 
front edge called the "centre of pressure." The centre of 
pressure approaches the front edge as the angle of the plane 
with the horizontal becomes less.

In order to render a better idea of how it is possible for 
an aeroplane to gain support in the air consider a skater 
moving swiftly over very thin ice which would not bear his 
weight, but since he is moving so rapidly that any one portion 
of the ice does not have time to bend to the breaking point, he 
is supported. In somewhat the same manner, the planes pass so 
rapidly on to new and undisturbed bodies of air, and stay over 
one body for so brief an instant that there is no time to 
completely overcome the inertia of the air and force it downwards.

.. figure:: images/Image12.jpg
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   :alt: FIG. 12. The action of the air upon a curved and a flat plane.
   
   FIG. 12. The action of the air upon a curved and a flat plane. We have seen that by the effects of the resistance of the air, an aeroplane may be sustained in the atmosphere. We must now see in what manner we can use these effects to the greatest advantage.

First of all, we have been continually speaking of a "plane" as 
the supporting surface, which from the definition of the word 
would lead one to believe that they were flat. If the wings of 
a bird are examined, it will soon be noticed that they are concave 
underneath. Since the first attempts at aviation, therefore, 
machines have been built with planes or wings concave on the underside. 
The reason for this is very apparent from Fig. 12. The first
illustration shows the action of a flat surface moving through the 
air. The air streams, as represented by the lines do not follow 
the surface of the plane, but leave a considerable region of dead 
air. This is the reason that a flat plane is very inefficient 
and not capable of giving so great a lift as the curved plane 
in the next figure where the lines follow the outline of the 
plane. The less disturbance a plane causes in the surrounding 
air, the closer it is said to approach to "stream line form." 
A correctly curved plane is considerably more effectual than a 
flat one, giving at the same time greater "lift" and less "drift."

**Built-up Planes**, that is, planes having a double curve approaching 
true stream line form, come nearer being the ideal plane than 
any other from some standpoints, but do not possess any advantages 
when used on models of less than four feet spread.

.. figure:: images/Image13.jpg
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   :alt: FIG. 13. Section of a built-up plane showing how a rib is made.
   
   FIG. 13. Section of a built-up plane showing how a rib is made. When made small, they offer greater "drift" or head resistance than a single curved surface plane and cannot because of the delicate structure necessary to make them light, withstand hard knocks. They have the further disadvantage of being from a constructional standpoint very hard to make smooth and rigid.

There are innumerable substances which would at first seem 
to recommend themselves as material for planes, but we may 
immediately thrust the greater portion aside. By all means 
*avoid tracing cloth or linen*, not only because its heavy weight 
forever precludes it from this use, but because it wrinkles 
and cockles so as to be absolutely useless when slightly damp or wet.

**Tissue paper** wrinkles easily and is not strong enough.

**Jap silk** is an excellent material for fabric covered planes, 
being at once light and strong. However, by far the most 
satisfactory plane of this kind is formed by silk bolting cloth 
which has been coated with collodion. The collodion is brushed 
on with a fine camel's hair brush after the fabric is in 
place and it is thereby rendered both waterproof and air-tight.

Fabrics should always be stretched over the planes from 
end to end and not front to back or vice versa. Make 
the lap joints or pockets around the end spars as long 
as possible so that they will not draw "dead air" and 
impede the forward motion of the machine.

**Bamboo Paper** is one of the best materials for covering 
the planes of a model aeroplane and is to be highly 
recommended. It is made in Japan from bamboo fibre 
and is very strong. It is usually stretched tightly 
over the framework and then given two coats of collodion 
or, what is much better, bamboo varnish.

**The framework** of the planes may be made of rattan, split 
bamboo, spruce, or steel piano wire. Piano wire is excellent 
for small machines since it is springy and light and able 
to withstand shocks. It is easily bent to any shape and 
offers considerably less head resistance than rattan 
because of its small diameter. Rattan can be bent into 
almost any shape by wetting.

Nothing is better for the cross pieces, ribs, etc., of 
the planes or framework than split bamboo. Bulk for 
bulk it is heavier but infinitely stronger than other 
woods. It is easily worked and can be bent into all 
kinds of shapes. Bamboo must always be bent while hot. 
The best source of heat is a spirit lamp or a bunsen 
burner. Always bend *toward* the hottest side. When bent 
apply a cold wet rag to cool quickly. If bent more 
than necessary, it may be straightened by applying 
heat again and allowing it to straighten itself.

In order to make long bends, such as the ends of 
planes, alighting skids, etc., first wind a strip of 
wet rag around, the bamboo and allow it to remain on 
for ten or fifteen minutes. Then remove the rag, 
heat the bamboo in a flame and bend slowly.

.. figure:: images/Plate3.jpg
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   :alt: PLATE III.
   
   PLATE III.

With a little care, strips several feet long may be easily 
split from bamboo rods. The best method of accomplishing 
this is to use a fine saw, but a sharp knife will often 
be successful.

.. figure:: images/Image14.jpg
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   :alt: FIG. 14. How ribs may be joined to the long members.
   
   FIG. 14. How ribs may be joined to the long members.

**Planes** of any considerable size require ribs to support 
and hold the fabric in shape. Split bamboo is one of the 
best materials for this purpose. Two very good methods 
of joining the ribs to the long members of the planes 
are illustrated in Fig. 14. In the first, a strip of
thin sheet aluminum is bent around the rib and spar and 
fastened by lashing with silk thread. Care must be taken 
to file off all sharp edges on the aluminum which might 
otherwise cut the thread. The second method is the neatest 
and probably the best, since the rib cannot so easily twist 
or slip out of place.

**Wood Planes.** In spite of the many advantages of fabric planes 
they cannot approach wooden planes for efficiency on a small 
machine. Wood is strong, light and does not change its adjustment.

Whitewood and spruce are the best materials for the purpose. 
Do not endeavor to saw out the wood. Use a carpenter's plane 
as much as possible in the work. A saw tears the fibres of 
the wood and will make the finished plane full of tiny splits.

The wood, however, may be sawed down to a thickness of 5/32 
of an inch and then planed down from that. The finished 
plane should be about 1/16 of an inch thick.

When planing down the wood do not butt one end against a 
bench stop, because as the wood becomes thin, the pressure 
exerted by the plane against the wood will cause it to rise 
in the middle and thereby become thinner at that part. 
Instead, use a clamp to fasten the wood at one end to the 
bench and *plane away* from the clamp—Plane down to a 
smooth surface and *avoid* the use of sand-paper.

.. figure:: images/Image15.jpg
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   :alt: FIG. 15. Form for bending the planes.
   
   FIG. 15. Form for bending the planes. 

**Forming the Curve** by steaming and bending the wood is a 
very poor method. It soon becomes distorted and warped.

.. figure:: images/Image16.jpg
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   :scale: 85 %
   :alt: FIG. 16. A good method of building a wooden plane. 
   
   FIG. 16. A good method of building a wooden plane. 

The best method is illustrated in Fig 16. A piece of
wood of the same length as the completed plane and 
having a cross section like that at A is glued to 
the forward under edge of a flat plane B. After the 
glue has hardened, the plane is worked down to the 
shape shown at D which is very close to the stream 
line form. The plane is then varnished to prevent it 
from absorbing moisture and losing its shape. The 
ends may be covered with thin Jap silk, carefully 
glued on to prevent splitting. The Wright brothers 
cover the blades of the propellers on their aeroplanes 
with silk for the same purpose.

Air does not flow smoothly when changing from an 
interrupted flow to an uninterrupted flow around a 
square corner and so by rounding the ends of the 
planes, the disturbance at that point is somewhat 
eliminated.

Planes having rattan or piano wire edges cannot very 
well be of any other shape than those which are 
illustrated in Fig. 17.

.. figure:: images/Image17.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 17. Various shapes a plane may take.
   
   FIG. 17. Various shapes a plane may take. 
   
It is a good plan to give wooden planes the shape shown 
by 3 and 4 in Fig. 17, as the disturbances mentioned 
above are not so marked.

.. figure:: images/Image18.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 18. An edgewise view of several planes showing the different ways they may be bent to secure stability.
   
   FIG. 18. An edgewise view of several planes showing the different ways they may be bent to secure stability.

The planes of large man-carrying machines possess the 
same characteristics, but not to such an alarming extent 
as in a model. The Voisin aeroplanes overcome the 
objection by the use of vertical panels set between the planes.

The angles at which the planes are set may vary from 
1 in 6 to 1 in 20. One in ten might be called the "happy 
medium." If the planes are given too great an angle, the 
drift becomes so great that the propeller thrust is 
severely taxed. The smaller the angle, the less will 
be the drift and consequently the greater the speed. 
However, if the surface is curved the angle must not be 
made too small or not much lift will result.

.. figure:: images/Image19.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 19. The various ways two planes may be combined to secure stability or form a biplane.
   
   FIG. 19. The various ways two planes may be combined to secure stability or form a biplane.

The angle of the tail planes should be adjustable. If too 
great, the machine will slow down and the tail will drop, 
destroying the equilibrium of the machine and consequently 
the flight. If the lift of the tail is too great, however, 
it will cause that part to rise and the machine will dive 
downwards.

**Elevators and Tails** are usually made of thin wood or fabric 
stretched over a rattan or wire framework. They are usually 
rectangular or elliptical in shape.

In case they are made of wood one of the best methods of 
attachment is to fasten the plane to a small stick by 
means of two or three small rivets. The stick is secured 
to the framework of the machine by two small rubber bands. 
Then in case the machine strikes head on in alighting, 
the band will absorb the shock and permit the elevator 
to move so that it is not damaged by the fall.

**Vertical Fins**. It is a much mooted question whether 
or not a vertical fin is of any value on a model aeroplane 
since a good model should be so designed that it will fly 
in a straight line without the use of a rudder. It has 
been the author's experience that it is often of decided 
advantage in correcting the flight of an "erratic machine" 
or in compensating any little difference that there may 
result in the drift of the two halves of the planes.

.. figure:: images/Image20.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 20. Fins.
   
   FIG. 20. Fins.

The fin should be placed well toward the rear of the machine 
and, whenever possible, stretched both above and below the 
centre line of the machine, so that the pressure due to 
cross winds will be equal both above and below and there will 
be no tendency for the machine to twist about its longitudinal axis.

When it is not possible to place the fin both above and below 
the centre line it should be placed above rather than below.

Fins may be made out of thin wood, sheet aluminum or 
fabric stretched over a wire or rattan framework.

CHAPTER IV. THE FUSELLAGE OR FRAMEWORK.
---------------------------------------

By the term "fusellage" or frames, that part of the aeroplane 
which serves as the "backbone" and to which all the other 
members are attached is implied.

The fusellage above all must be strong. The second requisite is 
lightness. The simplest frame for a model aeroplane is a 
long straight stick. The cross section of the stick may vary 
and be either round or square. A careful workman, however, 
can build them of "I" section like a steel girder. Increased 
lightness and strength is the result.

.. figure:: images/Image21.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 21. A simple "motor base" or fusellage.
   
   FIG. 21. A simple "motor base" or fusellage.

A single skein of elastic when wound up tends very strongly 
to twist the framework of the machine out of true. Since 
the tail and elevator are usually attached to the ends, 
the adjustment is thrown out to a marked degree and the 
flight of the machine is liable to be erratic.

We have tried building the fusellage of a network of girders 
such as the Bleriot and Voisin aeroplanes employ. Nothing 
could have been prettier than these carefully designed and 
constructed frames with their little struts and guy wires, 
but we soon found that for plain ordinary everyday efficiency, 
the simple stick is the best, provided, of course, that 
it is of the proper size to resist the twist of the rubber.

In some cases it is desirable to retain the framework because 
of the realistic appearance of the model to the larger 
machines which it gives. The only practical method then is 
to employ a plain stick backbone to withstand the torque 
of the rubber and build a false framework around it. The 
framework need only be strong enough to support the fabric 
and resist the shocks of landing. This method of construction 
is best suited to models of the Bleriot and Antoinette types.

The only type of frame consisting of a single member 
which will resist the torque of powerful rubber bands 
successfully is a tube. The rubber skein is placed 
inside the tube which may be of wood, paper or aluminum.

.. figure:: images/Image22.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 22. Paper Tube Fusellage.
   
   FIG. 22. Paper Tube Fusellage. Part of the tube is cutaway to show the rubber skein inside.

Paper tubes are excellent for small machines, being exceedingly 
light and very strong. They are formed by wrapping tough, 
unglazed paper around a rod of the required inside diameter. 
The paper is well smeared with glue and wrapped tightly. 
The rod is afterwards removed. Be sure that the glue is 
thoroughly dry before attempting to use the tube.

In larger machines it is preferable to employ some other 
means of avoiding the nuisance of a single skein rather 
than to use a tubular frame. There are several ways of 
accomplishing this, the best one undoubtedly being to 
balance the torque of one elastic by an equal torque 
tending to twist in the opposite direction.

.. figure:: images/Image23.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 23. Two methods of gearing a propeller.
   
   FIG. 23. Two methods of gearing a propeller.

In Fig. 23, a second skein of elastic is geared to the first 
with equal sized gear wheels. The second skein is placed 
immediately underneath the first and is equal in length 
and strength. Placing one skein under the other and 
not side by side as might be the first tendency allows 
the propeller to be arranged centrally. The lower part 
of the same figure illustrates a second method. In this, 
the propeller is attached to a long shaft, the other end 
of which is fitted with a gear wheel. Two elastic skeins 
of equal length and strength are attached to a second 
gear which meshes with the first. The only disadvantage 
of this form of motor is the long propeller shaft required. 
The objection, however, is sometimes outweighed by the 
fact that it is possible to employ a small gear wheel 
on the shaft meshing with a large one between the bands 
so that the action of the elastic is multiplied and a 
greater number of propeller revolutions secured where 
the length of the bands is limited and could not be 
increased in order to bring about the same result.

**Skids.** It requires only very little experience with 
model aeroplanes to prove the need of efficient skids 
on the machine. After the rubber band motor has run down, 
the propeller offers considerable resistance to the forward 
travel of the machine so that it does not glide properly 
and causes it to land on its "nose," often damaging 
the propeller or front planes. At the least, the 
framework of the machine is strained by such a shock.

.. figure:: images/Image24.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 24.
   
   FIG. 24.

Skids of course weigh something and offer a certain 
amount of resistance, but the advantages more than 
outweigh those drawbacks.

Skids are usually made of piano wire, split bamboo or 
rattan. The skids should not be made any larger 
than is necessary to protect the machine. They 
do not usually take any special shape but are formed 
to fit each individual case.

CHAPTER V. MOTIVE POWER.
------------------------

By far the simplest and most efficient form of power which could 
be installed in a model aeroplane to drive the propeller is a 
twisted skein of rubber. Nothing is lighter, or more easily 
handled and repaired.

The word *elastic*, in physics, is the name given to the 
tendency which a body exerts, when distorted, to 
return to its original shape. Rubber possesses more 
elasticity than any other material known, it being 
possible to stretch a piece of rubber cord to eight 
or nine times its original length without fracture. Rubber 
also possesses the added requisite of lightness and will 
store up more energy than any form of steel spring.

**The Simplest Form of Motor** is a single skein of elastic 
stretched between two hooks, one fixed and the other to 
which the propeller is attached, free to rotate. In some 
cases it is a decided advantage to divide the motor into 
one or more parts. One phase of this question has already 
been considered. The others will be discussed in the 
following chapter.

**The type of Elastic** which gives at once the longest life 
and the greatest power is the *square* rubber, preferably 
about 3/32 x 3/32 inches, and not the flat strip. When 
examined under the microscope the edges of the square rubber 
show to be cleaner and sharper and not so ragged as those of 
the flat strips. To be of any value for use in a model 
aeroplane, the rubber should be absolutely pure and fresh.

There are certain precautions which if observed will add 
greatly to the power and efficiency of a rubber band motor.

Always remove the elastic from the machine when the flights 
are over for the time being. Rubber spoils very quickly 
when kept under tension. It also deteriorates if warm, 
so keep in a cool place. Strong sunlight causes rubber 
to harden and lose its elasticity, due to the presence of 
the sulphur used in vulcanizing. If talcum powder or finely 
powdered soapstone is rubbed on the bands from time to 
time it will prevent them from sticking together. The 
strands will then run and slip more easily upon each 
other, making it possible to store up a greater number of 
propeller revolutions.

In spite of the use of talcum powder, however, when a skein 
of rubber is twisted very tightly, the strands stick together, 
causing it to soon break up.

This nuisance may be somewhat alleviated if the strands are 
lubricated with *pure redistilled* glycerine free from grease, 
etc. Such a precaution will not always greatly lengthen 
the life of the rubber, but will increase the number of turns 
which it is possible to give the skein (and this is a very 
important advantage in model contests). Due to its sticky 
nature, however, the glycerine will cause the rubber to gather 
dust and particles of dirt which, if allowed to grind into 
the rubber, would soon weaken it. The skein should therefore 
be washed from time to time in warm soda and water and 
fresh glycerine applied. By all means, avoid all oils or 
substances of a greasy nature, such as lubricants. They 
quickly soften and rot the rubber.

**The Amount of Elastic** required for a model will vary 
considerably for propellers of the same pitch and diameter. 
There is always a tendency to use too much rather than 
too little and this fault should be carefully guarded 
against. In nine cases out of ten it is the cause of 
the unsatisfactory behavior of a model.

The motor should always be "stranded," that is, made 
up of a skein of bands. It is then possible to secure 
a larger number of turns than if a single strip were used.

Always start a new machine with a small number of strands 
and gradually add to the number until the proper amount of 
power is obtained. The distance between the propeller and 
the fixed hook should always be as great as possible so 
as to secure the maximum number of turns.

**Doubling the Number of Elastic Strands** increases the 
power of the motor but cuts down the number of turns 
which it is possible to give the propeller. That is 
to say, a certain skein composed of six strands of rubber 
will take perhaps two hundred and twenty-five turns 
while a twelve strand skein of he same sized rubber strands 
strands is only capable of less than half or about one 
hundred turns before it is wound tight.

Doubling the number of strands and at the same time keeping 
them the same length increases the torque more than three 
times but diminishes the number of turns from one-half to one-third.

**Doubling the length** of the strands does not materially 
reduce the torque for the first hundred turns. After 
two hundred turns have been reached, the torque is only 
about one-half as great as it would be in case the length 
were not doubled.

Doubling the length of the strands doubles the number 
of turns it is possible to give the skein. It is easy to see 
from this why it is always advisable to make the 
*motor as long as possible* and to compose it of the 
fewest number of strands if long flights are desirable.

By using several separate skeins geared together so as to 
apply their energy to one screw, it is possible to obtain 
a greatly increased number of turns. The weight of the gearing 
is very small and hardly a factor, considering the advantages 
derived therefrom. Since the skeins revolve in opposite 
directions the frame of the machine is relieved of the harmful 
twisting effect so often present in a single skein.

The gears should be of steel accurately cut and of no 
larger diameter than is necessary to separate the rubber 
skeins the requisite distances so that they will not rub.

Holes may be bored in the gears to lighten them. The 
gears are easily and conveniently cut out of steel pinion wire.

CHAPTER VI. SCREW PROPELLERS.
-----------------------------

We might compare a propeller to an ordinary screw or bolt 
by likening the thread of the screw to the two blades 
of the propeller. If the screw penetrates wood or metal 
nut it will advance a certain distance known as the 
*pitch* which is always the same, namely, the distance
separating two consecutive turns of the threads. The 
revolving blades of the propeller cut their way through 
the air in identically the same manner. But since air 
is a very thin medium as compared to wood or iron 
the propeller slips a little just like a screw going 
into an unsteady nut and does not advance the distance 
it theoretically should considering the angle of the 
blades. The distance lost in each revolution is 
called the *slip*. Thus a screw having a ten-foot 
pitch in actual operation perhaps only advances the 
aeroplane eight feet.

.. figure:: images/Image25.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 25.
   
   FIG. 25.

If a propeller blade had a uniform angle throughout 
its entire length the portions of the blade near 
the centre would not have as great a pitch as the 
extreme tips because the diameter of the circle they 
travel in one revolution is not as great as that at 
the tips. For this reason it is usual to give 
the blades an increasing angle as they approach 
the centre.

.. figure:: images/Image26.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 26. Method of laying out a screw propeller, that is, determining the angle of the blades at different points.
   
   FIG. 26. Method of laying out a screw propeller, that is, determining the angle of the blades at different points.

Fig 26 shows a diagram illustrating the theoretical 
pitch of a screw, the angle of the blade varying 
inversely as its radial distance from the centre 
of the screw.

When a propeller revolves it sets in motion a cylinder 
of air. If the angle of the blades is uniform 
throughout their length the air in the centre of 
the cylinder will move much more slowly than that 
near the outside as shown by the arrow heads in A 
of Fig. 27. If the blades are given an increasing 
pitch, the air in all parts of the cylinder will 
move away from the propeller at the same speed.

From a diagram like this it is very easy to calculate 
the angle of a blade at any point to secure a certain 
pitch. Suppose that the problem in hand is to design 
a propeller eight inches in diameter and a pitch of 
twelve inches. On a sheet of paper draw a vertical 
line AM twelve inches long to represent the pitch. 
Draw a long horizontal line AN of indefinite 
length from the lower end of AM and at right angles 
to it. The diameter of the propeller being eight 
inches, the tips of the blades must travel in one 
revolution 8 x 3.1416 (the circumference of an 
eight inch circle in inches), a distance of 33.1 inches. 
Lay off on AN the distance AB which is 33.1 inches, 
draw the line MB. The angle MB forms with AN is the 
proper angle for the blades at the tips. To find 
the angle one inch from the tips lay off the 
distance AC, which is. 8 - 2 x 3.1416 or 24.8 inches. 
MC gives the right angle. The angle two inches 
from the tip would be shown by MD where AD is 
8 - 4 x 3.1416 or 18.8 inches. Any other points 
can be located in the same manner.

.. figure:: images/Image27.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 27. A propeller of the truly helical type delivers a cylinder of air in which all parts move at the same speed as at A.
   
   FIG. 27. A propeller of the truly helical type delivers a cylinder of air in which all parts move at the same speed as at A. A propeller having blades of the same angle throughout their length throws the air as in B in which the centre of the cylinder moves more slowly than the outside.

.. figure:: images/Image28.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 28. Templets for testing and carving a propeller.
   
   FIG. 28. Templets for testing and carving a propeller.

If desirable, a number of small templets having 
the proper angle may be cut out of sheet tin and 
fastened to a board as shown in Fig 28. When 
making the propeller it can be frequently laid 
on the templets to see if the proper angle has 
been secured yet.

There are a great many other ways of making 
propellers for model aeroplanes, the simplest 
and best of which are described below.

**Metal Propellers** have advantages and disadvantages 
which may be summed up only to find that as far 
as efficiency is concerned the advantages outweigh 
the disadvantages.

.. figure:: images/Image29.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 29. A simple method of forming a propeller from sheet metal.
   
   FIG. 29. A simple method of forming a propeller from sheet metal.

The simplest method of making a small metal propeller 
is to cut a piece of sheet aluminum into the shape 
shown by A in Fig. 29. Fold along the dotted 
lines so that the result is like B in the same 
illustration. The shaft may be a small piece of 
piano wire passed through the hole in the centre 
and bent around as shown.

.. figure:: images/Image30.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 30. A built-up metal propeller made of aluminum. 
   
   FIG. 30. A built-up metal propeller made of aluminum. 

Another method of making a metal propeller which is 
more suitable for large machines than that just 
described is illustrated in Fig. 30. The blades 
are cut out of sheet aluminum to the shape shown 
and set in the slots in the end of a small aluminum 
tube. They are held in position with aluminum solder. 
Ordinary solder will not accomplish the work and cannot 
be used. The shaft is soldered into a hole in the 
tube halfway between the two blades.

.. figure:: images/Image31.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 31. Metal Propeller.
   
   FIG. 31. Metal Propeller.

The propeller shown in Fig. 31 is extensively used by 
manufacturers of model aeroplanes because of its simplicity 
and strength. The propeller is cut out of sheet aluminum 
and then bent and folded. The shaft is held in place 
by a brass eyelet riveted firmly over on both sides.

.. figure:: images/Image32.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 32. Method of carving a propeller of the truly helical type. 
   
   FIG. 32. Method of carving a propeller of the truly helical type. 

**Wooden Screws**. Single piece screws cut out of a block 
of wood are easy to make and very efficient. The propeller 
is laid out on a square or rectangular strip of wood 
(according to the pitch), cut to the required length. A 
pocket knife or a wood rasp is used to rough the wood down 
to the shape shown at B. It is then finished down to 
the form shown at C. After rubbing with sand-paper a 
coat of varnish is applied and allowed to dry. The 
varnish is then rubbed down to a smooth surface.

.. figure:: images/Image33.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 33. Methods of fastening propellers to shaft.
   
   FIG. 33. Methods of fastening propellers to shaft.

Fig. 33 shows a very good method of mounting the 
propeller on the shaft. A piece of stiff brass 
is soldered to one end of a bicycle spoke and 
bent around the propeller. A small nut made by 
cutting a spoke nipple is screwed on the end to 
hold the propeller in position. (The same 
illustration shows another very good method of 
fastening the propeller to the shaft. The end 
of the shaft is filed to a sharp point, bent 
into the shape shown in the illustration and 
then driven into the propeller. A small pin hole 
should be made in the propeller at the place 
where the sharp point is to enter in order 
to avoid the possibility of splitting.)

.. figure:: images/Image34.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 34. Method of forming sockets for joining struts, etc., by cutting from sheet metal.
   
   FIG. 34. Method of forming sockets for joining struts, etc., by cutting from sheet metal.

There are two methods of making propellers by steaming 
and bending thin wood. American whitewood and spruce 
are the best woods for the purpose. After steaming 
place one end of the strip in a vise and holding the 
other in the fingers twist it into the right shape. 
Fasten it in position and allow it to remain so until 
dry. Then give it a coat of varnish to prevent the 
absorption of moisture and consequent warping. The 
method of fastening the shaft, which in this case is 
a piece of piano wire or a bicycle spoke is illustrated 
in Fig. 35. Two small pieces of wood shaped like a 
half cylinder and having a groove cut on the curved 
surface are glued on either side at the centre. 
The shaft is then bent around and twisted.

.. figure:: images/Image35.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 35. Bent wood propellers and the methods of fastening them to the shaft.
   
   FIG. 35. Bent wood propellers and the methods of fastening them to the shaft.

.. figure:: images/Image36.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 36. Propeller blank (top). Carved propeller (bottom). 
   
   FIG. 36. Propeller blank (top). Carved propeller (bottom). 

In order to make the second type the wood must 
first be bent into shape. It is steamed and bent 
along the dotted lines. It is attached to the 
shaft by means of a piece of sheet brass 
doubled over the edge and soldered to the 
end of a bicycle spoke. The only disadvantage of 
this form of propeller is that it is easily broken. 
It turns very easily with little expenditure of power.

.. figure:: images/Image37.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 37. Langley type propeller (top). Wright type propeller (bottom).
   
   FIG. 37. Langley type propeller (top). Wright type propeller (bottom).

**Size of Propeller.** One bad feature about most of the 
model aeroplanes offered for sale in toy shops is 
the propeller. In almost every case it is decidedly 
too small. In order for a model to fly really well 
the propeller must usually be out of all proportion 
to the rest of the machine. In fact its size will 
make the machine appear very awkward and unsightly.

.. figure:: images/Image38.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 38. Quasi-helical propeller.
   
   FIG. 38. Quasi-helical propeller.

The enormous slip of small screw propellers when 
turning rapidly makes them very inefficient. The 
thrust of the propeller is dependent upon the 
volume of air sent backwards. A large propeller 
naturally deflects more air than a small one 
and so in order for the latter to equal the 
work of a large propeller it must either have 
an increased pitch or revolve more rapidly.

.. figure:: images/Image39.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 39. Blanks for racing (top) and chauviere (bottom) propellers.
   
   FIG. 39. Blanks for racing (top) and chauviere (bottom) propellers.

A small pitched propeller is less wasteful of 
power than one having a high pitch and so it 
is of no advantage to make a small screw do the 
work of a larger one. It is not only wasteful 
of energy but also permits the rubber skein to 
untwist too rapidly. The advantage therefore 
lies with a propeller of low pitch driven slowly.

.. figure:: images/Image40.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 40. The first step in carving a propeller. The blank. Hollowing the first blade.
   
   FIG. 40. The first step in carving a propeller. The blank. Hollowing the first blade.

.. figure:: images/Image41.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 41. One blade hollowed. Hollowing the second blade. 
   
   FIG. 41. One blade hollowed. Hollowing the second blade. 

The average propeller should have a pitch of from 
2-3 times its diameter, that is, the blade should 
have an angle at the tips of slightly less than 
45 degrees.

The propeller diameter (of course this rule is 
not infallible, but only a general statement) 
should be about one-third the spread of the planes.

The edges of the blades should come to a clean 
edge but not be too sharp.

.. figure:: images/Image42.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 42 Rounding the back of the first blade. Rounding the back of the second blade.
   
   FIG. 42 Rounding the back of the first blade. Rounding the back of the second blade.

One of the best means of determining the efficiency 
of a propeller is to connect it to a small electric 
motor which will drive it at high speed and by 
blowing tobacco smoke around it or holding a piece 
of burning rag nearby and test whether or not the 
air is thrown out from the sides by centrifugal 
force. A correctly designed propeller will pull 
air in from the sides instead of throwing it out.

.. figure:: images/Image43.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 43. All carving finished. Sandpapering to secure a smooth surface.
   
   FIG. 43. All carving finished. Sandpapering to secure a smooth surface.

Calculation in fitting a model with a propeller is 
almost useless. The experimental error is so large 
that the empirical or "cut and try" method is the 
only reliable one. It is best to make a number of 
propellers of varying pitch and diameter and give 
to each a thorough tryout on the machine before 
making a decision.

**The Single Screw Machine.** A propeller placed in 
the rear of a machine is usually more efficient than 
a "tractor" screw placed in front. A machine drags 
along considerable air with it (due to skin friction 
of the planes, etc.), and so a screw placed in the 
rear revolves in air which is really traveling with 
the machine itself and so the effect is somewhat as 
though it were traveling with the wind. A further 
advantage of placing the propeller in the rear of 
the machine lies in the fact that there is less 
likelihood of damage in landing.

.. figure:: images/Image44.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 44. Varnishing. The propeller finished.
   
   FIG. 44. Varnishing. The propeller finished.

An aeroplane having a single screw always betrays 
a marked tendency to turn completely over in a 
direction opposite to that in which the screw is 
rotating. Action and reaction are always equal and 
opposite in their effects and so the motor has a 
tendency to rotate the machine against the 
resistance of the screw as well as to rotate the 
screw against the resistance of the machine.

One way in overcoming this difficulty is to set 
the two halves of the plane at a slight angle to 
one another or at a *dihedral* angle as it is 
called. Then if the machine tends to twist and 
turn over the lifting power of the lower wing 
becomes greater as it approaches the horizontal while 
that of the other wing grows less. Accordingly 
the machine resists and tends to turn back to its 
normal position.

Another method is to keep the weight or centre of 
gravity as low as possible so that the machine will 
automatically right itself as soon as it begins 
to turn. The objection to this, however, is that 
the machine will fly very unsteadily on a gusty day 
(and most days are more or less gusty). The effect 
of placing the centre of gravity low is shown in 
Fig. 45. The dotted line represents the centre 
of pressure acting against a plane P. The weight 
of the machine is centred at W. Imagine the machine 
in flight. Then the resistance of the plane P 
acting along the dotted line will tend to stop the 
machine while W tends to still go forward because 
of its inertia. As a result, the front of the 
machine tilts upwards and increases the angle of 
P, which in turn increases the resistance. The 
machine therefore slows down but W tends to 
still move forward and tilt the machine further 
until the thrust of the screw is unable to 
support the weight and so W swings back down 
and beyond the position shown at B. The angle 
of P decreases, the machine travels forward 
quickly and gathers sufficient speed for W to 
swing up again. Thus the performance is repeated 
and the machine will have a flight path very 
much like the dotted line shown in the lower 
part of the illustration. The motion is slight 
but is sufficient to considerably shorten the 
length of the flight.

.. figure:: images/Image45.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 45. Accentricity. The effect of placing the center of gravity too low. 
   
   FIG. 45. Accentricity. The effect of placing the center of gravity too low. 

If the machine meets wind, the motion is somewhat 
increased. In fact the author has seen a small 
biplane turn completely over and actually "loop 
the loop." When the machine flies with the wind 
the effect is largely reduced. If the wind is of 
just the right strength and comes from the rear, 
the machine will fly quite steadily. If too 
strong, however, the model will dive to the ground. 
A tail somewhat dampens the swing while an elevator 
will slightly increase it.

The only other methods of partially mitigating the 
evils of a single screw are to ballast the machine, 
that is, place a weight on one side or to give one 
plane an increased sustaining surface. The first 
may be dismissed immediately because the weight will 
cause one side of the machine to drop as the elastic 
runs down and the reaction of the propeller becomes 
smaller. The last named method is the usual one employed. 
The wing on that side of the machine opposite to which 
the propeller is revolving is given a larger surface 
than the other and so exerts a greater lift on that 
side. This also has disadvantages, however, for by 
giving one wing a greater lifting power the machine 
is caused to fly in a long spiral path when the 
propeller begins to run down and when it stops 
completely to glide in the same manner.

.. figure:: images/Image46.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 46. Simplest method of fitting two propellers to a model aeroplane.
   
   FIG. 46. Simplest method of fitting two propellers to a model aeroplane.

The propeller should be placed as nearly as possible 
on a level with the planes. The *centre of pressure* 
on the planes and the centre of gravity should 
coincide if true stability is desired. The centre 
of pressure on a machine having the planes set at 
a dihedral angle is halfway between the lowest point 
and the highest providing the planes are the same 
width all the way along. If they taper towards the 
ends it is slightly lower while if they are wider 
at the extremities it is higher. The rubber skein 
and the propeller are usually placed on top of the 
fusellage of a dihedral winged machine.

**The Double Propeller Machine.** The best method 
and the only one which entirely removes the 
difficulty is to fit the machine with two 
propellers. A machine having two propellers 
to the author's mind is the only one worth much 
attention.

Fig. 46 illustrates the simplest arrangement 
for fitting two propellers to a machine. In the 
first a second propeller is attached to the 
other end of the skein. At first it might seem 
in the second arrangement that there would be 
difficulty in getting the screws to revolve at 
the same speed. However, if the propellers are 
similar and the same number of rubber strands 
employed to drive each, the difference will be 
so small as to be negligible.

When the first arrangement is employed the pitch 
of the screw in the rear must be slightly greater 
than that in the front because it is revolving 
in the slip of the latter.

Placing both propellers on a double shaft on the 
same axis has the disadvantage of decreasing the 
efficiency of the propellers because they are 
operating in each other's draft.

.. figure:: images/Image47.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 47. A method of arranging two propellers on the same axis.
   
   FIG. 47. A method of arranging two propellers on the same axis.

The first of these methods is undoubtedly the best 
construction. It is then possible to use the same 
rubber skein to drive both propellers. Also any 
possible difference in their speed will not so 
readily cause the machine to change its course 
as if the propellers were alongside of each other. 
When two propellers are used in this latter 
position it is a very good idea to fit them with 
two small pulleys and a connecting belt so that 
any tendency for a difference in speed between 
the two will be immediately equalized.

The power absorbed varies directly with the volume 
of air acted upon and the square of the speed with 
which it moves away. If the pitch of the propeller 
or its rate of revolution were doubled, four times 
the power previously required would be necessary. 
Vice versa, decreasing the rate of revolution or 
the pitch by one-half will make only one-fourth the 
power previously required necessary.

Doubling the speed and doubling the diameter requires 
eight times more power. Doubling the diameter, 
halving the pitch and halving the speed will give 
twice the thrust for the same power as in the first case.

CHAPTER VII. BEARINGS, THRUST BLOCKS AND GEARS.
-----------------------------------------------

Since the power available for driving the model is 
very limited it is obvious that every precaution 
should be taken to enable the propeller to absorb 
every last fraction of energy stored in the motor. 
With this end in view the bearing or thrust block 
in which the shaft of the propeller revolves should 
receive careful attention in order to remove as 
far as possible all causes which would result in 
friction.

.. figure:: images/Image48.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 48. Simple bearings. 
   
   FIG. 48. Simple bearings. 

The simplest form of bearing is a simple piece of 
sheet brass or aluminum having a hole drilled 
through it and bent up at right angles so that 
it may be lasted to the frame as shown in Fig. 48 by A.

Single bearings of this type are employed on the 
model aeroplanes manufactured by toy makers whose 
only desire is to flood the department stores and 
toy shops around Christmas time with their impossible 
machines. Such single bearings are a decidedly poor 
and unsatisfactory construction. Unless the elastic 
is very short it soon begins to vibrate in unwinding. 
Since the rubber is directly connected to the propeller 
shaft, the propeller is set into vibration as shown 
by the dotted lines in the second part of Fig. 48. 
The long blades of the propeller considerably 
magnify the motion and there is a very appreciable 
loss of power due to the erratic path of the propeller 
and the increased friction at the bearing. The rubber 
skein also offers considerably more resistance to 
the forward travel of the machine than if it were 
not in vibration.

.. figure:: images/Image49.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 49. Double bearings. 
   
   FIG. 49. Double bearings. 

The advantage of a double bearing more than offsets 
the added weight. Such a bearing is formed out of 
a piece of sheet brass bent up at right angles at 
both ends as in Fig. 49. The third method of 
construction in the accompanying figure makes it 
possible to employ lighter sheet metal in the 
construction of the bearing and still resist the 
pull of the rubber and the thrust of the propeller 
successfully.

.. figure:: images/Image50.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 50. Simple thrust bearing.
   
   FIG. 50. Simple thrust bearing.

**Friction is reduced** and the thrust taken up by 
placing one or two glass beads between the 
propeller and the bearing. Only those beads 
which are flat, with parallel sides and have 
a round hole in the centre, should be used.

Four or five copper washers or rings may be 
made to serve the same purpose with equally 
good results.

Another method is to employ two washers separated 
by a small spiral spring. Such an arrangement 
is employed on some of the French models and might 
be called a "friction thrust." That is, when the 
rubber skein is wound up tight and the propeller 
is released the friction acts as a brake and 
reduces the speed, preventing the propeller from 
"racing." As the elastic unwinds, the tension, 
and with it also, the friction becomes less so 
that the propeller revolves more rapidly and 
maintains a somewhat even speed. The importance 
of preserving as far as possible an even propeller 
speed can hardly be overestimated and that is 
why such emphasis has been laid in several 
places upon the desirability of a model whose 
propeller is driven by a long skein of rubber 
composed of the fewest possible number of strands.

.. figure:: images/Image51.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 51. Ball thrust bearing. 
   
   FIG. 51. Ball thrust bearing. 

**Ball bearing** thrusts are by all means the most desirable, 
but not all models are large enough to accommodate 
their size and weight. Wherever it is possible, 
however, to use them it should be done. The 
increased amount of energy available for turning 
the propeller will make it possible to employ less 
rubber and so increase the number of turns and 
consequently the length of the flight.

.. figure:: images/Image52.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 52. Hooks.
   
   FIG. 52. Hooks.

**The hooks** at either end of the rubber skein are 
apt to cut the rubber unless some precautions are 
taken to prevent it. This can be done by binding 
with cotton thread or slipping a piece of rubber 
tubing or aluminum over the hook as shown in Fig. 52.

CHAPTER VIII. BUILDING AND FLYING MODEL AEROPLANES.
---------------------------------------------------

The Blerioplane Flyer. (Plate II.) 
``````````````````````````````````

The Blerioplane Flyer is of the simple 
monoplane type and is very easily constructed. It 
is a remarkable flyer when properly adjusted and 
will fly over one hundred and fifty feet.

The motor base is a piece of 3/16 dowel, 12 inches 
long. The edges of the planes are made of fine 
steel piano wire bent to the shape shown in Plate I. 
The planes are covered with silk which is carefully 
turned over at the edges, around the wires and 
fastened either by sewing or with bamboo varnish. 
The dimensions of the planes are clearly shown in 
the illustration.

.. figure:: images/Plate4.jpg
   :align: center
   :scale: 85 %
   :alt: Plate IV.
   
   Plate IV.

The propeller is placed at the rear of the machine, 
the smaller plane being considered the elevator. 
The bearing is shown in detail in the accompanying 
illustration. It is made by folding and bending a 
piece of sheet brass into the shape shown. A piece 
of steel piano wire is passed through the forward 
end of the motor base to act as an anchor hook for 
the rubber band.

The propeller is easily wound up by hand.

One side of the main plane will have to be made slightly 
larger than the other in some cases in order to counteract 
the twisting action of the propeller by one side of 
the machine more of a lift than the other.

The planes are adjusted by bending the wire edge. 
They should form a slight dihedral angle. The rubber 
strands lie along the top of the motor base so as to 
bring the centre of the propeller thrust coincident 
with the centre of pressure on the planes. Bending the 
front edge of the planes down will cause the machine 
to take a downward path while bending them up will 
cause the aeroplane to fly higher. A little 
experimental work will determine the proper position.

The Monoplane Flyer. (Plate III.)
`````````````````````````````````

The fusellage or "backbone" of the 
machine is formed out of a piece of thin walled 
aluminum tubing having an outside diameter of 
one-quarter of an inch and measuring twenty-four 
inches long.

The framework of the planes is formed out of rattan 
reed, one-eighth of an inch in diameter. The main 
plane is 19 inches across from tip to tip. It is 4 
inches deep at the centre and 5 1/2 inches at the 
widest point near the tips. The framework is spread 
near the centre of each wing by a piece of rattan 
reed 5 1/4 inches long. The ends of the reed are 
joined by rolling a small piece of copper sheet 
into a tube and closing it around the reed tightly 
with a pair of pliers.

The reed forming the frame of the plane passes 
through a hole in the aluminum tube.

.. figure:: images/Plate5.jpg
   :align: center
   :scale: 85 %
   :alt: Plate V.
   
   Plate V.

The plane forming the tail is almost the same in 
all respects save that of size as the forward main 
plane.

A small vertical fin 3 inches wide and 3 1/2 inches 
deep is placed below the tail plane, in line
with the "backbone" to act as a keel or rudder 
and hold the machine to a straight course.

The covering of the planes is China silk or 
bamboo paper coated with bamboo varnish.

The bearing is made out of sheet brass bent 
into the shape shown and fastened to the tube 
by lashing with a wire.

The propeller should be 6 inches in diameter. 
One or two glass beads placed between the bearing 
and the propeller will reduce the friction.

The motive power consists of 8 strands of 3/32 
x 3/32 inch rubber connected at one end to the 
propeller and at the other to a hook at the rear 
end of the aluminum tube.

The machine is provided with two piano wire skids 
to protect the propeller in landing.

If the aeroplane tends to rise too abruptly when 
in flight, bend the rear edge of the main planes 
up. If on the contrary, it dips or dives, bend 
the rear edge down.

The Baby Racer. (Plate IV.)
```````````````````````````

This is one of the smallest and simplest machines 
of the twin propelled racing models. The two 
main members of the motor base or fusellage 
are 1/8" x 1/8" in section and 5 1/2 inches long. 
One end of each is tapered and then glued and 
bound with strong thread. The opposite ends are 
held apart by a brace made from flat steel wire. 
The wire is hammered out flat at the ends and 
drilled with a small hole to form a propeller 
bearing. The details of the brace are given in 
the upper right-hand corner of the plate. The 
brace is fastened to the sticks by lashing with 
thread.

It is well to place a small wooden brace across 
the frame about midway of its length. This will 
serve to considerably stiffen the frame and 
prevent it from sagging under the tension of 
the rubber bands.

.. figure:: images/Plate6.jpg
   :align: center
   :scale: 85 %
   :alt: Plate VI.
   
   Plate VI.

The planes are cut from stiff paper. The main 
plane is 7 1/4 inches across and the elevation 
plane 2 3/4 inches. Each plane is cut to the 
shape shown in the drawings and stiffened by gluing 
a thin wooden strip across the front edges of 
the planes.

A small piece of steel wire is passed around the 
front end of the frame and bent to form two 
anchor hooks for the rubber bands. It is then 
lashed firmly into position and the thread 
covered with glue so that it will not untwist 
if broken.

The propellers are made from thin whitewood 
or veneer. They are four inches in diameter 
and formed by steaming and bending. The shaft 
is formed out of brass wire by bending it 
around the centre of the propeller. Two small 
beads are slipped over the shaft to eliminate 
friction between the propeller and the bearing.

The planes are held in position by small rubber bands. 
The sketches in Fig. 53 explain exactly how this is 
accomplished.

.. figure:: images/Image53.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 53. Method of holding plane to frame with rubber bands.
   
   FIG. 53. Method of holding plane to frame with rubber bands.

The sticks glued along the front edges of the planes 
are sufficient to give them a slight angle. The 
machine is controlled by moving the planes back 
and forth so as to shift their lifting effort to 
the proper position.

.. figure:: images/Plate7.jpg
   :align: center
   :scale: 85 %
   :alt: Plate VII.
   
   Plate VII.

The motor consists of two strands of 3/32 x 3/32 
rubber attached to each propeller.

The Peerless Racer. (Plate V.)
``````````````````````````````

This excellent flyer is very simple to put together 
and by carefully following the directions anyone 
can construct the machine and obtain splendid flights.

The two long members of the frame or fusellage, 
marked "A" and "B" in the drawing are 36 inches 
in length. They measure 1/4 x 3/16 in cross section.

Bevel one 1/4 inch side of one end of each of the 
two long sticks so that they can be joined to form 
an angle as shown in the upper right hand corner of 
the accompanying plate. The tip should not be greater 
than one quarter inch in width after joining. Glue 
the ends together using plenty of glue and before 
it has set, bind with strong linen thread, starting 
at the tip and winding back for about one inch. 
The surplus glue will squeeze out between the threads 
and when hard prevent them from unwinding if broken.

An aluminum brace must be made by flattening the ends 
of a piece of 1/8 inch aluminum rod. The rod should 
be about 5 1/4 inches long so that when the brace is 
placed 5/8 of an inch back from the ends of the sticks, 
the distance between them will be about 4 3/4 inches.

Glue and bind a small wooden cross brace to the 
frame, 12 inches from the rear end. The brace should 
be made 3/16 of an inch wide and 3/32 of an inch thick.

The elevating blocks are 3/4 of an inch long, 3/16 of 
an inch thick, 3/8 of an inch high at the rear and 1/2 
inch high at the front. They should be fastened to 
the machine by gluing and binding six inches back from 
the tip. The highest part of the blocks should be 
towards the front of the machine as shown in the 
illustration. Be careful to see that the frame is 
lined up perfectly true and then lay it aside until 
the glue dries.

.. figure:: images/Image54.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 54. The Peerless Racer. 
   
   FIG. 54. The Peerless Racer. 

The propeller bearings are made from No. 18 hard 
sheet aluminum. It is cut into a strip 1/4 of an inch wide 
and then drilled and bent as shown in the accompanying 
illustrations. The bearings are screwed on the rear ends 
of the sticks "A" and "B." It is also a good plan to 
bind some linen thread around tightly. 

Pass the propellers through the bearings and bend the 
end of the shaft into the shape of a hook, being very 
careful not to twist the bearings during the operation. A 
bead should be slipped over the propeller shaft previous 
to passing it through the bearing so that it comes 
between the bearing and the propeller and lessens the 
friction. 

Bore a small hole through the frame of the machine 1/2 
inch back from the tip, making the hole pass from 
side to side. Pass a piece of stiff wire through 
this hole and bend back each end snugly to the frame 
to form the anchor hooks as illustrated. Bind some 
thread over the anchor hooks to keep them from twisting.

Bend two small pieces of wire into "S" shaped hooks 
and slip one over each of the anchor hooks.

.. figure:: images/Plate8.jpg
   :align: center
   :scale: 85 %
   :alt: Plate VIII.
   
   Plate VIII.

Pass the rubber skein through one of the "S" hooks 
and back to the hook in the end of the propeller shaft, 
weaving it back and forth seven times so that there 
are seven strands. Do the same with the other 
propeller. The ends of the rubber must be tied to 
the hook with some strong cotton cord. The cord 
should be soft and the rubber should be passed 
loosely around the hook so that it will not easily 
become cut.

The planes are made of hard fibre 1/32 of an inch 
thick. The main plane is 22 inches long and 3 1/2 
inches wide. The elevating plane is 8 inches long 
and 3 1/2 inches wide. The ends are rounded as shown 
in the illustration. Glue a strip of wood 1/16 x 3/16 
inches to the front edge of each plane. The strip 
for the large main plane should be 19 inches long 
and that for the elevating plane 5 inches. The 
edges should be smoothed with a piece of fine 
sandpaper and rubbed down until they are dry.

The planes are attached to the frame by rubber 
bands in the usual manner. The edges of the 
planes should be squeezed together slightly 
until they are slightly concave on the under 
side. The position of the main plane will have 
to be determined by trial. The front edge of 
the elevating plane should rest on the 
elevating blocks.

The propeller should be given from 600-700 
turns. The propellers should be six inches 
in diameter and of medium pitch.

The Peerless Racer is a splendid flyer and 
will fly over 1,000 feet if properly adjusted.

The Competition Flyer. (Plates VI and VII.)
```````````````````````````````````````````

The Competition Flyer does not differ materially 
from the Peerless Racer just described except in 
some of the details of construction. The motor 
base of the machine is composed of two long 
members 36 inches in length tapered and lashed 
together at one end in the usual manner. The other 
ends are held apart by a wooden brace (marked a) 
about 4 7/8 inches long. Two other braces 
(marked b and c) are placed at equal distances 
along the frame.

The bearings used on this machine are similar 
to those used on the Peerless Racer and are 
fastened to the rear end of the frame by three 
small screws.

.. figure:: images/Plate9.jpg
   :align: center
   :scale: 85 %
   :alt: Plate IX.
   
   Plate IX.

The planes of this machine are "built up" planes, 
that is, they are double surfaced. The main 
plane is 24 inches long and four inches broad.

The accompanying illustration shows the details 
of the planes. The long members of the planes 
are made of whitewood or spruce and the edges 
and ribs are split bamboo.

The elevating plane is 9 1/2 inches long and five 
inches wide.

The planes are covered with bamboo paper and 
then given a coat of bamboo varnish. The front 
plane is tilted upwards by two small elevating 
blocks similar to those used on the Peerless Racer.

The machine is fitted with skids made by 
bending 3/32 inch square split bamboo into the 
shape shown and lashing them to the frame. The 
skids protect the planes and the propeller 
of the machine from possible damage in landing.

The propellers should be of the racing type, six 
inches in diameter and carved out from a blank 
in the method described in the chapter on propellers.

The planes are held to the frame of the machine 
by rubber bands in the usual manner. Their exact 
position will have to be determined by experiment.

The Long Distance Racer. (Plates VIII and IX.) 
``````````````````````````````````````````````

The Long Distance Racer is a model adapted from the 
Competition Flyer and similar to it in many respects.

The drawings show the dimensions and arrangement 
of the various parts sufficiently well so that 
little comment is necessary.

The planes are of the built-up type, being made 
entirely from split bamboo according to the size 
and shape shown in the drawings. They are covered 
with bamboo paper and given two coats of bamboo 
varnish.

The propellers are of the racing type and carved 
from wood in the manner described in the chapter 
on propellers.

.. figure:: images/Plate10.jpg
   :align: center
   :scale: 85 %
   :alt: Plate X.
   
   Plate X.

The machine is fitted with skids to prevent possible 
damage to the propeller and planes. The front plane 
is bent so as to form a slight dihedral angle. 
This tends to make the machine keep to a straight 
course.

.. figure:: images/Image55.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 55. Racing blank and propeller. 
   
   FIG. 55. Racing blank and propeller. 

The rubber skeins are each composed of 7 to 10 
strands of 3/32 x 3/32 inch rubber. The best 
number will have to be determined for each 
particular machine.

Fleming-Williams Flyer. (Plate X.) 
``````````````````````````````````

The Fleming-Williams model is a type well 
known in England where it has won many 
prizes. The motor base is a piece of "T" section 
wood 48 inches long. The detailed dimensions 
of the "T" section are given on the plate. 
A crosspiece B, 5/16 square and 8 1/2 
inches long is fastened at one end of the 
motor by gluing and lashing as shown in 
the drawing.

Two braces, C, C, 1/8 x 1/4 inches in section 
are lashed near the ends of the cross piece 
and brought together on the motor base so 
as to form a triangle. This is covered 
with bamboo paper to form a triangular 
shaped plane called the stabilizer.

The bearings are simple strips of hard 
sheet aluminum bent around the ends of 
the cross brace and fastened into 
place with several small screws.

The main plane is formed by bending 1/32nd 
inch drill rod into the shape shown in the 
detailed drawing on the plate. Mark out the 
wing form on a board, and by means of nails 
driven into the board around the outline, bend 
the drill rod into shape, splicing the ends 
neatly with some fine wire. Then bend the 
ribs into shape and twist the ends around 
the wing form. It is a very good plan to 
solder all joints. Cover the frame with 
bamboo paper and when dry apply two coats 
of "bamboo varnish."

Drill a hole through the motor base at the 
front to receive a piece of steel wire. Bend 
the wire to form two anchor hooks.

The propellers are each 8 inches in diameter. 
Each propeller is driven by a skein composed 
of 50 feet of 3/32 x 3/32 rubber.

The main plane is fastened temporarily to 
the motor base with rubber bands. Its normal 
position is about 17 inches from the tip of 
the machine, but its exact position will have 
to be determined by experiment. After it is 
formed, the plane should be fastened into 
position more securely.

The propellers must be of opposite pitch 
and wound in opposite directions. Each 
should receive from 500 to 600 turns. The 
model is launched by casting from the hand 
as though it were a spear.

FLYING THE MODELS.
``````````````````

A suitable winder of some sort is essential 
for winding up the strands of a model aeroplane.

A winder is most easily made from an egg 
beater of the dover pattern. The egg beater 
is dismantled and fitted up in the manner 
shown in the illustration. The blades are 
fitted with hooks which engage those on 
the end of the rubber skein.

.. figure:: images/Plate11.jpg
   :align: center
   :scale: 85 %
   :alt: Plate XI. Winding a model.
   
   Plate XI. Winding a model.

In order to wind a model remove the skeins 
from the anchor hooks and hook them on the 
winder. Have some one hold the machine at 
the rear end, slipping the fingers
around the propellers to keep them from 
untwisting. Stretch the skeins out to 
about twice their normal length and commence 
to wind. Gradually shorten the skein 
as the winding progresses until, at 
the time it is finished, it is down 
to its normal length.

.. figure:: images/Image56.jpg
   :align: center
   :scale: 85 %
   :alt: FIG. 56. A winder made from an egg beater.
   
   FIG. 56. A winder made from an egg beater.

In winding the machine be careful to do 
it in such a manner that the machine is not 
wrenched or twisted. Always count the number of 
turns given the winder so that there will be 
no danger of twisting them up too tightly 
and causing them to break.

The successful flying of a model aeroplane 
is an acquired knack just like swimming 
or bicycle riding. It is usually necessary 
to make several attempts before the model 
can be made to fly well. As soon as one gets 
acquainted with the vagaries of a model 
aeroplane it is a very easy matter to launch 
and adjust a machine.

The large page in the front of the book 
shows the right way of launching a model. 
The fingers are passed over the propellers 
and the frame grasped firmly, but gently. 
The tip of the machine should be raised and 
pointed slightly upward. Then give it a 
gentle slow push forward and release it. 
Always launch a machine into the wind, 
that is against it. The machine will fly 
forward, rise rapidly, turn completely 
around and race down the wind
for a thousand feet or more in the case of 
some of the larger machines described in 
this book when properly adjusted.

All the models described in this book with 
the exception of the first three must be 
flown out of doors because, when properly 
handled, they will travel upwards of one 
thousand feet.

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   Cut a circular hole the diameter of 
   
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   sufficient size to fit closely in the 
   
   envelope. The cardboard should 
   
   be no thicker than the coin. 

   Insert the coin in the hole and paste 
   
   a piece of paper on both sides of 
   
   the cardboard to prevent the coin 
   
   from falling out. 

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   WE HAVE THE LARGEST LINE OF

   TWENTY-FIVE CENT BOOKS

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   COLE &

   MORGAN

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   Publishers of the Arts and Sciences Series 

   187 N. 11th Street, NEWARK, N. J.

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   Wireless Telegraphy and Telephony

   Simply Explained

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   By ALFRED P. MORGAN

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   A NEW BOOK by the author of "Wireless Telegraph

   Construction for Amateurs."

This is undoubtedly one of the most complete 
and comprehensive treatises on the subject 
ever published, and a close study of its 
pages will enable one to master all the 
details of the wireless transmission of 
messages. The author has filled a 
long-felt want and has succeeded in 
furnishing a lucid, comprehensible 
explanation in simple language of 
the theory and practice of wireless 
telegraphy and telephony.

The book treats the subject from an entirely 
new standpoint. Several very novel and original 
ideas have been carried out in its making. 
It is well illustrated by over one hundred 
and fifty interesting photographs and drawings. 
All diagrams have been made in perspective showing 
the instruments as they actually appear in practice. 
The drawings are carefully keyed and labeled. 
Many of the photographs are accompanied by phantom 
drawings which reveal the name and purpose of each part.

It is a book which the wireless experimenter cannot 
afford to be without. It will prove even more 
valuable to the layman.

Among the contents are: Introductory. Wireless Transmission 
and reception. The ether. Electrical Oscillations. 
Electro-magnetic waves. The means for radiating and 
intercepting electric waves. Aerial Systems. Earth 
Connection. The Transmitting Apparatus. Current Supply. 
Spark Coils and Transformers. Condensers. Helixes. 
Spark Gaps. Anchor Gaps. Aerial Switches, Etc. The 
Receiving Apparatus. Detectors, etc. Tuning Coils 
and Loose Couplers. Variable Condensers. Tuning and 
Coupling. Directive Wave Telegraphy. The Dignity 
of Wireless. Its applications and service. Wireless 
in the army and navy. Wireless on an aeroplane. 
How a message is sent and received. The Wireless 
Telephone. The Ear. How we hear. Sound and Sound 
Waves. The Vocal Cords. The Structure of Speech. 
The Telephone Transmitter and Receiver. The 
Photophone. The Thermophone. The Selenium.

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   Handsomely bound in cloth with embossed cover

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   **Postpaid, $1.00**

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   **Build Your Own Wireless Instruments**

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   **Complete Up-to-the-Minute Authentic Practical**

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   WIRELESS TELEGRAPH 
   
   CONSTRUCTION FOR AMATEURS 

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   By ALFRED POWELL MORGAN 

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   3d EDITION 

   220 Pages 163 Illustrations 

   **Price**, $1.50, **Postpaid** 

   **Handsomely Bound in Silk Cloth**

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   :alt: Book Cover WIRELESS TELEGRAPH CONSTRUCTION FOR AMATEURS

Thoroughly up to date and unusually complete. Gives 
in minute detail, full directions for constructing wireless 
apparatus and various outfits capable of receiving from 
100 to 1,500 miles and transmitting 3 to 100 miles. Also 
clearly explains the purpose and action of each instrument. 
Directions for Operating and Adjusting, etc. 

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   **A SPLENDID TREATISE OF WIRELESS ALONG**
 
   **CONSTRUCTIVE LINES**

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   *Price*, $1.50, *Postpaid* 

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   **CONTENTS OF CHAPTERS**

\I.—Introduction. II.—The Apparatus. III.—Aerials and Earth Connections. IV.—Induction Coils. V.—Interrupters. VI.—Transformers. VII.—Oscillation Condensers and Leyden Jars. VIII.—Spark Gaps or Oscillators. IX.—Transmitting Helixes. X.—Keys. XI.—Aerial Switches and Anchor Gaps. XII.—Hot Wire Ammeter. XIII.—Oscillation Detectors. XIV.—Tuning Coils and Tuning Transformers. XV.—Receiving Condensers. XVI.—Telephone Receivers and Headbands. XVII.—Operation. XVIII.—The Amateur and the Wireless Law. How to Secure a License. Oscillation Helix. Quenched Spark Gap. Rotary Gaps. Kick-Back. The Variometer. New Crystal Detectors. The Audion.—Appendix. 

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   ENDORSED BY WIRELESS CLUBS THROUGHOUT THE COUNTRY AS BEING 

   THE MOST PRACTICAL BOOK PUBLISHED ON WIRELESS. 

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The value of this book has been greatly increased by the addition of much new subject matter and many illustrations of recent interest.

The new text explains fully how to build the most recent forms of Quenched Gaps, Rotary Gaps, Dough-Nut Tuners, Kick-back Preventers, Audion Detectors and numerous other instruments, accompanied by dimensioned working drawings. Several very interesting and instructive photographs have been included.

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**If you are interested in Wireless you need this book.**

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   THE AMATEUR'S WIRELESS HANDY BOOK

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   YOU CANNOT AFFORD TO 

   BE WITHOUT THIS BOOK 

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   Price 25 Cents, Postpaid    

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If you want to be an expert and an 
authority you must surround yourself 
with all available aids and helps. You 
have one of the best in the AMATEUR’S WIRELESS HANDY 
BOOK. 

It contains 36 pages of wireless calls, 
1500 in all. The list is complete and thoroughly 
revised to date and embodies all the wireless 
land stations in the world, the ships of the 
Merchant Marine, the U. S. Navy, the Revenue 
Service, etc. They are all there. All the 
calls are classified alphabetically. The 
list is the most reliable and complete in 
existence. All obsolete stations have been 
abolished. All corrections and changes have 
been made from the official lists.

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   **BUT, THAT IS NOT ALL.**

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Pages with spaces to fill in names, call letters, etc., make it possible to keep 
an accurate record of nearby amateur stations.

THE CODES, BOTH MORSE AND CONTINENTAL, are shown in the form of two 
large full-page charts printed in heavy black type so that they can be read from a 
distance. 

A BEGINNER’S SPEED CHART of both Codes so arranged that the codes may 
be quickly learned or consulted is provided. 

All the Abbreviations used so constantly by the wireless operator to 
save time and labor are included. There are a couple of pages of them.

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   **And last but not least**

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And last but not least Over 100 large hook-ups of wiring diagrams 
fully illustrated in a concise and clear manner. Loop and 
straightaway aerials, grounds, helixes, spark gaps, anchor gaps, 
leyden jars, induction coils, transformers, keys, aerial switches, 
tuning coils, loading coils, loose couplers, variometers, 
fixed condensers, silicon, electrolytic, carborundum, perikon 
and audion detectors, telephones, potentiometers, etc., 
you can find them all and how to connect. A hook-up for any 
set accompanied by full explanation. None are missing. They 
are all there. There are no two alike.

The most complete and reliable data ever collected. The result of thousands of 
experiments by some of the most famous wireless experts in the country. 

Read now before the supply is exhausted or you forget. You will be sorry if you 
don’t. 

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   **Price, 25 Cents, Postpaid**

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Note: This book is always kept up-to-date by frequently issuing new editions. 
Send for the latest copy. 

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   **The Operation of Wireless Telegraph Apparatus**

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Do your Wireless friends come to you for advice on 
constructing and operating their apparatus or do you go 
to them for information? 

Here is a chance for YOU to become the authority. 

**This book is a necessity to every Progressive Experimenter.** 

**It shows how to obtain the very highest efficiency from 
any station, and how to comply with the law. How 
to tune, adjust your detector, spark gap, phones, etc.**

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   Price, 25 Cents, Postpaid. 

This book was written for the wireless experimenter who 
has passed the amateur stage, but explains how the beginner also can 
obtain the very best results from his 
station. It contains much useful information to this end 
and many "kinks". 

**IT SHOWS HOW** to receive or send on long or short 
wave lengths with highest efficiency, to tune for longest 
distance reception of messages, to use the buzzer test, 
how to test and connect condensers, receivers, etc., 
how to use receiving transformers, variometers, etc., 
all with highest efficiency in view. 

**IT ALSO DESCRIBES** the construction and use of a simple, inexpensive wave 
meter to tune the station to any desired wave length, and tells how to obtain a 
sharp wave and a pure wave. 

**EXTRACTS FROM THE LAW** are also given in such a manner that they are 
easily understood. 

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   THE MODEL LIBRARY SERIES

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   **25c. BOOKS.**

**ELECTRICITY.**
    The study of, and its laws for beginners, comprising the laws of electric current generation and flow, Ohm's law, galvanism, magnetism, induction, principles of dynamos and motors, wiring, with explanations of simple mathematics as applied to electrical calculations. By N. H. SCHNEIDER. With 55 original illustrations and 6 tables.

**DRY BATTERIES.**
    A practical handbook on the designing, filling and finishing of dry batteries, with tables, for automobiles, gas engine, medical and coil work, electric bells, alarms, telephones, experiments and all purposes requiring a first-rate battery. Fully illustrated with 30 original drawings.

**ELECTRICAL CIRCUITS AND DIAGRAMS.**
    Being a selection of original up-to-date and practical diagrams for installing annunciators, alarms, bells, electric gas lighting, telephones, electric power light and wiring circuits, induction coils, gas engine igniters, dynamos and motors, armature windings. By N. H. SCHNEIDER.

**ELECTRIC BELLS AND ALARMS.**
    How to install them. By N. H. SCHNEIDER. Including batteries, wire and wiring, circuits, pushes, bells, burglar alarms, high and low water alarms, fire alarms, Thermostats, annunciators, and the locating and remedying of faults. With 56 original diagrams.

**MODERN PRIMARY BATTERIES.**
    Their construction, use and maintenance, including batteries for telephones, telegraphs, motors, electric lights, induction coils, and for all experimental work. By N. H. SCHNEIDER. 94 pages, 55 illustrations. The best and latest American book on the subject.

**EXPERIMENTING WITH INDUCTION COILS.**
    \H. S. NORRIE, author of "Induction Coils and Coil Making." A most instructive little book, full of practical and interesting experiments, fully explained in plain language with numerous hints and suggestions for evening entertainments. Arranged under the following headings: Introduction; The Handling of Ruhmkorff Coil; Experiments with Sparks; Effects in the Vacuum; Induction and Wireless Telegraphy. With 36 original illustrations. [In the press]
    
**SMALL ACCUMULATORS.**
    How made and used, by P. Marshall. Giving full descriptions how to make all the parts, assemble them, charge the cells and run them, with examples of their practical application. Useful receipts and memoranda and a glossary of technical terms. 80 pages, 40 illustrations, paper.

**ELECTRIC GAS LIGHTING.**
    How to install Electric gas igniting apparatus including the jump spark and multiple systems for all purposes. Also the care and selection of suitable batteries, wiring and repairs, by H. S. NORRIE. 101 pages, 57 illustrations, paper

**THE WIMSHURST MACHINE. HOW TO MAKE AND USE IT.**
    A practical handbook on the construction and working of Wimshurst machines, including radiography and wireless telegraphy and other static electrical apparatus. By A. W. Marshall. Second edition, revised and enlarged. Containing a number of sectional drawings and details to scale. Contents of chapters: 1. Introductory. 2. Static Electricity. 3. The electrophorus. 4. The Electroscope. 5. Condensers. 6. The Leyden Jar. 7. The Parts of a Wimshurst Machine and Their Use. 8. Making and Management of Wimshurst Machines. 9. Some Examples of Wimshurst Machines, small machines. 10. Complete detailed drawings and particulars for the construction of a 24-inch plate machine. 11. The Wimshurst machine for X-ray work with detailed drawings. 12. Experiments for Wimshurst machine. 112 pages, 30 illustrations and plates.

**WIRELESS TELEPHONE CONSTRUCTION.**
    By Newton Harrison. A comprehensive explanation of the making of a Wireless Telephone Equipment. Both the transmitting and receiving stations fully explained with details of construction sufficient to give an intelligent reader a good start in building a Wireless Telephone system and in operating it. 74 pages and 43 illustrations.

**LOW VOLTAGE ELECTRIC LIGHTING WITH THE STORAGE BATTERY.**
    Specially applicable to Country Houses, Farms, Small Settlements, Launches, Yachts, etc. By Norman H. Schneider. Giving full details and illustrations of the most up-to-date small American Plants. Contents of chapters. 1. Introduction. 2. The Storage Battery. 3. Estimating the Installation. 4. The Electric Plant. 5. Some Typical Plants. 6. Installation and Operation. 95 pages, 27 illustrations.

**PLANS AND SPECIFICATIONS FOR WIRELESS TELEGRAPH SETS, Part II**, 
    by A. F. Collins. Complete and detailed data for constructing a five to ten mile set, also a ten to twenty-five mile set. 1. A five to ten mile tuned transmitter. 2. A five to ten mile tuned coherer receptor. 3. A five to ten mile tuned auto-detector receptor. 4 and 5. A ten to twenty-five mile tuned transmitter. 6. A ten to twenty-five mile tuned coherer receptor. 7. A ten to twenty-five mile auto-detector receptor. 80 pages, 63 illustrations.

**PLANS AND SPECIFICATIONS FOR WIRELESS TELEGRAPH SETS, Part I**, 
    by A. Frederick Collins. Complete and detailed instructions for making an experimental set, also a one to five mile set. 1. An experimental transmitter. An experimental receptor. 3. A one to five mile transmitter. 4. A one to five miles coherer receptor. 5. A one to five mile auto-receptor. 55 pages, 37 illustrations.

**MODEL FLYING MACHINES, THEIR DESIGN AND CONSTRUCTION.**
    By W. G. Aston. Contents of chapters: 1. General principles and their application. 2. Power. 3. Supporting surfaces. 4. Screws, and how to make them. 5. Tails and elevators. 6. Fins. 7. Designs. With a number of examples of monoplane, bi-plane, tandem bi-plane and tri-plane models. 8. Dirigibles. 9. Helicopters. 10. Ornithopters. 11. Winding apparatus. 12. Compressed air motor. A first-rate book for Model Makers, 125 pages, 95 illustrations, 12mo. boards, postpaid, for 550.

**MODEL GLIDERS, BIRDS, BUTTERFLIES AND AEROPLANES.**
    How to Make and Fly Them. A booklet with one large sheet containing twelve butterflies and two birds in colors and material for making a small card-board Model Aeroplane Glider. Complete in folder, postpaid, for 55c.

**MODEL AEROPLANES, HOW TO BUILD AND FLY THEM.**
    By E. W. Twining. Consisting of one booklet and five large scaled drawings for three Twining Models, two of them being of the Bi-plane Glider type. Complete in folder, postpaid, for 55c.

**THE AEROPLANE PORTFOLIO.**
    By D. Ross Kennedy. Containing nine sheets of scale drawings of the following celebrated Aeroplanes: Bi-plane type-Wright, Farman, Voisin, Cody, Herring-Curtis. Monoplanes—Rep. Antoinette, Santos Dumont, and Bleriot. Each of these machines are here shown in End View, Plan and Elevation. Including booklet which contains a description of each machine. This timely set of drawings should prove of value to everyone interested in this important new industry. The complete set in folder, postpaid, for 55c.

**THE PERCY PIERCE FLYER.**
    A large scale drawing of this prize-winning Monoplane. With all measurements and details showing a front elevation, a side elevation and a top elevation; with 8-page descriptive booklet of particulars postpaid, 15c.

**HOW TO BUILD A 20-FT BIPLANE GLIDING MACHINE,**
    that will carry a man. By A. P. Morgan. A practical handbook on its construction and management. Enabling an intelligent reader to make his first step in the field of aviation with a comprehensive understanding of some of the principles involved. Fully illustrated with detailed drawings. Contents of chapters: 1. The frame work assembling and finishing the wood. 2. Covering the planes, laying out the fabric and fastening it. 3. Trussing, fastening the tie-rods and trueing the glider. 4. Gliding flight, the principles involved, instructions and precautions. 5. Remarks. 60 pages, 31 illustrations.

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   **ELECTRICIAN AND MECHANIC**

Is a magazine which will help you. It is a practical monthly for every one who wants to learn about electricity, or who uses tools. Its articles tell you how to make dynamos, engines, wireless telegraph apparatus, furniture, models, etc. It is the only magazine of its kind in the world.

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   EDITORS:

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   Frank Roy Frapie, M. Sc. Chem., F. R. P. S. 
   
   Prof. A. E. Watson, E. E., Ph. D. 
   
   \M. O. Sampson.

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   **CHARACTERISTIC FEATURES**

.. vspace:: 2

**Electricity.**
   Practical and simple articles on electrical science, new applications and history, all illustrated. How to make dynamos, motors, batteries, all kinds of electrical apparatus. How to wire for bells and electric lights, install telephones, etc.

**Mechanical Articles.**
    How to use lathes and machine tools. How to build gas engines, steam engines and other machines. All about gas engines and flying machines. Illustrated articles on everything new in mechanical progress.

**Woodworking and Manual Training.**
    How to build mission furniture. Wood finishing, staining, polishing, etc. Woodwork joints and cabinet making. How to make useful and handy articles of wood. Mechanical drawing, etc.

**Wireless Telegraphy and Telephony.**
    Full information of all that is new in wireless. Any one can build a wireless station from our descriptions. Our Wireless Club has over a thousand members in America and even beyond the seas. For seven years the wireless authority in the magazine line. 
    
**All articles written in simple language for everybody to read. $1.50 a year, 3 months' trial 25c.**

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   SPECIAL OFFER 
   
Until our stock of back numbers is exhausted, we offer six back numbers and a full year's subscription for $1.50. Money orders only; no stamps accepted. 

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   SAMPSON PUBLISHING COMPANY

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   161 Pope Building BOSTON, MASS. 
 
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   *When writing to advertisers, please mention this book.*
 
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   Materials for Building 

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   MODEL AEROPLANES 

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   will be found listed in our catalog of apparatus and supplies for

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   EXPERIMENTERS 
           
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   **WE ARE HEADQUARTERS for Rubber Strand, Bamboo Sticks**

   and all the rest of the things that you need

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   **WIRELESS TELEGRAPH APPARATUS**

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   We manufacture the largest line of RELIABLE wireless

   Apparatus in the country 
   
   Efficient Design Reasonable Cost Excellent Appearance 

   Skillful Workmanship and Unequalled Efficiency 
   
   are all yours when you buy AMCO Apparatus. 

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   OUR CATALOG 

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   Shows, Storage Cells, Step Down Transformers, Rectifiers, Induction Coils, 

   Wireless Instruments, Complete Transmitting and Receiving Outfits, Telephones, 
   
   Keys, Sounders, Flashlights, Lamps, Motors, Dynamos, Water Motors, Railways, 

   Model Aeroplanes, Books, Parts and Supplies. 

   **Send 4 cents in stamps to help cover cost of mailing and ask for a copy of our catalog.**

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   ADAMS - MORGAN CO.

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   **"The Experimenters Supply House"**
   
   **Box 72i Upper Montclair, N. J.**

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