Produced by James Simmons.

This file was produced from page images at Google Books.




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.




                         Model Flying Machines

                          HOW TO BUILD AND FLY

                                  THEM

                                   BY

                              A. P. MORGAN




                             NEWARK, N. J.

                             COLE & MORGAN

                                  1913




                            COPYRIGHT, 1913

                                   By

                             COLE & MORGAN




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.

[Illustration: PLATE I. Launching a Model Aeroplane.]




    INTRODUCTION. .....................................................
    CHAPTER I. GENERAL PRINCIPLES UNDERLYING AEROPLANE FLIGHT. ........
    CHAPTER II. GENERAL REMARKS REGARDING MODEL AEROPLANE CONSTRUCTION.
    THE QUESTION OF RESISTANCE. WEIGHT. STABILITY. ....................
    CHAPTER III. PLANES AND RUDDERS. ELEVATORS AND TAILS. .............
    CHAPTER IV. THE FUSELLAGE OR FRAMEWORK. ...........................
    CHAPTER V. MOTIVE POWER. ..........................................
    CHAPTER VI. SCREW PROPELLERS. .....................................
    CHAPTER VII. BEARINGS, THRUST BLOCKS AND GEARS. ...................
    CHAPTER VIII. BUILDING AND FLYING MODEL AEROPLANES. ...............
      The Blerioplane Flyer. (Plate II.) ..............................
      The Monoplane Flyer. (Plate III.) ...............................
      The Baby Racer. (Plate IV.) .....................................
      The Peerless Racer. (Plate V.) ..................................
      The Competition Flyer. (Plates VI and VII.) .....................
      The Long Distance Racer. (Plates VIII and IX.) ..................
      Fleming-Williams Flyer. (Plate X.) ..............................
      FLYING THE MODELS. ..............................................




    PLATE I. Launching a Model Aeroplane. .............................
    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. ................................................
    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.
    FIG 3. Diagram showing the makeup of a biplane (Wright). ..........
    FIG. 4. Two methods of controlling the lateral stability of an
    aeroplane. ........................................................
    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. ..........................
    FIG. 6. The disturbance caused by a triangular body moving through
    the atmosphere. ...................................................
    Plate II. .........................................................
    FIG. 7. Showing the disturbance created by a small spar on the back
    of a plane. .......................................................
    FIG. 8. Diagram illustrating the ichthyoid shape and how smoothly it
    slips through the air without creating an eddy. ...................
    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. .......................................................
    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. ...............
    FIG. 11. Flat and dihedral planes. ................................
    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. ...
    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. ....................
    PLATE III. ........................................................
    FIG. 14. How ribs may be joined to the long members. ..............
    FIG. 15. Form for bending the planes. .............................
    FIG. 16. A good method of building a wooden plane. ................
    FIG. 17. Various shapes a plane may take. .........................
    FIG. 18. An edgewise view of several planes showing the different
    ways they may be bent to secure stability. ........................
    FIG. 19. The various ways two planes may be combined to secure
    stability or form a biplane. ......................................
    FIG. 20. Fins. ....................................................
    FIG. 21. A simple "motor base" or fusellage. ......................
    FIG. 22. Paper Tube Fusellage. Part of the tube is cutaway to show
    the rubber skein inside. ..........................................
    FIG. 23. Two methods of gearing a propeller. ......................
    FIG. 24. ..........................................................
    FIG. 25. ..........................................................
    FIG. 26. Method of laying out a screw propeller, that is,
    determining the angle of the blades at different points. ..........
    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. .....................................
    FIG. 28. Templets for testing and carving a propeller. ............
    FIG. 29. A simple method of forming a propeller from sheet metal. .
    FIG. 30. A built-up metal propeller made of aluminum. .............
    FIG. 31. Metal Propeller. .........................................
    FIG. 32. Method of carving a propeller of the truly helical type. .
    FIG. 33. Methods of fastening propellers to shaft. ................
    FIG. 34. Method of forming sockets for joining struts, etc., by
    cutting from sheet metal. .........................................
    FIG. 35. Bent wood propellers and the methods of fastening them to
    the shaft. ........................................................
    FIG. 36. Propeller blank (top). Carved propeller (bottom). ........
    FIG. 37. Langley type propeller (top). Wright type propeller
    (bottom). .........................................................
    FIG. 38. Quasi-helical propeller. .................................
    FIG. 39. Blanks for racing (top) and chauviere (bottom) propellers.
    FIG. 40. The first step in carving a propeller. The blank. Hollowing
    the first blade. ..................................................
    FIG. 41. One blade hollowed. Hollowing the second blade. ..........
    FIG. 42 Rounding the back of the first blade. Rounding the back of
    the second blade. .................................................
    FIG. 43. All carving finished. Sandpapering to secure a smooth
    surface. ..........................................................
    FIG. 44. Varnishing. The propeller finished. ......................
    FIG. 45. Accentricity. The effect of placing the center of gravity
    too low. ..........................................................
    FIG. 46. Simplest method of fitting two propellers to a model
    aeroplane. ........................................................
    FIG. 47. A method of arranging two propellers on the same axis. ...
    FIG. 48. Simple bearings. .........................................
    FIG. 49. Double bearings. .........................................
    FIG. 50. Simple thrust bearing. ...................................
    FIG. 51. Ball thrust bearing. .....................................
    FIG. 52. Hooks. ...................................................
    Plate IV. .........................................................
    Plate V. ..........................................................
    Plate VI. .........................................................
    FIG. 53. Method of holding plane to frame with rubber bands. ......
    Plate VII. ........................................................
    FIG. 54. The Peerless Racer. ......................................
    Plate VIII. .......................................................
    Plate IX. .........................................................
    Plate X. ..........................................................
    FIG. 55. Racing blank and propeller. ..............................
    Plate XI. Winding a model. ........................................
    FIG. 56. A winder made from an egg beater. ........................




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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.]

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.)

[Illustration: 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.

[Illustration: FIG. 35. Bent wood propellers and the methods of
fastening them to the shaft.]

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: FIG. 40. The first step in carving a propeller. The
blank. Hollowing the first blade.]

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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.

[Illustration: 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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save time and labor are included. There are a couple of pages of them.


                        *And last but not least*


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.


                      *Price, 25 Cents, Postpaid*


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




            *The Operation of Wireless Telegraph Apparatus*

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.*

                       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.




                        THE MODEL LIBRARY SERIES

                             *25c. BOOKS.*

*ELECTRICITY.*
       The study of, and its laws for beginners, comprising the laws of
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       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
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*ELECTRICAL CIRCUITS AND DIAGRAMS.*
       Being a selection of original up-to-date and practical diagrams
       for installing annunciators, alarms, bells, electric gas
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       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,
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       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
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*EXPERIMENTING WITH INDUCTION COILS.*
       H. S. NORRIE, author of "Induction Coils and Coil Making." A most
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       and Wireless Telegraphy. With 36 original illustrations. [In the
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*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
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*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.
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       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
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       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
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       bi-plane and tri-plane models. 8. Dirigibles. 9. Helicopters. 10.
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*MODEL GLIDERS, BIRDS, BUTTERFLIES AND AEROPLANES.*
       How to Make and Fly Them. A booklet with one large sheet
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*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
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*THE AEROPLANE PORTFOLIO.*
       By D. Ross Kennedy. Containing nine sheets of scale drawings of
       the following celebrated Aeroplanes: Bi-plane type-Wright,
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*THE PERCY PIERCE FLYER.*
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*HOW TO BUILD A 20-FT BIPLANE GLIDING MACHINE,*
       that will carry a man. By A. P. Morgan. A practical handbook on
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       the principles involved, instructions and precautions. 5.
       Remarks. 60 pages, 31 illustrations.




                       *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.


                                EDITORS:

              Frank Roy Frapie, M. Sc. Chem., F. R. P. S.

                   Prof. A. E. Watson, E. E., Ph. D.

                             M. O. Sampson.


                       *CHARACTERISTIC FEATURES*


*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.*


                             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.


                       SAMPSON PUBLISHING COMPANY

                    161 Pope Building BOSTON, MASS.

        _When writing to advertisers, please mention this book._




                         Materials for Building

                            MODEL AEROPLANES

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

                             EXPERIMENTERS

         *WE ARE HEADQUARTERS for Rubber Strand, Bamboo Sticks*

              and all the rest of the things that you need

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