Construction and Operation
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Unknown >> Construction and Operation
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Some Practical Uses.
At the same time there are fields in which the flying
machine may be used to great advantage. These are:
Sports--Flying machine races or flights will always
be popular by reason of the element of danger. It is
a strange, but nevertheless a true proposition, that it is
this element which adds zest to all sporting events.
Scientific--For exploration of otherwise inaccessible
regions such as deserts, mountain tops, etc.
Reconnoitering--In time of war flying machines may
be used to advantage to spy out an enemy's encampment,
ascertain its defenses, etc.
CHAPTER III.
MECHANICAL BIRD ACTION
In order to understand the theory of the modern flying
machine one must also understand bird action and wind
action. In this connection the following simple experiment
will be of interest:
Take a circular-shaped bit of cardboard, like the lid of
a hat box, and remove the bent-over portion so as to
have a perfectly flat surface with a clean, sharp edge.
Holding the cardboard at arm's length, withdraw your
hand, leaving the cardboard without support. What is
the result? The cardboard, being heavier than air, and
having nothing to sustain it, will fall to the ground.
Pick it up and throw it, with considerable force, against
the wind edgewise. What happens? Instead of falling
to the ground, the cardboard sails along on the wind,
remaining afloat so long as it is in motion. It seeks
the ground, by gravity, only as the motion ceases, and
then by easy stages, instead of dropping abruptly as in
the first instance.
Here we have a homely, but accurate illustration of
the action of the flying machine. The motor does for
the latter what the force of your arm does for the cardboard--
imparts a motion which keeps it afloat. The
only real difference is that the motion given by the
motor is continuous and much more powerful than that
given by your arm. The action of the latter is limited
and the end of its propulsive force is reached within a
second or two after it is exerted, while the action of the
motor is prolonged.
Another Simple Illustration.
Another simple means of illustrating the principle of
flying machine operation, so far as sustentation and the
elevation and depression of the planes is concerned, is
explained in the accompanying diagram.
A is a piece of cardboard about 2 by 3 inches in size.
B is a piece of paper of the same size pasted to one edge
of A. If you bend the paper to a curve, with convex
side up and blow across it as shown in Figure C, the
paper will rise instead of being depressed. The dotted
lines show that the air is passing over the top of the
curved paper and yet, no matter how hard you may
blow, the effect will be to elevate the paper, despite the
fact that the air is passing over, instead of under the
curved surface.
In Figure D we have an opposite effect. Here the
paper is in a curve exactly the reverse of that shown in
Figure C, bringing the concave side up. Now if you
will again blow across the surface of the card the action
of the paper will be downward--it will be impossible to
make it rise. The harder you blow the greater will be
the downward movement.
Principle In General Use.
This principle is taken advantage of in the construction
of all successful flying machines. Makers of monoplanes
and biplanes alike adhere to curved bodies, with
the concave surface facing downward. Straight planes
were tried for a time, but found greatly lacking in the
power of sustentation. By curving the planes, and placing
the concave surface downward, a sort of inverted bowl
is formed in which the air gathers and exerts a buoyant
effect. Just what the ratio of the curve should be is a
matter of contention. In some instances one inch to the
foot is found to be satisfactory; in others this is doubled,
and there are a few cases in which a curve of as much as
3 inches to the foot has been used.
Right here it might be well to explain that the word
"plane" applied to flying machines of modern construction
is in reality a misnomer. Plane indicates a flat,
level surface. As most successful flying machines have
curved supporting surfaces it is clearly wrong to speak
of "planes," or "aeroplanes." Usage, however, has made
the terms convenient and, as they are generally accepted
and understood by the public, they are used in like manner
in this volume.
Getting Under Headway.
A bird, on first rising from the ground, or beginning
its flight from a tree, will flap its wings to get under
headway. Here again we have another illustration of
the manner in which a flying machine gets under headway--
the motor imparts the force necessary to put the
machine into the air, but right here the similarity ceases.
If the machine is to be kept afloat the motor must be
kept moving. A flying machine will not sustain itself;
it will not remain suspended in the air unless it is
under headway. This is because it is heavier than air,
and gravity draws it to the ground.
Puzzle in Bird Soaring.
But a bird, which is also heavier than air, will remain
suspended, in a calm, will even soar and move in a
circle, without apparent movement of its wings. This
is explained on the theory that there are generally vertical
columns of air in circulation strong enough to sustain
a bird, but much too weak to exert any lifting power
on a flying machine, It is easy to understand how a
bird can remain suspended when the wind is in action,
but its suspension in a seeming dead calm was a puzzle
to scientists until Mr. Chanute advanced the proposition
of vertical columns of air.
Modeled Closely After Birds.
So far as possible, builders of flying machines have
taken what may be called "the architecture" of birds as
a model. This is readily noticeable in the form of
construction. When a bird is in motion its wings (except
when flapping) are extended in a straight line at right
angles to its body. This brings a sharp, thin edge
against the air, offering the least possible surface for
resistance, while at the same time a broad surface for
support is afforded by the flat, under side of the wings.
Identically the same thing is done in the construction of
the flying machine.
Note, for instance, the marked similarity in form as
shown in the illustration in Chapter II. Here A is the
bird, and B the general outline of the machine. The
thin edge of the plane in the latter is almost a duplicate
of that formed by the outstretched wings of the bird,
while the rudder plane in the rear serves the same purpose
as the bird's tail.
CHAPTER IV.
VARIOUS FORMS OF FLYING MACHINES.
There are three distinct and radically different forms
of flying machines. These are:
Aeroplanes, helicopters and ornithopers.
Of these the aeroplane takes precedence and is used
almost exclusively by successful aviators, the helicopters
and ornithopers having been tried and found lacking in
some vital features, while at the same time in some
respects the helicopter has advantages not found in the
aeroplane.
What the Helicopter Is.
The helicopter gets its name from being fitted with
vertical propellers or helices (see illustration) by the
action of which the machine is raised directly from the
ground into the air. This does away with the necessity
for getting the machine under a gliding headway before
it floats, as is the case with the aeroplane, and consequently
the helicopter can be handled in a much smaller
space than is required for an aeroplane. This, in many
instances, is an important advantage, but it is the only
one the helicopter possesses, and is more than overcome
by its drawbacks. The most serious of these is that the
helicopter is deficient in sustaining capacity, and requires
too much motive power.
Form of the Ornithopter.
The ornithopter has hinged planes which work like
the wings of a bird. At first thought this would seem
to be the correct principle, and most of the early experimenters
conducted their operations on this line. It
is now generally understood, however, that the bird in
soaring is in reality an aeroplane, its extended wings
serving to sustain, as well as propel, the body. At any
rate the ornithoper has not been successful in aviation,
and has been interesting mainly as an ingenious toy.
Attempts to construct it on a scale that would permit
of its use by man in actual aerial flights have been far
from encouraging.
Three Kinds of Aeroplanes.
There are three forms of aeroplanes, with all of which
more or less success has been attained. These are:
The monoplane, a one-surfaced plane, like that used
by Bleriot.
The biplane, a two-surfaced plane, now used by the
Wrights, Curtiss, Farman, and others.
The triplane, a three-surfaced plane This form is
but little used, its only prominent advocate at present
being Elle Lavimer, a Danish experimenter, who has not
thus far accomplished much.
Whatever of real success has been accomplished in
aviation may be credited to the monoplane and biplane,
with the balance in favor of the latter. The monoplane
is the more simple in construction and, where weight-
sustaining capacity is not a prime requisite, may
probably be found the most convenient. This opinion is
based on the fact that the smaller the surface of the
plane the less will be the resistance offered to the air,
and the greater will be the speed at which the machine
may be moved. On the other hand, the biplane has a
much greater plane surface (double that of a monoplane
of the same size) and consequently much greater weight-
carrying capacity.
Differences in Biplanes.
While all biplanes are of the same general construction
so far as the main planes are concerned, each aviator
has his own ideas as to the "rigging."
Wright, for instance, places a double horizontal rudder
in front, with a vertical rudder in the rear. There
are no partitions between the main planes, and the
bicycle wheels used on other forms are replaced by skids.
Voisin, on the contrary, divides the main planes with
vertical partitions to increase stability in turning; uses
a single-plane horizontal rudder in front, and a big box-
tail with vertical rudder at the rear; also the bicycle
wheels.
Curtiss attaches horizontal stabilizing surfaces to the
upper plane; has a double horizontal rudder in front,
with a vertical rudder and horizontal stabilizing surfaces
in rear. Also the bicycle wheel alighting gear.
CHAPTER V.
CONSTRUCTING A GLIDING MACHINE.
First decide upon the kind of a machine you want--
monoplane, biplane, or triplane. For a novice the biplane
will, as a rule, be found the most satisfactory as
it is more compact and therefore the more easily handled.
This will be easily understood when we realize that the
surface of a flying machine should be laid out in proportion
to the amount of weight it will have to sustain.
The generally accepted rule is that 152 square feet of
surface will sustain the weight of an average-sized man,
say 170 pounds. Now it follows that if these 152 square
feet of surface are used in one plane, as in the monoplane,
the length and width of this plane must be greater
than if the same amount of surface is secured by using
two planes--the biplane. This results in the biplane
being more compact and therefore more readily manipulated
than the monoplane, which is an important item
for a novice.
Glider the Basis of Success.
Flying machines without motors are called gliders. In
making a flying machine you first construct the glider.
If you use it in this form it remains a glider. If you
install a motor it becomes a flying machine. You must
have a good glider as the basis of a successful flying
machine.
It will be well for the novice, the man who has never
had any experience as an aviator, to begin with a glider
and master its construction and operation before he
essays the more pretentious task of handling a fully-
equipped flying machine. In fact, it is essential that he
should do so.
Plans for Handy Glider.
A glider with a spread (advancing edge) of 20 feet, and
a breadth or depth of 4 feet, will be about right to begin
with. Two planes of this size will give the 152 square
yards of surface necessary to sustain a man's weight.
Remember that in referring to flying machine measurements
"spread" takes the place of what would ordinarily
be called "length," and invariably applies to the long
or advancing edge of the machine which cuts into the air.
Thus, a glider is spoken of as being 20 feet spread, and
4 feet in depth. So far as mastering the control of the
machine is concerned, learning to balance one's self in
the air, guiding the machine in any desired direction by
changing the position of the body, etc., all this may be
learned just as readily, and perhaps more so, with a 20-
foot glider than with a larger apparatus.
Kind of Material Required.
There are three all-important features in flying machine
construction, viz.: lightness, strength and extreme
rigidity. Spruce is the wood generally used for glider
frames. Oak, ash and hickory are all stronger, but they
are also considerably heavier, and where the saving of
weight is essential, the difference is largely in favor of
spruce. This will be seen in the following table:
Weight Tensile Compressive
per cubic ft. Strength Strength
Wood in lbs. lbs. per sq. in. lbs. per sq in.
Hickory 53 12,000 8,500
Oak 50 12,000 9,000
Ash 38 12,000 6,000
Walnut 38 8,000 6,000
Spruce 25 8,000 5,000
Pine 25 5,000 4,500
Considering the marked saving in weight spruce has
a greater percentage of tensile strength than any of the
other woods. It is also easier to find in long, straight-
grained pieces free from knots, and it is this kind only
that should be used in flying machine construction.
You will next need some spools or hanks of No. 6
linen shoe thread, metal sockets, a supply of strong
piano wire, a quantity of closely-woven silk or cotton
cloth, glue, turnbuckles, varnish, etc.
Names of the Various Parts.
The long strips, four in number, which form the front
and rear edges of the upper and lower frames, are called
the horizontal beams. These are each 20 feet in length.
These horizontal beams are connected by upright strips,
4 feet long, called stanchions. There are usually 12 of
these, six on the front edge, and six on the rear. They
serve to hold the upper plane away from the lower one.
Next comes the ribs. These are 4 feet in length (projecting
for a foot over the rear beam), and while intended
principally as a support to the cloth covering of
the planes, also tend to hold the frame together in a
horizontal position just as the stanchions do in the vertical.
There are forty-one of these ribs, twenty-one on
the upper and twenty on the lower plane. Then come
the struts, the main pieces which join the horizontal
beams. All of these parts are shown in the illustrations,
reference to which will make the meaning of the
various names clear.
Quantity and Cost of Material.
For the horizontal beams four pieces of spruce, 20 feet
long, 1 1/2 inches wide and 3/4 inch thick are necessary.
These pieces must be straight-grain, and absolutely free
from knots. If it is impossible to obtain clear pieces
of this length, shorter ones may be spliced, but this is
not advised as it adds materially to the weight. The
twelve stanchions should be 4 feet long and 7/8 inch in
diameter and rounded in form so as to offer as little
resistance as possible to the wind. The struts, there
are twelve of them, are 3 feet long by 11/4 x 1/2 inch. For
a 20-foot biplane about 20 yards of stout silk or unbleached
muslin, of standard one yard width, will be
needed. The forty-one ribs are each 4 feet long, and
1/2 inch square. A roll of No. 12 piano wire, twenty-four
sockets, a package of small copper tacks, a pot of glue,
and similar accessories will be required. The entire
cost of this material should not exceed $20. The wood
and cloth will be the two largest items, and these should
not cost more than $10. This leaves $10 for the varnish,
wire, tacks, glue, and other incidentals. This estimate
is made for cost of materials only, it being taken for
granted that the experimenter will construct his own
glider. Should the services of a carpenter be required
the total cost will probably approximate $60 or $70.
Application of the Rudders.
The figures given also include the expense of rudders,
but the details of these have not been included as the
glider is really complete without them. Some of the best
flights the writer ever saw were made by Mr. A. M. Herring in a
glider without a rudder, and yet there can
be no doubt that a rudder, properly proportioned and
placed, especially a rear rudder, is of great value to the
aviator as it keeps the machine with its head to the
wind, which is the only safe position for a novice. For
initial educational purposes, however, a rudder is not
essential as the glides will, or should, be made on level
ground, in moderate, steady wind currents, and at a
modest elevation. The addition of a rudder, therefore,
may well be left until the aviator has become reasonably
expert in the management of his machine.
Putting the Machine Together.
Having obtained the necessary material, the first move
is to have the rib pieces steamed and curved. This curve
may be slight, about 2 inches for the 4 feet. While
this is being done the other parts should be carefully
rounded so the square edges will be taken off. This
may be done with sand paper. Next apply a coat of
shellac, and when dry rub it down thoroughly with fine
sand paper. When the ribs are curved treat them in
the same way.
Lay two of the long horizontal frame pieces on the
floor 3 feet apart. Between these place six of the strut
pieces. Put one at each end, and each 4 1/2 feet put
another, leaving a 2-foot space in the center. This will
give you four struts 4 1/2 feet apart, and two in the center
2 feet apart, as shown in the illustration. This makes
five rectangles. Be sure that the points of contact are
perfect, and that the struts are exactly at right angles
with the horizontal frames. This is a most important
feature because if your frame "skews" or twists you
cannot keep it straight in the air. Now glue the ends
of the struts to the frame pieces, using plenty of glue,
and nail on strips that will hold the frame in place while
the glue is drying. The next day lash the joints together
firmly with the shoe thread, winding it as you would to
mend a broken gun stock, and over each layer put a
coating of glue. This done, the other frame pieces and
struts may be treated in the same way, and you will thus
get the foundations for the two planes.
Another Way of Placing Struts.
In the machines built for professional use a stronger
and more certain form of construction is desired. This
is secured by the placing the struts for the lower plane
under the frame piece, and those for the upper plane
over it, allowing them in each instance to come out flush
with the outer edges of the frame pieces. They are then
securely fastened with a tie plate or clamp which passes
over the end of the strut and is bound firmly against
the surface of the frame piece by the eye bolts of the
stanchion sockets.
Placing the Rib Pieces.
Take one of the frames and place on it the ribs, with
the arched side up, letting one end of the ribs come
flush with the front edge of the forward frame, and the
other end projecting about a foot beyond the rear frame.
The manner of fastening the ribs to the frame pieces is
optional. In some cases they are lashed with shoe
thread, and in others clamped with a metal clamp fastened
with 1/2-inch wood screws. Where clamps and
screws are used care should be taken to make slight
holes in the wood with an awl before starting the screws
so as to lessen any tendency to split the wood. On the
top frame, twenty-one ribs placed one foot apart will be
required. On the lower frame, because of the opening
left for the operator's body, you will need only twenty.
Joining the Two Frames.
The two frames must now be joined together. For this
you will need twenty-four aluminum or iron sockets
which may be purchased at a foundry or hardware shop.
These sockets, as the name implies, provide a receptacle
in which the end of a stanchion is firmly held, and have
flanges with holes for eye-bolts which hold them firmly
to the frame pieces, and also serve to hold the guy wires.
In addition to these eye-bolt holes there are two others
through which screws are fastened into the frame pieces.
On the front frame piece of the bottom plane place six
sockets, beginning at the end of the frame, and locating
them exactly opposite the struts. Screw the sockets into
position with wood screws, and then put the eye-bolts in
place. Repeat the operation on the rear frame. Next
put the sockets for the upper plane frame in place.
You are now ready to bring the two planes together.
Begin by inserting the stanchions in the sockets in the
lower plane. The ends may need a little rubbing with
sandpaper to get them into the sockets, but care must
be taken to have them fit snugly. When all the stanchions
are in place on the lower plane, lift the upper
plane into position, and fit the sockets over the upper
ends of the stanchions.
Trussing with Guy Wires.
The next move is to "tie" the frame together rigidly
by the aid of guy wires. This is where the No. 12 piano
wire comes in. Each rectangle formed by the struts and
stanchions with the exception of the small center one,
is to be wired separately as shown in the illustration.
At each of the eight corners forming the rectangle the
ring of one of the eye-bolts will be found. There are
two ways of doing this "tieing," or trussing. One is to
run the wires diagonally from eye-bolt to eye-bolt, depending
upon main strength to pull them taut enough,
and then twist the ends so as to hold. The other is to
first make a loop of wire at each eye-bolt, and connect
these loops to the main wires with turn-buckles. This
latter method is the best, as it admits of the tension being
regulated by simply turning the buckle so as to draw
the ends of the wire closer together. A glance at the
illustration will make this plain, and also show how the
wires are to be placed. The proper degree of tension
may be determined in the following manner:
After the frame is wired place each end on a saw-horse
so as to lift the entire frame clear of the work-shop
floor. Get under it, in the center rectangle and, grasping
the center struts, one in each hand, put your entire
weight on the structure. If it is properly put together
it will remain rigid and unyielding. Should it sag ever
so slightly the tension of the wires must be increased
until any tendency to sag, no matter how slight it may
be, is overcome.
Putting on the Cloth.
We are now ready to put on the cloth covering which
holds the air and makes the machine buoyant. The kind
of material employed is of small account so long as it is
light, strong, and wind-proof, or nearly so. Some aviators
use what is called rubberized silk, others prefer
balloon cloth. Ordinary muslin of good quality, treated
with a coat of light varnish after it is in place, will answer
all the purposes of the amateur.
Cut the cloth into strips a little over 4 feet in length.
As you have 20 feet in width to cover, and the cloth is
one yard wide, you will need seven strips for each plane,
so as to allow for laps, etc. This will give you fourteen
strips. Glue the end of each strip around the front
horizontal beams of the planes, and draw each strip back,
over the ribs, tacking the edges to the ribs as you go
along, with small copper or brass tacks. In doing this
keep the cloth smooth and stretched tight. Tacks should
also be used in addition to the glue, to hold the cloth to
the horizontal beams.
Next, give the cloth a coat of varnish on the clear, or
upper side, and when this is dry your glider will be
ready for use.
Reinforcing the Cloth.
While not absolutely necessary for amateur purposes,
reinforcement of the cloth, so as to avoid any tendency
to split or tear out from wind-pressure, is desirable. One
way of doing this is to tack narrow strips of some
heavier material, like felt, over the cloth where it laps
on the ribs. Another is to sew slips or pockets in the
cloth itself and let the ribs run through them. Still another
method is to sew 2-inch strips (of the same material
as the cover) on the cloth, placing them about one
yard apart, but having them come in the center of each
piece of covering, and not on the laps where the various
pieces are joined.
Use of Armpieces.
Should armpieces be desired, aside from those afforded
by the center struts, take two pieces of spruce, 3 feet
long, by 1 x 1 3/4 inches, and bolt them to the front and
rear beams of the lower plane about 14 inches apart.
These will be more comfortable than using the struts,
as the operator will not have to spread his arms so
much. In using the struts the operator, as a rule, takes
hold of them with his hands, while with the armpieces,
as the name implies, he places his arms over them, one
of the strips coming under each armpit.
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