A model glider, or aeroplane without a motor, will be found perhaps as
entertaining a toy as the power-driven machine. It is much simpler, of
course, to build and adjust a successful glider even than the most
elementary model aeroplane. With the problem of the motor and propeller
removed, the cost of construction besides is reduced to practically
nothing. Here is excellent entertainment for those who have not the time
or patience for model building. A graceful glide of successive waving
lines makes a beautiful spectacle. Incidentally it is a good plan to
work out the designs of large models in this way.
Fascinating little paper models, reproducing the famous man-carrying
machines, the Wright, Bleriot, and others, may be put together in a few
minutes. With a little adjustment, they may be made to fly from fifty to
one hundred times their length. A paper Bleriot biplane six inches in
length, for instance, may be made to sail for from twenty-five to fifty
feet, and so on. This will be the actual horizontal distance traversed;
the actual distance measured in long, undulating curves may be
considerably more. Such flights do not consist merely of a long diagonal
to earth, but of several surprising upward sweeps, well worth the
trouble of construction. It is interesting to note the remarkable
stability of their gliders.
[Illustration: A Simple Model Glider]
An hour’s entertainment, no less interesting than instructive, may be
enjoyed with a series of these paper gliders. A different model might be
prepared for each guest, and a prize or favor offered for the longest or
best spectacular flight. The little gliders will cross a large room
before coming down. The various aeroplanes nowadays are so familiar that
in any gathering will be found several who favor, for instance, a Wright
over a Curtiss take a lively interest in the rivalry of the various
models.
[Illustration: An effective glider built by R.S. Barnaby]
[Illustration: An efficient sling-shot glider built by John Roche]
Begin with a very simple model. You will soon learn the trick of judging
the size of the supporting surfaces and the spacing. The Antoinette
aeroplane is probably the easiest one to imitate. From a sheet of
ordinary writing paper, cardboard or fine wood, cut the form indicated.
If the paper be rather heavy, it may be made six inches in length. By
folding the paper and making one cutting, it will be found much easier
to make the wings even and symmetrical.
The two sides should be fixed at a broad dihedral angle. To keep the
little glider on an even keel you will need to add a weight to the
front. A large pin or paper clip will answer. Launch the glider by
holding it horizontally and throwing slightly forward. If it darts
downward, lighten the ballast. If it falls backward, "sitting on its
tail," add more weight at the front or bend the tail up.
Your glider will, of course, travel to the ground along the line of
least resistance, and the trick is to adjust the center of gravity and
center of pressure that this descent may be as gradual as possible. The
center of gravity should come a little in front of the center of
pressure. The gliding angle, as it is called, or the angle between the
course of the model in flight with the ground should be about one in
twelve. In other words, the glider descends one foot for every twelve
feet it travels forward. Practically all the famous monoplanes may be
reproduced in this way.
A variety of gliders may be made in a general arrow form. These arrows,
or darts, as they are called, may be made about a foot in length and
three or four inches in width. The horizontal surface, it should be
borne in mind, is the supporting surface, while the vertical surface
gives the flight direction. These gliders will also require weighting at
the forward end. They should be thrown forward with rather more force
than in the case of the Antoinette.
The biplanes such as the Wright and Curtiss aeroplanes may be reproduced
very easily in paper. They fly best when made about six inches in
length. Cut the two sheets of paper for the main planes one inch by six
inches and round off the corners on one side. Two similar sheets, one by
three inches, will be required for the smaller plane in the rear.
The planes are held in position by a series of paper struts, or
toothpicks, and should be separated by a distance equal to their width,
in this case one inch. Cut the slips of paper to form the struts one and
one-half inches in length and bend over the corners at right angles,
one-quarter of an inch from either end. These should be pasted in
position, always keeping the edge of the struts lengthwise so that they
will offer the least resistance in flight.
Connect the two biplanes by strips of paper six inches in length pasted
on the lower planes or main deck of the little aeroplane. The forward
planes should be fixed at a slightly elevated angle by running struts
from the connecting strips to the upper plane. The accompanying picture
will show how simple this all is.
The biplanes as a rule require no weighing. To launch them, hold them
high in the air and merely let go. They fly best with their smaller
planes forward. By varying the angle of the front plane, you can soon
bring it to an even keel. A vertical rudder placed three inches behind
the main plane will increase the model’s directional stability.
An amazingly clever little glider may be made of a piece of reed or
cane, say five inches in length, and a sheet of writing paper. With a
pair of scissors cut two planes, one three by one inch and the second
two by half an inch. You will also need a vertical rudder one inch
square. Round off the corners slightly and glue the planes at either end
of the stick and exactly on a level. Now fasten the rudder at right
angles to the planes beneath the larger plane. If it dips, the front
plane is too far back, while if it rises too quickly and settles back,
the front plane must be brought back.
The paper gliders form an excellent kindergarten preparation to the
study of aviation, leading up to the construction of large model
gliders. You will thus gain a skill in adjusting the planes and fixing
the centers of gravity and of pressure, which will prove valuable later
on. The possibilities of glider building come as a surprise to the
laymen in such matters.
THE SLING-SHOT GLIDER.
A fascinating field of experiment is opened by combining the sling-shot
principle with the ordinary glider. The speed with which one can launch
a glider from the hand is, of course, limited. Now use a small strand of
rubber to launch the planes, and the increased speed will not only
lengthen the flight surprisingly but make possible a really remarkable
spectacular flight. A small glider may be made to return to the starting
point or even loop the loop two or three times before touching the
ground. By a simple adjustment of the planes, these curves may be varied
indefinitely.
[Illustration: Designs for Sling-Shot Gliders.]
When you have adjusted your glider to fly well, try the same arrangement
of planes on a piece of reed, say eight inches in length, and bend the
end over in the form of a hook. By heating the cane over a flame, you
can make it turn without breaking and hold its position. Now loop a
single rubber band over your thumb and forefinger, and passing the hook
over the rubber, pull back exactly as you would use a sling shot. As you
release the glider, pull your other hand quickly out of range. By using
a heavier paper, one which will hold its shape, and turning the forward
edges up slightly, the glider may be made to travel upward in a variety
of graceful curves.
[Illustration: Paper Gliders. Antoinette Monoplane and Wright Biplane]
[Illustration: An excellent glider with wooden planes]
[Illustration: A covered-frame sling-shot glider]
The best glider for launching on the sling-shot principle is made from
planes cut from thin metal sheets. Aluminum is the best material, but a
very thin wood will answer. A one-foot model glider will be found the
easiest size to manage. Cut one plane eight inches in length by three in
width, and the second five inches by two inches. Round off the corners
on one side of each plane, leaving a straight line for the front or
entering edge.
Mount the planes on a strip of reed, cane or bamboo about eighteen
inches in length. In all these gliders the forward plane is made the
smaller, thereby reducing the head resistance as far as possible. The
metal planes should be slightly flexed by bending them to a slight
concave above the horizontal and just back of the front edge. The
forward end of the stick should be bent into a large hook by heating or
first soaking in water. If your glider falls quickly to the ground bend
the frame a trifle upward.
Since your glider is intended to travel at a comparatively high speed,
the planes may be mounted much further apart than in the case of a
glider launched from the hand. Try them first ten inches apart and
afterwards adjust them to suit. The rubber used for launching the glider
should be fairly heavy, say three strands of one-eighth inch rubber or
its equivalent. The end of the hook may need adjusting so that it will
escape from the rubber on being released.
It will be found an easy matter to obtain long, graceful glides from
this model from the first. By launching it upward, it may rise to a
considerable height. When you have caught the trick of launching your
glider with sufficient force, try a spectacular flight. Set your forward
plane at an angle by inserting a block of wood between the stick. In the
case of metal planes, bend up the front edge.
A very slight upward elevation will answer. Gradually increase this
angle until the model sweeps upward and turns on itself. You will soon
be able to make the glider describe a complete circle or loop the loop
twice before landing. When traveling at such a high rate of speed, your
glider is likely to be dangerous and might inflict a bad cut, and the
flight should only be attempted where one has plenty of room.
These flights may be still further varied by adjusting the rear edge of
the vertical plane or rudder. By turning the rudder to the right, for
instance, the glider may be made to travel to the right or the direction
may be reversed. In this way the glider may be made to describe a
complete horizontal circle or several circles. By launching the glider
upward with this adjustment, it may be made to fly in a graceful spiral.
The success of a glider depends more upon its modeling and finish of its
planes than in the case of the model aeroplane. It must gain as much
support as possible from the air, since it has no motive power to keep
it aloft. Its head resistance must also be cut down. The ordinary
cloth-covered planes, which serve well enough for an ordinary model
aeroplane, will not carry a glider far. The planes must, therefore, be
of metal or wood, or when built-up planes are used they must be of the
most careful workmanship.
The simplest form of glider, excepting, of course, the paper model, is
made entirely of wood. A glider two feet in length will be found a good
size to experiment with. The model should be much heavier than an
aeroplane so that one need not take the care in its construction to
reduce weight which may make the construction of a model tedious. A
glider of this size may weigh upward of one pound. Under favorable
conditions, it will glide for two hundred feet, when launched from the
hand, while if it is thrown from an elevation, an upper window or a hill
top, it may travel considerably further.
Select a stout stick for your base, one inch square and two feet in
length. The main plane should measure fifteen inches in width by six in
depth, and the smaller plane ten inches by four inches. A thin board
about three-sixteenths of an inch thick may be used for the planes.
The front corners should be slightly rounded, and the rear edges cut
sharply away. These planes may be flexed by steaming. Hold the section
to be bent over the spout of a tea kettle until the wood is soft and
pliable enough to bend. If it does not soften sufficiently, immerse the
wood in boiling water. The plane should be flexed slightly upward just
back of the forward edge. A good curve may be obtained by heating the
under surface over a flame.
To hold it in position until it has dried and assumed shape, bend it
over a stick laid on a board and fasten the plane down by driving brads
around the edges and bending them over to keep it down. Leave it in this
position until it is dry and hard.
Your glider will fly better with a vertical rudder, as in the case of
the paper models. The rudder should be cut from a thin board of the same
material about six inches square. Round off one corner and plane or
sandpaper this front edge, which will be the entering edge. The entering
edges of the front plane should be prepared in the same way to reduce
the head resistance as much as possible. Nail this rudder to the side of
the stick directly beneath the rear or larger plane. It will be still
better if you mortise it neatly into the center of the stick.
The glider is thrown with the smaller end forward. For the trial flight,
mount the smaller plane at the extreme forward end and then move it
backward as you test it out, until the glider moves on an even keel. To
launch the glider, grasp the central stick from beneath at the point
where it balances, and throw it forward with all your might. Since it
travels at a much higher speed than a power-driven model aeroplane, it
requires much less supporting surface, while the planes may be spaced
much further apart.
When you have adjusted the planes, try throwing your glider at an upward
angle of say forty-five degrees. It should rise swiftly to a height of
upwards of fifty feet, turn backward on itself, and even describe a
graceful upward curve before coming down. Now try throwing it into the
wind or against a moderately strong breeze. Its course is likely to be
very irregular. It will dip and rise at many unexpected angles, and
probably travel several hundred feet in all before landing. During the
past year, a model glider has been built by Mr. W. H. Howell, Jr., to
glide a horizontal distance of 650 feet, while the actual length of the
flights has been upwards of 2,000 feet.