Much more attention is paid to designing the skids for model aeroplanes
in America than abroad. Since the American model usually rises from the
ground under its own power, this detail of construction naturally has
come to be of vital importance. By attacking the problems faced by the
designers of large aeroplanes, our work is helpful in developing the
science of aviation as a whole.
Nothing has been found better for building skids than cane or bamboo. A
chassis may be made of these materials which will weigh but a fraction
of an ounce, so that even the most elaborate skids will add but little
weight. They are, besides, exceedingly elastic, which makes them easy to
work, while this quality enables them to take up the shock of a violent
landing. The thinnest sizes are best for our purposes. The reed
one-eighth of an inch in diameter will answer for all ordinary models.
To prepare reed for working, soak it for an hour. Another plan is to
heat it slightly over a flame, when it may be bent with little danger of
breaking. In case of a bad smash during a meet such skids may be readily
pieced out and repairs made so quickly that the model need not be kept
long out of the contest.
[Illustration: A model with limited plane area built by R. Barry]
[Illustration: An interesting experiment in metal frame building by R.
Fisher]
The simplest skid is made by splitting a section of reed, or splicing
it, to form a Y, and attaching the upper ends to the bottom of your
motor base. The lower end is then bent into a half circle. Wrap the reed
tightly at the crotch to keep it from splitting, and touch the wrapping
with glue. To make such a skid stable, join the two pieces by a cross
brace. The skid should slant backward at a slight angle to reduce the
friction on starting. Several methods of bracing such a skid are
suggested in the accompanying photographs of models.
A stronger skid is formed by turning the reed to form ellipses and
attaching them to the motor base. The curved parts will require bracing.
Two diagonal braces will keep them in position. Some model builders
prefer to shape the skids at the bottom, so that only a single point of
the reed comes in contact with the floor. This plan makes it possible to
shape the skids into several graceful forms which help to make the model
attractive.
Still another plan, followed by some of the most successful model
builders, is to shape the skids like the runners of a sleigh. In some of
the Percy Pierce models this year, about six inches of the rear skids
come in contact with the ground. It might be supposed that the friction
in this case would be considerable, but this particular model is one of
the quickest to rise. This design has the great advantage of being
extremely elastic and letting the rear of the model down gently after a
considerable fall.
Some model builders still retain the wheel skid in a much simpler and
lighter form. The miniature bicycle wheels do very well for scale
models, but since they are likely to add an ounce or two to the weight
of the aeroplane, they are prohibitive. To avoid this weight, the wheels
may be made of simple disks of wood cut very small. A wheel one-half an
inch in diameter, cut from a board one-eighth of an inch thick, weighs
practically nothing and affords sufficient support. These may be mounted
very simply on axles made of bent wire attached to the feet of the
skids. Sandpaper the rims to an edge in order to reduce the surface
presented to the air. Since their surface is edgewise to the line of
flight, they will offer very little resistance.
The wheels on some of this year’s models are formed of wire disks
covered with silk. The weight of these wheels is practically nothing,
and they add much to the appearance of a well-finished model. Wire disks
which may be covered in this way may be bought from the supply houses.
It requires rather a skilful hand to shape the wire into perfect circles
which will run easily. The covering again is a very nice operation. The
silk wheel is not recommended for the beginner; but for one who is
anxious to finish his model to the last detail as attractively as
possible, they form an interesting feature.
Ping-pong balls make serviceable skids. Since they are carefully
rounded, they will turn easily. To mount them, drill a hole for the wire
shaft or axle, taking great care to have it pass through opposite points
of the sphere. The wire may then be bent above it and attached to the
skid. The celluloid turning on the wire axle produces practically no
friction, and the ball offers very little resistance to the air. The
balls are, of course, extremely light and add little to the weight of
the model.
By combining the skid and wheel form of support, your model will gain
the advantage of both these devices. The general form of the Farman skid
may be followed. The skid in this case should be fairly heavy, strong
enough to hold its shape, although elastic enough to take up a
considerable shock. The simplest plan is to connect the two skids by a
cross piece, and use this as the axle for two small wheels, mounted on
the outside of the skid. This plan enables the aeroplane to rise with
the minimum amount of resistance and land at the end of a flight with
protection.
In the collapsible skid we find one of the most interesting novelties of
the year. This ingenious mechanism, which is very easy to adjust, and
which is placed under the front of the model on rising from the ground,
is drawn into a horizontal position extending out before the machine and
acts as a buffer, an aerial cow-catcher. Any simple form of skid may be
adjusted in this way. The upper end or ends are merely fastened to the
motor base so that they will swing easily back and forth. From a point
half way down the skid, a rubber band is run to the front end of the
motor base. When the model is set on the ground, after winding up, the
skid is pulled back to form the forward support. It will be found
necessary to adjust it to stand at a trifle less than the vertical. The
rubber bands must be just strong enough to permit the skid to stand in
this position when held down by the weight of the machine. As the
machine rises, the skid is, of course, released and instantly snaps up
to a horizontal position.
A new interest is lent to model aeroplane building by mounting them on
pontoons contrived to float them on the water. Several large men
carrying machines have risen from the water, notably the Curtiss model.
It is believed by some aviators that since the water offers less
friction than the earth or than a wooden runway, it is easier to rise in
this way.
The builders of modern aeroplanes have been quick to adopt this idea.
The models are mounted on miniature pontoons, and after winding up the
motors are released in the usual way. An actual photograph of a model
thus mounted in the very act of rising clear on the surface of the water
is reproduced as a frontispiece of this volume. The pontoons, it will be
noticed, consist of two small pieces of board, placed almost directly
beneath the planes. The model is mounted on these pontoons by ordinary
skids of reed. The angle of the planes with the surface of the water is
the same as in the ordinary mounting. The pontoons are kept as small and
light as possible.
To start the machine, the propellers are wound up in the usual way. It
has been found that a model would rise rather more quickly from the
water than from the land or within a few feet. As our photograph shows,
the pontoons leave a slight wake behind them in the water. Once started
to rise, however, the machine rapidly gains its elevation. One advantage
of the pontoon skid flying over the water is the safety it insures on
landing. At the end of such a flight the model drops into the water, but
with little danger of breaking any of its parts. It will be found
interesting to experiment in mounting the model loosely on pontoons, so
that when it rises it will leave them behind, thus doing away with the
increased load.