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