Proper Sizes For Frame.

Allowing that the biplane form is selected the construction
may be practically identical with that of the
20-foot glider described in Chapter V., except as to size
and elimination of the armpieces. In size the surface
planes should be about twice as large as those of the
20-foot glider, viz: 40 feet spread instead of 20, and 6 feet
deep instead of 3. The horizontal beams, struts, stanchions,
ribs, etc., should also be increased in size proportionately.

While care in the selection of clear, straight-grained
timber is important in the glider, it is still more important
in the construction of a motor-equipped flying
machine as the strain on the various parts will be much
greater.

How to Splice Timbers.

It is practically certain that you will have to resort to
splicing the horizontal beams as it will be difficult, if not
impossible, to find 40-foot pieces of timber totally free
from knots and worm holes, and of straight grain.

If splicing is necessary select two good 20-foot pieces,
3 inches wide and 1 1/2 inches thick, and one 10-foot long,
of the same thickness and width. Plane off the bottom
sides of the 10-foot strip, beginning about two feet back
from each end, and taper them so the strip will be about
3/4 inch thick at the extreme ends. Lay the two 20-foot