ry than one done with a
third timber.

As the frame pieces are generally about 1 1/2 inch in diameter, the
tongue and the groove into which the tongue fits must be correspondingly
small. Begin by sawing into one side of one of the frame pieces about
4 inches back from the end. Make the cut about 1/2 inch deep. Then turn
the piece over and duplicate the cut. Next saw down from the end
to these cuts. When the sawed-out parts are removed you will have a
"tongue" in the end of the frame timber 4 inches long and 1/2 inch
thick. The next move is to saw out a 5/8-inch groove in the end of the
frame piece which is to be joined. You will have to use a small chisel
to remove the 5/8-inch bit. This will leave a groove into which the
tongue will fit easily.

Joining the Two Pieces.

Take a thin metal sleeve--this is merely a hollow tube of aluminum
or brass open at each end--8 inches long, and slip it over either the
tongued or grooved end of one of the frame timbers. It is well to have
the sleeve fit snugly, and this may necessitate a sand-papering of the
frame pieces so the sleeve will slip on.

Push the sleeve well back out of the way. Cover the tongue thoroughly
with glue, and also put some on the inside of the groove. Use plenty
of glue. Now press the tongue into the groove, and keep the ends firmly
together until the glue is thoroughly dried. Rub off the joint lightly
with sand-paper to remove any of the glue which may have oozed out, and
slip the sleeve into place over the joint. Tack the sleeve in position
with small copper tacks, and you will have an ideal splice.

The same operation is to be repeated on each of the four frame pieces.
Two 20-foot pieces joined in this way will give a substantial frame, but
when suitable timber of this kind can not be had, three pieces, each 6
feet 11 inches long, may be used. This would give 20 feet 9 inches, of
which 8 inches will be taken up in the two joints, leaving the frame 20
feet 1 inch long.

Installation of Motor.

Next comes the installation of the motor. The kinds and efficiency of
the various types are described in the following chapter (IX). All we
are interested in at this point is the manner of installation. This
varies according to the personal ideas of the aviator. Thus one man puts
his motor in the front of his machine, another places it in the center,
and still another finds the rear of the frame the best. All get
good results, the comparative advantages of whi