. This makes five rectangles. Be sure
that the points of contact are perfect, and that the struts are exactly
at right angles with the horizontal frames. This is a most important
feature because if your frame "skews" or twists you cannot keep it
straight in the air. Now glue the ends of the struts to the frame
pieces, using plenty of glue, and nail on strips that will hold the
frame in place while the glue is drying. The next day lash the joints
together firmly with the shoe thread, winding it as you would to mend a
broken gun stock, and over each layer put a coating of glue. This done,
the other frame pieces and struts may be treated in the same way, and
you will thus get the foundations for the two planes.

Another Way of Placing Struts.

In the machines built for professional use a stronger and more certain
form of construction is desired. This is secured by the placing the
struts for the lower plane under the frame piece, and those for the
upper plane over it, allowing them in each instance to come out flush
with the outer edges of the frame pieces. They are then securely
fastened with a tie plate or clamp which passes over the end of the
strut and is bound firmly against the surface of the frame piece by the
eye bolts of the stanchion sockets.

Placing the Rib Pieces.

Take one of the frames and place on it the ribs, with the arched side
up, letting one end of the ribs come flush with the front edge of the
forward frame, and the other end projecting about a foot beyond the rear
frame. The manner of fastening the ribs to the frame pieces is optional.
In some cases they are lashed with shoe thread, and in others clamped
with a metal clamp fastened with 1/2-inch wood screws. Where clamps and
screws are used care should be taken to make slight holes in the wood
with an awl before starting the screws so as to lessen any tendency to
split the wood. On the top frame, twenty-one ribs placed one foot apart
will be required. On the lower frame, because of the opening left for
the operator's body, you will need only twenty.

Joining the Two Frames.

The two frames must now be joined together. For this you will need
twenty-four aluminum or iron sockets which may be purchased at a
foundry or hardware shop. These sockets, as the name implies, provide
a receptacle in which the end of a stanchion is firmly held, and have
flanges with holes for eye-bolts which hold them firmly to the frame
pieces, and also serve to hold the