A piece of silk measuring 2″ longer and 2″ wider than each of the wing frames should be used in covering the wings, and this can be held in position by the use of pins prior to the actual sewing. The extra inch of silk on all sides of the frame is placed around the under side of the frame—in order that it can be made thoroughly taut when the silk has been sewn close to the edges of the frame. After the silk has been sewn close to the edges the pins may be removed and the surplus silk that hangs from the under side of the frame may be cut off. To make this silk airproof it should be coated with a thin coat of shellac or varnish and the wings should be thoroughly dry before being used. This coating, in addition to airproofing, will assist in making the covering perfectly taut, and also in making the wing ready for service when the entire model is ready to be assembled.
Asall other parts of the model are attached to the frame in addition to its having to standthe strain of the tightly wound rubber strands which serve as the motive power for the model, it must be made strong. It is therefore necessary to exercise care and judgment in making certain that the different units that make up the frame are rightly proportioned and are of the proper material. Just as in the large sized aëroplanes there are many types of bodies, so there are many different types of frames in use in model construction, but the standard, and for all practical purposes the best frame, resembles the letter A in shape, hence the name A type. The lightness of the frame depends entirely on the materials used and the manner in which it is constructed.
Some model flyers use but a single stick for the frame, but generally the A type frame is preferred for the reason that it is more durable, the wings can be more securely attached to it, and that it is possible of developing very much better results.