WINGS
One of the most important considerations in the construction of a model is the making of the wings. To obtain the greatest efficiency the wings must be carefully designed, with due attention to whether the model is being constructed for speed, duration or climbing ability. Attention should be given to streamline construction; that is, the parts of the wing should be so assembled that the completed wing would offer the least possible resistance to the air, if the best results are to be obtained.
For the main wing three strips of spruce, each 30″ in length, two of them being ³⁄₁₆″ × ¹⁄₄″ and the third ³⁄₁₆″ × ¹⁄₁₆″ are required. To make them thoroughly streamline all edges should be carefully rounded off and all surfaces should be smooth. A strip of bamboo at least 20″ long, ¹⁄₂″ wide, ¹⁄₈″ thick, should be cut into pieces, each piece to be 5 in. long. To secure the necessary curve, ¹⁄₂″ depth, the pieces of bamboo should be held in steam and slowly bent in a manner closely resembling the skids of an ordinary bobsled. When the curvature has been obtained, care should be exercised in cutting each piece into four longitudinal strips, from which twelve should be selected to be used as ribs, each to be ¹⁄₈″ wide. The bending of the bamboo preliminary to making the ribs is done in order to secure uniformity of curvature.
Diagram 4
When this has been done the ribs are ready for fastening to the sticks—entering and trailing edges—and each must be attached an equal distance apart. In order that the ribs may be evenly spaced it is necessary to put a mark every 3″ on the larger stick or entering edge of the wing, and also on the flat stick or trailing edge. The main beam which is of the same dimensions as the entering edge is afterwards fastened across the center of the wing, and does not necessarily need to be thus marked, as it is fastened to the ribs after the ribs have been attached to the entering and trailing edges of the wing frame. By holding the ribs one at a time so that the curved edge rests upon the entering edge where the mark indicates, as shown in [diagram 5], they should be fastened thereon by means of thread and glue. The rear end of the rib must be fastened to the trailing edge where the mark indicates, also by thread and glue.
After all ribs have been thus securely fastened to both edges of the frame the third stick, or main beam, should be attached to the frame on the underside, the fastening being made at the highest point of the curve of each rib. This main beam prevents the wing covering from drawing in the end ribs and adds very materially to the strength of the entire wing structure. To cover the wings fiber paper may be used and is a suitable material, but the best results, from a standpoint of flying efficiency and long service, are obtained by the use of China silk.
The frame of the forward wing or elevator is made in the same manner as is the main wing, but it is only 12″ in span by 4″ in chord, and is constructed without the use of a main beam. This wing has only five ribs which are made in the same manner as those for the rear wing, and each is placed a distance of 3″ apart.
Diagram 5
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.