First job today was to calculate the dimensions for a stub rib rear section which forms the rear inside edge of the wingtip (top right of the picture). This is positioned 1" outboard from the last main rib to allow the aileron mass balance to fit between it and the wingtip to streamline it in normal flight. As before the dimensions for the stub rib were fed in the the CAD/CAM package and a test piece cut out on the router. Then it and the three tip ribs were located on the spars in their correct positions. A blank for the trailing edge was made by sawing along the diagonal of a 2" x 1" section of spruce to make two triangular sections. When angled at 45 degrees along the line of the wingtip trailing edge this section matches the wing section nicely and will need relatively little finish sanding. The ends of the trailing edge were cut to 45 degrees and the outer end pinned to the tip rib. Then the trailing edges of the two intermediate ribs and the stub rib were carefully marked and cut at the required angle. A piece of 3/8" spruce was cut to form the leading edge and the front of the ribs bevelled to match. The picture shows the wing tip assembled on the spars with just one panel pin in the tip rib the only thing holding it together.Next job is to procure some 15mm birch ply, cut the final ribs for both wings, buy some Aerodux glue and then assemble and glue the two wingtips.
