I finished cutting two complete sets of wing tip ribs out of 12mm birch ply today. The picture shows one complete set plus the tip and tail ribs from the second wing. All the cutting was done with the CNC router using a 6.35 (1/4") cutter. The router was programmed for a 8m cut width so the machine does two passes at each height this ensures that the cut to final size is small and means that the finish and accuracy is superb. The program is set to leave 2.5mm thick holding tabs to hold the parts in place as the cut completes. It looks just like a model aeroplane kit (only bigger!) and removing the pieces is easy using a miniature saw blade in the Dremel. I've uploaded the coordinates of the ribs to the Yahoo Tailwind Group site if they are of use to anyone. 
