Fabricating the flap ribs is much like fabricating the wing ribs. The material required includes 1/4" last-a-foam, 1/2" last-a-foam, 1/2 plywood for inserts, and BID. The Flap Rib Templates are in the download section. The ribs are made from either 1/4" or 1/2" last-a-foam covered with 2 layers of BID on each side. There are a few hard points that are reinforced with plywood inserts. The second smaller slots toward the trailing edge of the ribs are not used and do not need to be cut out.

1/2" Ribs cutout

Once the ribs are cutout, the edges have the foam dug out an 1/8" or so all the way around and filled with micro. The rib is then sanded to match the pattern as closely as possible.

Installing Inserts

Finally, the 1/2" plywood inserts are installed in the 1/2" ribs that require them. these are micro-ed in and covered with two more layers of BID.

Alternatively the Ribs may be cut out of a sheet of precured sandwich by CNC