ORIGINAL: longdan

I am scratch building a plane at the moment that has a foiled horizontal stab. The foil is added on to the top and bottom surfaces of the built up stab like ribs. They increase the overall thickness of the stab from 1/4" to about 1/2", but the spars are still only 1/4" thick, so the foil does nothing to add strength. And it's hardly a speed demon either - it's a Tyro Major, a 3 channel trainer from the 70's.