Mike, BID is a short-hand call-out for Bi-directional fiber glass cloth; approximately the same number of fiber strands crossing each other at 90 degrees in the woven cloth. (Lots of weave patterns for fiber glass cloth on the market: plain weave, Crow Foot, Satin weave, etc. The Aircraft Spruce catalog has a good reference for the home builder.) The BID will have approximately the same strength and stiffness in 90 degree directions. Most plans call for the BID to be applied at 45-degrees fabric orientation to the main spar to enhance torsional strength of the wing. The Diehl wing skins use this same 45-degree fabric orientation when they are constructed at the factory.
Sid Wood Tri-gear KR-2 N6242 Mechanicsville, MD, USA ---------------------------------------------------------------- > "The Diehl wing skins are a sandwich with inner and outer layers of 2 BID on a foam core. I have talked with other builders that have used the Diehl skins and not used the spar extensions; they just use the rather stiff skin as a monocoque stressed skin. The Diehl skins extend the horizontal stabilizer and elevator span 3-inches each side for an increase of 6 inches more than the KR-2 plans." Thanks for posting that info on the Diehl tailfeathers & skins. I never knew the stabilizer had three inches extra. Nor do I know what BID is . . . but I can Google fu and find out. Whatever it is it sure holds up well. They literally still look like new after thirty years, tops and bottoms. Whatever BID is, it's good stuff. Mike KSEE
