I wonder if anyone has tried this fiber. The claims on the website are amazing. They claim has a higher strength to weight ratio, a higher Tensile Modulus, a higher abrasion resistance and flex life, better light stability, and chemical resistance, than Kevlar.
In addition to the problems Scobie mentioned, the other BIG problem with Spectra/Dyneema is cold flow. If you subject it to a steady load, it "relaxes" or "creeps". All plastics do this to some extent, but polyethylene fiber is in a league by itself with regard to this. A wing of a full-scale aircraft made from this stuff would develop elliptical anhedral just from sitting in the hangar with its own weight pulling down on it.
Back when we were developing the 2-meter Chrysalis, I tried some cable-actuated, spring-opened, cable-closed spoilers for it. The Spectra line I used was nice and slippery and ran nicely through its guide tubes, but relaxed so much every night just form the tension from the springs that every morning the spoilers would be halfway open.
Later I tried it for pulling some dihedral into the wings of a LiteStik to get better roll response. It worked OK right after I installed it, but the next morning, most of the extra dihedral was gone. It was after this that I developed the polyhedral mod for the LiteStik. Much better roll response, less drag, less stress on the wing roots, doesn't take any longer to install, and the dihedral is still there the next morning, as well as every morning after that.
Spectra (or its equivalents) has its place, but if there is a need for something with dimensional stability, Spectra is usually not a good choice.
Don Stackhouse @ DJ Aerotech [EMAIL PROTECTED] http://www.djaerotech.com
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