Successful Extraction of the First Test Spar!!  Today there was
much rejoicing as we hit a very significant milestone: under a
load of roughly 2000 lbs we pulled our first test spar off it's
aluminum mandrel  Spar extraction video  The carbon fibre tubes
that make up the primary structural members are constructed by
wrapping sheets of unidirectional carbon fibre around a tapered
aluminum tube. The carbon fibre is cured in an extremely long
oven, set to cool, and then pulled off the tube. At least in
theory. If the carbon is wrapped at an angle greater than about
35 degrees then, when it cools back to room temperature,
aluminum will shrink more than the carbon and the tubes pull
apart easily. If the wrap angle is less than 35 degrees then the
carbon shrink more than the aluminum and tubes end up clamped
together. Unfortunately, to get a structure that can resist
large bending forces, the angle needs to be quite shallow. To
maximize the structural strength and stiffness for a given
amount of material we designe