OK, if we want to get picky, lets recall first that the major body parts
are molded/vacuumed FRP, not Aeropoxy/Fiberglass components.
So while the Tg for Aeropoxy is indeed just over 190F, it is not the
critical, softening component of an XS wing. I don't recall anyone
ever specifying the Tg for the molded components, but I specifically
remember Andy, Russell, and Bob actively promoting only white finishes.
I remember when "YellowBird" came back from the paint shop and we
were all agast and predicting problems with it for Florida flying.
Second, it is not the direct sunlight on the upper surfaces which
are most vulnerable. Try instead measuring the temperature on the
undersurface of the wing when that wing is parked over hot asphalt
tarmac and radiating long infrared like a convection oven! Say like
the ramp where I did my 40 hours of test flight at Zepherhills, Florida,
where I did many hours shirtless in the cabin in August in temps
exceeding 90F in flight and much hotter on the ground.
The droops I've seen come from below, not above.
As I said above, in the US, we have "experimental" aircraft and we can
do what we want basically. On the other hand, I think it reasonable
that new builders be exposed to industry standard conventional wisdom,
based on experience and bad outcomes, and not just on an anecdote
or two.
There once was a bright red Lancair..........
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Ira N224XS
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