rlborger wrote:
>
> The UV protection is a component of the paint that blocks
> UV light preventing it from reaching the composite surface.
> According to Bob Setzer and my EAA Tech Advisor, Sonny Logan,
> this is extremely > important. UV will degrade the epoxy over
> time resulting in significant loss of strength of the composite
> structure.
The min. qualifications for EAA Tech Counselor is having built one
airplane, or commonly an A&P who need know nothing about fiberglass.
Arguably a viewpoint of people who should know is from System III Resins
(market: FG boat owners and builders) is their "The Epoxy Book." The say
there are even clear coatings you can buy to use as the sole coating over
FG which have requisite chemical UV blocking. Else, you can depend upon
the opacity of the primer and topcoat. When latter begins to break down,
maybe even 10-15 years, they say you best remove and recoat.
Their water-based 2-part epoxy primer (not as chalky and more opaque than
Smooth Prime per my sampling ) does not claim to be a special UV blocker,
and they freely discuss other primers for your boat if you want. Skipping
past the part about problems below the water line, they say you can
otherwise use about any primer, with the only possible problem of chemical
reaction with unreacted amines in the resin. Doubtfully any factor on
Europa's sandwich components, and we're careful on mix ratios for the
other stuff.
Can't insist above is definitive either, but at least there's not one
instance of even UV-suspected structural failure in the U.S. accident
database, including gliders back to year one of the data, 1962, just
failures for reasons like builder error in layup or AAL Flight 587.
Reg,
Fred F.
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