Following a test I did, I need to add important info re "foam may not
stand that" below. The blue foam will distort very badly above 170F
(77C), and seems a function of uneven temps around the component.
Even heating in a large, homemade autoclave is hard to achieve w/o
fancy methods of air circulation. That suggests bake temp well below
150F (65C), which reduces the effect of the postcure (increasing bake
time does nothing they say).
For U.S. builders, I note that PTM&W (Aeropoxy) does not discuss
postcure in their published info, beyond saying elevated initial cure
temp (unspecified) improves temperature resistance and strength. This
may be due to their marketing the product for aerospace applications
and residing in the native land of the product liability lawyer. If
you'll stand behind your room-temp cure specs, better not to send
amateur (oops!) builders down the garden path into methods you can't
control.
I'm starting to think that low-temp postcure does little, but if not
done, exact mix ratio, low humidity, fresh epoxy and all that become
more important. Neither in Rutan/Yaeger's book on the Voyager, nor in
the TV documentary, is postcure mentioned (would have some big
oven!). Great book BTW.
Regards,
Fred F., A063
Fred F. rambled:
> ...
> SP Systems, for example, states that
> max strength is NOT achieved without a 4-hour, 80C postcure, but foam
> may not stand that. They only otherwise document the effect of
> overnight cure + 16 hours at 50C, but hint that just 28 days at room
> temp is similar, with glass transition temps either way well above
> what you need for white paint on a sunny day.
>....
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