Speaking from an SP perspective, I would suggest any postcure be done after
applying
the Hibuild. Hibuild is not like an ordinary paint primer as it is really
a fairing compound and is intended to act as a sort of very thin filler that
can be sanded back until the desired profile is achieved on your component. This
is why it comes in different colours: by alternating the colours between
coats,when
you sand it back to get your profileyou can more easily see the high
and low spots. It isa solvent based epoxy product but the solvent is to allow
it to be easily coated/sprayed onto the job. Once the solvent has evaporated,
the resin and hardener cure in a similar way to a solvent-free epoxy product
like the 106 you are using for the thicker areas of fairing.
By postcuring the Hibuild and the 106 together you will increase the Glass
Transition
Temperature (Tg) of both systems to some degree (although this is not highly
important for a non-structural filler),but you will also take out most of
the shrinkage that might otherwise occur later. This shrinkage is what can give
fabric print patterns in your paint finish after the a/c's been standing in
the hot sun, particularly if the filler is only thinly applied and the resin
content of your laminates is low (as ideally should be the case). By sanding
after both 106 and Hibuild have been postcured you will have the opportunity to
sand away any 'print-through' that may have occurred in the postcure process.
Your final painting will then be onto a surface that is unlikely to shrink and
print much more.
On the paint front, when high-performance composite yachts are painted, as far
as I know no separate silver layer is used. Modern 2-part PU paints (such as the
Awlgrip range from US paints), are extremely good at both filtering out UV
---From the layers underneath the paint, and being UV-stable themselves and not
fading
or discolouring. They're not cheap but they do work well!
Hope this all helps.
David
-----Original Message-----
Subject: Finishing/painting
Hi all.
I have filled and sanded my Stabilizers prior to priming/painting. I'm doing
this
prior to fitting the top- to enhance the balancing procedure. The manual states
that a second bake must be done after filling - beforepriming, and my question
is: Is this really necessary?? My stuff is the British SP 106, withExpencell
that came with the kit - and for priming I'm going to use Hibuild from SP.
My next problem is UV protection. Do I have to apply silver before paint, or can
I just spray on a layer of clear Polyurethane UV protection as final top coat?
I'm approaching this first painting of mine with a certain awe, and should be
very
glad if any of you "masters" out there could shed any light on this. (I'll
have a Pro doing the actual spraying though!).
Hans, #334
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