Message-ID: <000701c03308$35244be0$4cb188ce@pavilion>
From: "J. N. Cameron" <toucan@The-I.net>
To: "Lancair List" <lancair.list@olsusa.com>
Subject: Water-based urethane paint (Poly-Fiber)
Date: Tue, 10 Oct 2000 15:07:28 -0500
Reply-To: lancair.list@olsusa.com
Mime-Version: 1.0

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   Thought I'd pass on my experience so far with the water-based urethane
paint system sold by Poly-Fiber.  The primer (UV Smooth Prime) goes on well;
I rolled the first three coats as per the manual, then sprayed the last
three with an HVLP gun (Fuji, #3 needle).  The filler solids content of this
primer seems less than, say, DuPont Corlar or the WLS system, so it helps to
blade on a thin layer of SuperFill (great product!) to help fill the weave,
then sand that with about 320 grit prior to starting the primer.  I only
used SuperFill on seams and obvious bad areas on the bottom of the wings,
but I'll do the whole surface when I flip the wings to do the top next week.
When the primer has cured (longer is better), I found that a visible guide
coat (a fast-drying black lacquer, available at places that sell auto paint
supplies) helped a lot to get a smooth surface -- it's next to impossible to
see all the weave depressions on a flat white surface.

    The top coat has been a lot trickier.  DO NOT try to use an HVLP spray
gun.  I did on the first coat, and spent a day and half with 400 grit
sanding it smooth.  The HVLP gun apparently atomizes differently; the drops
are too large to flow out, and the hot air makes it dry too fast.  The
result is nasty -- rough in spots, bad orange peel, and where it was heavy
enough to flow out, it sagged!  Today's shoot with a conventional gun (40
psi air pressure, medium needle, medium paint flow rate) came out fine, but
I do have a couple of sags on the leading edges.  I thinned 10% with
distilled water, but maybe that was a mistake.  The margin between just
enough to flow out and too much (with sags) is VERY thin with this paint.  I
can't wait 'til I start shooting vertical surfaces -- my wings were laid
flat on tables for today's shoot.

   The manual I have says a conventional spray gun is better, but implies
that an HVLP gun will also work OK.  Don't believe it.  I'll stick with the
HVLP gun for priming, since the overspray is zilch.

    Yesterday I was ready to shop for solvent-based urethanes, but today I
guess I'll stick with it.  The advantages of not having clouds of
isocyanates, MEK, toluene, and other nasties filling the shop will outweigh
the tricky application problems, I think.

Jim Cameron,  ES #2 in progress (I think)


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