Beam me up Scotty... There is no intelligent life on this planet.

Mix up a Roofycollada.

What is PVA, and where can it be obtained? Thanks!

Dave

Poly vinyl alcohol. It's a spray on mold release (spray with paint sprayer). You build up several layers to form a film that is almost like saran wrap and can be peeled off when cured or washed away - it's very water soluble and easy to remove. It makes a pretty bullet-proof mold release or an air barrier for gelcoat that you need to cure in the open air.

When spraying on a waxed surface, you have to mist on the first coat or two and let each coat dry for about 15 minutes. Then you can lay down two or three nice glossy coats. It dries pretty smooth and glossy but it's about impossible to get a completely glassy smooth finish on it so it's probably not the best thing out there to use as a release for a very high end mold. It is waterbased so it works very well with ester based resins. You have to be sure to get a thick enough barrier when using epoxy...but it doesn't seem to affect the finish of the epoxy at all.

I buy mine at www.uscomposites.com but I'm sure www.fiberglasssupply.com or www.aircraftspruce.com has it as well.

What's the best epoxy (with what characteristics) to use for this? I've decided to use epoxy and a pigment to color it in order to avoid that yellowing. Also, can you use cabosil with all epoxies to thicken it?

ANY decent epoxy , mixed with :
West-Systems 404 High-density adhesive filler ; will do
the job.

Do NOT use just any filler,(like micro-balloons) because
they are hollow spears that will break down with time.Some
fillers were designed as a sanding/fairing compound, and won't
work for a structural application !!

The splice i made for my Hobie-21se, i actually installed grease-nipples, and pumped in the filler with a grease-gun
from Harbor freight; then removed the nipples after the epoxy
gelled-off, but before it cured.
It worked Great !!

Bille

I've had good success using teflon tape on the beams and West Six-10 as the bedding compound.


-Mike

Packing tape.

No matter what pigment you add (unless it's black and use also use aluminum powder), epoxy will yellow.

The boat I have now had the beams previously bedded (by POs) with gelcoat. It's holding up just fine and where it oozed out it matches the boat perfectly.

I also just wax the beams with four or five coats of a good carnuba wax. I've never had a problem with them releasing (you have to go to some advanced etching to get epoxy or polyester resins to adhere to aluminum).

PVA is 2-4 mils thick in a heavy application (0.002"- 0.004"). It can be applied thinner to aluminum (0.001-0.002"): http://www.rexco-usa.com/documents/TDS_Partall%20Film%2010.pdf
If 0.002" is a concern to you, go ahead and not use the PVA. PVA guarantees a release every time.

I use 2-3 coats of wax (Rexco Partall Paste #2), followed by a light brush coat of PVA, tape off beam sockets with drop cloth and add thickened (with cabosil) gelcoat to the sockets. Plug the holes in the beams with the Partall Paste wax and avoid putting gelcoat near the bolt holes.

So does waxing the bare aluminum beam and not going through the extra step with PVA. I've seated more than my share of beams and they all released with a slight tap with a rubber mallet.