Sealing Fiberglass - What works for you?

[RV7ADRIVER]

I am building a 7A.
The inside of the engine cowl has what looks like a thin layer of fiberglass over the honeycomb.
It looks and feel porous.
I'm thinking this should be sealed.
Has anyone painted on a thin layer of epoxy resin?
Does that crack or flake off over time?
How does the 50% epoxy resin and 50% acetone mixture mentioned in the builders instructions for filling pin holes work out?
High temp paint is an option but what a pain to remove if a repair is needed.
Any experience with this is helpful.
Thanks in advance.

[rv72004]

Dont bother sealing it. The rough surface you feel is from peel ply. The cowling is obviously vacuum bagged and peel ply leaves a nice finish. I found mine cleans right up with a bit of degreaser at service time.

Some do paint etc, but I just see it as adding weight. If you paint it with epoxy it will stick very well. That is what peel ply does [prepare surface]

[N395V]

I would seal it. The rough peel ply surface will also retain the inevitable oil and that will catch dust. Prime and paint and it will be much easier to keep clean.

[cytoxin]

funny you should ask, i am doing this right now. i painted the inside with akzo. as far as thinning epoxy with acetone, it woked fine on the top cowl which i had previously coated with a straight mixture of resin,it took 3.5 hrs @95 deg. to be dry enough to sand.
. got brave and did the bottom with thinned 50-50 first time on. it took a lot longer to dry but sanded fine. second coat on the bottom took days to dry and seems uncured at times while sanding. it would sand fine wet but would roll when sanding dry. luickily it sands dusty dry today.
from now on i will just use straight resin spread with a new yellow bondo spreader. the brush streaks left by the brush were far more trouble to sand out than the streaks left by the spreader. spreader left two ridges the brush left multiple ridges and made sanding a dog.
my observation is that the acetone evaporates by about the third stroke and you have nearly pure resin any way. This makes me wonder if it is taking some of the hardener with it and increases the drying time. dunno

[mike newall]

If you are using West System - use a small radiator roller - it puts a thin coat on really well. Used it on all sorts of applications from rejuvenating fabric with dope, laying up deck cloth on a One Design, retouching 2 pack without all the spray problems.

Use the gloss roller for best results.

[RV7Guy]

Clean before doing anything. Use a high pressure nozzle, blow it out. Clean with acetone. Sand with rough paper, 80-100 grit. Clean again. Roll epoxy as described. No real need to thin. Don't use too much. Sand smooth. Done.

On the bottom, you might use some heat shield. Doing the above will dramatically assist in the adhesion of the heat shield.

[Captain Avgas]

Originally Posted by mike newall

If you are using West System - use a small radiator roller - it puts a thin coat on really well. Used it on all sorts of applications from rejuvenating fabric with dope, laying up deck cloth on a One Design, retouching 2 pack without all the spray problems.

Use the gloss roller for best results.

Mike, what's a "radiator roller" (got a photo). And can it be used to apply the epoxy straight (ie UNthinned).

[glenn654]

The cowling of my -4 had been coated w/ epoxy which chipped and flaked w/ time and handling. What I would recommend for the lower cowl is to sand it smooth, thoroughly clean and apply Vans heat shielding to it. It will protect against heat damage, provide an impermeable surface to protect from oil staining....works great for me. And the top...you could paint it if you want but it will be fine w/o anything else.

Glenn Wilkinson

[mike newall]

It's the small rollers you can get at Home Despot - about 4" long - like mini rollers for doing detail work Try either the foam one if using non volatile stuff like epoxy or the latex fluffy ones if using dope/solvent paint.

Use the epoxy unthinned but warm - lay out in a flat plate and play a hair dryer over it to thin it out - works well

[DanH]

I've mentioned it before....you can buy an epoxy with the viscosity of water; System Three ClearCoat. Its intended use was soaking into wood for moisture sealing, which it does very well. It also soaks into exposed fiberglass.