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Graphite Epoxy over Fairing Compound?

Posted: Tue Jun 11, 2019 12:23 pm
by Mike Bergen
Hey guys,

I'm rebuilding a Simmons sea skiff with fiberglass running surface and wood sides. Sanding paint off the bottom and going to do a graphite epoxy coating. There appears to be a fairing compound over the glass (see pic linked below). Is it safe to leave that in place and epoxy over? If so what prep work would be in order for proper adhesion? Using Marinepoxy.

Thanks guys!

Mike

http://gallery.bateau2.com/displayimage.php?pid=71641

Re: Graphite Epoxy over Fairing Compound?

Posted: Tue Jun 11, 2019 12:27 pm
by Mike Bergen

Re: Graphite Epoxy over Fairing Compound?

Posted: Tue Jun 11, 2019 1:05 pm
by narfi
If epoxy will stick to it, then graphite/epoxy will stick to it.

Re: Graphite Epoxy over Fairing Compound?

Posted: Tue Jun 11, 2019 1:35 pm
by Mike Bergen
So just clean with acetone and epoxy right over the smooth fairing compound?

Re: Graphite Epoxy over Fairing Compound?

Posted: Tue Jun 11, 2019 1:42 pm
by narfi
Well you have sanded it, so its not 'smooth', it has a good mechanical grip, so yes, as long as there isnt anything in the unknown fairing compound that is adverse to epoxy you should be good to go.

Since you dont really know what it is I would probably still do a small sample area first and see how it reacts.

Re: Graphite Epoxy over Fairing Compound?

Posted: Tue Jun 11, 2019 3:00 pm
by Capt UB
I don't know the boat, so
Is it wood and epoxy built?
Or was she built using polyester resin?

If polyester resin, you will need to clean first, soap and water then you need to make sure all curing agents (waxes and blush) is removed using acetone. Turn the rag over as you wipe. Sand again, with 80 or 100, then clean that mess up..

If your hull/bottom is fair, then put down the epoxy/graphite mix. This is what I have used and works great, there are other mixes out there...

My mix as follows: 8 oz of resin and 4 oz. slow hardener, then 1/2 cup of graphite power.

What I used;
BBC's
Graphite
MarinEpoxy with slow hardener

What I did;
Shifted graphite a few times.
Mixed epoxy and hardener.
Added graphite slowly as I mixed.
Rolled on slowly.
Wet on wet, 1/2 to 1 hour between coats.
Did not sand at all.

Re: Graphite Epoxy over Fairing Compound?

Posted: Tue Jun 11, 2019 3:23 pm
by Mike Bergen
Good info. Thanks Cap!

The boat has a fiberglass hull and sole with wood strake sides. No idea what kind of resin was used

Re: Graphite Epoxy over Fairing Compound?

Posted: Tue Jun 11, 2019 3:50 pm
by Mike Bergen
Here's a good write up on Simmons Sea Skiffs that also talks about the Silva-built boats with fiberglass hulls.

https://boatsandwaterfront.wordpress.co ... sea-skiff/

Re: Graphite Epoxy over Fairing Compound?

Posted: Tue Jun 11, 2019 8:25 pm
by Capt UB
Mike Bergen wrote:
Tue Jun 11, 2019 3:23 pm
Good info. Thanks Cap!

The boat has a fiberglass hull and sole with wood strake sides. No idea what kind of resin was used

Sounds like polyester resin, got to make sure it's free of mold release, wax.....

Re: Graphite Epoxy over Fairing Compound?

Posted: Tue Jun 11, 2019 10:59 pm
by Fuzz
You need to make sure that fairing compound is not too thick, hard and stuck to the hull well. If it is a weak point your whole job will be weak.