Page 1 of 1

Epoxy/ Graphite/ Silica

PostPosted:Mon Jul 27, 2009 10:28 pm
by traveling man
Can anyone discuss the merits (or not) of coating the bottom with epoxy/ graphite, also I hear mention that if you add Coloidal Silica (Cabosil) to your mixture that this adds a lot of durability to the concoction. I am going to build, or at least try to build a cedar strip kayak later this year that will be used on the upper Brazos river (lots of rocks). Will this make the bottom more durable or will the damage just not show as bad?

Re: Epoxy/ Graphite/ Silica

PostPosted:Tue Jul 28, 2009 9:05 am
by Piscator
I read a page with pics a couple of days ago explaining how graphite helps to prevent bad scratches on the epoxy finish. Actually makes the bottom 'slippery'. One pic showed a scratch on the clear epoxy finish and it turned into a smudge when it crossed onto the graphite finish. Help rocks to slide across the finish where the epoxy tends to 'grab' the rock and thus causes a scratch.

Search 'epoxy graphite' and a couple of different articles will be in there somewhere. I am currently looking for powdered graphite locally for a similar need.

Re: Epoxy/ Graphite/ Silica

PostPosted:Tue Jul 28, 2009 1:04 pm
by gerald
Graphite impregnated epoxy works by providing a sacrificial surface for rocks, stumps, logs, stobs, etc. to slide off easier. And it does work. A matt black finish rather than the shiny black is preferred. You expect this coating to eventually wear off and/or need to be resurfaced. I use to do it after every marathon race...almost.

Adding silica is different. This provides a slightly harder, slightly more durable surface, but it does not make the surface slippery.

For the materials to be used in combination it would be best to use silica in a fill coat with subsequent coats being graphite filled. A graphite impregnated coating is NOT a fill coat. It goes on after the fill coats.

Re: Epoxy/ Graphite/ Silica

PostPosted:Tue Jul 28, 2009 1:33 pm
by JEM
Progressive Epoxy offer telflon powder now, which sounds promising. However, I haven't heard of any feedback on it's effectiveness.

Re: Epoxy/ Graphite/ Silica

PostPosted:Tue Jul 28, 2009 2:53 pm
by gerald
Teflon powder. Hmmm--I'll have to try that. It's worth a shot. Maybe test it along side some graphite impregnated epoxy.

Re: Epoxy/ Graphite/ Silica

PostPosted:Tue Jul 28, 2009 3:27 pm
by JEM
It's worth taking a look at. Maybe you could do zebra stripes on the bottom of the hull. :mrgreen:

Re: Epoxy/ Graphite/ Silica

PostPosted:Tue Jul 28, 2009 5:10 pm
by Piscator
Does the graphite rub off on hands or clothes?

Re: Epoxy/ Graphite/ Silica

PostPosted:Tue Jul 28, 2009 5:34 pm
by gerald
Piscator wrote:Does the graphite rub off on hands or clothes?


No, it does not. When you sand it you can get a little on your hands, clothes...hair, eyebrows, etc.. Just funning. It's little worse than normal sanding dust.

Re: Epoxy/ Graphite/ Silica

PostPosted:Tue Jul 28, 2009 10:19 pm
by traveling man
Thanks for the info, trying to learn all I can before the build. So it goes (glass---epoxy---epoxy/ silica---epoxy/ graphite). Has anyone used Kevlar cloth on the bottom for more durability, or is this just overkill?

Re: Epoxy/ Graphite/ Silica

PostPosted:Wed Jul 29, 2009 8:02 am
by gerald
E-glass is the standard glass for layup. Let's, for example, say that e-glass costs $100. Then s-glass would cost $200. Kevlar would cost $400. And carbon fiber would cost $800.

So...it's not a question of whether or not kevlar is overkill. It may not be, but it's expensive. It's also opaque and yellow--meaning you won't see the wood if that's what you're after. Have I used kevlar and carbon fiber? Sure, but only in special circumstances.

Re: Epoxy/ Graphite/ Silica

PostPosted:Wed Jul 29, 2009 9:08 am
by preacher
gerald wrote:
Piscator wrote:Does the graphite rub off on hands or clothes?


No, it does not. When you sand it you can get a little on your hands, clothes...hair, eyebrows, etc.. Just funning. It's little worse than normal sanding dust.


Floors, walls, kids, pets, furniture, steering wheel . . .