Hi Russ, 

just to clarify, i am assuming you have a normally glassed bottom but that you want to coat the bottom panels with epoxy with some graphite powder mixed in to give it a 'black' look.  if you meant something different (i.e. using carbon fibre cloth on the bottom) please just let us know.

ok, so if you want the black look you will mix the epoxy with a little bit of graphite powder.  you can actually make it black/opaque with relatively little graphite powder such that your epoxy will not be appreciably 'thickened' compared to straight epoxy...and as such, you can just roll it on with one of those yellow rollers and then tip it out with a foam brush.  it won't really be  'textured' any more than a pure epoxy fill coat.   then you would just sand as normal as if you were doing a normal plain epoxy bottom.

so i would dispense with peel ply for this preperation....i don't think it will save you subtantial time.   the final result will be black and it should be just as smooth as a regular epoxy finish.....which really depends on how much time/attention you spend on your finish sanding.

do note, that the graphite does not protect against UV...so i would still consider varnish over it.  you can also paint the bottom black and get a similar effect.   i would also point out that the graphite in epoxy is similar to the graphite in a pencil. so if you don't overcoat it, it can leave marks on things like your shirt (like a big pencil).

hope that helps

h

Russ,

I'm going to be respectfully disagreeing with Howard here - a very rare thing for me to do.

Part of the difference depends on why you're putting on a graphite/epoxy mix. I use it to make a scratch-resistant bottom. In that spirit, I use a 50-50 mixture by volume. That leaves the bottom very dark black, slippery and soft. That prevents rocks and such from getting a purchase and continuing with a long scratch. They tend to just slide off.

With that much graphite, it really is like a pencil lead. It's also got the orange peel finish. If you try to sand it smooth, the bottom ends up shiny gray like the pencil lead and you end up covered in black dust like a coal miner.

Peel-ply will leave a matte surface. If you want it smooth you'll have to sand it and you'll be back in the mine again.

With that much graphite, you do get UV protection. The protection is good, even at lower concentrations. I have one boat with a 15% by volume graphite bottom that is over nine years old - no solar damage.

Varnish over graphite/epoxy negates its anti-scratch properties. It hides the soft slippery graphite under a hardened varnish surface. You might as well use black paint.

As far as drag penalties, I haven't noticed any but then again I haven't looked for it. I like to tell myself that the orange peel works like the laminar flow bumps on dolphin skin. It most likely doesn't, but it sounds good :-)

Have fun,

Laszlo

Thanks Howard and Laszlo!

Howard, I had in mind more of what Laszlo described.  I was just wondering if the peel ply would smooth out the orange peel surface.  

Laszlo,  I'll be filling the weave on the bottom panels with expoxy/glass balls, followed by sanding, then a coat of 50/50 epoxy/gaphite mix.

Target date for launch is Oct 12th

Russ

I tried one coat of graphite & colloidal silica for a tougher mix total 50% by volume with the resin/herdener mix, then another coat of just graphite 50% by volume to try and combat our brutal PNW beaches.  So far, the bottom itself is faring well except for the hard groundings at the launch ramp.  I'm actually contemplating using 3M 5200 black on the skids to see if that helps.