Graphite powder on bottom of my boat. how much

[mrxireland]

Just like the title says. Im going to put some graphite powder on the bottom of my hull to cover a few bad patches that appeared on it.

Ive been building a cedar strip rowing boat and now im near th eend of it, i noticed a few blackish patches underneath my fiberglass and it really catches the eye when looking at it and TBH, it spoils the look of the boat. Im well pleased at teh way the boat has turned out apart from this patch so im going to mix up some epoxy and get some graphite powder and cover a football shape at the bottom of my boat.

Im wanting to know how much should i order if im going to cover the bottom football piece of the hull and is there any special graphite powder i need to get for marine use or is the stuff all the same.

[RodB]

Mixture for graphite in epoxy... one heaping teaspoon per mixed ounce of epoxy (resin/hardener) ... Graphite powder is available from West, or System Three, etc... usually comes in a quart can and that will last you for a few projects. Just mix it, use a 3.5" roller and roll and tip it... when cured, attach a pieces of scotchbright to a square finishing sander... and smooth and dull the entire finish... so its fair and smooth... last, wipe it down with teak oil so it looks a bit shiny and uniform...


http://forum.woodenboat.com/showthre...graphite+epoxy

RodB

[mrxireland]

Mixture for graphite in epoxy... one heaping teaspoon per mixed ounce of epoxy (resin/hardener) ... Graphite powder is available from West, or System Three, etc... usually comes in a quart can and that will last you for a few projects. Just mix it, use a 3.5" roller and roll and tip it... when cured, attach a pieces of scotchbright to a square finishing sander... and smooth and dull the entire finish... so its fair and smooth... last, wipe it down with teak oil so it looks a bit shiny and uniform...


http://forum.woodenboat.com/showthre...graphite+epoxy

RodB

I dont unederstand quarts and ounces. Im in irealand and we use a different system.

[wizbang 13]

I used it for the first time on a small cold molded boat.
I do not like it, the black powder when sanded was obnoxious. lotta sanding.
And , it remains fair, but dull. If I had to coat it with teak oil to make it shiny, I would just paint it with LP black.
Teak oil will not be scratch resistant, which is one of the things the graphite is supposed to offer .
I would suggest a test on another piece first.
a heaping teaspoon is about how much I used for a pint.

[Bob Cleek]

I dont unederstand quarts and ounces. Im in irealand and we use a different system.

Google is your friend. Save this one: http://www.france-property-and-infor..._converter.htm

[timo4352]

I just used it for the first time on my present build. After rolling and tipping I still had some tiny bubbles showing. I went over it with a few passes of my heat gun and it smoothed out pretty nicely. I guess the heat pops the bubbles. YRMV
Tim

[Todd Bradshaw]

I think that for color and UV blocking, Gougeon Brothers suggested something like 10% graphite to 90% epoxy. For abrasion resistance, you can boost the amount of graphite a bit if desired, though the more you add, the softer the final product is. It may be more slippery, but may scratch deeper, so it's hard to say what's best (some folks also mix in a little Cabosil to harden it more). The nicest graphite bottoms I've seen were wet-sanded (probably 400 grit or so after flattening and fairing) to a really nice satin-gray finish with no oil. They were pretty elegant, though sanding that stuff is a rather obnoxious job. If the goal is simply to cosmetically cover ugly spots, paint would be a heck of a lot easier. If you also want some abrasion protection, then graphite might be worth doing.

p.s. If you have excess left over, pour it into a plastic container and let it harden. Little blocks of epoxy/graphite can be handy when you need to make things, like the pads under these winches and cheek blocks.

[RodB]

I used it for the first time on a small cold molded boat.
I do not like it, the black powder when sanded was obnoxious. lotta sanding.
And , it remains fair, but dull. If I had to coat it with teak oil to make it shiny, I would just paint it with LP black.
Teak oil will not be scratch resistant, which is one of the things the graphite is supposed to offer .
I would suggest a test on another piece first.
a heaping teaspoon is about how much I used for a pint.

Lots of information here: about graphite in epoxy... http://forum.woodenboat.com/showthre...graphite+epoxy

First, if you know how to apply graphite powder/epoxy over a large area rolling and tipping it will be shiny and smooth... depending on your speed and technique.

Sanding it makes for a nice opaque black fair surface that will slide easier off of hard objects and not be damaged by going on and off a trailer. Its very tough but with the graphite the epoxy underneath will be protected from UV. If you want it shiny but fair, applying Teak oil is an easy way to make a large surface look uniform. ITS VERY EASY TO REAPPLY TEAK OIL EVERY NOW AND THEN IF IT GETS SCRATCHED enough to bother you. The teak oil is only to make it easy to have a large surface look very uniform. Just don't use it and you can just leave the surface matte. Its still hard to beat for a tough bottom that will go on and off a trailer and be protected from UV.

You didn't used enough graphite powder per ounce if you only added one teaspoon to a pint of epoxy... its not a colorant... its graphite powder used for increased lubricity of a hull surface.

RodB