graphite coating

I know this is a frequently discussed topic, but I am still confused about the mix ratio for graphite.  I'm building a WD12 and was considering a graphite bottom with dynel strips.  The area I launch and land is small rocks and cobble so scratches will be unavoidable.  I've launched a skerry from the same spot for about 15 years and have never had to do more than touch up paint, but I hop in and out of that in shallow water and I'm thinking that in a kayak there is going to be more abrasion, so why not plan for it.

From past discussion it seems the recommended ratio is 50/50 after the weave is filled. 

But the product page says no more than 10% by volume.  So with an abundance of caution I wanted to confirm - is this the right stuff and should the max 10% be ignored?

Is just a single graphite coat sufficient?

Thanks in advance for any help,

- Bob

7 replies:

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RE: graphite coating

Hi Bob,

I've posted many replies to this same question over the last eleven or so years and may be the source of that 50:50 ratio. That is just what has worked out well for me over the years on various boats I've built. It's a softer and more slippery coating than what you get with 10%. I think that it works better, but that could be because of the kind of bottom I run aground on (mud with embedded oyster shells and occasional rocks and waterlogged wood). The slipperiness is more important than the hardness where I paddle.

If I am the source of that thicker mix, that's why. It's personal preference empirically developed over a decade of experience. Your mileage may vary.

You could go with the recommended lower ratio and if it works out for you, then fine. If after a few outings you decide that you want a slipperier mixture, it's real easy to just clean off the dirt and apply another coat that's got more graphite in it. That way the original coat acts as a hard base coat.

Have fun,



RE: graphite coating

Thanks Laszlo - I'm not second guessing, just making sure I'm not overlooking something, especially when it's right there in plain English.  There is a lot of chemistry going on, and I wanted to make sure manufacturers statement wasn't an indication that I was heading down the wrong path.

Experience is a great teacher, but in this case I would like it to be someone elses!

- Bob   

RE: graphite coating

I'm pretty certain that Laszlo is the source of the 50:50 mix - I read his logs in preparation for putting a graphite mix on the bottom of my 17LT. 

Being a cautious sort of guy and knowing that I was not using the same epoxy as Laszlo* I ran a couple of tests and for me 50:50 was very thick and unworkable. I did a few more test pieces with 20%, 30% and 40% and eventually put two coats on with a 30% mix and a final coat with a 40% mix. 

Like you Bob, it's rocky, stony and very gritty sand around here but the bottom of the boat is good. I don't run her into the beach though as I'm pretty sure that would create wear on the base of the stem, I come in parallel to the beach and struggle out. :)  I also have a Skerry but the bottom of that is treated with anti-fouling paint as she spends the summer months moored 20 metres off the beach.

*I live in S.W Turkey and I simply can't get the named supplies that are common in the U.S. Buying from the States with be simply too expensive so I get what I can. And test! 

RE: graphite coating

Yambo - I love that you have both a Skerry and a WD14 with Sail Rig.  We obviously think alike!

That's a good idea too - I could do some test patches just to see what's up.

RE: graphite coating

Powdered graphite's a great additive to epoxy for its lubricating properties. I added a couple of coats on the insides of my Waterlust's daggerboard trunk and the rudder cassette for just that reason. Also formed some 'lubricating' bushings for the rudder pivot bolt (Drill-fill-Drill methodology) with the same mix, about 25% graphite by volume to resin+hardener mix.

You want a really tough, abrasion-resistant coating though I'd look to adding powdered aluminum to mixed epoxy. A little can go a long way!

RE: graphite coating

spclark - ok, that's another interesting datapoint for graphite use

what does the aluminum powder look like as a coating?  Do you paint over it (obviously the paint will get scratched, but that's repairable)?

RE: graphite coating

Jamestown says it can be painted over so I'd assume it'd need prepping for painting as with any other epoxy-clad surface.

By itself as an epoxy additive it adds a measure of UV protection; when I bought some decades ago from Gougeon Bros. the only use I could think of at the time was for weatherproofing the luan roof for a bird-feeding platform I'd built. Exposed to Chicago-latitude Midwest seasons it lasted almost nine years & that was with three coats when first applied. I still have 95% of that left; it's like aluminum 'dust'. Probably flammable too as aluminum powder's a common ingredient in fireworks.

It cures to a slightly metallic-looking grey surface, not unlike what you may have seen of aluminum-bearing stuff sold for roof coatings.

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