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,

Laszlo

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   

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! 

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.

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!

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)?

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.