Graphite over a previously painted bottom?

I am trying to refurbish my 10+ year old Chessy 18.  The hull is painted with Brightside Yellow.  I would like to apply the epoxy/graphite mix to the bottom of the hull.  Do I need to completly sand off the paint?  I have already sanded into the glass in some places, any tips will be greatly appreciated!


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RE: Graphite over a previously painted bottom?

Yes, epoxy does not like to be applied over other finishes.

But I'm personally not a fan of graphite/epoxy. I once emailed Jim Watson, the tech guru at West Systems, who said adding graphite powder to epoxy mainly changes the color to black. It does provide some UV protection, but dark colors can get warm enough in the hot sun to soften the epoxy. But most importantly, he said it doesn't provide much abrasion resistance, and doesn't make the surface much "slipperier".

I'm going to paint the hull of my new Chesapeake with Brightsides Yellow (but use varnish on the deck). One of my reasons is so the hull will be highly visible in the water when it's turned upside down. The bright color on the topsides should also make me more visible to boat traffic when I'm rightside up. My wife doesn't like bright colors, though, and is willing to sacrifice safety, so hers will be probably get painted some shade of blue.

RE: Graphite over a previously painted bottom?

I can't speak to the UV protection graphite provides to the epoxy. I have not had enough years on my kayak to make that determination. However, the abrasion resistance is superior to a paint job. IMWHO

RE: Graphite over a previously painted bottom?

If Jim Watson can be believed, the abrasion resistance of epoxy without the graphite is equally superior to a paint job. I would only worry about scratches in the paint on the bottom of the hull if the boat needed to be stored with it's bottom exposed to UV. But, in any case, I would not like to subject anything black to long term direct exposure to the sun. I am not sold on the graphite, and prefer the visibiliity of bright colors.

RE: Graphite over a previously painted bottom?

Hi guys,

I don't see any reason not to believe Mr. Watson, but first we have to be sure that we're comparing apples to apples. FWIW, I've found that the suitability of graphite/epoxy depends on 2 things - the ratios of graphite to epoxy and the kind of bottom you'll be scraping on.

I started out with a low graphite/epoxy ratio years ago (about 15/85 by volume, which is what I believe West recommends). I've now moved to 50/50. That's enough graphite that it leaves streaks if you rub against it. That amount of graphite definitely makes the surface slipperier. It also makes it softer than plain epoxy, which brings me to my next point - the kind of bottom.

If the bottom is a small scale abrasive, like sand, smooth concrete, etc., the graphite doesn't seem to make a lot of difference in my experience. However, if the bottom is mostly smooth with occasional sharp objects in it, such as oyster shells, and you skim over them, the graphite/epoxy is much superior to plain epoxy or paint. Finally, whatever the bottom, if you ground hard on it and slide along, it doesn't really make much difference which you use, you'll get gouges. Where I paddle, it's mostly mud with the occasional pebble, oyster shell or waterlogged piece of wood, so for me the 50/50 graphite/epoxy mix is a better choice.

I've finished my boats with 2-part LPU crosslinked paint (very hard coat), varnish over epoxy and surplus epoxy tankliner (even harder than LPU), so that's what I'm comparing against.

As for the sunlight softening the epoxy, I usually paddle with coaming up and the bottom underwater where there isn't that much sun :-)

Have fun all,




RE: Graphite over a previously painted bottom?

Just to make sure we leave no part of this poor horse unbeaten ...

"That's enough graphite that it leaves streaks if you rub against it." That's another thing I've heard reported about graphite bottoms that I'm not crazy about either - that they leave smudgy marks on your clothes when you lift and carry the boat. Is that what you mean, Laszlo?

On the positive side, I suppose it is a bit easier to repair gouges since there is no need for repainting. But I don't worry about touching up paint on the bottom until the paddling season is over. Nobody sees it, it's just going to get scratched again, so there's no reason to be fussy.

I guess the orginal poster didn't ask for the pros and cons of using graphite in the first place. Sorry Bill!

Cheers, Grant 

RE: Graphite over a previously painted bottom?

Hello  BP.  I guess the tread above got a bit lost in its writing.  I have epoxyed tape over paint and the physical strength of the paint was enough to hold the epoxyed tape for groundings, beachings, etc.  Of course I sanded and painted over the epoxy so you would not notice  it was there.  I am guessing that you are trying to stop bare wood from showing (as in my case) and going over the top of paint is certainly strong enough for that purpose.  Make a post if you want more  information from me or generally.

All the best and happy paddling (don't think your boat is too precious like some do)


RE: Graphite over a previously painted bottom?

Oh.  I forgot to mention.  My Chesapeake 17 is also about 10 years old.  I have repainted the hull 3 times and re-varnished the deck once (never do that as i had to scrape all the old varnish off as it was flacking).  Good on you mate, and keep paddling your 18.


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