Black Gel Coat for a keel strip

I’m getting ready to apply a keel strip to my five year old Explorer (standard Diolene construction) and following this article printed in Sea Kayaker a few years ago:

I haven’t done much fiberglass work but know how critically things need to be measured, and the small repair I just did came out great. The article recommends 2:1 gel coat to resin mixture with microballoons added to thicken it. I have white gel coat (gel and resin are both polyester) and want to make it black, so I also bought two ounces of black pigment.

I need about 16 ounces total of this mixture, but my question is about the pigment. Can anyone tell me if they think two ounces of pigment is enough? I called the supplier (Jamestown) and they said there really isn’t a rule about how much would be needed. I don’t want to end up with grey…

not an answer
to your question, but consider that black gelcoat over white on the keel strip might look like like crap once you start wearing into it.

While racing stripes look cool, I think a light color will look better in the long run.

Fumed silica
Microballoons lighten the resin as well as thicken it. Fumed silica also thickens, and makes it tougher as well.

I have a white keel strip and a clear one on my Caribou. Both have lasted years with just epoxy and silica as the main ingredients. If you want a black strip, use graphite powder, and your strip will have much higher abrasion resistance.

Surface prep is 90% of the battle. Wash with acetone, sand, mask, and apply. It’s not hard. If you can fix fiberglass, you can easily do this.


am a fan of fumed silica, it gives it a great deal of rigidity.

Thanks for all the advice. They did have clear (unpigmented) gel coat but I figured I’d get white so I could also touch up a couple minor spots on the hull too. Black pigment is just a pigment and if it doesn’t add strength to the gel/resin mixture then that probably means that adding a bunch will take some strength away.

I guess I’ll stick with a white keel strip. Well, I suppose I could mix in some metal flake… Probably not!

fiberglass tape with graphite ‘pigmented’ epoxy …

With the graphite you can get the gelcoat pretty dark, especially if you keep loading it before going with your choice of thickener … much better than those pigment tubes which inhibit full cure.

Really should use resin though … if you want any of it to stay on an already well used / worn surface, you gotta prep ( sand ) real well.