I am just about ready to put the final two coats of epoxy on the exterior of the hull of my new boat, a pretty cool double paddle canoe designed using Gregg Carlson's Hulls 2 software. I wouldn't mind a little more abrasion resistance on the very bottom than plain epoxy. I've used graphite on another boat and didn't like it. The graphite is pretty ugly, didn't seem to harden the surface much and increases heat absorption. In the current issue of "Boatbuilder" an epoxy supplier suggests a kevlar reinforced epoxy putty and sand, neither of which sound like good ideas to me. I would think the putty would add excess weight and the sand would be rough, thus slowing the boat.

I've used silica in epoxy for fillets and glueing. As others have mentioned, it gets very hard and is a bear to sand. Given those properties, I wonder how adding a small amount of silica to the epoxy would work (below waterline only, I want the rest bright and clear). Has anyone tried this and, if so, what ratio of silica to epoxy would be appropriate?

Thanks for your help.

Chris Luneski