: 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

Chris I can tell you how some products worked against abrassion resistance when I was pattern making that were pretty amazing. The mold making department had a problem with nozzles wearing out on a giant planner that suck up iron shaving 24 hours a day and they wanted us to rig something up. We made a nozzel head cast onto a 2" steel pipe out of a black casting epoxy and this would last about a week. Then we tried a blue epoxy surfice coat that had tungston in it that was so tough that you would round a drill bit over the first time you drilled into it. This nozzel plastic lasted about a month. Then we tried a two part polyurethane that was flexable but stiff. This never wore out, only the steel pipes would wear through and we would then have to make a new nozzel in about 6 months. The blue epoxy would be almost impossible to sand and shape but would never wear through in a tough boat area and the draw back on the Polyurethane is that it can be sliced with a knife but would last a lifetime against sand and rocks. These are just thoughts if anyone wants to do some experimenting.

John