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Re: Strip: Building Bjorn Thomasson's Frej

I have used graphite mixed in epoxy on the bottom of two S&G kayak to give a more durable finish, and toyed with the idea of a black "graphite" hull. Do you know of some data comparing scratch or dent resistance of finishes having different compounds mixed in epoxy?

If you found that graphite gave a more durable finish on your S&G kayaks, yo already have a couple of data points....
I can't answer your question with any real 'data', but I have a few thoughts/opinions/experiences:

1)I've found graphite + epoxy is quite soft (easy to sand into a black dust cloud....)-softer than straight epoxy. The idea of adding graphite to epoxy was developed by the Gougeons (WEST Epoxy) for making low-speed pour-in-place bearings for things like sailboat rudder stocks, as I recall.

2) The 'usual' hull coating is epoxy+graphite+silica (fumed silica aka Cabosil aka 'NoSag'). Graphite for black, silica for hardness. An experiment sanding silica-loaded epoxy will give you an idea of that. I've always found that graphite is more of a dark grey than jet-black color, but it may be the stuff (WEST) I was using.

For sliding off rocks and barnacles, I'm looking for the hardest surface I can easily get, so lots of silica is one way to try for that. The iron oxide is gritty and 'hard' and I don't need a great deal to get a black color, so I can use more silica in the mix.
I've been impressed with how tough the hull on my 'BritBoat' project has turned out to be. It's 6oz glass filled/faired with a good layer of black silica epoxy, coated with 2-part black polyurethane paint (Interlux perfection). So far, so good.....

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Strip: Building Bjorn Thomasson's Frej *PIC*
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Re: Strip: Building Bjorn Thomasson's Frej
Re: Strip: Building Bjorn Thomasson's Frej *PIC*
Re: Strip: Building Bjorn Thomasson's Frej *PIC*
Re: Strip: Building Bjorn Thomasson's Frej *PIC*
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Re: Strip: Building Bjorn Thomasson's Frej *PIC*
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Re: Strip: Building Bjorn Thomasson's Frej *PIC*
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Re: Strip: Building Bjorn Thomasson's Frej
Re: Strip: Building Bjorn Thomasson's Frej *PIC*
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Re: Strip: Building Bjorn Thomasson's Frej *PIC*
Re: Strip: Building Bjorn Thomasson's Frej *PIC*
Re: Strip: Building Bjorn Thomasson's Frej
Re: Strip: Building Bjorn Thomasson's Frej *PIC*
Re: Strip: Building Bjorn Thomasson's Frej *PIC*
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Re: Strip: Building Bjorn Thomasson's Frej