I've used various mix ratios, the last one being 1:1. The ones with less graphite were harder and protected better against sand. The ones with more graphite were softer, but protected better against rocks and oyster shells.

When you're using 1:10, the graphite is basically just a coloring agent and you're counting on the hardness of the epoxy layer to protect your boat. With the higher ratios you're actually making the bottom more slippery so that it slides over the rocks and shells, instead of letting them get a purchase and starting a gouge.

Two coats sounds right. Depending on the thickness of the coats, even three is reasonable.

Never heard of the hardener speeds affecting the ultimate hardness, but that could be plausible, depending on the chemistries involved. If so, it may be specific to a certain brand of epoxy/hardener.

Have fun,

Laszlo

Thanks Laszlo.  I had a feeling I could depend on your experience. Am I correct in assuming that you used Silver Tip and slow hardener for your graphite mix.

kngtut

I've used S3 Marine & fast, medium & slow, S3 Silvertip & slow and Marinepoxy & medium.

Laszlo

Two questions about the Graphite Epoxy mix.

 1) what about UV?  We varnish or paint plain epoxy to give it UV protection, does the Graphite provide UV or is this simply a case of can't paint it so have to live with it?

2) Has anyone tried this on a Skin on Frame boat?

1. The graphite provides the UV protection

2. I haven't

 Laszlo