: I would like to put a keel strip of graphite impregnated epoxy on my Coho.
: Where do I get the graphite?

You want graphite powder. It can be purchased at any boat building store and possibly a hardware store.

: What is the best mix ratio?

West System recommends a 10% weight/weight ratio, that is about one teaspoon to 5-oz of epoxy. Some folks have used as much as 25 % to get better slipping power over rocks and gravel. I plan on redoing my boat using the 25 % ratio to see how well it works.
: tape or other application tips?

Use electrical tape to mark off the area you want to apply the graphite/epoxy mix to.

: Does the graphite effect varnish adhesion?

Absolutely! Varnish will not stick to this kind of mixture. I know this from practical experience. Varnish will peel off a graphite surface almost immediately and once that starts, it only gets uglier.

: I know similar threads have been on the forum before so a reference to a past
: post would be great.

It was easier for me to restate what I know. Besides, I'm at work and all is quiet.

Robert N Pruden