Hello Andrew,

Personally, I wouldn't bother with keel shoes. Even grounding on gravel shouldn't harm them. I won't do anything to the keels of my Coromandel until I suspect damage.

If I were wanting more protection for the keels, or were repairing existing wear, I would abrade to a rough surface underneath, and laminate on layers of glass with epoxy, shape and seal that, then prime and antifoul. But there's a healthy thickness of GRP already.

An alternative would be to shape and attach sacrificial hardwood shoes with sikaflex, then prime and antifoul. (mehitabel's rudder has one.)

A slippery plastic like nylon, I would only consider if I wanted to skid the boat around on her keels routinely. It won't glue. Drilling for attachments down there, opening holes into the encapsulated ballast... not a good idea; or if done and sealed very well, a very big job in an awkward place.

The keel-shoe question has come up in the Corribee/Coromandel Yahoo discussions, and my comments concur with others there.

Best of luck and cruising, Kurt