What to coat a wood rudder with?

I build a sailboat called the "Point Jude" which originally was built in wood, and now glass. See www.pointjude.com. I need some assistance on the rudder, which is built of wood. The top part of the rudder is built in two outer pieces of marine ply sandwiching a piece of mahogany. The previous builder was only varnishing the wood, and as a result, the plywood on some rudders is falling apart. I want to build a better rudder and I need some help in determining what epoxy I should use, if it makes sense to put a layer of fiberglass cloth on the plywood, and if it should be varnished after the epoxy has cured.

Thanks for the help.

 

Glass away

Yes, you will get a better job by glassing the timber.
Make sure it is dry, 80 grit sanded and cure your epoxy glass sheath at a minimum of 20 degrees C.
Dont know what brand of epoxy is available around your joint but 105 West Epoxy is fine. Epoxy has no UV protection so you are better to paint, or at least use a good UV resistant 2 pack varnish and keep in a cover if possible. Plywood is a poor timber to epoxy coat so you may have to pre-do your end grain a few times first to stop the edges soaking up all the resin in the one shot method. If you know anything about peel ply, use this over the wet glass cloth and resin.