Re: rebuilding a rudder and boom question
I'd use epoxy resins rather than polyster, esp if you're not going to use real marine ply for the rudder... and then simply paint it with a decent paint once you've removed the post-cure amine blush.. Epoxy is more water resistant than polyester resin, esp in thin layers.
I wouldn't try to 'gel coat' a wooden boom.. just paint it - you'll be needing to touch it up periodically anyway, so why make it complicated? Or leave it natural/varnished/cetol'ed or whatever...
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
1984 Fast/Nicholson 345 "FastForward"