I don't think copper alone will stop slime. The newer paints have
extra "anti-slime" additives. I was talking to a guy who has a
power boat with Coppercoat on it and for the first few miles of
motoring he can see the slime falling off as he leaves the marina.
I have no idea if a sailboat would go fast enough for this but I
suspect not.
I met a guy who made his own copper powder/epoxy and tried it on the
rudder of his trimaran. He said it worked but he had to dive down
once in awhile to give it a light sand in order to expose new
copper. I think the challenge is to get an epoxy that will slowly
erode/wear and expose new copper and some epoxies are better for
this than others.
Paul