Mahogony rudder

[Rebecca]

I have a replacement mahogany rudder, made from 2 pieces. I'd like to leave it on for the season, salt water, in its hauled up position which leaves about 5" along the length submerged. I had lots of cracking and fouling with spar varnish and have sanded it back to bare wood. My previous rudder I had encapsulated in epoxy and it did not fare well, lots of fouling. I've heard bare mahogony does well in salt water but I'm concerned that this has a glued joint. Any suggestions?

[Hirilonde]

First off, is it real Mahogany? (Swietenia) There are many reddish woods labelled Mahogany that really aren't.  What type of boat is this?  Is the rudder easily removable?  Any pictures?

 

Varnish has absolutely no anti-fouling properties, neither does epoxy. So using either as the final coat below the water line is of no value in that regard.

 

I would take the rudder off at the dock or mooring, and varnish it. (If that is an option.)  Or you could scribe the waterline with the board up, and paint the submerged part, to 2" about the water, and paint that part with anti-fouling paint, or paint the whole thing.