During the last time when I took the boat out of the water, I noticed that water had accumulated in the rudde, this happens every year when taking the boat out of the water, I drilled a hole in the bottom of rudder, drained the water, waited two days, plugged the hole with epoxy putty and that's it, because I didn't have time for a complete solution.
This year I would prepare, and coat the entire surface of the rudder with something or laminate it with glass canvas.
What you think, is this will solve it?