Hi Arne,
I am thinking to add end plates to the bottom of my rudder, and wondered if you had any guidelines as to their design - materials, thickness, construction, dimensions of outstand and leading tapers, etc. Part of my reasoning is that there has been some damage to the bottom of the rudder where it has made contact with something hard on the sea bed. When the boat was in Plymouth for a year it dried out twice daily against a wall, and though the rudder is shallower than the stub keel and should in theory not contact the bottom, in practice the keel would sink into the mud, the depth depending on whether it found anything hard to stop it, and so the rudder would at times be in contact with the bed. Being of GRP with a (balsa?) core the lower edges have been worn away locally, and there is a danger of water entering the core. I thought to get a "shoe" of stainless steel plate made to a) protect the GRP of the rudder, and b) take the form of an end plate to improve rudder action.
Any comments from anyone appreciated.