Geoff,
Thanks for info - I'm surprised that 10mm PVC is stronger that ply. Did the ply blade break across the pivot hole? How far did the blade extend? We leave about a foot of keel down, so I was thinking that a blade extending to match this depth below the hull would be about right i.e. probably about 2 feet in the water.
How do you stop the blade dropping down when not in use? Is the pivot nut sufficiently tight to prevent this?
I know that boats with rudders that lift vertically use a shorter stub rudder when on a drying mooring. I thought that I might try to contrive something similar for the 235 by attaching some slides on one side of the stainless steel rudder housing but this is still at the "idea" stage pending some inspiration on how to attach the guides to the rudder box and also making them stand off sufficiently so that the stub rudder clears the pivot nut. I don't think slotting the stub to clear the nut would be very strong or hydro-dynamically efficient!
Chris Cobb
235/48 "Tarakihi"