While at CSR today I saw this new Bieker anti-cavitating rudder. I was told that it helped a big Perry boat, Icon I think it was, a lot. Not sure how it works. Would mean rudders must be CNC if it is a thing. I don’t know if it only works on monos or at what speed it works best. Would real fences work better? I only found this online. http://www.biekerboats.com/Bieker_Boats/Rudder_Tubercles.html
Some of the ideas for rudder and mast bumps have been tried in the 70’s by some America’s Cup designs. The inspiration is from whale flippers (humpbacks?). At the time it was found that it does help with rapid changes in velocity (don’t ask for numbers!). Overall they were discarded due to the burden in design and manufaturing processing.
Kurt:
This rudder was built by Jim Betts in Anacortes about the same time he built my mast. You can see the mast behind the rudder in the shop photo. Small world!
Alex