I am in the process of making my own after the rudder was lost by the PO.
First thing I learned was single screw rudders and twin screw rudders are not the same!
My boat has a single screw. When I was searching, I found lots of twin screw rudders but they were tiny and not adequate nor robust enough for a single screw.
I decided to make my own.
My problem was the shaft was broken. It was a two-piece shaft that was bolted together through mating flanges. The rudder was lost when the upper flange departed from the upper shaft. Poor weld was the root cause.
With only the stub of the top-half of the shaft, making a new lower was going to be impossible
I ordered a stainless shaft 1-3/4" diameter that would run the entire length of the rudder.
For the rudder itself I have measured the rudder of several similar size single-screw boats that were in the boat-yard (I did it this fall when many boats were being pulled out for the winter season (Canada, Lake Ontario) In my case, the rudder for my size trawler seems to be about 18" long by 22-24" high (36' trawler)
With dimensions in hand, I ordered a stainless sheet steel that I would fold into an airfoil shaped rudder that would bolt onto the shaft along the 24" length.
Anyway, that's how I am solving my rudder problem. It may not work for you, but hopefully it gave you some ideas.
