What is not documented very well, or at least I am not aware of it, is how
the rudders failed.
Denise, our O'days have a 2+" stainless steel tube that runs through the rudder tube and into the rudder itself. Welded to this post should be a stainless steel frame. This assembly is sometimes referred to as a "Flag." I did some googling and found a pic to give you an idea;
Note that this pic has two shafts, because the guy built a rudder and a skeg as one unit, then cut them apart.
The flag is then set in foam to provide increased surface area. The whole thing is wrapped in Fiberglass, and that's your rudder.
There is also a good overview of the process at the Foss Foam website, here
A problem with our rudders, and I believe that this applies to most spade rudders, is that the rudder connects to the hull right at the waterline. There is a lot of stress on the rudder in this area, and the fiberglass shell therefore tends to crack right here. This, in turn allows water to enter the shell, where it sits and stagnates, and causes crevice corrosion of the stainless.
I believe that the vessels that have experienced failure, did so because of shoddy repair to a damaged rudder. Welding stainless is not the same as welding mild steel, and without using the right tools (TIG welder) and correct welding rods, what looks like a good weld will soon fail after the rudder is placed back into service.
When I pulled my rudder last year, I cleaned out a groove around the rudder post (that stainless steel tube) and filled it with 5200.
Here is a "before" picture;
The red stuff seen in this pic is not corrosion, but is actually grease.
I then dropped a HDMPE spacer on top, and allowed it to set in the 5200. I believe that the 5200 has the flexibility and the compressive strength to resist cracking, and will keep water out.
Regardless, I would either spring the $3K for a new rudder, or build my own, if I were to make an open ocean run.
I would also consider through bolting large (5") stainless washers through the rudder post to either side of my rudder to substantially "beef it up."