Rudder Shaft Material

hutch5151 · #1 (**permalink**) 11-03-2008

I recently discovered a crack in my rudder shaft and will need to replace it. My boat is a 1984 Kirie-Elite 37 and the original shaft is (we think) 316 stainless x 32mm. My question is what type of stainless do modern boats use for rudder shafts. Is there a better material than 316 stainless for this shaft. The material will need to be welded to the paddles inside the rudder. It appears that the failure was the result of bending loads rather than torque loads.

sailingdog · #2 (**permalink**) 11-03-2008

You might want to try one of the Aquamet alloys...which are often used for prop shafts.

Aquamet 19 or 22 are probably better choices than Aquamet 17.

RXBOT · #3 (**permalink**) 11-03-2008

Since you are welding to existing material whatever material you choose must be compatible. Probably the original material is best choice. Welding different materials togeather can be done but may require exotic rods and procedures.

ranes · #4 (**permalink**) 11-04-2008

I had my Islander 37MS rudder shaft fail this season. I am in the process of gathering information and material to build one. I think they recommend aluminum 6082 for strength, weight savings and corrosion resistance. Check out this site to read about all things rudder. Marine and Boat Rudder systems

sailingdog · #5 (**permalink**) 11-04-2008

Ranes-

You shouldn't use aluminum in any situation where it is in close proximity to stainless steel, since it will get eaten away, since it is less noble than the stainless steel. The webbing in the rudder shouldn't be aluminum either.

Rockter · #6 (**permalink**) 11-04-2008

Hutch :
Can you post a picture? I would be interested in seeing that crack in the shaft.

hutch5151 · #7 (**permalink**) 11-05-2008

Thanks to each of you for your input. In talking to the metalurgist at Western Branch Metals, we have decided to use Aqualoy 22 and increase the diameter of the shaft from 1 1/4 to 1 3/8. This will require honing out the nylon bearings in the rudder stock, but my local vendor see's no problem in performing this operation.

I had also found the information at the Jefa rudder site and had a extended conversation with Western Branch about the difference between Aqualoy 22 and Stainless 329 and 2025. They are very similar in composition, strength and corrosion resistant.

I'll post a picture of the break as soon as I get the shaft back from the vendor.