Design diameter of Rudder stock

Guys, I'm in a learning cycle of the rudder and rudder stock design. I used the rule books and various empirical formula to find out the required rudder area, and accordingly rudder torque. I have developed 3 designs for the rudder with NACA series 0010, 0012, and 0015. I need to finalize the series before which I need to calculate the rudder stock diameter. Can anybody tell me an idea how I could go forward.

 

You already know the torque, so look up the strength of shaft material on manufacturer's site. As a practical matter, how large of a diameter can you fit in your foil? Not strong enough? ...then get a different material. Do check out http://www.jefa.com/products/materials.htm How are you making the rudders?

 

oh ya, why din my brain think in dat way.. thanks mate....