fibreglass ruder how many layers & wood spar or not?

[danielfarley 0]

Hi guys need to make a new rudder for my boat, she's a trojan 750 (25 foot trailer sailor). I am planing on making a foam core, following a NACA0012 profile. The ruder (bit in the water) will be the same as the old broken one in size which is 1m x 0.35m.

 

The plan at the moment is hot wire cut Extruded Polystyrene foam, and layup some uni and bi glass on top of it.. and a top coat of just woven cloth, fill, sand and paint.

 

I am also considering putting in a hard wood spar that runs 70% of the way to the bottom, and perhaps even wrapping this is uni carbon or glass.

 

Can someone give me a rule of thumb calculation for what weight and number of sheets of glass at what angle you would wrap a ruder for this sized boat in... with out with out the wooden spar??

 

 

Thanks D