Any ideas on the rudder foil?

The bottom of the rudder is angled backwards slightly (so if a plate was put on the back it would pull the back down).

Should I just glue a bit of plywood to the bottom so t looks like the attached image of the black boat? (obviously on my rudder sketch, the angle has been emphisised.

Does the foil have to be an areofoil? If so, can someone draw me a crosssection?

Many thanks,

Andrew

Many thanks,


Andrew