Hello Mr. Roberts

Well, that really is interesting.

Section peak lift to drag ratio occurs - just as you said - at a lift coefficient close to 1.

Then I included a term for the hull total resistance (using Dr. Norwood's estimation method) and the induced drag of the rudder (since it has finite span). The optimum lift to drag ratio for the hull and its rudder occurs when the induced drag is equal to the sum of the hull total resistance and section drag - which makes sense. The induced drag is decreasing with speed while the other drag terms are increasing so there is a local minimum in the curve of resistance versus speed when these terms are equal.

The more rudder area I gave it the lower the speed at which the optimum lift to drag ratio occurred. The lower the speed at which optimum lift to drag ratio occurred the better the optimum lift to drag ratio got.

The rudder really is working hard no matter what. The optimum lift to drag ratio for the whole boat happened when the rudder was just about to stall no matter how large I made the rudder. That happens at a lift coefficient - as you said - of about 1.

At the high angle of attack the rudders operate it is really nice they can be angled relative the hull.

Thank you for your suggestion and encouragement.
-colin pitts