GasTurbine, on this test, what where the water conditions? Did you test the 40mph boat with the rudder first, and then without? Also, on the 120mph boat, what were the conditions, and how did you conduct this test? If it was at a drag racing event, what was the reaction, ET, and MPH of both passes?
I'm not saying you didn't do these tests, but I am saying just be removing the rudder you are not going to notice a difference in MPH. Now, like you posted, if you add a Large rudder to your 120mph boat there was a 4mph drop in speed. One question, why would you have a Large rudder on a boat like that anyway?
I'm not trying to start anything with you, I just think your results have another variable in the equation which you didn't account for and I don't want everyone thinking there rudder creates so much drag to where they would notice a difference in top speed if it was removed.
HBjet