Uh oh...my emergency aerodynamics intervention may have come too late.
A generous round over on the leading edge of the rudder is a good idea. It will enable the flow at the leading edge (which is coming off the keel) to attach cleanly to the rudder.
The trailing edge is a different story. You want those corners to be as sharp as possible. This may be counter-intuitive to armchair aerodynamicists, but it is true. With a sharp corner, the flow coming off the trailing edge will always (assuming the rudder isn't stallled) separate at that sharp corner, even when the rudder is deflected. Yeah there is a small amount of drag due to the little bubble of separation due to the blunt trailing edge, though it isn't as bad as you might think...but I won't go into details on that.
With rounded corners, there isn't a fixed separation point, so the flow may stay attached a little longer in absolutely perfect conditions, but instead it will tend to wander around and the flow will basically end up unzipping way forward of where the sharp corner would have been. So now there's a bigger bubble of seperation behind the rudder, and thus more drag. And it gets worse when you deflect the rudder, because that seperation point is now going to be really happy to move forward, and all that area behind the seperation point isn't going to contribute a wooden nickel to your rudder effectiveness. So, now you've got more drag and less rudder effectiveness. Bummer.
That being said, the magnitude of the degradation that we're talking about isn't such that it would make the rudder useless or anything. Even sailing a sharp corner rudder and a 1/2" round-over rudder back-to-back probably won't yield a perceptible difference. But it'll be there just the same.
![20141029_210806_resized_1.jpg](./download/file.php?id=452&sid=0f04746a69491f5b2cad309343dc1b59)
- 20141029_210806_resized_1.jpg (88.59 KiB) Viewed 10917 times
![20141029_210734_resized.jpg](./download/file.php?id=451&sid=0f04746a69491f5b2cad309343dc1b59)
- 20141029_210734_resized.jpg (85.13 KiB) Viewed 10885 times