It appears from the photo you supplied that part of the problem is that you did not bury the hinge deep enough into the rudder to attain the scale like movement of the rudder that is intended.

It looks like the pivot point of the hinge is even with the leading edge of the rudder. This would be fine if the leading edge of the rudder was simply beveled. Since it is a half circle, the hinge pivot point must be behind the leading edge at what would be the center of the circle.