Vasek,

Not sure what to tell you about the curved rudder (perhaps just build a new one?) but I normally laminate a piece of C/F in between the TE sheeting to get a sharp, strong, & straight surface. I've also used a dremel tool mounted in a dremel drill press attachment with a saw blade (or cutoff wheel if you want a thicker slot) to slot the TE 1/8" deep & then insert the C/F or 1/32" ply piece. That'll allow you to sand the TE down to a sharp edge.

Bob