Why are RC boat rudders wedge-shaped?

[Darin Jordan]

I ran flat SS 1/16 blades way back when in my SAW mono,,, the boat did not track straight with a flat blade

Yup... I found the same on my LITTLE N1-Mono, and especially on my tiny SAW 1 and 2-cell Hydros...

The Octura little wedge rudders are perfectly sized for these, but WAY too soft... Small stainless knife blades are the ticket... Drilling them, on the other hand, not so much... :)