Hans,

You would be referring to an A Class? There are several issues in using the A class as a basis for foil testing: With the class rules restricting the curvature of the boards and also the fact that the righting moment is reduced with curved boards (A Class is already narrow for its length) plus the fact that the A Class is not adding any sail area downwind. all these factors reduce the impact of the foils in a performance test.

We did many hours testing with identical platforms and changed only the foils. The results were conclusive: Curved foils were always better on a 2 person, 3 sailed boat with a wider ratio to length than an A class.