Anybody got a copy of ISAF Equipment Rules for sailing?

Look up hydrofoil.

Then look up daggerboard and rudder.

I dont have the document, but as it was just explained to its all defined. Daggerboard is defined as being near the centerline of the hull. Hydrofoil is "not near" the centerline of the hull. Rudder is what you would expect.

So Wouter's interpretation of hydrofoil being a "waterborne foil" and Luiz's assertion that "all foils generate lift" are not valid for the sake of this argument. What matters is the ISAF definition.

So if your daggerboard is not in line with the centerline of the hull, it's a hydrofoil according to ISAF's equipement rules of sailing. The ISAF's definitions are what the measurers use, so its that definition that matters.

Under this definition, any boat with a board that is not in line with the centerline of the hull is not an Acat and cant compete. There are boats competing today that are outside this rule, its just not been enforced.