Rewording of Rule 17

17. Hydrofoils are not permitted. Atleast one hull shall be in the water while sailing. To this end, centreboards and rudders are to be essentially straight with a maximum camber (top to bottom) of no more than 25mm. They are to be essentially vertical with the distance between the bottom of the boards, when both are deployed, within 100mm of the distance between the top of the boards in the same position.

Diagrams required.

A bit wordy but should avoid any confusion.