OK Guys all good points, however the main reason is the boards must produce lift in both directions. Starboard and port tack require the boards to lift in opposite directions. Here is a simple comparison: Consider an aerobatic aircraft. They typically run symmetric airfoils because they must fly just as well upside down as they do rightside up. A symmetric foil requires some angle of attack to produce lift, whereas a cambered or unsymmetric foil produces lift at zero angle of attack. It might be possible to have two oppositely cambered foils in each hull and raise the windward one, allowing the leeward board to do all the lifting, however a cambered board would never work on a monohull...<br><br>