I don't think it's fair to make the 18 on this video represent foiling boats as they obviously had not worked out efficient foiling technique yet (like the guy who has to run forward to the bow every time they get foiling). Obviously foiling will decrease dramatically wetted surface, which is the biggest aspect in terms of friction forces on boats. So theoretically a foiling cat should be faster than a non foiling cat (duh:)). How much is yet to see, I will hopefully do some study on exactly this kind of stuff when I finish my Master degree in Marine Technology some five years from now:) However, foils sure made the Moths faster...