You’re not going to win America’s Cup 34 without sexy foils to keep the leeward bow floating, or flying, high. This is an area of development just as important as wings for the next generation of Cup-hopeful catamarans, and all eyes were on Emirates Team New Zealand when their flaming red AC72 hit the water ahead of other teams. She looks wild, but this particular 72-foot, wing-sailed beast is presumably the conservative sister of something even more “playful” to come.
The foils displayed on ETNZ 1.0 for her first excursions were S-curved, with L-turned lower sections reminiscent of the experimental foils long-since exposed on Oracle Team USA’s AC45s. (Nonstandard foils can be tested, but not raced, in AC45s.)
A straight foil is all about countering leeway. Curved foils might compromise that function, but contribute hugely to lift, whether they are C-shaped, S-shaped, L-shaped or mixed. With aerodynamic crossmembers and subtly canted hulls and rudders, all parts work together.
The AC72 class rule prohibits the trimmable rudder winglets that would be the obvious pitch-control mechanism for lifting the entire leeward hull out of the water, but fixed rudder winglets are popping up everywhere in experiments, and speculation is rife about alternate pitch-control points.
Photo courtesy of 34th American's Cup