America's Cup 2013 two finalist hydrofoil catamarans "Oracle Team USA" and "Emirates Team New Zealand" racing neck and neck on the San Francisco Bay.
The sail of the AC72-class hydrofoil catamarans is a rigid wing made of carbon fiber. When hydro-foiling, those sailboats can go about twice as fast as the wind.
America's Cup 2013 two finalist hydrofoil catamarans racing on the San Francisco Bay.
For more info about hydrofoil sailboats, go to en.wikipedia.org/wiki/Sailing_hydrofoil.
For more info about America's Cup 72 class boats (AC72), go to en.wikipedia.org/wiki/AC72.