A kite having separate forward and aft sails, each arched about a common longitudinal kite axis and each sail disposed concave downward in flight. The concave shape of the sail funnels the wind through the kite. Lift is derived from the central portions of the sail while the lateral portions of the sail,...http://www.google.com/patents/US4018408?utm_source=gb-gplus-sharePatent US4018408 - Concave parabolic arch kite
