a fixed pitch, and use two strings, one on each side of the kite, to change the roll. Rogallo also developed a series of soft foil designs in the 1960s which have been modified for traction kiting. These are double keel designs with conic wings and a multiple attachment bridle which can be used with either dual line or quad line controls. They have excellent pull, but suffer from a smaller window than more modern traction designs. Normally the #5 and #9 alternatives are used. Early Rogallo patents Despite similar designs having appeared earlier and critical innovations such as the triangular control frame and harness for adequate weight-shift control having been developed by others, Rogallo holds several patents. Rogallo, Gertrude et al., "Flexible Kite", US patent 2,546,078, Filed November 23, 1948 Rogallo, Gertrude et al., "Flexible Kite", US patent 2,751,172, Filed November 17, 1952 See also Flight Dynamics Flightsail Hang gliding History of hang gliding Paragliding Wing References External links Sled kites at the Virtual Kite Zoo. Rogallo wing and kites. Landing Gemini Losing Rogallo from Gemini Rogallo After Gemini American inventions Kites Aircraft wing design Hang gliding Gliding in the United States