Sheila E. Widnall - Lexington MA
William S. Widnall - Lexington MA
William E. Gorgen - Wayzata MN
Jeffrey T. Evernham - Carmel IN
Flex Foil Technology, Inc. - Lexington MA
A flexible airfoil section for a wing or a blade comprising a streamlined shape and an elastic structure whose stiffness distribution along its chord and span is tailored to provide a desirable cambered shape with proportional increases in camber with increases in lift, mounted to a supporting structure such that the airfoil sections are free to pivot about axes near their leading and trailing edges. In operation, the foil derives much of its lift from elastic bending deformation of its flexible shape, thereby achieving a higher lift than a symmetric foil at the same angle of attack while postponing the onset of flow separation and stall and, for operation in water, of ventilation and cavitation. A wing or blade of general planform comprising flexible elastic airfoil sections which can be used to stabilize, or to control the direction of travel of, as well as provide side force for, a watercraft such as a sailboat or a sailboard, or for application to a variety of aircraft components and configurations to provide lift and side force and as well can serve as the aerodynamic surfaces of various types of fluid machinery including fans, helicopter rotors and wind turbines operating in subsonic flow.