Abstract: The mixing of liquid and liquid suspensions in vessels is obtained by a mixing impeller mounted on a shaft and rotated by a drive which delivers selected speed and torque. The torque and power needed to obtain given flow is minimized by a low-cost impeller having a plurality of blades, each formed from a plate of constant thickness except for a leading edge of rounded profile. Each blade has camber which decreases from the tip to the base thereof. The base can be flat to facilitate the attachment of the blades to the shaft. The blades are oriented and twisted to be at the threshold for flow separation along the width of the blades from the leading to the trailing edge thereof, thereby providing maximum flow in the axial direction before the onset of flow separation.

Abstract: A reversible airfoil generally wing-like in shape comprising at least two spaced apart rigid spars having at least two slots therethrough, bars projecting through the slots in each rigid spar, each end of each bar attaching to a flexible slat, and a common flexible movable skin adjacent the flexible slats thereby covering same to form a reversible airfoil. A series of the rigid spars and attending parts when covered by a common flexible skin and adapted to fit on a beam provides a unique sail for a sailboat. Additionally, a series of the rigid spars and attending components when covered by a common flexible skin and vertically mounted on a rotatable frame provides a reversible lift airfoil for a wind-powered generator.