| 摘要 |
To reduce drag in a lightweight windmill, a vertical centrally located frame has three vertical windmill-vane arrays extending radially outward therefrom spaced circumferentially 120 degrees from each other about the rotatable framework. Each vane array includes a plurality of flat flexible sails rigged one under the other between leading and trailing horizontal arms in the array with an upper leading edge of each sail being directly fastened to a different one of the leading arms and a lower edge of each sail being fastened by flexible cords to a different one of the trailing arms so that when the wind blows in the direction of the leading arm, the sail billows outwardly to turn the framework but when the wind blows in the opposite direction the sails are lifted flat to provide low drag. In one embodiment, the arms are cables, stretched radially from the central vertical framework by other cables so that the entire structure is easily disassembled for shipment. The structure is made of hollow aluminum tubes, cords and fabric sails so as to be lightweight and efficient.
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