Rotor blade for power-generating windmill, has sinusoidal cross- section made up of two semicircles joined to each other at one edge and facing opposite ways

摘要

The rotor blade has a sinusoidal cross-section and is made of a single sheet of metal. It is designed to maximize the surface area for a given diameter and length of rotor. The sinusoidal section is made of two oppositely facing semicircles of equal diameter (D), joined at one edge. Each semicircle has a constant radius (r). The total developed width of the sheet is twice the circumference (U/2) of each semicircle.