Patent ID: 7040940

Claim:
A rotatable lifting surface device, comprising a hub and a plurality of blades extending therefrom, wherein a blade is formed of a material that is flexible, has a pitch distribution across a span of the blade, and has a camber profile at at least one radial station of the blade such that the blade is loadable toward a trailing edge of the blade and that the blade is deflectable from a first position in which a load on the device is low and the pitch distribution is a first pitch distribution, such that a pitch of the blade increases from the hub to a tip of the blade, to a second position in which the load on the device is an intended load and the pitch distribution is a second pitch distribution different from the first pitch distribution, and the camber profile has its maximum camber nearer the trailing edge of the blade at a chord-line position that is at least about sixty percent of a chord length at substantially all radial stations of the blade.