SWEPT WING VARIABLE PITCH SAILPLANE
Document Type and Number: United States Patent 3561702
Link to this page:
http://www.freepatentsonline.com/3561702.html
Abstract: A sailplane is provided in which the line-of-lift of the wing is swept back from the longitudinal elastic axis to give an automatic wing twist with change of lifting force. In operation, a reduction in the angle of incidence from an updraught wind results in a trade of lift for greater forward thrust. An increase in angle of incidence from a downdraught wind results in a trade of forward momentum for greater lift. This is most effective under turbulent air conditions.
...is the bit that I've highlighted in bold type true?