During flight, the glider sustained an in-flight failure of both wings, then entered an uncontrolled descent and crashed. An exam of the wreckage revealed no preexisting structural problems. The glider was equipped with a recording barograph. A barograph trace showed that the glider had been airborne about 45 minutes and had step climbed to 16,500 ft. During the last 5 minutes it had descended 500 ft and climbed 250 ft, then entered a rapid descent (straight line on the recording) and crashed. Other glider pilots reported that N71W was flying in the vicinity of lenticular clouds with bases between 14,000 and 18,000 ft. They reported "mild wave conditions" with no unusually strong rotor. One pilot noted a phenomenon of "lenticular jump," in which the cloud could grow faster than a glider could move away. N17W was not equipped for instrument flight and did not have an oxygen system installed. The pilot was diabetic, but a flight surgeon's findings concerning his medical condition at the time of the accident were inconclusive.