Discus 2b stalls after winch launch with improvised wingtip support

The pilot of a Discus 2b was seriously injured in a stall and roll-over shortly after a winch launch from grass RWY 12; aircraft destroyed. Launching solo without a wing runner, the pilot rested the right wingtip on an improvised ~50 cm folding bench, leaving the wings non-level. In a gusty east-south-easterly crosswind from the right (peaks ~33 km/h), the glider rolled right about its longitudinal axis after lift-off and, from low height, tipped over inverted ~100 m from the launch point. The probable cause was a climb attitude below stall speed, aggravated by a right-heavy tendency from the improvised wingtip support and the crosswind.

1. Winch launch from grass RWY 12: At about 10:50 local a single-seat Schempp-Hirth Discus 2b was prepared for a winch launch on grass RWY 12 at the Hoya gliding site, a 900 m by 20 m strip with grass cut to 5-8 cm. The pilot held a glider licence with an instructor rating, ~2 363 h total experience and 940 h on type, with 54 winch launches in the last 90 days. The flight was planned as a longer cross-country with ~50 L of water ballast, but no ballasting was observed and no water was found at the wreck. The winch driver was experienced and reported a normal start.
2. Gusty crosswind from the right: Surface wind at the launch was easterly at ~8-10 kt, gusty; nearby official stations recorded mean 12 kt with peaks ~18 kt (~33 km/h), direction 090-120. With RWY 12 aligned 120 degrees the crosswind component came from the right and had to be accounted for during the ground roll.
3. No wing runner; wingtip on bench: No helper was available at the launch point and the pilot decided to start without a wing runner. As a substitute for the wing holder required by the club operating procedures (and the flight manual), the right wingtip was rested on an improvised ~50 cm folding bench. The wings could not be brought level, producing a right-heavy tendency that would have had to be corrected with aileron during a brisk winch pull.
4. Right roll after lift-off: Witnesses observed the glider roll right about its longitudinal axis immediately after lift-off. Ground contact of the right wing during the ground roll, after it left the folding bench, was assessed as likely; this would have generated a strong asymmetric yaw and altered the lift distribution between the wings.
5. Stall from low climb attitude: From low height the glider entered a climb attitude in which the stall speed was undercut. Airflow over the wing separated and the glider tipped over the right wing. No technical defects of the glider or the winch were found, and no control-system anomaly was identified.
6. Inverted impact ~100 m from start: The Discus 2b struck the ground inverted, with a slight nose-down attitude, about 100 m from the launch point on a grass field beyond the southern airfield boundary. The tow cable was still attached and had not been released. The canopy was shattered and the fuselage broke in the middle. The pilot was recovered seriously injured; the glider was destroyed.