The tug pilot released the glider from tow shortly after takeoff because the glider did not appear to be climbing. The tug pilot advised that he had lifted of at approximately 55 knots, allowed for drift, let the speed stabilise at 70 knots, then commenced to climb. After he had climbed to about 100 feet above the strip he noticed that the glider was very low behind him. He stated that he made a radio call to the glider telling him to "come up". He noticed the speed was deteriorating below 55 knots, he had full forward elevator applied and the stall warning had activated. The tug pilot considered that the glider was excessively out of station and that if the tow continued it would affect the safe operation of the tug. He therefore released the tow rope. The tug completed a circuit and landed safely. The glider pilot stated that he selected negative flap during his preparation for launch. He stated that the tug commenced its tow and lifted off after a normal ground run. The glider was skipping and not lifting off. He moved the flap back two notches, looked at the airspeed indicator and it showed around 55 knots. He stated that the "tug went up like a rocket" and climbed well above the glider. He pulled back on the control column to try to catch up with the tug. Shortly after this he heard the tow rope release. After being released he turned left, flew for a few hundred metres before turning right, and then outlanded into a small field covered in stubble. Once on the ground the glider ground looped in the stubble and slid backwards into a fence. The glider was substantially damaged. After the accident the glider was found to be configured with the flaps in the "negative flap" setting. This setting is a feature that is used to reduce drag during high speed cruise. The negative flap setting can also be used in the first segment of a takeoff roll to increase the low speed effectiveness of the ailerons. When this procedure is employed the flaps are reconfigured to the takeoff setting as soon as the wings are levelled and under positive aileron control. The continued use of the negative flap setting during takeoff and climb seriously degrades the climb performance of the glider. The pilot was not able to explain to the investigator from the Gliding Federation of Australia(GFA) why the flaps were still selected to an inappropriate setting. There is no evidence of the flaps having moved as a function of the accident sequence therefore it can be concluded that the pilot did not apply landing flap during the approach into the stubble field. It is probable that the flap setting was not changed during the takoff run. This would explain the lack of climb performance experienced during the takeoff sequence.