After travelling 15 metres during a winch-launch the left wing-tip contacted the ground. The instructor immediately assumed control of the glider and applied right rudder and aileron but the left wing entered an oat crop on the edge of the strip. The tip then dug into soft soil, causing the glider to cartwheel and impact heavily on its nose 120 metres from the take-off position and 35 metres to the left of the centreline. The crop on the edge of the 15 metre wide strip was about 1 metre high and the glider's wing span was 17.5 metres. The student was experiencing difficulty learning to control the aircraft during take-off and following wing-tip contact with the ground both the instructor and the student stated that they made control inputs. Conditions during the day were hot and the instructor had been on duty for nearly ten and half hours.