After reaching a height of about 200 feet agl on a winch launch, the glider was observed to enter a shallow dive. The drogue parachute was seen to inflate above the inboard section of the left wing and then trail behind the glider with the tow wire draped over the top of the wing. The glider entered a left turn which developed into a spiral dive. Partial recovery was effected but the aircraft impacted the ground in a nose-down attitude. The pilot was relatively inexperienced and was performing his fourth solo winch launch. During the launch the aircraft exceeded the climb speed limit and the pilot atempted to signal this fact to the winch operator by the normal method, which involves lowering the nose of the aircraft prior to yawing it from side to side. However, the pitch change used was larger than normal, unloading the tow cable and resulting in a "back release". The length of cable between the attachment ring and the drogue parachute was considerably shorter than that recommended and increased the probability of an uncommanded release of the tow cable.