When the aircraft had reached a height of about 300 feet agl the winch motor lost power. The pilot released the launch cable and attempted to land straight ahead but the aircraft overshot the end of the landing area and collided with trees. It was considered that at the time of the winch failure, sufficient strip length remained to permit the aircraft to land safely. However, the pilot had not deployed the dive brakes early enough to prevent the overshoot. The reason for the loss of power from the winch motor was not established, and subsequent operations were reported to be normal. This accident was not the subject of an on-scene investigation.