The pilot had hired the aircraft to fly to Piper's Field with three friends for the day. He was familiar with the strip which is used for glider operations. On arrival in the circuit area, the pilot contacted the local gliding club by radio and was advised that gliders were landing and taking off in a southerly direction. The strip, 686 metres in length, has a one percent average down slope to the south. The wind velocity was reported as 200 degrees at 10 knots. The pilot reported that the aircraft encountered sink on final approach and that he applied power to counteract the sink. The aircraft touched down well into the strip and bounced. The second touchdown was about halfway along the strip and the pilot was unable to stop the aircraft before it overran the strip. The aircraft was damaged when it ran through a ditch which was concealed by long grass.