On December 3, 2005, about 1600 Pacific standard time, a Diamond Aircraft Industries HK 36 TTC, N543MD powered glider, registered to and operated by the pilot as a 14 CFR Part 91 instructional flight, collided with a tractor during takeoff from a private airstrip near Sandpoint, Idaho. Visual meteorological conditions prevailed at the time and no flight plan was filed. The glider was substantially damaged and the private pilot owner and flight instructor were not injured. The flight departed from Sandpoint Airport about 30 minutes prior to the accident. During a telephone interview and subsequent written statement, the pilot stated that they had been practicing short field approaches at the Sandpoint Airport, then decided to go to the owner's property where he had a private airstrip. The pilot stated that the flight instructor was flying the glider, making a low approach over the airstrip when he unexpectedly decided to land. The airspeed was too high to stop on the remaining runway which was covered with compacted snow. After rolling about 300 feet, the flight instructor applied full throttle for the takeoff. The pilot pointed out the power lines beyond the end of the runway, and the flight instructor stated that they would fly under them. At this time the left wing struck a tractor that was positioned at the end of the airstrip. The wing separated from the airframe and the glider spun around, coming to rest. The pilot stated that there was no mechanical failure or malfunction with the glider at the time of the accident.