Incident Overview
A glider pilot reported that while returning to the airport after approximately three hours of soaring, the glider encountered a sink. The aircraft descended 2,500 feet before the pilot found a more favorable air mass. At that point, the glider was too low to reach the airport, and the pilot chose to land in a field.
Approach and Landing
On final approach, the pilot observed that the field had deep ruts. However, he was committed to landing. During the landing roll, the left wing contacted a rut, causing the glider to ground-loop. The ground-loop resulted in partial separation of the tailboom.
Mechanical Condition
The pilot reported no preimpact mechanical malfunctions with the glider.