On October 8, 2004, approximately 1500 mountain daylight time, a Schweizer SGS 1-26E glider, N17911, was substantially damaged during a collision with a tree while executing an off-airport landing near El Paso, Texas. The private pilot, sole occupant, sustained serious injuries. The airplane was registered to and operated by the pilot. Visual meteorological conditions prevailed and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The local flight originated from the Horizon Airport, near El Paso, Texas, at approximately 1300. According to the 650-hour pilot, while soaring near El Paso, Texas, the thermal conditions became weak and the glider began to lose altitude. The pilot reported that with a landing becoming imminent, he elected to land at a new housing development under construction. The pilot further reported that during the landing roll, the glider bounced over a street curb and the right outboard wing contacted a small tree. The glider came to rest in an upright position. According to a Federal Aviation Administration (FAA) inspector, who inspected the glider, the right wing sustained structural damage. Despite several attempts by the Investigator-In-Charge to obtain a completed Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) from the pilot, one was not obtained.