Reportedly, after waiting almost 2 hrs, the plt decided he would fly the sailplane, either for 1 hr or until the owner arrived. When the owner arrived, he observed the sailplane flying back & forth along the north side of ridge area. Subsequently, the acft crashed in a wooded area on the downwind side of a ridge that sloped downward to the north at about a 30 deg angle. Although there were no known witnesses, the owner saw the sailplane disappear behind a ridge in the vicinity of the accident side. During impact, the sailplane struck a tree, aprx 12 ft tall, & broke it in half. It came to rest on trees & brush with extensive damage to the nose & cockpit areas. No preimpact malfunction or failure of the sailplane was found. The crash site was located in an area known to have periods of high sink. The plt was a naval aviator with only about 3.4 hrs flt time in this make & model.