On July 18, 1995, at 1340 central daylight time, a Reed RS15 glider, N964, was destroyed while taking off from Ames Municipal Airport, Ames, Iowa. The tow airplane, a Piper PA-25-150, N6084Z, operated by Silent Knights, Inc., of Ames, Iowa, was also destroyed. The pilot of the glider received serious injuries and the pilot of the tow airplane received minor injuries. The local 14 CFR Part 91 flights operated in visual meteorological conditions. In a detailed written statement, the pilot of the glider outlined the preflight procedure he followed in order to prepare the glider for the launch. After towing the glider to the takeoff area, the pilot stated that he unhitched the glider, adjusted the auxiliary balancing weight which is calculated for his weight, and tightened the retainer bolts. Next the pilot stated that he deployed the ruddervators to their normal "V" configuration and locked them into position. The pilot stated, "I tested each ruddervator with vertical (up and down) hand pressure." He then stated that he checked the overall condition of the glider and installed the battery power source. After the preflight was accomplished, the pilot secured himself in the glider as the tow rope was connected to the glider. The pilot stated that he does not remember any of the events that followed concerning the takeoff roll or accident. The pilot of the tow airplane reported that the glider was hooked up to his tow airplane and the ground crew gave him the departure signal to begin the takeoff roll. The pilot stated, "the towplane, although being somewhat pulled sidewise, lifted off and established normal climb." At approximately 50 to 60 feet above the ground, the pilot stated that the tow airplane experienced an extreme drag which pulled the airplane's tail down despite his use of full forward elevator. At this time, a severe jerk caused the tow rope to break near the attachment point on the tow airplane. The pilot stated the airplane stalled and then impacted the ground. Both the tow airplane and the glider came to rest approximately 300 feet from the end of the runway. One witness stated, "as the takeoff roll proceeded down the runway it was evident that the glider was having difficulty maintaining control." The witness stated that the glider "fish- tailed" and its wings never became level. The witness observed the tow airplane lift off and climb to an altitude of approximately 75 to 100 feet above the ground while the glider remained on the ground. The witness stated that the tow airplane appeared to stall and it then impacted the ground as the glider cartwheeled and flipped over. Another witness stated he observed a normal start in the tow operation but stated that the glider was having difficulty in maintaining directional control. The witness stated that the tow airplane lifted off as the glider stayed on the ground. "This appeared to pull the tail of the towplane down pitching the nose up into a stall configuration. This caused a full stall at low altitude and a loss of control and the accident," the witness stated. Postaccident inspection of the glider revealed the right ruddervator was loose and was not properly connected to the push- pull tube. During this inspection, the ruddervator was tested to determine if it would operate as designed. It was found to function properly once the ruddervator connection was engaged into the push-pull tube and the locking pin was engaged properly. During a telephone interview, the pilot of the glider stated he did not remember if he had done a positive control check of the ruddervators prior to the takeoff roll, but he stated that he probably did not. He only recalls doing an external check and then remembers climbing into the cockpit and wiggling the stick to verify control. The pilot stated that he has learned his lesson from this accident, and a positive control check is now a mandatory part of his preflight. A witness did observe the glider pilot climb into the glider's cockpit and work the control stick to verify aileron and ruddervator control during his preflight. But the witness stated that the pilot did not do a positive control check.