The glider pilot reported that before hooking-up to the tow plane he reviewed the preflight checklist and verified that the flight controls were connected and unobstructed. The initial takeoff roll was normal with the glider becoming airborne prior to the tow plane. The glider pilot applied forward stick pressure to remain in ground effect and in proper position relative to the tow plane, which was still accelerating on its takeoff roll. After the tow plane became airborne the glider began to climb above proper tow position. The glider pilot stated that he "could not push the stick all the way forward to lower the nose" and the glider continued to climb out of tow position. The glider pilot released from the towline when he no longer had the tow plane in sight. After releasing from the towline, the glider resumed a level pitch attitude and began to decelerate. The pilot selected full nose down trim, in response to his limited pitch control. The glider continued to decelerate and subsequently landed hard on the turf runway. The main landing gear and aft fuselage tubular support structure was substantially damaged during the hard landing. Both wingtips were damaged and there were several fabric tears on the left wing and fuselage. After exiting the glider, the pilot found his handheld communication radio on the cockpit floor. The pilot said that during takeoff the radio must have fallen off his seat onto the cockpit floor, restricting the movement of the control stick. The pilot reported that the accident might have been prevented if the glider had a method to secure a handheld radio and the preflight checklists included a task to identify if there were any unrestrained items in the cockpit area.