The pilot and passenger were on a personal cross country flight. The pilot was taking off on a gravel runway after completing a refueling stop. According to the pilot, during the initial climb, he rolled the airplane into a left turn, but when he tried to roll out of the turn, the control stick was jammed. The airplane continued in a descending left turn and impacted the ground. Postaccident inspection of the airplane by the pilot failed to disclose any flight control system mechanical anomalies.