The pilot reported that during the takeoff roll he attempted to close a window vent and veered off the left side of the runway. He aborted the takeoff and taxied back for takeoff; he examined the airplane prior to takeoff and did not see any damage. After landing he secured the airplane in the club hangar. On August 25th during a flying club meeting the pilot observed damage to the lower section of the right wing and subsequent examination revealed substantial damage to the wing spar. The pilot reported that there were no mechanical malfunctions or anomalies with the airplane prior to the runway excursion.