On August 4, 2000, about 0900 Pacific daylight time, a Piper PA-30, N300RE, veered off the runway and collided with a runway light during takeoff from Yolo County Airport, Davis, California. Travis Air Force Base USAF Aero Club was operating the airplane under the provisions of 14 CFR Part 91. The certified flight instructor (CFI) and the commercial rated multiengine student were not injured; the airplane sustained substantial damage. The instructional flight departed the private Travis AFB Aero Club airport about 0830. Day visual meteorological conditions prevailed, and no flight plan had been filed. In a written statement given by the CFI, he stated that he explained to his student that he would be simulating an engine failure on the takeoff roll and proceeded to retard the right throttle. The airplane started to drift to the right and the CFI said he felt the distinct application of left rudder. As the CFI waited for his student to apply the proper correction procedures, the airplane continued to drift to the right side of the runway. The CFI pulled both throttles but realized at that point that he did not have any brakes on his side of the airplane. He increased the throttles and the airplane "violently swerved" and rolled to the left as it became airborne. As the airplane drifted down the runway in ground effect, the CFI regained control and continued the departure. The CFI and student continued back around to practice another stop-and-go landing. During the taxi back for takeoff they noticed "something shiny" on the side of the runway. The CFI noticed the left wing tip was missing. The CFI then took control of the airplane and flew it back to Travis AFB Aero Club airport. The pilot and operator submitted written statements, but did not submit an NTSB 6120.1/2 pilot/operator report.