On August 18, 2010, about 1015 Pacific daylight time, an Ercoupe 415C, N2368H, collided with trees during takeoff from Lake Wenatchee State Airport, Leavenworth, Washington. The pilot/owner was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The private pilot and one passenger sustained serious injuries. The airplane sustained substantial damage to the wings and fuselage from impact forces. The cross-country personal flight was en route to Auburn, Washington. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot reported that he made a short field takeoff to the west with an approximate 5-mile-per-hour (mph) headwind. Shortly after liftoff, he realized that the airplane would have difficulty clearing trees at the end of the runway, and considered aborting the takeoff. However, he decided that not enough runway length remained to do so, and continued the takeoff and climb at what he believed was the best angle of climb speed. The airplane did not stall, but the pilot stated that the speed might have gotten below the best angle of climb speed. He turned the airplane slightly to the right, but the airplane collided with the top 10 feet of trees surrounding the airport. The pilot stated that he lost consciousness, and his legs were numb when he awoke. The passenger was able to evacuate herself from the airplane, and called for emergency service. The pilot stated that, in retrospect, he might have taken off downwind to the east where there was more room, used a different airport, or maintained a faster airspeed. The pilot also reported no mechanical failures or malfunctions with the airplane at the time of the accident. A witness, who held a pilot certificate, but had not flown for 30 years, stated that he drove the pilot and passenger to the airplane. He observed the pilot taxi the airplane to the end of the runway, and perform a run up. The engine sounded fine and smooth. The airplane taxied into position on runway 27, and the airplane appeared to stay stationary as the pilot added power. The airplane then started forward. The witness noted that while the airplane taxied to the runway, there was no wind. During the takeoff, he noted a very slight crosswind. The turf field appeared to be bumpy, and the airplane kicked up dirt as it progressed down the runway. The takeoff roll was longer than he expected. After liftoff, the airplane did not appear to be climbing, and drifted to the right while remaining in a wings level attitude. There were no sudden movements, and it started a shallow climb. He lost sight of the airplane behind trees, and heard a loud sound about 2 seconds later. He did not have the impression that the airplane had engine issues, or stalled after getting airborne. When the witness arrived at the wreckage, the passenger was standing beside the airplane. He instructed the pilot to turn off the ignition switch.