According to the pilot, after takeoff, at an altitude of 100 feet above the ground, the engine’s right side cowling door became unsecured. He stated that the door was banging in the air flapping onto the top of the cowling. As the pilot began to maneuver toward the airport to land, the cowling started to move to the closed position, and the pilot attempted to further close the door with rudder input. The pilot stated that he was fixated on keeping the cowling closed and inadvertently let the airspeed slow to the point that the airplane started to descend rapidly. The pilot applied full power to recover, but did not have enough altitude to regain flying speed. The airplane impacted trees, resulting in substantial damage to the upper and lower wings. The pilot stated that there were no mechanical malfunctions or anomalies with the airplane. A Federal Aviation Administration inspector examined the cowling camlocks and found them to be in good condition.