THE PILOT WAS CONDUCTING A SERIES OF PRACTICE SWATH RUNS WHEN HE LOST CONTROL OF THE AIRPLANE DURING CLIMBOUT. THE PILOT STATED THAT THE AIRPLANE STALLED DURING THE CLIMB, AND THE AIRPLANE COLLIDED WITH TREES ON THE DEPARTURE END OF THE SWATH RUN. EXAMINATION OF THE AIRPLANE FAILED TO DISCLOSE A MECHANICAL PROBLEM. EXAMINATION OF THE ACCIDENT SITE DISCLOSED THAT THE AIRPLANE WRECKAGE SUSTAINED TREE AND GROUND IMPACT DAMAGE ALONG THE LEADING EDGE OF THE WING ASSEMBLY.