The pilot of the tailwheel-equipped airplane reported that, during the takeoff roll, he had difficulty staying on the runway. He added, in a telephone interview with the National Transportation Safety Board investigator in charge, that, while airborne, the airplane aerodynamically stalled into brush off the end of the runway. The airplane nosed over and came to rest inverted. The airplane sustained substantial damage to the left wing. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The automated weather observation station located about 9 miles to the north-northwest reported that that, about the time of the accident, the wind was from 170° at 8 knots, gusting to 18 knots. The airplane departed the southeast runway.