The pilot of the tailwheel equipped airplane reported that while attempting to land on the "grass portion of the runway", parallel to the paved runway, the ground was soft. Subsequently, the main wheels sunk into the ground and the airplane nosed over.
The airplane sustained substantial damage to its right-wing lift strut and vertical stabilizer.
The pilot reported that there were no pre-accident mechanical failures or malfunctions with the airplane that would have precluded normal operation.