The pilot of the tail wheel-equipped airplane reported that, during the landing roll with a crosswind, the airplane began to swerve right as the tail wheel touched the ground. The airplane then veered off the right side of the runway and collided with a ditch. The airplane sustained substantial damage to the fuselage just above the right main gear attachment. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. Probable Cause: The pilot’s failure to maintain directional control during the landing roll which resulted in a runway excursion and collision with a ditch.