The airplane sustained substantial damage when it impacted a drainage ditch following a loss of directional control during takeoff. The pilot stated that during the takeoff roll, the right brake failed and the airplane veered to the left of the runway. The pilot pulled the engine power to idle and the tail of the airplane came down. The airplane veered across several cotton rows and impacted a drainage ditch. Inspection of the airplane revealed a hole in the right brake line which allowed brake fluid to leak out of the system.