THE PILOT AND ONE PASSENGER WERE LANDING ON A GRAVEL AIRSTRIP FOLLOWING COMPLETION OF A PERSONAL CROSS-COUNTRY FLIGHT FOR THE PURPOSE OF SHEEP HUNTING. DURING THE LANDING TOUCHDOWN, THE LEFT MAIN GEAR TUBE SEPARATED AT THE AXLE SPINDLE AND THE AIRPLANE GROUND LOOPED. THE PILOT REPORTED FINDING CORROSION AT THE POINT OF SEPARATION IN AN AREA COVERED BY THE AIRCRAFT'S FABRIC SKIN. THE FABRIC WAS INSTALLED ON THE AIRPLANE 30 YEARS BEFORE THE ACCIDENT. THE AIRPLANE HAD RECEIVED AN ANNUAL INSPECTION 43 HOURS BEFORE THE ACCIDENT.