Complex sentence: Cooling difficulties and driveshaft weakness made the Clipper very unreliable however, and the project was discontinued; as of 2001 there were only three survivors, only one of which is in relatively good condition.
Split into simpler sentences: Cooling difficulties and driveshaft weakness made the Clipper very unreliable however, and the project was discontinued. As of 2001 there were three survivors, only one of which is in relatively good condition.