>>212734310Sail boats, race cars, bike frames, and the use in aircraft is primarily for wings and control surfaces.
It's great for applications where tensile strength is needed.
>>212732798 (OP)>whenNever. It's the wrong material for compressive loads and repeated stress.
>>212736177>We can make carbonfiber spaceshipsBecause those pressure vessels are fighting decompression. Not compression. The structure is being stressed from a positive internal pressure to an unpressurized exterior environment. In the same way that an aircraft fuselage is filled to a pressure that's higher than the exterior pressure due to increased altitude. It's entirely the wrong material to make a submarine out of.