Below is the introduction to an article extracted from www.freedomyachts.org called FREEDOM YACHTS MAST CRACKING - CAUSES AND THE CURE. Written by the former chief engineer (Masts) of Freedom Yachts (now defunct). It will interest those with carbon masts and anyone thinking about building them. The pdf is here.

"Freedom Yachts and their free-standing masts were built by Tillotson-Pearson Inc. (TPI) from the late 1970s to about the mid 1980s in Warren and Portsmouth, RI. The earlier boats were outfitted with aluminum masts, but from about mid-1980 on, the masts were built of carbon fiber. I was hired as a staff engineer at TPI in March, 1980, and at that time the company was doing the design, engineering and testing for the new carbon fiber masts. By July, the chief engineer left the company, and I became the new chief engineer to carry on with mast development for the Freedom Yacht line. In the course of time, the Freedom Yacht masts experienced circumferential cracking in the exterior surface. Usually, this cracking is cosmetic only and not of immediate concern. However, if left unattended for too long a time (we’re talking years, here) the cracking can open up and lead to more serious cracking within the masts. This paper ... provides a procedure to cure the problem."