I've seen the majority of A-cat mast failures occur in a downwind capsize and typically if the downhaul is still on tight. We always tell new A-cat sailors to be sure they ease some downhaul tension downwind in heavy air. This takes some of the compression loading out of the mast which seems to make it vunerable to breakage if you flip over. Other than that scenario, the masts seem pretty durable and reliable. In 7 years of racing in the class, I've yet to break a mast (knock on carbon!).

The most durable carbon mast I have seen is the Riba section made for the Bimare F-18HT. I've never seen one break and I've had some pretty violent flips in that boat and the mast seemed to take it all well.

Bob Hodges
A-Class USA 230