Had been sailing for 2 hrs, 10 to 12 knots of wind, gusts 15 absolute max. Flew a hull 6" off the water a couple of time. Boat felt great! Had been upwind and down a couple of times, did run the spin, but did reach with the screacher few times. Checked the diamonds several times, always finding the mast in column.
Mast broke shortly after heading back upwind. The boom has an underside traveller (ala 18 meter square) for the mainsheet between the rear traveller and the boom, so there is zero resistance from the mainsheet to the compressive forces the boom applies to the mast. I could see the boom flexing maybe 3" out of column(10' boom, big squaretop EP main), the mast rotation limiter was on pretty tight because the builder, Malcom Davy, had expressed his concern earlier that the boom was putting a lot of pressure on the mast. The mast is quite well reinforced at the gooseneck, and he feels that the forces were transmitted up the mast to the first weakest point. The break is 6' above the base, 36' mast, hounds 7' from the top of the mast, aft swept spreaders. Malcom said he'd had the boat out in 20 kt conditions before, had flow a hull close to vertical, so he'd put more force to the rig than I did.
What do you think?

Dave