It'll probably be a while before there's a definitive answer about why a Swedish America's Cup catamaran went cartwheeling out of control on San Francisco Bay yesterday, killing British Olympic medalist Andrew "Bart" Simpson. Simpson was trapped beneath the crippled boat for 10 minutes or more before rescuers could free him. Desperate attempts to resuscitate him failed.
But there are early indications that the boat's design might have been flawed. According to a report in Wired, "The problem was with the boat itself, either faulty engineering or faulty construction. The boat simply broke apart under sail, folded, then flipped."
Wired also reported that "the Artemis boat has had a history of cracking and problems with the carbon fiber used in the twin 'beams' — the two girders that lash the two narrow hulls together. The boat had been in and out of the shed numerous times in an attempt to correct those problems."
During Thursday's practice run, according to the report, "the forward beam — the girder in front of the sail — gave way during a practice run. The two hulls, no longer connected, began sailing in slightly different directions. This caused one hull to snap just forward of the aft beam, and the mast, held up by high-tension rigging connected to the front of the hulls, simply fell over. The boat began to cartwheel, ultimately trapping Simpson underneath and drowning him."

It's also clear that Simpson's team, Artemis Racing, recognized the danger posed by a capsizing long before yesterday afternoon and provided some training on how to deal with it. Beyond disorientation and panic, the hazards also include the possibility of becoming trapped beneath the netted "trampoline" between the craft's twin hulls.