Wired magazine’s Adam Fisher has reported that the accident was due to a structural failure when the forward beam broke.
Nathan Outteridge was helming. His father, interviewed on Australian television said,
“They heard a few cracking noises, and then the boat tipped on its side. Before it went right over the mainframe just broke and it collapsed a bit like a taco shell cracking.”
That forward beam had been damaged during tow tests, without the wing in place.
From the report last October:
“The plan was to launch and tow the boat, to put it through its paces at speed, then to step the wing… We launched the boat, towed it to the bridge at speed and on the way back we heard some noises as we were loading the catamaran platform itself. The boat will come out of the water and go into the shed and we will spend the rest of the day thoroughly going through it.”
Photos and TV helicopter video make it clear that the port hull and forward cross beam broke up.