Ben Ainslie’s team tripped up in the Solent today when they capsized their development boat T2 during training.

The 45ft foiling cat named ‘T2’ is the team’s latest boat to be launched and is a more powerful and sophisticated version of the AC45f cats that are used in the America’s Cup World Series events.

According to early reports from the team T2 capsized off of Ryde, Isle of Wight.

‘The wind range was between 15 – 19 knots, the boat was sailing at a slow speed when an issue with the wing inversion initiated a capsize to windward,’ read the statement issued shortly after the incident.

No other vessel was involved and there were no injuries.

This is the first time that the team has capsized one of its 45ft cats despite having trained in more boisterous conditions than those experienced today.

But the T2 development boat differs significantly from the team’s previous boats, particularly in the power it can generate and in the complexity of the hydraulic systems aboard the boat. Where the AC45f has conventional ropes and control lines, T2 has just one rope aboard the boat, the wing sheet.

Few details are known at present as to why the accident happened and at first it may sound strange that it was control of the wing that caused the capsize – surely easing the wing sheet could have saved the day?

But modern Cup wings have become increasingly efficient and can generate high loads both to windward and to leeward. The twist control in the wing, which is altered hydraulically, can change both the power in the sail and the height at which it is delivered. This, combined with a boat that is substantially wider than the previous machines, can be tricky to handle, especially at low speeds when there is minimal stability generated by the foils. As many high performance sailors will say, ‘speed is your friend’, an AC cat is no different.

There are however some details in the picture that may provide clues as to the circumstances leading up to the capsize.

First, the direction of the white caps suggests that the boat was heading upwind.

The port daggerboard is down and the crew are largely on the starboard side suggesting T2 was going upwind on starboard tack. There is however one crew member to port indicating that maybe the team was about to head into a tack.

The helm is set to port suggesting that Ainslie was trying to bear away, as you would given that the rig is coming in to windward.

Given that the jib is flapping it may be that the cat’s rudders stalled out before the tack and the boat span up into and through the breeze.

With such a powerful wing and only a small jib to create the fore and aft balance in the sail plan it is easy to find the centre of effort of the sail plan shooting backwards and overpowering the rudders, causing a spin up into the breeze.

If this was the scenario it would seem likely that the capsize would have been slow and ‘controlled’ as the wing, which is still set for port tack would be generating vertical lift and slowing the mast’s descent onto the water – hence the minimal damage that was reported by the team. The boat would have slowed down too as it rounded up into the wind and its windage put on the brakes.

Whatever the cause the capsize will likely to be an embarrassment to the team rather than the crisis that Oracle faced in the last Cup when it nose dived its AC72 at speed in San Francisco. Then it took months to rebuild the boat. According to Land Rover BAR, the plan is to be back on the water in the New Year.

The crew aboard included:

Ben Ainslie

Paul Campbell James

Bleddyn Mon

David Carr

Nick Hutton

Andy McLean

Benjamin Muyl – observer