America's Cup - Dramatic wingsail break on SoftBank Team Japan

by Sail-World.com on 27 Oct 2016 All are safe after a broken wing appendage onboard SoftBank Team Japan’s AC45 Sport ended testing yesterday as the sailors pushed the upper wind limit of the platform on the Great Sound in Bermuda.

The broken wing – belonging to the team’s next generation America’s Cup Class (AC50) competition yacht – suffered a significant fracture in the lower trailing flap causing the entire lower portion to detach completely.

The AC45S boats are close replicas of the AC50's that will be sailed in the 2017 America's Cup with many of the parts being interchangeable with the AC50. Typically they will sail with an AC50 wingsail - which is a one design in terms of its profile, but the control systems are unique to each team and their designers.

At this stage it is not known whether the failure was with the one design specification, the team-designed control system, a building fault, or operator error. If it is a flaw in a one design element then it would be expected for all teams to be advised.

The video shows the lower second element of the wingsail detaching from the front element, or main spar in its upper corner where there is a hinge point for the element. The detached element then crumples and is destroyed.

The team is expected to substitute a replacement element either from their own sources or from Oracle Team USA.

Teams are restricted in the numbers of wingsails they are permitted to build for the AC50's



“We were pushing the boat hard today in 20-23 knots of wind”, said Skipper and CEO Dean Barker. “We were doing an upwind run with Oracle Team USA and heard a loud bang as the lower flap of the wing broke and blew off the back of the main element. Fortunately there was no injury to any of the crew and we managed to get the boat back to the dock and avoid any further damage.”

One of only a few testing days to date in this Cup cycle that have seen wind speeds at the top of the design threshold for these boats, the breakage creates a unique learning scenario for team’s designers as they fine-tune their heavy-air wing control systems for the next America’s Cup. The upper wind limit for racing is 25kts without using the bizarre tide adjusted wind limit calculation used in San Francisco last year which saw the wind limit range from 19.9kts to 24.3kts - depending on which week racing was staged.

“Any issue like this is always good to happen now as opposed to next year”, continued Barker. “As we learn more about these boats and push them further up the wind range, the loads get increasingly higher. Understanding how hard we can push is a key part of being successful next year.”

With less than eight months until the start of the 2017 America’s Cup Qualifiers, and with build times already forcing teams to finalize their design parameters, there may not be many more opportunities for team’s to test at these extreme levels.

“As with any issue like this it is important to look through all the footage and data to correctly analyze the problem. Jumping to a wrong conclusion early can lead to making some bad decisions.”

The SoftBank Team Japan shore team will now have plenty of sleepless nights ahead of them as they pull double duty in the wing shed.

They’re now tasked with both prepping the team’s backup wing for testing this weekend while also building a new lower appendage for the America’s Cup Class wing as quickly as possible.

“We are fortunate that we will be back out sailing by the weekend”, concluded Barker. “While we will miss a couple more breezy days the week, it is nice to know the program can continue without any significant loss in time.”

Three of the America's Cup teams are training in Bermuda, with Artemis Racing and Oracle Team USA each with two AC45S development boats. Softbank Team Japan is using an AC45S from Oracle Team USA with whom they have a very close design, training and performance data sharing relationship.

All six teams have AC50's underway, with Groupama Team France having their boat built at Core Builders Composites in Warkworth, NZ. Meantime they are sailing their AC45S from their base on Lorient, France. LandRover BAR are winding down their development program, sailing from their Portsmouth base. Emirates Team NZ are three months into their development program in Auckland sailing their single AC45S. All three teams are expected to have been experiencing winds at the top end of the 25kt range for racing as the British and French teams go well into autumn and the New Zealanders experience the vagaries of the Spring weather patterns. They are the only team expected to launch their AC50 in their home waters.