Land Rover BAR skipper and principal Sir Ben Ainslie put a positive spin on lopsided losses against Oracle Team USA on the Great Sound on Wednesday amid growing concerns regarding his team’s performances of late.

“It was great to be out sailing on the America’s Cup course, the conditions were fantastic,” Ainslie said. “Each day on the water is a development day, and this will continue all the way through this America’s Cup cycle.

“Our shore, design and sailing teams are doing a fantastic job working to maximise the performance of our race boat.”

Land Rover BAR won the America’s Cup World Series in the AC45F foiling catamaran, but have yet to replicate that form in their more technically advanced AC Class catamarans.

“Unfortunately, the British seemed to be having issues and weren’t competitive which was a bit of surprise,” said Oracle skipper Jimmy Spithill following last month’s practice races in the AC45S, in which BAR posted a dismal 1-8 record.

One of the theories being touted about BAR’s struggles has been the team’s decision to test daggerboard foil designs near their home base in Portsmouth rather than in Bermuda, something which appears to have given their rivals who did most of their testing in the Great Sound the edge.

The foil concepts that the team are using are believed to be based on the conditions in the Solent where the density and chop of the water differs to the conditions here, resulting in slower speeds.

The same may be true for Emirates Team New Zealand, who have done all of their testing in Auckland.

With the AC50 boasting mainly one design elements, much of the focus of the design race has been centred around the foils that lift the hulls out of the water to allow the boats to virtually fly three times the true wind speed.

The key to achieving high speed is designing foils that reach the edge of stability without comprising control.

According to rules governing the 35th America’s Cup, each competitor is allowed to build a maximum total of four daggerboard foils, which may be modified a maximum of four times, provided at least 70 per cent of the daggerboard foil determined by weight maintains its original shape and structure.

Foiling catamarans were introduced to the America’s Cup scene at the previous event in San Francisco in 2013, where Defender Oracle produced a stunning comeback to retain their title.