Technical lessons from the America’s Cup

Published on March 28th, 2021

North Sails Director of Design and Engineering JB Braun discusses the technical lessons that have come up during this America’s Cup cycle…


The AC75s are challenging the sail shapes and their range in a more complex way than has ever been done before. Mainly because of the low righting moment of the boats when they go slow, and their high righting moment when they go fast.

When the boats are going slow, their righting moment – their ability to resist heel – is coming from the foils, and those foils don’t work until they’re going fast. So just the boats getting going is a complex process which requires full sails and a low center of effort. And when the boats get going, you want to reduce that power.

In terms of sail design, that leads to different sail structures that power up or de-power. One of the biggest things that you want in a sail is added range, or added optimum application – meaning, to be able to react to a change of conditions if you’re using a given sail. One of the big things that’s going to come out of this America’s Cup is the application of that range.

How do you get a sail to be powered up working at very low wind speed, but then have the same sail working at triple or quadruple the apparent wind speed?

With normal boats, your apparent wind speed may only go a fraction of that. But when the AC75s are sailing in 12 knots of wind, they’re going to get up to 50 knots of apparent wind. The same sail needs to change its shape quite a bit to be optimum at the low and the top ends.

Having a sail that can morph itself and have a wider range reduces the uncertainty with selecting a sail. This is an area that’s going to come out as being a big plus for a lot of sailors, the top racers and the Wednesday night races, TP52, ORC fleets, championship racing, and more. – Full report


36th America’s Cup Match Scoreboard (wins-losses)
Emirates Team New Zealand (NZL): 7-3
Luna Rossa Prada Pirelli Team (ITA): 3-7

Advancing as the winner of the PRADA Cup, the Italian challenger faced the Kiwi defense in the best of 13 series. After the postponement due to government COVID-19 health regulations, the 36th America’s Cup Match racing schedule had two races per day planned for March 10, 12, 13, 14, 15, and each day after that until the first team had won seven races.

More information:
• 36th America’s Cup details: click here.
• Complete America’s Cup coverage: click here
• Additional America’s Cup information: click here

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