America's Cup: The 'difficult' new rule set to pump up the pressure on teams

The America's Cup is won on the water, but it's the work that goes on behind closed doors that makes all the difference. Your team might have the best sailors but, it's the fastest boat that usually comes out triumphant.

Now, there will be little room for error with the class rule and Protocol for the 37th edition of the race allowing teams to build just one new AC75, despite innovations to make the vessel lighter, including having three fewer sailors onboard.

"The challenge is broad and difficult, which I guess is what all engineers seek," Ineos Britannia chief technical officer James Allison said of the class rule.

"In particular things like the foils, where there are just three foils and they have to basically be the same as one another. That means you really only get one go at picking the racing foils for the competition.

"That places a huge amount of pressure on you to make the right judgment between the risk and the reward that might come with being super ambitious on one hand, but maybe overstepping the mark if you push it too far."

In the campaign for the 36th America's Cup, won by Team New Zealand in Auckland this year, teams were allowed to build two AC75 vessels, allowing them to explore the radical new class of 75-foot foiling monohull and get some sort of a grip on it before committing to the design for their main race boat.

Team New Zealand successfully defended the America's Cup in Auckland this year. Photo / Brett Phibbs.

For the next campaign, existing teams will be able to sail one of their two boats from the last campaign before building their new one, and all teams will have a one-design, scaled-down version – the AC40 – which they can tinker with to see what does and doesn't work before having to return it to its original specs for use in the women's and youth America's Cups.

New teams will be able to buy an AC75 from the teams who competed in the last regatta, and will be allowed to start sailing it earlier than existing teams - with a 20-day window of catch-up sailing set for new competitors next June, before all teams can get on the water in September.

Only being able to build one boat not only makes competing more affordable for prospective challengers, but it also lessens the advantages the existing teams have in their experiences from last campaign.

The cost of competing was a driving factor in just four teams making the starting line in Auckland.

The new class rule results in major changes to the first generation AC75s, with Allison estimating the designers from Team New Zealand and Britannia, who put the class rule together, found ways to shed "something like a tonne" of weight from the vessels.

The lighter boats will have more success in lighter airs, which proved to be an issue in Auckland at times, particularly during the Christmas Cup regatta last December.

"We're making the boats lighter, fewer crew, bigger span foils, and all of that together is going to make a more exciting boat. It's a higher top-end speed and a lot better in the light air so we'll be able to get up on the foils in lighter breeze," Team New Zealand designer Dan Bernasconi said.

"The class rule is really an evolution of the AC75 class and it's a real step up."