A few days after Justice Cahn sat down in the New York Supreme Court to hear both sides of the dispute over the 33rd America's Cup, Alinghi made the unexpected move of publishing details of the new 90-foot rule which will shape the boats for the future. More importantly, making public the details of the new rule might have moved Alinghi and BMW Oracle Racing closer to withdrawing their weapons of mutually assured destruction. Instead, there now appears the chance of reaching an entente cordiale after months of brinkmanship which have severely tarnished the credibility of the America's Cup.

Originally Alinghi and America's Cup Management said the details of the rule, to be known as the AC90 Rule, would only be made available to teams that had officially entered the 33rd Cup. But following a few weeks of bad publicity, the Defender decided to make the rule public, perhaps as a token of appeasement.

An ACM statement said: "This rule has been crafted over the past six weeks through a design consultation process with all entered challengers, the Defender, and headed by Tom Schnackenberg as the class rule and competition regulations consultant for ACM. Designers from all six entered teams have met regularly since the design process began on 15 September."

The decision to publish received a cautious welcome from BMW Oracle and the Golden Gate Yacht Club. Club spokesman Tom Ehman said: "The concern has always been about the defender having several months' lead-time ahead of challengers to design and build a new boat, without anyone else knowing what the design rules were.

"Alinghi agreed that they would significantly change the original rule to address this problem. We hope this will be reflected in what was published yesterday. This will be easy to determine once we compare yesterday's document with what they started out with and we continue to ask Alinghi to provide this. When our designers can verify that we are all starting from the same point we hope to see all other issues resolved quickly, as agreed recently with the challengers."

Larry Ellison's team has told challengers it is prepared to agree to other compromise proposals on remaining protocol issues, provided it can satisfy itself that that the new design rule is fair for defender and challengers alike.

So, what will the new boats look like? The AC90 Rule defines a boat that will be 90ft overall maximum length, 6.5m in draft while racing, and will have a displacement of 23 tons. Schnackenberg  commented: "In writing the AC90 Rule we have used the experience gained in forming Version 5 of the America's Cup Class rule. We have tried to keep it simple because of the short timeframe, while also taking care not to ignore the lessons of the last 18 years of the ACC. The rule is a box rule rather than a rating rule and differs greatly to Version 5 in that the yacht will be big, fast and much more demanding."

Britton Ward and Bruce Farr, who now work for the Desafio Espanol challenge and were part of the round-table discussions that helped formulate the AC90 Rule, made their analysis of the new boat. Farr, who previously worked for BMW Oracle Racing and who has long called for the old Version 5 boats to be scraped in favour of something more dynamic, sounds like he might have got his wish. This is what Ward and Farr had to say: "Combining the light displacement with a substantial sail area increase, particularly downwind where spinnaker area is unrestricted, and the result is a much more powered-up boat both upwind and down. These boats will be challenging to sail to their maximum potential, but promise some spectacular performance that will be very exciting to watch.

"Determining the right amount of hull form stability will be one of the first major challenges all designers will face. Given the light displacement and the large sail plan you can expect them to be substantially more powerful hull shapes than the Version 5 ACC boats. These boats will be designed to maximize their sailing length so expect plumb or dreadnought stems and potentially some level of transom immersion to be the norm.

"There are also only limited restrictions on the hull shape with limits only on transverse hollows leaving designers substantial latitude in shaping the hull. We expect there will also be plenty of variation in the appendage choices - single or dual aft rudders are allowed and will be tightly related to the style of hull form."

Kiwi yacht designer Brett Bakewell-White observes that the new boats will not be so different from the last generation of fixed-keel Maxi yachts built a few years back. "Dimensionally these boats are not dissimilar to the Maxis from the period of Rambler (the old 90ft Shockwave) and Zana," he commented on the Sail-World.com website. "If you cut eight feet of overhang off Zana's stern, effectively you are close to the new rule except they are three tonnes heavier with less draft. Sail area and everything is all pretty similar." Coincidentally Zana, which has competed in a few Rolex Sydney Hobarts in her time, is up for sale. "All Zana needs is eight feet taken off the stern and you basically have an AC boat," said Bakewell-White.