After months of speculation as to what type of boat Alinghi plans to use to defend the America’s Cup, the cat’s now out of the bag. At least it will be once the giant hangar style marquee that is sitting just a few hundred metres from the shores of Lake Geneva in Villeneuve is disassembled.

As the white fabric walls come down this Sunday, the Swiss team’s giant catamaran will be prepared for its launch on Wednesday 8 July, a task that will involve the world’s most powerful helicopter, a Russian Mi-26 that will lift the catamaran over the buildings before lowering her into the small harbour next door.

So what does she look like?

She’s wide, very wide. While the team won’t confirm specific dimensions, the assembly tent is understood to be 30mx40m, a space that she fills amply from beam to beam with around 10m to spare in the longitudinal dimension. The result? A 90x90ft catamaran, so little surprise here. Until, that is you see what a 90ft beam really means in the flesh – stacks of righting moment and, once the mast is stepped in the middle of the forward cross beam, an engineering nightmare for the designers.

Peak loads of 70-100tonnes in parts of her structure won’t be unusual according to designer Rolf Vrolijk and the cats cradle of struts and stays that run back and forth along the underside of her cross beams are testament to this.

“When it comes to the structural side she’s very similar to Ernesto’s 40footer,” said co-designer Dirk Kramers referring to team boss Bertarelli’s Bol d’Or winning cat. Be that as it may, such structure emphasises the engineering challenge in supporting a highly loaded mast in the middle of a 90ft beam. Beams that are a work of art in themselves and through their proportions, once again illustrate the scale of the issues.

BMW Oracle’s current boat on the other hand is a trimaran and while this too is believed to be 90x90ft, having a central hull makes life easier in some respects for the designers, albeit at the risk of creating a boat that is heavier than a catamaran.

Overall, Alinghi’s while painted hulls look like scaled up versions of a Hobie Tiger or Nacra cat, her bows raked aft with the characteristic low down volume forwards and correspondingly skinny topsides switching to the more normal flared hull shape amidships. According to Kramers there is little particularly special about their shape. Instead the key issue lies with the loads and how the crew can work her up to speed safely.

“Breaking something or hurting someone is the biggest worry,” he admits. “The potential for equipment failure is very high and as a result we have spent a considerable amount of time testing both the finished structures and the construction of the components. Just about every major area is wired for load analysis using fibre optic strain gauge technology,” he continued. “We have red lines for every major component.”

So what kind of performance can we expect from Alinghi 5 as she is being referred to by the team?

“Upwind I think we’re looking at around 20 knots,” said Kramers. “Wind conditions won’t vary this that much, but when it comes to going downhill I think we could see speeds in excess of 30 knots.”

Such speeds would be completely at odds with a traditional America’s Cup event and while exhilarating to watch will be at the sacrifice of the often close boat on boat racing that characterised the last Cup.

“It’s certainly the case that last time around we considered that being able to engineer a half boat length advantage was a considerable success,” explained Rolf Vrolijk. “This time the difference is going to be measured in kilometres.”

With such big stakes and so little known about the performance of such an extreme multihull, how much development will take place between now and the Cup itself in February next year?

“By the time we get to the event my guess is that the boat will look very different indeed,” he continued. “We haven’t ruled out the idea of a 140ft boat either,” he said referring to the Deed of Gift which makes provision for a larger boat if rigged with two masts.

“To my mind it doesn’t mean it would have to be a ketch, simply a rig that provided a contribution to the performance of the boat,” he said. “That could be in the form of a wing mast perhaps which might modify the wind flow. But to start with such a radical idea would be to introduce far too many variables.”

With her launch date set for Wed 8 July, what is the team’s programme?

“It will take a while to step the mast and get her set up for sailing, but we plan to be doing this around 15-20 July,” continued Vrolijk. “We also need to do some tests on how we are going to transport her to the Mediterranean via helicopter to see whether this will be possible. If it isn’t we might have to take her down the Rhone, but this would involve some serious work craning her over the locks and bridges along the way, a major exercise.

“August 1 is a national holiday in Switzerland and after that we plan to be off to the Mediterranean.”

The first step along the road to the big match between the cat and the tri. After so long knowing so little, a picture is starting to emerge but, given the enormous amount of development that is in store for both teams, what we see will not be what we get.