CHALLENGER REVELATIONS

The anticipation as to what the latest generation of AC75s would look like following a season of testing and training aboard the teams’ prototypes had been building steadily. Throughout the season, teams had been racking up the hours aboard their first boats as they worked day and night to gather sufficient data and experience to nail down the design of their second boats in what felt like an impossibly small timeframe on the road to the 36^th Cup.

Making matters harder for those who were charged with creating a race winning concept there were additional problems to deal with. The world health crisis had forced the cancellation of two key America’s Cup World Series events, denying all three Challengers and the Defender Emirates Team New Zealand from checking in with each other to gain valuable intelligence on both their own performance and that of their competitors.

The rules prohibit training alongside another team, so the validation process continued as an in-house exercise. The only comfort was that everyone was facing the same issue. By the time the second boats were complete teams had invested around 140,000 man hours in design and construction without ever being able to present their work to a competitive datum, other than their own predicted performance calculations. As indication of the truly unprecedented nature of this new class around double the amount of hours were spent designing than those spent building the beasts.

The message is clear, these are complex racing machines, said to comprise around 18,000 parts each in a boat that is built to achieve top speeds in excess of 50knots.

The America’s Cup is always a game of high stakes, but this time around, with so much invested and yet so little known, the pressure could hardly be greater as the clock counts down to the first event. Little surprise then, that there was so much tension during the build-up to each of the three Challenger launches.

Despite months of intelligence gathering on each other, when it came to individual curtain raisers, teams had little more idea as to what their opponent’s finished article would look like than the public who queued at the gates to catch a first glimpse.

These are the boats that, barring any disaster, teams expect to be taking into battle come the first official race on 17 Dec as the America’s Cup World Series gets under way. These are boats that can and will be modified, refined and enhanced along the way, yet even so, all the teams are clear as to just how high the stakes have become.

And all the teams know it. But if any had thought that the new boat launches would reveal a consensus across the small elite fleet, their illusion was to be shattered as each one of them was revealed.

AMERICAN MAGIC - PATRIOT

First into the spotlight was American Magic’s Patriot, a sleek development of the team’s first boat Defiant.

“When you see Defiant and then you see Patriot, the obvious differences come out in the hull forms,” said skipper and executive director Terry Hutchinson.

The highly polished gloss finish did a great deal to conceal some of the finer details, but even so it seems clear that there are some key areas that have indeed changed, most notably in the forward sections.

“The flare in the bow? It's just maximising driving force and minimising the heeling moments that you're producing,” explained designer Marcelino Botin.  “The bow shape and the whole boat is guided towards that objective.” 

Part of that detail can be seen in the bow with the early stages of a centreline skeg that is formed with the resultant flared forward sections. This skeg then runs aft to around 70 percent of the length of the hull.

“You should look at the hull shapes as a continuation of the rig and the sail plan,” he continued. “What you're trying to achieve with the hull is to maximise the driving force of the rig and the sails and minimise the heeling moment, it’s as simple as that.”

And here the Americans are not alone. Among the many differences across the fleet, the skeg is a detail that all the Challengers are using, albeit to different degrees.

The broad concept is to maintain an aerodynamic seal under the hull to prevent high pressure from the lower end of the sail plan leaking around to the low pressure side and reducing efficiency. This in turn keeps the forward driving force at maximum at a time when the boat needs it most in order to accelerate quickly enough for the foils to then lift the boat. Once this happens, the hydrodynamic drag reduces dramatically and the boat accelerates even more quickly.

This transition phase from hull in the water (displacement mode), to fully flying (foiling) is critical. Like turbo charging a car to pull away faster from the lights, acceleration is expected to be one of the key performance aspects, particularly on a course that is constrained by electronic boundaries.

Further evidence of this transition can be seen on Patriot’s rudder where there the upper section has a much longer chord than the lower end to ensure that the helmsman has sufficient steering at low speeds while having a super skinny and low drag foil when Patriot is up and flying.

On deck the American boat is a super smooth, streamlined shape clearly designed with low aerodynamic drag in mind.

INEOS TEAM UK - BRITANNIA

When it came to INEOS Team UK’s launch the change in style could barely have been more stark. Few were expecting such a radical looking design.

“Britannia, is vastly different to boat one. But we think it's certainly a step in the right direction,” said INEOS Team UK’s chief designer Nick Holroyd.

While the British boat also has a skeg, this is a large box section affair that sprouts immediately from an aggressive, angular bow and runs a long way aft. Interestingly, unlike Patriot’s slender affair, Britannia’s skeg increases in width towards a max under the cockpit area, it’s section shape possibly creating lift in a similar way to a conventional centreboard.

The aggressive underwater sections around the middle of the boat, along with the secondary step or bustle as it is referred, appears to provide additional stability while at the same time providing a more abrupt reduction in wetted surface area (and hence drag), as the boat raises out of the water. Presumably a way of promoting faster acceleration into the foiling phase.

“The hull’s got two functions,” Holroyd continued. “It's your launch vehicle and it's an aerodynamic body that you put under the rig. You're dropping the keel line down to meet the water to improve the aerodynamic seal, so you push that one pretty hard. And then, getting the kind of volume distribution you want, the boats accelerate hard from about 10 knots to 18 knots when they take off. So, you start looking at the drag of the hull through that speed regime and try to get into the air as quickly as you can.”

Yet extreme though Britannia II is, he still feels that this is a boat that was meant to be.

“Some boats are hard to kind of get off the page and into production because there are things nagging you,” he said. “Yet, some boats actually come quite easily and this is one of them. There are three performance aspects we were really focused on at the time and throughout the process they seemed to kind of mesh well.”

But whatever the technical speculation around such a radical looking boat may throw up, the reality is that of all of the Challengers, Britannia II is the biggest departure from a team’s first boat. Normally, such a big step from one boat to the next instead of a seamless evolution rings alarm bells. But this is no ordinary Cup.

Luna Rossa Prada Pirelli’s Jimmy Spithill knows this well and is quick to point out why this Cup could be different.

“It's a real, real tough group here, no one's lacking anything,” he said. “Everyone's got the money, the technology and the resource. There's no excuses. It'll be a good series.”

LUNA ROSSA PRADA PRIELLI TEAM - LUNA ROSSA

Of the three Challengers, the Italian boat was the sleekest of them all. A complete opposite to Britannia II, smooth lines below the waterline and gentle curves everywhere, this is a machine that has been designed as much for the air as it has the water.

Just as each individual bow characterises the other challengers, so the gentle radius that forms the knuckle of Luna Rossa’s bow when viewed in profile sets the scene for lines that flow throughout the 75ft overall length.

“We are pretty happy with what we have done and the evolution of our boat,” said designer Horacio Carabelli. “I think we have stepped up pretty well. It's just different details and small details that we really improved from our first-generation boat.”

As with the American Challengers, the Italians’ second boat has a skeg that flows elegantly and effortlessly from the forward sections but in this case runs all the way to just ahead of the rudder. Here, the dual chord rudder is similar in concept to that of Patriot.  

But what stands out most of all aboard the Italian design is the clearest indication across the three boat Challenger fleet of how the curved, humpback style sheerline creates a hull and deck that is now treated as a lifting surface as well.

 

Such is the apparent wind speed over the deck that reducing drag is no longer the only goal. At these wind speeds, lift can be created to contribute to the forces that are raising the entire boat out of the water.

All three boats exhibit this style but it is Luna Rossa that stands out.

But while their boat may look modest when compared to the other two, Carabelli, along with all the other designers in the Cup, is already thinking to the next big line of development.

“Foils are going to be a big parameter to look into and everybody's looking for minimal drag and maximum manoeuvrability,” he said. “And I think that's where we will see a lot of changes. It will depend on how you look at the overall picture, not only maximum speed, but also about how you get around the corners. And I think that's very important.”

But for all the differences in style and approach, there is one hard fact that unites all the teams, summed up by Cup veteran and four times winner of the Auld Mug, INEOS TEAM UK’s CEO Grant Simmer.

“We're pushing to do stuff that we haven't really done before. And sometimes we don't always have mature tools to actually make a decision. So you've got to take a bit of a leap of faith with some of these decisions.”

And see how they shape up when the Defenders show their hand.