America’s Cup, boat secrets and differences revealed by designers

Four America’s Cup designers analyze the differences between the hulls competing from Aug. 22 in Barcelona. And they reveal unknown design secrets. But even for them, men will make a difference

America’s Cup, the designers’ word

She inferences and assumptions follow about the performance of the six AC 75 boats that will participate in the 37th America’s Cup. One thing is certain, little or nothing is known. And it will go on like this until August 22/25 when for the first time the six teams will compete in preliminary races.

In this uncertainty, it took the Tip&Shaft Sail Racing website, the bible of world competitive sailing experts, to tell us something certain about the upcoming America’s Cup. He asked four top designers involved in team design to evaluate the differences in design choices, comparing the six boats, which, we remind you, will be the ones now undergoing solo training.

In fact, the regulations prohibit building, as happened in the past edition, to make a second boat. The four top designers who reveal the differences among the six boats are: Philibert Chenais (Ineos Britannia) who has been designing for the America’s Cup since 2007 with winner Alinghi; Dimitri Despierres (American Magic) since 1998 on Cup teams, Sam Manuard (Alinghi Red Bull Racing) famous for his Mini Transat and Class 40 ocean boat victories; Benjamin Muyl (Orient Express) who comes from previous experience with the British Ineos.

The design

Their analyses are important because the America’s Cup is won or lost first and foremost in terms of naval architecture. The fastest always wins, says Cup history since 1851.

The six boats that will compete from Aug. 29 to Oct. 27 in Barcelona represent the third generation of AC75s and the second generation of measuring rules (two boats were allowed for the 36th edition). According to the architects and engineers, the rules have undergone only a slight change but are very rigid, particularly in terms of displacement and the position of the center of gravity, not to mention the rigid parts (mast, foil arms and boom).

Foils in the America’s Cup

“There is a clear convergence on some architectural or steering aspects, says Dimitri Despierres: “We cannot analyze the profiles, flaps and all the complexity of the appendages based solely on photos, but I notice that all the foils are now T-shaped, with very similar and relatively small surfaces. This is the lesson of the New Zealand design of the last Cup and also the result of lightening the boats,” he concludes.

The hulls

The word goes to Benjamin Muyl regarding the hulls: “There are notable differences between Ineos Britannia, with its very pronounced shapes, and American Magic or Luna Rossa, which have focused heavily on aerodynamics, or the stern of Alinghi, whose cockpit ends in a wing with a vertical trailing edge.”

The opinions of the four design gurus converge that Ineos seems the most radical of the fleet, with its bulkier hull, raised deck, and large water intakes in the bottom of the hull ending at the bow of the rudder, unlike its opponents. “The deep bustle (a kind of keel) is designed to close the space between the hull and the water and prevent the passage of downwind air, which disturbs the sail plan,” Philibert Chenais points out.

Chief designer Martin Fischer, who moved from Luna Rossa to Ineos Britannia, adds, “Other aspects of Ineos’ hull seem like nonsense, such as the raised deck. However, this is precisely the element that produced the best results in the CFD studies we conducted, in collaboration with Mercedes.”

Sam Manuard then takes the floor, “Hull and deck are intimately linked, and it must be understood that in flight mode, the most recurrent, this union becomes just the basis for an even more efficient sail plan. Multiple compromises are possible, and after testing some very radical configurations, our choices fell on more versatility, like those of the Italians and New Zealanders.”

In this regard, spies in Barcelona during testing noted Ineos’ difficulty during takeoffs and during landings, which are frequent when the wind and sea are not coming from the same direction, a situation that is very common in Barcelona waters.

Energy

No one thinks about it, but AC 75s consume tremendous amounts of energy; watts are used for the few dozen minutes of a regatta’s duration. The hydraulic jacks on the foils are controlled by batteries, while the energy for adjusting the sails comes from human power, produced by the pedals of the grinders sitting on their bicycles. American Magic made the countercultural choice of lying down cyclists. This allowed the deck line of the New York Yacht Club’s hull to be lowered by 30 centimeters compared to its competitors.

Will it work? Benjamin Muyl thinks so: “A winning layout in terms of aerodynamics and lowering the crew’s center of gravity, but less efficient in terms of developed power.

Speaking of men on board, in all teams the crews no longer cross each other when changing tack. But in the U.S. hull the helmsman and trimmer are side by side while they are in line on all the others. Here is Dimitri Despierres’ explanation of the choice of American Magic: “You lose aerodynamics, but you move the crew’s center of gravity forward, so you load the foil more and the rudder less.”

Equipment and adjustments

While the distribution between mainsail and headsails (J1, J2, and J3) seems quite similar across hulls, the control systems seem to reveal different approaches. Emirates Team New Zealand’s choice is to have two separate sheets on two cylinders, which allows the pressure on the two edges of the sail to be managed differently.

As Sam Manuard confirms, “A slightly different system was devised, with a boom fitted with rails for the edges, unlike other boats where the rails are attached to the sail. All these mechanics are critical in terms of performance. The ability to adjust very quickly and with great precision is a very important element.”

Philibert Chenais feels the same way, that the real differences will not be in the, but “the foils, the sails and their systems. No one knows who and where they have buttons, what they control, how they are combined together. As for the architecture of the hulls, the teams are unlikely to make much progress with their AC75s between the training sessions, which began in the spring, and the preliminary regatta in Barcelona (Aug. 22-25), which anticipates the start of the Louis Vuitton Cup (the competition among the five challengers, Aug. 29-Oct. 7.”

Sailors, the human factor of the America’s Cup

But surprisingly when it comes to the element that will make the difference in the next America’s Cup, designers have similar views. And it is not about their work. “The regulations are rigid in terms of the changes that can be made, and everyone has been investing in one direction for the past three years. What will make the difference is the sailors’ learning curve. On architecture you gain cents, while a successful maneuver means a difference of several knots of speed,” Benjamin Muyl judges.

Of the same opinion is Dimitri Despierres, who believes that the performance of humans will make a difference, particularly on mechatronics, which allows several simultaneous actions to be combined in an automatic and calibrated manner. “In the old regulation, these controls were possible, but now we work on closed loops, so we can program target values to be achieved. Now there is no limit to what we can achieve.” To know who got it right will have to wait until the second half of August.