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| ©François Chevalier |
Of the six contenders competing for the America’s Cup in Barcelona, one specifically epitomizes all the progress that has been achieved since the AC75s were created, and that’s the boat from the American Magic challenge, Patriot, the second of its name.
A brief flashback brings us aft to 2019, with the first Defiance, which focused on flight. If they’re supposed to fly, they may as well be designed as planes! But it soon became clear that these machines needed to take off, that they would pitch up, skim the water and tend to fall back into the water at any point. The New Zealanders shown the method by devising a canoe hull under the platform, and all the others followed in their wake. The previous Patriot has a median ridge under the forward two thirds of the boat to ease the take-off and cushion the splashdown.
The freeboard limit imposed by the rules led the Design Teams to create a bulge in the midship section of the hull. The British had conceived of digging a central passageway to grow the effect of the mainsail’s flushness with the deck, thus increasing the sail area. The mainsail is only measured above a certain height. Nevertheless, they had extended this passage all the way to the stern, so that the boat looked more like a wagon than a rocket.
The second generation was therefore fitted with this famous inset hull, more or less U-shaped or V-shaped. However, they all maintained a fairly wide waterline at rest, for minimum initial lateral stability. A characteristic of the AC75 rule is that the racers are measured when at rest, whereas this posture is unlikely when the yacht is in motion. When the keel is a few centimeters above the water, the ideal flying position is reached. The underside of the hull forms a wing, which at full speed helps to lift the ship. Research on the ground effect dates to the work of the Russian engineer Alekseyev in the 1960s. At 80 km/h or 90 km/h, the ground effect seems significant and reduces the drag of the foils, a speed factor. The volume of the V-shaped hull of our Patriot fully supports the weight of the boat, which remains unstable at rest, limiting the wetted surface area during water landings.
On the 2021 winner, to achieve greater performance, the functions of each part of the AC75 were maximized. The Americans have reworked and refined every portion, focusing on aerodynamics for the upper section and hydrodynamics for the lower section. The deck design is also particularly meticulous, with the smoothest curves in the entire fleet. To center the weights, six of the crew, including the cyclists, are aligned, more on the axis, below in the middle lane.
©François Chevalier
The jib and mainsheet traveler bars are embedded below deck, and roller blinds at each end close off the cut-out perfectly. The only drawback is that this beautiful layout comes at the price of a large surface area, but in this field, any architectural option has consequences that will be settled by the competition.
©François Chevalier
Patriot, AC75
Designer: American Magic Design Team
Co-ordinator: Scott Ferguson
Launching date: May 7, 2024
LOA: 20,70 m
LWL: 20,70 m
Beam: 5 m
Draft: 5,50 m
Air draft: 28 m
Displacement: 6195 kg
Mainsail: 146m2
Solent: 70 m2
Crew: 8
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