Red Bull gave Alinghi wings: here’s why the Swiss AC 75 may be revolutionary

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The new AC 75 Alinghi Red Bull Racing. 37th America’s Cup Recon.

Alinghi Red Bull Racing has officially launched its new AC 75 in Port Val, Barcelona, and we have to admit that compared to the very first impression we had of the boat, we had to think again. Early images, with the AC 75 in the half-light of the “unveiling” ceremony, had cleverly kept hidden the real shapes of what promises to be like a new “family” of AC 75s, different from Luna Rossa and Team New Zealand. The collaboration with Red Bull Racing seems to have opened up a different interpretation of the AC 75 box rules, one that broke the mold from what had been seen so far. The Swiss challenger led by Ernesto Bertarelli promises to be a potential big surprise.

That strange aft wing on AC 75 Alinghi Red Bull Racing

Alinghi Red Bull Racing the particular shape of the stern that almost looks like a wing. 37th America’s Cup Recon.

There is little doubt that the first element that jumped out at everyone is that sort of wing that the boat has in the back, as well as in the design of the stern. The design team led by Marcelino Botin, developed the lines of the broadside differently, which seen from behind have a teardrop shape, and do not run all the way to the stern as on the AC 75s seen so far but end earlier.

Alinghi Red Bull Racing, you can see how the broadside is shorter than the other 75s, and with a particular drop shape that indents, and the stern flat, and wider than where the edges end, which goes to form this sort of wing. 37th America’s Cup Recon.

At the end, due to the teardrop shape, the broadside falls back slightly, while at the stern the completely flat transom continues. As the broadside returns to that area, a kind of projecting wing is formed, which could have a dual function, aero and hydro dynamic.

Alinghi Red Bull Racing. America’s Cup Recon.

This particular shape is also created by the fact that the boat, from the foil arm attachment to almost the extreme stern, has a sort of edge that runs over a constant width, and that widens slightly at the height of what we call the “wing,” as seen in the photo above.

As you can see from these photos, with the boat in displacement this particular area of the boat will touch the water, and will probably have an anti drift function. What is more interesting, however, is to understand what aerodynamic function such an element might have. Indeed, there are several things about the new Alinghi that might be interesting and worth exploring.

We told you in one of our in-depth articles how flat and round hollow or tunnel-like shapes under the hull were key to recreating the air cushion between hull and hull necessary to give lift to the hull.

At left is Te Rehutai, Team New Zealand’s winning boat at the last America’s Cup. At right are two possible design solutions to recreate the air cushion between the hull and water surface. Alinghi’s seems to be closer at least in part to the yellow solution, unlike what had emerged at first glance.

Scheme this functional to reduce the size of submerged foils through precisely a hull that also gives lift. So far Luna Rossa has chosen the almost totally flat option under the hull, with low-resistance shapes at the bow. Team New Zealand has shapes not too far from the Italian hull, but more substantial bow volumes and a hint of a tunnel before the flat part of the hull begins. Instead, Alinghi seems to have ushered in yet another, perhaps more extreme path.

The fairing like a Formula 1 car

Alinghi Red Bull Racing, the detail of the fairing shapes. America’s Cup Recon.

In the central area of the boat, in fact, Alinghi’s shapes do not look flat, but slightly concave, and then flatten out altogether toward the stern.

The fairing of a Formula 1 car has areas hollowed out to recreate the air cushion and fluid acceleration under the car.
Alinghi Red Bull Racing, Day 1 of AC75 (B2), Launch of the new AC75, ”BOAT ONE” in Barcelona. – 16April2024. 37th America’s Cup Recon.

It is a solution inspired by the Formula 1 world, which increases the air cushion and can generate acceleration. In F1, the variance is much more pronounced and is used to create downforce (top-down thrust) and not lift (bottom-up thrust) as AC 75s would need. However, it is a solution that, in a compromise version, Alinghi seems to have implemented on its boat that really seems to have benefited from the collaboration with Red Bull Racing.

Alinghi’s AC 75 with new foils

Alinghi Red Bull Racing, the new foils are not completely flat, like those used by Team New Zealand to win the last Cup, but slightly curved downward. Alinghi added just above the foil attachment a second silhouette, in addition to the upper one found in the other AC 75s, probably intended to catch the spray from the water. America’s Cup Recon.

Foils up to or until now represented the biggest mystery of the next version of the AC75. Shrouded in an impenetrable halo of secrecy, teams are conducting a long series of tests on a wide range of possible configurations. Only a few aspects appear certain since they now appear established in all the tests that have been seen at sea. The first is that the appendages in the next edition, probably because of the increasingly higher speeds of the boats, will have a very high aspect ratio, with a decidedly tiny chord and a length up to the permissible limit of the regulations (also recently amended to that effect). Alinghi Red Bull Racing is the first syndicate to show a version of the new generation of appendages, which had barely been glimpsed during the months of training.

On foils a huge theme for designers to study may have been the flexibility of materials, in an attempt to make profiles take on particular shapes or to circumvent some regulatory limitation (curved foils could take advantage of flexibility for this reason). This is also a theme dear to Formula 1, it goes back there again in the case of Alinghi Red Bull Racing. Notwithstanding the fact that we do not know on the subject of foils what the choices of the other unions will be, which at the moment have shown only the old appendages.

Mauro Giuffrè and Federico Albano

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