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Cup Spy April 13: Luna Rossa launch their AC75 silver missile

by Richard Gladwell, Sail-World.com 13 Apr 20:21 PDT 14 April 2024
Luna Rossa Prada Pirelli reveal their AC75 in Cagliari, Sardinia - April 13, 2024 © Luna Rossa Prada Pirelli

Luna Rossa Prada has unveiled their Challenger for the 37th America's Cup.

Luna Rossa's sixth America's Cup challenger emerged from the boat shed in Cagliari covered with a black hull shroud. On her first attempt, Miuccia Prada broke a bottle of Cantine Ferrari's Maximum Blanc de Blancs on the protected bowsprit.

At that moment, the black tarpaulin immediately fell away, revealing a metallic silver AC75, which caused an audible gasp of appreciation from the spectators and guests. The Italians have reverted to the silver hull colour, first seen in 2013 on their AC72 wingsailed foiling catamaran.

Luna Rossa's AC75 design is not a radical departure from the Swiss and New Zealand AC75s launched last week.

The significant difference between the three teams is that the Swiss and Kiwis have both sailed an AC75 extensively in Barcelona. In contrast, the Italians have not sailed their AC75 since March 2021 and have only sailed for a few days in their AC40 at the America's Cup venue.

Presumably, they have good information on Barcelona sea states and are confident that they have been able to replicate these at Cagliari. The Italians did build a custom-designed 40-foot test boat, which looked to perform well. However, as the AC75-equipped teams found out, there was a big difference in performance between the 40-foot test boats and the 70-foot AC75s in the Barcelona seaway due mainly to the different foiling geometry.

The Kiwi, US and Swiss teams have all been able to test their cyclor powered hydraulic systems, in full size, on their 2021 edition AC75s - another area that will need to be tested by the Italians, French and British teams.

After its retirement from active service, American Magic pointed out that their AC75 Patriot was designed for the flat, almost landlocked courses of the Hauraki Gulf, not the open sea of the Mediterranean with its often off-axis seaway. So, there is a need to step away from a boat designed for Auckland conditions - and Luna Rossa's third AC75 is quite different from their first two.

So, the performance of the Italian AC75, off Barcelona, will be interesting to watch. There is no reason to believe that there will be any issues, but confirmation of that will set to rest the minds of their many fans.

Playing out in the background, during this AC75 launch season, is a game of designer roulette. Marcelino Botín, American Magic's lead designer from 2021, is now in a similar role for Alinghi Red Bull Racing; Martin Fischer, Luna Rossa's lead designer from 2021, is now with INEOS Britannia; and the French Orient Express Racing Team has purchased a design package from Emirates Team New Zealand.

That said, with the three teams having now revealed their AC75 raceboats, their design teams seem to have similar views of the direction and opportunities offered in Version 2 of the AC75 Class Rule.

The silver-hulled AC75 is not a radical departure from the Swiss and New Zealand AC75s launched in the past week.

With the Defender and Challenger from the 2021 America's Cup having revealed their third AC75, their design teams seem to have similar views of the direction and opportunities in Version 2 of the AC75 Class Rule.

The Italian aft underbody appears to be a more pregnant hull shape than the Kiwi and Swiss designs.

Most AC75 hull shapes appear to change with a change in viewing angle, making the team spies less sure of the nuances of hull shape. The underbody colours chosen by the teams defy camera accuracy because there is no light and shade to contrast the various sections of the hull.

That qualification aside, Luna Rossa has an interesting skeg/bustle shape, with the keel line running straight from the bow before tapering upward into the transom—which is now just a measurement point on the AC75s rather than having a functional purpose.

Hull shapes can become very distorted by a camera lens. With that qualification, the photographs and video show an underbody treatment reminiscent of those encouraged by the IOR rule, where the aft underbody of the hull was a more voluminous shape.

On their AC75, the Italians use the increased hull volume to house the sailing crew and cyclors in four pits on either side of the deck. Once clear of the crew accommodation, the hull lines - the sheerline, chine and keel (excluding the skeg) all come together in a nice aero-friendly taper, intersecting at the transom.

The chine line is softer than the other two AC75s. It starts higher up in the bow, runs down to pick up the pivot point for the foil arms, hits maximum depth under the crew accommodation, and then lifts up into the transom.

The Italian bow/forefoot has the same nicely rounded signature shape that has been a feature of all the Luna Rossa race boats—going right back to the 2000 America's Cup.

Alinghi Red Bull Racing and Emirates Team New Zealand have opted to carry the keel skeg in a straight line, right to the transom, and theirs appears to be deeper and more dominant than the Italian.

Again, without being able to eyeball the Italian hull, it does seem to have a more subtle shape than the previous two AC75s launched for the upcoming America's Cup.

Like the others, the bow section is flared to avoid the very wet consequences of errant foil control, but on Luna Rossa it appears to have a much softer design treatment as it merges with the rest of the underbody.

The deck on Luna Rossa is interesting—with the same lower, more aero-friendly forward hull section seen on the other AC75s of the past week. However, it takes quite a sharp upturn at the start of the crew accommodation and keeps its height almost flat through that area before tapering to the transom. This approach differs from the more rounded deck/sheerline shape favoured by Emirates Team New Zealand and is the opposite of the cut-away topside of Alinghi Red Bull Racing.

The deck/cockpit area is dished with a small drop from the accommodation side deck. It is also clear-finished, reflecting the beautiful build by Persico and, of course, saving the weight of the paint used.

The foil arm dimples appear to be more elongated than the other two AC75s. This could be an illusion created by the various paint finishes (and remembering that the Swiss boat has only been revealed for 20 minutes in the dark of night).

As an aside, the pivot point for the foil arms is the only control on the hull beam - allowed to be 2050 mm from the centre line with just a +/- 2mm tolerance. So, in round numbers, the beam of an AC75 measured between the foil arm pivot is 4.1 metres - giving the designers plenty of scope to make trade-offs in hull lines and functionality. There are other measurements to restrict more extreme/unsafe design approaches, but generally, the hull shape is free-form, explaining why the different design approaches are possible.

The Italians are expected to test-sail from their Cagliari base before moving the new AC75 to their 2024 America's Cup facility in Barcelona.

From the AC37 Joint Recon Team:

On this day, the Italian team Luna Rossa Prada Pirelli rolled out their AC75 legacy mast, which was missing most of its fitting at 08:15hrs.

Shortly after, the AC75 Boat 3 rolled out entirely covered with a black sheet.

The mast was stepped and the boat remained in standby for several hours before the unveiling ceremony officially started.

Once the bottle was broken, the tarp came off showing revealing the shiny silver hull body.

With a large crowd in front of our recon square it was challenging to get clear view.

Some features were: bustle developing sharp from the bow decreasing and ending up to the rather edgy transom. The bow is similar to second iteration boat without any chines, lower and channeled deck with four elevated pods on each side.

There is a rather concave deck surface developing from the flat bow towards aft of mast.

Foils and rudder were legacy components of previous boat iteration. The boat touched the water at 13:25hrs where it stayed for guest viewing until liftout.

[Michele Melis, AC Recon]

Additional Images:

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