The Racing Spot / sailing

Luna Rossa, a high-tech challenge

The America's Cup began as a sailing match between yacht clubs. And still, 170 years after that famous race around the Isle of Wight, only yacht clubs can call the challenge. In those days, the rules set team nationality requirements and technological contributions were forbidden, but while the nationalistic component has not entirely disappeared, technology has played the main part in the event since 2000. So, teams can reach out far and wide hiring the world's best designers and engineers and using innovations with no limitations.

The perfect class

The 36th edition of the America's Cup will go down in the history for the introduction of a revolutionary new boat. The new AC75 class combines the allure of the monohull, ideal for this one-on-one match racing event that made regatta history, with the best technology for reaching very high speeds and the safety of a boat that can right itself if it capsizes.

These boats can travel at speeds in the order of 40 knots upwind and 50 knots downwind. Designed in a joint study by defender Emirates Team New Zealand and the record-breaking challenger Luna Rossa Prada Pirelli, the AC75 class rules can be summed up in a few numbers: an overall length of 22.70 metres, including the bowsprit; a beam of 5 metres; 6.5 tonnes in weight; 26.5 metres of mast height from the deck; 225-235 square metres of sail area, including the mainsail and the jib (plus 200 square metres of the Code Zero). The Luna Rossa Prada Pirelli was made of carbon fibre and aluminium by Persico Marine, based in Nembro (Brescia, Italy).

The magic of foiling

The real break with the past is the set of appendages called foils that in an ideal configuration allow the hull to lift off from the water and stay up achieving incredible speeds. This is nothing new for sailing. Foils have been used on racing dinghies and ocean racers, that in any case are just over 18 metres long, for some time. The rear foil (basically, the rudder blade) has a perfect T shape, with a maximum draught of 3.5 metres.

The two side foils look like wings, having a maximum opening of four metres each, and they can tilt, so when the AC75 is moored they are lowered to minimise the beam and take up little space. For the record, they weigh a good 500 kilos each and can withstand a breaking load of 27 tons. Crucially, the arm (or wing) at the tip is adjustable and provided with flaps.

Flight controller

How does it work? When the foil flap bends down, it creates lift not unlike an aircraft wing with flaps. The rudder foil, on the other hand, acts as the tail of the aircraft. The more the stern approaches the water surface, the greater is the angle of attack of the main foils and this causes the hull to lift. Once the boat is in the air, the crew works to lower the bow over the water and the foil flaps are raised to increase stability.

The pitching of an AC75 that rises and falls on the water is not a bad thing because it demonstrates the continuous search for the ideal take-off conditions.

That is why the skipper of the Luna Rossa Prada Pirelli no longer at the helm – that incidentally is a console full of buttons reminiscent of a Formula 1 car – is called the flight controller. He is in charge of the trim.

A double mainsail

All this set-up would be worthless without the power of the sail rig that is obviously reminiscent of the ocean-fairing multihulls that introduced the wing mast concept to increase the available surface area and give more safety to the vessel already back in the 1990s. Now more than ever in the America's Cup, the mast-sail rig is a key element and the new class rule has allowed the introduction of the very innovative soft wing. The small bow jib and the large Code Zero for light winds are nothing new besides the fact of being made of state-of-the-art materials.

The ingenious soft wing consists of two parallel hoisted mainsails in which the sail shape controls are placed. It provides the efficiency of a rigid wing with an ease of use not far from that of a conventional sail.

A touch of mystery

The way it works is still not entirely clear in keeping with the halo of mystery that always shrouds the America's Cup technology. Some claim that it “conceals” the mast's braces inside while many others pondered about the absence of the traditional boom where the lower side of the mainsail is usually inserted. This could be to make the most of the wing profile of the sail, “securing” it to the deck to create a perfect whole. As always, we will probably know a lot more by the end of the event. Certainly, the new solutions will be carried across from boat racing and to pleasure yachting. It has always been so and this is one of the many merits of the Regatta of Regattas.

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