America's Cup: Video shows Luna Rossa came close to a capsize

A short-crewed Luna Rossa lights their afterburner during training in Cagliari, Sardinia © Luna Rossa

Video published on leading Italian sailing website Farevela shows that Luna Rossa exhibited many of the same moves as Emirates Team New Zealand's Te Aihe, in the kiwi AC75's capsize on December 19, 2019.

The Italian America's Cup Challenger was sailing in 10-12kt breezes, and race training, when the AC75 is generating its fastest speed as a function of the windspeed.

Both incidents had a similar genesis in that the two AC75's had just executed a high speed "slingshot" gybe, foiling in a normal position with both main foils immersed and lifting, the rudder wing was also generating lift with the AC75 under control and flying moderately high. Initially Luna Rossa is trimmed down slightly by the bow, but viewed in slow motion, the AC75, now riding on just a single foil rotates to go bow up before the rudder starts aerating and putting up a very pronounced wake. Interestingly the wake from the main foil is extended well back and may have affected the operation of the rudder wing, causing it to ventilate, lose grip, and the stern sinks as the bow is pushed even higher by the main foil and the boat continues to rotate skywards.

At the extreme point of the rotation, Luna Rossa's main foil also stalls throwing up a very solid foil wake, while the rudder and its wing throws a big rooster tail of spray, while in normal operation its wake would be minimal.

Like Te Aihe, Luna Rossa crashes back into the water and continues to slide across the surface. But there the two incidents have a different ending as Luna Rossa is able to round up into the wind and the canted windward foil comes into play and pulls the AC75 upright.

In Te Aihe situation the Kiwi AC75 begins to round up, but not sufficiently for the canted windward wing to provide the required righting moment and the AC75 capsizes, lying on her side waiting for assistance.