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America's Cup Rialto: November 13 - Sticky business as AC75's struggle in the light

by Richard Gladwell, Sail-World NZ 13 Nov 2020 02:57 PST 13 November 2020
INEOS Team UK - Waitemata Harbour - November 13, 2020 - 36th America's Cup © Richard Gladwell /

The nightmare condition for crews in the upcoming America's Cup is likely to be winds that are close to the minimum windstrength of 6.5kts than the upper 23kt limit.

After the breeze literally boxed the compass across all five course areas for the Prada Cup and 36th America's Cup, crews finally got their practice session around 4.00pm in winds of 2-7kts on the inner Waitemata Harbour - sailing mostly between Bean Rock lighthouse and the container port at the City end.

It is a very difficult stretch of water notable for variable wind pressure, tidal flows and with the high rise buildings of downtown Auckland at the western end, with a couple of volcanic cones on its northern side and the high land mass of Bastion Point to the south.

Hopefully this area will not be used for Prada and America's Cup racing. It highlighted the most serious flaw of the AC75 class, which is the massive speed difference between the boats in the lighter end of the windrange when one of the foiling monohulls can get foilbourne and their competitor can't.

Once foiling and generating apparent wind, the AC75 will sail at three times true windspeed, maybe four.

With the three challengers, Luna Rossa, INEOS Team UK and American Magic all within the same small patch of water, it would have been easy to make accusations of training in a co-ordinated manner - a practice that is prohibited in the Protocol.

However today there was none of that. It was the first time the challenger group had come up against their peers since they have been in Auckland. For the crews and their support teams it was a "Come to Jesus" moment, when they were struggling to get foil-borne and could look over to one or both of their competitors - and saw them clear of the water and flying away with a speed delta or differential of about 15knots between the two boats. Come the Prada or America's Cup that is a race determining moment.

Of course being able to negotiate a foiling, or near foiling tack, in these conditions is vital to retain your maragin, or be able to recover lost ground.

Unlike the AC50's the AC75 doesn't have the same inability to sail downwind in these light conditions and weirdly looked more comfortable sailing downwind.

There were two questions to be answered today. The first being how the radical stepped chine hull of INEOS Team UK would cope in the conditions. The short answer is "Not Well".

The other two with their less extreme hull shapes fared better in that they seemed to get foiling with less effort than the Brits.

Once up and going it was difficult to tell if there was any speed difference between the three. But certainly the Brits were no slower and may well have had a speed edge.

The other question was, similar to the situation with the AC72's - is it more beneficial to use the larger Code Zero, or the more efficient but smaller #1 jib.

There was no definitive answer to this one. Initially the AC75's were living off their Code Zeroes - and like most group activity looks OK when everyone is doing the same. However later in the session the teams started trying their #1 jibs instead and looked just as good as with the Code Zero - maybe even better.

Who knows what will happen come the start of the Prada Cup? Unlike the 2013 Cup there is no weight advantage in leaving the bowsprit and Code Zero ashore. The rules this time around require that a compensating weight be carried.

We may know more by the end of the weekend - there are two more days of light winds forecast.

One thing is for sure the integration of a crew's sailing ability with chosen design strategy, technology and their ability to work through the gears in winds of the lower end of the range may well prove to be the winning of the America's Cup - and more so than who can sail the fastest close to the upper end of the wind limit.

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