Cup Spy Special: A swell day in Barcelona
by Richard Gladwell Sail-World NZ 4 Aug 04:27 PDT
4 August 2023
INEOS Britannia - LEQ12 - Day 64 - August 3, 2023 - Barcelona © Job Vermeulen / America's Cup
Since Barcelona was announced as the venue for the 37th America's Cup at the end of March 2022, many Cup Veterans have questioned how the foiling America's Cup class will handle the exposed venue.
As the AC75 is a unique design concept, little was known as to how the 69ft foiling monohull would handle the at times difficult sea conditions for which Barcelona is renowned.
Those questions were answered to a large extent on Thursday afternoon, with the current America's Cup champion Te Rehutai, being given a solid workout, by the Cup-winning crew.
From what we've seen on all the RFS videos, the Kiwis handled it well, with their longer boat. It remains to be seen how the Swiss or the USA handle a similar sea state in their first generation AC75s.
In Barcelona, it seems to be unusual to find the waves on the same axis as the wind, with reconnaissance teams identifying and providing measurements on up to three swell/chop directions running in the race area.
The issue seems to be particularly difficult for the foiling AC75, when there is a substantial swell coming head on - ie at about 45° to the true wind angle.
The America's Cup class of yesteryear would just take the sea on the nose and punch through it.
The issue for the AC75 is being able to achieve foiling speed, take off, and then keep the AC75 foiling during a tack or gybe, and coping with the new angle of the swell and wind.
In some situations, the America's Cup boats have attempted to foil upwind in a following sea state.
However, most of the issues seemed to be answered today in a three-hour sailing session for Te Rehutai.
"Sure, some of the other teams have seen bigger swells," said twice America's Cup champion, Josh Junior after today's sail, which he observed from the Kiwi's chase boat.
"Basically it's all generated from the Mistral coming out of France - and the strong wind coming out of there pushes the waves, which in turn wrap into Barcelona.
"But unfortunately, today we didn't get the same wind - it was a little bit lighter."
"We got the waves but not the wind."
"The waves make a massive difference to how you have to sail the boat. "It gets a lot trickier when the waves get big - and that's where the skill of the crew comes in.
"I guess punching into them, like all boats, is always harder than going down them. So depending on which way the waves are skewed, the boat can be easier or harder to sail."
The AC75's seaway problems are complicated because the boat has to reach a speed of 14-16kts to lift off onto its foils - which is challenging in a head sea with the foil arms dragging in the water, throwing up a lot of spray.
Once foiling and clear of the surface, the drag reduces markedly, and the AC75 will chop through the swells with ease - provided the flight control is accurate and the boat is not flown so high that it loses its grip on the water and gets pushed sideways. If it is flown too low the underside of the hull will make contact with the surface - something the designers may have contemplated, and opted for a drag-reduced underbody. However too low, or close to the surface and hull and foil arm drag come back into the equation, slowing the boat - and maybe costing the race.
In the conditions that prevailed on Thursday, Junior who won the 2021 Finn Gold Cup says the conversation changes on the Kiwi boat "When the waves are bigger, the conditions are trickier or shiftier, or gusty the conversation always turns a little bit more towards the boat handling, like like any boat, and then it's just about trying to get your head out of the boat to keep racing.
"So like like all sailing, it just gets a little bit more challenging when the waves get up," he added.
Four times winner of the Finn Gold Cup, and double Olympic Gold medalist Giles Scott was asked the same sea-state questions after the Brits came ashore having been on the water for a trying five hours in their 40ft test boat.
"I think the sea state today certainly changed a lot," he told top sailing journalist, Justin Chisholm, who is part of the Recon Team tracking the British boat. "Looking back to last week, when we were sailing the AC 40 [off Barcelona], we had some lumpy days. But today was a big step up on the conditions that we saw last week.
"I'd say it was the wind speed and the wind direction. This sea-state was pretty extreme today, and certainly very, very tricky, in the 40 footer."
"Does it change all of the angles, exits from tacks, and gybes?" Chisholm asked.
"Yeah, it changes absolutely everything," Scott responded.
"As a sailing group, we've got to adjust to it. You're changing sail shapes all the time and having to steer around waves.
"The pilots have got a lot on trying to keep the foils in the water as well."
"Sea-states like today certainly make the sailing a lot more challenging, let's put it that way."
Looking back at the last seven weeks, Scott said there had been no significant changes to the test boat.
"But there's been plenty going on in the background," Scott explained. "As you probably see from today, there are no major component changes. But for sure, there's been little tweaks here and there."
Wednesday was supposed to have been the Brit's first sail in less challenging conditions. However, after a couple of delays, the session was cancelled when the forecast increase in the breeze kicked in around 1330hrs.
"It was some of the data link setup that we had between the base, the boat, and back in Brackley so it got sorted throughout the day, but unfortunately we missed our window. The breeze picked up in the late afternoon. I think it got north of 20 knots and we weren't that keen to push out on that with a recommissioning for T6."
"How would you score yourself today, Giles, on today's performance," was Chisholm's parting shot.
"A solid commissioning day," replied the double Olympic champion. "It was certainly an eye-opener for some of the conditions that Barcelona can offer.
"It was a good day. Let's give it an eight out of 10."
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