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America's Cup: Emirates Team NZ foiling on first sail + Video

by Richard Gladwell, Sail-World.com/nz 18 Sep 2019 03:11 PDT 18 September 2019
Emirates Team New Zealand foiling quite easily - Sail - Day 1, September 18, 2019 © Emirates Team New Zealand

America's Cup Defender, Emirates Team New Zealand became the second team to sail and foil an AC75, in the buildup to the 36th America's Cup.

Following on the back of a successful first sail by Challenger New York Yacht Club's team, American Magic who sailed and foiled their first boat, Defiant, late last week, Emirates Team New Zealand emulated their feat, laying to rest many of the concerns regarding the AC75 class.

From video of both sessions, sailed in light breezes, without whitecaps visible, the monohulls were able to get on their foils easily and stay foiling.

The performance of the AC75 appears to give the lie to some of the antics of the prototype foiling monohulls used by three of the Challenging teams, however, testing across the full wind range will be required to resolve those questions.

Today's sail followed a brief sea-trial a week earlier off the teams base in the America's Cup Village in downtown Auckland. A feature of that test, which had to be cut short due to rising winds, was the apparent inability to raise the double-skinned mainsail completely. The team has not disclosed whether that was a problem with a halyard sheave at the top of the mast or a halyard lock.

The issue persisted today delaying the start of the sailing session, with a crew member up the rig trying to rectify the relatively common initial issue which is not possible to be tested with the boat ashore or tied up at the dock.

One of the downsides with Emirates Team New Zealand's decision not to build a less than 38ft (12 metres) overall length prototype is that these issues cannot be worked through in half scale ahead of the launch of the AC75.

In that context, the Defender would have to come away feeling pleased with the progress made today, and while slightly behind the AC50, on its first sail (which was able to execute foiling tacks and gybes in the first 90 minutes of being on the water) the AC75 seemed to function well, straight out of the box.

The video below reveals the answers to a couple of key questions for the team.

The first is whether the bustle which runs down the centreline of the AC75 would come into play as the boat at minimum foiling speeds. The video tends to indicate that the bustle certainly plays its intended role, creating a virtual catamaran around the bustle and the leeward foil, and keeping the windward foil clear of the water for as long as possible.

Many of the video and still images of the day show the AC75 being sailed in the same mode, or an even more extreme stance than the AC50 - bow down and heeled slightly to windward creating a lifting force on the AC75 in a similar way to a windsurfer. The fact that the crew were able to maintain this stance in a sustained way, points to a close correlation between what the team are seeing on their practice simulator and what is happening, in the real-world, on the water.

The other point relates to the double skinned, deck sweeping mainsail, which in the video can be seen lying very close to the flat centre deck in the cockpit, forming an endplate and tidying up turbulent air generated with conventional main boom systems. The foot of the mainsail still looks untidy in this area, and no doubt more design work will be done to improve the efficiency of this device further.

Although the design concept of Te Aihe is quite different from Defiant, the two AC75's both helmed by New Zealanders, appear to have different sailing styles in these conditions. Te Aihe appears to be sailed in a more heeled to windward bow-down stance, while Defiant is more upright, lending support to the theory that her scow-like design is predicated around maximising ground effect - allowing the AC75 to sail on a cushion of air trapped and compressed below her wide flat hull.

Today Emirates Team New Zealand caught a lot of the Cup aficionados by surprise, opting to head out deep into the Hauraki Gulf - but still accompanied by a fleet of spy boats and fans.

On the water photography at any range is not prohibited by spy boats in this edition of the America's Cup. In previous editions, a limit of 200 metres was in force. The use of drones is not allowed. Neither is tracking a yacht using GPS or range-finding gear.

The easing of the long-standing restrictions feels very surreal, particularly at the sight of a RIB from a competitor team within close range and with a long lens focussed on some aspect of a competitor, free of the clutches of the Arbitration Panel.

The Challenger teams have to lock off their race boat design, well before the Defender, and the Challenger design teams will be keen to understand, the approach of the most experienced and successful team in the 2021 America's Cup regatta. The fact that the AC75 class rule is open to a range of design interpretations and permutations means that design options taken by one team may not be relevant to another - but understanding the other teams' boats is a key to ensuring their own is as good as it can be.

While it is common practice to Emirates Team New Zealand to have their practice sessions well out in the Hauraki Gulf - where there is plenty of room to stretch their legs - and undertake performance analysis over a sustained distance in steady wind conditions.

However with the next America's Cup due to be held on inshore courses there will be a much greater premium on manoeuvrability and reacting to quick changes in wind direction and angle, it will be surprising if the team continue to sail on their traditional training waters. The situation is more pressing given that the design options for the second and likely race boat have to be locked off in the next few months, certainly by November/December.

One of the key advantages that Emirates Team New Zealand holds is that the 36th Match will be sailed on its home waters, and the way the pre-regatta scheduling has panned out, they will be the only team to sail an AC75 on an America's Cup course before locking off the design option for their second boat.

Maybe in the near future, Kiwi America's Cup fans will be able to see Te Aihe at much closer quarters than today.

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