- Te Kahu - Emirates Team New Zealand - Waitemata Harbour - February 20, 2020 - photo © Richard Gladwell / Sail-World.com
Dear Recipient Name
Welcome to Sail-World.com's New Zealand e-magazine for February 24, 2020
Following the return of Peter Burling and Blair Tuke from the 49er Worlds in Geelong, Emirates Team New Zealand was out sailing on Tuesday in their test boat Te Kahu.
Launched in the third week of January, the 12 metres long Te Kahu was sailing straight out of the box. The half-size AC75 didn't have too much of a shake-down before being put into filling the gap left by the team's AC75, Te Aihe.
In the buildup to the 2017 America's Cup, Emirates Team NZ was the last to launch a test boat. Only Team Groupama France didn't have one - and paid the price being eliminated after the Qualifiers. Some very clever thinking effectively gave the Kiwi team an AC50 to sail in June 2016. The other teams never got their hands on the real thing until late February 2017. That was thanks in part to the Arbitration Panel signing off on a time-out as part of the settlement over the illegal removal of the Qualifiers from Auckland, triggered by the change of class from an AC62 to an AC50 nine months after entries had opened.
Reading the America's Cup tea-leaves is a vexed pursuit at the best of times.
Right now there is very little to go on, except for comparing some team released and manicured video clips, and the occasional photo, again showing little that the PR people don't want you to see. Other than of ETNZ, there are few independent images/video available. If people have seen the challengers' boats sailing, then they certainly aren't saying much.
In New Zealand, we can only compare the AC75 with the half-size test boat. The smaller boat appears to be more forgiving than the AC75. Splashdowns were rare on the session last Tuesday on Course B in the Rangitoto Channel and again on Thursday on Course C or the North Head course. With the AC75 they appear to be more frequent, but ignoring the spectacular splash they create, most seem to have a minimal effect on speed - about the same as a regular keelboat of that size punching through the occasional wave.
The jury is still out on the scow versus skiff approach to hull design/concept. Between the Hawk and the Dolphin, there seems to be little difference, given they are both skiffs. They both take about the same time 1-2 secs to get foiling. The comment from the scow side is that they chose that direction to get clear of the water and onto the foils as quickly as possible. Given that the skiffs are inherently fast in that respect, it would seem that the scow teams have given the lift-off aspect too much weighting.
Once airborne, aero-drag becomes a big factor. We won't know until after the first America's Cup World Series in Cagliari whether there is a significant difference between the scows and the skiff, or not. From the 2013 America's Cup, we know that Oracle Team USA had an advantage over Emirates Team NZ with their better aerodynamic profile of the hulls and platform.
On Tuesday's sail Te Kahu (The Hawk) was doing plenty of tacking and gybing - mostly without touching the water at any stage.
Even going back and looking at the photo-sequences (shooting at three frames per second) there was usually no sign of water contact by the hull on the test boat. The key point of both manoeuvres seems to lie in the co-ordination of the raising and lowering of the foil arms and maintaining ride height.
The crucial part of the manoeuvre is the exit - provided the crew have made a fast entry and stayed high during the turn. Without satisfying those two prerequisites, the exit cannot work. The issue with the exit is removing the old foil from the water, as at some point it doesn't contribute to lift and is all drag. At that stage, you see the ride height dip, and if the dry tack/gybe is going to turn wet, that is the time it will happen.
The most obvious point of difference between the Hawk and the Dolphin is in the wing shape. That is to be expected as the number of wings and flaps are restricted under the AC75 class rule (as happened with daggerboards in the AC50 in the 2017 America's Cup). The restriction doesn't apply to development boats which can test in any design direction they decide and without restrictions on number.
The body language on the chase boat was a give away with Te Kahu (the Hawk), with some very intent gazing at the development boat with several of the design team packed into the bow. Obviously, they were looking for performance nuances that didn't jump out of the screen when reviewing the day's data. Tuesday's session, in particular, indicated that the team may have made some gains with the wing shape, flaps and control system. The flight height and tack/gybe behaviour appeared to be significantly different from Te Aihe (the Dolphin). Indications are that there is more to come.
As noted in my Saturday column for NZME/NZ Herald, Emirates Team New Zealand is an outlier in a number of areas from the Challenger group. One of these is in the use of their test boat. INEOS Team UK was first to launch with a small boat (28ft) which was designed to be hard to sail - and tested the crew. American Magic was next with The Mule - a 38fter like Te Kahu, it was designed to be a mini AC75, like the Kiwi boat.
We assume that The Mule is alive and well and will continue as a test boat like Te Kahu. Luna Rossa were third to launch and sailed their test boat a few times before it went into the shed, after which they launched their AC75. Only the Italians know what their strategy will be using a test boat, or if they are going to rely completely on their simulator, and then test on the AC75 with the restrictions inherent in that strategy.
Bear in mind that the class rules restrictions apply per AC75 not per campaign. So Luna Rossa (and all teams) get a new equipment quota with their second AC75, and may well believe they can work within that allocation to achieve their development needs. Obviously, they can compare results between their two AC75's in the simulator, and with wings and flaps, they can run different shapes and combinations per side to get even more comparison.
A point of interest in Cagliari will be whether the Kiwis put any of the new kit onto the AC75 and test that in a race situation, and similarly before the second event in Portsmouth.
After that, the only opportunity for a race comparison will be in December in the third round of the America's Cup World Series. That's a big gap, and the teams will need to be locked and loaded with their preferred configurations before that series - and should be just confirming their decisions before racing starts in the Prada Cup just over three weeks later.
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Good sailing!
Richard Gladwell
NZ Editor
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