Cup Spy April 12: Kiwis launch and sail straight out of the box
by Richard Gladwell/Sail-World NZ 12 Apr 2024 05:26 PDT
13 April 2024
Emirates Team New Zealand shore crew washes down the new AC75 base after her first sail - April 12, 2024 © Richard Gladwell- Sail-World.com/nz
Emirates Team New Zealand's new AC75 moved from first splash to first foiling tack in Auckland on Friday.
The accelerated sequence is the first time that the team has launched for the first time and sailed on the same day. Normally in a foiling America's Cupper, there is at least a tow test to check that foils and hydraulics are working correctly.
Quite why the Kiwis moved through the test sequence so rapidly is not clear, but regardless they have the distinction of being the first to sail an AC75 raceboat in the cycle of the 37th America's Cup. They also achieved their usual benchmark in a new foiling boat where their first tack is a dry one.
They did strike a very convenient weather window, after Auckland, was lashed with an equinoxial gale, causing serious flooding in many parts of New Zealand, and the delay of the start of the Three Kings Race by 24 hours.
While the gale abated to a mere 11-15kts, and shifted direction to an offshore breeze with flat seas, their late afternoon sail in fading light, was beset with passing rain squalls. Almost all of the Kiwis America's Cup launches have experienced rain in various quantities - said to be the tears of joy of ancestors according to Maori custom. The tradition started with the launch of KZ-7 in 1986, with Master of Ceremonies, Peter Montgomery, holding an umbrella to keep solo yachtswoman Dame Naomi James dry, while she christened Kiwi Magic.
The Kiwis latest America's Cup progeny is of the same genre as their 2021 America's Cup champion and isn't a major shift in design direction, unlike their second born Te Rehutai, which was very different from their first AC75 Te Aihe. That shift was not surprising given that their design team had to commit to the final lines and get those to their build team, and before the benefit of any performance data from their first AC75.
Prior to today's launch, Te Rehutai has undergone radical surgery to explore some options afforded by Version 2 of the AC75 Class Rule.
As expected, and seen in Alinghi Red Bull Racing's new AC75, the Kiwi design team have gone for an slimline hull - to improve the aerodynamic characteristics around the bow, while staying with the required minimum volume required by the class rule.
The low bow and sheerline then leads in a very aerodynamic way into the crew pits of which there are four per side, and there is obviously no intention for the sailing crew to run across the cockpit between tacks.
The "plowshare" bow first seen on Te Rehutai remains, but in a more subtle form and will come into play to avert a serious nosedive after a flight control error/malfunction. The entry of the canoebody at the forefoot does have an initial fullness to provide additional buoyancy in the bow - useful to help the bow quickly clear any contact with the awkward Bacelona seastate.
The most striking feature if the AC75 is her stern treatment where the beam does not appear to be carried right into the aft end of the canoebody. And in a step back into the more traditional days of yacht design, the AC75 has pinched waterlines in her afterbody.
While unusual it is clearly a move to reduce hull drag at the lighter end of the wind range.
The previous design theory, shared by several design teams, was that the hull would ride on its leeward chine and centreline bustle - presenting like a pair of catamaran hulls, with lower drag, before lifting onto the foils. The flat section is still there at the aft end of the Kiwi boat, it is just not as wide.
Our guess is that the computer simulations, and this cycle, feeding off plenty of good AC75 performance data, have shown that it is better to let the foils do the heavy lifting - a task made easier by reduced stern hull drag.
Anyone who has followed an AC75 in light airs will see that the back end is very sticky - and that means more drag.
With the designs for the last America's Cup, there was some talk of "ground effect" (similar to the compressed air bubble under a low flying jet fighter), and with the reduction of flat underbody in the aft end, ETNZ may be working on the basis that "there is no ground -effect".)
That being said have they also looked at turbulence as the spent breeze exits underneath the hull, and also the rig?
Remember that this is the team who responded to the ban on wind tunnel testing with a radical landyacht, and in the course of that project would have learned a lot, in an extreme design environment about minimising aero-drag - all of which is applicable to the AC75 thinking. Another spinoff from the landspeed record project is that it should have enabled ETNZ to refine and tune their design and performance prediction software. So that while wind tunnel testing is prohibited, the Kiwis have the next best thing, or better in their performance software.
The 11-15 kt breeze today was well up on the minimum wind range of 6.5kts and while the AC75 was able to lift easily onto her foils, it was not a good light air test of the new hull shape.
The skeg is noticeably deeper than that on Te Rehutai, and is similar to that seen on Alinghi Red Bull Racing at their reveal.
Emirates Team New Zealand launched the new AC75 with legacy foils from Te Rehutai - so nothing new to see in that department. The foils were different from one side to the other ie they were not matched. In view of our observation about the design objectives of the hull, and not using that to assist so much with the lift-off, it will be interesting to see what the Kiwis produce as their next generation foil design.
There are some interesting features in the back end of the cockpit floor, which were not that obvious in the darkness of the haulout.
A spy task for another day.
AC37 Joint Recon Team Report:
Emirates Team New Zealand - AC75 - Boat 3 - Day 1 - April 12, 2024 - Auckland
[AC37 Joint Recon team: Sam Thom and Andrew Burgess]
Today ETNZ launched their America's Cup race boat, Boat 3 AC75. After a long morning of waiting for the weather to clear up enough, the shed doors opened and the boat rolled out into the sunshine for the first time. Sporting the same paint job as "Te Rehutai" did for testing early in this cycle, you could have mistaken B3 for Te Rehutai, however changes were very noticeable.
The team rolled the boat out of the shed at 12:22. Proceeding into the forecourt in front of the base, then proceeded to start the necessary calibrations required. As they completed a 360 spin with the boat for compass calibrations, recon got its first good look at the boat from all angles and while it has roots in the design of Te Rehutai, there have been significant design changes.
ETNZ shore crew worked quickly and effectively to step the rig of Boat 3, with all systems seeming to run smoothly during the stepping process. The Base was alive with everyone coming down to watch the boat splash for the first time. A host of people quickly sprang into action on the boat once it was secured on the dock, starting a range of system checks and calibrations. We see for the first time "cyclors" joining the sailing crew running through essential dock checks. Seen for the first time now was the configuration of the sailors onboard the yacht. With 2 cyclor pods aft of the helm and trimmer on each side of the yacht. Spending roughly an hour running over on the dock, the team departed to start some tow testing down the harbor. Docking out at 15:40.
In a moderating westerly breeze, the team completed a long foil tow heading east down the harbor and towards the "Back Paddock", towing at times with speeds in the high 30's and low 40's. Dropping off the tow, Boat 3 rounded up, and Chase 1 came alongside to start working on hoisting sails for the 1st time. Spending roughly 1 hour working on hoisting both mainsails and a J4, the shore crew returned to the chase boat, and the Sailing team started getting the boat sailing upwind.
With a very controlled speed build and takeoff, Boat 3 was officially flying under sail and started accelerating upwind. Looking in control, the team went into a few tacks, completing them fully foiling. Being late in the day and quickly running out of light, the team stopped sailing after just 10 minutes and began getting the sails down. This ended with a slight delay as they had trouble getting the port mainsail off the lock and had a man up the rig working on it for quite some time, eventually getting it sorted; the team towed back towards the base in the dimming evening light and hit the dock just after sunset at 18:20.
AC37 Joint Recon had an interview with Peter Burling to talk about the new boat after the sailing session.
Crew: Sailing: Peter Burling, Nathan Outteridge, Andy Maloney, Blair Tuke. Cyclors: Louis Crosby, Louis Sinclair, Marius Van Der Pol, Simon Van Veltooven
Session Statistics: Emirates Team New Zealand - AC75 - Boat 3 - Day 1 - April 12, 2024 - Auckland
- Weather: 17-20° Rolling showers
- Wind Strength: 11-15kts
- Wind Direction: Westerly
- Sea State: 0.4mts
- Crane In: 1430hrs Dock Out: 1540hrs
- Dock In: 1825hrs Crane out: 1900hrs
- Total Tacks: 3 - Fully foiling: 3; Touch & Go: 0; Touch Down: 0
- Total Gybes: 0 - Fully foiling: 0; Touch & Go: 0; Touch Down: 0
Additional Images: