It will be interesting for sure, I saw a pic today where the kiwi foil actually looks like it's on the boat backward... I have no doubt they are using some different tactics with their foil design... if you believe what has been said they also have more advanced sail trimming systems...

Can't wait for it to start.

Yes, a lead change or two is nice to see, but rare. Again, like with formula racing in our sport, if you win the start, you win the race. Rare exceptions.

Despite all the commentary about Luna Rossa having the overall faster boat against Ineos, the one race that Ineos won showed that even a "slower" boat can control and win the race if they win the start.

The other two times when Ineos started out in front, it was amazing to watch LR climb higher and faster on port tack, and just plain pass Ineos with straight speed.

Since Ineos dominated the round robins, and even beat LR, It is amazing to see a reversal in fortunes for the finals. Either LR made some significant changes, or Ineos lost something. One thing even my non-racing wife noticed is that LR's crew were a bunch of determined machines out there, and that the boat just smoothed its way around the course, bow down but almost never splashing the hull.

I have to believe that NZ are shaking in their boots. Two weeks to get ready.

I watched the round robbin races between Ineos and LR. There were a number of close races with multiple lead changes. I think the difference in the finals, was that LR limited their errors to almost zero. They are a very calm boat. The AC final will be interesting, with the NZers not having much competition on the water to hone their sailing skills under pressure.

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segler said..
...that the boat just smoothed its way around the course, bow down but almost never splashing the hull.
...

This is something that keeps me wondering.
What is the reason for the bow-down (tilted towards front) sailing stance?
Do they get better VMG, does it have impact on the center of effort of the sail (mast tilted forward) or???

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ned321 said..

segler said..
...that the boat just smoothed its way around the course, bow down but almost never splashing the hull.
...

This is something that keeps me wondering.
What is the reason for the bow-down (tilted towards front) sailing stance?
Do they get better VMG, does it have impact on the center of effort of the sail (mast tilted forward) or???

They run a fair rake in the rig so when up to speed and bow down they are certainly not tilted forward, not sure on the rules but they may be able to change it readily.

The reason they sail bow down is because the foils are attached to the end of the canting arm with an angle of attack so they can actually take off; yes they have flaps but still need this AoA. As they are up to speed this AoA approaches very small angles and hence they go bow down. ETNZ have by far the smallest foils hence they probably have the highest static AoA of the foil on the arm; IE the reason they also look the most bow down when ripping.

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ned321 said..

segler said..
...that the boat just smoothed its way around the course, bow down but almost never splashing the hull.
...

This is something that keeps me wondering.
What is the reason for the bow-down (tilted towards front) sailing stance?
Do they get better VMG, does it have impact on the center of effort of the sail (mast tilted forward) or???

Yes, seeing the photo of the NZ boat I wondered about the same thing..

Could it be a way to better the aerodynamics of the hull and/or the airflow around the sail perhaps?
If boat is travelling at 3x wind speed, the apparent wind is always very forward in direction and the angle could be very low..

Perhaps at speed, the curious tablespoon shape of the NZ boat deck creates a venturi effect around the bottom of the sails hence bettering the sails efficiency..

Mozzy sails explains it nicely. The rules specify the height of the rotating mast foot relative to the foil cant axis. This no doubt was to equalise the sail centre of effort to righting moment amongst the teams. ETNZ's work around was to put the mast step on a pedestal and lower the deck. Apparently there's no restrictions on closing the gap. Sail power down low = more power for a given righting moment.

The mozzy sails video is on youtube but it has a double "_" in the web address and the seabreeze linker doesn't like it. Search for "ETNZ loophole!"

The America's cup rules are set by a collaboration between the Defenders and the Challenger of Record. Here's the NZ designer's take on it. "By opening the playing field we're playing to our strengths"


The word is that INEOS is going to throw the hat in the ring as Challenger of Record for the next event.

How is the 'Challenger of Record" decided if there are multiple challengers?

Ineos know now of course, that they won't be the Cup Holder. Italy and NZ could both decide to be the CoR, depending on who wins, and we won't know that until it's over.

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sailquik said..
How is the 'Challenger of Record" decided if there are multiple challengers?

Ineos know now of course, that they won't be the Cup Holder. Italy and NZ could both decide to be the CoR, depending on who wins, and we won't know that until it's over.

I suspect it's whoever gets in first.

The Brits must be suckers for punishment. They spent a lot of time & money coming up with a slow boat that was very difficult to get up and stay on the foil in the bottom end of the race wind range.

Well after losing the inaugural match in 1851 they challenged 16 times between 1871 and 1964. It would sort of water down the mystique if they ever won it back.

en.wikipedia.org/wiki/America's_Cup

Interesting, with one week on Saturday!

www.nzherald.co.nz/sport/americas-cup-2021-team-new-zealand-reveal-their-latest-weapon/44KC6RFH2CUSF42SGSCDK7GGB4/

An interesting article in their Sail design:
www.sailingscuttlebutt.com/2021/03/06/twin-skin-mainsail-hits-superstardom/

Double-skinned sails have been tried in our sport, too. Not practical for us, and too heavy. Our super-wide luff sleeve sails do indeed move in this direction.

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Ian K said..
Can't find much on "super cavitating foils with flaps" on the internet, however, as usual, someone's been there before.

eprints.utas.edu.au/11838/2/Pearce-whole.pdf
Ventilated Supercavitating Hydrofoils for Ride Control of High-Speed Craft
Bryce W. Pearce, B.Eng (Hons.) National Centre for Maritime Engineering and Hydrodynamics Australian Maritime College

We're going top have to find you a healthy R&D budget but I'd reckon there's another 10 knots in the AC75 format if top speed was the aim.

Supervised by local windsurfer Prof. Paul.... www.utas.edu.au/profiles/staff/amc/paul-brandner

Here's an interview with SailGP Japan captain Nathan Outteridge (Aus) commentator for the series.

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Ian K said..
These fellows have dug up some interesting lab tests. At 1.00 check the ventilation coming from a metre or more back in the wake down the centre of the tip vortex! They make an interesting proposition that cavitation is delayed on larger foils, less pressure drop in negotiating wider curves. Of course you need more power to drive a larger foil through the water. But the AC75s seem to have heaps of that to spare, even in 20 knots.

Here's another specific to AC75

12-15 knt forecast for today's first races, should be in both team's strong zones if the 'talk' is accurate! - maybe a touch high for LR... hopefully, some good racing coming up with the kiwis on top

Interesting racing today. Not much in it so far.

Once again, whosoever winneth the start, winneth the race. Very few exceptions.

On race one that little squeeze Prada tried at the start line lost them a lot of speed, and they never recovered. NZL had the momentum there and just sailed away from them. That's the only mistake I have seen Prada make since the round robins.

The race two start was classic, and both boats had full speed out of the start, Prada a couple seconds ahead.

50 knots around the top mark, they said. Amazing that they just kept it level and smooth through that transition. Just amazing. Practice makes perfect.

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segler said..
...

50 knots around the top mark, they said. Amazing that they just kept it level and smooth through that transition. Just amazing. Practice makes perfect.

At 19'28". They do 49.8 (Spaghetti) and 51.1 (Kiwi) at the exit of the gate to leg 4. They actually accelerate during the turn ... it is quite incredible.

Very closly matched boats and Teams...the start is critical. You feel NZ may have a tiny speed advantage downwind but not enough to really attack if they get behind. Should be a really interesting series.

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segler said..
50 knots around the top mark, they said. Amazing that they just kept it level and smooth through that transition. Just amazing. Practice makes perfect.

We'd have to assume they are showing us real time data transmitted from an onboard GPS. On the GPS forum we've got to believe it. I noticed ETNZ sitting on a steady 48-49 knots, for maybe even 10 seconds, on its way back down to the start box during pre race.

What were the anemometers on the start gates reading at this time? 12-13 knots? But wind readings are always hard to make sense of, they could've been in a gust. They are impressively slippery boats. What do you think they'd score for an Alpha ?

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Ian K said..>>>> What do you think they'd score for an Alpha ?

Great question Ian!
Does anybody know a crew member, could they be persuaded to try?

They're doing over 40kts square, and 50 as they bare off into the gybe.
The gybes look very tight, the 50m separation shouldn't be a problem.
Did anybody notice minimum speed? I'd guess it doesn't go below 40, they look powered up all the time. So I wouldn't be surprised by a low to mid 40. There was a speed graph, showing up leg and down leg speeds, but I didn't take much notice of the gybes.

An exciting first day of racing with only today as rest day.

Forecast isn't looking like much wind for the next day(s) and expect start delays and possible postponements.

Another situation to develop for Auckland is covid level hopefully to change to level 1 relative freedom where more courses open with the gusty shifty wind directions which can give more passing opportunities. Also spectators in the cup village and bars will do good business.

As a kiwi we wanted extra fast boat to dominate with boat speed but what we have is a sailing contest of two excellent teams where the start is crucial to get the first cross.

Yesterday the first race once the kiwis are comfortable in front they sail to the wind but the Italians are more match racers to cover and dictate tactics to the boat behind.

Come on kiwis & Aussie Glenn Ashby

All evo stevo on second day of racing. Seems like who wins the start has a big advange. Great to watch

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Steve Charles said..
All evo stevo on second day of racing. Seems like who wins the start has a big advange. Great to watch

Yeh the boats are too even in the conditions so far for either to make a clean pass just with boat speed, its going to take wind shifts, current or a mistake... that said so far it looks like when they are behind the kiwis can stay closer to LR so are more likely to be able to take advantage of a mistake.

Looks like it could be over or almost over by the time any decent breeze shows up too, bit of a shame really.

Anyone know why the AC boats don't keep both side foils down when they are having trouble staying up? I would have thought more foil equals less speed to fly or stay flying

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thedoor said..
Anyone know why the AC boats don't keep both side foils down when they are having trouble staying up? I would have thought more foil equals less speed to fly or stay flying

Drag, they want as little drag as possible to keep the speed up and keep the airflow over the sails and water flow over the one foil. As the kiwis demonstrated today once on the foil as little drag as possible is preferable - smaller foils, smaller jib. That was remarkable in both races today

The windward foil also contributes to the balance of the boat when it is out of the water.

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thedoor said..
Anyone know why the AC boats don't keep both side foils down when they are having trouble staying up? I would have thought more foil equals less speed to fly or stay flying

No righting moment with both foils set for lift. Can't power up. They have two down sometimes for stability in the turns. They can dial in negative lift if needed inside the turn.