Emirates Team New Zealand.

The_Alchemist · Feb 28, 2021

45Roller said:
Sure thing, some serious vibration in the wheel when turning too, DB always seemed to be really fighting it

Yes, they had some major problems with rudder control.

mako23 · Feb 28, 2021

Talking about the weather

It seems to me that Auckland’s weather has changed. Seems to be a lot cooler and slightly more windy. How long this will last haven’t got a clue. I wonder what other Jafa’s think

For non Kiwis

https://en.wikipedia.org/wiki/Jafa

strider470 · Feb 28, 2021

mako23 said:
For non Kiwis

https://en.wikipedia.org/wiki/Jafa

Ahahahah I didn't know!

barfy · Feb 28, 2021

Apterix said:
This to me is the awesome bit about having such an open design rule. And, having two very different expressions of the rule racing against each other in the final. We will, in the not too distant future, see what works and what doesn't

I agree..last cycle the foils were still pretty open, but the limiting cant angles stuck everyone close in one corner. I believe with almost unlimited cant the design box is much larger.

Apterix · Feb 28, 2021

The_Alchemist said:
I thought of saying "could" on the tacks, it all depends on the course. I doubt there would be any time that the higher course would require more tacks (assuming no wind shifts).

Just for grins, I plotted a 45 vs a 44 degree course on the current AC course:

View attachment 431640

edit: we were talking about upwind, I should not have added the downwind part to the plot.

Looking at the latest JM video (#257 Emirates Team NZ | 8 Days To America's Cup Match | 26 Feb 2021 - YouTube), in light winds it seems like ETNZ comes out of the tacks and gybes in a pretty low VMG mode to keep on the foils. They then take quite a while to build speed before trimming to a higher VMG mode (see huckery yellow lines added to The_Alchemists' elegant drawing). If ETNZ can't make up for VMG losses in manoeuvres with superior VMG once up to speed and trimmed, tacks/gybes could be a weakness that LR is able to exploit in light air, and ETNZ may end up doing more tacks/gybes. But, I figure the ETNZ designers have worked out that they will gain more than they lose across the predicted wind range.

MaxHugen · Feb 28, 2021

Apterix said:
NZ's foils are ~ half flap, which I assume is how they are able to make small foils fly in bugger all wind - albeit it with lots of trim and a massive drag penalty. Once they're up to speed they can decrease the trim and fly more efficiently. But, at what cost? How much distance will they give up in the tacks and gybes? Will they be able to point as high as LR?

This to me is the awesome bit about having such an open design rule. And, having two very different expressions of the rule racing against each other in the final. We will, in the not too distant future, see what works and what doesn't.

FYI, NZ's flaps are ~40% of foil chord.

Previously did a force comparison between NZ's foil size vs GB, which is roughly the same as LR. Despite requiring a bit more foil and flap angles, especially at lower boat speeds, NZ's foil had a higher lift/drag ratio from 20 knots to 60 knots.

Apterix · Feb 28, 2021

MaxHugen said:
FYI, NZ's flaps are ~40% of foil chord.

Previously did a force comparison between NZ's foil size vs GB, which is roughly the same as LR. Despite requiring a bit more foil and flap angles, especially at lower boat speeds, NZ's foil had a higher lift/drag ratio from 20 knots to 60 knots.

Nice - thanks for that - you add a lot to this forum Max. It's the low speed (<20 knots) stuff that worries me as ETNZ supporter. It may just be pre cup jitters, but it looks like ETNZ are slow around the corners in light airs. I hope the higher lift/drag ratio of NZ's foils make up for any low speed disadvantage.

weta27 · Feb 28, 2021

TR launching off Orakei, good breeze but no batwing

Ncik · Feb 28, 2021

On 2/26/2021 at 4:11 PM, Forourselves said:

Wow, just before 5mins that is some very slow foiling. Keeping it up at such a slow speed is tricky, not seen another team do it.

weta27 · Feb 28, 2021

TR in the back paddock. Good day for “unheard of” speeds???

Ncik · Feb 28, 2021

EYESAILOR said:
Unfortunately that is not the situation. The AC is governed by a deed of gift which in turn is governed by NY law. ETNZ may have a cast iron contract with the RNZYS but if Dalts tried to choose another YC, that would be in breach of the deed of gift. In legal terms, the cup cannot be given to another club by either ETNZ or RNZYS. It can only be removed by a valid challenge (or relinquished to prior club in specific circumstances...see deed)

The cup resides at the club which won the cup. The only loophole is that RNZYS could accept a challenge from Dalts club and then lose that challenge. But the challenging club would have to meet the deed of gift requirements as Allinghi found out when they tried to create a bogus challenging club and got sued in NY court.

They could always do a bogus AC in 6-12 months for minimum $$$ and deliberately lose to their chosen benefactor club in exchange for an ETNZ payday. As long as the other deed criteria are met, it is probably cheaper than lawyers fees.

uflux · Feb 28, 2021

weta27 said:
TR in the back paddock. Good day for “unheard of” speeds???

I guess too windy for LR... :mellow:

jaysper · Feb 28, 2021

Ncik said:
Wow, just before 5mins that is some very slow foiling. Keeping it up at such a slow speed is tricky, not seen another team do it.

Good for pre-starts presumably. Can use it to dodge Jimmy's hook.

They look to be seriously struggling for stability whilst they are doing it.

Presumably they have cranked up the main foil's angle of attack and are compensating like fuck with the rudder.

MaxHugen · Feb 28, 2021

Apterix said:
Nice - thanks for that - you add a lot to this forum Max. It's the low speed (<20 knots) stuff that worries me as ETNZ supporter. It may just be pre cup jitters, but it looks like ETNZ are slow around the corners in light airs. I hope the higher lift/drag ratio of NZ's foils make up for any low speed disadvantage.

There's a lot of "intelligent guesswork" on this forum as a whole... I notice a few YT channels that "analyse" the AC appear to use info gained from the forum.

I think you're right about NZ's performance through the turns in light air, particularly the tacks. I'm guessing that they need to get speed up on their narrow foils to compensate for speed decrease during the turn, so they tend to bear away slightly for a couple of seconds before and after a tack. LR have a bit of an advantage here, and probably gain a few metres over NZ.

Countering this, NZ most likely have a slightly higher acceleration to get back to max speed for the conditions, and this should neutralise LR's tacking advantage. Then it's back to VMG, where NZ have an edge through those extra sail area down low plus the ability to squeeze out max power due to the camber they can induce, and their lower-drag foils.

I think NZ will be OK even in the lower wind range.

MaxHugen · Feb 28, 2021

jaysper said:
Presumably they have cranked up the main foil's angle of attack and are compensating like fuck with the rudder.

You can tell... when they are sailing with little or no bow down pitch, it's to use more of the "Angle of Incidence" of the foils as AoA. (about +2° for NZ I think).