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30 minutes ago, southseasbill said:

My guess is that the yellow colour is Dalts trolling sailing anarchy.

When there's a yellow arrow on the main pointing at something interesting, Dalt's trolling mastery will be complete... 

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It's pissing down outside and yes, we are back to Level 3. To all those moaning and bitching about it and calling the PM childish names, get a grip, we are the luckiest people in the world right

After many hours of consideration, a lot of in-depth research on the SA technical threads, extensive computational modelling and a few quick & dirty minutes in Photoshop, I have produced this anal

Yes, quite light but I didn't see all the afternoon's sailing, can only comment on later in the day, when Britannia 2 was running a #1 jib and foiling around no problem. They look quite quick at times

Posted Images

1 hour ago, enigmatically2 said:

I don't see the advantage of inflation. They can only put anything in the lower mainsail zone whether mechanical or inflation. If its in the lower section then having an inflatable solution would either not be adjustable whilst sailing or would require a lot of additional equipment to be able to adjust it. 

More likely two (semi-)rigid panels separated by mechanical or hydraulic devices I would have thought

Aerodynamics 

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1 minute ago, enigmatically2 said:

I think the aero between the two skins in the bottom and top zones is pretty messed up 

Agree.  Hence why they may want to improve it with inflated forms 

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1 minute ago, I ride bikes said:

Agree.  Hence why they may want to improve it with inflated forms 

Which would stop all air flow. Which they could do in those zones very easily if there was mechanical or hydraulic separation without all the difficulty of inflation

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25 minutes ago, enigmatically2 said:

I think the aero between the two skins in the bottom and top zones is pretty messed up 

What makes you think so?

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2 minutes ago, MaxHugen said:

What makes you think so?

Because it is between the 2 skins, with a mast in front of it sealing the gap, and loads of controls in there. What aero flow do you think is in there?

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17 minutes ago, enigmatically2 said:

Because it is between the 2 skins, with a mast in front of it sealing the gap, and loads of controls in there. What aero flow do you think is in there?

Zero.   Why should there be any airflow between the skins?

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1 hour ago, MaxHugen said:

Zero.   Why should there be any airflow between the skins?

Exactly, so why would having an inflatable between the skins be better for aero than mechanical hydraulics

(apologies if my comment about the aero being messed up was misleading, British understatement doesn't always export well)

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2 minutes ago, enigmatically2 said:

Exactly, so why would having an inflatable between the skins be better for aero than mechanical hydraulics

(apologies if my comment about the aero being messed up was misleading, British understatement doesn't always export well)

Ah, I must have missed something along the way. Don't know what the inflatable discussion was about obviously.

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tape.thumb.png.1e05b77f398b01df3faf796493c12810.png

 

What's this "tape" between the mast and the mainsail ? Could be the subject of this Class Interpretation ? 

Interpretation link: https://docs.google.com/a/acofficials.org/viewer?a=v&pid=sites&srcid=YWNvZmZpY2lhbHMub3JnfGFjMzYtb2ZmaWNpYWwtbm90aWNlYm9hcmR8Z3g6MzdiN2MzMTc0OTgyOWI3YQ

 

PS Frame from  this Justin Mitchell video (link https://www.youtube.com/watch?v=s1DZ-2KaAZQ)

 

 

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44 minutes ago, MaxHugen said:

Ah, I must have missed something along the way. Don't know what the inflatable discussion was about obviously.

Possible it could just be an air spring, perhaps pushing on a batten in opposition to a control line

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1 hour ago, enigmatically2 said:

Exactly, so why would having an inflatable between the skins be better for aero than mechanical hydraulics

(apologies if my comment about the aero being messed up was misleading, British understatement doesn't always export well)

Perhaps because it's lighter?

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Just now, jaysper said:

Perhaps because it's lighter?

But not by the time you have added all the pumps and gizmos to inflate it. Plus air pumps would add another reliability issue. #And if you don't have those on board then a fixed solution is simpler and no extra weight

 

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6 hours ago, enigmatically2 said:

But not by the time you have added all the pumps and gizmos to inflate it. Plus air pumps would add another reliability issue. #And if you don't have those on board then a fixed solution is simpler and no extra weight

 

So the other day we saw the poms manually inflating part of their wing with a external hand pump which is then removed from the boat for racing.

Seems to me that they (ETNZ) might be doing the same.

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6 hours ago, enigmatically2 said:

But not by the time you have added all the pumps and gizmos to inflate it. Plus air pumps would add another reliability issue. #And if you don't have those on board then a fixed solution is simpler and no extra weight

 

TNZ just use a compressor fitted to one of their chase boats to inflate the pockets in the upper portion of their mainsails.

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8 hours ago, Zaal said:

tape.thumb.png.1e05b77f398b01df3faf796493c12810.png

 

What's this "tape" between the mast and the mainsail ? Could be the subject of this Class Interpretation ? 

Interpretation link: https://docs.google.com/a/acofficials.org/viewer?a=v&pid=sites&srcid=YWNvZmZpY2lhbHMub3JnfGFjMzYtb2ZmaWNpYWwtbm90aWNlYm9hcmR8Z3g6MzdiN2MzMTc0OTgyOWI3YQ

 

PS Frame from  this Justin Mitchell video (link https://www.youtube.com/watch?v=s1DZ-2KaAZQ)

 

 

What supplied rigging would be chaffing at the foot of the mast?

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3 minutes ago, barfy said:

What supplied rigging would be chaffing at the foot of the mast?

I imagine with over 50 knots apparent wind chafe would be a constant issue, perhaps it just the sail chaffing the mast. 

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8 hours ago, Zaal said:

What's this "tape" between the mast and the mainsail ? Could be the subject of this Class Interpretation ? 

I'm guessing to damp vibration, the same reason we were seeing crew members "hugging" the base of the mast when towing without main.

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2 hours ago, jaysper said:

So the other day we saw the poms manually inflating part of their wing with a external hand pump which is then removed from the boat for racing.

Seems to me that they (ETNZ) might be doing the same. 

Seems to me a paintball air tank with a regulator on it would be a much easier way to do it on the water (and faster).

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12 minutes ago, Grrr... said:

Seems to me a paintball air tank with a regulator on it would be a much easier way to do it on the water (and faster).

and that would be a good way to decide any crossing protests !   if you can hit the give way boat the protest is upheld,  no paint no protest.

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42 minutes ago, Zeusproject said:

More pics of foils from today 

2889E679-1FDC-4B90-9EA8-8A775E55A895.jpeg

E98A8AFB-6533-4D7A-A23F-EC9AB18326C0.jpeg

749E5B64-7104-452B-B4EA-5A17D08F3236.jpeg

AE68308A-4006-40CC-994B-CC1F268A520A.jpeg

Those are some SERIOUSLY anemic looking foils.
I can only assume that they have a rig producing a shit tonne more power than the other teams. The alternative is that they will have no show of getting foil borne in light airs.

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48 minutes ago, Zeusproject said:

More pics of foils from today 

2889E679-1FDC-4B90-9EA8-8A775E55A895.jpeg

E98A8AFB-6533-4D7A-A23F-EC9AB18326C0.jpeg

749E5B64-7104-452B-B4EA-5A17D08F3236.jpeg

AE68308A-4006-40CC-994B-CC1F268A520A.jpeg

Any idea what's been attached to the port foil? Some kind of sensor I guess?

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1 hour ago, jaysper said:

Those are some SERIOUSLY anemic looking foils.
I can only assume that they have a rig producing a shit tonne more power than the other teams. The alternative is that they will have no show of getting foil borne in light airs.

Yes, they do appear to be pretty damn small foils relative to the others.  I wonder how much they plan to use their flap allowance (i.e. change flap size) to optimise for different  wind conditions.  As you say they may also have a more powerful/controllable rig.  

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2 hours ago, jaysper said:

Those are some SERIOUSLY anemic looking foils.
I can only assume that they have a rig producing a shit tonne more power than the other teams. The alternative is that they will have no show of getting foil borne in light airs.

Didn’t have many issues putting time on the others in the Xmas cup 

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On 1/26/2021 at 10:49 PM, enigmatically2 said:

How do you know it is fast? The seagulls haven't been calibrated with those on duty at the round robins

I calibrated one of those Gulls at 5.7 Teraflaps per Millennia (S.A. Units), so now we know she's fast...

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16 minutes ago, Lickindip said:

^^^ as a true 1 eyed ETNZ supporter ... "look how much higher they point with that fantastically trimmed sail in the 2nd and 3rd pics" :lol:

Still too much lift from those tiny wee foils. 

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3 hours ago, Lickindip said:

image.png.8fa6b9e53a19afca0a7d72907c21283f.png

reversed?

Wow finally convincing evidence it's possible! 

From the model I made, it was clear that in stronger winds, having a negative AOA at the top of the sail makes the boat faster even if it increases drag. I just wasn't sure how much could be achieved with active control at the top, so I limited the twist to 15 degrees from top to bottom.

This is the model prediction for 20 kts of wind. AOA at the top of the sail is around -5 degrees for reaching and upwind angles. It's all about lowering the center of effort.

image2-cr.thumb.png.d8457ff8d36647e8216ae7e2be0b13fc.png

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47 minutes ago, weta27 said:

 

DSC_5588.JPG

 

Pretty good effort depowering the main. I'm sure AM would have been happy to have this much control. Did the jump look accidental or maybe they were learning how to tame the boat if it wants to jump out after a messed up mark rounding or jibe?

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2 hours ago, HawkeyeNZ said:

Any idea what's been attached to the port foil? Some kind of sensor I guess?

Often they put cameras on, so they can see how the foils are behaving 

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3 hours ago, Lickindip said:

image.png.8fa6b9e53a19afca0a7d72907c21283f.png

reversed?

Active or passive? Looks pretty eased there. Veeeery interesting.

As above, how will 300kg of airbag buoyancy fit up there with skins squashed flat?  Isnt top 4m or so of main only allowed active control?

All will be revealed in someones book in 10 years time.

 

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3 minutes ago, minimumfuss said:

Active or passive? Looks pretty eased there. Veeeery interesting.

As above, how will 300kg of airbag buoyancy fit up there with skins squashed flat?  Isnt top 4m or so of main only allowed active control?

All will be revealed in someones book in 10 years time.

 

It's enough to force the top out, the rest of the sail will follow passively. Must be quite a contraption hidden between the skins to control the shape like that.

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4 minutes ago, southseasbill said:

The vid.

 

 

 

Geez, I'd need a change of undies after that!

So they are consistently running with the foil partially clear of the water.

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43 minutes ago, erdb said:

Did the jump look accidental

Yes, they were heading into the inner harbour (straight, level and in control, see preceding frame below) so it must have been a gust.

There was a decent westerly (?) coming down past North Head. All three boats had 'hairy' moments while I was watching.

EDIT: Justin saved me the explanation! Great video.

DSC_5586.JPG

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10 minutes ago, weta27 said:

Yes, they were heading into the inner harbour (straight, level and in control, see preceding frame below) so it must have been a gust.

There was a decent westerly (?) coming down past North Head. All three boats had 'hairy' moments while I was watching.

DSC_5586.JPG

Justin must be filming from near you on North head?

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24 minutes ago, southseasbill said:

The vid.

 

 

 

Great vid...

- Was it a practice maneuver.. (better to train for capsize avoidance methods than wait for it to happen). They are sailing a normal course with lower main just below center, then bear away aggressively (maybe 30deg) without much easing and hold direction, then as gust hits they round up aggressively to depower (no major sign of easing).

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23 minutes ago, southseasbill said:

Justin must be filming from near you on North head?

Yeah, we were on adjacent rocks :-)

His vid is more front-on and gives a much better picture of what happened.

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Another angle. A lot of wind angle change in that gust. You can see them bear away a bit to be safe. But still caught them out. 

 

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Yeah looked to be just a wired swirling gust. Just under North head??. Lucky they didn't get back winded

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Agree big gust from 17secs, you'd see that coming across the water up to 30secs prior..

Surely they'd see that and be in communication about it. They bear down only 2 seconds before it hits, which is why it looks like a controlled and planned (and well executed) training maneuver to me..

I think all teams will be trying low risk capsize avoidance maneuvers after AM incident.

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5 hours ago, Lickindip said:

image.png.8fa6b9e53a19afca0a7d72907c21283f.png

reversed?

Still a question mark.  Still photo, where is the video to show it was not just a header?

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7 minutes ago, rastro said:

Still a question mark.  Still photo, where is the video to show it was not just a header?

I wonder how fast they can invert the head, and if it can be used quickly enough for a avoidance capsize situation.

Northsails says:- By inverting the upper wing, the sail/wing is actually pushing backwards. It is also pushing to windward, reducing the sail’s tendency to heel the boat. The balance of the inversion and normal camber can in some conditions increase the boat’s performance.
https://www.northsails.com/sailing/en/2018/04/designer-spotlight-americas-cup-special-edition-developing-softwing-technology-for-2021-ac

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3 hours ago, erdb said:

Wow finally convincing evidence it's possible! 

From the model I made, it was clear that in stronger winds, having a negative AOA at the top of the sail makes the boat faster even if it increases drag. I just wasn't sure how much could be achieved with active control at the top, so I limited the twist to 15 degrees from top to bottom.

This is the model prediction for 20 kts of wind. AOA at the top of the sail is around -5 degrees for reaching and upwind angles. It's all about lowering the center of effort.

image2-cr.thumb.png.d8457ff8d36647e8216ae7e2be0b13fc.png

Certainly lowering the CE is good. But how are you calculating the resultant drag from the sail at -5°?

I can't calculate the L/D using XFoil with what is effectively a "reversed" sail compared to the mast rotation - it won't converge.

I'd still like to see more video footage, to look at whether this was just a momentary situation, or a useful strategy.

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1 hour ago, waterboy42 said:

Agree big gust from 17secs, you'd see that coming across the water up to 30secs prior..

Surely they'd see that and be in communication about it. They bear down only 2 seconds before it hits, which is why it looks like a controlled and planned (and well executed) training maneuver to me..

I think all teams will be trying low risk capsize avoidance maneuvers after AM incident.

Looks ,more like a header or a lull causing a header to me, and they bear away for that. Then it comes back and more. 

That was not a planned event

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8 minutes ago, Ex-yachtie said:

Here you go. From about 1:30. 

 

Wow agreed that is some voodoo sail shaping :blink:

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Getting big twist into the main and head, the leech has been loose fir a long time on that boat, the diagonal creases that run from the batten end at 45deg ish up toward the mast.

the loose material as the main unloaded in the big luff and the inverted head are signs of it.

it’s a big camber induced windsurf race sail. 

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25 minutes ago, weta27 said:

This seems to be different each day! Gradually tidying up ...

TRclew1.jpg

TRclew2.jpg

Great shots. :)

They are smoothing out the lumps slowly - good progression

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1 hour ago, nav said:

Great shots. :)

They are smoothing out the lumps slowly - good progression

Love to know whats happening inside there.

Have they now got a partial boom (horizontal lump about 1m above deck).?

Whats the conical thing poking out above the clew?

I can't think of a conventional sail equivalent

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ok here is my prediction ...

ETNZ are holding off putting in windows into their sails until just before the match ... there may be some sail shape / twin skin gap / mechanism that they are trying to hide for as long as possible

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5 minutes ago, Lickindip said:

ok here is my prediction ...

ETNZ are holding off putting in windows into their sails until just before the match ... there may be some sail shape / twin skin gap / mechanism that they are trying to hide for as long as possible

Then if the mechanisms fails for whatever reason, you  can always blame Windows. :-)

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1 minute ago, Kiwing said:

The leeches look much closer together. Is that true?

The gap looked much bigger when they were running the yellow version a couple of days ago, ie., in real light conditions.

Maybe it depends on the amount of camber they are trying to create?

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2 minutes ago, weta27 said:

The gap looked much bigger when they were running the yellow version a couple of days ago, ie., in real light conditions.

Maybe it depends on the amount of camber they are trying to create?

Thank you, good thought, will be interesting to test that hypothesis, but gut feel seems good. 

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6 hours ago, mako23 said:

I suspect there making a big pot of popcorn 

Not going out again after seeing American Magic today.!  :D

P.S. And I believe they are drafting a no thanks to AM as a tune up partner upon AM's exit

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@weta27 Sir, your photography has improved a lot since you started posting here. The constant giving you do selflessly to this forum is humbling. 

Thank you. 

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