Salty Seacock

Emirates Team New Zealand.

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1 hour ago, JALhazmat said:

Because zero side skirt  to actually seal in any air passing under the hull to create a pressure differential between top and bottom surface. 

It has a central skirt because the rules won’t allow side skirts. And on two B2 boats it is thick enough to be an aerofoil in itself. So it only can achieve half at best of what may be possible. When heeled (either way) it has the makings of a tunnel effect. That is not to say that there isn’t any WIG effect at all.

Competitions can be won by the smallest of advantages, especially if the central skirt also softens landings, facilitates takeoffs and provides additional lateral resistance and balance at low speeds, especially with the ‘sprit sail up. And if you ooch back and forth between “tunnels”, you might increase AWS on the upper sails at least.

FBADE976-1E13-406F-9C72-5A96CA64AD22.jpeg

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16 minutes ago, Priscilla said:

Oh the humanity a double reefed Piedy bloody millennials I suspect.

1812524627_DSC_2083.thumb.JPG.3db6ef3d59cb9b18c64e7b1c1f77f980(1).jpeg.75baf5ab13c6584844c00f7159c1c209.jpeg

 

One helluva sail number

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3 hours ago, eurochild said:

 

Anyway, question - have the teams been spotted doing pre start drills? Possibly one of the things being hidden on those trips out behind the islands? Or kept for the sim?

There was a video that had GB and NZ in that I wondered if both of them were doing that sort of drill a few days ago. I almost mentioned it at the time. Lots of odd turns going on

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10 hours ago, Rennmaus said:

Paywall, but anyway, Heaven help!


America's Cup whistleblowers Tom Mayo and Grant Calder say they feared for their safety after Grant Dalton branded them 'spies'

https://www.nzherald.co.nz/business/americas-cup-whistleblowers-tom-mayo-and-grant-calder-say-they-feared-for-their-safety-after-grant-dalton-branded-them-spies/FRLGNAOAPIXUXQERWFDEIBCEXE/

Just read the thing with "Bypass Paywalls". Phew, this is belonging to worst journalism I've ever encountered, straight out of Trump's new media handbook. No evidence, unfounded accusations disguised with question marks, and victim playing. Ouch.

If you changed the name of the paper to Womans Day, everything falls into place in terms of the quality of churnalism...

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1 hour ago, kiwi39 said:

 

Why would you want a body that doesn't want to fly ? you'd just have more downfoil to support on the foils .. and that'd be more drag. 

 

NO you are only thinking about drag.   extra load on the foil == more power available and that power is > the drag .  Down-force on the hull will make it go faster! 

!!

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3 hours ago, Priscilla said:

Beauty is in the eye of the beholder...

AC75TeRehutaiDraftCadV1.thumb.png.d58ee12ec89ddae27cbe1a535bb4da40.png

Hmm maybe not...

Ac75_Ineos_RBS_Launch_Bow1_16102020.thumb.jpg.5a2830fc164da1c19fc1deeffa48f3af.jpg

Don't  let the paint fool you, stand beside me when you measure my size...

 

 

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3 hours ago, Priscilla said:

Beauty is in the eye of the beholder...

AC75TeRehutaiDraftCadV1.thumb.png.d58ee12ec89ddae27cbe1a535bb4da40.png

Hmm maybe not...

Ac75_Ineos_RBS_Launch_Bow1_16102020.thumb.jpg.5a2830fc164da1c19fc1deeffa48f3af.jpg

Don't  let the paint fool you, stand beside me when you measure my size...

 

 

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1 hour ago, kiwi39 said:

It'd be interesting to see a cross section of the hull between the crewpods and the centreline.

I'm willing to bet that when the boat is  bow down it'd show an aerofoil section. 

I'm not saying that WIG is there to sustain flight - rather to aid takeoff and help lift the hull and minimise foil drag once airborne. 

Why would you want a body that doesn't want to fly ? you'd just have more downfoil to support on the foils .. and that'd be more drag. 

It's quite amusing that a lot of people on here are describing a hovercraft effect .. hovercraft create a contained cushion of high pressure air through the use of fans .... 

I just don't get the obsessing over using the hulls for lift. They have foils. They're actively depowering. Why on earth would you fuck around trying to get lift with the least controllable part of the platform?

 

I think the hull shapes are designed around a dozen factors that are more important than lift

 

 

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3 hours ago, Priscilla said:

Beauty is in the eye of the beholder...

AC75TeRehutaiDraftCadV1.thumb.png.d58ee12ec89ddae27cbe1a535bb4da40.png

Hmm maybe not...

Ac75_Ineos_RBS_Launch_Bow1_16102020.thumb.jpg.5a2830fc164da1c19fc1deeffa48f3af.jpg

Don't  let the paint fool you, stand beside me when you measure my size...

 

 

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1 hour ago, kiwi39 said:

It'd be interesting to see a cross section of the hull between the crewpods and the centreline.

I'm willing to bet that when the boat is  bow down it'd show an aerofoil section. 

I'm not saying that WIG is there to sustain flight - rather to aid takeoff and help lift the hull and minimise foil drag once airborne. 

Why would you want a body that doesn't want to fly ? you'd just have more downfoil to support on the foils .. and that'd be more drag. 

It's quite amusing that a lot of people on here are describing a hovercraft effect .. hovercraft create a contained cushion of high pressure air through the use of fans .... 

I just don't get the obsessing over using the hulls for lift. They have foils. They're actively depowering. Why on earth would you fuck around trying to get lift with the least controllable part of the platform?

 

I think the hull shapes are designed around a dozen factors that are more important than lift

 

 

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7 minutes ago, RMac said:

I just don't get the obsessing over using the hulls for lift. They have foils. They're actively depowering. Why on earth would you fuck around trying to get lift with the least controllable part of the platform?

 

I think the hull shapes are designed around a dozen factors that are more important than lift

 

 

Yeah like the enormous flappy thing that they spend all their time trying to get to behave like the perfect wing.

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4 minutes ago, astro said:

Looks like Mt Warning in the background.

That be the Tweed River?

Yeah was thinking the same.....

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1 hour ago, Kate short for Bob said:

Why?  To generate more lift that they have little control over?

Ground effect is pretty much self regulating isn't it?

It's not like the hull is actually going to generate enough of it for the boat to simply fly away...

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5 minutes ago, Boybland said:

Ground effect is pretty much self regulating isn't it?

It's not like the hull is actually going to generate enough of it for the boat to simply fly away...

But once flying you actually want to get as close to the water as you can.  Ground effect would prevent that.  The only advantage I can see with different hull shapes is to help get it OFF the water not to stay ABOVE it.  Once in the air the foils and the sails are what is controlling height.  

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1 minute ago, Kate short for Bob said:

But once flying you actually want to get as close to the water as you can. 

Agree. Drag and the keel are two good reasons  to fly low 

 

2 minutes ago, Kate short for Bob said:

Ground effect would prevent that.

 Strongly disagree. The hull will sit happily in ground effect at whatever height the pilots choose. Ground effect is not a solid barrier.

 

4 minutes ago, Kate short for Bob said:

Once in the air the foils and the sails are what is controlling height.  

Agreed.  ... Who ever said that the hull was controlling ride height ?? 

 

14 minutes ago, Boybland said:

Ground effect is pretty much self regulating isn't it?

Definitely 

14 minutes ago, Boybland said:

It's not like the hull is actually going to generate enough of it for the boat to simply fly away...

Correct ... It will however help support it's own weight , requiring less foil lift ... negative flap on the foils is a very real drag reduction option. 

 

The thing to remember here ... is that we're all guessing - and in lieu of actual facts from the teams, we're really just expressing our opinions as to whats actually going on. 

I'm more than happy to stand corrected if the facts show otherwise. 

Its certainly interesting to hear peoples opinions as to what's going on ...

 

 

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3 minutes ago, kiwi39 said:

Strongly disagree. The hull will sit happily in ground effect at whatever height the pilots choose. Ground effect is not a solid barrier.

That's where you are misunderstanding "ground effect".  The distance at which it comes into effect on an aeroplane is a very narrow range.  You don't have an ability to change that as the distance is a factor of the wing design.  For the same reason it is a pain in the butt for pilots of light aircraft it would be for those controlling a boat.  You don't have any control and are stuck in this narrow range of distance from the ground.  You either cross your controls to stall the wing or you hope that your speed drops off before the runway ends.  Neither of those actions are good for sailing!

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9 minutes ago, kiwi39 said:

The thing to remember here ... is that we're all guessing - and in lieu of actual facts from the teams, we're really just expressing our opinions as to whats actually going on. 

I'm sorry but some of us are not guessing when it comes to ground effect.  I've experienced it when piloting a plane and was extremely motivated after one instance to find out what the theory was.

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1 minute ago, Kate short for Bob said:

I'm sorry but some of us are not guessing when it comes to ground effect.  I've experienced it when piloting a plane and was extremely motivated after one instance to find out what the theory was.

You are, however guessing when it comes to whats going on with the boat. 

How many hours flying do you have under your belt ??  PPL I'm guessing ? 

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4 hours ago, kiwi39 said:

I’d give my left gnad to see the CFD models of how much lift these hulls produce when they’re airborne in ground effect. 

Unfortunately, they have already rejected my offer of the same.  Maybe they'll accept yours?

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42 minutes ago, kiwi39 said:

You are, however guessing when it comes to whats going on with the boat. 

I'm not guessing.  Go check out the theory and the physics that explains ground effect and show us how these hull shapes generate it.  Let alone to any advantage.  

Also ground effect only happens in specific environmental conditions as well.  Conditions over which you have no control.

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Anyone who has flown, even as a passenger,  has experienced it first hand. It is particularly noticeable when you come in on a bumpy descent, you get to a certain altitude level, when the wheels are just off the ground, and the plane suddenly becomes more stable and seems to float, and the engines are throttled back, because of the extra lift.

There are any number of links for those that can be bothered to look. Here is one:

https://www.flightliteracy.com/ground-effect-on-takeoff/

No one is saying that ground effect will hold an AC 75 fuselage off the water, just that it should help somewhat. It is the extent of the somewhat that is interesting and unfathomable, but surely must exist and could be maximised?

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1 hour ago, Kate short for Bob said:

But once flying you actually want to get as close to the water as you can.  Ground effect would prevent that.  The only advantage I can see with different hull shapes is to help get it OFF the water not to stay ABOVE it.  Once in the air the foils and the sails are what is controlling height.  

"Ground effect would prevent that."  Don't think it's relevant at all. If you look at the shape of the underside of any of the hulls, it does not fit an aircraft wing's profile. Aspect ratio is all wrong too, 0.5 compared to an aircraft's 20+ or thereabouts. I doubt you would get any "wing-in-ground" effect at all.

The hull design considerations would probably be (in no specific order):

  • Efficient Take-off
  • Maximise Laminar Airflow to Sails
  • Minimise Drag, both Parasitic (form) and Induced

IMO. :)

[Edit] I agree with a comment that if it could produce a bit of down force, it would assist RM.  This is an enormous issue for these boats, which is why they are forced to depower as much as they do. Perhaps it's why I often measure the hull AoA at around -2° ?

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32 minutes ago, Sidecar said:

No one is saying that ground effect will hold an AC 75 fuselage off the water, just that it should help somewhat. It is the extent of the somewhat that is interesting and unfathomable, but surely must exist and could be maximised?

But only if you shaped the hull like an air foil i.e. wing.  I think Max has summed up the design elements quite well.

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Can we stop with the ground effect bs.  I'm just assuming but I recan these boats are doing the same as the last cup. Using the drag to develop righting moment / power.  The bow down trim is driving the hull back down to the water. Giving the ability to power up the boat more. I believe team NZ have a shorter rudder too so we're not seeing as such a bow down trim. But it's there . 

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5 hours ago, Kate short for Bob said:

Just check out the explanation for ground effect.  It was a phenomena identified in aircraft particularly low wing aircraft.  It describes the phenomena where an air foil eg a wing which is horizontal to the ground produces vortexes that provide additional lift causing the plane to float.  They only provide lift when the wing is within a certain distance of the ground.  

The hulls of these boats are not that shape.  Their shape is not to sustain flight but to aid the transition between displacement mode and flight.

We have gone over this discussion for pages and pages in the past.  There are several components to ground effect, none of us know the real answer when it comes to these hulls.  Some are very adamant about it not being possible, some think it has a little effect.  Similar discussions to lift from the hull.

One very real fact is that many of the B 2 designs show much more stable flight than the B1.  Ward even discussed how some of the hulls are directing airflow for more stability while foiling.  

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23 hours ago, Varan said:

She sure is pretty.

5 hours ago, Priscilla said:

Oh the humanity a double reefed Piedy bloody millennials I suspect.

1812524627_DSC_2083.thumb.JPG.3db6ef3d59cb9b18c64e7b1c1f77f980(1).jpeg.75baf5ab13c6584844c00f7159c1c209.jpeg

 

 

No Seagull to see how fast she is going, looks to be holding the boat under tow off pretty well.

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50 minutes ago, The_Alchemist said:

One very real fact is that many of the B 2 designs show much more stable flight than the B1.  Ward even discussed how some of the hulls are directing airflow for more stability while foiling.  

Its almost as if they're flying on some sort of magic cushion. now WHAT could that be ... :D

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16 minutes ago, kiwi39 said:

Its almost as if they're flying on some sort of magic cushion. now WHAT could that be ... :D

I think you'll find it is the improved control and configuration of three elements - the sails, the foils and the rudder.  

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7 hours ago, Kate short for Bob said:

Just check out the explanation for ground effect.  It was a phenomena identified in aircraft particularly low wing aircraft.  It describes the phenomena where an air foil eg a wing which is horizontal to the ground produces vortexes that provide additional lift causing the plane to float.  They only provide lift when the wing is within a certain distance of the ground.  

The hulls of these boats are not that shape.  Their shape is not to sustain flight but to aid the transition between displacement mode and flight.

Phenomenon is the singular. If you believe it was more than one phenomenon adjust your grammar

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8 hours ago, breezie said:

I agree with ZERO ground effect. !

Why?..... because the designers would try to avoid any such effect. if anything they would seek down-force on the hull

The power available is proportional to the righting moment. any lifting of the hull will reduce the available power 

particularly when going full noise they will seek as much aerodynamic down force as they can obtain

 

That would fit with a low pressure area under the hull vaporising water.

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9 hours ago, kiwi39 said:

to maximise ground effect 

No, to maximise end plating the hull to the water.

something utterly different 

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9 hours ago, Sidecar said:

It has a central skirt because the rules won’t allow side skirts. And on two B2 boats it is thick enough to be an aerofoil in itself. So it only can achieve half at best of what may be possible. When heeled (either way) it has the makings of a tunnel effect. That is not to say that there isn’t any WIG effect at all.

Competitions can be won by the smallest of advantages, especially if the central skirt also softens landings, facilitates takeoffs and provides additional lateral resistance and balance at low speeds, especially with the ‘sprit sail up. And if you ooch back and forth between “tunnels”, you might increase AWS on the upper sails at least.

FBADE976-1E13-406F-9C72-5A96CA64AD22.jpeg

You show us a wing i ground effect that is sealed by a central skirt. 
 

keyword are  sealed and central. 
 

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7 hours ago, kiwi39 said:

Agree. Drag and the keel are two good reasons  to fly low 

 

 Strongly disagree. The hull will sit happily in ground effect at whatever height the pilots choose. Ground effect is not a solid barrier.

 

Agreed.  ... Who ever said that the hull was controlling ride height ?? 

 

Definitely 

Correct ... It will however help support it's own weight , requiring less foil lift ... negative flap on the foils is a very real drag reduction option. 

 

The thing to remember here ... is that we're all guessing - and in lieu of actual facts from the teams, we're really just expressing our opinions as to whats actually going on. 

I'm more than happy to stand corrected if the facts show otherwise. 

Its certainly interesting to hear peoples opinions as to what's going on ...

 

 

So ground effect that you all think is about making the boat fly and lift  early. 
is based on the underside containing a low pressure zone sucking downwards

how is that a desirable feature and at sub 20 kts forward speed ( as we are told they take off at) with no way of directing and holding the airflow under the boat ( no side skirt) how can it be happening? You need accelerated airflow to create a pressure differential 

 

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17 minutes ago, JALhazmat said:

So ground effect that you all think is about making the boat fly and lift  early. 
is based on the underside containing a low pressure zone sucking downwards

how is that a desirable feature and at sub 20 kts forward speed ( as we are told they take off at) with no way of directing and holding the airflow under the boat ( no side skirt) how can it be happening? You need accelerated airflow to create a pressure differential 

 

No. You might be thinking of formula 1, where the underfloor is low pressure. 
ground effect in this context is high pressure underneath and lower pressure over the top of the aerofoil 

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3 hours ago, Kate short for Bob said:

I think you'll find it is the improved control and configuration of three elements - the sails, the foils and the rudder.  

Actually it’s probably a combination of all the above including ground effect. 

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12 minutes ago, kiwi39 said:

No. You might be thinking of formula 1, where the underfloor is low pressure. 
ground effect in this context is high pressure underneath and lower pressure over the top of the aerofoil 

Lol. So explain how you are are creating this magical switcheroo.. at sub 20 kts with a boat that weight 6.5 ton. In 6-8 kts of true wind.

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Oh god please let there be real sailing news soooon!!!:blink:

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On 11/28/2020 at 4:00 PM, barfy said:

Maybe not concave :

11.6 At any transverse cross-section through the hull lower surface:
(a) no horizontal line shall cut the cross-section more than twice; and

It is concave.

They are making 100% maximum use of the exclusion around the arm hinges.

Quote

Parts of a cross-section within cylindrical regions of length 4.000 m and diameter 1.250 m centred on each
foil cant reference point, and whose axes are aligned with the foil cant axes, are excluded from this Rule.

 

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7 hours ago, hoom said:

It is concave.

They are making 100% maximum use of the exclusion around the arm hinges.

 

Prove it with pictures.  

I think what you are seeing is an optical illusion.  The square sides on the stern look to dip lower then the curved flare of the bow.  But the high points of the bow curve and the edges of the stern are not in the same cross section.  

In other words: It gives the illusion of a concave shape when viewed from the front, but the high and low parts are not next to each other in the same cross section.

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Alchemist, you are right that the rules don't allow a cat or Tri shape. But the bustle to flat bottom is concave. And this when the boat heels either way it does create a "tunnel". I'm not sure of how much lift it could provide because they certainly say F1 wings stop working above the max AWS these boats see, but I guess the weight brothers got off the ground with less AWS. But will still be minute amount of.lift. 

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10 hours ago, kiwi39 said:

Actually it’s probably a combination of all the above including ground effect. 

For the benefit of trying to understand wtf you are on about can you at least explain the difference between “wing in ground effect” and “ground effect” because I am very sure you are mixing the two up and assuming they are the same.  Increasing downforce and increasing lift are not the same. 

as they offer two distinctly different outcomes.

also how you expect to swap the high/low pressure over. physics suggests that it’s a lost cause but dying to see you prove the theory wrong. 

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17 hours ago, MaxHugen said:

"Ground effect would prevent that."  Don't think it's relevant at all. If you look at the shape of the underside of any of the hulls, it does not fit an aircraft wing's profile. Aspect ratio is all wrong too, 0.5 compared to an aircraft's 20+ or thereabouts. I doubt you would get any "wing-in-ground" effect at all.

The hull design considerations would probably be (in no specific order):

  • Efficient Take-off
  • Maximise Laminar Airflow to Sails
  • Minimise Drag, both Parasitic (form) and Induced

IMO. :)

[Edit] I agree with a comment that if it could produce a bit of down force, it would assist RM.  This is an enormous issue for these boats, which is why they are forced to depower as much as they do. Perhaps it's why I often measure the hull AoA at around -2° ?

Agree. Aspect ratio of a hull is terrible......modern parlance, "worst wing ever"

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On 11/20/2020 at 2:45 PM, Xlot said:

In keeping with aero design nomenclature, can we call the fat foil arm sections “spats” as in fixed undercarriage wheel fairings?

How can drag induced by the landing gear be reduced? - Aviation Stack  Exchange

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4 hours ago, Kate short for Bob said:

Does your ground effect work upwind as well as downwind?  

Yep. Relative airflow ... apparent wind.

are you going to tell me that the  wind downwind  is up the chuff and flowing from stern to bow ? 

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Are you going to explain how ground effect works? 
 Clue it’s not with high pressure under the lower surface.. 

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There is a whole other thread for this.....

0E9F371F-5030-4AEB-9CC2-F5C40F0C7E89.gif

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3 hours ago, JALhazmat said:

For the benefit of trying to understand wtf you are on about can you at least explain the difference between “wing in ground effect” and “ground effect” because I am very sure you are mixing the two up and assuming they are the same.  Increasing downforce and increasing lift are not the same. 

as they offer two distinctly different outcomes.

also how you expect to swap the high/low pressure over. physics suggests that it’s a lost cause but dying to see you prove the theory wrong. 

In an aviation context, wings lift upwards - and in formula one, their lift vector acts downwards ("downforce"). 

In a formula one context, ground effect is low pressure under the car which "sucks" the car down and produces downforce. 

Ground Effect in an aviation context is different .. in aviation wings lift upwards (with the exception of the tailplane which balances the couple of weight force acting through the CofG and Lift Force acting through the CoL) When an aerofoil with its lift vector acting upwards approaches a surface running parallel to it's high pressure side, a ground effect forms which is approximates to the distance from the surface to the freestream airflow.  This distance varies dependant on the shape of the underside of the aerofoil, ambient air temperature and pressure, and dewpoint. 

When An aerofoil with its force vector acting upwards approaches  this distance from the surface, it's said to be in ground effect. The high pressure underneath it forms the "cushion" previously mentioned. 

I contend  that the shape  longitudinal cross sectional shape of ETNZ (as the best example) forms an aerofoil with its force vector acting upwards. in particular the flat sections both the underside and upper surface of the "tail" of the hull body that sits in between the crew pods tends to suggest this.  I also think that this contention still holds true even when the boat is foiling in bow down trim. 

Interestingly  wing in ground effect was mentioned in a recent INEOS youtube 

The reality is that - like everyone else on here this is my best guess as to whats going on. The only way to really know whats going on would be if we could see the CFD modelling. 

Any defender or challenger team lurkers on here must be laughing their arses off at our expense. 

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3 hours ago, Rasputin22 said:

How can drag induced by the landing gear be reduced? - Aviation Stack  Exchange

They certainly look like wheel spats .. 

I'm super curious as to what they contribute to the overall physics model 

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10 minutes ago, JALhazmat said:

Are you going to explain how ground effect works? 
 Clue it’s not with high pressure under the lower surface.. 

its depends which way your aerofoil is oriented - and which way your lift vector points :D 

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32 minutes ago, kiwi39 said:

The reality is that - like everyone else on here this is my best guess as to whats going on. The only way to really know whats going on would be if we could see the CFD modelling. 

 Any defender or challenger team lurkers on here must be laughing their arses off at our expense. 

This.

The reality is that even with “the worst wing ever” at 5 metre span (excluding any additional benefit from the foil arms), AC75’s operate entirely within in the 0-40% wingspan WIG zone.

Box kites, sky surfboards and frisbees are just a few examples of objects, which, despite their lousy wing spans all derive some aeronautical benefit outside the WIG zone,  more if they could stay well within the zone.

FI racing cars also have lousy wing spans..... And a terrible foil shape due to their other functional necessities.

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37 minutes ago, kiwi39 said:

In an aviation context, wings lift upwards - and in formula one, their lift vector acts downwards ("downforce"). 

In a formula one context, ground effect is low pressure under the car which "sucks" the car down and produces downforce. 

Ground Effect in an aviation context is different .. in aviation wings lift upwards (with the exception of the tailplane which balances the couple of weight force acting through the CofG and Lift Force acting through the CoL) When an aerofoil with its lift vector acting upwards approaches a surface running parallel to it's high pressure side, a ground effect forms which is approximates to the distance from the surface to the freestream airflow.  This distance varies dependant on the shape of the underside of the aerofoil, ambient air temperature and pressure, and dewpoint. 

When An aerofoil with its force vector acting upwards approaches  this distance from the surface, it's said to be in ground effect. The high pressure underneath it forms the "cushion" previously mentioned. 

 I contend  that the shape  longitudinal cross sectional shape of ETNZ (as the best example) forms an aerofoil with its force vector acting upwards. in particular the flat sections both the underside and upper surface of the "tail" of the hull body that sits in between the crew pods tends to suggest this.  I also think that this contention still holds true even when the boat is foiling in bow down trim. 

Interestingly  wing in ground effect was mentioned in a recent INEOS youtube 

The reality is that - like everyone else on here this is my best guess as to whats going on. The only way to really know whats going on would be if we could see the CFD modelling. 

Any defender or challenger team lurkers on here must be laughing their arses off at our expense. 

Right so now you are conceding that it isn't "ground effect" but something else.  However I will contend that the designers are trying to minimise the lifting effect when the boat is in full flight i.e. they are trying to avoid ground effect or wing in ground effect.  I think in the same video it was mentioned that they want to get as close to the water as possible without touching it.

Of course they want to get flying as quick as possible hence the bustles and skegs but they are designed to minimise drag (through reduced contact area on the water) - ground effect isn't possible at that point nor are they trying to attain it!

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7 minutes ago, Kate short for Bob said:

Right so now you are conceding that it isn't "ground effect" but something else. 

No. Re-reading what I wrote , I definitely did not say ("concede") that it isn't ground effect. 

Actually I firmly believe that WIG is what they're attempting. Not a WIG that completely supports the weight of the boat for sure, but a WIG nonetheless - one that assists takeoff and assists flight. 

Just as aside, you never answered my previous question about how many flying hours and what pilots licence you hold. I'm guessing a low hour (<100) PPL ?

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7 minutes ago, kiwi39 said:

Just as aside, you never answered my previous question about how many flying hours and what pilots licence you hold. I'm guessing a low hour (<100) PPL ?

What does that have to do with my argument against ground effect?  

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Was driving in to work this morning and ETNZ were out relatively early... 8:30am already off North Head.

Not sure if the regular photogs caught anything - my potatovision is not really worth the upload, but they appeared to have code zero up, and sail in a pretty quick displacement mode for quite some time... it felt easily windy enough to have been foiling, but there was no spray that I could see...

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Had a quick look from Narrow Neck but could only see LR and INEOS training in the channel. ETNZ may have been out off the Bays, but it was a bit hard to be sure through the murk.

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Just to liven things up here's the most recent video I could find.  Luna Rosa in a good breeze and a brief glimpse of ETNZ.  

 

 

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In other news I took the kids to the Spark 5G Race Zone on the weekend. Some notes:

  • The PR spin for 5G was solid - pretty sure we have 5g to thank for wind and buoyancy amongst other things.
  • In all seriousness, there is some 5G smarts delivering ETNZ realtime weather data for all courses apart from Course E, making this course less advantageous.
  • There is a near 360 video experience that puts you on the boat. It's quite a ride, and you get a great sense of the speed ("48 knots") and shear physicality of sailing that boat.
    • It includes very clear footage of B1's internal boom and hydraulic leech system, showing it snapping shapes through manoeuvres.
    • The gap between the two skins, at the window cuout, is much larger than I was expecting given the photos.
    • The team have little curved cutouts/backrests on the outward side of the trenches that they back themselves into in order to stay table during racing.
    • I wish this video was posted to YT as it is better than anything I've seen online.
  • There is a boat builder app, that whilst simple, does explain tradeoffs for things like bulb-size, anhedrals etc - it might be more about making a good narrative, but I suspect the principles are correct.
  • The racing simulator was most impressive. The graphics are as good as any recent console could deliver (appears to be PC running an Unreal engine). The gulf looks as good as photo realistic, the sailors have been motion captured, and overall this looks much better than it deserves to considering it is for just this event.
    The setup includes both a helm with foot pedals to raise/lower each foil, and a second station with two joysticks for controlling both flaps and elevator - this allows for controlling attitude as well as height. The flight controller was far too complex and sophisticated for this environment - the guide even suggested leaving it to resort to auto. I could see no one master the flight controller it at all. :-) The helm and foils provided more than enough to juggle. It was built using ETNZ's physics models, and it feels pretty accurate, and also pretty difficult.

download.thumb.jpg.d0219566e000bcfe9f899d197fe51628.jpg

The company responsible for the simulator and boat builder app have some great images and videos here, worth checking out :-)

https://buildmedia.com/work/spark-5g-race-zone

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The consistency of their ride height is next level. Very impressive 

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Due diligence... bird on post (upper left), not a seagull20201129_171254.jpg.1aa1587b214480f24c5ef9c3f9a7fce3.jpg

Bird lower right.. seagull

20201129_171351.thumb.jpg.1d83e2568d47fe11bb1cba2c59a33ccd.jpg

Yep, looked slow.

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1 minute ago, Varan said:

Due diligence... bird on post (upper left), not a seagull

Bird lower right.. seagull

Yep, looked slow.

Sorry for forgetting the seagulls in the timestamps :-D

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57 minutes ago, mikenz2 said:

From an hour ago:

 

Well certainly not impressive sailing overall: off foils, bouncy ride height, looking slow. But how would the others do in such light airs? Does anyone on the scene know how the other teams do in similar winds? 

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1 hour ago, Apterix said:

Just to liven things up here's the most recent video I could find.  Luna Rosa in a good breeze and a brief glimpse of ETNZ.  

 

 

LR looking pretty damn fast and stable in that vid

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2 minutes ago, zillafreak said:

Well certainly not impressive sailing overall: off foils, bouncy ride height, looking slow. But how would the others do in such light airs? Does anyone on the scene know how the other teams do in similar winds? 

I can tell you there was next to no wind out there this morning. That is very impressive. 

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2 minutes ago, zillafreak said:

Well certainly not impressive sailing overall: off foils, bouncy ride height, looking slow. But how would the others do in such light airs? Does anyone on the scene know how the other teams do in similar winds? 

does anyone realize they will have to maneuver in the pre starts... Perhaps training for such instances. Straight lines are fun and all but the boats will need to do some strange maneuvers at times

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5 minutes ago, zillafreak said:

Well certainly not impressive sailing overall: off foils, bouncy ride height, looking slow. But how would the others do in such light airs? Does anyone on the scene know how the other teams do in similar winds? 

It appeared like ETNZ were almost hunting out light winds today for their testing. All the other teams have headed to areas with better breeze. And now with 13 knots they sailed back into the harbour and have dropped all the sails. 

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10 minutes ago, Afrayedknot said:

does anyone realize they will have to maneuver in the pre starts... Perhaps training for such instances. Straight lines are fun and all but the boats will need to do some strange maneuvers at times

Maneuver in the pre starts? Strange maneuvers? I had no idea! I thought they just let each other pass with a hand wave and blew kisses. I am so glad you are here to inform us! Fucktard level comment there newbie.

 

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Just now, zillafreak said:

Maneuver in the pre starts? Strange maneuvers? I had no idea! I thought they just let each other pass with a hand wave. I am so glad you are here to inform us! Fucktard level comment there newbie.

 

I guess you never watched Bermuda :mellow:

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5 minutes ago, mikenz2 said:

It appeared like ETNZ were almost hunting out light winds today for their testing. All the other teams have headed to areas with better breeze. And now with 13 knots they sailed back into the harbour and have dropped all the sails. 

Agreed - as noted above their speed this morning was definitely well under what the wind would have produced - it felt like they were sailing deliberately very high, or in a mode that almost felt they were using flaps to maintain stability while not climbing up...

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1 minute ago, zillafreak said:

Maneuver in the pre starts? Strange maneuvers? I had no idea! I thought they just let each other pass with a hand wave. I am so glad you are here to inform us! Fucktard level comment there newbie.

 

At least he is not chasing shadows like you are.

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7 minutes ago, Kate short for Bob said:

At least he is not chasing shadows like you are.

Turned out not to be shadows eh Kate :D  Or do I need to show you again?

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On 11/29/2020 at 9:50 AM, kiwi39 said:

Why would you want a body that doesn't want to fly ? you'd just have more downfoil to support on the foils .. and that'd be more drag.

It does seem counter-intuitive, but a major issue in using "full power" is in keeping the boat upright. As they have no way to substantially increase RM, such as a canting keel etc, they have to balance the boat in the transverse plane.  Balancing it in the longitudinal plane by using downforce on the stabilator is not a problem, apart from being somewhat "delicate".

That's why they often have to "depower" the rig a lot, through the use of twist - which also lowers the CE.

There is no shortage of lift from the foil, so if the hull is able to exert some downforce, that would be very beneficial to RM, so they can utilise more of the sails' forces.

I've wondered why the boats are mostly sailed bow down... perhaps to add hull downforce?

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27 minutes ago, meanermachine said:

It's a very meme-able bit of footage!

Just wish I'd recorded a bit longer so I could make it perfectly loop :D

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2 hours ago, mikenz2 said:

From an hour ago:

 

Nice on Mike.  Good to see some footage being posted again.  It looks like they might be practicing some low wind range starting manoeuvres with one of the chase boats acting a surrogate competitor.  Do you have any thoughts about what they were up to?    

 

 

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2 hours ago, mikenz2 said:

From an hour ago:

 

I recall a comment about not seeing any pre-start practice... they did a very well controlled quick left-right maneuver from about 0:26, impressive in the light air.  I could see them using that as a feint, perhaps to force the opponent off the foils?

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i thought it might be how they could jam the competitor outside the start box and still have room to get to the line themselves

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3 minutes ago, phill_nz said:

i thought might be how they could jam the competitor outside the start box and still have room to get to the line themselves

Could do... there was a very entertaining "pre-box" encounter in an AC35 race, but I don't remember the teams involved.

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4 hours ago, Apterix said:

Just to liven things up here's the most recent video I could find.  Luna Rosa in a good breeze and a brief glimpse of ETNZ.  

 

 

From this video, it's simple to conclude that LR were only doing 40kts, but ETNZ was doing just over 60kts. 

No need for the challengers to waste their time in March.

My cat counted the frames, so it must be true. 8)