Salty Seacock

Emirates Team New Zealand.

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4 hours ago, mikenz2 said:

Some haul out photos from Wednesday:
P1130433.thumb.JPG.fd29a3cd65039d42b5e8bd02caed3749.JPG

Awesome pics! Many thanks for your efforts.    Interesting that NZ is still evaluating their foil profiles.

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1 hour ago, MaxHugen said:

Interesting that NZ is still evaluating their foil profiles.

As long as they stay within the foil quota TNZ has until March 2021 to keep on evaluating.

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Hmmm... that "join" between the foil arm and the foil - where it goes from black to white - would that be a "wing fence" to help prevent ventilation?

image.thumb.png.9675b91f7239e7ee30b92c5658e014a8.png

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29 minutes ago, MaxHugen said:

Hmmm... that "join" between the foil arm and the foil - where it goes from black to white - would that be a "wing fence" to help prevent ventilation?

image.thumb.png.9675b91f7239e7ee30b92c5658e014a8.png

I think it would need to be bigger, I’m not sure If a fence is even needed to stop ventilation. I suspect that when water at speed hits the top of the bulb were it intersects with swing arm., it’s pushed upward. This creates a constant flow of water flowing up the arm. Hence no need to worry about ventilation 

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45 minutes ago, MaxHugen said:

Hmmm... that "join" between the foil arm and the foil - where it goes from black to white - would that be a "wing fence" to help prevent ventilation?

image.thumb.png.9675b91f7239e7ee30b92c5658e014a8.png

Interesting observation, Max. Not sure if it's a fence, but it definitely looks as if the junction between the foil arm and foil stem has certainly evolved its shape. There used to be a series of stepped reductions in cord length on the arm end faring. See pic, from Set. 2019. That now seems to be evened out.

image4.jpg

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7 minutes ago, mako23 said:

I think it would need to be bigger, I’m not sure If a fence is even needed to stop ventilation. I suspect that when water at speed hits the top of the bulb were it intersects with swing arm., it’s pushed upward. This creates a constant flow of water flowing up the arm. Hence no need to worry about ventilation 

A paper I read about ventilation on V foils had a diagram of a surface piercing foil at around 45°, which showed water pushing up on the downward side, and air being sucked down on the upward side.   Most images I've seen of actual fences do seem larger... except perhaps those of Hydroptere's:

image.png.447acaba80a0490a28210d7a3b1749a1.png

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10 minutes ago, Sailbydate said:

Interesting observation, Max. Not sure if it's a fence, but it definitely looks as if the junction between the foil arm and foil stem has certainly evolved its shape. There used to be a series of stepped reductions in cord length on the arm end faring. See pic, from Set. 2019. That now seems to be evened out.

Thanks for to 2019 pic... quite a difference, not only in the foil arm/stem but also a bulb, foil at aft end now...!   Have to find a pic of AM's foil arm geometry - can't ask MikeNZ to work his great "spy magic" since they mothballed B1.

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10 minutes ago, MaxHugen said:

Thanks for to 2019 pic... quite a difference, not only in the foil arm/stem but also a bulb, foil at aft end now...!   Have to find a pic of AM's foil arm geometry - can't ask MikeNZ to work his great "spy magic" since they mothballed B1.

I'll just pop back in my time machine....

28th July, it's a smooth transitionP1110696.thumb.JPG.333e667eae7321edcdbd8974656a5b00.JPG

Also note the dihedral on the rudder foils vs Te Aihe's horizontal foils
P1110697.thumb.JPG.20bd02a8fdc7274cb414c208f9efc28d.JPG
 

Edited by mikenz2
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4 minutes ago, mikenz2 said:

I'll just pop back in my time machine....

28th July, it's a smooth transition

Also note the dihedral on the rudder foils vs Te Aihe's horizontal foils
 

You da Man... with a Wayback Machine! :D    Thanks!

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Just now, MaxHugen said:

You da Man... with a Wayback Machine! :D    Thanks!

Gotta have a back catalog of photos, never know what you guys are going to ask for :lol:

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3 minutes ago, mikenz2 said:

Gotta have a back catalog of photos, never know what you guys are going to ask for :lol:

Sweet!

Your next mission, should you decide to accept it, Mr Mike, is to sneak into ETNZ's design office, and record how they determine their design strategies.

This post will self-destruct in 10 seconds.

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2 hours ago, MaxHugen said:

Awesome pics! Many thanks for your efforts.    Interesting that NZ is still evaluating their foil profiles.

You can tell the foil profile being used on each foil from that pic? 
 

bulb type, yup? Planshape?  yup

foil profile? How? 

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5 minutes ago, mikenz2 said:

Gotta have a back catalog of photos, never know what you guys are going to ask for :lol:

Can your excellent Time Machine edit unwanted effects too, Mike? 

Be nice if you could go back and delete those pesky container cranes from your excellent vids! :)

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1 minute ago, Sailbydate said:

Can your excellent Time Machine edit unwanted effects too, Mike? 

Be nice if you could go back and delete those pesky container cranes from your excellent vids! :)

I wish! I just need to keep them distracted enough that the yellow crane doesn't create a building that blocks my view!

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48 minutes ago, MaxHugen said:

A paper I read about ventilation on V foils had a diagram of a surface piercing foil at around 45°, which showed water pushing up on the downward side, and air being sucked down on the upward side.   Most images I've seen of actual fences do seem larger... except perhaps those of Hydroptere's:

image.png.447acaba80a0490a28210d7a3b1749a1.png


image.png.4e4c093db2773d904ef610084831d8c7.png

This amazing boat is widely different than an AC75 in more ways than obvious ways. The facts that these foil arm don’t have a bulbed wing at the bottom must make them work completely different. These wings are more  likely to suffer from ventilation. The fact that there at 45 degrees must also change there ventilation profile. However my knowledge of ventilation makes me concerned in making any definitive statements. 
 

ps your photo might be showing fences considering how their repeated 

 

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1 minute ago, JALhazmat said:

You can tell the foil profile being used on each foil from that pic? 

foil profile? How? 

Well, perhaps I should not have said foil profile... I was thinking about the "blended bulb & foil" versus the the previous buld arrangement.

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7 minutes ago, mako23 said:


image.png.4e4c093db2773d904ef610084831d8c7.png

This amazing boat is widely different than an AC75 in more ways than obvious ways. The facts that these foil arm don’t have a bulbed wing at the bottom must make them work completely different. These wings are more  likely to suffer from ventilation. The fact that there at 45 degrees must also change there ventilation profile. However my knowledge of ventilation makes me concerned in making any definitive statements. 

 

Reminds me of the old hydrofoil motor launch, Manu Wai, which was used on the Waiheke Island/Auckland run a million or so years ago in Auckland. Do we need to remind ourselves that hydrofoils are not new tech?

Screen Shot 2020-10-09 at 8.12.24 PM.png

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5 minutes ago, mako23 said:


image.png.4e4c093db2773d904ef610084831d8c7.png

This amazing boat is widely different than an AC75 in more ways than obvious ways. The facts that these foil arm don’t have a bulbed wing at the bottom must make them work completely different. These wings are more  likely to suffer from ventilation. The fact that there at 45 degrees must also change there ventilation profile. However my knowledge of ventilation makes me concerned in making any definitive statements. 

 

Yeah, I was stunned when I first saw Eric Tabarly's Hydroptere. Athough Sailrocket holds the sailing speed record, it can only sail on one tack, so to me, the H is still king! Reached some 56 knots before again proving multihulls are most stable upside down.

With both NZ and AM canting their foils to the extent that they "surface pierce", I suppose that ventilation was of some concern?

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16 minutes ago, MaxHugen said:

Yeah, I was stunned when I first saw Eric Tabarly's Hydroptere. Athough Sailrocket holds the sailing speed record, it can only sail on one tack, so to me, the H is still king! Reached some 56 knots before again proving multihulls are most stable upside down.

With both NZ and AM canting their foils to the extent that they "surface pierce", I suppose that ventilation was of some concern?

Having the outer tip of the foil piercing the water will increase ventilation chances. Ventilation is air being sucked down the foil and it can’t be happening at the tips,  if they don’t pierce the surface. ( I know you know this fact but other readers might not know this) Ventilation can still happen via the swing arm. The fact that ETNZ foil is constantly piercing the water it’s not happening by chance. They wouldn’t be doing this unless there was real performance increases. 
The reality it is a very complex phenomenon way above my pay grade or understanding by an extreme margin. In the end you’re guess is good as mine. However it’s likely your guess is better

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Guillaume Verdier designed Ultime, Gitana 17 isn't too far behind hydroptere - doing it on foils, but quite differently.

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19 minutes ago, Sailbydate said:

Reminds me of the old hydrofoil motor launch, Manu Wai, which was used on the Waiheke Island/Auckland run a million or so years ago in Auckland. Do we need to remind ourselves that hydrofoils are not new tech?

Screen Shot 2020-10-09 at 8.12.24 PM.png

Can’t get a better picture by any chance....I want to see if there fences on those foils....anyway very good picture

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2 hours ago, MaxHugen said:

would that be a "wing fence" to help prevent ventilation?

No, they're spray deflectors.

There are a bunch of videos where you can see they are nearly always above the waterline while foiling & the new, more defined ones seem to do a very good job while above water.

As with spray deflectors in other applications, more spray/drag when they get immersed though.

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23 minutes ago, mako23 said:

 

Can’t get a better picture by any chance....I want to see if there fences on those foils....anyway very good picture

Yeah. She had foil fences. Max speed was only 36 knots or so though.

Here's a video link of her in Sydney. Don't know if she's still operational.

https://www.youtube.com/watch?v=759A774qf68

 

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51 minutes ago, Sailbydate said:

Yeah. She had foil fences. Max speed was only 36 knots or so though.

Here's a video link of her in Sydney. Don't know if she's still operational.

https://www.youtube.com/watch?v=759A774qf68

 

Great Video Popeye ...yes definitely fences or spray deflectors  ..,thanks much appreciated 

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1 hour ago, mako23 said:

The fact that ETNZ foil is constantly piercing the water it’s not happening by chance. They wouldn’t be doing this unless there was real performance increases. 
 

Whereas a few months ago when ETNZ were sailing lower and LR had the foil piercing the surface at times, that was of course slower!

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11 minutes ago, enigmatically2 said:

Whereas a few months ago when ETNZ were sailing lower and LR had the foil piercing the surface at times, that was of course slower!

Wtf I never said that, and I can’t make comments taking into consideration statements made by someone months ago. To be honest I’ve seen the Brit boat come in for a bashing, but not so much LR. 
Also LR might of started with tip piercing foils and then tested other ones to make a valid comparison. Also it could also be the case for some boats with bigger bulbs, tip piercing doesn’t work so well. It’s a extremely complicated situation with only the syndicates having a better idea. All I can do is speculate

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1 minute ago, enigmatically2 said:

Wasn't you that said it mako, didn't mean to imply it was, sorry.

It just struck me as funny that's all

No problem at all, however there is an ounce of truth some kiwis do slag of other syndicates what ever they do. 

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2 hours ago, Sailbydate said:

Reminds me of the old hydrofoil motor launch, Manu Wai, which was used on the Waiheke Island/Auckland run a million or so years ago in Auckland. Do we need to remind ourselves that hydrofoils are not new tech?

Not new tech but difficult to argue a lot of attention and development has been put in the area lately (in parallel with much better tools and computation power for CFD). Not sure they would have the same foils or even concept for the hydroptere now. As for powerboat, they care less about minimizing drag to the extreme.

Looking at ETNZ foiling mode, really close to the surface at time, one wonders if the next move is not towards "skipping" foils on the surface like sailrocket instead. It might be the best bet to overcome cavitation and increase speed even further for next cycle. Might be tricky to get foiling and would work best on flat seas.

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8 minutes ago, Lakrass said:

Not new tech but difficult to argue a lot of attention and development has been put in the area lately (in parallel with much better tools and computation power for CFD). Not sure they would have the same foils or even concept for the hydroptere now. As for powerboat, they care less about minimizing drag to the extreme.

Looking at ETNZ foiling mode, really close to the surface at time, one wonders if the next move is not towards "skipping" foils on the surface like sailrocket instead. It might be the best bet to overcome cavitation and increase speed even further for next cycle. Might be tricky to get foiling and would work best on flat seas.

I’m intrigued by the concept of “skipping foils” , I have very little knowledge of sailrocket. So I’m at a disadvantaged compared to some anarchists who know a lot more about this boat. Do you have any idea how a foil skipping helps ? I’ll be fascinated with what you have to say. 
maybe cavitation takes time to build up and if your foil pierces the surface you reset the clock ?or could there be something different about water in the fist six inches of depth. 

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1 hour ago, Sailbydate said:

Yeah. She had foil fences. Max speed was only 36 knots or so though.

Here's a video link of her in Sydney. Don't know if she's still operational.

https://www.youtube.com/watch?v=759A774qf68

   

I remember her well, in Auckland and Sydney. Did the run to Manly aboard her. There is an extensive history of Manu Wai's chequered career in an old issue of Fast Ferries. Seems she was still operational and looking fo a raison d'être in 2001.  http://www.classicfastferries.com/cff/pdf/cff_2001_8.pdf  This link for the whole magazine. Manu Wai story starts on page 4.

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4 minutes ago, mako23 said:

I’m intrigued by the concept of “skipping foils” , I have very little knowledge of sailrocket. So I’m at a disadvantaged compared to some anarchists who know a lot more about this boat. Do you have any idea how a foil skipping helps ? I’ll be fascinated with what you have to say. 
maybe cavitation takes time to build up and if your foil pierces the surface you reset the clock ?

Maybe wrong term as the foil is not actually skipping but here are some illustration from below and sailing, front float is skipping the surface.

Sailrocket.jpg

hqdefault.jpg

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I think the problem is still that whilst for a power boat or speed record attempt you can largely ignore the time taken to get on the foils at the start, and how easy it is to stay on them through manoeuvers , that isn't true for the AC. Better to spend more time on the foils and improve VMG once you are up than get that little extra top speed I think. Especially so for ETNZ since the average wind speed for her racing is likely to be lower

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9 minutes ago, Lakrass said:

Maybe wrong term as the foil is not actually skipping but here are some illustration from below and sailing, front float is skipping the surface.

Sailrocket.jpg

hqdefault.jpg

That's right, the port float flies, front float (which has the rudder!) skims, while the "hull" is lifted by the foil to starboard which also counters the lateral force of the wing. Another pic, showing the supercavitating foil, labelled (1):

image.png.4fda7ce7fb0e1e7120d550ece12bb739.png

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22 minutes ago, MaxHugen said:

 

That's right, the port float flies, front float (which has the rudder!) skims, while the "hull" is lifted by the foil to starboard which also counters the lateral force of the wing. Another pic, showing the supercavitating foil, labelled (1):

image.png.4fda7ce7fb0e1e7120d550ece12bb739.png

Yes I agree that item 1 is the foil. The black pontoons act as planing hulls with only the front one in the water when speed is up. A close up of item 1 would be interesting, however I doubt this foil is skipping.  Also being so thin it could of delayed cavitation to a higher speed and not super captivated 

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16 minutes ago, mako23 said:

Yes I agree that item 1 is the foil. The black pontoons act as planing hulls with only the front one in the water when speed is up. A close up of item 1 would be interesting, however I doubt this foil is skipping.  Also being so thin it could of delayed cavitation to a higher speed and not super captivated 

The foil is supercavitating as mentioned on their website: http://www.sailrocket.com/node/288.  Interesting diagram showing how the foil, besides providing lift, counters the wing:

image.png.a5b3944e6b357e07feacc733fb73d67c.png

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2 hours ago, mako23 said:

I’m intrigued by the concept of “skipping foils” , I have very little knowledge of sailrocket. So I’m at a disadvantaged compared to some anarchists who know a lot more about this boat. Do you have any idea how a foil skipping helps ? I’ll be fascinated with what you have to say. 
maybe cavitation takes time to build up and if your foil pierces the surface you reset the clock ?or could there be something different about water in the fist six inches of depth. 

Sail rockets foil didn’t skip, it was fully submerged, if it wasn’t the entire thing would flip. As it was the only thing providing an opposing force to the wing 

 

the pods/floats were the bits that skimmed/skipped. When at full speed the pod under the base of the wing was actually completely clear leaving the front, the rear and the base ventilating foil the only points of contact 

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55 minutes ago, JALhazmat said:

Sail rockets foil didn’t skip, it was fully submerged, if it wasn’t the entire thing would flip. As it was the only thing providing an opposing force to the wing 

 

the pods/floats were the bits that skimmed/skipped. When at full speed the pod under the base of the wing was actually completely clear leaving the front, the rear and the base ventilating foil the only points of contact 

On their website they state that there foil was supercavitation capable. I havent seen any close up shots showing the profile of this foil. Do you have any information on this ??

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42 minutes ago, mako23 said:

On their website they state that there foil was supercavitation capable. I havent seen any close up shots showing the profile of this foil. Do you have any information on this ??

This pic shows the flat aft section on the V shaped foil.

image.png.d004af715fac8630eb745ba8e522c770.png

This site has some other good pics too, if interested: http://www.yachtingworld.com/blogs/elaine-bunting/half-plane-half-boat-6339

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1 hour ago, mako23 said:

On their website they state that there foil was supercavitation capable. I havent seen any close up shots showing the profile of this foil. Do you have any information on this ??

Other than conversation with Paul, no.

other than others on here confirming what I have said and Paul said, about it being a base ventilating foil, no 

the reason you haven’t seen close up shots of it is that none of us that were shown it were going to go against the request not to take pictures. 
 

 

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33 minutes ago, MaxHugen said:

This pic shows the flat aft section on the V shaped foil.

image.png.d004af715fac8630eb745ba8e522c770.png

This site has some other good pics too, if interested: http://www.yachtingworld.com/blogs/elaine-bunting/half-plane-half-boat-6339

Those photos are from initial launch in Cowes.

the foil picture is 100% not what was used to set the record, in shape or length. 

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1 minute ago, JALhazmat said:

Those photos are from initial launch in Cowes.

the foil picture is 100% not what was used to set the record, in shape or length. 

Bugger! Did you find a pic of the one used?

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I had posted this info in the NYYC thread a while back.  With all of the SR2 discussion above, I will re-post it:

On 10/3/2020 at 11:32 AM, P Flados said:

I was very interested in the Sail Rocket project from the start and followed it closely. 

When the SR2 foil subject came up, I remembered that there was minimal details shared by the team at the time.  I very much appreciated the "reverse engineering" effort by Speer & Drela in the BDN thread (From post 8883 - BDN post).

I also found another SR2 item from December of 2012.  It is not nearly as deep as the BDN thread, but it has good pictures.  Similar to the post 8883 disclaimer, I think this item was never confirmed to be accurate by anyone connected to the SR team.     https://chevaliertaglang.blogspot.com/2012/12/clearing-50-knot-gate-hydrofoil.html

 

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9 hours ago, MaxHugen said:

Hmmm... that "join" between the foil arm and the foil - where it goes from black to white - would that be a "wing fence" to help prevent ventilation?

image.thumb.png.9675b91f7239e7ee30b92c5658e014a8.png

Do you watch any videos of the boats out practising?

Like this.... 

 

Notice anything happening at the 'foil arm fence'? Looks like a fire hose got turned on right, that's what they are trying to keep from getting any higher up the arm.

As for the whole 'supercavitating discussion', forget it, not gonna happen, spinboy doesn't even know what it means. Sure if they get to 50+ knots the foils will be likely be cavitating like crazy.....but that ain't supercavitaion :lol:

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32 minutes ago, MaxHugen said:

Bugger! Did you find a pic of the one used?

No because he hasn’t ever given permission

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18 minutes ago, P Flados said:

I had posted this info previously.  With all of the SR2 discussion above, I will re-post it:

Thanks for that!  I found Mr Speer's analysis very interesting... especially "Sailrocket uses a base ventilated section for its main foil."  If I understand what he is saying, the foil was somehow sucking air (ie ventilating) into the pocket that would otherwise have been filled with water vapour from cavitation, to reduce drag. Mr Chevalier described the foil as ""double parabolic cambered with air intake on the trailing edge".  So a supercavitating section that has air in the cavitation zone!

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4 minutes ago, nav said:

Do you watch any videos of the boats out practising?

Like this....

Notice anything happening at the 'foil arm fence'? Looks like a fire hose got turned on right, that's what they are trying to keep from getting any higher up the arm.

Right, hadn't taken note of that, 'foil arm fence' thoughts cancelled!  Cheers!

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Why do the run the foil such that the tip breaks the surface? Why not a tad more down cant?

Is it their version of windward heel on a Moth?

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1 hour ago, MaxHugen said:

Thanks for that!  I found Mr Speer's analysis very interesting... especially "Sailrocket uses a base ventilated section for its main foil."  If I understand what he is saying, the foil was somehow sucking air (ie ventilating) into the pocket that would otherwise have been filled with water vapour from cavitation, to reduce drag. Mr Chevalier described the foil as ""double parabolic cambered with air intake on the trailing edge".  So a supercavitating section that has air in the cavitation zone!

No cavitation forms on the side surface of the foil,

 

the ventilated foil still has attached flow on each side but with a pocket of air sitting along the square/blunt trailing edge.

there is something In The foil profile that trips the water flow into releasing and forming the pocket and shedding the drag of what is an inefficient foil up to the release point, I think in SR2 case this was around 30kts. 
 

the reduction in drag and subsequent acceleration must have been epic 

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50 minutes ago, Liquid said:

Why do the run the foil such that the tip breaks the surface? Why not a tad more down cant?

Is it their version of windward heel on a Moth?

One of the theories bouncing around is that it reduces drag. 

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4 minutes ago, Ex-yachtie said:

One of the theories bouncing around is that it reduces drag. 

And lift.. 

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Compared to the spam argument of yesterday, this information posted by a number of anarchists about super cavitation   is fascinating. 

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8 hours ago, Lakrass said:

Not new tech but difficult to argue a lot of attention and development has been put in the area lately (in parallel with much better tools and computation power for CFD). Not sure they would have the same foils or even concept for the hydroptere now. As for powerboat, they care less about minimizing drag to the extreme.

Looking at ETNZ foiling mode, really close to the surface at time, one wonders if the next move is not towards "skipping" foils on the surface like sailrocket instead. It might be the best bet to overcome cavitation and increase speed even further for next cycle. Might be tricky to get foiling and would work best on flat seas.

Pretty sure I heard Dan Bernasconi speculating in a vid about the possibility of dual foils in the future. He wasn't quite sure how a transition from one foil to the other would occur during mid-flight, but thought that that could be the answer to cavitation in some way. Either that, or I made the whole thing up. ;-)

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3 hours ago, nav said:

Notice anything happening at the 'foil arm fence'? Looks like a fire hose got turned on right, that's what they are trying to keep from getting any higher up the arm.

Well spotted....yes something very wacky is happening at the joint between swing arm and upper foil section.  The water is flying out at right angles to the arm. 

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1 hour ago, JALhazmat said:

..........
the reduction in drag and subsequent acceleration must have been epic 

It was.

5:38 

but this is the AC, not a one tack, one AWA, one TWS, one place in the world, one boat thing..... so not that relevant, right?

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Just now, nav said:

It was.

5:38 

but this is the AC, not a one tack, one AWA, one TWS, one place in the world, one boat thing..... so not that relevant, right?

Exactly.. 

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11 minutes ago, JALhazmat said:

Exactly.. 

Until yesterday never seen a video of them. Amazing stuff and full credit to them. I wonder if any of their experiments with different foil shapes might be of some help in AC

Maybe not super cavitation, but pushing to a higher speed when cavitation occurs. The speed of when cavitation occurs is not set at 50 knots. ?? It can be higher or lower depending on shape ?

 

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1 hour ago, JALhazmat said:

And lift.. 

I think this is an attempt at a hybrid approach to the foil giving good lift when starting out, but shedding drag and unnecessary lift when at high speed. 

Basically, keep the entire foil submerged at lower speeds, so both sides of the wing on either side provide max lift (albeit with drag).

Once up to a certain higher speed, only one side of the wing is needed to provide enough lift, so cant the arm up further, let the outboard side of the wing break the surface and ventilate down to the foil arm joint section. This will drop drag significantly, and reduce lift, but again, the inboard side has enough lift, and with the drag reduction, speed will increase further, affording even more lift to the inboard wing.

If the rules allowed for assymetrical wings on a foil, you could maybe see the inboard wing having a different shape that might be higher drag at slower speeds but that addressed cavitation, whereas the outboard wing would have profile more suited to slower speed take-off. Get going with both, and once up to a good speed, ventilate the outboard wing, and carry on with the inboard over 50 knots. But given the wind range, and limits on foil choices, this idea is probably not feasible inside the AC36 constraints.

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20 minutes ago, mako23 said:

Until yesterday never seen a video of them. Amazing stuff and full credit to them. I wonder if any of their experiments with different foil shapes might be of some help in AC

Maybe not super cavitation, but pushing to a higher speed when cavitation occurs. The speed of when cavitation occurs is not set at 50 knots. ?? It can be higher or lower depending on shape ?

 

Cavitation speed is not a set metric, equally the requirements of the cup race format and what it promotes, early take off, staying on the foil, high angles and use ability don’t cross over much with a concept that needed a highly bespoke design that even when spat out of a computer and carefully built had 25cm of it hacked off the end in desperation to actually achieve the record. 
 

the reason there aren't photos and build diagrams is that it was in constant development and as soon as the record was done it was packed up a d never sailed again. 

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20 minutes ago, rh3000 said:

I think this is an attempt at a hybrid approach to the foil giving good lift when starting out, but shedding drag and unnecessary lift when at high speed. 

Basically, keep the entire foil submerged at lower speeds, so both sides of the wing on either side provide max lift (albeit with drag).

Once up to a certain higher speed, only one side of the wing is needed to provide enough lift, so cant the arm up further, let the outboard side of the wing break the surface and ventilate down to the foil arm joint section. This will drop drag significantly, and reduce lift, but again, the inboard side has enough lift, and with the drag reduction, speed will increase further, affording even more lift to the inboard wing.

If the rules allowed for assymetrical wings on a foil, you could maybe see the inboard wing having a different shape that might be higher drag at slower speeds but that addressed cavitation, whereas the outboard wing would have profile more suited to slower speed take-off. Get going with both, and once up to a good speed, ventilate the outboard wing, and carry on with the inboard over 50 knots. But given the wind range, and limits on foil choices, this idea is probably no feasible inside the AC constraints.

Agree 100%,

if the teams have found benefit of ventilating at least half of one side and still getting the lift the need to maintain flight then bloody hell fair play. 
it could well be wind and angle specific modes too.

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Cutting things too fine?
Trainee team?
Error?
taken some more training wheels off?

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36 minutes ago, chesirecat said:

Just capsized off Beachlands. Righted quickly and main dropped, being towed back

I hope all the lads on the boat are ok. 

WetHog  :ph34r:

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7 hours ago, Ex-yachtie said:

One of the theories bouncing around is that it reduces drag. 

Is the drag penalty for piercing the surface worth the cost of the loss of leeway by raking the foils? Theres also maximum righting moment at that point also I'd imagine.

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46 minutes ago, Varan said:

Over she goes. Whoops, it happens.

Sounds like GD might want to revise, "These things don't go end-over-end like the AC50's", or words to that effect. ;-)

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51 minutes ago, Varan said:

Over she goes. Whoops, it happens.

From RG’s article, I hope everyone is okay.

“The AC75 suffered damage to a steering pedestal in the incident.”

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3 minutes ago, Sailbydate said:

Sounds like GD might want to revise, "These things don't go end-over-end like the AC50's", or words to that effect. ;-)

Gladwell has never let fact get in the way of a good story (or a shit one)...

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1 hour ago, NZL3481 said:

Is the drag penalty for piercing the surface worth the cost of the loss of leeway by raking the foils? Theres also maximum righting moment at that point also I'd imagine.

All good questions. 

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No pictures - it is almost unbelievable!  If the pedestal is broken then I do hope no one was hurt.

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9 hours ago, Liquid said:

Why do the run the foil such that the tip breaks the surface? Why not a tad more down cant?

Is it their version of windward heel on a Moth?

I'm guessing they are trying to maximise lateral lift to windward. The tips are not permanently breaking the surface so that is probably incidental. Lift should not be an issue as they likely have an excess of lift force shortly after achieving foiling speed.

TNZ gained an advantage in AC35 over US several times by sailing higher and making better VMG.

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26 minutes ago, Kiwing said:

No pictures - it is almost unbelievable!  If the pedestal is broken then I do hope no one was hurt.

Makes you wonder, because it was broken by the force of a sailor hitting it....

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30 minutes ago, Kiwing said:

No pictures - it is almost unbelievable!  

Not really , been a pretty gnarly day out off Beachlands a bit like the Amway flop not too many witnesses.

Maybe TNZ will release some footage at a later date.

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2 minutes ago, Priscilla said:

Not really , been a pretty gnarly day out off Beachlands a bit like the Amway flop not too many witnesses.

Maybe TNZ will release some footage at a later date.

Far from tranquil here in Glenfield with NE exposure. The air circulation vents in our double-pane windows were whistling like kettles on the boil.

ENTZ is bound to have footage and they can make PR hay with select shots of their management of a potential disaster.

 

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