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Kiwing

Wings

219 posts in this topic

Wings are supposedly the same - well mostly the same.

 

ETNZ stands out as different. Sections seeming to be able to be controlled almost independently.

 

Does this make any difference to boat performance?

 

Is the wing able to provide stability and power at the same time?

 

What other differences are there between wing controls and wings?

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Given wing control and development is a massive part of the boats performance , yes is the answer to all your questions. The differences will be in the control systems however these are all trying to achieve the same thing, Ultimate control over all aspects of the wing shape and trim for a given range of wind conditions. We really don't know the differences in the control systems as this part is kept secret by all the teams.

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^

Although we do seem to have seen some crazy shit happening on the ETNZ wing.

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Unfortunately most of the time the wing is side on.

 

But when they are coming towards or going away that is when the differences can be seen.

 

Especially when powering up after a t/g or preparing for a t/g.

 

There is some good video of ETNZ where I first noticed this - must find it.

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Unfortunately most of the time the wing is side on.

 

But when they are coming towards or going away that is when the differences can be seen.

 

Especially when powering up after a t/g or preparing for a t/g.

 

There is some good video of ETNZ where I first noticed this - must find it.

At about 2:30 for about the next minute, if you watch the very top of the wing there is a lot of adjustment going on there!

There is another part in one of those videos where they are sailing away and you can see it even clearer, will try and find it.

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Hey Boybland,

 

Thank you for that, amazing eh !

 

I have not studied the other so well but I hope to get some compares.

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I can see two things TNZ is doing differently.

https://www.youtube.com/watch?v=AGJeBP4Cvc0

They tape the gaps off on the aft element of the wing (0:47)

 

and the vertical structure in the aft element of the wing is closer to the mast compared to other teams' wings. (1:00)

 

but what effects that has on performance I don't know.

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@Blak

 

Watch any video of teams coming toward or away from you and you will notice ETNZ's top third of it's wing has a mind of it's own. Flapping around being controlled by hydro. It bares no resemblance to soft sails or other wings. I am trying to guess what it does and why and if it makes much difference.

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I can see the top element change when sailors cross the rig, providing balance trim. GA balances that entire boat with the top element, probly where the lever arm is the greatest. Windsurfers rigs just get blown around on the top, maybe spill a bit in the gusts, but are passive control.

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As a senior Wing Nut, this was my first impression of the ETNZ video. I speculate that the Cyclors ability to pump more fluid is being used to give Gashby more active control of the top of the flap.Essentially allowing him to "beast mode" the top of the wing.

The AC teams have had access to millions more megabytes of CFD than the C Class, and have been pursuing some goals that we never did. For example, they are convinced that twisting the flap ( reducing camber aloft) and thus lowering the center of pressure of the wing, is hugely fast. Further, they want to actually over twist the flap so that the top of the wing is inverted and actually generating lift in the opposite direction. This to counter heeling moment, and allow them to drive the bottom of the wing harder, resulting in more driveing force.

 

At least that is the theory as I have understood it, and have tested on the water on more than one occasion. Our wings can control twist in the E1 & E3, so we can test this pretty well. The troubling news is that I have never found it to be faster than reducing the camber to minimum and sheeting out. Reducing the angle of attack, reduces the lift coefficient and with that the induced drag. So the wing is getting more efficient as it continues to provide as much overturning moment as the platform can absorb. Eventually the parasitic drag is enough to prevent the wing from going faster or tip you over.

 

We tried using the twist as our most active sheeting unit when we first sailed the Cogito wing in 1995, and didn't find the results we expected. I have repeated the experiment every time I have had my ears bent by Dirk or Andrew, but never seen the promised performance improvement over just flattening to minimum and sheeting out.

 

Once again, my knowledge is all practical and gained from sailing wings for a long time. I have been frozen out of any involvement in the America's Cup for crimes I don't recall committing......other than helping to invent the fucking boats. But that is a rant for another day.

SHC

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As a senior Wing Nut, this was my first impression of the ETNZ video. I speculate that the Cyclors ability to pump more fluid is being used to give Gashby more active control of the top of the flap.Essentially allowing him to "beast mode" the top of the wing.

The AC teams have had access to millions more megabytes of CFD than the C Class, and have been pursuing some goals that we never did. For example, they are convinced that twisting the flap ( reducing camber aloft) and thus lowering the center of pressure of the wing, is hugely fast. Further, they want to actually over twist the flap so that the top of the wing is inverted and actually generating lift in the opposite direction. This to counter heeling moment, and allow them to drive the bottom of the wing harder, resulting in more driveing force.

 

At least that is the theory as I have understood it, and have tested on the water on more than one occasion. Our wings can control twist in the E1 & E3, so we can test this pretty well. The troubling news is that I have never found it to be faster than reducing the camber to minimum and sheeting out. Reducing the angle of attack, reduces the lift coefficient and with that the induced drag. So the wing is getting more efficient as it continues to provide as much overturning moment as the platform can absorb. Eventually the parasitic drag is enough to prevent the wing from going faster or tip you over.

 

We tried using the twist as our most active sheeting unit when we first sailed the Cogito wing in 1995, and didn't find the results we expected. I have repeated the experiment every time I have had my ears bent by Dirk or Andrew, but never seen the promised performance improvement over just flattening to minimum and sheeting out.

 

Once again, my knowledge is all practical and gained from sailing wings for a long time. I have been frozen out of any involvement in the America's Cup for crimes I don't recall committing......other than helping to invent the fucking boats. But that is a rant for another day.

SHC

I've been always curious as to why no team tried involve you in the AC, since you've been messing around with wings for a long time.

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Interesting Steve, and makes sense. Thanks

 

I did wonder about the fact if you over twist the top to get righting moment, the chord of that section is further from the centreline to the bottom, so the angle of force will quickly produce more drag than the bottom can produce forward force, Since that impact increases as the Sin of angle (which is quite quickly), whereas the righting moment increases linearly, it does seem inefficient for any but very small angles of over twist

 

But I haven't work through all the maths to prove it even to myself

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As a senior Wing Nut, this was my first impression of the ETNZ video. I speculate that the Cyclors ability to pump more fluid is being used to give Gashby more active control of the top of the flap.Essentially allowing him to "beast mode" the top of the wing.

The AC teams have had access to millions more megabytes of CFD than the C Class, and have been pursuing some goals that we never did. For example, they are convinced that twisting the flap ( reducing camber aloft) and thus lowering the center of pressure of the wing, is hugely fast. Further, they want to actually over twist the flap so that the top of the wing is inverted and actually generating lift in the opposite direction. This to counter heeling moment, and allow them to drive the bottom of the wing harder, resulting in more driveing force.

 

At least that is the theory as I have understood it, and have tested on the water on more than one occasion. Our wings can control twist in the E1 & E3, so we can test this pretty well. The troubling news is that I have never found it to be faster than reducing the camber to minimum and sheeting out. Reducing the angle of attack, reduces the lift coefficient and with that the induced drag. So the wing is getting more efficient as it continues to provide as much overturning moment as the platform can absorb. Eventually the parasitic drag is enough to prevent the wing from going faster or tip you over.

 

We tried using the twist as our most active sheeting unit when we first sailed the Cogito wing in 1995, and didn't find the results we expected. I have repeated the experiment every time I have had my ears bent by Dirk or Andrew, but never seen the promised performance improvement over just flattening to minimum and sheeting out.

 

Once again, my knowledge is all practical and gained from sailing wings for a long time. I have been frozen out of any involvement in the America's Cup for crimes I don't recall committing......other than helping to invent the fucking boats. But that is a rant for another day.

SHC

I've been always curious as to why no team tried involve you in the AC, since you've been messing around with wings for a long time.

Been thinking exactly the same thing.

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Interesting Steve, and makes sense. Thanks

 

I did wonder about the fact if you over twist the top to get righting moment, the chord of that section is further from the centreline to the bottom, so the angle of force will quickly produce more drag than the bottom can produce forward force, Since that impact increases as the Sin of angle (which is quite quickly), whereas the righting moment increases linearly, it does seem inefficient for any but very small angles of over twist

 

But I haven't work through all the maths to prove it even to myself

I suspect they aren't doing one to the exclusion of the other. For any given apparent wind there should be some ideal lift distribution and angle of attack. Tom Speer's paper has been influencing this kind of discussion for a while. He lays out a method for approaching the math.

Fig20.gif

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Maybe ETNZ is trying to be too clever ??

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I know the foils can't be automated and must be controlled manually. What about wings?

 

It either seems that Ashby is trimming the wing (very quickly and constantly, even during gybes) in response to gusts, the wing is soft/flexible enough to respond to gusts in the same way that a windsurfer rig might, or the hydraulics are responding to localised sensors in response to wind speed changes.

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I think Gadsby has to touch a "yes" button to initiate the sequence.

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As a senior Wing Nut, this was my first impression of the ETNZ video. ...

SHC

 

Thanks Steve, it's always great to read your posts. I've been also wondering about the effect of twist on effective aspect ratio. I'd think that twisting off the top so much that it actually creates low pressure on the windward side would greatly enhance spanwise flow. Also, given that there's already a tip vortex at the top of the wing, it seems that to generate righting moment, you'd have to twist off the top a lot more than what you'd assume just from the apparent wind angle. For these reasons I never really believed that the wing twist we see is more than just an effort to reduce lift at the top. But what do I know? Most of my knowledge about wings is from SA and the C Class threads! :)

 

I really hope that some day someone will write a book about all the research and development that went into these boats. It would be a fascinating read.

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As a senior Wing Nut, this was my first impression of the ETNZ video. I speculate that the Cyclors ability to pump more fluid is being used to give Gashby more active control of the top of the flap.Essentially allowing him to "beast mode" the top of the wing.

The AC teams have had access to millions more megabytes of CFD than the C Class, and have been pursuing some goals that we never did. For example, they are convinced that twisting the flap ( reducing camber aloft) and thus lowering the center of pressure of the wing, is hugely fast. Further, they want to actually over twist the flap so that the top of the wing is inverted and actually generating lift in the opposite direction. This to counter heeling moment, and allow them to drive the bottom of the wing harder, resulting in more driveing force.

 

At least that is the theory as I have understood it, and have tested on the water on more than one occasion. Our wings can control twist in the E1 & E3, so we can test this pretty well. The troubling news is that I have never found it to be faster than reducing the camber to minimum and sheeting out. Reducing the angle of attack, reduces the lift coefficient and with that the induced drag. So the wing is getting more efficient as it continues to provide as much overturning moment as the platform can absorb. Eventually the parasitic drag is enough to prevent the wing from going faster or tip you over.

 

We tried using the twist as our most active sheeting unit when we first sailed the Cogito wing in 1995, and didn't find the results we expected. I have repeated the experiment every time I have had my ears bent by Dirk or Andrew, but never seen the promised performance improvement over just flattening to minimum and sheeting out.

 

Once again, my knowledge is all practical and gained from sailing wings for a long time. I have been frozen out of any involvement in the America's Cup for crimes I don't recall committing......other than helping to invent the fucking boats. But that is a rant for another day.

SHC

Looking at the rapid movement, I'm wondering if the top of the flap is actually designed with an elastic range that allows it to passively respond to gust dynamics, much like the head of a windsurfing sail. I have a hard time seeing how someone actively controlling the upper flap could anticipate what was happening at the masthead in any kind of time frame where they could do something that would have a positive effect, whereas the idea of having a certain percentage of the upper flap be able to function as a pressure 'relief valve' (within a range that was controllable at all times by the wing trimmer, obviously) could be a huge advantage on a system that must balance maximum power with not cartwheeling into oblivion in a strong gust.

 

Regarding camber, we had the opposite experience when testing sails with ultra deep bottom sections and extremely twisted, flat heads against the optimum shapes predicted by CFD programs - the distorted shapes had similar top speeds but accelerated far more quickly, which meant that they were faster out of marks, faster in chop, and just faster around any race course. But a big part of that is the massive amount of body english a windsurfer can put into the rig.

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Wow how interesting.

 

As an sunday laser sailor trying to get my mind around all this is .....

 

good for the brain though - thank you Steve, and all you others for teasing out the meanings and pointing out new angles.

 

Sailing 3 times as fast as the wing down wind still gets me .... and having slippery foils does not do it but helps.

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It's "fairly obvious" that for a given amount of righting moment, the lower you push the harder you can push and the boat will go faster. So it makes sense to dump power from the top down, which usually is a problem with sails because the inevitably get fuller when you ease the sheet, so you have to devise some combination of tip bend and leech loading to get the head of the sail to do what you want it to. With a rigid wing, you have the opportunity to actually control this twisting and or flattening. One of the speculations was what is ETNZ doing with all the fluid the cyclors are pumping. Assuming they didn't go for bikes because it was inherently cool, they must have perceived an advantage to having the capacity to move more things. The top of the wing seems like their choice, and one which, according to the theory, should be very potent.

 

The AC Rule defined the profile, minimum weight, cross section and Cg height of the wings, but not the structure or control system. The wing minimum weight and center of gravity rules limit what can be done structurally, so all that is left is to do something with the control system, the weight rules make simplification and weight reduction non players, so all you can do to build a better wing is come up with a more complex control system to achieve some benefit. As always, attempting to control costs by eliminating the first order "easy stuff" like weight reduction, has lead to an exploration of a complex and expensive alternative to gain a probably smaller performance improvement.

 

I always thought the big floppy heads on sailboard rigs were like panaches. Good looking but dumb, and would never be tolerated in a class that actually measured sail area. But I later recognized that ther is a drag reduction benefit of keeping the high and low pressure apart as long as possible. The vortices are, after all caused by two steams of air at different velocities bumping into each other.

All my work has been in classes where you had to extract as much juice as you could from a limited square area of sail. So I never experimented with what could be done if the limits were removed.

SHC

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Looking at the rapid movement, I'm wondering if the top of the flap is actually designed with an elastic range that allows it to passively respond to gust dynamics, much like the head of a windsurfing sail. I have a hard time seeing how someone actively controlling the upper flap could anticipate what was happening at the masthead in any kind of time frame where they could do something that would have a positive effect, whereas the idea of having a certain percentage of the upper flap be able to function as a pressure 'relief valve' (within a range that was controllable at all times by the wing trimmer, obviously) could be a huge advantage on a system that must balance maximum power with not cartwheeling into oblivion in a strong gust.

 

Regarding camber, we had the opposite experience when testing sails with ultra deep bottom sections and extremely twisted, flat heads against the optimum shapes predicted by CFD programs - the distorted shapes had similar top speeds but accelerated far more quickly, which meant that they were faster out of marks, faster in chop, and just faster around any race course. But a big part of that is the massive amount of body english a windsurfer can put into the rig.

 

 

That's an interesting point. So basically the equivalent of a flexible mast tip, but with the ability to continuously control the "flexibility" or twist-responsiveness of the rig. That would be more believable than Glenn's fingers dancing on the tablet a few times per second. ETNZ also made a comment earlier that their youth team was collecting data on wind sheer in the race course area. I guess that would be an important input into how much twist should be programmed into the wing controls.

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Steve, Are you suggesting,

 

that they have more area than they need most of the time?

 

And what are the possibilities for using it ?

 

Stability, RM, moving centre of effort, top speed ??

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Really good discussion here.

 

I am interested in what the greater wing control, particularly at the top of the wing, will have on the ability to sail higher upwind, or lower down wind. Could the real benefit of all this, from TNZ wings perspective, is not only higher control and speed but, importantly higher VMG? And then knowing you have that control of the wing do you change the shape of the foils to cater for that?

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^

What a simple question Just let me think for a minute !!

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Steve, Are you suggesting,

 

that they have more area than they need most of the time?

 

And what are the possibilities for using it ?

 

Stability, RM, moving centre of effort, top speed ??

 

I may have this wrong, but I think they will almost always have too much power once they are up to speed.

The amount of wing required to get the boat up to foiling speed in 6 knots of wind is almost certainly going to be too much at top speed in anything much more than that where the apparent wind speed must be approaching 50 knots

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It's "fairly obvious" that for a given amount of righting moment, the lower you push the harder you can push and the boat will go faster. So it makes sense to dump power from the top down, which usually is a problem with sails because the inevitably get fuller when you ease the sheet, so you have to devise some combination of tip bend and leech loading to get the head of the sail to do what you want it to. With a rigid wing, you have the opportunity to actually control this twisting and or flattening. One of the speculations was what is ETNZ doing with all the fluid the cyclors are pumping. Assuming they didn't go for bikes because it was inherently cool, they must have perceived an advantage to having the capacity to move more things. The top of the wing seems like their choice, and one which, according to the theory, should be very potent.

 

The AC Rule defined the profile, minimum weight, cross section and Cg height of the wings, but not the structure or control system. The wing minimum weight and center of gravity rules limit what can be done structurally, so all that is left is to do something with the control system, the weight rules make simplification and weight reduction non players, so all you can do to build a better wing is come up with a more complex control system to achieve some benefit. As always, attempting to control costs by eliminating the first order "easy stuff" like weight reduction, has lead to an exploration of a complex and expensive alternative to gain a probably smaller performance improvement.

 

I always thought the big floppy heads on sailboard rigs were like panaches. Good looking but dumb, and would never be tolerated in a class that actually measured sail area. But I later recognized that ther is a drag reduction benefit of keeping the high and low pressure apart as long as possible. The vortices are, after all caused by two steams of air at different velocities bumping into each other.

All my work has been in classes where you had to extract as much juice as you could from a limited square area of sail. So I never experimented with what could be done if the limits were removed.

SHC

Ya, we're definitely working from opposite ends. With no size limit, windsurf rigs are designed to break thru the planing threshold as early as possible, and then dispose of the excess area as efficiently as possible IE with minimum drag. But another analogy to consider is that foiling has a similar 'downward step' in the drag vs speed curve (planing threshold for windsurfers, foiling threshold for AC boats), and recovering from any incident that knocked you off the foils would require instantaneous power to minimise the cost in a race. This was where ETNZ had a huge advantage over OR at the beginning of AC34 - their designers had anticipated this as shown by their decision to incorporate LE twist, and their wing was trimmed much more like a windsurf sail at the regatta outset - I had the privilege of watching the first races from a boat, and the difference was obvious and extreme.

 

Basically, it breaks down to how 'powered up' the new boats are. If they are producing power beyond the righting moment limitations of the boats, then you could afford to dedicate the upper section to being reactive to gusts, whereas if they need to extract every last bit of HP out of the permitted wing area, then that's what you would do. Looking at the boats (at least in the stronger winds in recent videos) I think it is the former - they have power to spare.

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^

That's roughly how I read it, with the addition of the fact that the objective at that point is to get the centre of force on the wing as low as possible so that the righting moment is lower and therefore you can apply more force before "bad shit starts to happen".

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I always thought the big floppy heads on sailboard rigs were like panaches. Good looking but dumb, and would never be tolerated in a class that actually measured sail area. But I later recognized that ther is a drag reduction benefit of keeping the high and low pressure apart as long as possible. The vortices are, after all caused by two steams of air at different velocities bumping into each other.

IIRC, those sails demanded a lot of small trimming inputs to work well. It has been ages but I remember giving them constant bumps both to get out of the hole and to maintain speed even when fully powered up. I ~assumed~ the effective flying shape wasn't well represented by the static wing shape. Ie. something magic was going on wrt time. A person with good shoulders can deliver quick, relatively powerful pumps to a windsurfer sized sail. No so much at larger scales with traditional manual power. Maybe ETNZ has an ability to pulse significant power and is looking to make gains with an effect that doesn't show up on traditional steady state analysis?

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Windsurfing had the twist loose leech thing figured in the mid 90s

 

The fact that is so widely misunderstood or ignored by other sailing disciplines is hilarious,

 

The logic that the top flap is being twisted far enough round ageist the flow of apoaremt wind is daft,

 

In one way it would increase righting moment as the twist is reducing power but it's not actively pushing against the apparent wind

 

Windsurfing rigs rely on a highly reactive and highly loaded mast that can deflect in the gusts spilling excess power without disturbing the lower driving section.

 

All the chat about oracles improvement in the last cup loading the bottom section and screwing with the slot gap?

 

Well it was bang on the same theory that helped windsurfing rigs evolve just about 20 years late!

 

 

 

The jizz being spouted about foil shapes being so organic and sculpted ( especially in the NZ threads) have a proper look at a £1500 kite hydrofoil, the shaping,extreme taper and twist? It's all there it's just that all of a sudden the yachting world is finally starting to look at sports and design that moves things forward from the staid and restrictive norms.

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Very interesting, thanks for the insight steve.

And what isn't really discussed here is the coupling of wing induced or controlled heel to foil performance. Riding high with well controlled heel could let you adjust effective cant over what is prescribed in the OD.

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^

If you are canted towards the wind you get lift - if you wanted it ?

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I always thought the big floppy heads on sailboard rigs were like panaches. Good looking but dumb, and would never be tolerated in a class that actually measured sail area. But I later recognized that ther is a drag reduction benefit of keeping the high and low pressure apart as long as possible. The vortices are, after all caused by two steams of air at different velocities bumping into each other.

IIRC, those sails demanded a lot of small trimming inputs to work well. It has been ages but I remember giving them constant bumps both to get out of the hole and to maintain speed even when fully powered up. I ~assumed~ the effective flying shape wasn't well represented by the static wing shape. Ie. something magic was going on wrt time. A person with good shoulders can deliver quick, relatively powerful pumps to a windsurfer sized sail. No so much at larger scales with traditional manual power. Maybe ETNZ has an ability to pulse significant power and is looking to make gains with an effect that doesn't show up on traditional steady state analysis?

 

That's absolutely not correct for a lit slalom board. At the speed regimes we're talking about - low 30s to high 40s - a windsurfer holds the rig in a relatively fixed position relative to the board, applying maximum pressure (which translates to maximum power), and the upper leech responds to gusts. Board control is the major limiting factor.

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It's "fairly obvious" that for a given amount of righting moment, the lower you push the harder you can push and the boat will go faster. So it makes sense to dump power from the top down, which usually is a problem with sails because the inevitably get fuller when you ease the sheet, so you have to devise some combination of tip bend and leech loading to get the head of the sail to do what you want it to. With a rigid wing, you have the opportunity to actually control this twisting and or flattening. One of the speculations was what is ETNZ doing with all the fluid the cyclors are pumping. Assuming they didn't go for bikes because it was inherently cool, they must have perceived an advantage to having the capacity to move more things. The top of the wing seems like their choice, and one which, according to the theory, should be very potent.

 

The AC Rule defined the profile, minimum weight, cross section and Cg height of the wings, but not the structure or control system. The wing minimum weight and center of gravity rules limit what can be done structurally, so all that is left is to do something with the control system, the weight rules make simplification and weight reduction non players, so all you can do to build a better wing is come up with a more complex control system to achieve some benefit. As always, attempting to control costs by eliminating the first order "easy stuff" like weight reduction, has lead to an exploration of a complex and expensive alternative to gain a probably smaller performance improvement.

 

I always thought the big floppy heads on sailboard rigs were like panaches. Good looking but dumb, and would never be tolerated in a class that actually measured sail area. But I later recognized that ther is a drag reduction benefit of keeping the high and low pressure apart as long as possible. The vortices are, after all caused by two steams of air at different velocities bumping into each other.

All my work has been in classes where you had to extract as much juice as you could from a limited square area of sail. So I never experimented with what could be done if the limits were removed.

SHC

Ya, we're definitely working from opposite ends. With no size limit, windsurf rigs are designed to break thru the planing threshold as early as possible, and then dispose of the excess area as efficiently as possible IE with minimum drag. But another analogy to consider is that foiling has a similar 'downward step' in the drag vs speed curve (planing threshold for windsurfers, foiling threshold for AC boats), and recovering from any incident that knocked you off the foils would require instantaneous power to minimise the cost in a race. This was where ETNZ had a huge advantage over OR at the beginning of AC34 - their designers had anticipated this as shown by their decision to incorporate LE twist, and their wing was trimmed much more like a windsurf sail at the regatta outset - I had the privilege of watching the first races from a boat, and the difference was obvious and extreme.

 

Basically, it breaks down to how 'powered up' the new boats are. If they are producing power beyond the righting moment limitations of the boats, then you could afford to dedicate the upper section to being reactive to gusts, whereas if they need to extract every last bit of HP out of the permitted wing area, then that's what you would do. Looking at the boats (at least in the stronger winds in recent videos) I think it is the former - they have power to spare.

 

Check out the last 5 minutes of this video describing Oracles comeback. -

It sounds like their main issue was leeward helm. The wing engineers corrected the problem by raking the wing back even though it screwed up there sheeting system. They had a faster boat the whole time. It just wasn't tuned correctly.

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Windsurfing had the twist loose leech thing figured in the mid 90s

 

The fact that is so widely misunderstood or ignored by other sailing disciplines is hilarious,

 

The logic that the top flap is being twisted far enough round ageist the flow of apoaremt wind is daft,

 

In one way it would increase righting moment as the twist is reducing power but it's not actively pushing against the apparent wind

 

Windsurfing rigs rely on a highly reactive and highly loaded mast that can deflect in the gusts spilling excess power without disturbing the lower driving section.

 

All the chat about oracles improvement in the last cup loading the bottom section and screwing with the slot gap?

 

Well it was bang on the same theory that helped windsurfing rigs evolve just about 20 years late!

 

 

 

The jizz being spouted about foil shapes being so organic and sculpted ( especially in the NZ threads) have a proper look at a £1500 kite hydrofoil, the shaping,extreme taper and twist? It's all there it's just that all of a sudden the yachting world is finally starting to look at sports and design that moves things forward from the staid and restrictive norms.

And there's a simple reason for that - in windsurfing, wild ass guesses cost a few hundred bucks each, and can be sold off for a small profit. I used to design over 150 prototypes per year - these were usually built and evaluated on the water via side by side testing within a week of the original design hitting the plotter. We built anything we could think of, and could test in the real world - progress was unavoidable. You could never afford to do that on a boat, much less organise the side by side testing.

 

And now the same thing is happening with the foils - we can make CNC prototypes of any wing we can imagine at relatively small cost, and actually test it. Not CFD, actual wind water plus expert riders. In an afternoon, we can evaluate multiple front wings, front/back combinations, trim angles etc. How many wings have the AC guys made?

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Check out the last 5 minutes of this video describing Oracles comeback. -

It sounds like their main issue was leeward helm. The wing engineers corrected the problem by raking the wing back even though it screwed up there sheeting system. They had a faster boat the whole time. It just wasn't tuned correctly.

 

Yep. OR started with a big power deficit and a slight lee helm. The initial 'retune' of the wing similar to a windsurf sail increased power, but also moved the CE down (good with increased power) and forward (bad - it exacerbated the lee helm issues). Once they resolved the lee helm issue, they never looked back.

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^

I vaguely remember them stalling at the start of the 1st (I think) race. Related?

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^

I vaguely remember them stalling at the start of the 1st (I think) race. Related?

Its ALL related - slow to foil, slow tacks, slow acceleration, sketchy flying jibes. At the outset of AC34, the top speeds were similar, OR might've even had a slight edge in stronger winds due to their more slippery platform. But they sucked at everything else. ETNZ would splash down and recover almost instantly, while it was painful to watch OR recover from any slowdown. That was all changed with wing trim, and I believe a lot of THAT had to do with their young fresh wing trimmer Kyle Langford, who was able to think outside the box - from what I understand, OR's upwind computer models never even considered coming out of tacks low, building speed and then heading up (which is of course exactly what you do to either plane upwind on a windsurf board or foil upwind on an AC cat).

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Wasn't it more that Dirk de Ridder ( trimmer for the World Series and all the training) was disqualified for his role in Leadgazi? It took Langford and Spitall a while to get it together. Certainly 17 looked like how I feel when working in a new sheet hand. Flying the hull at just the not right angle so we are chasing each other instead of being on it. In the first races look at how many times the windward foil splashes in .......

SHC

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It's "fairly obvious" that for a given amount of righting moment, the lower you push the harder you can push and the boat will go faster. So it makes sense to dump power from the top down, which usually is a problem with sails because the inevitably get fuller when you ease the sheet, so you have to devise some combination of tip bend and leech loading to get the head of the sail to do what you want it to. With a rigid wing, you have the opportunity to actually control this twisting and or flattening. One of the speculations was what is ETNZ doing with all the fluid the cyclors are pumping. Assuming they didn't go for bikes because it was inherently cool, they must have perceived an advantage to having the capacity to move more things. The top of the wing seems like their choice, and one which, according to the theory, should be very potent.

 

The AC Rule defined the profile, minimum weight, cross section and Cg height of the wings, but not the structure or control system. The wing minimum weight and center of gravity rules limit what can be done structurally, so all that is left is to do something with the control system, the weight rules make simplification and weight reduction non players, so all you can do to build a better wing is come up with a more complex control system to achieve some benefit. As always, attempting to control costs by eliminating the first order "easy stuff" like weight reduction, has lead to an exploration of a complex and expensive alternative to gain a probably smaller performance improvement.

 

I always thought the big floppy heads on sailboard rigs were like panaches. Good looking but dumb, and would never be tolerated in a class that actually measured sail area. But I later recognized that ther is a drag reduction benefit of keeping the high and low pressure apart as long as possible. The vortices are, after all caused by two steams of air at different velocities bumping into each other.

All my work has been in classes where you had to extract as much juice as you could from a limited square area of sail. So I never experimented with what could be done if the limits were removed.

SHC

Ya, we're definitely working from opposite ends. With no size limit, windsurf rigs are designed to break thru the planing threshold as early as possible, and then dispose of the excess area as efficiently as possible IE with minimum drag. But another analogy to consider is that foiling has a similar 'downward step' in the drag vs speed curve (planing threshold for windsurfers, foiling threshold for AC boats), and recovering from any incident that knocked you off the foils would require instantaneous power to minimise the cost in a race. This was where ETNZ had a huge advantage over OR at the beginning of AC34 - their designers had anticipated this as shown by their decision to incorporate LE twist, and their wing was trimmed much more like a windsurf sail at the regatta outset - I had the privilege of watching the first races from a boat, and the difference was obvious and extreme.

 

Basically, it breaks down to how 'powered up' the new boats are. If they are producing power beyond the righting moment limitations of the boats, then you could afford to dedicate the upper section to being reactive to gusts, whereas if they need to extract every last bit of HP out of the permitted wing area, then that's what you would do. Looking at the boats (at least in the stronger winds in recent videos) I think it is the former - they have power to spare.

 

Check out the last 5 minutes of this video describing Oracles comeback. -

It sounds like their main issue was leeward helm. The wing engineers corrected the problem by raking the wing back even though it screwed up there sheeting system. They had a faster boat the whole time. It just wasn't tuned correctly.

 

oh please don't start with the, "guys I have an idea, we're down 8 races and this bitch of a boat has a mean lee helm. I remember my opti had that and i raked the mast. whatcha think?"

Presto

If you have any kind of a bullshit meter it has to be pinned at that idea.

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No. Changing the rake on a big wing like that was a big deal. The deck sweeping structure all had to be rebuilt, probably new shrouds and forestays fabricated, and jibs re cut to raise the clews. The other thing is that the longitudinal Cg was moved aft, so the foil loading changes, and with it the entire control of the foiling. This isn't like dropping the pins on a 470. Everything is calculated to the third decimal place, so yes, they did change the rake, but it was a design team decision and not a sailor decision made at the end of the dock.

 

 

If I have learned anything in my time playing with hydrofoils, it is that you can go from hero to zero in a split second. You see this in the training videos, a team may be rock solid one day and total crap the next, and this can be there result of something pretty minor. A member of an AC design team told me that painting the foils can render then inoperative if they aren't polished right. So what is most impressive about Oracle and Artemis is how reliably they fly fast in differing conditions given the restrictions on their foil designs and control inputs.

SHC

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Here's my new conspiracy theory. Ashby just focuses on getting the most speed out the bulk of the wing. One of the bikers uses that mysterious joy stick to invert the top of the wing when the boat starts to heel.

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Wasn't it more that Dirk de Ridder ( trimmer for the World Series and all the training) was disqualified for his role in Leadgazi? It took Langford and Spitall a while to get it together. Certainly 17 looked like how I feel when working in a new sheet hand. Flying the hull at just the not right angle so we are chasing each other instead of being on it. In the first races look at how many times the windward foil splashes in .......

SHC

If you go back and watch the videos, OR's wing trim pre-regatta was always way too flat in the lower sections - look how sketchy their foiling jibes were, even just a week before the AC. I'm suggesting the splashdowns (and slow recoveries) were inevitable with that wing trim paradigm regardless of who's hand was on the sheet, and that the introduction of a fresh trimmer who was less 'conditioned' may well have facilitated OR's ability to make the necessary radical (rather than incremental) changes that it took for them to win.

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oh please don't start with the, "guys I have an idea, we're down 8 races and this bitch of a boat has a mean lee helm. I remember my opti had that and i raked the mast. whatcha think?"

Presto

If you have any kind of a bullshit meter it has to be pinned at that idea.

 

They started working on this on DAY ONE of the regatta, and actually went backwards (when they had increased power but further exacerbated the lee helm issue) before they went forwards.

 

 

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No. Changing the rake on a big wing like that was a big deal. The deck sweeping structure all had to be rebuilt, probably new shrouds and forestays fabricated, and jibs re cut to raise the clews. The other thing is that the longitudinal Cg was moved aft, so the foil loading changes, and with it the entire control of the foiling. This isn't like dropping the pins on a 470. Everything is calculated to the third decimal place, so yes, they did change the rake, but it was a design team decision and not a sailor decision made at the end of the dock.

 

 

If I have learned anything in my time playing with hydrofoils, it is that you can go from hero to zero in a split second. You see this in the training videos, a team may be rock solid one day and total crap the next, and this can be there result of something pretty minor. A member of an AC design team told me that painting the foils can render then inoperative if they aren't polished right. So what is most impressive about Oracle and Artemis is how reliably they fly fast in differing conditions given the restrictions on their foil designs and control inputs.

SHC

Steve, are any of the other teams twisting the flap in a similar way to ETNZ from what you have seen?

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this is one cool thread

keep it coming !

 

+1

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@ fdib and sbd

 

Everyone can contribute at any level give a thought of what you think.

 

Watch the wings coming towards or going away then point out the differences and might get some reasons or suggested reasons.

 

Do all teams add a piece to the bottom of the wing to join it to the deck/tramp? How much difference do you see in wing twist and shape?

 

If you study them they are all slightly different during the manoeuvres and some suggest the gap between the fore element and the aft elements are different? Why? Do you think. We all come with different ideas and they are all interesting.

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@ fdib and sbd

 

Everyone can contribute at any level give a thought of what you think.

 

Watch the wings coming towards or going away then point out the differences and might get some reasons or suggested reasons.

 

Do all teams add a piece to the bottom of the wing to join it to the deck/tramp? How much difference do you see in wing twist and shape?

 

If you study them they are all slightly different during the manoeuvres and some suggest the gap between the fore element and the aft elements are different? Why? Do you think. We all come with different ideas and they are all interesting.

I've been building and racing solid wings with an external slotted flaps similar to those used on the current AC 50's since the late 80's. I use them on landsailers and iceboats.

Closing the gap. - I've found that what we call closing the gap at the bottom of the wing makes them go faster. It helps clean up the vortex that occurs at the bottom of the wing. It appears all AC boats have them (Gap Closers) by looking at the video's. Part of the one design wing package I assume.

The slot - the slot or gap when the flap is angled opens up more when the angle becomes greater. The amount of gap can be changed by moving the pivot point for and aft in the trailing edge of the first element. I design mine to have an optimum shape at 20 degree flap angle. That means the lee side of the wing and flap have no abrupt changes (smooth flow). I find with a 12% thick flap multiply its chord length by 13%. That is the distance of the flaps pivot point forward of the main elements trailing edge. Its better to error on the smaller side than the bigger with the pivot point location. I'm not sure if the pivot point location is One Design or open to choice on the AC 50's.

Twist - In the land sailing/iceboating world excessive twist is slow especially to weather. We get instant feedback while landsailing so if your doing something right or wrong you feel it right away. I use whats called positive control on my wing to change the angle of attack. I can sheet it in or out with no slop in the system. I can actually back wind the wing to act like a giant air brake = drag. Occasionally this can happen on accident in the middle of a tack. You really feel the boat slow down if the timing is off going through the eye of the wind. Based on that I'm some what skeptical of what people see as inverting( back winding) through excessive twist the top of the AC wings for more righting moment. That would cause a lot of drag.The AC wings seem overpowered once hooked up at speed so they need the twist to keep the thing under control. Another benefit of some twist is reducing the tip vortex = less drag off the top. I think there is a fine line between over twist and under twist. Who ever gets it figured out best will prevail.

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A view of twist between Oracle and Artemis at the start of the race.

post-22056-0-10295200-1493441148_thumb.png

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@ fdib and sbd

 

Everyone can contribute at any level give a thought of what you think.

 

Watch the wings coming towards or going away then point out the differences and might get some reasons or suggested reasons.

 

Do all teams add a piece to the bottom of the wing to join it to the deck/tramp? How much difference do you see in wing twist and shape?

 

If you study them they are all slightly different during the manoeuvres and some suggest the gap between the fore element and the aft elements are different? Why? Do you think. We all come with different ideas and they are all interesting.

 

I've been building and racing solid wings with an external slotted flaps similar to those used on the current AC 50's since the late 80's. I use them on landsailers and iceboats.

Closing the gap. - I've found that what we call closing the gap at the bottom of the wing makes them go faster. It helps clean up the vortex that occurs at the bottom of the wing. It appears all AC boats have them (Gap Closers) by looking at the video's. Part of the one design wing package I assume.

The slot - the slot or gap when the flap is angled opens up more when the angle becomes greater. The amount of gap can be changed by moving the pivot point for and aft in the trailing edge of the first element. I design mine to have an optimum shape at 20 degree flap angle. That means the lee side of the wing and flap have no abrupt changes (smooth flow). I find with a 12% thick flap multiply its chord length by 13%. That is the distance of the flaps pivot point forward of the main elements trailing edge. Its better to error on the smaller side than the bigger with the pivot point location. I'm not sure if the pivot point location is One Design or open to choice on the AC 50's.

Twist - In the land sailing/iceboating world excessive twist is slow especially to weather. We get instant feedback while landsailing so if your doing something right or wrong you feel it right away. I use whats called positive control on my wing to change the angle of attack. I can sheet it in or out with no slop in the system. I can actually back wind the wing to act like a giant air brake = drag. Occasionally this can happen on accident in the middle of a tack. You really feel the boat slow down if the timing is off going through the eye of the wind. Based on that I'm some what skeptical of what people see as inverting( back winding) through excessive twist the top of the AC wings for more righting moment. That would cause a lot of drag.The AC wings seem overpowered once hooked up at speed so they need the twist to keep the thing under control. Another benefit of some twist is reducing the tip vortex = less drag off the top. I think there is a fine line between over twist and under twist. Who ever gets it figured out best will prevail.

brilliant summarizing.

 

Thats where the regatta will be won!... by the engine not the tyres!

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@us772

That is great information and that picture gives a real difference,

Which do you think is faster?

I'm guessing AR as it is flatter so faster? Maybe OR is still accelerating?

Do you have any pictures of land/ice yachts to give us people who don't see them that often an idea of what you are talking about?

But thank you for this stimulating information.

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With respect to the pic in post #54 and comments in #56 - The only caveat that I would say is look at the 2 wakes of the boats

Oracle has just done a luff up from deep running and then a speed build whereas Artemis has just hardened up slightly.

 

772's comments are most useful. Can you give some thoughts on the amount of turbulence, wind sheer and mixing you contend with inland, compared to that seen on the ocean, and the twist profile that it dictates?

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All the AC50 wings seal to the central fore and aft spine. Some of the jibs do as well, although not all of them.

The jibs kind of freak me out. I don't know what they are doing there except holding telltales.

The Rules require the trampolines to be nets, which reduces some of the benefit of endplating the wing, but that is equal for everyone.

The vertical movement of th Cp is different with a sealed wing and an unsealed wing. It is bigger with a sealed wing.

 

None on these guys are dumb. They have university degrees and looking into this is their full time job. This is many times more study and work than I have done, using tools and techniques that didn't exist when I started, I don't know how to use now, and couldn't afford. So I am uncomfortable with any glib dismissal of what they are doing and why. I have enough knowledge to understand the principles, but not to evaluate the subtle trade offs. To do that, you have to do the studies.

 

Having said that, it seemed to me that Glen was twitching the top flap more than others. This could be for several reasons. He could be using the twist as his primary sheet instead of the main sheet to power on and off. This makes sense since he would be dumping power where it has the greatest impact on overturning. It also wouldn't interfere with the interaction of the jib and wing down low. There are studies that show that some recurve in the tip of wings reduces tip vortices which results in less drag, which is also overturning force, so a second bird bites the dust. Finally, the small foiling catamarans use the gen elder sheet to help control pitch, pumping in to trim down, and out to trim up. Glen may have been trying the same thing with the wing tip, essentially raising and lowering the Cp to reduce the pitching and thereby heave stability. It has been stated by almost everyone that the faster foil configurations are less stable than the safe ones. So a wing trim technique which gives a further intput to the fil control may be the ticket to faster foils.

 

Furthermore, there is speculation of what ETNZ is doing with the extra hydro they develop. Other teams seem to manage by intermittent grinding on the hand bikes while ETNZ seems to be cycling non stop. They either have higher speed actuators which demand more fluid, or the have added functions which demand more fluid, or maybe both. This is one aspect of the current America's Cup which is new. In the past, the metabolic output of the crew was never given much consideration. The number of hands was important, but the actual wattage that the crew could produce was a minor consideration. My bet is that Olin Stephens or Ben Lexington never gave it a thought beyond "We'll need some big boys on the handles."

 

SHC

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@us772

That is great information and that picture gives a real difference,

Which do you think is faster?

I'm guessing AR as it is flatter so faster? Maybe OR is still accelerating?

Do you have any pictures of land/ice yachts to give us people who don't see them that often an idea of what you are talking about?

But thank you for this stimulating information.

Sorry for the temporary hijacking of the tread. Here is some history on how the use of wings got started (at least in iceboating and maybe sailing in general). The first mention of a rigid wing dates back to 1927. German or Estonian ? iceboat design. That same year Estonia and Germany organized the first official European iceboat racing. USSR had a lot of them racing and formed their own separate 12m and 8 m classes after WWII. Pictured 1- 10m rigid wing. 2 - What appears to be the first rigid wing with a flap 1950.

post-22056-0-69443600-1493476684_thumb.png

post-22056-0-87207100-1493476709_thumb.jpg

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USSR rigid wing fleet

post-22056-0-42915800-1493477353_thumb.png

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With respect to the pic in post #54 and comments in #56 - The only caveat that I would say is look at the 2 wakes of the boats

Oracle has just done a luff up from deep running and then a speed build whereas Artemis has just hardened up slightly.

 

772's comments are most useful. Can you give some thoughts on the amount of turbulence, wind sheer and mixing you contend with inland, compared to that seen on the ocean, and the twist profile that it dictates?

The photo was captured at the start of the practice race when Oracle retired early from this video -

 

The apparent wind is a more because our speeds are a little higher than the AC boats. That makes the difference of wind sheer less important because it is less of a percent from top to bottom. Our wings are not that tall either compared to them so wind sheer is not as big of a factor. I figure through the use of vectors 4 degrees of twist is about all you want in my world. I have the ability to take off the tip section for high winds. It lowers the ce and area. It's faster because the RM improves meaning you can sheet in the wing where its has full drive.

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@ fdib and sbd

 

Everyone can contribute at any level give a thought of what you think.

 

Watch the wings coming towards or going away then point out the differences and might get some reasons or suggested reasons.

 

Do all teams add a piece to the bottom of the wing to join it to the deck/tramp? How much difference do you see in wing twist and shape?

 

If you study them they are all slightly different during the manoeuvres and some suggest the gap between the fore element and the aft elements are different? Why? Do you think. We all come with different ideas and they are all interesting.

I've been building and racing solid wings with an external slotted flaps similar to those used on the current AC 50's since the late 80's. I use them on landsailers and iceboats.

Closing the gap. - I've found that what we call closing the gap at the bottom of the wing makes them go faster. It helps clean up the vortex that occurs at the bottom of the wing. It appears all AC boats have them (Gap Closers) by looking at the video's. Part of the one design wing package I assume.

The slot - the slot or gap when the flap is angled opens up more when the angle becomes greater. The amount of gap can be changed by moving the pivot point for and aft in the trailing edge of the first element. I design mine to have an optimum shape at 20 degree flap angle. That means the lee side of the wing and flap have no abrupt changes (smooth flow). I find with a 12% thick flap multiply its chord length by 13%. That is the distance of the flaps pivot point forward of the main elements trailing edge. Its better to error on the smaller side than the bigger with the pivot point location. I'm not sure if the pivot point location is One Design or open to choice on the AC 50's.

Twist - In the land sailing/iceboating world excessive twist is slow especially to weather. We get instant feedback while landsailing so if your doing something right or wrong you feel it right away. I use whats called positive control on my wing to change the angle of attack. I can sheet it in or out with no slop in the system. I can actually back wind the wing to act like a giant air brake = drag. Occasionally this can happen on accident in the middle of a tack. You really feel the boat slow down if the timing is off going through the eye of the wind. Based on that I'm some what skeptical of what people see as inverting( back winding) through excessive twist the top of the AC wings for more righting moment. That would cause a lot of drag.The AC wings seem overpowered once hooked up at speed so they need the twist to keep the thing under control. Another benefit of some twist is reducing the tip vortex = less drag off the top. I think there is a fine line between over twist and under twist. Who ever gets it figured out best will prevail.

brilliant summarizing.

 

Thats where the regatta will be won!... by the engine not the tyres!

 

Thats where the regatta will be won!... by the engine not the tyres!

I should of said the wing trim is only one piece of the whole package that will win. Artemis's foiling ability looks pretty impressive so far!

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As a senior Wing Nut, this was my first impression of the ETNZ video. I speculate that the Cyclors ability to pump more fluid is being used to give Gashby more active control of the top of the flap.Essentially allowing him to "beast mode" the top of the wing.

The AC teams have had access to millions more megabytes of CFD than the C Class, and have been pursuing some goals that we never did. For example, they are convinced that twisting the flap ( reducing camber aloft) and thus lowering the center of pressure of the wing, is hugely fast. Further, they want to actually over twist the flap so that the top of the wing is inverted and actually generating lift in the opposite direction. This to counter heeling moment, and allow them to drive the bottom of the wing harder, resulting in more driveing force.

 

At least that is the theory as I have understood it, and have tested on the water on more than one occasion. Our wings can control twist in the E1 & E3, so we can test this pretty well. The troubling news is that I have never found it to be faster than reducing the camber to minimum and sheeting out. Reducing the angle of attack, reduces the lift coefficient and with that the induced drag. So the wing is getting more efficient as it continues to provide as much overturning moment as the platform can absorb. Eventually the parasitic drag is enough to prevent the wing from going faster or tip you over.

 

We tried using the twist as our most active sheeting unit when we first sailed the Cogito wing in 1995, and didn't find the results we expected. I have repeated the experiment every time I have had my ears bent by Dirk or Andrew, but never seen the promised performance improvement over just flattening to minimum and sheeting out.

 

Once again, my knowledge is all practical and gained from sailing wings for a long time. I have been frozen out of any involvement in the America's Cup for crimes I don't recall committing......other than helping to invent the fucking boats. But that is a rant for another day.

SHC

 

 

 

Prevailing opinion I have heard more than once, at least as it applies to OracleAUSNZL, is that your crime is simply being American.

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The Russian wing sail stern steerers are the troubling juxtaposition of the best and worst things. In fact it is probably a good analogy for the Soviet Union. A good idea ( socialism and the promise of social justice in a planned efficient economy) mounted on an antique and flawed chassis ( feudalism,corruption, totalitarianism, and a complete lack of modern infrastructure). Put the gas to it and it will spin out and potentially kill people.....

Just an aside.

SHC

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No. Changing the rake on a big wing like that was a big deal. The deck sweeping structure all had to be rebuilt, probably new shrouds and forestays fabricated, and jibs re cut to raise the clews. The other thing is that the longitudinal Cg was moved aft, so the foil loading changes, and with it the entire control of the foiling. This isn't like dropping the pins on a 470. Everything is calculated to the third decimal place, so yes, they did change the rake, but it was a design team decision and not a sailor decision made at the end of the dock....

Just for the record, the rake wasn't changed for the races. Raking aft was tried on the lay day, but it didn't relieve the lee helm. The head wasn't pushing to leeward because of the flap twist, so moving it back did not improve the helm. The original rake was restored for the races.

 

Instead, the lee helm was alleviated by adjusting the strings controlling the tab so as to open the slot. This had the effect of increasing the load on the flap while decreasing the load on the main element, and the resulting aerodynamic moment countered the lee helm. The effect on profile drag was also predicted to be neutral from the tab change, with an increase in drag on the flap and a decrease in drag on the main element. The tab changes were made only low down at first, then additional segments were added in subsequent races, but the change never extended to the entire span.

 

In addition to the tab changes, the flap twist profile was changed to raise the mid leech and twist off more at the head. This increased the load on the part of the wing that was behind the ball and pushing to leeward. It also allowed the wing to produce more lift for the same heeling moment.

 

The December 2013 Seahorse magazine has an article that presents data showing these effects.

 

Moving the ball was actually considered. But it was judged too risky to accomplish in a day and a half.

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Prevailing opinion I have heard more than once, at least as it applies to OracleAUSNZL, is that your crime is simply being American.

 

 

Only in some heads,

 

Most of us are more interested in interesting world (both worlds)

 

This thread has sofar manged to keep on track - thank you everybody.

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From Steve's past on GTF

post-66708-0-22618900-1493496382_thumb.jpg

Main element sealed looks best what is the main element as opposed to wing?

post-66708-0-06927400-1493496451_thumb.jpg

Wing and flap sealed not as good ?

What is the difference between wing and flap - main element?

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^ Just realised,

more blue (low pressure)on Main element

More red (high pressure) on wing and flap

 

So which is best IYO?

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So I get that the tramp must be made of net, but can't they put something directly above or below it to act as an end plate to the wing?

I've read that portion of the class rule and all it says is thou shalt use netting, not thou shall also use nothing else.

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They do use something else, carbon and clysar under the wing (and jib) right about where all that red is...

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So I get that the tramp must be made of net, but can't they put something directly above or below it to act as an end plate to the wing?

I've read that portion of the class rule and all it says is thou shalt use netting, not thou shall also use nothing else.

ETNZ have significant additional endplate, presumably allowable under the rules. No idea why none of the other teams do, perhaps they are all keeping it undeer their hats until later.

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They do use something else, carbon and clysar under the wing (and jib) right about where all that red is...

Yep and I remember it from last time.

But Steve seemed to indicate it wasn't as large as it could be, so what's stopping them ? Weight?

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From SHC's post on GTF

high pressure side

post-66708-0-32232500-1493497524.gif

low pressure side

post-66708-0-31045000-1493497564.gif

 

Of a C class I think?

 

But you can see the leak under and the loss.

 

Thanks Steve

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So I get that the tramp must be made of net, but can't they put something directly above or below it to act as an end plate to the wing?

I've read that portion of the class rule and all it says is thou shalt use netting, not thou shall also use nothing else.

ETNZ have significant additional endplate, presumably allowable under the rules. No idea why none of the other teams do, perhaps they are all keeping it undeer their hats until later.

 

 

 

 

They do use something else, carbon and clysar under the wing (and jib) right about where all that red is...

Yep and I remember it from last time.

But Steve seemed to indicate it wasn't as large as it could be, so what's stopping them ? Weight?

 

What are you guys smoking? Last time? other teams don't have them? Steve talking about tests conducted on another class? Wake up.

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^

Apparently not as good as the (ob)noxious weed you seem to be smoking nav 😂

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Oh dear. Mis labeled the second set of images. Red is low pressure or leeward side. Blue is high pressure windward side.

Tests don on C Class wing and platform, which has some details quite different from AC50. Some of these, like kink in the beams and trampoline material have an effect. Most of the studies show up as spread sheets, not necessarily easy to misunderstand pictures.

SHC

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....main element as opposed to wing?...

The terminology I used vs what Steve uses:

main element = element #1

tab = element #2

flap = element #3

 

I use "wing" to mean the assembly of all the elements.

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@Steve might be my mis labeling - sorry.

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Glen sails a foiling A pretty well. I don't know if it is sealed to the platform or if the platform is only net. It does not have a jib.

 

Would sailing using the top mostly for quick minor adjustment be more like sailing his A? Do you think.

 

Sailing by answering the computer's suggestion will I do this? Yes! Might be a tad futuristic.

 

I imagine the brains trust writing the code that makes the suggestions would be challenging but I guess Glen does the overall planning.

 

The sensors on the wing might be quicker than the eye picking up the tell tales too. Am I on course?

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On the A Class, the current rig is a "decksweeper" and we run a sealed tramp made of sailcloth. It gives a proper end plate effect and has produced big gains in the last 2 years or so. The ideas are not new, but they have been made popular through the development of the A rig.

 

I think that comparing how you can sheet an AC wing and how you sail an A isn't really that relevant. The A relies on a mix of downhaul, mainsheet and mast flex coupled with rotation to control the sail. Like any sailboat, leach control is very important and it interplay with all the other elements. There are enough other AC sailors and designers who have had significant A Class experience that Glenn won't be bringing anything others cannot brong just based on his experiences on the A. What Glenn does have is a brilliant mind as a sailmaker and trimmer which gives him an edge, and that has been gained from many classes including the A and the Tornado. I would rather have Glenn trimming than anybody else i can think of and see him as the biggest single advantage ETNZ has on the water.

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@ A Class Sailor

 

How do you think trimming by screen would be

 

"wind speed increase at point B7" flatten? Yes No

 

almost immediately,

 

"continue 5 degree from true wind" Yes no

 

Just trying to imagine the dialogue

 

"Can I sail it for you" Yes No

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Thank you TRGrin.

It is hard sitting on your chair doing tax etc with the odd glimpse of this exciting world.

Laser sailing is my experience other than 60 years ago. I have been on a 30foot cat in the Tall Ships race in the Bay when doing 18 knots in no apparent wind seemed so strange. Of course laying on the tramp with Dolphins almost touching your out stretched hand and easily keeping up with us, was pretty distracting.

It is a huge jump to here and not knowing where to start as well.

However every now and then you get a clear glimpse of this world with a kind person explaining in lay language some aspect of this amazing boat and race.

Trying to tease some real oil out of sailors who do this is daunting as well and I hearty thank those that have taken the trouble.

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@ A Class Sailor

 

How do you think trimming by screen would be

 

"wind speed increase at point B7" flatten? Yes No

 

almost immediately,

 

"continue 5 degree from true wind" Yes no

 

Just trying to imagine the dialogue

 

"Can I sail it for you" Yes No

 

I suspect more of the later...

 

Maybe with 'mode' choices?

 

But I suspect if you have the processing power and the inputs you would then keep it as simple as possible, GA mentioned the 'hope' that he might also (like BT) get his head out of the boat from time to time - not that there's much evidence of that from the photos etc seen though. More like a teen with his phone!

 

So just a 'refresh all' button ;)

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If there's just a posted photo of shattered carbon fibre on PBs Facebook, you know he clicked yes on the wrong device at a somewhat critical moment... 8)

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^ Made me look :o

 

needs a...

 

Undo.png

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@ A Class Sailor

 

How do you think trimming by screen would be

 

"wind speed increase at point B7" flatten? Yes No

 

almost immediately,

 

"continue 5 degree from true wind" Yes no

 

Just trying to imagine the dialogue

 

"Can I sail it for you" Yes No

 

I suspect more of the later...

 

Maybe with 'mode' choices?

 

But I suspect if you have the processing power and the inputs you would then keep it as simple as possible, GA mentioned the 'hope' that he might also (like BT) get his head out of the boat from time to time - not that there's much evidence of that from the photos etc seen though. More like a teen with his phone!

 

So just a 'refresh all' button ;)

 

 

I don't know. The human brain is pretty amazing, and with the experience of someone like Glenn, it would be really hard to design a system and software that can react better. The hope that he could get his head out of the boat may actually refer to improvements that make it possible to trim by the seat of pants instead of looking at the damn screen all the time. I see value in pre-programming a tack or a jibe, when people have to switch sides and lots of stuff happen at the same time, but in straight line, Glenn may do better than the computer, because he can anticipate events by looking at puffs on the water, communicating with Pete and the rest.

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Maybe the top element is the "seat of his pants element" ???

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^ It's hard to imagine that anyone could anticipate gust dynamics well enough to effectively manipulate the top of the wing, whereas a reactive 'pressure release' system at the extreme top trailing edge of the flap makes total sense to me. But then again, I'm coming from windsurfing, and have zero experience with 100% solid wings.

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^ I guess there would be an computer over ride (for safety?)

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^ No override - computers don't get to 'control' anything, and they never did.

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^ It's hard to imagine that anyone could anticipate gust dynamics well enough to effectively manipulate the top of the wing, whereas a reactive 'pressure release' system at the extreme top trailing edge of the flap makes total sense to me. But then again, I'm coming from windsurfing, and have zero experience with 100% solid wings.

I also sailed windsurfers and always thought of some similar system. I think Steve Clark did something like it in Cogito, a mast inside another so that the top could rotate: or must I change the weed?

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There are some issues with wing masts that need to be understood. The biggest challenge compared with soft sails is that you cannot see when flow is attached or beginning to become detached. With a soft sail, you can see it either with tell tales or because the sail begins to lift. With a wing, you cannot see the leeward side and you don't get the luff of the sail lifting.

 

It's hard to imagine that anyone could anticipate gust dynamics well enough to effectively manipulate the top of the wing

 

I don't think it is hard to imagine. What is the difference between spilling wind by easing the mainsheet or opening the top element? What they seem to be doing is using the top element as the power control, rather than the mainsheet. It is just like adding twist to a conventional sail, but the reason why you usually cannot do this on a conventional sail is because vang usually controls more than just leach. It also contributes to mast bend and therefore overall sail shape. Unlike soft sails and conventional rigs, I don't believe you can set a wing up for automatic gust response like you see when the top of the mast flicks off in a gust and the leach opens.

 

Another factor that makes this style of power control possible is that usually, you need more power on the vang than the mainsheet, meaning playing the mainsheet is both easier and quicker. With the hydraulics, I believe it is just as easy to move the top flap as it is to move the mainsheet, maybe even easier.

 

The question remains whether it is better to play the mainsheet or the wing elements and I doubt there is any clear answer to that. What might work for one team might not work for another. It depends on how you actually sail the boat. I can see beoth methods being used and there being little noticeable difference between them. It could even come down to foil design, because the different methods of playing the wing might load the foils differently. I can see that opening the top element would lower the centre of effort compared with easing the mainsheet and this would impact the load on the foils. Add it all together, it's interesting to note the differences but very hard to draw conclusions.

 

I think Steve Clark did something like it in Cogito, a mast inside another so that the top could rotate:

 

You are correct that the Cogito style wing does have a main spar around which the front element can twist, but that is all about achieving leading element twist to tackle wind shear and not to do with gust response. it is the system used by ETNZ in the last cup but isn't allowed this time.

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^ It's hard to imagine that anyone could anticipate gust dynamics well enough to effectively manipulate the top of the wing, whereas a reactive 'pressure release' system at the extreme top trailing edge of the flap makes total sense to me. But then again, I'm coming from windsurfing, and have zero experience with 100% solid wings.

I also sailed windsurfers and always thought of some similar system. I think Steve Clark did something like it in Cogito, a mast inside another so that the top could rotate: or must I change the weed?

 

We actually did that in windsurfing - in the mid 90's, we looked at a bunch of different options to create reactive twist at the upper trailing edge and also reduce tip vortices, and ended up going with a rotating mini spar at the mast head called a 'shear tip' courtesy of the guy who thought of it, David Starbuck. Ultimately, we were able to achieve the same result with just the rectangular head planform, because the leeches were already flexible and relatively unloaded.

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There are some issues with wing masts that need to be understood. The biggest challenge compared with soft sails is that you cannot see when flow is attached or beginning to become detached. With a soft sail, you can see it either with tell tales or because the sail begins to lift. With a wing, you cannot see the leeward side and you don't get the luff of the sail lifting.

 

It's hard to imagine that anyone could anticipate gust dynamics well enough to effectively manipulate the top of the wing

 

I don't think it is hard to imagine. What is the difference between spilling wind by easing the mainsheet or opening the top element? What they seem to be doing is using the top element as the power control, rather than the mainsheet. It is just like adding twist to a conventional sail, but the reason why you usually cannot do this on a conventional sail is because vang usually controls more than just leach. It also contributes to mast bend and therefore overall sail shape. Unlike soft sails and conventional rigs, I don't believe you can set a wing up for automatic gust response like you see when the top of the mast flicks off in a gust and the leach opens.

 

Another factor that makes this style of power control possible is that usually, you need more power on the vang than the mainsheet, meaning playing the mainsheet is both easier and quicker. With the hydraulics, I believe it is just as easy to move the top flap as it is to move the mainsheet, maybe even easier.

 

The question remains whether it is better to play the mainsheet or the wing elements and I doubt there is any clear answer to that. What might work for one team might not work for another. It depends on how you actually sail the boat. I can see beoth methods being used and there being little noticeable difference between them. It could even come down to foil design, because the different methods of playing the wing might load the foils differently. I can see that opening the top element would lower the centre of effort compared with easing the mainsheet and this would impact the load on the foils. Add it all together, it's interesting to note the differences but very hard to draw conclusions.

I just think a passive 'pressure release' system would make more sense rather than trying to create power at the point of maximum pitching moment and also right where all the tip vortices are.

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2 little remarks in this high quality discussion, even if I am a bit late and have little to bring

 

1-Riding my bicycle in Lorient last year, I met the Groupama Team on the deck, preparing their GroupamaC for a training session

One guy of the design team, disclosed that the top wing inversion, was either not that easy to achieve, nor was it that efficient, I don't know, these guys have signed a NDA, but overall it seemed that they did not rely on this rig feature to expect any performance pick-up

 

2-Regarding the power control of the wing by moving elt 3 instead of the whole wing can find an easy explanation in theory

When a wing is correctly tuned/trimmed, the first element AoA is not that much compared to apparent wind, so not effective to decrease the AoA

Reading some of Mark Drela's ( CFD teacher @ MIT) books or posts you might discover that the AoA of 15% aft part of a wing chord is the biggest driver of the whole wing/sail power.

 

So it makes sense that some team may focus on this point.

 

Cheers

 

BW

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Have noticed the ETNZ wing has an anemometer off the tip, on a forward strut. Didn't see the same on some of the other boats in the photos I found on my phone. Might further suggest the difference in trimming strategies between teams if the readings are being used by GA.

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^ Noticed that up there too, but aren't their also less obvious (and less draggy) ways of getting the same data these days though?

 

Wonder if it will stay up for racing?

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^ It's hard to imagine that anyone could anticipate gust dynamics well enough to effectively manipulate the top of the wing, whereas a reactive 'pressure release' system at the extreme top trailing edge of the flap makes total sense to me. But then again, I'm coming from windsurfing, and have zero experience with 100% solid wings.

 

I don't think the two exclude each other. I like the idea of a reactive pressure release system, the equivalent of a flexible mast tip and leech, but human input could change the characteristics of that as if you could change the flexibility of your mast every few seconds. So human input could be used to adjust the system for the power needed, prepare the system for a gust or lull, or for an upcoming maneuver, but turbulence, quick changes in wind strength would be handled by a mechanical buffer system.

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Depending what their control system looks like, it can be pretty easy to adjust the elasticity of the flap.

It can be as simple as selecting the right cable, or modeling the torsion stiffness of the flap to react at the desired load.

Or , if you wanted to be more adjustable, controlling the springiness of some of the turning point or pivot foundations so they yield at the appropriate rate. Imagine gas shocks with variable air pressure. This could be the "P" alluded to in the ETNZ thread.

SHC

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Depending what their control system looks like, it can be pretty easy to adjust the elasticity of the flap.

It can be as simple as selecting the right cable, or modeling the torsion stiffness of the flap to react at the desired load.

Or , if you wanted to be more adjustable, controlling the springiness of some of the turning point or pivot foundations so they yield at the appropriate rate. Imagine gas shocks with variable air pressure. This could be the "P" alluded to in the ETNZ thread.

SHC

I've allways thought something like that. Some kind of torsion bar inside the upper part that could allow twist.

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Depending what their control system looks like, it can be pretty easy to adjust the elasticity of the flap.

It can be as simple as selecting the right cable, or modeling the torsion stiffness of the flap to react at the desired load.

Or , if you wanted to be more adjustable, controlling the springiness of some of the turning point or pivot foundations so they yield at the appropriate rate. Imagine gas shocks with variable air pressure. This could be the "P" alluded to in the ETNZ thread.

SHC

That's pretty much what I was thinking - you could introduce a couple additional components to the upper flap control system to allow it to automatically release pressure in a gust: range of reactive motion (which if set to zero would mean no dynamic behaviour), and pressure, which would set the spring constant for when and how much it would release. I'm thinking you would put some kind of dampening in parallel with whatever elastic system you used to prevent buffeting etc.

 

But over all, a system like this makes much more sense explaining the rapid upper wing movements on ETNZ than some guy at deck level frantically pushing buttons.

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http://www.azom.com/article.aspx?ArticleID=13516

 

EAP technology is interesting and may be within the rules. Imagine controlling the leading and trailing edge of a foil in the AC50 class without breaching the "No moving appendages below waterline rule"?

 

Is something that flexes a moving appendage?

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The benefits of IPMCs in particular are the large electromechanical bending at low voltages [9], and their soft, flexible structures. This allows them to mimic the motion of biological muscles, and be used in aqueous environments [10,11].

 

Holy smoke batman! Ultrasonic swimming foil blades.

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@ Hobie

 

Like the mental bust !!

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