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      Abbreviated rules   07/28/2017

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Tornado-Cat

The winning foils

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The weak dependence of Cd (Dissipation coef) on pressure gradients (assuming fixed transition locations) indicates that the dissipation D(s)= Rho*Ue^3*Cd

 

 

 

I've never heard of "dissipation" in the context of aerodynamics but that looks more like an equation for predicting power than drag.

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A different location - possibly similar purpose, who could know beyond a w.a.g.

 

13446389_10206980844059088_509255037_o1.

IMO, this foil is a communication stunt by OR in order to mislead other teams. Where is the shot coming from by the way, OR ?

Main research is probably on low speed foils with supercavitation possibilities at high speed thanks to the modification of their profile. Don't ask me how though....

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^ Why do you say that? All you know about the foil is that it tracks further outboard (>RM) than others.

 

Everything else being equal - that seems like a gain. And the profile is presumably still as unconstriained as any other configuration.

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Sure, all being equal, it's a gain, however on a video Soft Bank was a bit faster on a straight line.

MF was talking about tips which shape would change under pressure.

The 2 major limitations for a low wind performing foil in windier conditions are:

- the surface (drag increases at the square of the speed)

- cavitation at the high end, around 50 kts.

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With the boat level- if the stb foil is the same one shown earlier out of the water- then the immersed portion of the foil would look like this which seems a bit weird:

post-30-0-81602400-1466962857_thumb.png

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Sure, all being equal, it's a gain, however on a video Soft Bank was a bit faster on a straight line.

MF was talking about tips which shape would change under pressure.

The 2 major limitations for a low wind performing foil in windier conditions are:

- the surface (drag increases at the square of the speed)

- cavitation at the high end, around 50 kts.

 

Potential gain, well done - so why did you claim

 

IMO, this foil is a communication stunt by OR in order to mislead other teams.

 

 

And you must have a strange grasp of analysis if you think one drag race proves or disproves the value of a foil designed to sail in a full course Match Race

 

as for the rest :blink:

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^^^ Clear that you didn't see the link. :)

 

Reaching and upwind are the two modes requiring the more power and still, OR was behind TJ. What does it tell you nav ? what part of the foil should be the most important one ? why do you think that the canting we see doesn't hide a more important part of their studies ? :unsure:

 

What we need to see now, is if it works upwind, and if it does or not affect the modification of the tip while sailing . Do you have the answer ? I don't.

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What is so difficult to understand here?

 

The CB foils are now basically 90 degree L shaped.

 

The foil control systems are now highly refined and micro-adjustable - allowing previously unstable shapes to achieve stable flight.

 

In AC34 - the angle between vertical and horizontal elements was less than 90 degrees to retain an amount of dihedral and therefore automatic stability.

However, more open intersections have inherently less interference drag than more closed angles - so that's a gain.

 

Furthermore, by canting a more "open shaped" foil outboard will increase RM by widening the footprint.

If the open shaped foiled can be canted sufficiently, then the horizontal element will vector its lift in a direction that will both achieve flight and resist leeway, thereby essentially achieving "Veal Heel" by the Catamarans.

(I see deployment of the CB by oracle as being very similar to that as being deployed by the Vampire Catamaran - it just uses an L foil rather than a T and the trunk is housed in the hull rather than outboard of the hull as done by the Vampire.)

 

Veal Heel allows multiple benefits - the vertical element which previously needed to resist leeway forces through asymmetry can be a lower lift/drag element that has to contribute less leeway and become primarily more of a support strut.

By canting the whole boat package to weather allows better rig aerodynamics and response.

The trimmers can focus on maintaining slight weather heel and then losing it to "upright" in a gust, whereas previously before, the boat was sailed upright to then "heeled" at which point the sum of all forces increased leeway significantly with large leaps to leeward.

Also, whenever the rig has any weather heel, it will begin to unload the immersed foil - allowing it to fly with less AOA and also less drag.

 

The gains are NOT as dramatic as say a Moth in true Veal Heel - but they would be worth chasing....... This development would be a classic engineering example of the virtuous circle - just comes at a very high price of cost, complexity and time to iron out the bugs and learn to use in real life heat of battle manoeuvres.

 

Remember that this cycle of the AC is evolutionary and about refinement - rather than the turning of all things on their head again.

 

 

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Jesus Boink!... you too have joined the " cut and paste" brigade of bullshitters on this thread!!

 

And I thought you had half a brain.

 

90% of the bullshit spun in this thread is stolen from article that the " BS bunch" have read somewhere!

 

This thread has as much cred as Donald Trump's hair!...

 

No one on this thread has a clue about foils!.... now that's the first statement of credible fact posted in this thread.

 

The "blue light seamen scanner" would have Field day in this wank fest!

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What is so difficult to understand here?

 

The CB foils are now basically 90 degree L shaped.

 

The foil control systems are now highly refined and micro-adjustable - allowing previously unstable shapes to achieve stable flight.

 

In AC34 - the angle between vertical and horizontal elements was less than 90 degrees to retain an amount of dihedral and therefore automatic stability.

However, more open intersections have inherently less interference drag than more closed angles - so that's a gain.

 

Furthermore, by canting a more "open shaped" foil outboard will increase RM by widening the footprint.

If the open shaped foiled can be canted sufficiently, then the horizontal element will vector its lift in a direction that will both achieve flight and resist leeway, thereby essentially achieving "Veal Heel" by the Catamarans.

(I see deployment of the CB by oracle as being very similar to that as being deployed by the Vampire Catamaran - it just uses an L foil rather than a T and the trunk is housed in the hull rather than outboard of the hull as done by the Vampire.)

 

Veal Heel allows multiple benefits - the vertical element which previously needed to resist leeway forces through asymmetry can be a lower lift/drag element that has to contribute less leeway and become primarily more of a support strut.

By canting the whole boat package to weather allows better rig aerodynamics and response.

The trimmers can focus on maintaining slight weather heel and then losing it to "upright" in a gust, whereas previously before, the boat was sailed upright to then "heeled" at which point the sum of all forces increased leeway significantly with large leaps to leeward.

Also, whenever the rig has any weather heel, it will begin to unload the immersed foil - allowing it to fly with less AOA and also less drag.

 

The gains are NOT as dramatic as say a Moth in true Veal Heel - but they would be worth chasing....... This development would be a classic engineering example of the virtuous circle - just comes at a very high price of cost, complexity and time to iron out the bugs and learn to use in real life heat of battle manoeuvres.

 

Remember that this cycle of the AC is evolutionary and about refinement - rather than the turning of all things on their head again.

 

 

 

Loved reading this answer / theory. Thanks!

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With the boat level- if the stb foil is the same one shown earlier out of the water- then the immersed portion of the foil would look like this which seems a bit weird:

 

post-30-0-81602400-1466962857.png

 

Of course what you have drawn would be illegal under the AC50 class rules.

 

No part of the daggerboard can exceed maximum beam below MWP and the maximum rotation of the daggerboard in the cant axis is 15 degrees. That is basically 7.5 degrees either side of the maximum draft point of the daggerboard.

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With the boat level- if the stb foil is the same one shown earlier out of the water- then the immersed portion of the foil would look like this which seems a bit weird:

 

post-30-0-81602400-1466962857.png

 

Of course what you have drawn would be illegal under the AC50 class rules.

 

No part of the daggerboard can exceed maximum beam below MWP and the maximum rotation of the daggerboard in the cant axis is 15 degrees. That is basically 7.5 degrees either side of the maximum draft point of the daggerboard.

 

 

It wasn't sketched with regard to the rules- it was drawn to be as representative as possible of the cant evident in the first photo of the port foil and the video of the stb foil. Just so there is no confusion: the sketch shows the stb hull/foil coming at you with the foil tip inboard-as usual. You make a good point because it would seem that Oracle is testing max cant under the rules.

The cant angle and the point where the board goes thru the hull could be changed to be rules compliant assuming Oracle is testing a legal configuration. I don't see what this configuration gains except a small increase in the righting arm. The effect it has on flight stability and how they deal with that would be very interesting....

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They put a curve on a board to get it further outboard. Simple or?

 

There is no restriction on the angle at the bottom - they can make that anything they like, as long as the foil stays inside the ACC rule envelope*

 

There is nothing else know about this foil - all the talk about extra tips and flex etc applies to this as it does to each of their other 5 AC45S foils (if those 'ideas' have any relevancy or base in reality at all that is!?)

 

 

* they can actually do almost anything they want with a surrogate - but we can probably safely assume they are trying to copy the ACC parameters - to get some meaningful data.

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With the boat level- if the stb foil is the same one shown earlier out of the water- then the immersed portion of the foil would look like this which seems a bit weird:

 

post-30-0-81602400-1466962857.png

 

Of course what you have drawn would be illegal under the AC50 class rules.

 

No part of the daggerboard can exceed maximum beam below MWP and the maximum rotation of the daggerboard in the cant axis is 15 degrees. That is basically 7.5 degrees either side of the maximum draft point of the daggerboard.

 

In measurement conditions I am sure the foil is within the box.

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Giant Oracle foil-found on Bermuda thread. I'm betting this is the foil that they're using to experimenting with flex?

 

aon6u0.jpg

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They put a curve on a board to get it further outboard. Simple or?

 

There is no restriction on the angle at the bottom - they can make that anything they like, as long as the foil stays inside the ACC rule envelope*

 

There is nothing else know about this foil - all the talk about extra tips and flex etc applies to this as it does to each of their other 5 AC45S foils (if those 'ideas' have any relevancy or base in reality at all that is!?)

 

 

* they can actually do almost anything they want with a surrogate - but we can probably safely assume they are trying to copy the ACC parameters - to get some meaningful data.

 

I've seen the curve but it doesn't fully explain the angle seen in the picture and video. Especially since its legal to cant the foil 15 degrees.

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What is so difficult to understand here?

 

The CB foils are now basically 90 degree L shaped.

 

The foil control systems are now highly refined and micro-adjustable - allowing previously unstable shapes to achieve stable flight.

 

In AC34 - the angle between vertical and horizontal elements was less than 90 degrees to retain an amount of dihedral and therefore automatic stability.

However, more open intersections have inherently less interference drag than more closed angles - so that's a gain.

 

Furthermore, by canting a more "open shaped" foil outboard will increase RM by widening the footprint.

If the open shaped foiled can be canted sufficiently, then the horizontal element will vector its lift in a direction that will both achieve flight and resist leeway, thereby essentially achieving "Veal Heel" by the Catamarans.

(I see deployment of the CB by oracle as being very similar to that as being deployed by the Vampire Catamaran - it just uses an L foil rather than a T and the trunk is housed in the hull rather than outboard of the hull as done by the Vampire.)

 

Veal Heel allows multiple benefits - the vertical element which previously needed to resist leeway forces through asymmetry can be a lower lift/drag element that has to contribute less leeway and become primarily more of a support strut.

By canting the whole boat package to weather allows better rig aerodynamics and response.

The trimmers can focus on maintaining slight weather heel and then losing it to "upright" in a gust, whereas previously before, the boat was sailed upright to then "heeled" at which point the sum of all forces increased leeway significantly with large leaps to leeward.

Also, whenever the rig has any weather heel, it will begin to unload the immersed foil - allowing it to fly with less AOA and also less drag.

 

The gains are NOT as dramatic as say a Moth in true Veal Heel - but they would be worth chasing....... This development would be a classic engineering example of the virtuous circle - just comes at a very high price of cost, complexity and time to iron out the bugs and learn to use in real life heat of battle manoeuvres.

 

Remember that this cycle of the AC is evolutionary and about refinement - rather than the turning of all things on their head again.

 

 

 

"Veal Heel" was tried on Off Yer Rocker with no significant improvement as I understood it. Seriously doubt there would be any significant benefit to an AC boat because leeway is beneficial in developing lift even to a 90 degree "L"foil so as best I can tell there would be no benefit in unloading the vertical portion of the AC foil. It's worth thinking about though.....

--The "T" foil on the Vampire is canted to eliminate the negative effects on a T foil of leeway. On a boat like the Rave the wand controlled T foil had more drag than the "L" foils used on the Hobie Trifoiler because with leeway the T foil had high and low pressure on the lee side of the "T".(High on the lee side of the daggerboard, low on the top of the lifting foil: drag where they met) The 20 degree cant eliminates that.

post-30-0-05461800-1467076604_thumb.jpg

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It's interesting to watch this foil development and think back to the Little America's Cup held in the US where foils were used for the first time. Groupama used a typical UptiP foil based on TNZ's invention(and larger than Hydros) and Hydros used a foil that was still uptip but much closer to a 90 degree "L". The heave stability of Groupama was way better than Hydros but Hydros was faster-when they could control her. The net result was that Groupama won. It says a lot about control systems if 90 degree foils will wind up being used because while they're faster they are definitely harder to control.

 

Click on the Hydros picture(by Doug Schickler) and compare to Yvan Zeddas Groupama picture of Groupamas uptip:

post-30-0-94398600-1467078591_thumb.jpg

post-30-0-79243400-1467078633_thumb.jpg

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somehow, i have the feeling that foils were not used for the first time during the Little AC.

 

The spin in here is great. it's like a vortex of brain dumps where facts are made to suit a theory in stead of the other way around. But i actually do like the thread as you guys are very good in finding information. so keep up the good work on finding pictures and discuss the differences being made.

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It says a lot about control systems if 90 degree foils will wind up being used because while they're faster they are definitely harder to control.

 

Did you miss AC34 altogether then?

 

americas-cup-win_2682133c.jpg

 

LunaRossa_13cb_113293.jpg

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You'd need to define terms.

 

The angle between the 'more vertical' and 'more horizontal' bits of the foil hardly change, so still >90°

 

A reference between the water surface and the 'horizontal' bit is probably what DL is on about with his uptip stuff - but if he's too lazy to define it I sure won't.

That is as much affected by the canting of the bearing and how far a (curved) board is lowered - as it is by the built in angle anyway obviously.

 

Do you disagree that a more refined and accurate foil control system allowed more critical foils to be used to win the last cup? Or are you with Doug and think that's just a vague possibility for this one?

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lol at change of subject ;)

 

'Type A vs Type B', (DL) is wrong - the angles tried and used are on a continuum

 

'Old (tips not submerged) vs New', (atefooterz) is also overly simplistic in my opinion - here for example (very early AC34 - note the steering)

 

m6649_GG12-SFOSEP-11441.jpeg

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^ the 'above pic' was merely to point out that your suggesting all the past foils were of a certain type was incorrect.

 

We have a new rule, better controls, more experience, but still there is a lot of variation apparent..

 

Sure - something will wash out as 'the best' in the end, but sometimes the 'bit' the win is attributed to by some - just happened to be attached to the winning boat&crew!

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It says a lot about control systems if 90 degree foils will wind up being used because while they're faster they are definitely harder to control.

 

Did you miss AC34 altogether then?

 

 

 

 

 

 

I was referring to boinks comment about the foils being 90 degrees. I don't agree that they are-most are not.

I referred to the LAC(the one before last) because it was the first time foils had been used in the C Class and the differences between Groupama and Hydros perfectly illustrated the problems with less up-tip to the foil.

 

Quote JMOD ,on 28 jun 2016:

"somehow, i have the feeling that foils were not used for the first time during the Little AC.

 

The spin in here is great. it's like a vortex of brain dumps where facts are made to suit a theory in stead of the other way around. But i actually do like the thread as you guys are very good in finding information. so keep up the good work on finding pictures and discuss the differences being made."

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Fuck off Doug - anecdotally, this round of AC development has photos of foils show simple L shapes with 90 degree turns.

Your beloved uptips are last years fashion item and with them go your attempts to create a new (shit) way to write our language.

They also show these boards being canted inwardly (losing RM - but becoming a dihedral set up with more docile characteristics) and more recently, canted outwardly (with no doubt increased "edginess" but with corresponding benefits to boot....)

 

Only in the outwardly canted mode, would the characteristics lean towards the characteristics of Veal Heal - but do not put words in my mouth - It is NOT Veal Heel.

It is only described this way as a matter of corralling other readers to understand the move by AC teams towards exploring more refined and more complex methods of flight - and to speculate as to why they may be chasing this route. I deal in shades of grey and subtle nuances.

 

The control systems capacity to repeatedly alter AOA to fractions of a degree are what counts here - and to do it speedily - enabling foil shapes that would have been seen as highly attractive but too unstable in the previous cycle, to be utilised here.

Every solution is a compromise. There is no magic bullet.

 

Do not bring up Off Your Rocker as an example of what I am advocating.

It's development and ultimate failure is heavily documented - but it is also ancient history.....

 

Though not as ancient as the repeated regurgitation by yourself of Hobie Trifoiler's, Osprey and other such irrelevancies.

 

The world has moved on. Deal with it. Your reference library is out-dated and of no practical relevance to what is being developed by the current AC cycle.

 

So very touched by your kind words 'ski. Do you believe I care what you think?

 

No.....

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Fuck off Doug - anecdotally, this round of AC development has photos of foils show simple L shapes with 90 degree turns.

Your beloved uptips are last years fashion item and with them go your attempts to create a new (shit) way to write our language.

 

 

 

 

Riiiight- Bar's curved UptiP foil and Oracles giant UptiP foil......

 

23leirn.jpg

 

2hxxd75.jpg

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You'd need to define terms.

 

The angle between the 'more vertical' and 'more horizontal' bits of the foil hardly change, so still >90°

 

A reference between the water surface and the 'horizontal' bit is probably what DL is on about with his uptip stuff - but if he's too lazy to define it I sure won't.

That is as much affected by the canting of the bearing and how far a (curved) board is lowered - as it is by the built in angle anyway obviously.

 

Do you disagree that a more refined and accurate foil control system allowed more critical foils to be used to win the last cup? Or are you with Doug and think that's just a vague possibility for this one?

 

Cute! How many dozens of times have I defined it??!! You missed every single one?

Even at it's best Oracles control system wasn't ideal in 34, but it is much ,much better now.

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^ the 'above pic' was merely to point out that your suggesting all the past foils were of a certain type was incorrect.

 

We have a new rule, better controls, more experience, but still there is a lot of variation apparent..

 

Sure - something will wash out as 'the best' in the end, but sometimes the 'bit' the win is attributed to by some - just happened to be attached to the winning boat&crew!

OK but how about getting into what is really up = tricking the water to create different reynolds number profiles suitable for whatever mode is required. The biggest irk with foil chat is the 2D clutter in a 3D fluid enviroment. Maybe gliders can be made better than the follow the leader 90 degree of main wing to tail sameness, in 2D speek?

 

 

Just in the general area of hydro and aerodynamic theory, hasn't recent research shown that most current theory is producing 'sub-optimal results' (e.g. everything that flys with a rudder or winglets), because it's primarily based on work by Ludwig Prandtl in 1925 but ignore the 1932 refinements to his theory?

 

Prandtl-D, Prandtl-M, Horten wings etc - might that not throw/have thrown a spanner in the theoretical works?

 

 

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For anyone having trouble following this, I've tried to simplify visualising the difference, including yellow lines...

 

2eey2di.jpg

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^ the 'above pic' was merely to point out that your suggesting all the past foils were of a certain type was incorrect.

 

We have a new rule, better controls, more experience, but still there is a lot of variation apparent..

 

Sure - something will wash out as 'the best' in the end, but sometimes the 'bit' the win is attributed to by some - just happened to be attached to the winning boat&crew!

OK but how about getting into what is really up = tricking the water to create different reynolds number profiles suitable for whatever mode is required. The biggest irk with foil chat is the 2D clutter in a 3D fluid enviroment. Maybe gliders can be made better than the follow the leader 90 degree of main wing to tail sameness, in 2D speek?

 

 

Just in the general area of hydro and aerodynamic theory, hasn't recent research shown that most current theory is producing 'sub-optimal results' (e.g. everything that flys with a rudder or winglets), because it's primarily based on work by Ludwig Prandtl in 1925 but ignore the 1932 refinements to his theory?

 

Prandtl-D, Prandtl-M, Horten wings etc - might that not throw/have thrown a spanner in the theoretical works?

 

 

 

Mmmm - not so sure.

 

I've just read the paper that came out of this project and I think it stated somewhere that the total induced drag for a given span, using either an elliptical loading (Prandtl's original 1920 thesis that assumes a constant AOA across the whole wing span) or a bell-curve loading (his 1933 updated thesis which requires a neutral or negative AOA near the outer wing) are very similar. The point of the NASA exercise was to provide proverse yaw (ie, yaw that helps the aircraft to turn in the desired direction rather than opposes it), and because these cats don't turn like conventional aircraft then proverse yaw is of little, if any, benefit.

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^ the 'above pic' was merely to point out that your suggesting all the past foils were of a certain type was incorrect.

 

We have a new rule, better controls, more experience, but still there is a lot of variation apparent..

 

Sure - something will wash out as 'the best' in the end, but sometimes the 'bit' the win is attributed to by some - just happened to be attached to the winning boat&crew!

OK but how about getting into what is really up = tricking the water to create different reynolds number profiles suitable for whatever mode is required. The biggest irk with foil chat is the 2D clutter in a 3D fluid enviroment. Maybe gliders can be made better than the follow the leader 90 degree of main wing to tail sameness, in 2D speek?

 

 

Just in the general area of hydro and aerodynamic theory, hasn't recent research shown that most current theory is producing 'sub-optimal results' (e.g. everything that flys with a rudder or winglets), because it's primarily based on work by Ludwig Prandtl in 1925 but ignore the 1932 refinements to his theory?

 

Prandtl-D, Prandtl-M, Horten wings etc - might that not throw/have thrown a spanner in the theoretical works?

 

 

 

Mmmm - not so sure.

 

I've just read the paper that came out of this project and I think it stated somewhere that the total induced drag for a given span, using either an elliptical loading (Prandtl's original 1920 thesis that assumes a constant AOA across the whole wing span) or a bell-curve loading (his 1933 updated thesis which requires a neutral or negative AOA near the outer wing) are very similar. The point of the NASA exercise was to provide proverse yaw (ie, yaw that helps the aircraft to turn in the desired direction rather than opposes it), and because these cats don't turn like conventional aircraft then proverse yaw is of little, if any, benefit.

 

 

They are suggesting massive increases in 'efficiency', but obviously a lot of that comes from the loss of drag achieved simply by removing the entire tail structure from a plane, but some is also from the increased thrust from the 'flat winglets' which would apply here.

 

Yes, the adverse/proverse yaw is associated with the impact of a roll on two wings.

 

But..... winglets are often added to elliptically span loaded wings to increase efficiency but using these are not possible under the ACC rule AFAIK. However with a different/better 'bell curve' designed wing you get those same benefits but with a 'flat' wing - so.... why wouldn't you??

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Horten brother's wingplanes had very low lift coefficient wing section ( positive Cmo) and a lot of twist at the wing tip which provides almost no lift in normal flight.

 

When these boats are sailing downwind at more than twice TWS, there is almost no apparent wind gradient, mainly wind twist

That is why GroupamaC wing plan is very elliptical.

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Good point Nav, but to achieve the same lift from a "bell curve" span loaded wing compared to an elliptical loaded span, the wing has to be longer (I think, after reading the paper), and I'm guessing that that requires a bit more engineering that may not make it entirely worthwhile (yes I know - lots of "presuming" going on here on my part).

 

Also, if the foil is in the form of Doug's UptiP (I'll go with his nomenclature until we have a definitive name for it) and the tip pierces the surface to reduce lift, then the portion of the foil that produced the increased efficiency is now no longer being used. If the lift from the foil could be controlled without doing this then perhaps there are advantages.

 

Anyway, a very interesting paper and thanks for posting the video clip.

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^ Yep I am a bit confused if it's necessarily about added length (a la OTUSA's new foil :o ) or added twist - or both

 

But that whole surface piercing thing was already history last AC, let alone this one wasn't it - so factor that out.

 

 

 

(piercing might go well with the other theme running here though :D )

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Good point Nav, but to achieve the same lift from a "bell curve" span loaded wing compared to an elliptical loaded span, the wing has to be longer (I think, after reading the paper), and I'm guessing that that requires a bit more engineering that may not make it entirely worthwhile (yes I know - lots of "presuming" going on here on my part).

 

Also, if the foil is in the form of Doug's UptiP (I'll go with his nomenclature until we have a definitive name for it) and the tip pierces the surface to reduce lift, then the portion of the foil that produced the increased efficiency is now no longer being used. If the lift from the foil could be controlled without doing this then perhaps there are advantages.

 

Anyway, a very interesting paper and thanks for posting the video clip.

 

CD, UptiP is my spelling but "uptip" is name given to the TNZ type foil by the inventors themselves.

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Like many here I’ve been hard-pressed to get too excited by this upcoming AC because the design innovation we have seen in previous cycles would be missing to a large extent. However, I’m beginning to see that the foil designs and associated control systems open up a can of technical worms, with probable application to all sailing if speed and stability are desired.

 

For example, it seems that Team Japan may have fast foils (but who really knows how fast?), but a fast foil usually means less drag, and less drag is easily achieved at the expense of reduced lift, and so the foil area or span has to be increased to allow for the reduced lift, and this then produces more drag, and so it goes on.

 

The great lea-valley bob ski has often posted that most of us write drivel or copy what others have already written. I urge him to read and understand NASA/TP—2016–219072 and then he can put his money where his mouth is and contribute something worthwhile, or at the very least interesting, to the conversation.

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Aeronamics 14 footer using similar foils to the Quant 23:

 

LOA 4.25m/13.9'
Beam-1.8m/5.9'
Beam-leeward foil deployed: 3.2m/10.5'
weight, all up: 55kg/121lb
Takeoff 6kts true wind
target: 8000euro intro price(about $9100)

post-30-0-57501600-1467326994_thumb.png

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Maybe the most sailing fun I've had was whenever planing a (chimed-hull) Fireball in the right conditions - it's both powerful and exciting. That thing above looks kinda boring?

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So instead of raking the foil to change lift, they are raising it up and down thru the curved part of the upper foil to adjust the effective lift angle? Not sure I explained that correctly.

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So instead of raking the foil to change lift, they are raising it up and down thru the curved part of the upper foil to adjust the effective lift angle? Not sure I explained that correctly.

I get the same impression. Maybe it is less power-intensive to do it that way at 50knts? Rake adjustments must be hell through the water at that speed given the size of those damn foils, there could well be better leverage gained by adjusting it vertically instead.

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The Aeronamics foil , like the Quant 23 foil, doesn't need to be adjusted once it is set it's pretty much automatic like any surface piercing foil.

Bar's UptiP foil works like any uptip foil: leeway coupling. But because of the great "UP" angle of the foil tip, in my opinion, it will be a lot more automatic than a 90 degree AC foil and probably will be able to be set for any given condition and likely not require any adjustment. But if conditions change it would have the rake and/or the cant adjusted before it was adjusted vertically....

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BAR foil seems to be the same as the one I posted on post 1

 

Except the foil in the latest picture seems to have a flat in the curve followed by a small "kink" not apparent in the original picture . Maybe just a different perspective or an entirely(or partially) new foil......

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Tom Speer's rather detailed explanation of how an UptiP foil works. Some uptip foils work a bit differently than what he describes because the foil designer wanted the tip to behave like a surface piercing foil.(GC32)

But nonetheless an excellent technical description:

The curved part of the vertical foil produces essentially the same lift as it rises. This is necessary to counter the side force from the sail rig, which does not change as the height changes.

Because the horizontal lift is constant but the vertical area is reduced as the boat rises, the leeway angle increases. It is the coupling of leeway with heave that is exploited by the L foil to provide vertical static stability.

The dihedral angle of the horizontal wing is set so that the angle of attack of the wing is reduced as the leeway angle increases. This satisfies the static stability condition that the vertical lift decrease as the heave increases.

Because the same horizontal lift is produced over a reduced vertical span, the sideways wash in the wake is also greater and the trailing vortices are more intense. This causes a coupling with the horizontal wing that increases the vertical lift, because the horizontal wing acts as a winglet for the vertical part of the foil (and vice versa). The dihedral angle required for vertical stability is greater than what one might expect by looking at the wing alone because it must overcome this wake-coupled influence. The result is there is a range of dihedral angles that provide positive vertical stability and a range of dihedral angles that are destabilizing in heave because of the coupling with the shed vorticity of the vertical part of the foil.

Although there are times when the foil tip has broached the surface, this is not the normal mechanism for providing heave stability in L foils. The best performance is obtained with the hull just above the wavetops and the wing submerged well below the surface. The leeway-modulated heave stability is still effective in this condition, and the induced drag is minimized.

Canting the foil inboard has the effect of increasing the dihedral angle of the wing, which enhances the heave stability. The vertical lift is spread over a greater span because the curved part of the foil is oriented to provide more vertical component of the force. This reduces the induced drag due to the vertical force. However, the induced drag of the horizontal force would be increased, so cant is typically used off the wind when the side force from the rig is less and the side force produced by the foils is correspondingly less. The foils still have to support the weight of the boat, so the vertical force is not lessened, but the relative proportions of vertical and horizontal force are changed, making the canted foil better suited to the operating condition. Cant allows the leeway-modulated heave stability to be increased an an acceptable penalty in the induced drag because of the lower side force and the higher speeds, which also reduce induced drag.

Upwind, the foils are canted to their vertical position to minimize the induced drag from the high side force and reduced speeds. The reduction in horizontal wing dihedral angle with vertical cant impacts the leeway-modulated heave stability, which is why it is much more difficult to achieve stable flight upwind than downwind. The crew had to be more active in trimming the wing and foil to deal with the reduction in natural heave stability, which was very hard on the grinders when flyng upwind.

Whether canted or upright, the mechanism for providing natural heave stability was still the coupling between heave and leeway, which led to a reduction in vertical lift because of the designed-in coupling between leeway and vertical lift by virtue of the wing dihedral. Reduction in horizontal/vertical-lifting area due to the foil tip broaching the surface was not part of this primary source of heave stability. Allowing the tip to broach the surface had big penalties in terms of induced drag and increased leeway due to insufficient vertical span.
__________________
Tom Speer

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So instead of raking the foil to change lift, they are raising it up and down thru the curved part of the upper foil to adjust the effective lift angle? Not sure I explained that correctly.

I get the same impression. Maybe it is less power-intensive to do it that way at 50knts? Rake adjustments must be hell through the water at that speed given the size of those damn foils, there could well be better leverage gained by adjusting it vertically instead.

 

My first reaction to these big uptip foils was that it was perhaps a solution to a lack of energy required to adjust every second the L foils.

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"My first reaction to these big uptip foils was that it was perhaps a solution to a lack of energy required to adjust every second the L foils."

 

What about just having different sized foils for different conditions - and then testing them exhaustively to see how they perform in what are perceived to be their non-optimum conditions?

 

It is plausible that a foil designed for 5-8 knots will suddenly find itself in 12-15knts of TWS and so developing foils that primarily are for one set of conditions but can remain competitive in other conditions would be highly desirable. Having foils that are "all-rounders" maybe as important as those that are so single purposed as to be a liability should they be asked to operate in conditions that are not their forte.

 

Its like being caught with the wrong headsail up with not enough time to change it before the top mark - you learn how to best deal with it......

 

This cycle is in Bermuda with changeable conditions - not SF with its metronomic seabreeze.

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"My first reaction to these big uptip foils was that it was perhaps a solution to a lack of energy required to adjust every second the L foils."

 

What about just having different sized foils for different conditions - and then testing them exhaustively to see how they perform in what are perceived to be their non-optimum conditions?

 

It is plausible that a foil designed for 5-8 knots will suddenly find itself in 12-15knts of TWS and so developing foils that primarily are for one set of conditions but can remain competitive in other conditions would be highly desirable. Having foils that are "all-rounders" maybe as important as those that are so single purposed as to be a liability should they be asked to operate in conditions that are not their forte.

 

Its like being caught with the wrong headsail up with not enough time to change it before the top mark - you learn how to best deal with it......

 

This cycle is in Bermuda with changeable conditions - not SF with its metronomic seabreeze.

I completely agree with this. Even though they can, IMO, change their foil, they need to design all rounded foils for the case wind changes in the same race. The choice of the right foil before the race will be key.

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Tom Speer's rather detailed explanation of how an UptiP foil works. Some uptip foils work a bit differently than what he describes because the foil designer wanted the tip to behave like a surface piercing foil.(GC32)

But nonetheless an excellent technical description:

The curved part of the vertical foil produces essentially the same lift as it rises. This is necessary to counter the side force from the sail rig, which does not change as the height changes.

 

Because the horizontal lift is constant but the vertical area is reduced as the boat rises, the leeway angle increases. It is the coupling of leeway with heave that is exploited by the L foil to provide vertical static stability.

 

The dihedral angle of the horizontal wing is set so that the angle of attack of the wing is reduced as the leeway angle increases. This satisfies the static stability condition that the vertical lift decrease as the heave increases.

 

Because the same horizontal lift is produced over a reduced vertical span, the sideways wash in the wake is also greater and the trailing vortices are more intense. This causes a coupling with the horizontal wing that increases the vertical lift, because the horizontal wing acts as a winglet for the vertical part of the foil (and vice versa). The dihedral angle required for vertical stability is greater than what one might expect by looking at the wing alone because it must overcome this wake-coupled influence. The result is there is a range of dihedral angles that provide positive vertical stability and a range of dihedral angles that are destabilizing in heave because of the coupling with the shed vorticity of the vertical part of the foil.

 

Although there are times when the foil tip has broached the surface, this is not the normal mechanism for providing heave stability in L foils. The best performance is obtained with the hull just above the wavetops and the wing submerged well below the surface. The leeway-modulated heave stability is still effective in this condition, and the induced drag is minimized.

 

Canting the foil inboard has the effect of increasing the dihedral angle of the wing, which enhances the heave stability. The vertical lift is spread over a greater span because the curved part of the foil is oriented to provide more vertical component of the force. This reduces the induced drag due to the vertical force. However, the induced drag of the horizontal force would be increased, so cant is typically used off the wind when the side force from the rig is less and the side force produced by the foils is correspondingly less. The foils still have to support the weight of the boat, so the vertical force is not lessened, but the relative proportions of vertical and horizontal force are changed, making the canted foil better suited to the operating condition. Cant allows the leeway-modulated heave stability to be increased an an acceptable penalty in the induced drag because of the lower side force and the higher speeds, which also reduce induced drag.

 

Upwind, the foils are canted to their vertical position to minimize the induced drag from the high side force and reduced speeds. The reduction in horizontal wing dihedral angle with vertical cant impacts the leeway-modulated heave stability, which is why it is much more difficult to achieve stable flight upwind than downwind. The crew had to be more active in trimming the wing and foil to deal with the reduction in natural heave stability, which was very hard on the grinders when flyng upwind.

 

Whether canted or upright, the mechanism for providing natural heave stability was still the coupling between heave and leeway, which led to a reduction in vertical lift because of the designed-in coupling between leeway and vertical lift by virtue of the wing dihedral. Reduction in horizontal/vertical-lifting area due to the foil tip broaching the surface was not part of this primary source of heave stability. Allowing the tip to broach the surface had big penalties in terms of induced drag and increased leeway due to insufficient vertical span.

__________________

Tom Speer

 

Thanks Doug.

Tom explains how L foils work, why broaching is not necessary for stability and how they use vertical or inward canting.

But if we want to explain the outward canting, we have to either develop a new theory, or accept that a smaller dihedral angle of the tip, or that tips are flexible. Isn't it ?

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"My first reaction to these big uptip foils was that it was perhaps a solution to a lack of energy required to adjust every second the L foils."

 

What about just having different sized foils for different conditions - and then testing them exhaustively to see how they perform in what are perceived to be their non-optimum conditions?

 

It is plausible that a foil designed for 5-8 knots will suddenly find itself in 12-15knts of TWS and so developing foils that primarily are for one set of conditions but can remain competitive in other conditions would be highly desirable. Having foils that are "all-rounders" maybe as important as those that are so single purposed as to be a liability should they be asked to operate in conditions that are not their forte.

 

Its like being caught with the wrong headsail up with not enough time to change it before the top mark - you learn how to best deal with it......

 

This cycle is in Bermuda with changeable conditions - not SF with its metronomic seabreeze.

... think! Tip vortices and vertical movement at speed... aka uptips on planes...

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Tom Speer's rather detailed explanation of how an UptiP foil works. Some uptip foils work a bit differently than what he describes because the foil designer wanted the tip to behave like a surface piercing foil.(GC32)

But nonetheless an excellent technical description:

The curved part of the vertical foil produces essentially the same lift as it rises. This is necessary to counter the side force from the sail rig, which does not change as the height changes.

 

Because the horizontal lift is constant but the vertical area is reduced as the boat rises, the leeway angle increases. It is the coupling of leeway with heave that is exploited by the L foil to provide vertical static stability.

 

The dihedral angle of the horizontal wing is set so that the angle of attack of the wing is reduced as the leeway angle increases. This satisfies the static stability condition that the vertical lift decrease as the heave increases.

 

Because the same horizontal lift is produced over a reduced vertical span, the sideways wash in the wake is also greater and the trailing vortices are more intense. This causes a coupling with the horizontal wing that increases the vertical lift, because the horizontal wing acts as a winglet for the vertical part of the foil (and vice versa). The dihedral angle required for vertical stability is greater than what one might expect by looking at the wing alone because it must overcome this wake-coupled influence. The result is there is a range of dihedral angles that provide positive vertical stability and a range of dihedral angles that are destabilizing in heave because of the coupling with the shed vorticity of the vertical part of the foil.

 

Although there are times when the foil tip has broached the surface, this is not the normal mechanism for providing heave stability in L foils. The best performance is obtained with the hull just above the wavetops and the wing submerged well below the surface. The leeway-modulated heave stability is still effective in this condition, and the induced drag is minimized.

 

Canting the foil inboard has the effect of increasing the dihedral angle of the wing, which enhances the heave stability. The vertical lift is spread over a greater span because the curved part of the foil is oriented to provide more vertical component of the force. This reduces the induced drag due to the vertical force. However, the induced drag of the horizontal force would be increased, so cant is typically used off the wind when the side force from the rig is less and the side force produced by the foils is correspondingly less. The foils still have to support the weight of the boat, so the vertical force is not lessened, but the relative proportions of vertical and horizontal force are changed, making the canted foil better suited to the operating condition. Cant allows the leeway-modulated heave stability to be increased an an acceptable penalty in the induced drag because of the lower side force and the higher speeds, which also reduce induced drag.

 

Upwind, the foils are canted to their vertical position to minimize the induced drag from the high side force and reduced speeds. The reduction in horizontal wing dihedral angle with vertical cant impacts the leeway-modulated heave stability, which is why it is much more difficult to achieve stable flight upwind than downwind. The crew had to be more active in trimming the wing and foil to deal with the reduction in natural heave stability, which was very hard on the grinders when flyng upwind.

 

Whether canted or upright, the mechanism for providing natural heave stability was still the coupling between heave and leeway, which led to a reduction in vertical lift because of the designed-in coupling between leeway and vertical lift by virtue of the wing dihedral. Reduction in horizontal/vertical-lifting area due to the foil tip broaching the surface was not part of this primary source of heave stability. Allowing the tip to broach the surface had big penalties in terms of induced drag and increased leeway due to insufficient vertical span.

__________________

Tom Speer

 

 

Can we once and for all leave the uptip bullshit behind us.

 

Your own expert tells you that what you imagine is happening - is not happening.

V or L or S, at least as far as Tom Speer knows and has investigated (up to the point where he wrote this anyway) are working in the same way and that has nothing to do with reduced lift through surface piercing and reduced effective area. (a la Jacob's Ladder etc) He even states that has negative consequences.

So can you accept that the shapes are on a continuum from more closed to more open angles but that how they 'look' does not mean they are designed to work in fundamentally different* ways? Uptip does not exist!

 

Although there are times when the foil tip has broached the surface, this is not the normal mechanism for providing heave stability in L foils. The best performance is obtained with the hull just above the wavetops and the wing submerged well below the surface. The leeway-modulated heave stability is still effective in this condition, and the induced drag is minimized.

 

* of course this may no longer be true by the end of AC35!?

 

 

lol at change of subject ;)

 

'Type A vs Type B', (DL) is wrong - the angles tried and used are on a continuum

 

'Old (tips not submerged) vs New', (atefooterz) is also overly simplistic in my opinion - here for example (very early AC34 - note the steering)

 

m6649_GG12-SFOSEP-11441.jpeg

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again from the Tom Speer explanation...

 

 

Upwind, the foils are canted to their vertical position to minimize the induced drag from the high side force and reduced speeds.

 

A board that can be taken to the outboard edge of the ACC envelope will be 'more vertical' in a heeled boat - that plus the added RM is surely enough to explain that style (ie OTUSA's 2 outwardly curved boards) at least being trialed.

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"My first reaction to these big uptip foils was that it was perhaps a solution to a lack of energy required to adjust every second the L foils."

 

What about just having different sized foils for different conditions - and then testing them exhaustively to see how they perform in what are perceived to be their non-optimum conditions?

 

It is plausible that a foil designed for 5-8 knots will suddenly find itself in 12-15knts of TWS and so developing foils that primarily are for one set of conditions but can remain competitive in other conditions would be highly desirable. Having foils that are "all-rounders" maybe as important as those that are so single purposed as to be a liability should they be asked to operate in conditions that are not their forte.

 

Its like being caught with the wrong headsail up with not enough time to change it before the top mark - you learn how to best deal with it......

 

This cycle is in Bermuda with changeable conditions - not SF with its metronomic seabreeze.

I completely agree with this. Even though they can, IMO, change their foil, they need to design all rounded foils for the case wind changes in the same race. The choice of the right foil before the race will be key.

 

 

4 ACC boards only may be measured in - that does not allow for a lot of specialisation, none in fact if you have to have them in pairs* - and want a spare set!

 

* there was at least one explanation of OTUSA using foils assymetrically last time to positive effect - so 'pairs' may not be relevant any longer if this holds true for the Bermuda course as well.

 

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Tom Speer's rather detailed explanation of how an UptiP foil works. Some uptip foils work a bit differently than what he describes because the foil designer wanted the tip to behave like a surface piercing foil.(GC32)

But nonetheless an excellent technical description:

The curved part of the vertical foil produces essentially the same lift as it rises. This is necessary to counter the side force from the sail rig, which does not change as the height changes.

 

Because the horizontal lift is constant but the vertical area is reduced as the boat rises, the leeway angle increases. It is the coupling of leeway with heave that is exploited by the L foil to provide vertical static stability.

 

The dihedral angle of the horizontal wing is set so that the angle of attack of the wing is reduced as the leeway angle increases. This satisfies the static stability condition that the vertical lift decrease as the heave increases.

 

Because the same horizontal lift is produced over a reduced vertical span, the sideways wash in the wake is also greater and the trailing vortices are more intense. This causes a coupling with the horizontal wing that increases the vertical lift, because the horizontal wing acts as a winglet for the vertical part of the foil (and vice versa). The dihedral angle required for vertical stability is greater than what one might expect by looking at the wing alone because it must overcome this wake-coupled influence. The result is there is a range of dihedral angles that provide positive vertical stability and a range of dihedral angles that are destabilizing in heave because of the coupling with the shed vorticity of the vertical part of the foil.

 

Although there are times when the foil tip has broached the surface, this is not the normal mechanism for providing heave stability in L foils. The best performance is obtained with the hull just above the wavetops and the wing submerged well below the surface. The leeway-modulated heave stability is still effective in this condition, and the induced drag is minimized.

 

Canting the foil inboard has the effect of increasing the dihedral angle of the wing, which enhances the heave stability. The vertical lift is spread over a greater span because the curved part of the foil is oriented to provide more vertical component of the force. This reduces the induced drag due to the vertical force. However, the induced drag of the horizontal force would be increased, so cant is typically used off the wind when the side force from the rig is less and the side force produced by the foils is correspondingly less. The foils still have to support the weight of the boat, so the vertical force is not lessened, but the relative proportions of vertical and horizontal force are changed, making the canted foil better suited to the operating condition. Cant allows the leeway-modulated heave stability to be increased an an acceptable penalty in the induced drag because of the lower side force and the higher speeds, which also reduce induced drag.

 

Upwind, the foils are canted to their vertical position to minimize the induced drag from the high side force and reduced speeds. The reduction in horizontal wing dihedral angle with vertical cant impacts the leeway-modulated heave stability, which is why it is much more difficult to achieve stable flight upwind than downwind. The crew had to be more active in trimming the wing and foil to deal with the reduction in natural heave stability, which was very hard on the grinders when flyng upwind.

 

Whether canted or upright, the mechanism for providing natural heave stability was still the coupling between heave and leeway, which led to a reduction in vertical lift because of the designed-in coupling between leeway and vertical lift by virtue of the wing dihedral. Reduction in horizontal/vertical-lifting area due to the foil tip broaching the surface was not part of this primary source of heave stability. Allowing the tip to broach the surface had big penalties in terms of induced drag and increased leeway due to insufficient vertical span.

__________________

Tom Speer

 

 

Can we once and for all leave the uptip bullshit behind us.

 

Your own expert tells you that what you imagine is happening - is not happening.

V or L or S, at least as far as Tom Speer knows and has investigated (up to the point where he wrote this anyway) are working in the same way and that has nothing to do with reduced lift through surface piercing and reduced effective area. (a la Jacob's Ladder etc) He even states that has negative consequences.

So can you accept that the shapes are on a continuum from more closed to more open angles but that how they 'look' does not mean they are designed to work in fundamentally different* ways? Uptip does not exist!

 

Although there are times when the foil tip has broached the surface, this is not the normal mechanism for providing heave stability in L foils. The best performance is obtained with the hull just above the wavetops and the wing submerged well below the surface. The leeway-modulated heave stability is still effective in this condition, and the induced drag is minimized.

 

* of course this may no longer be true by the end of AC35!?

 

 

lol at change of subject ;)

 

'Type A vs Type B', (DL) is wrong - the angles tried and used are on a continuum

 

'Old (tips not submerged) vs New', (atefooterz) is also overly simplistic in my opinion - here for example (very early AC34 - note the steering)

 

 

 

 

Despite what Tom says there are other designers of UptiP foils that specifically say they use the up-tip as a surface piercing foil!! The proof is the GC32 that mostly sails with the tip exposed-design by Martin Fischer.

What utter and complete nonsense!!!

 

GC32 on record speed run flying(as usual) with exposed lee foil tip:

 

 

2j68y7p.jpg

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Doug you are quoting AC designers talking about AC foils in the AC forum trying to convince people that your uptip foils have relevance - but proving the exact opposite

 

You need to take your GC32 foils to "Cheap one-designs where no billionaires care about ultimate performance" anarchy

 

 

 

yes yes "cheap one-designs" is sorta the whole point of the current AC - I do see the irony

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No, I'm talking about foils period. Bar has a large uptip, Oracle has the largest yet and you say they have no relevance? Just nonsense.

Most of the foils I've seen have some degree of uptip. When you talk about control power a 90 degree or more foil will require more than an UptiP foil-just a fact. So if power is limited an uptip foil will be considered. Another thing: the foil that requires constant adjustment is done by a person-skipper or ?-automatic foil control is illegal.

 

Oracle Sam Greenfield, Bar- team, France Didier Ravon:

post-30-0-82468300-1467380039_thumb.jpg

post-30-0-74509000-1467380078_thumb.jpg

post-30-0-52975800-1467380770_thumb.jpg

post-30-0-17143400-1467381096_thumb.jpg

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Tom Speer doesn't say that surface piercing foils do not work but that it is not the faster configuration and not the only way for auto stability.

The best is the L well under water, but for a couple of reasons (control ?) other solutions may be better.

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".....and you say they have no relevance?"

 

No Doug, we are saying it is you that has no relevance.

 

Every time you look to support your argument you come back with outdated and irrelevant examples and even ones that are not AC, let alone this cycle. e.g Osprey, Tri Foiler, GC32 and so on. This is an AC forum about their foils.

 

The foil shape is L - shaped (driven by the AC rule) and the level of turn is more or less 90 degrees. However it is no longer (in this current AC cycle) an uptip type of leeway coupling in operation. The foils get canted inward or outward and the tips have varying lengths and curvature and a hundred other things going on. But it is the foil control systems increased complexity and accuracy that enables stable flight, not the first generation AC72 style foils where the inward cant of the vertical was balanced by the upward slant of the tip allowing automatic ride height and foil stability.

 

That is the fundamental point that you are missing.

 

However, because all you see is an L shaped foil you believe that uptip is still the primary flight control that is being achieved.

 

So, go away, stop your bleating, recognise that the game has moved on (and left you behind) and apply the golden rule - One mouth, Two ears - if you are talking more than one third of the time in any conversation - then something has gone wrong.

 

If you tot up all the postings you make up, about shit you no longer have a handle on, then you will understand why your earn no respect.....

 

I take no pleasure in being blunt - however, time and again you fail to respond to anything else.

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boink, you simply don't know what you're talking about. Canting foils are not new-neither are 90 degree foils. 90 degree foils may or may not have an up-tip but they still operate with some degree of leeway coupling-which I would have thought you might know. The GC32- and the thinking behind those foils- is certainly relevant to the AC since Martin Fischer(GC32 designer) is working with Team France-another fact you didn't know.

Further, at least four of the Teams are using UptiP foils!

You bumble around with your BS talking about things like "footprint" which you don't understand- and mis-defined in one of your last ridiculous ramblings(post 312)*-and leeway coupling of which you have no clue.

 

* boink's use of a classic mis-definition of "footprint: " Furthermore, by canting a more "open shaped" foil outboard will increase RM by widening the footprint."

This is simply ignorant: "footprint" is defined as the distance between the rudder foil and main foil or more specifically from the center of lift of the rudder foil to the center of lift of the main foil. It has absolutely nothing to do with "increasing RM"!! There is no "footprint" because the windward foil is not in the water!!

------

 

More from Tom Speer:

 

"So if the two panels were at 90 deg and there was no change in angle of attack on the horizontal wing from leeway alone, there would be an increase in lift on the horizontal wing due to the increase in leeway as the boat flew higher, and the heave stability would be unstable.

This is why an L foil needs to have some dihedral in order to be neutrally stable. The neutral stability dihedral angle is not at 90 degrees, as one might expect. Just what dihedral angle is neutrally stable depends on the planform shapes of the wing and vertical blade, the cant angle of the blade, etc."

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He has been part of Team USA(Oracle) in the past. Not sure if he still is.

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I think there may be some misunderstanding of the capability of the advances being made in foil control systems. It is completely illegal to have an automatic foil control system-regardless of improvements the foil rake angle must still be adjusted by a person! Electronics, gyros, etc are not legal. So when you consider foil control system improvements remember that the bottom line is human foil control. As I understand it, there have been significant improvements in the response time(and accuracy) of the foil control system to human input which is one of the things Oracle did better than anybody else in the later part of 34.

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If he does, perhaps there is more to his theories that he is not revealing. Surely he would not reveal any IP deemed important or advantageous to his team that was not already common knowledge.

 

BTW, please continue with your own theories. I know nothing about how foils work (other than basic principles) and I find this discussion rather fascinating. Thanks y'all.

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boink, you simply don't know what you're talking about. Canting foils are not new-neither are 90 degree foils. 90 degree foils may or may not have an up-tip but they still operate with some degree of leeway coupling-which I would have thought you might know. The GC32- and the thinking behind those foils- is certainly relevant to the AC since Martin Fischer(GC32 designer) is working with Team France-another fact you didn't know.

Further, at least four of the Teams are using UptiP foils!

You bumble around with your BS talking about things like "footprint" which you don't understand- and mis-defined in one of your last ridiculous ramblings(post 312)*-and leeway coupling of which you have no clue.

 

* boink's use of a classic mis-definition of "footprint: " Furthermore, by canting a more "open shaped" foil outboard will increase RM by widening the footprint."

This is simply ignorant: "footprint" is defined as the distance between the rudder foil and main foil or more specifically from the center of lift of the rudder foil to the center of lift of the main foil. It has absolutely nothing to do with "increasing RM"!! There is no "footprint" because the windward foil is not in the water!!

------

 

More from Tom Speer:

 

"So if the two panels were at 90 deg and there was no change in angle of attack on the horizontal wing from leeway alone, there would be an increase in lift on the horizontal wing due to the increase in leeway as the boat flew higher, and the heave stability would be unstable. [/size]This is why an L foil needs to have some dihedral in order to be neutrally stable. The neutral stability dihedral angle is not at 90 degrees, as one might expect. Just what dihedral angle is neutrally stable depends on the planform shapes of the wing and vertical blade, the cant angle of the blade, etc."[/size]

Doug!... building a few RC model does not make you a hydrodynamics guru. In fact it works against you due to many mitigateing factors.

 

Just looking at you drawings above shows you have very little understanding of what is involved, other than what you cut n paste from real gurus.

 

Stick to your models dude.

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I think there may be some misunderstanding of the capability of the advances being made in foil control systems. It is completely illegal to have an automatic foil control system-regardless of improvements the foil rake angle must still be adjusted by a person! Electronics, gyros, etc are not legal. So when you consider foil control system improvements remember that the bottom line is human foil control. As I understand it, there have been significant improvements in the response time(and accuracy) of the foil control system to human input which is one of the things Oracle did better than anybody else in the later part of 34.

Human foil control???... want the heck are you smoking. As soon as you introduce Even just a block and tackle or a manually pumped hydraulic system that, is not automated, you have stepped from human to mechanical.

 

The automated "next step" can see foils finitely finely tuned without technically being automated.

 

The foil control is semi automated right know. It's just done in two / three basic steps.

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boink, you simply don't know what you're talking about. Canting foils are not new-neither are 90 degree foils. 90 degree foils may or may not have an up-tip but they still operate with some degree of leeway coupling-which I would have thought you might know. The GC32- and the thinking behind those foils- is certainly relevant to the AC since Martin Fischer(GC32 designer) is working with Team France-another fact you didn't know.

Further, at least four of the Teams are using UptiP foils!

You bumble around with your BS talking about things like "footprint" which you don't understand- and mis-defined in one of your last ridiculous ramblings(post 312)*-and leeway coupling of which you have no clue.

 

* boink's use of a classic mis-definition of "footprint: " Furthermore, by canting a more "open shaped" foil outboard will increase RM by widening the footprint."

This is simply ignorant: "footprint" is defined as the distance between the rudder foil and main foil or more specifically from the center of lift of the rudder foil to the center of lift of the main foil. It has absolutely nothing to do with "increasing RM"!! There is no "footprint" because the windward foil is not in the water!!

------

 

More from Tom Speer:

 

"So if the two panels were at 90 deg and there was no change in angle of attack on the horizontal wing from leeway alone, there would be an increase in lift on the horizontal wing due to the increase in leeway as the boat flew higher, and the heave stability would be unstable.

 

This is why an L foil needs to have some dihedral in order to be neutrally stable. The neutral stability dihedral angle is not at 90 degrees, as one might expect. Just what dihedral angle is neutrally stable depends on the planform shapes of the wing and vertical blade, the cant angle of the blade, etc."

What a great quote.

 

Trying to come to terms with neutral stability, and "there would be an increase in lift on the horizontal wing due to the increase in leeway as the boat flew higher".

 

For some reason I have always assumed greater leeway on a horizontal foil results in a decrease in lift. If for no other reason than the flow "sees" a wider and perhaps less efficient cross-section.

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I’m having trouble trying to visualize how "leeway-coupling" works in reducing heave. I can see that as the boat rises above the desired ride height the area of the vertical foil in the water reduces, thus reducing the force resisting leeway and so the boat moves to leeward.

 

My question is; does the coupling rely on the wake (or downwash) from the vertical foil somehow impinging on the horizontal foil (which I'm finding very hard to visualize), OR does the coupling rely on the change in apparent flow direction that the horizontal foil "sees" as it is moved sideways when heaved either up or down?

 

If it is the latter, then I think I can visualize how the apparent AOA of the horizontal foil could reduce or increase lift, and I can see how this effect would not be as great on a horizontal foil as it would be on an inclined foil - ie, a foil with some degree of dihedral.

 

I'm sure the explanation is far more complex than this scenario but Speer does not go into detail.

 

My head hurts but it’s fun trying to understand it!

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Read Toms explanation of leeway coupling above(post 365) again. Here is an excerpt that may help:

 

The curved part of the vertical foil produces essentially the same lift as it rises. This is necessary to counter the side force from the sail rig, which does not change as the height changes.

 

The force resisting leeway does not change-the leeway angle increases.

Because the horizontal lift is constant but the vertical area is reduced as the boat rises, the leeway angle increases. It is the coupling of leeway with heave that is exploited by the L foil to provide vertical static stability.

The dihedral angle of the horizontal wing is set so that the angle of attack of the wing is reduced as the leeway angle increases. This satisfies the static stability condition that the vertical lift decrease as the heave increases.

Because the same horizontal lift is produced over a reduced vertical span, the sideways wash in the wake is also greater and the trailing vortices are more intense. This causes a coupling with the horizontal wing that increases the