Tornado-Cat

The winning foils

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Simon do you know why they have a bow down attitude!.. by your statement above you obviously do not!....

 

Interesting?....

I do actually know why they have bow down attitude. It's faster. It really is that simple. Maybe I was being a bit modest or guarded when i said "my best guess", but all the testing i have done, both in practice and in theory, says there is a significant aerodynamic advantage. However, i have to be a bit guarded because the testing i am doing is based on an 18' cat (A Class).

 

CFD results show that with a bow down attitude, you get a better flow over the deck/tramp which compliments the end plate effects of the deck sweeping rigs, The last thing you want is separation and therefore disrupted airflow at the front beam, because that vastly reduces the end plate effect. Even with rigs that don't properly deck sweep, there seems to be a gain by having the flows well sorted over the initial part of he track. Having bow down attitude gives you the widest range of movement before you get separation off the front beam.

 

Even on a boat with no deck sweeping/end plate rig, it seems that a bow down attitude still sorts the airflow around the bottom of the rig better than bow up.

 

I am far less certain about whether being bow down simply gives a better distribution of loading between the 2 foils but suspect there is some secondary effect in this area. This is far harder to model (certainly well above my pay grade), so it is hard to be so definitive. I also believe that sailing with bow down gives the greatest sense of "security". The boat simply feels far less likely to get away from you.

 

But as i said, this is all based on testing on an A Class. I believe the results are transferable to the AC boats, but i have never modeled and AC boat (why would I) and when i speak to AC team designers, I never put them in a position where they have to decide whether or not to disclose any of their team research. I am simply happy that they give me feedback on my A Class work.

 

Having said all of that, what really counts is on the water, and there we know that bow down is fastest. In the end, that is all that matters. If I go out and test an idea and it works out to be faster, I certainly don't dismiss the results because I might not fully understand every detail of why it is faster.

 

 

interesting..

Wonder if you'd get better overall aero if instead of bow down, the design incorporated level trim with an appropriate upward angle of the tramp from fore to aft to get that improved end-plate on the rig without creating as much aero drag on the hulls?

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Wonder if you'd get better overall aero if instead of bow down, the design incorporated level trim with an appropriate upward angle of the tramp from fore to aft to get that improved end-plate on the rig without creating as much aero drag on the hulls?

 

Possibly, but there is a high probability that this would be a very fine line to chase particularly the bold part - the upward angle would start to also create some downforce much like the ground effect of race cars ( the hulls bordering the tramp area act as pseudo endplates on the underside flow further accelerating this flow).

 

I suspect that in the A Cats where everything is so dynamic (watch some of the recent worlds footage) - that having a trim with low drag and really good seal between foot of main and tramp would be the current optimum. Reducing hull volume even more to lessen aero drag seems to be the lowest hanging fruit in terms of gains to still be had.

 

Are end plates at the head of the main permitted to reduce vortex creation?

It seems to be the one remaining open aero edge that no class of sailboat currently deals with. It has been subject to some work by the French but that was some considerable time ago.

 

 

 

 

 

 

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Squaretop Jib endplate on Aussie 18 recently:

 

2q02dci.jpg

 

 

Combination low drag wing tip/buoyancy pod on RC Test Model foiling trimaran:

 

14uaqms.jpg

 

 

 

 

 

Wing Tip Rig-low drag tip on first production sailing RC foiler(16 years ago):

 

281r97k.jpg

 

 

 

 

Winglets on a C Class-not particularly successful as I remember it:

 

 

vh8ef4.jpg

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Those C-class ones were Alpha c.2007 & the Lumix rig in the 18's was for the '12-'13 season and not successful - so neither were recent or relevant to where design and materials are today.

 

Winglets/Endplates make sense where there are rule restrictions to extending span - and the AC wing package ticks that box.

 

I am not going to comment on the relevance of your efforts.

 

Anyone else have thoughts/insight?

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t3

clik

13576908_964478487004154_803835013355025

can't scrub the image of this board from my eyes.

 

What's with that 'bump'?

 

Thinking this board can't be real - perhaps they are just testing a tip section.

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I'm not sure it's legal but Dario Valenza wrote this a year or so ago. The idea of downforce from the windward rudder and its interaction with and effect on the total pitch control of the boat needs to be looked at carefully. I haven't been able to find any articles by any team corroborating the "work with AC 45 Turbo test platforms" referred to below:

 

Dario Valenza-

It is inescapable that we must be able to get all our upward lift from our leeward foil if we ever want to be able to efficiently foil upwind. Also if we want to foil in light airs downwind, and if we want to keep pushing max speed downwind in fresher conditions.

Recent work with AC45 Turbo test platforms, and smaller cats, has shown that differential rudder rake, such that the windward elevator foil produces downforce, can add significant speed. (emphasis DL)
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Why do you suggest that is not legal?

 

There are no restrictions on the surrogates at all in this regard.

 

But assuming that it's the ACC boats that are of interest and for which this technique is ultimately intended, there are still no limits on the rudders being used in this way - as long as the 3° rake limits (10.4) are respected.....

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No limits but interest ?

I met last week the crew of a foiling C class cat, I asked him why they pp at last world championship in Swizerland: " As we had problem with our main foil we compensated with a negative aoa on the rudder. Result, at the first gust it went out of the water and we pitch poled".

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No limits but interest ?

I met last week the crew of a foiling C class cat, I asked him why they pp at last world championship in Swizerland: " As we had problem with our main foil we compensated with a negative aoa on the rudder. Result, at the first gust it went out of the water and we pitch poled".

 

TC, wouldn't a negative AOA on the rudder foil pull down rather than lift? Were they saying the foil stalled?

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No limits but interest ?

I met last week the crew of a foiling C class cat, I asked him why they pp at last world championship in Swizerland: " As we had problem with our main foil we compensated with a negative aoa on the rudder. Result, at the first gust it went out of the water and we pitch poled".

 

TC, wouldn't a negative AOA on the rudder foil pull down rather than lift? Were they saying the foil stalled?

 

 

Do try to keep up. that differential rudder rake, such that the windward elevator foil produces downforce, can add significant speed

 

TC was pointing out again the potential pitfall

 

The same issue was referred to earlier in the thread, with regard to adding RM via the main ww foil - you gain RM up until the moment that foil leaves the water, (or loses neg lift for any number of other reasons) - and you are then instantly overpowered and flip

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This doesn't look very winning...

 

https://www.instagram.com/p/BGE8MLYrn6W/?taken-by=sailingshack

 

13329179_1782466271999598_1708263060_n.j

 

Why would you knock a couple of kids hauling ass on an experimental foiler? Looks like a lot of fun to me......

 

 

j83cs4.jpg

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No limits but interest ?

I met last week the crew of a foiling C class cat, I asked him why they pp at last world championship in Swizerland: " As we had problem with our main foil we compensated with a negative aoa on the rudder. Result, at the first gust it went out of the water and we pitch poled".

 

TC, wouldn't a negative AOA on the rudder foil pull down rather than lift? Were they saying the foil stalled?

 

 

Do try to keep up. that differential rudder rake, such that the windward elevator foil produces downforce, can add significant speed

 

TC was pointing out again the potential pitfall

 

The same issue was referred to earlier in the thread, with regard to adding RM via the main ww foil - you gain RM up until the moment that foil leaves the water, (or loses neg lift for any number of other reasons) - and you are then instantly overpowered and flip

 

 

Gee thanks ,nav-if you weren't there to explain it I'd never get it. So you do realize that the C cats have two rudder foils and what you seem to be saying is that when the C Class guy said "neg AOA on the rudder" he was talking about the windward rudder? So when the windward rudder foil came clear of the water the boat pitchpoled? What was the lee rudder foil doing during this period? There is more to this story than you seem to have the capability to understand. I was hoping to learn more detail.

On the boats that use 2 wand controlled main foils, the windward foil will generate downforce BUT it is NOT a given that if the windward foil pops out while developing downforce that the boat will capsize(or pitchpole)-that is an old wifes tale from people who have never sailed such a boat. And that's what makes me think there is more detail to TC's story.

If the lee rudder foil was doing it's normal job and the windward rudder foil was set to develop downforce it seems like a real stretch to say that when the windward rudder foil popped out of the water that led to a pitchpole-there must be more to the story. When the windward rudder foil popped out the pitch attitude of the boat would change and the lee rudder foil would instantly develop loads of downforce which seems it might prevent a pitchpole-or at least give the crew time to react.

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Are you saying that - on a cat with two rudders - they are adjusting the rudder stabiliser/elevator foils independently, and that they are (sometimes) using them for LIFT?

 

You do realise that the stabiliser foil on the kite foils, windsurfer foils and the SUP/surf foils are all designed to produce down force, just like those on a plane, right?

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Are you saying that - on a cat with two rudders - they are adjusting the rudder stabiliser/elevator foils independently, and that they are (sometimes) using them for LIFT?

 

You do realise that the stabiliser foil on the kite foils, windsurfer foils and the SUP/surf foils are all designed to produce down force, just like those on a plane, right?

 

Rudder t-foils on multifoilers start out lifting up then at an automatic crossover point begin to pull down-again, completely automatically(or manually controlled on some multifoilers). I'm still not sure of the setup that TC was talking about on the C Class cat. The rudder T-foil will LIFT as the boat starts to foil-lifting 15-20% of the total weight. As it speeds up the amount of vertical lift from the rudder t-foil will go down and is replaced automatically by downforce at a certain point on many multifoilers.

What Dario said(quoted post 516) previously was that differential control of the rudder foils may be beneficial in increasing RM. That would depend on the design of the foil system,the specific characteristics of rudder foil loading throughout the speed range and the set-up of the boat. But it is possible.

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Are you saying that - on a cat with two rudders - they are adjusting the rudder stabiliser/elevator foils independently, and that they are (sometimes) using them for LIFT?

 

You do realise that the stabiliser foil on the kite foils, windsurfer foils and the SUP/surf foils are all designed to produce down force, just like those on a plane, right?

 

Rudder t-foils on multifoilers start out lifting up then at an automatic crossover point begin to pull down-again, completely automatically(or manually controlled on some multifoilers). I'm still not sure of the setup that TC was talking about on the C Class cat. The rudder T-foil will LIFT as the boat starts to foil-lifting 15-20% of the total weight. As it speeds up the amount of vertical lift from the rudder t-foil will go down and is replaced automatically by downforce at a certain point on many multifoilers.

What Dario said(quoted post 516) previously was that differential control of the rudder foils may be beneficial in increasing RM. That would depend on the design of the foil system,the specific characteristics of rudder foil loading throughout the speed range and the set-up of the boat. But it is possible.

 

 

This is complete and utter bullshit. The main lifting foil is relatively close to the Cg, whereas the rudder is approximately half the length of the hull from the Cg. So if the rudder foils were developing 15-20% of the lift, that vertical force combined with the moment arm would cause an instant nose dive and crash.

 

During actual stabile foiling flight, the main foils are still aft of the CG - just like a plane - which means that the stabilisers (rudder foils) must by necessity be providing a downward force. The rig also provides a pitching moment (forward and down) around the rotational axis defined by the the Cg position.

 

So no - without moving the Cg AFT of the main foils (or moving the main foils forward of the Cg), it is NOT 'possible'.

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Foilers designed with a conventional "airplane" configuration(large main foils fwd, small rudder foils aft) do very well with around 80% of the load on the main foils and around 20% on the rudder foils. Examples are the Rave, Osprey and Skat and there are many others that are similar. The foil loading(lbs/sq.ft.) of the main foils should be greater than that of the rudder foils. The CG is aft of the main foils! The angle of incidence on the mainfoils is around +2.5 degrees(wand controlled foils) and set at zero degrees on the rudder foil-both set relative to the static waterline(which on the boats mentioned is parallel to the flight waterline after takeoff).

 

 

AC 72 CG in sketch by Francois Chevalier-Note this is a foiling configuration after the crossover point mentioned in a previous post(526) because it shows the rudder foil pulling down to balance the force at the Center of Effort. At takeoff, the rudder foils would be LIFTING!

Note that the CG is AFT of the main foils.......

 

 

25k4w11.jpg

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CnzsBJWWYAAXoLF.jpg

 

When the foil designer has one alcoholic beverage too many... 8-)

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Foilers designed with a conventional "airplane" configuration(large main foils fwd, small rudder foils aft) do very well with around 80% of the load on the main foils and around 20% on the rudder foils. Examples are the Rave, Osprey and Skat and there are many others that are similar. The foil loading(lbs/sq.ft.) of the main foils should be greater than that of the rudder foils. The CG is aft of the main foils! The angle of incidence on the mainfoils is around +2.5 degrees(wand controlled foils) and set at zero degrees on the rudder foil-both set relative to the static waterline(which on the boats mentioned is parallel to the flight waterline after takeoff).

 

 

AC 72 CG in sketch by Francois Chevalier-Note this is a foiling configuration after the crossover point mentioned in a previous post(526) because it shows the rudder foil pulling down to balance the force at the Center of Effort. At takeoff, the rudder foils would be LIFTING!

Note that the CG is AFT of the main foils.......

 

 

25k4w11.jpg

At take off - which requires maximum thrust to overcome the very high level of drag before the boat lifts off - the pitching moment induced by the rig would be at it's greatest. So no, you are utterly wrong about the stabilisers (rudder foils) providing anything but down force. Which Chevalier's drawing clearly shows.

 

Apparently (my bad) the Cg is slightly aft of the main foils (although still close enough for horse shoes), but regardless the pitching moment induced by the rig would more than offset that - in other words it is hard to imagine a scenario where the rudder foils would be required to produce any vertical lift much less the ridiculous 20% you are asserting.

 

Besides, how on earth - even ignoring all the rest of the basic physics as you are - do you imagine those tiny rudder foils could produce 20% of the massive lift of the giant main foils? 20% of 13000 lbs is 2600 lbs - you seriously think the rudder foils could produce that amount of lift, never mind the insane pitching moment (read 'nose dive from hell') that 2600 lbs of lift at the extreme tail end of the hull would produce?

 

Seriously, dude.

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Have you ever watched a foiler take off? In almost every case you will notice that the boat is pitched up and as it goes faster it pitches down. Thats why many rudder foils are symmetrical sections: because they have to lift up and lift down at different times throughout the course of the speed range.

The fact that the CG is aft of the main foil should tell you that the rudder foils are carrying part of the load at takeoff and for a bit after that depending on the boat and conditions. Saying the pitching moment is greatest at the boats slowest speed(takeoff) is very wrong. Not understanding that the rudder foils on many foilers both lift up and create downforce-at different times- is unfortunate. Especially after you admit you were wrong about the position of the CG.

 

 

 

Are you saying that - on a cat with two rudders - they are adjusting the rudder stabiliser/elevator foils independently, and that they are (sometimes) using them for LIFT?

 

You do realise that the stabiliser foil on the kite foils, windsurfer foils and the SUP/surf foils are all designed to produce down force, just like those on a plane, right?

 

Rudder t-foils on multifoilers start out lifting up then at an automatic crossover point begin to pull down-again, completely automatically(or manually controlled on some multifoilers). I'm still not sure of the setup that TC was talking about on the C Class cat. The rudder T-foil will LIFT as the boat starts to foil-lifting 15-20% of the total weight. As it speeds up the amount of vertical lift from the rudder t-foil will go down and is replaced automatically by downforce at a certain point on many multifoilers.

What Dario said(quoted post 516) previously was that differential control of the rudder foils may be beneficial in increasing RM. That would depend on the design of the foil system,the specific characteristics of rudder foil loading throughout the speed range and the set-up of the boat. But it is possible.

 

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Have you ever watched a foiler take off? In almost every case you will notice that the boat is pitched up and as it goes faster it pitches down. Thats why many rudder foils are symmetrical sections: because they have to lift up and lift down at different times throughout the course of the speed range.

The fact that the CG is aft of the main foil should tell you that the rudder foils are carrying part of the load at takeoff and for a bit after that depending on the boat and conditions. Saying the pitching moment is greatest at the boats slowest speed(takeoff) is very wrong. Not understanding that the rudder foils on many foilers both lift up and create downforce-at different times- is unfortunate. Especially after you admit you were wrong about the position of the CG.

 

 

Have you ever watched a plane take off? Of course the boat is pitched up when it takes off - the main lifting foils need a higher angle of attack to produce the same vertical lift at lower speeds. During take off on a plane, the elevators are used to produce downwards force, to increase the angle of attack of the wings. I suppose since the stabilisers on the rudders were not adjustable, they would produce some lift during extreme tail-dragging scenarios - but that is not their primary function.

 

And sure, there are lots of stabilisers with symmetrical sections - but for symmetrical sections to produce 20% of the lift of the main foils, they would need to be on the order of 20% of the size (at least) of the main foils.

 

And finally, you've once again conveniently ignored the pitching moment induced by the rig, not to mention the fact that the drag (the other half of that pitching relationship) actually drops when the boat gets up on foils - that's why it goes faster on foils. So during take off, you have high drag, which necessitates a lot of forward thrust from the wing (EG pitching moment) to get going which equates to a BIG pitching moment. Which would require downforce from the stabiliser(s).

 

Draw a free-body diagram of all the forces and moments if you can't visualise this.

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The boats that I know the exact details on-Rave, Osprey and SKAT have a single rudder foil that is 50% of the area of the combined total area of the two main foils but has about 51% of the foil loading of the main foils at takeoff. Most "airplane config" foilers would be somewhat similar.

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The boats that I know the exact details on-Rave, Osprey and SKAT have a single rudder foil that is 50% of the area of the combined total area of the two main foils but has about 51% of the foil loading of the main foils at takeoff. Most "airplane config" foilers would be somewhat similar.

 

This is a thread about the winning foils in the America's Cup.

 

But you're wrong about the 'airplane foils', at least insofar as they apply to kites, windsurfers, SUPs and surfboards - the stabilisers provide downforce, just like a plane.

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The principle is the same whether it's a 16' Rave foiler tri,18' Osprey foiler tri, 40' SKAT foiler tri or an AC 45 , 50 or 72 foiler cat........

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The principle is the same whether it's a 16' Rave foiler tri,18' Osprey foiler tri, 40' SKAT foiler tri or an AC 45 , 50 or 72 foiler cat........

 

The Osprey for example, uses 3 identical T-foils - I could imagine a fairly even lift distribution. The AC 72s used 2 massive J foils and had tiny, fixed stabilisers on the rudders. The idea that the tiny, non-adjustable rudder foils on the AC 72s produced 20% of the lift is ridiculous.

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The AC 72 used a single uptip foil on the lee side. Both rudders were immersed and they would lift together 25%(12.5% each) of the total load at takeoff and the main foil would lift 75% at takeoff IF Chevaliers sketch is accurate.

Trailing rudder foils don't need to be adjustable to work. They lift at takeoff and begin to pull down at a crossover point as the boat speeds up. Their performance can be enhanced by having their angle of incidence adjustable while flying but there are many foilers whose rudder foils are not adjustable under sail that work just fine.

 

Keep in mind that takeoff speed for an AC 72 was about 23 knots............

http://www.yachtsandyachting.com/news/176256

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The AC 72 used a single uptip foil on the lee side. Both rudders were immersed and they would lift together 25%(12.5% each) of the total load at takeoff and the main foil would lift 75% at takeoff IF Chevaliers sketch is accurate.

Trailing rudder foils don't need to be adjustable to work. They lift at takeoff and begin to pull down at a crossover point as the boat speeds up. Their performance can be enhanced by having their angle of incidence adjustable while flying but there are many foilers whose rudder foils are not adjustable under sail that work just fine.

 

Keep in mind that takeoff speed for an AC 72 was about 23 knots............

http://www.yachtsandyachting.com/news/176256

 

You're full of shit. 100% of the lift was provided by the lifting foils. The elevators (horizontal rudder foils) provide stability, nothing more - and most of that time, providing stability means generating down force. The size of the elevator foils was determined by finding the best compromise between stability (making them larger) and reducing drag (making them smaller), as Pete Melvin notes in the article below:

 

http://www.cupinfo.com/en/americas-cup-pete-melvin-foils-multihulls-13146.php

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On airliners, when only 40% of the seats are occupied, the pilot ask the passengers to seat mostly at the rear

in order to move te CoG aft and compensated by a little positive trim (positive lift) on stabilizer.

This arrangement was required by the company, in an attempt to make jet-fuel economy.

The rational behind it is the little lift (Cz<0.2)provided by the stabilizer will alleviate the lift required from the wing in order to decrease the induced drag of the wing, and decrease the overall drag, because the increase in stabilizer induced drag is more than offset by the decrease in the wing's induced drag.

 

So for performance (speed) I guess a little positive lift could be beneficial, but for stability, the AoA should become negative quickly when the boat starts to pitch.

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The AC 72 used a single uptip foil on the lee side. Both rudders were immersed and they would lift together 25%(12.5% each) of the total load at takeoff and the main foil would lift 75% at takeoff IF Chevaliers sketch is accurate.

Trailing rudder foils don't need to be adjustable to work. They lift at takeoff and begin to pull down at a crossover point as the boat speeds up. Their performance can be enhanced by having their angle of incidence adjustable while flying but there are many foilers whose rudder foils are not adjustable under sail that work just fine.

 

Keep in mind that takeoff speed for an AC 72 was about 23 knots............

http://www.yachtsandyachting.com/news/176256

 

You're full of shit. 100% of the lift was provided by the lifting foils. The elevators (horizontal rudder foils) provide stability, nothing more - and most of that time, providing stability means generating down force. The size of the elevator foils was determined by finding the best compromise between stability (making them larger) and reducing drag (making them smaller), as Pete Melvin notes in the article below:

 

http://www.cupinfo.com/en/americas-cup-pete-melvin-foils-multihulls-13146.php

 

 

You're contradicting the facts and your own words! If the CG is where Chevalier says it is there is no doubt what the loading is for the main foils and rudder foils at takeoff-it's just physics.

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CnzsBJWWYAAXoLF.jpg

When the foil designer has one alcoholic beverage too many... 8-)

What a rule constraint can do to an innovation borne of a rule constraint?

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The AC 72 used a single uptip foil on the lee side. Both rudders were immersed and they would lift together 25%(12.5% each) of the total load at takeoff and the main foil would lift 75% at takeoff IF Chevaliers sketch is accurate.

Trailing rudder foils don't need to be adjustable to work. They lift at takeoff and begin to pull down at a crossover point as the boat speeds up. Their performance can be enhanced by having their angle of incidence adjustable while flying but there are many foilers whose rudder foils are not adjustable under sail that work just fine.

 

Keep in mind that takeoff speed for an AC 72 was about 23 knots............

http://www.yachtsandyachting.com/news/176256

 

You're full of shit. 100% of the lift was provided by the lifting foils. The elevators (horizontal rudder foils) provide stability, nothing more - and most of that time, providing stability means generating down force. The size of the elevator foils was determined by finding the best compromise between stability (making them larger) and reducing drag (making them smaller), as Pete Melvin notes in the article below:

 

http://www.cupinfo.com/en/americas-cup-pete-melvin-foils-multihulls-13146.php

 

 

You're contradicting the facts and your own words! If the CG is where Chevalier says it is there is no doubt what the loading is for the main foils and rudder foils at takeoff-it's just physics.

 

 

The CG is only one factor that determines the load distribution on the foils .. the pressure on the rig and it's height is also a major force.

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Terry, thats absolutely true. I've tried to point out that the lift percentages I used based on the CG are accurate for takeoff only-everything changes as the boat speeds up and flies.

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The AC 72 used a single uptip foil on the lee side. Both rudders were immersed and they would lift together 25%(12.5% each) of the total load at takeoff and the main foil would lift 75% at takeoff IF Chevaliers sketch is accurate.

Trailing rudder foils don't need to be adjustable to work. They lift at takeoff and begin to pull down at a crossover point as the boat speeds up. Their performance can be enhanced by having their angle of incidence adjustable while flying but there are many foilers whose rudder foils are not adjustable under sail that work just fine.

 

Keep in mind that takeoff speed for an AC 72 was about 23 knots............

http://www.yachtsandyachting.com/news/176256

 

You're full of shit. 100% of the lift was provided by the lifting foils. The elevators (horizontal rudder foils) provide stability, nothing more - and most of that time, providing stability means generating down force. The size of the elevator foils was determined by finding the best compromise between stability (making them larger) and reducing drag (making them smaller), as Pete Melvin notes in the article below:

 

http://www.cupinfo.com/en/americas-cup-pete-melvin-foils-multihulls-13146.php

 

 

You're contradicting the facts and your own words! If the CG is where Chevalier says it is there is no doubt what the loading is for the main foils and rudder foils at takeoff-it's just physics.

 

 

Pure physics would include the huge pitching moment induced by the wing, which you have ignored for the duration of this conversation. Here's a simplified sum (I'm ignoring inertia for example) of the forces acting on an AC 72 during take off, and how they affect pitching:

 

1) Hydrodynamic Drag - prior to take off, much of this is on the hull, with a smaller percentage on the foils - at take off, the total drag sharply drops. The moment around the Cg is negligible, although it increases slightly once the boat goes up on the foils.

 

2) Net Motive force - this is the component vector of the total lift developed by the wing that acts parallel to the centerline of the boat, driving the hull forward multiplied by the L/D ratio. To make the boat accelerate, this force must be greater than the drag (which as I've noted is very high just before take off). The moment arm of this massive force is at least 1/3rd up the 130 ft span of the wing - in other words, absolutely MASSIVE. If you are looking at a drawing of the hull with the bow on the right side of the page, this moment are would act clockwise, driving the nose down.

 

3) Aerodynamic drag - Since wing drag has already been included in #2, we are only talking about aero drag of the hull/deck. This acts roughly on the same plane as the Cg, so no pitching.

 

4) Hydrodynamic lift - this is the force generated by the foil(s) that lifts the 13000 lb boat out of the water and moves the entire system into a lower drag (faster) regime. According to Chevalier's drawing, The Cg is slightly aft of the main foils. The foil position is first designed for steady flight, so we can safely assume that at steady flight (shown in the drawing), 100% of the lift ('heave') keeping the boat out of the water is coming from the main foils. Which, coincidentally, the drawing shows. But we are talking about take off. At take off, the main lifting foils need maximum angle of attack to heave that 13,000 lbs out of the water, and the net motive force is huge, and forcing the bow down. If the stabilizers were providing any upward force much less the ridiculous 20% you are asserting, that angle of attack of the main foils - which the massive pitching moment of the motive force is already trying to unwind - would be further reduced, not increased, and the boat would flop back into the water.

 

So your 'percentages' are BS.

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CnzsBJWWYAAXoLF.jpg

When the foil designer has one alcoholic beverage too many... 8-)

What a rule constraint can do to an innovation borne of a rule constraint?

Yes, one presumes that someone with better knowledge and computer modelling than anyone resident here did this on purpose...

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^ Foil?

 

I posted that because I couldn't believe TF would ever accept such a tacky carpet

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You've seen what they'll eat, right? A tacky carpet is the least of their worries...

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The AC 72 used a single uptip foil on the lee side. Both rudders were immersed and they would lift together 25%(12.5% each) of the total load at takeoff and the main foil would lift 75% at takeoff IF Chevaliers sketch is accurate.

Trailing rudder foils don't need to be adjustable to work. They lift at takeoff and begin to pull down at a crossover point as the boat speeds up. Their performance can be enhanced by having their angle of incidence adjustable while flying but there are many foilers whose rudder foils are not adjustable under sail that work just fine.

 

Keep in mind that takeoff speed for an AC 72 was about 23 knots............

http://www.yachtsandyachting.com/news/176256

 

You're full of shit. 100% of the lift was provided by the lifting foils. The elevators (horizontal rudder foils) provide stability, nothing more - and most of that time, providing stability means generating down force. The size of the elevator foils was determined by finding the best compromise between stability (making them larger) and reducing drag (making them smaller), as Pete Melvin notes in the article below:

 

http://www.cupinfo.com/en/americas-cup-pete-melvin-foils-multihulls-13146.php

 

 

You're contradicting the facts and your own words! If the CG is where Chevalier says it is there is no doubt what the loading is for the main foils and rudder foils at takeoff-it's just physics.

 

 

Pure physics would include the huge pitching moment induced by the wing, which you have ignored for the duration of this conversation. Here's a simplified sum (I'm ignoring

So your 'percentages' are BS.

 

 

Wrong! Based on Chevaliers position of the CG, 75% of the total weight is on the main foil which for a 12760lb boat is 9570lb. And the two rudder foils support 3190lb(25%) or 1595lb each. The rig pitching moment during takeoff is offset by the fact that the CG is aft of the main foils.

If the position of the CG was slightly forward with 80% of the weight on the main foil (10208lb) the rudder foils would support 20%(2552lb or 1276lb each).

==================================

These configurations are for takeoff only-as the boat speeds up the lift from the rudder foils would decrease as the boat pitches down until there is neg lift on the rudder foils and the main foil loading would increase by the difference.

==================================

 

75/25=At 23 knots takeoff speed with a 2 degree pitch up of the boat, the rudder foil area for each rudder would be 2.63 sq.ft.-in other words "tiny"!

 

80/20= At 23 knots takeoff speed with a 2 degree pitch up of the boat, the rudder foil area for each rudder would be 2.1sq.ft-in other words "tinier"!

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Wrong! Based on Chevaliers position of the CG, 75% of the total weight is on the main foil which for a 12760lb boat is 9570lb. And the two rudder foils support 3190lb(25%) or 1595lb each. The rig pitching moment during takeoff is offset by the fact that the CG is aft of the main foils.

If the position of the CG was slightly forward with 80% of the weight on the main foil (10208lb) the rudder foils would support 20%(2552lb or 1276lb each).

==================================

These configurations are for takeoff only-as the boat speeds up the lift from the rudder foils would decrease as the boat pitches down until there is neg lift on the rudder foils and the main foil loading would increase by the difference.

==================================

 

75/25=At 23 knots takeoff speed with a 2 degree pitch up of the boat, the rudder foil area for each rudder would be 2.63 sq.ft.-in other words "tiny"!

 

80/20= At 23 knots takeoff speed with a 2 degree pitch up of the boat, the rudder foil area for each rudder would be 2.1sq.ft-in other words "tinier"!

 

 

The position of the Cg shown in Chavalier's drawing could either offset the pitching moment of the rig, or redistribute the load on the foils the way you've described. It can't do both. Since the rig exists - check the photos if you don't believe me - your distribution claims are incorrect.

 

1 does NOT = 1+1.

 

It would also be very inefficient (draggy and slow) to use stabilisers to do any heavy lifting.

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I am curious - as the role of the stabilizers has always puzzled me. Basiliscus was nice enough to drop his lecture notes in from the cloud.

 

The following bullets from slide 7 of Speer's A Class foiling slide deck:

 

Pitch stability

- Aft foil less heavily loaded than forward foil (per m2)

- Weight forward

 

Pitch-heavecoupling

- Forward foil has higher heave stiffness than aft foil

- Fully submerged aft foil (T rudders)

- Stern-first takeoff

 

Yep. Stern first takeoff. Just what we see the boats doing every day. So it baffles me a bit the assumption of bow first takeoff above.

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I've never noticed a stern first takeoff-got any video? If that was desirable it would probably be a piece of cake to tweak the foils to allow it particularly with adjustable rudder foils but even without them. Same with a nosedown attitude which I have seen a lot of particularly with Oracle.

 

Tom Speers A Class presentation: http://www.tspeer.com/Aclass/A-ClassCatamaranFoils.pdf

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Perhaps it's a perception or nomenclature issue - but I used to watch the boats do this regularly. Always figured it was what they were shooting for, as it looked quite controlled and elegant.

 

In any case - its right there in Tom's presentation. Slide 7.

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Well, I watch this stuff as often as possible and have many hours on a Rave but I've never seen stern first liftoff-or should I say-I've never noticed a foiler with the stern lifting off first-but I'd like to. I don't understand the reason for it-but I'd like to as well.

I'd love to read a clear cut explanation of the idea-I've read Toms presentation but it's not real clear to me.

If you could post one of the videos where you've seen this I'd sure appreciate it........

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Why even discuss this?

douGh boY knows nothing - yet quotes Osprey and Skat as his point of reference. Good one.....

He moves to AC72's - no longer in the picture either. They could adjust the AOA on the main foils only, with the Rudder stabiliser locked off for the duration (at a very slight positive AOA) of each race.

A Plane flies by adjusting AOA through the tail stabiliser and adjusting camber on the wings to account for maintenance of lift at different velocities (but not by adjusting the AOA on the wing foil itself).

A current cycle AC48/50 adjusts AOA on both Main Foil and Rudder stabiliser.

No one on this thread knows the exact foil profiles or AOA's that are implemented on either the main foil or the rudder stabiliser - nor the sequence or frequency that they alter them in. We do know that the main foils are canted in all four main axis as well as vertically. But no one has published the "crossovers" as to when that occurs.

 

The rudder stabilisers can be altered by 3 degrees - but no one knows if this is in constant adjustment (like a plane) or adjusted on a very fine basis for trim only.

 

Is that adjustment driven by sea state, wind conditions, boat velocity or course direction (upwind, downwind or reaching)? Again it is only a guess to say it will be a combination of several if not all of these factors.


Anyone who says "this is how it happens......" is only posting conjecture, and the quality of that conjecture is highly variable depending on the poster.

 

The game has moved on a long way since the last cup. Unfortunately the control systems which would give good insight into what is actually happening, are out of sight, and no one who actually knows is allowed to reveal because of proprietary knowledge and NDA's. There are only long range shots of the foils - nothing detailed or revelatory. ETNZ got burned by revealing their technology too early in the last cycle and Oracle were smart enough (& lucky enough) to move it on - but not lets get distracted by that whole story - suffice to say, no one will reveal anything that they do not have to.

There are a lot of smart people here who do have relevant inputs - most of which gets drowned out by the tidal wave of puss that emanates from fLoriDa......

I believe that Doug suffers from the Dunning-Kruger Effect.
He fits the findings very closely......
http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

 

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I suspect understanding how an A class flies could add understanding, or at least a greater appreciation, for how the AC boats fly. Similarly, I guess it's not a complete waste of time - or maybe it is! - to investigate the basis of the technology. Antique imagery below.

 

Sorry I didn't bring my tape measure - and don't recall if the rudder foil was symmetric (think so). But I guess the lifting area of a rudder foil could be 10% of a main foil.

 

post-18173-0-47091500-1469253460_thumb.jpeg

 

How elegant does this look compared to that ungainly main foil on BAR?

 

post-18173-0-59042200-1469253843_thumb.jpeg

 

Seems low aspect. Perhaps span was rule constrained.

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Why even discuss this?

 

douGh boY knows nothing -

A current cycle AC48/50 adjusts AOA on both Main Foil and Rudder stabiliser.

 

No one on this thread knows the exact foil profiles or AOA's that are implemented on either the main foil or the rudder stabiliser - nor the sequence or frequency that they alter them in. We do know that the main foils are canted in all four main axis as well as vertically. But no one has published the "crossovers" as to when that occurs.

 

The rudder stabilisers can be altered by 3 degrees - but no one knows if this is in constant adjustment (like a plane) or adjusted on a very fine basis for trim only.

 

 

 

There are a lot of smart people here who do have relevant inputs - most of which gets drowned out by the tidal wave of puss that emanates from fLoriDa......

 

I believe that Doug suffers from the Dunning-Kruger Effect.

He fits the findings very closely......

http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

 

 

boing, boing,boink....

For those that give a damn the use of "AOA" above shows boinks repertoire of misunderstood terms used for hydrofoils keeps on growing. He's previously botched the definition of "footprint" and more.

AOA refers to the angle of the flow relative to the foil. If you're talking about a setting for the adjustment of a foil you're talking about the angle of incidence(AOI) of the foil-which is a fixed ,accurate and repeatable adjustment relative to a fixed reference on the boat.

The best way to visualize the difference and why there is an "AOA" and "AOI" in foiling terminology is to consider a fixed daggerboard(or centerboard or keel). The daggerboard is fixed at or parallel to the centerline of the boat. It's angle of incidence is ZERO degrees but it's AOA is equal to the leeway angle of the boat which is not a fixed number and changes depending on the conditions and the direction the boat is heading relative to the wind.

Same with hydrofoils: the AOI is the angle relative to a fixed reference on the boat-it's a specific term and refers to a definite measurement. AOA for foils is constantly variable. AOI can be changed within the range allowed by the foil within its physical constraints but is always exactly repeatable. AOA is the angle of the foil to the approaching water which is variable due to speed, waves, leeway and other conditions.

----

Another classic example of how this can be misunderstood was in a discussion about an uptip ama foil whose vertical portion was set at +3 degrees AOI* on a boat with a fixed main daggerboard set at ZERO degrees AOI. Which one carries the majority of the lateral resistance load?

 

* the vertical portion of the ama uptip foil was angled 3 degrees to windward of a line parallel to the centerline of the boat......

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There you go again.....

I used the term AOA deliberately as it is the angle of the lifting surface within the water flow that counts.
Why? Because if you haven't noticed - many of the front running teams have adopted nose down stable flight, in certain modes, whilst running level boat attitude in other modes.

Furthermore, the daggerboard cases are cassette structures that hold the foil. We do observe how the boards are raked both fore and aft (changing the AOA) as well as being canted inboard and outboard in different sailing modes (from upright to inward).

They represent the 4 directions of movement I referred to.

 

However, consider this:
It would not be a great leap of faith to think that the teams will have also tested the capacity to twist the foil on a longuitudinal axis akin to a gybing centreboard - just limited in range from neutral to positive, and prevented from going negative.
BUT no one would yet know whether this is occurring because all the control systems are hidden and not discussed.
And before you jump on the red ink, in time honoured fashioned - think as to why they would want to twist a low drag profile rather than not twist a higher camber profile into a higher drag scenario.......)

Anyway, we can all live in hope; but yet again you choose to denigrate others in a attempt to further bolster your own false sense of superiority.

Thereby proving my accusation that you fall under the Dunning-Kruger Effect
http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

 

Classic :lol:

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Someone's socks are smelly...

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Here is a "definition" for those that don't know or can't tell an UptiP foil when they see one:

 

definition(to be applied using a picture of a deployed foil) : any foil that when it is deployed allows the more or less horizontal portion to be less than 90 degrees from a line normal(90 degrees) to the waters surface and/or when the more or less horizontal portion is less than 90 degrees from the more or less vertical portion of the foil as in the sketch:

stb hull coming at you:

post-30-0-92424400-1467666477_thumb.png

 

Doug, when this is the best you can do on your own, (rather than relying on the often completely irrelevant work of others), I don't think you are in any position to criticise - or even claim any great depth of knowledge

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There you go again.....

 

I used the term AOA deliberately as it is the angle of the lifting surface within the water flow that counts.

Why? Because if you haven't noticed - many of the front running teams have adopted nose down stable flight, in certain modes, whilst running level boat attitude in other modes.

 

Furthermore, the daggerboard cases are cassette structures that hold the foil. We do observe how the boards are raked both fore and aft (changing the AOA) as well as being canted inboard and outboard in different sailing modes (from upright to inward).

They represent the 4 directions of movement I referred to.

 

However, consider this:

It would not be a great leap of faith to think that the teams will have also tested the capacity to twist the foil on a longuitudinal axis akin to a gybing centreboard - just limited in range from neutral to positive, and prevented from going negative.

BUT no one would yet know whether this is occurring because all the control systems are hidden and not discussed. Rotation is limited to the cant axis and rake axis by rule.......

And before you jump on the red ink, in time honoured fashioned - think as to why they would want to twist a low drag profile rather than not twist a higher camber profile into a higher drag scenario.......)

 

Anyway, we can all live in hope; but yet again you choose to denigrate others in a attempt to further bolster your own false sense of superiority.

 

Thereby proving my accusation that you fall under the Dunning-Kruger Effect

http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

 

Classic :lol:

 

 

 

What nonsense!

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Here is a "definition" for those that don't know or can't tell an UptiP foil when they see one:

 

definition(to be applied using a picture of a deployed foil) : any foil that when it is deployed allows the more or less horizontal portion to be less than 90 degrees from a line normal(90 degrees) to the waters surface and/or when the more or less horizontal portion is less than 90 degrees from the more or less vertical portion of the foil as in the sketch:

stb hull coming at you:

post-30-0-92424400-1467666477_thumb.png

 

Doug, when this is the best you can do on your own, (rather than relying on the often completely irrelevant work of others), I don't think you are in any position to criticise - or even claim any great depth of knowledge

 

 

Sorry you feel that way, "nav".

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It sounds like upwind foiling is being regularly accomplished in Bermuda. I think it's gonna be who can foil tack the most effectively.

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The very first post-AC34 test boat splashed by Artemis was foiling upwind, in light air, right out of the box. This was two years ago.

 

And yes, it looked to like they were attempting to tack (and stay up) - but no success. And until we see a video...

 

I suppose the foil shape could have significance for the foiling tack. And now that you mention it - perhaps this might explain that loopy BAR foil shown above.

 

A foil not intended for max efficiency or speed - but instead to provide lift through a tack.

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I don't remember where I found this but just had time to look again at it now. Written by Martin Fischer who is working with Team France, in April 2016. For those interested in Pitch Stability scroll down to a great illustration :

https://fr.calameo.com/read/0047502132ae545e148b0

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FWIW from my own memories....

 

Yes, TV schedules have/had a huge part to play, for right or wrong. It's one of the issues with the current LVACWS. (I was in the media thingy at Portsmouth and the general consensus was not good on the influence of TV) They sail to schedules, not best breeze. TV has its own agendas, and those are not necessarily in the best interests of sailing.

 

As for ETNZ/Oracle.... as far as I understand it on the layday/days popular legend says that Oracle flew up 3 kiwi engineers to look at issues with foils.

 

From my PoV ETNZ developed foiling, as has been mentioned, as a silver bullet through the rules. I think their boat was probably at around 100% of it's design curve at the finals. As good as it was going to get.

 

Oracle were later on the curve, but having seen the kiwis foil downhill they worked on trying it uphill too (needing a matched combination of wing and foil development). They just hadn't got it right early on.

 

Yes, it is well known that foils have got a max speed of something around 50 knots(ish) and better technology is required to get round the cavitation issues. But at the time Oracle knew that if they could foil uphill in any way shape or form, they'd walk it.

 

They just got it wrong early on.

 

They got lucky with delays, however caused. The kiwis got unlucky for the same reasons. They nearly won as Oracle struggled, but the gods conspired against them.

 

Once Oracle got foiling uphill you could see instantly it was game over and I had no doubt the moment I saw them lift I knew the kiwis had no chance. Such is the nature of foiling. The difference between foiling speed and hull speed is so marked. (long discussion last week with a top foiling cat sailor/sail maker on foiling confirmed a lot of what I saw)

 

Although the result looked close I believe it was far from it. If Oracle had got things sorted earlier they would have walked it, the same way the kiwis hoped that they would. The kiwis probably knew what was coming (they all spy so they know) and hoped to make hay whilst the sun shone.

 

You can blame who you like amongst the sailors, but I believe the Cup was won/lost by the designers last time round.

 

I suspect that the next cup will be similar. Someone will get it right and walk it. From conversations with current crew that is what they are all worried about.

 

Yes, the IACCs were not as spectacular, but the design was refined and there were few opportunities for a massive speed difference. The Cup with the IACCs in Valencia probably WAS as good a racing as we have ever seen as the boats were so equal. Currently with foiling there are still huge opportunties for big speed increases. And as we all know, quickest boat usually wins.

 

Ref the 83 cup above the comments I have heard from people there (as far as my memory serves) was that A2 had two slight advantages, one in manouverability due to the shortened length of the keel, and slightly better speed on reaching. Neither were great enough to win it by themselves. The biggest differentiator was the US (and everyone else) THOUGHT A2 was faster. Mentality makes a big difference at that level. It gave the Aussies a swagger and the US thinking it was unfair. That left them chasing ghosts.

 

(from more than one source on Victory 82/83 team)

 

Rgds

Reetp

 

(all in IMHO... what do I know ?!)

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+1

 

Agree with the reasoning above. It is also the reason for so much one design being forced on all the competitors, Oracle know that their win was very close. A bit more breeze to enable an extra race to be finished and they would have been the loser with what should have been the fastest boat.

 

By bringing in the one design it narrows down the spending areas making it much harder for anyone to come up with the silver bullet out in left field. Fair crack to them as well, they have a bunch of poodle teams that are happy to go along with anything as long as they continue to get paid, so they get to make any rule they want. And before you all jump on the 'it saves money' bandwagon, do you really think that running the joke of a world series helps save money. Just can that bullshit and have an open design, save money and the concept behind the cup at the same time.

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As an aside to the comments from Reept, there was a lot of garbage talked about the first Oracle boat. Sorry, but it was never a foiler and was modified to try and catch up, no matter what the fan boys say. Oracle, like all the others had no idea what was coming. With all the pretending that of course boat 1 was going to be a foiler bullshit everyone seems to forget that the advances Oracle made in the time frame from first seeing the Kiwi tractor fly and race day was pretty fucking amazing. Their whole design team had to throw out all their theories and plans and start again. Well done to them, the fuckers.

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Damn! Lookie thar-another UptiP foil-funny I heard they were going out of "style" from a couple of real geniuses......

 

> no picture credit?!

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^ Childish repitition and a technically weak application of a meaningless phrase.

 

The foil case is capable of canting through 30° range in an ACC boat - there's no limit here.

 

The lifting surface in this photo is +/- parallel to the water surface - it's just another foil variation mate, get over it.

 

13710634_1780325705516241_56189060180170

opps... Photo © Eloi Stichelbaut / Groupama Team France

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Oh, bullshit! You're staring right at it and you can't recognize what you're looking at. There's a reason these guys are using uptip foils-because they require less power and attention to keep the boat flying fast. Remember, it was Groupama in the C Class at their first foiling LAC that proved the "uptip" point in direct comparison with Hydros. That lesson is still valuable today because all the AC boats have a power budget and they can't afford to ignore the proven value of these foils !

 

====================

And like so many other times you're dead wrong about 30 degrees on the cant axis:

 

i) The maximum rotation about the cant axis shall be 15 degrees with the rake axis
rotation set to appendage measurement condition; and
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@Gissie,

 

I'm pretty sure Oracle DID know what was coming.. the spy networks are large and sophisticated (and they are an IT company after all!!). I understand Oracle already have a permanent spy setup in the UK to watch BAR, and probably similar elsewhere too.

 

Knowing what is coming, and doing something to beat it are two different things.... I'm sure they did indeed crap themselves when they saw NZ foil first time.... like Alinghi did when they saw Oracles big wing (I remember well the looks on Alinghis faces in the presser after R1 at Valencia.... they knew the game was up) but Oracle probably had a lot longer to work on it than we may realise. Scrapping plans and starting afresh was a brave move, but ultimately the right one. Fortunately for them they had the cash and resources to do that.

 

They knew what they had to do to beat NZ. As Spithill said recently they are all working on measuring 'air time'.... the longer you spend up, the quicker you will be, even if you nearly sail backwards ! They knew that if they could foil just a little uphill.....

 

I agree, they did an amazing job, just. Feckers :-)

 

B. Rgds

Reetp

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I see yet another foil variation but no reason to apply any silly designation - (especially not yours, your own definition is not convincing, or even coherant).

 

What angle do you think that foil is to the surface in this photo - if it even matters?! (Note: it's the one in the water that counts! :o )

 

13710634_1780325705516241_56189060180170

 

There are no limits on cant for these boats - but you are right that the ACC boats are restricted to 15° (not the 30° I thought I remembered) - my bad, thanks for the correction.

 

Check the surrogate's case out here...

 

13692848_1780317892183689_75408271971017

 

That's a lot of 'slop'! :D

 

Not sparing the grinders gave OTUSA the win in AC34. There will be no mercy this time either, in the fitting of 'set-and-forget foils' - if there is a faster alternative!

 

But none of that will matter to TF with FC cranking on the helm like that!

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I see yet another foil variation but no reason to apply any silly designation - (and your own definition is not convincing, or even coherant).

 

What angle do you think that foil is to the surface - if it even matters?!

 

There are no limits on cant for these baots - but you are right that the ACC boats are restricted to 15° (not the 30° I thought I remembered) - my bad

 

Check the surrogate's case out here...

 

 

 

That's a lot of 'slop'! :D

 

First you say there are no limits, then you agree that the limit is 15 degrees??!! That is "coherent" thinking?!

Looks like they have reserved the majority of the "cant" range for moving the top of the foil inboard and bottom outboard thus lowering the tip dihedral.

--

The idea of ignoring the classic shape of an uptip foil to push some agenda you don't even understand is amazing. You simply don't understand what the foil is doing-I guess..... Canting inboard or outboard can change the level of leeway coupling-but not eliminate it. The uptip configuration has great value either way.......

By the way I seriously doubt that these foils are Team Frances "final" version- a lot more to come......

--

And once again: "uptip" is the inventors name for the foil. My definition exactly defines the key elements of the geometry of such a foil.

 

definition(to be applied using a picture of a deployed foil) : any foil that when it is deployed allows the more or less horizontal portion to be less than 90 degrees from a line normal(90 degrees) to the waters surface and/or when the more or less horizontal portion is less than 90 degrees from the more or less vertical portion of the foil as in the sketch:

NOTE: if an "L" foil is canted inboard(at the bottom) so that the bottom of the "L" has a dihedral angle it can have some of the positive attributes of an uptip foil.

stb hull coming at you:

post-30-0-92424400-1467666477_thumb.png

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The lifting surface in this photo is +/- parallel to the water surface

 

13710634_1780325705516241_56189060180170

opps... Photo © Eloi Stichelbaut / Groupama Team France

Not parallel, at a glance I vould say 10 to 15 %

 

The lifting surface in this photo is +/- parallel to the water surface

 

13710634_1780325705516241_56189060180170

opps... Photo © Eloi Stichelbaut / Groupama Team France

Not parallel, at a glance I vould say 10 to 15 %

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You purile little florida puss bag.

 

You are a sole voice using the word uptip in the whole community, but your arrogance and stupidity clouds your reasoning every time.

 

Even your hero Martin Fischer does not identify them as such. Plenty of valid coherent reasons have been given, explanations shared as to why - but your response in the face of overwhelming non-doug theories, is "rubbish" or "nonsense" etc....

 

Wow - well, that must settle it then in your favour then. :blink:

 

You have driven like a Road Train into a small little winding cul de sac with no hope of backing out with your dignity or reputation intact.

(Though it is doubtful that you have ever had either of these.)

 

You have never done anything but post other people's work and even then there have been plenty of occasions when you have failed to grasp their concepts - yet you blithely wander around professing your own superiority when it is clear that you have a very shallow understanding of anything really. Pathetic and truly Sad.

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You purile little florida puss bag.

 

You are a sole voice using the word uptip in the whole community, but your arrogance and stupidity clouds your reasoning every time.

 

Even your hero Martin Fischer does not identify them as such. Plenty of valid coherent reasons have been given, explanations shared as to why - but your response in the face of overwhelming non-doug theories, is "rubbish" or "nonsense" etc....

 

Wow - well, that must settle it then in your favour then. :blink:

 

You have driven like a Road Train into a small little winding cul de sac with no hope of backing out with your dignity or reputation intact.

(Though it is doubtful that you have ever had either of these.)

 

 

 

You have never done anything but post other people's work and even then there have been plenty of occasions when you have failed to grasp their concepts - yet you blithely wander around professing your own superiority when it is clear that you have a very shallow understanding of anything really. Pathetic and truly Sad.

Apparently he has the same " technique " and is held in similar " reverence " In the RC sailing world .

 

They've been dealing and mostly ignoring him for years which is why he spends so much time droning on in here .

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Thanks, TC... I wrote to them to ask why some of the pictures show dual, independent, wands on each hull. Interesting design.

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You purile little florida puss bag.

 

You are a sole voice using the word uptip in the whole community, but your arrogance and stupidity clouds your reasoning every time.

 

Even your hero Martin Fischer does not identify them as such. Plenty of valid coherent reasons have been given, explanations shared as to why - but your response in the face of overwhelming non-doug theories, is "rubbish" or "nonsense" etc....

 

Wow - well, that must settle it then in your favour then. :blink:

 

You have driven like a Road Train into a small little winding cul de sac with no hope of backing out with your dignity or reputation intact.

(Though it is doubtful that you have ever had either of these.)

 

 

 

You have never done anything but post other people's work and even then there have been plenty of occasions when you have failed to grasp their concepts - yet you blithely wander around professing your own superiority when it is clear that you have a very shallow understanding of anything really. Pathetic and truly Sad.

Apparently he has the same " technique " and is held in similar " reverence " In the RC sailing world .

 

They've been dealing and mostly ignoring him for years which is why he spends so much time droning on in here .

 

 

MM, you don't have a clue what you're talking about......(along with boing, boing)

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I don't remember where I found this but just had time to look again at it now. Written by Martin Fischer who is working with Team France, in April 2016. For those interested in Pitch Stability scroll down to a great illustration :

https://fr.calameo.com/read/0047502132ae545e148b0

The free-body diagram is an error-filled disaster. It also doesn't show what you think it does.

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Yeah, right.

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I see 2 wands per foil, I guess the higher one has priority to the other one in order to provide more AOA, thus a safer solution.

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Wrong thread? Trickle Down maybe? Possibly moving the whole foil and dgr or just the foil with no flap?

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You purile little florida puss bag.

 

You are a sole voice using the word uptip in the whole community, but your arrogance and stupidity clouds your reasoning every time.

 

Even your hero Martin Fischer does not identify them as such. Plenty of valid coherent reasons have been given, explanations shared as to why - but your response in the face of overwhelming non-doug theories, is "rubbish" or "nonsense" etc....

 

Wow - well, that must settle it then in your favour then. :blink:

 

You have driven like a Road Train into a small little winding cul de sac with no hope of backing out with your dignity or reputation intact.

(Though it is doubtful that you have ever had either of these.)

 

You have never done anything but post other people's work and even then there have been plenty of occasions when you have failed to grasp their concepts - yet you blithely wander around professing your own superiority when it is clear that you have a very shallow understanding of anything really. Pathetic and truly Sad.

 

Apparently he has the same " technique " and is held in similar " reverence " In the RC sailing world .

They've been dealing and mostly ignoring him for years which is why he spends so much time droning on in here .

MM, you don't have a clue what you're talking about......(along with boing, boing)

Actually I do , Greg V says hello and you haven't changed a bit :)

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No, you really don't! Greg V is(was?) a good guy but everything changes.

 

PS- it just struck me as very peculiar: you don't even use your own name but you toss Gregs name around on this forum??!!

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You purile little florida puss bag.

 

You are a sole voice using the word uptip in the whole community, but your arrogance and stupidity clouds your reasoning every time.

 

Even your hero Martin Fischer does not identify them as such. Plenty of valid coherent reasons have been given, explanations shared as to why - but your response in the face of overwhelming non-doug theories, is "rubbish" or "nonsense" etc....

 

Wow - well, that must settle it then in your favour then. :blink:

 

You have driven like a Road Train into a small little winding cul de sac with no hope of backing out with your dignity or reputation intact.

(Though it is doubtful that you have ever had either of these.)

 

You have never done anything but post other people's work and even then there have been plenty of occasions when you have failed to grasp their concepts - yet you blithely wander around professing your own superiority when it is clear that you have a very shallow understanding of anything really. Pathetic and truly Sad.

Apparently he has the same " technique " and is held in similar " reverence " In the RC sailing world .

They've been dealing and mostly ignoring him for years which is why he spends so much time droning on in here .

MM, you don't have a clue what you're talking about......(along with boing, boing)

Actually I do , Greg V says hello and you haven't changed a bit :)

 

 

MM, I discovered last night that you did this same exact thing several years ago-using exactly the same wording. Very strange.

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You purile little florida puss bag.

 

You are a sole voice using the word uptip in the whole community, but your arrogance and stupidity clouds your reasoning every time.

 

Even your hero Martin Fischer does not identify them as such. Plenty of valid coherent reasons have been given, explanations shared as to why - but your response in the face of overwhelming non-doug theories, is "rubbish" or "nonsense" etc....

 

Wow - well, that must settle it then in your favour then. :blink:

 

You have driven like a Road Train into a small little winding cul de sac with no hope of backing out with your dignity or reputation intact.

(Though it is doubtful that you have ever had either of these.)

 

You have never done anything but post other people's work and even then there have been plenty of occasions when you have failed to grasp their concepts - yet you blithely wander around professing your own superiority when it is clear that you have a very shallow understanding of anything really. Pathetic and truly Sad.

 

Apparently he has the same " technique " and is held in similar " reverence " In the RC sailing world .

They've been dealing and mostly ignoring him for years which is why he spends so much time droning on in here .

MM, you don't have a clue what you're talking about......(along with boing, boing)

Actually I do , Greg V says hello and you haven't changed a bit :)

MM, I discovered last night that you did this same exact thing several years ago-using exactly the same wording. Very strange.

Which can also be said for the majority of your posts .

 

I see Greg every summer . Sailing and boats in general are one of the topics discussed so of course how could your fine work over the years not come up for review ? :)

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Interesting video, foils seem to be straight, however at 1:11 it seems canted to the outside.

That would mean that Oracle succeeded to design foils flexing to the outside for more RM...

What do you think ?

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I think you are not making anything clearer.

 

There is no shot of that foil to say it's 'straight' (and I'm having to guess at what you probably mean by that anyway)

 

We know they have at least one board with a curve in the 'vertical' section that pushes the whole thing out towards max beam when deployed, expecially if they cant it out to max at the same time.

 

That is probably the board you are seeing. There is absolutely no reason to assume the two boards installed at that moment are the same.

 

You seem to have a bee in the bonnet about 'using flex to go places the rules would not otherwise allow' - sure there'll be a bit of flex in all boards and maybe more in the extra long lifting sections that we saw being trialed by LARBAR, but on what do you base your idea that there is 'more going on'??

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Interesting video, foils seem to be straight, however at 1:11 it seems canted to the outside.

That would mean that Oracle succeeded to design foils flexing to the outside for more RM...

What do you think ?

 

 

We've seen before that the bottom of the foil can be canted outboard. I don't think they are flexing outboard-I think they are hydraulically canted outboard. The force on the vertical section of the foil would be pushing hard inboard-not outboard. I think there is no doubt that the more or less horizontal part of the foil flexes but I don't think it causes outboard movement of the foil against the powerful lateral resistance of the vertical portion of the foil.

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