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On 2/1/2021 at 9:58 AM, MaxHugen said:

Mozzie, I did the following diagram quite a while ago to convince myself that the net vertical and horizontal forces were the same for "equivalent" T and Y foils - they are of course.  I'm not sure about the torque you mention, but from the bottom right diagram, the Y foil appears to have net horizontal force a bit further outboard than the T foil, no flap differential used though.

image.png.b855cf783a3a41d5f175040c0025d09f.png

And all this is correct in how the forces are drawn, but the conclusion that "the Y foil appears to have net horizontal force a bit further outboard than the T foil" is very misleading. That is not shown here. 

The vertical component is greater on the outboard wing. But that is a force component. 

I mean, otherwise just rotating the foil on your piece of paper changes the CoL. 

How can tilting the foil on your piece of paper change where the CoL is?

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Just a few interesting bits of the straight-line performances from today: Upwind /Downwind VMGs - race 1: Upwind /Downwind VMGs - race 2: Same story in both races actually.

Thanks to weta27's pics I have created an approximation of NZ's "BFB v2" foil. Main points: Foil area is almost the same, possibly even a smidge larger. Flaps have increased in area as

OK, it sounds like there's some interest in this topic, so here goes.   Any engineering effort starts by defining the requirements.  From this figure, it looks like the average foil area is 1.64

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Imagine roll stability in a plane. 
Anhedral is unstable, in that as the plane rolls the gravitational force start pulling the mass further over to the side inducing more roll. But is is not the CoL which is changing position relative to the wings and fuselage, but that the gravity is pulling in a different direction once the plane starts to roll (relative to aircraft). 

Now, people draw this as gravity staying a fixed direction and the plane rotation on the diagram. But it would show up the same if you fixed the rotation of the plane on the diagram and rotated gravity. The result is not dependent on what you label X and Y. You could fix the plane as your reference frame, or the direction of gravity and still come to the same conclusion. 

You should be able to orientate you X-Y reference frame in any direction you like and get the same result. 

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29 minutes ago, Mozzy Sails said:

How can tilting the foil on your piece of paper change where the CoL is?

I'm unsure of your question... are you referring to the Vertical force  (FZ)?

As there's obviously some interest in force CEs and Flap factors in Y foils, I've done a few calcs.  LR's foil has been used as the example, and the required Vertical Force (FZ) for balance of forces in the y plane is set at 70,000 Newtons (about 6.8 tonnes-force).

Diagram 1 shows an approximation of the Centroid of the foil, although strictly speaking this is probably not quite the CE - but it will have to do.

image.png.8bf822b5f3a34e217b1aa52ae73daf58.png

Diagram 2 shows the foil at 20° cant. LR data during the Challenger Finals indicated a range of 18-20° - notably less than TR during the ACWS (median = 22°).

Both flaps are at equal angle. The Resultant (Lift) Force (FR) is therefor equal for each wing, and is perpendicular to the foil cant angle.

The CE of both FZ (vertical force) and FY (lateral force) have also been calculated, and if we were to use the FR (or the foil/bulb intersection) as the "axis of rotation" for the calculation of moments, both FZ and FY should be included for somewhat greater precision.

image.thumb.png.f1dc71c26fb4c93e102f9cad67f16758.png

Coming to a forum near you, "in the fullness of time", ... maybe... will be an attempt to quantify the effects of using differential flaps to increase the CE-FZ offset. This will again be calculated on the basis of requiring a total FZ = 70,000 N.  :)

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10 minutes ago, Mozzy Sails said:

You should be able to orientate you X-Y reference frame in any direction you like and get the same result. 

I don't understand your point.  These are the commonly used x,y and z planes.  With gravity in the z (vertical) plane.

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6 minutes ago, MaxHugen said:

I don't understand your point.  These are the commonly used x,y and z planes.  With gravity in the z (vertical) plane.

So test your ideas and instead of setting gravity as your Z plane use the foil symmetry line. 

The foil doe not know which way gravity is pulling. CoL is not dependent on gravity. Yet the way you draw this it is. 

Only mass feels gravity. 

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18 minutes ago, Mozzy Sails said:

So test your ideas and instead of setting gravity as your Z plane use the foil symmetry line. 

The foil doe not know which way gravity is pulling. CoL is not dependent on gravity. Yet the way you draw this it is. 

Only mass feels gravity. 

??? And what is Vertical Force (FZ) doing?  Countering the effect of Mass x Gravity, no?

The cant of the foil results in a Resultant force perpendicular to the cant, nothing to do with gravity. This force can then be vectored into Vertical force - as in opposite to gravity - and lateral force, perpendicular to vertical force.

Somehow, we're not on the same page... :unsure:

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10 minutes ago, MaxHugen said:

??? And what is Vertical Force (FZ) doing?  Countering the effect of Mass x Gravity, no?

The cant of the foil results in a Resultant force perpendicular to the cant, nothing to do with gravity. This force can then be vectored into Vertical force - as in opposite to gravity - and lateral force, perpendicular to vertical force.

Somehow, we're not on the same page... :unsure:

I don't think we are in the same book with Mozzy.

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5 minutes ago, MaxHugen said:

??? And what is Vertical Force (FZ) doing?  Countering the effect of Mass x Gravity, no?

The cant of the foil results in a Resultant force perpendicular to the cant, nothing to do with gravity. This force can then be vectored into Vertical force - as in opposite to gravity - and lateral force, perpendicular to vertical force.

Somehow, we're not on the same page... :unsure:

Yes, it's countering gravity. But you don't have gravity shown in your diagram above. 

So, I challenge you again, change your frame of refence and show the same result. 

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6 minutes ago, Mozzy Sails said:

Yes, it's countering gravity. But you don't have gravity shown in your diagram above. 

So, I challenge you again, change your frame of refence and show the same result. 

I guessed that everyone would obviously assume gravity was down... why would you want to use a diagram with gravity in a different direction?

Perhaps you should have a chat with your mates, show them my diagram, and see if they feel it's right, wrong, flawed, or whatever.

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1 hour ago, Mozzy Sails said:

I mean, otherwise just rotating the foil on your piece of paper changes the CoL. 

Imagine a 90deg Y.

When the outboard section is horizontal there is 0 vertical component from the inboard because it is vertical.

So yes the CoL moves depending on the cant angle.

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Just now, hoom said:

Imagine a 90deg Y.

When the outboard section is horizontal there is 0 vertical component from the inboard which is vertical.

So yes the CoL moves depending on the cant angle.

Not relative to the foil. 

The foil does not know X and Y. 

It's insane that the CoL of a foil changes depending on how you orientate in you your reference frame. The relationship between CoG and CoL changes, but that is because gravity is from a different direction relative to the CoG and CoL. 

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14 minutes ago, hoom said:

Imagine a 90deg Y.

When the outboard section is horizontal there is 0 vertical component from the inboard because it is vertical.

So yes the CoL moves depending on the cant angle.

Perhaps this is all a matter of terminology. Technical stuff I've read re sails, foils etc, tends to use Resultant Force (is that CoL to others?) to avoid misinterpretation, and then express force vectors in logical "planes" - x, y and z.

The Resultant force (FR) is perpendicular to the foil plane, if flap angles are equivalent. However, the Vertical and Lateral forces have CEs that vary dependent on the foil cant angle. The CE of FR also changes position.

If everyone used FR, FX, FY and FZ, to explain their thoughts, this might not be so confusing.

And I thought my diagram would clearly show what I was calculating!  Silly me. :D

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3 hours ago, Hemi said:

Does anyone know what the extension jutting out from the trailing edge on ETNZ foil is for? Been meaning to ask for ages..

Mozzy and co think that ETNZ have moved some weight from the foil to the spat (extension on the trailing edge of the foil arm),  which has been done to allow them to run smaller foils.         

It may serve a second purpose tidying up the spray flowing off the foil arm.  

  

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2 minutes ago, MaxHugen said:

The Resultant force (FR) is perpendicular to the foil plane, if flap angles are equivalent. However, the Vertical and Lateral forces have CEs that vary dependent on the foil cant angle. The CE of FR also changes position.

They are not vertical and lateral forces though, they are just vectors you have drawn. 

Draw your anhedral foil at some extreme angles and show me where the CoL is. If you must, keep gravity in Z, makes no difference to me. 

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25 minutes ago, MaxHugen said:

Perhaps you should have a chat with your mates, show them my diagram, and see if they feel it's right, wrong, flawed, or whatever.

"Ce-fy and ce-Fz are totally irrelevant points"

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1 minute ago, Mozzy Sails said:

"Ce-fy and ce-Fz are totally irrelevant points"

Well, there goes Euclidian geometry then.

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2 minutes ago, The Advocate said:

This was my bible. Is really old but still really relevant. Even covers lift foils, all the way back then.

Sailing Theory and Practice  by C A Marchaj

Ditto!  Bought my copy ~4 decades ago.

I'm p*ssed off that I lent it to someone who never returned it. :angry:

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I like to follow this topic, you are amazing guys! But I think advantages and disadvantages of the two different solutions can't be obvious. Or you greatly underestimate one design team or the other, and all the simulations that surely they made. The choice has been a compromise towards what was seen as more important, and also a guess, of course.

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8 minutes ago, MaxHugen said:

Ditto!  Bought my copy ~4 decades ago.

I'm p*ssed off that I lent it to someone who never returned it. :angry:

Fuck me, the same!

I have located a replacement though through looking for a link for my and rebought it!

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12 minutes ago, MaxHugen said:

Well, there goes Euclidian geometry then.

well explain to me. Does the boat heel around Ce-fy or ce-Fz?

You seem to be proposing that Ce-Fz is the fulcrum? Why that and not Ce-fy?

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9 minutes ago, Mozzy Sails said:

well explain to me. Does the boat heel around Ce-fy or ce-Fz?

You seem to be proposing that Ce-Fz is the fulcrum? Why that and not Ce-fy?

Ce-Fz because that is the focal (result of all the forces) point of the forces in a sailing condition. Ce-Fy is the point with the foil arm oriented so the foils are parallel to the water line, as if towing.

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3 minutes ago, Mozzy Sails said:

well explain to me. Does the boat heel around Ce-fy or ce-Fz?

You seem to be proposing that Ce-Fz is the fulcrum? Why that and not Ce-fy?

The fulcrum can be anywhere you like on the boat for calculating moments, including the windward foil or even the mast top. The boat heels, but you can choose any reference point you like, so long as you correctly calc the relevant moments.

But no, I haven't suggested anywhere that the fulcrum should be either of the vector force CEs. These "totally irrelevant points" were simply included in the diagram to demonstrate that neither of them coincide with the Resultant force CE. Thought someone might find it interesting to see where they actually are, re LR's Y foil.

For my calcs I just use the foil/arm junction of a T foil as the axis of rotation,  so FZ and FY are disregarded,  to avoid even more complicated equations.

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 I was hesitant to bore everyone with another diagram to illustrate differential flaps and the resultant forces and the Vertical and Lateral vector force CE locations - but what the hell, here goes.

This examines a scenario where the leeward wing flap has an increased angle, to generate more Vertical force (FZ), and the windward wing flap angle is decreased, such that the total FZ is still 70,000 N, as in the previous diagram. An arbitrary increase of 20% FZ increase on the leeward wing was chosen.

Note that Lateral force (FY) has decreased by 16.3%, and CE-FZ has moved outboard by ~200mm. CE-FY has not changed by much. The previous force vectors and CEs, where flap angles were equal, are shown in grey for comparison.

So does this have anything to do with RM?  Yes it does. Using either the foil/arm intersection, or FR as the "axis" for calcs, it can be seen that both FZ and FY exert opposing "turning" forces. The greater force FZ and it's greater perpendicular distance to the chosen fulcrum exceeds that of FY, so there is a net additional righting moment which can be used for more sail power.

Whether it's worthwhile needs to be considered against some loss of total Lateral force (FY), and possibly a difference in drag compared to setting both foils at equal angles (could be positive or negative, haven't done calcs on that).

Leeway has also not been addressed. This has more effect on the windward wing due to it's greater angle to the horizontal. But the rabbit wants me out of it's hole, so enough.

image.thumb.png.46ca4ea7bd1e1b9bcfb99954dac10672.png

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I like the gravity arrow!

The thing is, you can't end up with less horizontal force component. In reality, the leeway will increase until the Fy is the same as it was before. Both will see more span wise flow, but the inboard wing will see it as more of an increase in AoA. Spanwise flow will feel, the water like a longer chord and shorter span. 
 

But, now you are running perhaps more flap than is ideal on the outboard wing and a greater AoA than is ideal on the inboard wing. The section have to be symmetrical, so it's not like you can change their shapes for these separate roles. 

My conclusion is this won't be optimum for VMG. But it would be a much quicker way of switching between high mode to low mode than using cant. 
 

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3 hours ago, Mozzy Sails said:

Yes, it's countering gravity. But you don't have gravity shown in your diagram above.

 

3 hours ago, MaxHugen said:

I guessed that everyone would obviously assume gravity was down... why would you want to use a diagram with gravity in a different direction?

I'm guessing the problem we have here is that, with the two of you on different sides of the world, gravity is in the opposite direction for each of you. :blink:

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51 minutes ago, MaxHugen said:

 I was hesitant to bore everyone with another diagram to illustrate differential flaps and the resultant forces and the Vertical and Lateral vector force CE locations - but what the hell, here goes.

This examines a scenario where the leeward wing flap has an increased angle, to generate more Vertical force (FZ), and the windward wing flap angle is decreased, such that the total FZ is still 70,000 N, as in the previous diagram. An arbitrary increase of 20% FZ increase on the leeward wing was chosen.

Note that Lateral force (FY) has decreased by 16.3%, and CE-FZ has moved outboard by ~200mm. CE-FY has not changed by much. The previous force vectors and CEs, where flap angles were equal, are shown in grey for comparison.

So does this have anything to do with RM?  Yes it does. Using either the foil/arm intersection, or FR as the "axis" for calcs, it can be seen that both FZ and FY exert opposing "turning" forces. The greater force FZ and it's greater perpendicular distance to the chosen fulcrum exceeds that of FY, so there is a net additional righting moment which can be used for more sail power.

Whether it's worthwhile needs to be considered against some loss of total Lateral force (FY), and possibly a difference in drag compared to setting both foils at equal angles (could be positive or negative, haven't done calcs on that).

Leeway has also not been addressed. This has more effect on the windward wing due to it's greater angle to the horizontal. But the rabbit wants me out of it's hole, so enough.

image.thumb.png.46ca4ea7bd1e1b9bcfb99954dac10672.png

Ah, this is what my question was about earlier, though I probably asked it awkwardly. Thanks you, exactly what I thought.

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2 hours ago, MaxHugen said:

The fulcrum can be anywhere you like on the boat for calculating moments, including the windward foil or even the mast top. The boat heels, but you can choose any reference point you like, so long as you correctly calc the relevant moments.

But no, I haven't suggested anywhere that the fulcrum should be either of the vector force CEs. These "totally irrelevant points" were simply included in the diagram to demonstrate that neither of them coincide with the Resultant force CE. Thought someone might find it interesting to see where they actually are, re LR's Y foil.

For my calcs I just use the foil/arm junction of a T foil as the axis of rotation,  so FZ and FY are disregarded,  to avoid even more complicated equations.

To clarify my earlier comment in answering this because I was bbqing, it took it that Mozzy was referring to the rotation point of the fulcrum, so to speak. Trying to accommodate as much varied language as I can.

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4 minutes ago, Mozzy Sails said:

I like the gravity arrow!

The thing is, you can't end up with less horizontal force component. In reality, the leeway will increase until the Fy is the same as it was before. Both will see more span wise flow, but the inboard wing will see it as more of an increase in AoA. Spanwise flow will feel, the water like a longer chord and shorter span. 
 

But, now you are running perhaps more flap than is ideal on the outboard wing and a greater AoA than is ideal on the inboard wing. The section have to be symmetrical, so it's not like you can change their shapes for these separate roles. 

My conclusion is this won't be optimum for VMG. But it would be a much quicker way of switching between high mode to low mode than using cant. 
 

Hahaha... thought I better add that arrow. :)

Agree with your thoughts about leeway, as eventually it has to balance in the Y plane forces, as well as moments. It is just so very complicated! Doing a drag calc might be interesting, to see how differential flaps stack up against equal angles? My guess agrees with your conclusion... I can't see it really helping VMG.

As for cant, when I check through all the data that @dorox has kindly made available for us, I just don't see much change in cant at all with either LR or NZ, excluding maneuvers etc, and of course upwind vs downwind.

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Anyone has an idea of what kind of hardware/operating system/programming language do the teams use for electronic systems on board? 

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ETNZ cant out to max upwind, then keep everything in line with sail trim. 

LR play with flap differential a little. I think this was their issue with that roll frequency the Italian guy did an analysis of. 

Gust hits and you don't want to spill wind, so what can you do with foils? More outboard flap to shift CoL outboard and give a little more RM? Sounds good. But then you have to decrease inboard flap to maintain ride height, which means more leeway. So you start to accelerate 'slip' sideways. The side slip will reduce force on the sail momentarily until the horizontal component equalises again and you hit your new steady state leeway angle and then you'll have to sheet on to match this new leeway with the same AoA on the sail with the increased yaw. I can imagine quite a bit of resonance in that feedback loop.

There will be an optimum sheeting angle for each leeway setting, so you'll need to get back to that which will mean flattening main and lowering CoE to get get trim back where it needs to be.

It's like sailing my skiff. When I see a gust, we need to talk crew (mainsheet) what I plan to do with the helm. If I plan to pinch a little, he needs to know to no overdo the main ease. Or of I plan to foot and take acceleration he needs to double his ease.  But after this we need to decide what w do to get the boom back where it should be... more kicker, more Cunningham (or board up?).

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9 minutes ago, Mozzy Sails said:

Gust hits and you don't want to spill wind, so what can you do with foils? More outboard flap to shift CoL outboard and give a little more RM? Sounds good. But then you have to decrease inboard flap to maintain ride height, which means more leeway. So you start to accelerate 'slip' sideways. The side slip will reduce force on the sail momentarily until the horizontal component equalises again and you hit your new steady state leeway angle and then you'll have to sheet on to match this new leeway with the same AoA on the sail with the increased yaw.

If leeway increases, then AoA presumably also increases? Doesn't this amplify the effect of a gust?

Why not have the mainsail trimmer increase twist to reduce the heeling effect of the gust, or let out the traveller a bit?

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Yeah, AoA would increase. But it's not instant. You'd basically have an acceleration to leeward until those forces resolved at the new increased leeway. 

If anything it would work to mitigate the gust, take the edge off. And as leeway increase AoA on your sails would decrease (which would feel like a lull) and need to be responded by sheeting in. So it all works. But difficult to do in a feedback loop between two crew members. 

Just like having someone lift up a dagger board in a dinghy. Leeway increase and you need to sheet on. Have you ever had a dagger board snap? I have. Instant and rapid acceleration in leeway = capsize to windward. 

But all needs to be co-ordinated about who is going to do what when that gust hits. Normally it's just helm and and main hand. Now it's helm, main hand and flight controller.

 "Why not have the mainsail trimmer increase twist to reduce the heeling effect of the gust, or let out the traveller a bit?"

No reason not to... worked fine for decades. But increasing righting moment on gust hitting isn't a new idea either. I.e hiking out a bit harder. What weird is the leeway RM coupling. 

Even dinghies with gybing centreboards (5o5) I don't think can play them dynamically. 

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22 minutes ago, The Advocate said:

Is the current thinking that the windward flap is angled downward?

I think the current thinking is... dunno!  :D

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2 hours ago, The Advocate said:

Is the current thinking that the windward flap is angled downward?

To my understanding, today this depends on which way your gravity vector points? 
 

It’s getting ‘heavy’ around here :) 

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OK, here is my take on the anhedral foil righting moment debate:

First, we have to clarify whether we're talking about steady-state balance or some dynamic situation. For simplicity, I'll talk about the steady state balance for now.

For this comparison, let's assume that we have two boats that are equally balanced, sailing with the same speed, TWA with the same sail plan. The only difference is that one has a T-foil, the other an anhedral. If we start from here, it's important to realize that the total vertical and total horizontal foil forces have to be the same for both boats. From here, it follows that you can't freely change the force distribution between the wing halves. That distribution will depend on the foil arm cant angle.

It turned out to be quite an interesting geometrical problem. I used Max's measurements for anhedral angle and coordinates of center of effort for the wing halves, and used my VPP for vertical and horizontal foil forces required. The effect of sticking out the outside tip of the foil was omitted.

Here is what happens at TWS=20kts upwind - need for max righting moment (double click to see it better):

1574351370_uw20.thumb.png.02533bfcd9a0d3e6b155c964247a7c5d.png

There's a lot to digest here, I've been staring at these for half an hour now:))) Horizontal axis is foil arm cant angle - as we go right, the foil is canted out more and more. Changes in all the forces and arm lengthes were included in these calculations.

For a given sail setup, the T foil can only have one specific cant angle to balance forces. This is indicated by the dotted vertical line. The horizontal dashed line shows total forces and righting moment generated by the T foil. For the horizontal and vertical forces, this is the same as the sum of forces on the anhedral wing halves. Red and green lines represent the inside and outside wing halves of the anhedral foil. RM is referenced to the foil arm rotation axis on the hull for simplicity. We're only interested in the differences anyway.

On the left graph, what you see is that with low cant angle, the outside half contributes minimally to horizontal forces, and the inside half has to carry almost all the force. As you cant the foil out, this balance changes with a cross-over around 64 deg cant angle. 

The second graph shows vertical force, and it's quite confusing at first. It shows the same thing that at low cant angle, the outside half contributes minimally, and almost all the vertical lift is carried by the inside. You might think this is wrong (I did first), since the angles should work the opposite way compared to horizontal forces, the outside half is much closer to horizontal - shouldn't it generate the vertical lift? The way it works out is that at those low cant angles, the total lift generated by the outside wing half is minimal.

This can be seen on the third graph. Basically, you can think of it as you need a certain wing angle to counteract the sail forces. At low arm cant angle, the outside wing's angle is just really not aligned well with these forces, so it can't carry much. The two halves become equally loaded at around 62 deg foil cant, which is well below the cant angle that a T foil would use. The load on each wing half is a tiny bit higher than the wing half of the T foil, because of the anhedral angle.

Finally, righting moment is shown on the right side. The blue line indicates the combined righting moment of the two wing halves. As you can see, righting moment of the T foil (dashed line) is reached at a much lower cant angle with the anhedral, and you can generate much more RM with the anhedral foil if you further increase cant angle. If you are limited by how much of the outside tip can stick out of the water, the anhedral foil generates a lot more righting moment.

So what's the downside? Unless you are at the cant angle when the loads on the wing halves are equal (where the lines cross on the third graph), one of your wing halves will carry more lift than the other, so basically you waste some wing area on the other wing half. Plus, if the flap is deflected from its optimum angle, drag will increase further. However, you can see that LR's foil is designed pretty well. The wing halves are loaded equally almost at the same cant angle, when the RM reaches the necessary amount (horizontal dahsed line), around 62 - 63 deg cant.

For contrast, here is what happens at TWS=10kts downwind, when you need less RM:

1021911571_dw10.thumb.png.484d6f28d2264c2c67323ab0fae61b14.png

Note that the cant angle is around 63 deg when the total righting moment is at the required value (dashed line). If you look at the lift on the wing halves, you'll see that the inside half is carrying lot more than the outside at this cant angle, so the foil is not balanced out as nicely as upwind. It's also interesting to see how the cant angle barely changes for the anhedral, whereas the T-foil's cant angle went from 67.5 deg (20kts upwind) to ~58 deg (10kts downwind). This explains why in my previous post, cant angles for ETNZ and AM were the highest upwind, and the lowest downwind.

To sum up, the anhedral foil certainly offers more flexibility, but it's top speed performance may be hindered in some conditions. 

Finally some of my previous histograms of cant angles supporting the above analysis. This is from the first ACWS race, in about 15-16kts of wind, upwind and downwind cant angles:

510053014_uwfcant.png.1ac3da66281e263a98fd5a7393d194d3.png  796790026_dwfcant.png.8d07be5c2f64704ed52fd487c53373ed.png

Note how narrow the histograms are for ETNZ, they have to set the cant at a certain angle for balance, whereas LR can play with it depending on how they want to distribute loads between the wing halves. You can also see, how ETNZ's cant angle is much higher upwind, and much lower downwind than LR's.

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14 hours ago, The_Alchemist said:

Very nice work.  It does get you wondering about how AM would have done without crashing...  So far LR has shown the best boat handling and that has gone a long way.

 

14 hours ago, Barnyb said:

Thanks Erdb.

This supports my observations that  GBR were the slow boat (but sailed well in the RR's). I think overall their campaign lacked the finesse you would expect from a winning campaign. Really not much better than Bermuda!

Also it doesn't really paint LR in a good light. LR is not really performing well in any category. Even without performance figures the history and sheer capability of ETNZ would be a daunting target. These figures make it just that much harder. The constant view that LR is setup for light air races I do not think will be shown to be correct. When they line up against ETNZ in the light I still see an advantage (and a reasonable one) for ETNZ.

As for AM - what may have been if they didn't have their off! They could have given LR a good test in the semi's with some more time for crew work and development rather than fixing the hole.

 

 

 

 

13 hours ago, jaysper said:

I think you're unfair to INEOS. They aren't great, but a lot better than Bermuda and not that far behind LR.

I agree that the whole myth about LR being shit hot in light airs will only be HALF right, in that they will be shit but not hot.

To think ETNZ will not be prepared for light airs is absurd. LR are going to receive a king sized reaming.

My take on it is that LR designed a very sweet boat, highly versatile, easy to sail with good overall performance. ETNZ and AM created monsters that are very fast, but difficult to handle. AM already demonstrated they couldn't tame it, ETNZ still has to show they can when racing in anger. However, ETNZ's monster is much further developed than AM's, so that might help. INEOS was off, but they did sail the shit out of that boat in shifty, puffy conditions in the RRs.

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On 3/1/2021 at 11:26 PM, dorox said:

I've done something pretty cool: synchronised video feeds with boat data and GPS tracks. Should keep you guys busy while the racing keeps getting delayed.

P.S. if VirutalEYE people are reading this: Lets see how long it takes for you to copy that, too!

https://ac36.herokuapp.com/map

image.png.ae221c1a91338f79ea478f88c6af1ef3.png

@dorox this is simply amazing. Thank you !! I re-watched races usually with the on board comms audio and the Virtual on video, but this is simply incredible.

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11 hours ago, Mozzy Sails said:

You can't just draw balance the vertical component though. Truth is the foils have no idea which direction is X and Y. Add in the X component and then balance.  

The way you have drawn it the CoL would constantly change depending on how you orientated the foil is canted by the teamon your page!

I mean, draw a foil with a right angle? What could possibly be the conclusion there? 

 

fixed it for you

a foil with a right angle ... ok

image.png.a68cbc8bd6ff1228e35a14e0b659b7f1.png

and yes it has changed my thinking thank you ... I think we are both right but wrong so can agree to merge results :P

someone with the time to SohCahToa can tell me if the yellow line is on the foil mirror line for various angles ... i.e, can LR move the pivot center outside the mirror line

image.png.17a6283c0653b1452bd3ff933e417ece.png

 

 

image.png

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27 minutes ago, erdb said:

OK, here is my take on the anhedral foil righting moment debate:

I forget, the foil cant angle (example 62) is the angle from... which plane? 

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1 hour ago, Stingray~ said:

I forget, the foil cant angle (example 62) is the angle from... which plane? 

FCS reports the angle between vertical and a line drawn from the rotation axis to the end of the foil arm. It's not quite clear whether they use the end of the one-design piece or some other point, so the actual numbers may differ by 1-2 degrees.

cant.JPG.56bcd16c2d336658d43f033a88534605.JPG

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1 hour ago, Lickindip said:

fixed it for you

a foil with a right angle ... ok

image.png.a68cbc8bd6ff1228e35a14e0b659b7f1.png

and yes it has changed my thinking thank you ... I think we are both right but wrong so can agree to merge results :P

someone with the time to SohCahToa can tell me if the yellow line is on the foil mirror line for various angles ... i.e, can LR move the pivot center outside the mirror line

image.png.17a6283c0653b1452bd3ff933e417ece.png

 

 

image.png

These questions, isolated from the state of the boat, cannot be answered. As you change cant angle, the forces on the wing halves change depending on what forces the foil has to counteract. You are only looking at it in 2D, but both the pitch and yaw angles can change as well, and suddenly the distribution of forces between the wing halves are different.

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8 hours ago, strider470 said:

Anyone has an idea of what kind of hardware/operating system/programming language do the teams use for electronic systems on board? 

It will be a variety, apparently in Bermuda ETNZ used a PLC to bodge a variable flow hydraulic valve with PWM and a solenoid, which required a windows embedded device, and that became the basis of the FCS so may still be used, the INEOS people had some consultants come in and build e-ink displays that I think use a custom Android port? And I certainly wouldn't be surprised to see Android or other Linux based software for the various displays around the place. The hardware side doesn't tend to have what you would think of as an operating system, the microprocessors will run specialised kernels, some plc's may run linux, some embedded windows, probably a lot of C or Rust around.

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12 hours ago, Mozzy Sails said:

And all this is correct in how the forces are drawn, but the conclusion that "the Y foil appears to have net horizontal force a bit further outboard than the T foil" is very misleading. That is not shown here. 

The vertical component is greater on the outboard wing. But that is a force component. 

I mean, otherwise just rotating the foil on your piece of paper changes the CoL. 

How can tilting the foil on your piece of paper change where the CoL is?

Drawings are ok. Two Things are clear: 

1- T-foil shows a smaller FR (5%) so induced drag is LESS. This is true all the time due to individual R forces on the same direction.

2- Y-foil puts the CoL a bit more outward so potentially more RM (marginal). This coud be more usefull when needing to depower. More induced drag as individual R forces not in the same direction. 

Less drag is better for VMG

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8 hours ago, MaxHugen said:

I think the current thinking is... dunno!  :D

LOL, yep! I have these thoughts bouncing around the noggin that play out some ideas where the flap angle could be completely different to what seems obvious.

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44 minutes ago, luisbordino said:

Less drag is better for VMG

Only if you’ve got all the lift you want.  More generally higher lift:drag ratio is what is needed for better for VMG.

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6 hours ago, Stingray~ said:

To my understanding, today this depends on which way your gravity vector points? 
 

It’s getting ‘heavy’ around here :) 

Good discussion though.

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55 minutes ago, JonRowe said:

It will be a variety, apparently in Bermuda ETNZ used a PLC to bodge a variable flow hydraulic valve with PWM and a solenoid, which required a windows embedded device, and that became the basis of the FCS so may still be used, the INEOS people had some consultants come in and build e-ink displays that I think use a custom Android port? And I certainly wouldn't be surprised to see Android or other Linux based software for the various displays around the place. The hardware side doesn't tend to have what you would think of as an operating system, the microprocessors will run specialised kernels, some plc's may run linux, some embedded windows, probably a lot of C or Rust around.

Good answer, thanks.

Chris (formerly of ETNZ) posted detailed info here a while back about Bermuda and the likely FCS software this time too, I forget his exact screen name. 

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20 hours ago, The Advocate said:

Copy that. I imaging that surface ventilation as @jaysper mention would screw with it though. I was thinking the other way in the the anhedral foil would have more area at a higher water pressure. I could very well be pissing into the wind though.

I reckon the outboard wing is fully ventilated when the tip is out. It's easily visible from the overhead shots. Could be why etnz has pitting all around the hinges on the outboard wing. Funny how the pitting on the inboard wing is most visible on the leading edge...can't find the shot right now but was notable.

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2 minutes ago, barfy said:

I reckon the outboard wing is fully ventilated when the tip is out. It's easily visible from the overhead shots. Could be why etnz has pitting all around the hinges on the outboard wing. Funny how the pitting on the inboard wing is most visible on the leading edge...can't find the shot right now but was notable.

Pitting from cavitation?

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6 minutes ago, barfy said:

I reckon the outboard wing is fully ventilated when the tip is out. It's easily visible from the overhead shots. Could be why etnz has pitting all around the hinges on the outboard wing. Funny how the pitting on the inboard wing is most visible on the leading edge...can't find the shot right now but was notable.

I don't think it would be fully ventilated, since that would mean the inboard one would be at least partially ventilated.

Given the board is straight, the ventilation would be largely gone by the time you get to the bulb I would have thought.

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5 minutes ago, jaysper said:

I don't think it would be fully ventilated, since that would mean the inboard one would be at least partially ventilated.

Given the board is straight, the ventilation would be largely gone by the time you get to the bulb I would have thought.

If Luna Rossa is going to win.. you will need ventilation ;)

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5 minutes ago, strider470 said:

If Luna Rossa is going to win.. you will need ventilation ;)

Yup! I think plenty of Etnz supporters would need to be put on oxygen! LOL! :lol:

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1 minute ago, jaysper said:

Yup! I think plenty of Etnz supporters would need to be put on oxygen! LOL! :lol:

Now I understand Bertelli saying he will bring some breath of fresh air to the America's Cup :D

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14 hours ago, Mozzy Sails said:

Yes, but those aren't the lift. Those are not the resultant forces. If they were, yes, but they're not.  Those are Y components of the lift. 

I mean, rotate the foil on the piece of paper and the CoL would change relative to the foil. Despite all geometry saying the same. 

The foil does not know what you are defined the X-Y refence frame as. 

But the defined Y axis is the L we care about for CoL.  There will be a similar vector at 90 degrees that will give the center of horizontal forces countering lee way.   If you combine the two vectors then they will be on the center line of the foil and in the direction of the foil arm.  But if you want just the component that is vertical, it's vector is off center further outboard.

Remember also that the Y axis is not arbitrary, as it is aligned to the direction that gravity points!  So the foil doesn't know which direction Y axis is, but the whole body as a combination of forces certainly does.

 

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7 minutes ago, strider470 said:

Now I understand Bertelli saying he will bring some breath of fresh air to the America's Cup :D

On a more serious note, has LR announced their CoR if they win?

I can't imagine it would be ETNZ.

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1 hour ago, erdb said:

FCS reports the angle between vertical and a line drawn from the rotation axis to the end of the foil arm. It's not quite clear whether they use the end of the one-design piece or some other point, so the actual numbers may differ by 1-2 degrees.

cant.JPG.56bcd16c2d336658d43f033a88534605.JPG

I’ve been slow to appreciate this definition of cant angle, but that means the two foils above have different cant angles, because the end of the arm is lower on the T foil.  That means doing a like-for-like comparison of LR and TR needs an offset applying.

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56 minutes ago, sosoomii said:

Only if you’ve got all the lift you want.  More generally higher lift:drag ratio is what is needed for better for VMG.

Well the assumption in theydrawings IS both foils generating the same vertical net force  and same horizontal net force

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22 minutes ago, The Advocate said:

Pitting from cavitation?

I would think so..showed as white in the shot. I'll keep looking for it,I think it was a zoom of a weta shot about a week ago. The hinge area makes sense as low pressure in the cavity, the leading edge wasn't mentioned and doesn't make sense to me.

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10 hours ago, MaxHugen said:

Hahaha... thought I better add that arrow. :)

Agree with your thoughts about leeway, as eventually it has to balance in the Y plane forces, as well as moments. It is just so very complicated! Doing a drag calc might be interesting, to see how differential flaps stack up against equal angles? My guess agrees with your conclusion... I can't see it really helping VMG.

As for cant, when I check through all the data that @dorox has kindly made available for us, I just don't see much change in cant at all with either LR or NZ, excluding maneuvers etc, and of course upwind vs downwind.

Surely it will help downwind VMG, where you don't want to counter leeway. Being able to favour generating lift on the more horizontal side should allow a more neutral setting on the side that would otherwise push the boat upwind

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12 minutes ago, sfigone said:

But the defined Y axis is the L we care about for CoL.  There will be a similar vector at 90 degrees that will give the center of horizontal forces countering lee way.   If you combine the two vectors then they will be on the center line of the foil and in the direction of the foil arm.  But if you want just the component that is vertical, it's vector is off center further outboard.

Remember also that the Y axis is not arbitrary, as it is aligned to the direction that gravity points!  So the foil doesn't know which direction Y axis is, but the whole body as a combination of forces certainly does.

 

I don't think you can really separate out vertical and horizontal in this way. 

The counter point is that that having the horizontal lift off the lower inboard foil increases heeling moment. So just saying vertical component of lift moves outboard is useless if the same action moves horizontal down. 

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13 minutes ago, barfy said:

I would think so..showed as white in the shot. I'll keep looking for it,I think it was a zoom of a weta shot about a week ago. The hinge area makes sense as low pressure in the cavity, the leading edge wasn't mentioned and doesn't make sense to me.

Wow, ok. I missed that image. Would be cool if you find it.

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6 minutes ago, Mozzy Sails said:

I don't think you can really separate out vertical and horizontal in this way. 

Yes you can. All of the individual forces are inputs into an equation that has a resultant force. That is what the vector diagrams are being used to illustrate.

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1 hour ago, jaysper said:

On a more serious note, has LR announced their CoR if they win?

I can't imagine it would be ETNZ.

Alinghi, Bertelli dixit

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7 minutes ago, Xlot said:

Alinghi, Bertelli dixit

Dixit? No fair teaching me shit.

I have an allocation of learning 1 thing per month and strider has already taught me enough shit to consume that allocation for the next 12 months.

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1 hour ago, The Advocate said:

@erdb I am confused about which is the flat foil and which is the anhedral.

The T-foil is represented by the vertical dotted line and the horizontal dashed line. The whole analysis is based on fixing the lateral and horizontal forces, and because the T-foil can't change the direction of summed foil force, it can only have one cant angle for a given lateral / horizontal force combo. The anhedral foil on the other hand can take different cant angles and use the flaps to change the distribution of foil forces between the two wing halves. The two wing halves of the anhedral are the red and green lines.

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4 hours ago, Stingray~ said:

I forget, the foil cant angle (example 62) is the angle from... which plane? 

As @erdb mentioned, the boats record the foil arm angle.  But we need the foil cant angle from the horizontal.

The difference is 42°.    Subtract this from the reported foil arm cant, so 60° foil arm = 18° foil cant.

image.png.da11db5bd54f0af595e9b9e04d0dc18f.png

image.png.b509849bfd0689e7e5b51ab11e076e6a.png

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Just now, erdb said:

The T-foil is represented by the vertical dotted line and the horizontal dashed line. The whole analysis is based on fixing the lateral and horizontal forces, and because the T-foil can't change the direction of summed foil force, it can only have one cant angle for a given lateral / horizontal force combo. The anhedral foil on the other hand can take different cant angles and use the flaps to change the distribution of foil forces between the two wing halves. The two wing halves of the anhedral are the red and green lines.

Copy that, thank you. Great work!

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1 hour ago, sosoomii said:

I’ve been slow to appreciate this definition of cant angle, but that means the two foils above have different cant angles, because the end of the arm is lower on the T foil.  That means doing a like-for-like comparison of LR and TR needs an offset applying.

Presumably, the FCS reports the cant angle the same way for all boats regardless of the length of the foil arm. We just don't know exactly what their reference point it.

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3 minutes ago, jaysper said:

Dixit? No fair teaching me shit.

I have an allocation of learning 1 thing per month and strider has already taught me enough shit to consume that allocation for the next 12 months.

Habemus  COR

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45 minutes ago, The Advocate said:

image.png.52833b9a518bbc0559a23927b8ee7a79.png

I can't argue with the force vectors shown in the diagram, but...

The first time I went skydiving, it was in a small plane - IIRC a Cessna. The RHS door is taken off for easy egress, and as I was the first to jump, I was right at the open door. When the plane banked right, I expected centrifugal force to keep me in the plane, but I nearly fell out, there seemed to be no force there at all!

Go figure?  :blink:

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4 minutes ago, MaxHugen said:

I can't argue with the force vectors shown in the diagram, but...

The first time I went skydiving, it was in a small plane - IIRC a Cessna. The RHS door is taken off for easy egress, and as I was the first to jump, I was right at the open door