Tornado-Cat

Boats and foils comparison

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1 hour ago, justsomeone said:

Anhedral gives the possibility of advantages in two possible areas

separate control over vertical and horizontal life due to separate control of the flaps on each side

That assumes that the foil is canted such that one part is more or less horizontal and the other part more or less vertical. That would require a cant of about 60 degrees. I haven’t seen anything like that much cant, or that much anhedral. 
 

Mostly the end of the arm seems to operate about vertical, so very little cant. If more lift to windward is required, they just cant the foil a bit. 

1 hour ago, justsomeone said:

improved beach tolerance due to the fact that whole foil don't break surface at the same time, gradual loss of life.

I think that’s a Furphy. If the above theory is correct, then the “horizontal” part will breech just the same, and the “vertical” part isn’t providing much vertical lift so the boat still drops the same regardless. In a neutral position with no cant, the apex of an anhedral foil is about 600 mm closer to the surface than the T of a flat foil with the tips at the same depth, so more likely to ventilate.

A flat foil is possibly canted slightly to windward, so the whole foil may not breech anyway. Videos have shown tip breeches without ventilating the whole foil. 
 

If the joint between the arm and foil was the same distance from the end of the arm for both configurations, then anhedral makes sense. But it’s not. Every mm of anhedral raises the joint (assuming a flat foil is at the lowest allowed position).

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5 hours ago, justsomeone said:

Anhedral gives the possibility of advantages in two possible areas

separate control over vertical and horizontal life due to separate control of the flaps on each side
improved beach tolerance due to the fact that whole foil don't break surface at the same time, gradual loss of life.

From the videos of tip breaches it seems that the outboard wing is carried quite a bit higher and breaches first; the entire wing is canted out and lifting the boat upwind as was hypothesized. A flat wing would probably poke the tip out earlier.

But certainly big advantage on the leeway resistance from the inboard wing as you mention.

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13 hours ago, Tornado-Cat said:

Obviously foil arms are the same length. ... if they want to keep the same length.

If they want to keep the same length the arms are the same length, well yes thats true.

But they don't have to keep the same length which was the point as I read it & I do think it looks like the Anhedral version has a chunkier vertical section.

A0f991t.png

Blue red & yellow are all legal but have different vertical section lengths, if they're sticking a particular volume of lead in there it does make sense that the shorter one would need to be fatter.

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19 hours ago, Boink said:

I recall this being discussed in the old ETNZ forum. The length of the foil arm extension reflects filling the "foil box" as described in the rules, so where there is anhedral only the tips of the foil reach the lower corners of the box, whereas the flat T - the whole foil will lie along the lowest extremity of the "foil box" with the difference being the length of the foil arm extension . If your numbers are correct, they are trying to pack approximately 80 litres of lead in either arrangement. 

 

14 hours ago, nav said:

Nicely highlighted and explained.

Just be careful with "foil arm" ......... it is specified in the rule, is a supplied part and cannot be altered, (so all are of uniform length)

But what then to call that "variable length leg/connector" which is actually part of the 'T' shaped foil wing 'assemblage' ?:o

(that as you explain, allows full advantage to be taken from the foil wing box rule)

So in my post yesterday I managed to miss the word extension which I have now added in Blue above - it was my intention to keep referring to this but posting on my phone rather than desktop does not always go smoothly.......:blink: 

Apologies @nav.

7 hours ago, justsomeone said:

Anhedral gives the possibility of advantages in two possible areas

separate control over vertical and horizontal life due to separate control of the flaps on each side
improved beach tolerance due to the fact that whole foil don't break surface at the same time, gradual loss of life.

Definitely agree with independently controlled surfaces, even on the "flat foils"- all things being equal, this would open lots more opportunity to really maximise control and performance. Dialling in lift behaviour across the foil - either with flap twist to reduce drag along foil span or even just trimming back the lift on the windward halve could extract yet more gains. 

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15 hours ago, Ex-yachtie said:

When you say "socket", do you mean "stock", as used in the drawing you've shown?

No. The stock is on the bottom of the arm. The extension, stem, strut, whatever goes from the stock to the joint. Very short on an anhedral foil, about 600 mm longer on a flat foil.

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8 hours ago, RobG said:

If more lift to windward is required, they just cant the foil a bit.

perfectly valid.

I'm not suggesting anhedral is best. Just possible reasons why designers may look at it.

Finding the design compromises required to come to an optimal solution is way beyond me. But it's very interesting try to understand how designer's are thinking.
This is the difference between the AC and SailGP!

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14 hours ago, RobG said:

Either they wasted 1/3 of their foil allowance on misdirection (maybe they’re going to have a bulb too?) or they are checking a thinner, flat foil vs a fatter anhedral foil.

As far as I can tell, both foils go to the extremes of the rule box. So I don’t see any benefit in an anhedral foil. But clearly people who know a lot more than me do. :-)

EH?!

You think these come off their foil budget - you do realise that's Te Kaahu their non-surrogate/fishing boat

Now if they ever attached these to an AC75 ...... well that would be a different story

as to which bits on any boat might be deliberate misdirection - before ACRace1 2021:wacko: ???

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8 hours ago, hoom said:

If they want to keep the same length the arms are the same length, well yes thats true.

But they don't have to keep the same length which was the point as I read it & I do think it looks like the Anhedral version has a chunkier vertical section.

A0f991t.png

Blue red & yellow are all legal but have different vertical section lengths, if they're sticking a particular volume of lead in there it does make sense that the shorter one would need to be fatter.

Well, you did, and better, the drawing I was willing to do, si I am going to use it. Each of the colour can represent a diffirent foil

1) The blue foil is the shorter one with less drag for lifting and the shorter stock with less friction at speed. It has pretty much the same lift as the red one (a bit less though) and is the fastest one, it should be use in stronger wind. The other advantage is that flat should more stable. The downside is that it need higher speed for lift, should not as good as anhedral during tacks and gybes, (if I refer to experiences on smaller foils for kites and windrsufers), needs for sure better control of the flight altitude, and is dangerous if hitting the surface. I don't think any team tried it yet.

2) The yellow is the same kind of flat foil, but wider and deeper, so more drag to lift and more friction from the stock at apeed. However it allows to lift in lighter wind, and is more tolerant to different flight altitude. This is one one of TNZ B1 foil, but I think (some observers here may tell) that it's the one that have been crashing most often.

3) The red anhedral is longer for a smaller span, so more drag for lift than the blue and less friction at speed than the yellow. I could be more unstable (it is the case for board, but it could be different for a boat with a rudder foil) but surely better for tacks and gybes. If you take off the tip at both ends that's what AM and Ineos have. With the tip it looks like the W wind of LR.

But I am sure some will have different opinions here. The real specialists have the numbers to figure the best compromise, at least that is what they must be working on.

Which is more complicated is that they can also 1) adjust the flaps 2) decide to position the foil arm differently, but I don't know how the fcs allows it 3) sail with ww or lw heel, at least some times.

That makes an interesting equation....

 

 

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7 hours ago, RobG said:

No. The stock is on the bottom of the arm. The extension, stem, strut, whatever goes from the stock to the joint. Very short on an anhedral foil, about 600 mm longer on a flat foil.

So what's the "socket"?

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5 hours ago, Ex-yachtie said:

So what's the "socket"?

I guess the connection is a mortise and tenon joint, where the “socket” is the mortise and the stock is the tendon. I think that part is pretty much the same on flat and anhedral foils. The unnamed part is the strut from the bottom of the stock to the top of the foil. 

To me, “strut” is too generic, maybe stem is suitable?

The interesting part for me is that the longer stem lets ETNZ use a thinner section on a flat foil. Every knows thin is fast. And a flat foil runs the joint deeper given the foil box rule. Does that make it “better” than a fatter (bulb-less) anhedral foil?

I think it might as I just don’t see the benefit of unaligned lift vectors of an anhedral foil vs a fatter foil with shallower joint.

ETNZ might be testing anhedral foils on the test boat because they think they have the flat foil sorted but are still optimising the anhedral design. Or the flat foil is actually shit so has been canned. :unsure:

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47 minutes ago, RobG said:

…and the stock is the tendon.

Tenon.

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10 hours ago, nav said:

You think these come off their foil budget - you do realise that's Te Kaahu their non-surrogate/fishing boat

I was referring to the foils on Te Aihe (one flat, one anhedral). 

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17 hours ago, hoom said:

If they want to keep the same length the arms are the same length, well yes thats true.

But they don't have to keep the same length which was the point as I read it & I do think it looks like the Anhedral version has a chunkier vertical section.

A0f991t.png

Blue red & yellow are all legal but have different vertical section lengths, if they're sticking a particular volume of lead in there it does make sense that the shorter one would need to be fatter.

@Ex-yachtie, the word I used, properly or improperly, as "socket" is the distance between the foil and the upper permitted end on the foil arm. So the yellow, red or blue verticla part of the foil that fits on the foil arm.

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here is a good visual for you,

in the testing video they have 4 plates of what looks to me Mildsteel (why would you bother with anything more expensive?)

with MS being about 0.7 the density of Lead ... you would ballpark need 3 plates of the same size made of lead

1 tucked up in the attachment stub and 1 in each of the Foil wings ... easy as don't you think?

image.png.f51a5a0aaa800f3dd46bee374d58fd2f.png

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8 hours ago, Lickindip said:

here is a good visual for you,

in the testing video they have 4 plates of what looks to me Mildsteel (why would you bother with anything more expensive?)

with MS being about 0.7 the density of Lead ... you would ballpark need 3 plates of the same size made of lead

1 tucked up in the attachment stub and 1 in each of the Foil wings ... easy as don't you think?

Wasn't the test load designed to er... test the load of the system in practise, e.g. the foil arms would be lighter but will be under similar load due to pushing water etc out the way

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I finally got around to creating a graphic of Te Aihe's foils based on the image in post 857. The green line is the starboard foil, red is port, simply traced from the image. The magenta rule box is just scaled to fit over the foils. The foil tips are a bit long due to the limitations of the application I was using, but I think they're good enough.

The anhedral angle is about 15°, so canting 15° makes the outboard part horizontal and the inboard part about 30 down°.

Given the same amount of cant, both foil tips (flat, anhedral) will breech at the same time and the flat foil will have more strut in the water with the tip at the same depth.

205897308_TeAihefoilschematic.thumb.png.6cfed02818af36b71a0e2d26382574ae.png

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1 hour ago, RobG said:

I finally got around to creating a graphic of Te Aihe's foils based on the image in post 857. The green line is the starboard foil, red is port, simply traced from the image. The magenta rule box is just scaled to fit over the foils. The foil tips are a bit long due to the limitations of the application I was using, but I think they're good enough.

The anhedral angle is about 15°, so canting 15° makes the outboard part horizontal and the inboard part about 30 down°.

Given the same amount of cant, both foil tips (flat, anhedral) will breech at the same time and the flat foil will have more strut in the water with the tip at the same depth.

205897308_TeAihefoilschematic.thumb.png.6cfed02818af36b71a0e2d26382574ae.png

I just tinkered around with some numbers based in the two extremes allowed in the rule, maximum anhedral and the planar foil. My calculations are based on a simplified, trapezoidal version of the dotted red boundary and I neglected the strut at the top which is the same for any foil.

If you use the maximum possible anhedral the max span of the foil increases from 4m to 4.24m (+6%). Assuming constant area this increases the aspect ratio by 12.25%.

The combined length of the leading edge which can be used to approximate wetted area decreases by almost 10%.

To generate the same vertical force the total lift of the anhedral foil needs to be 6% higher. Taking into account that induced drag is proportional to lift squared divided by aspect ratio the induced drag is the same for both.

This still leaves the wetted area advantage for the max anhedral foil which means it should have less drag. Furthermore, I can imagine additional benefits from less drag at the junction due to the larger angle between strut and foil. However, it will operate somewhat closer to the surface.

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6 hours ago, neuronz said:

I just tinkered around with some numbers based in the two extremes allowed in the rule, maximum anhedral and the planar foil. My calculations are based on a simplified, trapezoidal version of the dotted red boundary and I neglected the strut at the top which is the same for any foil.

It has occurred to me that not only must the main part of the foil must fit in the box, but also the flaps at full extension (up and down) including any twist in the foil. So the bounding box in my graphic is fitted too tightly to the foil outlines. If about 200 mm is allowed at the bottom for flap deflection and say 100 mm at the top (assuming they'll use a lot more down than up) the max horizontal span of the foils is significantly reduced, maybe to 3.5 m. It's impossible to know precisely without knowing how far up and down the flaps go at full extension.

Also, in calculating drag, you can't omit the opposing forces produced by an anhedral foil running with zero cant. At 15° anhedral, about 3.4% of the total lift of each foil is opposing the lift of the other, and 96.6% is up. Canting the foil 15° means the outboard wing is 100% up and the inboard foil (now at 30° below horizontal) is 86.6% up and 13.4% to windward, so no opposing force and the horizontal component is useful. Using a flat foil the same way means less side force (3.4% of the whole wing vs 13.4% of half a wing), so I think I've found why anhedral works when canted. The flat foil will also have more stem in the water, so more drag from that. It doesn't make any difference in regard to flying height or the tip piercing the surface since they're in relatively the same place with respect to the arm.

There was a picture of the ENTZ test boat with about 15° cant on the windward foil, so that might be the magic number for cant and anhedral.

The flat foil may well come into its own in light conditions when it can be run much closer to the surface to reduce stem drag and avoid the inherent horizontal force drag of an anhedral foil with zero cant. But it's also more prone to ventilation drops…

PS. In the graphic, the top of the stem of each foil is at the bottom of the grey portion of the of the arm, providing a datum for positioning the foils over one another. Also, no scaling was applied so they are at the same scale (provided the original image was not overly distorted).

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6 minutes ago, RobG said:

It doesn't make any difference in regard to flying height or the tip piercing the surface since they're in relatively the same place with respect to the arm

Isn't the entire outboard wing, when horizontal on the anhedral, the same distance from the surface? Which would breach the entire lifting wing, rather than just a tip ventilation on the flat foils?

Nice work guys btw. :D

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12 hours ago, RobG said:

It has occurred to me that not only must the main part of the foil must fit in the box, but also the flaps at full extension (up and down) including any twist in the foil. So the bounding box in my graphic is fitted too tightly to the foil outlines. If about 200 mm is allowed at the bottom for flap deflection and say 100 mm at the top (assuming they'll use a lot more down than up) the max horizontal span of the foils is significantly reduced, maybe to 3.5 m. It's impossible to know precisely without knowing how far up and down the flaps go at full extension.

Also, in calculating drag, you can't omit the opposing forces produced by an anhedral foil running with zero cant. At 15° anhedral, about 3.4% of the total lift of each foil is opposing the lift of the other, and 96.6% is up. Canting the foil 15° means the outboard wing is 100% up and the inboard foil (now at 30° below horizontal) is 86.6% up and 13.4% to windward, so no opposing force and the horizontal component is useful. Using a flat foil the same way means less side force (3.4% of the whole wing vs 13.4% of half a wing), so I think I've found why anhedral works when canted. The flat foil will also have more stem in the water, so more drag from that. It doesn't make any difference in regard to flying height or the tip piercing the surface since they're in relatively the same place with respect to the arm.

There was a picture of the ENTZ test boat with about 15° cant on the windward foil, so that might be the magic number for cant and anhedral.

The flat foil may well come into its own in light conditions when it can be run much closer to the surface to reduce stem drag and avoid the inherent horizontal force drag of an anhedral foil with zero cant. But it's also more prone to ventilation drops…

PS. In the graphic, the top of the stem of each foil is at the bottom of the grey portion of the of the arm, providing a datum for positioning the foils over one another. Also, no scaling was applied so they are at the same scale (provided the original image was not overly distorted).

Is there a rule that the foil has to fit in the box in any configuration? Anyway, even a 50% flap will not require 200mm of space as they will only run a few degrees of flap angle.

Furthermore, I have included the additional lift due to the anhedral angle in the calculation (+6%), but it is cancelled by the increased aspect ratio.

Last but not least anhedral has zero influence on the cant angle of the foil arm since the direction of the total lift does not change. There also is no magic angle. The best angle is where vertical and transverse forces are in equilibrium with the least amount of total drag.

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On 2/1/2020 at 9:16 PM, neuronz said:

Is there a rule that the foil has to fit in the box in any configuration?

Yes:

13.4 With the foil arm lowered to its minimum cant angle, and at all foil flap rotation angles and twists, the foil
wing and foil flaps, projected to TRP, must lie entirely within the area shaded in Figure 13.1.

My emphasis, the rule author's Oxford comma.

On 2/1/2020 at 9:16 PM, neuronz said:

Anyway, even a 50% flap will not require 200mm of space as they will only run a few degrees of flap angle.

Maybe, I don't know. But the rule says "at all foil flap rotation angles" so it's based on the extent the flaps can be moved. The flaps may well be in segments so that different flap angles are used in different segments, which can also twist the foil. It's not just about uniform camber. I expect that to initiate foiling they's use a lot more than a few degrees of flap.

On 2/1/2020 at 9:16 PM, neuronz said:

Furthermore, I have included the additional lift due to the anhedral angle in the calculation (+6%), but it is cancelled by the increased aspect ratio.

Last but not least anhedral has zero influence on the cant angle of the foil arm since the direction of the total lift does not change. There also is no magic angle. The best angle is where vertical and transverse forces are in equilibrium with the least amount of total drag.

Anhedral and cant are very important when the vectors are resolved vertically and horizontally, because that is the direction of the forces the foil is competing with: gravity and leeway. An anhedral foil can generate more windward force for the same vertical lift, albeit with a bit more drag due to the overall greater lift, than a similarly canted flat foil.

Some very rough numbers: Canted 15°, a flat foil generating 7.5 t vertical lift is generating 0.264 t to windward. A 15° anhedral foil generating 7.5 t vertical will generate 0.580 t to windward, more than double the force of a flat foil. The extra drag from the additional lift is likely compensated for by less stem in the water (where "stem" is the vertical part of the foil that connects it to the stock on the end of the arm).

The above is likely not that accurate, I'll do something a bit better later.

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On 1/30/2020 at 10:45 PM, Tornado-Cat said:

1) The blue foil is the shorter one with less drag for lifting and the shorter stock with less friction at speed. It has pretty much the same lift as the red one (a bit less though) and is the fastest one, it should be use in stronger wind. The other advantage is that flat should more stable.

Well we now know why you are an armchair commentator, because you demonstrate how little you do know.

There is absolutely no good reason why you would run any foil that would fit in the upper limits of the "box" as per the blue foil that you describe.

The junction of the foils represents approximately the Centre of Lift for these foiling boats - and that replaces the Centre of Buoyancy as found on archimedian boats.

The Boats also (particlarly those with Bulbed foils) also centre their Ballast mass at these approximate junction locations.

The Boats clearly do not run the Foil extensions in a vertical orientation when they are trying to maximise the Power of the boat. They run the foil arms and its lower sections in a stance that spreads the two juction points as far apart as practically possible. 

There is NO designer worth his wage that would produce a design that does not operate on the principle of gaining the greatest RM by having the longest levers (foil arms + foil extensions) availble to them, even when this might increase WSA and drag. Especially for a High Wind range foil. You however propose a small foil on no foil arm extensions (600mm) which would give away between 1000mm (on Tangentail Projection) to a less likely 1200mm (because of the curvature and orientation of the two foil arms). 

Go get a Brazilian, you Fake News generator. 

Come on El Presidente Trump C@nt - Bluster your way out of this one........

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On 2/1/2020 at 11:55 AM, RobG said:

Also, in calculating drag, you can't omit the opposing forces produced by an anhedral foil running with zero cant. At 15° anhedral, about 3.4% of the total lift of each foil is opposing the lift of the other, and 96.6% is up. Canting the foil 15° means the outboard wing is 100% up and the inboard foil (now at 30° below horizontal) is 86.6% up and 13.4% to windward, so no opposing force and the horizontal component is useful. Using a flat foil the same way means less side force (3.4% of the whole wing vs 13.4% of half a wing), so I think I've found why anhedral works

Again, you both are assuming equal lift from both inboard and outboard wings. Flaps are measured as symmetrical in range of motion but don't need to be operated as such. Doesn't mean so much to a flat wing but could mean heaps to an anhedral wing.

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On 1/30/2020 at 2:43 PM, RobG said:

That assumes that the foil is canted such that one part is more or less horizontal and the other part more or less vertical. That would require a cant of about 60 degrees. I haven’t seen anything like that much cant, or that much anhedral. 

Why does one wing need to provide force exactly along the y or x vector? Wouldn't some degree of force that can be generated with the wing in near optimal flap condition be vectored into a sum that is still favourable, but can be adjusted for liftoff or minimum leeway without having to cant the entire arm? Or to keep the arm more vertical during lift off to increase stability? 

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16 hours ago, RobG said:

Anhedral and cant are very important when the vectors are resolved vertically and horizontally, because that is the direction of the forces the foil is competing with: gravity and leeway. An anhedral foil can generate more windward force for the same vertical lift, albeit with a bit more drag due to the overall greater lift, than a similarly canted flat foil.

Some very rough numbers: Canted 15°, a flat foil generating 7.5 t vertical lift is generating 0.264 t to windward. A 15° anhedral foil generating 7.5 t vertical will generate 0.580 t to windward, more than double the force of a flat foil. The extra drag from the additional lift is likely compensated for by less stem in the water (where "stem" is the vertical part of the foil that connects it to the stock on the end of the arm).

The above is likely not that accurate, I'll do something a bit better later.


 this is not correct. Assuming same angles of attack on each side of the foil the forces perpendicular to the strut compensate each other which means the total lift has to be aligned with the strut. Thus, the vertical and horizontal components are exactly the same for both types of foils.

There are two possibilities to break the symmetry, independent flap angles and leeway.

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4 hours ago, neuronz said:

There are two possibilities to break the symmetry, independent flap angles and leeway.

My initial numbers were pretty rubbish, I shouldn't have rushed it. Yes, the benefits really come from playing the lift of each wing independently. Here are some not to scale diagrams (the angles are about right, the vector lengths aren't). I'm sure I'll be corrected if they're no good. I've used a nominal total vertical lift of 7.5 t for simplicity and ignored things like strut drag which I think favours the anhedral foil anyway when canted.

When level, an anhedral foil has opposing lift so more drag than a flat foil for the same vertical lift.

543718745_0Anhedral0deg.png.49995b27017742bfd67d3620ec569aa5.png

When canted 15° and each wing of an anhedral foil is producing the same vertical lift, it provides a little more horizontal force to windward than a flat foil (please ignore scale, the flat foil vectors should be double the size so the Hz force shouldn't be so out of proportion):

230238819_1Anhedralvsflat15deg.png.1b341c811dee809bf390c446a31711d7.png

However, if the total vertical lift of an anhedral foil is kept constant but distributed more to the inboard wing, the sideways force is greatly enhanced:

407334827_2Anhedralasymlift.png.3f21e366ab05f63023316edc1565c560.png

Nothing is for free though, the increased sideways force must also increase drag. It likely also messes a bit with RM as it moves the centre of lift inboard, producing a rotation to leeward. But the angles of the foil means there are potential benefits to playing with the sideways force while keeping the vertical lift, cant and ride height more or less constant. To do the same thing, a flat foil must adjust the cant angle, which is likely a trickier solution given the arm, FCS and control software are supplied and can't be modified.

I think 15° is a magic angle only because that's probably the maximum practical angle given the dimensions in the rule before the foil length is affected too much, i.e. it's indirectly a constraint of the rule. Whether a greater angle is actually desirable is moot.

Oh, I also had an idea that the ultrasonic transmitter in the foil might be a depth detection device to measure how far the foil is below the surface. Can ultrasound waves bounce off an air—water interface?

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32 minutes ago, RobG said:

Can ultrasound waves bounce off an air—water interface?

Not as far as I know. I was wondering if these were either for a log of some sort (receiver in the rudder foil) or to do with measuring the proximity of other boats foils.... the safety "diamond" or whatever it was called when the design concept was introduced?

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25 minutes ago, Woolfy said:

Not as far as I know. I was wondering if these were either for a log of some sort (receiver in the rudder foil) or to do with measuring the proximity of other boats foils.... the safety "diamond" or whatever it was called when the design concept was introduced?

Safety diamond most likely as it's mandated gear. As I've said a month ago.

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1 hour ago, RobG said:

the centre of lift inboard, producing a rotation to leeward. But the angles of the foil means there are potential benefits to playing with the sideways force while keeping the vertical lift, cant and ride height more or less constant. To do the same thing, a flat foil must adjust the cant angle, which is likely a trickier solution given the arm, FCS and control software are supplied and can't be modified.

Nice. Exactly as I was saying. The reason these boats will be faster around the track will be due to incredible angles. We saw them on the first tack from mini frack, when these guys get the handling sorted with a year of practice and dev, these boats will amaze. Just think of the improvement all teams showed in bda with what was it, 4 months practice? Now quadruple that.

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Up wind VMG will determines who’s wins

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13 minutes ago, uflux said:

Up wind VMG will determines who’s wins

Well, they'll need boatspeed as well.

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1 minute ago, Sailbydate said:

Well, they'll need boatspeed as well.

Yep but as per the last 2 cups upwind performance is key. Down wind both boats basically have a cavitation ceiling so upwind is where the big gains are made

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36 minutes ago, barfy said:

Safety diamond most likely as it's mandated gear. As I've said a month ago.

There's no need for a distance measurement device in the foils for the diamond. It can be a fixed shape relative to the boat and allow for a max sized foil at the most beamy cant angle, plus a safety margin.

If it's a safety device, it might be a proximity alarm for anything that gets within a certain distance when the arm is raised, like blindspot monitoring in cars. It would be useful for the lee boat when both boats are on the same tack and running parallel. For crosses it will be useless given the closing speeds and angles. I just can't see that it gives any advantage over a spatial location system that knows exactly where the boats are plus their speed and heading and can predict issues (risk mitigation) rather than responding to them (damage control).

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17 minutes ago, uflux said:

Yep but as per the last 2 cups upwind performance is key. Down wind both boats basically have a cavitation ceiling so upwind is where the big gains are made

I think these boats are essentially always sailing to windward, and VMG matters always especially if there's a physical speed limit. On the downwind in Bermuda, it seemed to me that ETNZ was lower with better VMG than OTUSA, which seemed slightly faster over the ground but higher. But that's just what I think I saw, I haven't analysed it in any great detail.

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27 minutes ago, RobG said:

There's no need for a distance measurement device in the foils for the diamond. It can be a fixed shape relative to the boat and allow for a max sized foil at the most beamy cant angle, plus a safety margin.

If it's a safety device, it might be a proximity alarm for anything that gets within a certain distance when the arm is raised, like blindspot monitoring in cars. It would be useful for the lee boat when both boats are on the same tack and running parallel. For crosses it will be useless given the closing speeds and angles. I just can't see that it gives any advantage over a spatial location system that knows exactly where the boats are plus their speed and heading and can predict issues (risk mitigation) rather than responding to them (damage control).

their won't be any proxie measuring devices when it comes to judging on the water decisions, GPS with multiple units around the boat will show accurate angle and speeds ... isn't this how they measured all of jimmy's over the line starts and then animated them

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only if it was acid etch

and you got a heap on yourself

 

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5 hours ago, uflux said:

Yep but as per the last 2 cups upwind performance is key. Down wind both boats basically have a cavitation ceiling so upwind is where the big gains are made

Most days conditions were not approaching full power or cavitation last cup, and won't again in Auckland. Vmg up and down gets you to the line first. 

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5 hours ago, RobG said:

There's no need for a distance measurement device in the foils for the diamond. It can be a fixed shape relative to the boat and allow for a max sized foil at the most beamy cant angle, plus a safety margin.

If it's a safety device, it might be a proximity alarm for anything that gets within a certain distance when the arm is raised, like blindspot monitoring in cars. It would be useful for the lee boat when both boats are on the same tack and running parallel. For crosses it will be useless given the closing speeds and angles. I just can't see that it gives any advantage over a spatial location system that knows exactly where the boats are plus their speed and heading and can predict issues (risk mitigation) rather than responding to them (damage control).

True that. Like a side mirror flasher. Something to do with not slicing and dicing for sure.

Edit: maybe a backup for gps. In case of solar flares....

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On 2/3/2020 at 1:31 AM, Boink said:

The Boats also (particlarly those with Bulbed foils) also centre their Ballast mass at these approximate junction locations.

The Boats clearly do not run the Foil extensions in a vertical orientation when they are trying to maximise the Power of the boat. They run the foil arms and its lower sections in a stance that spreads the two juction points as far apart as practically possible. 

There is NO designer worth his wage that would produce a design that does not operate on the principle of gaining the greatest RM by having the longest levers (foil arms + foil extensions) availble to them, even when this might increase WSA and drag. Especially for a High Wind range foil. You however propose a small foil on no foil arm extensions (600mm) which would give away between 1000mm (on Tangentail Projection) to a less likely 1200mm (because of the curvature and orientation of the two foil arms). 

 

Again you don't know what you are talking about boinkboink:

1) you only consider the RM with the windward lever arm and not the lw

2) You tell that windward RM trumps the drag. Have you ever been on a cat over 20 kts with the lw hull pushing water ? If what you are saying is true the AC75 would have even longer arms to be faster, but they don't.

3) You pull again an assumption from your a...about what real designer will do or not do.

Could you again explain how the AC75 foil will have all their weight in the exterior part of the foil ? :D

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I ask you again. How fast have you Actually been on water wind powered, 20 knots on a cat Doesn't exactly Qualify as quick 

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25 minutes ago, JALhazmat said:

I ask you again. How fast have you Actually been on water wind powered, 20 knots on a cat Doesn't exactly Qualify as quick 

23 kts on a cat when measured, probably close to 30 kts on a windsurfer.

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30 knots of boatspeed is nothing at all like 20.  40 knots is not like anything else.

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Over 48Kts is fun, TC should try it.. actually everyone should. It wakes you up a bit 

358E228A-4E83-438E-BD95-E40BE7BD879C.png

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17 minutes ago, JALhazmat said:

Over 48Kts is fun, TC should try it.. actually everyone should. It wakes you up a bit 

43.7 was more than enough for me.

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47 minutes ago, Tornado-Cat said:

23 kts on a cat when measured, probably close to 30 kts on a windsurfer.

It's prolly all relative anyway, TC. I can recall shitting myself doing 15 kts.

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13 minutes ago, JALhazmat said:

Cool :)on what? 

This one, a few months before this video was filmed.  My run was posted on SA but I have no idea where to find it these days.

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21 minutes ago, Sailbydate said:

It's prolly all relative anyway, TC. I can recall shitting myself doing 15 kts.

I completely agree with you Sailbydate, it's all relative. 15 kts on a mono can be more frightening than 23 on a cat, which can also be more frigthening than 40 kts on a foiler.

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49 minutes ago, JALhazmat said:

Over 48Kts is fun, TC should try it.. actually everyone should. It wakes you up a bit

Yes I would like.

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1 minute ago, Tornado-Cat said:

Yes I would like.

My 48.47 wasn’t foiling 

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4 minutes ago, JALhazmat said:

My 48.47 wasn’t foiling 

Congrats. I might buy a kite, but it's difficult to sail different things with limited time...

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15 minutes ago, Tornado-Cat said:

Do you helm ?

I did, but only to around 36 knots.  Scared myself enough to hand it over to the frenchie after that.  This was pre-foil days; C-boards and a straight dagger.

Gunboat G4 on foils at 36 was not nearly as scary as the MOD.

 

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Just now, Tornado-Cat said:

MODs are amazing boats.

So sorry that the series never really succeeded.

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1 hour ago, Rennmaus said:

So sorry that the series never really succeeded.

It would have but for the guy who created it.  The boat is true genius.

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Oh man, that sent me down memory lane.
Caution, mega thread drift ahead!
Some random shots from the days of yore...

ph-25420.thumb.jpg.b0083ae5858aa3ced24e38ac46736e97.jpg

ph-25486.thumb.jpg.1eb73b024b99855df066fd6995ba93c6.jpg

ph-25515.thumb.jpg.9197c0c7e30864d2f588476a00205fca.jpg

ph-25544.thumb.jpg.80fa5434df9fcf223cd05fc80587b23e.jpg

ph-25525.thumb.jpg.957f737d2750db53f59601534a8f163f.jpg

[/threaddriftend]

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Yes and not, the thread is about boats comparison, implicitely AC75 but it can also be read more widely. And it's about sailing, better than trading insults as in some other threads.

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On 2/8/2020 at 11:32 PM, Tornado-Cat said:

Yes and not, the thread is about boats comparison, implicitely AC75 but it can also be read more widely. And it's about sailing, better than trading insults as in some other threads.

 

Agree

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On 2/3/2020 at 2:31 PM, Boink said:

Well we now know why you are an armchair commentator, because you demonstrate how little you do know.

There is absolutely no good reason why you would run any foil that would fit in the upper limits of the "box" as per the blue foil that you describe.

The junction of the foils represents approximately the Centre of Lift for these foiling boats - and that replaces the Centre of Buoyancy as found on archimedian boats.

The Boats also (particlarly those with Bulbed foils) also centre their Ballast mass at these approximate junction locations.

The Boats clearly do not run the Foil extensions in a vertical orientation when they are trying to maximise the Power of the boat. They run the foil arms and its lower sections in a stance that spreads the two juction points as far apart as practically possible. 

There is NO designer worth his wage that would produce a design that does not operate on the principle of gaining the greatest RM by having the longest levers (foil arms + foil extensions) availble to them, even when this might increase WSA and drag. Especially for a High Wind range foil. You however propose a small foil on no foil arm extensions (600mm) which would give away between 1000mm (on Tangentail Projection) to a less likely 1200mm (because of the curvature and orientation of the two foil arms). 

Go get a Brazilian, you Fake News generator. 

Come on El Presidente Trump C@nt - Bluster your way out of this one........

 

On 2/8/2020 at 10:40 PM, Tornado-Cat said:

Again you don't know what you are talking about boinkboink:

1) you only consider the RM with the windward lever arm and not the lw

Where on earth do you draw this conclusion from having re-read my ENTIRE post above? Not running the Foil arm extension in the vertical stance means that the longer the arm extension the longer the Lever arm becomes....... It is also the immersed arm (the leeward arm) - yet you jump up and down like you are having hysterical fit talking about I how do not reference the "lw" - FFS grow up.

2) You tell that windward RM trumps the drag. Have you ever been on a cat over 20 kts with the lw hull pushing water ? If what you are saying is true the AC75 would have even longer arms to be faster, but they don't.

The Foil Arms are not allowed to be any longer - the Arms are supplied - the foil arm extensions are limited by the "Box" - how on earth could they be any longer?

The point is that they would try and put the point of Lift at the end of the longest lever arm to maximise RM - your proposal would not generate max RM = DUMB & FOOLISH. Period.

3) You pull again an assumption from your a...about what real designer will do or not do.

Could you again explain how the AC75 foil will have all their weight in the exterior part of the foil ? :D

What do you think those Bulbs contain? The whole foil arm + extension + foils are limited to c.900Kg of which the foil arm is 300Kg. Therefore the teams have an ability to make their Foil arm extension + Bulb + Foils approx c.600Kg each side.

At the density of Lead they only need to find c.53 litres of Lead to hide within the foil arm extension, bulb or foil wings or any combination of those elements. This is suggestive of why the NZ foils are so much larger in plan and section - but with the compensation of no BULB drag - which is why I have alluded to these foil shapes being their light to moderate foil options. Who knows what they might develop post Calagari. 

 

You write about thid thread being about sailing and not trading insults - yet that is exactly what you do.

I am so bored with your hypocritical reactionary postings. You do not bring insight, enlightenment, observation and certainly not humour.

You clearly have such a tenuous grasp of what is going on that you cannot contribute.

You try and deflect to a Boat speed contest. Like you are 7 years old in Junior school playground. If 23 knots is your greatest achievement - then you are clearly lacking in many regards, including sailing experience.

You are so mad and deluded in your personal attacks at me, that is now appropriate to Label you as the Syphilitic Trump Cunt.......... Work it out Einstein

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On 2/8/2020 at 7:02 PM, Tornado-Cat said:

MODs are amazing boats.

Remember being on one of the 72s in SF heading to the start box between races and having to avoid a MOD70 that bore away thinking we would pass to windward when we were already committed to go under them. They were going full chat and the boys on the 72 were eating sandwiches and making the MOD look like it was standing still. Was a lot closer than anyone wanted!

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12 hours ago, Boink said:

Where on earth do you draw this conclusion from having re-read my ENTIRE post above? Not running the Foil arm extension in the vertical stance means that the longer the arm extension the longer the Lever arm becomes....... It is also the immersed arm (the leeward arm) - yet you jump up and down like you are having hysterical fit talking about I how do not reference the "lw" - FFS grow up.

Wrong, the 700 mm part of arm it concerns is mostly vertical in the water, the lever would not really change but the drag would increase substancially.

The Foil Arms are not allowed to be any longer - the Arms are supplied - the foil arm extensions are limited by the "Box" - how on earth could they be any longer?The point is that they would try and put the point of Lift at the end of the longest lever arm to maximise RM - your proposal would not generate max RM = DUMB & FOOLISH. Period.

The 700 mm of extra arm provides some extra RM at the cost of more drag with the LW foil, which you never thought of. You should know that for these boats drag is generally more important than RM.

Do you know what is the best compromise ? You don't, but you are dumb enough to assert that you know.

The more you post the more BS you write. At least you could write about some hypothesis, as teams may not already know themselves the best compromises depending on the weather, but your assertions and pompous verbiage hide pure ignorance.

By the way, are you still claiming that the exterior part of the foil will be heavier than the other one ?  :D

 

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On 2/12/2020 at 8:30 AM, Tornado-Cat said:

Wrong, the 700 mm part of arm it concerns is mostly vertical in the water, the lever would not really change but the drag would increase substancially.

The 700 mm of extra arm provides some extra RM at the cost of more drag with the LW foil, which you never thought of. You should know that for these boats drag is generally more important than RM.

You are so full of crap.

Look at the photo attached.

Now try and tell everyone that the Foil Arm Extension is being run vertically.

You can do this with several photos - the same result applies. You will argue all sorts of irrelevant crap - when Immersed, the arm extension is nowhere near vertical.

Oh and look at the angle that the Foil arm extension flies at whilst in the air, yes near Horizontal - Coincidence - I think not - but again if you want to not deploy your windward foil at maximium extension then go right ahead and celebrate your 23 knots of BS.......

As I pointed out - it is quite commonly seen that teams deploy the arms to widen the stance to the Maximum possible, to gain max. RM.

If they do run upto the full 700mm extra that could be permitted (on a flat T-foil) then they have the ability, and option, to run the foil arm extension vertically with little immersion to minimise Drag - but to suggest that they would run an option limiting choice of no foil arm extensions is Ludicrous - much like you - except without the humour.......

You don't have the intelligence to accept this. You want to foul the player (me), rather than play the ball (the facts)....... Pathetic

Orientation of Foil Arm Extension in Water.jpg

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On 1/13/2020 at 6:31 AM, phill_nz said:

16.3 The wetted part of the rudder must be symmetric about the rudder centre plane, with a build tolerance
of 3.0 mm.
16.4 With the rudder centre plane aligned with LCP, and at all rake angles that can be achieved, no wetted part
of the rudder shall extend:
(a) below a waterline plane 3.500 m below MWP;
(b) aft of TRP; or
(c) forward of a transverse plane 1.500 m forward of TRP.
 

Has anybody worked out the corresponding rake range? Of course, this depends on the stabilizer chord

 

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11 hours ago, Boink said:

You are so full of crap. Look at the photo attached. Now try and tell everyone that the Foil Arm Extension is being run vertically. You can do this with several photos - the same result applies. You will argue all sorts of irrelevant crap - when Immersed, the arm extension is nowhere near vertical.

^^ So, you post of photo of foil arm in the air to prove that the 700 mm part of the foil extension is not vertical in the water ? Are you even dumber than I thought ? Now, even if the foil extension is not perfectly vertical depending on how the boat is heeling to windward or leeward, the additional or decrease of lever arm is minimal because of the few degrees angle it would involve.

Oh and look at the angle that the Foil arm extension flies at whilst in the air, yes near Horizontal - Coincidence - I think not - but again if you want to not deploy your windward foil at maximium extension then go right ahead and celebrate your 23 knots of BS.......As I pointed out - it is quite commonly seen that teams deploy the arms to widen the stance to the Maximum possible, to gain max. RM.

We know that the maximum foil extension in the air increases the RM, but how can you assert it is  more efficient than the drag it could save when in the water. It takes only a boink to claim it.

If they do run upto the full 700mm extra that could be permitted (on a flat T-foil) then they have the ability, and option, to run the foil arm extension vertically with little immersion to minimise Drag - but to suggest that they would run an option limiting choice of no foil arm extensions is Ludicrous - much like you - except without the humour.......

And here we can see how ignorant you are, because if they do it for the reason you mention, they will fly higher and loose the RM you have been praising.

You don't have the intelligence to accept this. You want to foul the player (me), rather than play the ball (the facts)....... Pathetic

Orientation of Foil Arm Extension in Water.jpg

You are stubborn and make looks Doug Lord as brillant and opened.

I don't know if one team will use the possible T foil fitting in the blue line, as I said they would need perfect control and could only use it in strong conditions.

However a flat hull could,

1) minimize the drag thanks to a small foil and a shorter foil extension

3) foil lower for higher RM with the same distance between hull and water at the cost a 700mm shorter windward lever arm.

I don't know if they will do it because of the control required and the difficulty to get out of the water with such a small foil.

You are from the old school that RM trumps everything while these boat have lots of power and are mainly  fighting against drag.

But instead of considering the options rationally you will come back with another stupid rant and come up with more idiocies.

 

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7 minutes ago, Tornado-Cat said:

You are stubborn and make looks Doug Lord as brillant and opened.

I don't know if one team will use the possible T foil fitting in the blue line, as I said they would need perfect control and could only use it in strong conditions.

However a flat hull could,

1) minimize the drag thanks to a small foil and a shorter foil extension

3) foil lower for higher RM with the same distance between hull and water at the cost a 700mm shorter windward lever arm.

I don't know if they will do it because of the control required and the difficulty to get out of the water with such a small foil.

You are from the old school that RM trumps everything while these boat have lots of power and are mainly  fighting against drag.

But instead of considering the options rationally you will come back with another stupid rant and come up with more idiocies.

 

This is so typical of you.

You now morph the argument to not tackle the evidence that beats you down.

You use a brightly coloured font (in Trumpesque orange no less), everywhere - you bemoan a Muppet of a fLorDia FuckwiT.

You must be Dougie's puPPeT....

Sad Little boy.....

Time for a(nother) medication review.

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4
17 minutes ago, Tornado-Cat said:

You are from the old school that RM trumps everything while these boat have lots of power and are mainly  fighting against drag.

ill agree with your comment that "these boats have lots of power" ... but much the same as cars with big engines, you cant transfer it without good wheels

Maximising RM as etnz did with there windward rudder at the last cup is a vital part of these designs

the ballpark measurement is 12% more between foils in the photo below. not to mention the slightly more RM you will bet from the hull being fractionally wider pivoted out

round that off to 10% so not to split too many hairs ... are you saying that is not an advantage a team would want?552089239_OrientationofFoilArmExtensioninWater.thumb.jpg.bd9d4f97283e57d6023d77d5e49fb7f0.jpg.7d4281c40a449f6cb853b5d0e391036d.jpg

 

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2 minutes ago, Lickindip said:

ill agree with your comment that "these boats have lots of power" ... but much the same as cars with big engines, you cant transfer it without good wheels

Maximising RM as etnz did with there windward rudder at the last cup is a vital part of these designs

the ballpark measurement is 12% more between foils in the photo below. not to mention the slightly more RM you will bet from the hull being fractionally wider pivoted out

round that off to 10% so not to split too many hairs ... are you saying that is not an advantage a team would want?552089239_OrientationofFoilArmExtensioninWater.thumb.jpg.bd9d4f97283e57d6023d77d5e49fb7f0.jpg.7d4281c40a449f6cb853b5d0e391036d.jpg

 

Your drawing is wrong to windward and does not represent the 700mm part.

It even more wrong with the leeward one as boink cut and paste is not the reality, have a look at the photo ( I would have to find one from behind though).

 

 

 

A0f991t.png.dba02131a5942c4fe671d82be5ea85d5.png

Capture.PNG

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2 minutes ago, Tornado-Cat said:

Your drawing is wrong to windward and does not represent the 700mm part.

It's even more wrong with the leeward one as boink cut and paste is not the reality, have a look at the photo ( I would have to find one from behind though).

 

 

 

A0f991t.png.dba02131a5942c4fe671d82be5ea85d5.png

Capture.PNG

 

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i apologise for using MSpaint which I agree isn't accurate ... next time ill do it in AutoCAD ... or would you prefer solidworks?

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3 hours ago, Xlot said:

Has anybody worked out the corresponding rake range? Of course, this depends on the stabilizer chord

 

If I’m not mistaken, it should be about 15 degrees - way more than the 3 degrees range for AC50s

 

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fuck it you wound me up and wanted to draw this anywho

 

9.34% more RM from you windward foil

and an additional 5.37%  from hull weight in this particular orientation if the foil arm stock isn't vertical

the blue line is just an arbitrary water line when foiling

image.png.7f938e4f895279e14aef07e0ee67b9c2.png

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21 minutes ago, Xlot said:

If I’m not mistaken, it should be about 15 degrees - way more than the 3 degrees range for AC50s

 

Nice.I mentioned it a while ago and got slammed for not accounting for max chord of the foil in the movement. If anyone uses the max chord. Hope you allowed for it. :unsure:

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20 minutes ago, Lickindip said:

fuck it you wound me up and wanted to draw this anywho

 

9.34% more RM from you windward foil

and an additional 5.37%  from hull weight in this particular orientation if the foil arm stock isn't vertical

the blue line is just an arbitrary water line when foiling

image.png.7f938e4f895279e14aef07e0ee67b9c2.png

What max beam did you calculate ?

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Just now, Lickindip said:

fuck it you wound me up and wanted to draw this anywho

 

9.34% more RM from you windward foil

and an additional 5.37%  from hull weight in this particular orientation if the foil arm stock isn't vertical

the blue line is just an arbitrary water line when foiling

image.png.7f938e4f895279e14aef07e0ee67b9c2.png

Excellent work.

Your efforts to formalise the gains that are as plain as the nose on a face, are very appreciated.

The fact that a team can have a basic premise of architecture that translates to gains in RM yet have the option to operate it at a variety of attitudes and immersion levels to mitigate (and I say mitigate - not remove) the additional drag, would, where the foils numbers are so restricted, be the most flexible solution.

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1 minute ago, Tornado-Cat said:

What max beam did you calculate ?

Stop focusing on trying to discredit the premise, by arguing or seeking how many decimal points were applied.

The foil arm extensions are not anywhere near vertical when immersed.

3 sets of foils only allowed, and restriction of 20% change to those foils, leads teams to require the most flexible and overlapping of solutions. 

Super refined foils with a very small window of operation - the classic one trick pony - leave the team too exposed if the wind or sea state changes. 

You have sailed in Auckland, right?

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3 minutes ago, Boink said:

Stop focusing on trying to discredit the premise, by arguing or seeking how many decimal points were applied.

The foil arm extensions are not anywhere near vertical when immersed.

3 sets of foils only allowed, and restriction of 20% change to those foils, leads teams to require the most flexible and overlapping of solutions. 

Super refined foils with a very small window of operation - the classic one trick pony - leave the team too exposed if the wind or sea state changes. 

You have sailed in Auckland, right?

You dumb boink are fighting to prove what teams may not already know.

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2 minutes ago, Boink said:

3 sets of foils only allowed, and restriction of 20% change to those foils, leads teams to require the most flexible and overlapping of solutions. 

Super refined foils with a very small window of operation - the classic one trick pony - leave the team too exposed if the wind or sea state changes. 

You have sailed in Auckland,

I reckon

-early takeoff at lower end conditions

-ability to trade speed for vmg in the high end

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41 minutes ago, Lickindip said:

fuck it you wound me up and wanted to draw this anywho

 

9.34% more RM from you windward foil

and an additional 5.37%  from hull weight in this particular orientation if the foil arm stock isn't vertical

the blue line is just an arbitrary water line when foiling

image.png.7f938e4f895279e14aef07e0ee67b9c2.png

I don't know what figures you took, whatever, let's say you are right, have you figured the difference between a small T foil at the top allowed and a large T at the maximum allowed ? + 55% profile for drag.