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Boats and foils comparison


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8 minutes ago, Basiliscus said:

I don't use XFLR5, so I can't help you there.  But here's how I generate coordinates for Xfoil.  It's perhaps an overly manual process, but it's not so onerous that I've been driven to automate it more fully.

My CAD program is Rhino.

Rhino at USD 995 is way way beyond my budget, but I'll scout around for an alternative CAD app that can maybe do the same.  Thanks for outlining the procedure.  :)

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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

Posted Images

Wouldn't  the best way to reduce drag and increase lift low down thus allowing smaller foils etc be to allow the foils to vary in angle.

Quite hard to do from a strength perspective but it would allow smaller foils quite aggressive AOA at lift off maybe 15deg then reducing to near zero for the speed runs thus raking boat and mast back for lots of lift and very clean drag profile at speed also.

Flaps for trim and control in the run but small clean foils.

The discussion about super critical above 55knts is fine but for these boats to get around the track 5 or 10 knts faster its not higher top speeds you need its higher average speeds and they are closer to half the cavitation speed than not.  

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3 hours ago, MaxHugen said:

Rhino at USD 995 is way way beyond my budget, but I'll scout around for an alternative CAD app that can maybe do the same.  Thanks for outlining the procedure.  :)

The program that Rhino was developed from (I think) was free and available last time I looked. Buggered if I can remember the name of it though, haven't had it on the last few laptops.

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The flap pivot rules were quite limiting. But even with those rules all teams ended up with surface pivot points. I'm not sure how much of that was just running out of time  / needing reliability. And the team with the most complex mechanisms within the wings were probably the slowest foils (or had most difficulty at low speed at least).

I still think one of the biggest things they could do to widen the wind range would be to open up the flap rules including deformation of main wing. But you'd probably have to slacken the CoG rule for the foils too, to allow those extra mechanisms in without bulking out too much. 

But, having said all that, ETNZ won by moving much of the mechanisms clear of the water and housing in the spat. It's probably that plus the ability of run the T at more extreme cant angles that made the biggest difference. 

 

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4 minutes ago, The Advocate said:

The program that Rhino was developed from (I think) was free and available last time I looked. Buggered if I can remember the name of it though, haven't had it on the last few laptops.

Hmmm, thanks, might see what I can find.  I'm currently trying an open source program, FreeCAD, but it's become a battle and so far I'm on the losing side!

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2 minutes ago, The Advocate said:

Mmm fair enough. We used it on a few projects but nothing super serious. Quite a few NA's I know rated it highly. I know they stopped developing it a while back.

Perhaps it was just me that was limited. :P

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24 minutes ago, Mozzy Sails said:

But, having said all that, ETNZ won by moving much of the mechanisms clear of the water and housing in the spat. It's probably that plus the ability of run the T at more extreme cant angles that made the biggest difference.

What mechanisms could they move?

I would have thought there wasn't much there, apart from the actuator(s) and a couple of hydraulic lines.

Ps: and some sensors I guess.

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2 minutes ago, MaxHugen said:

What mechanisms could they move?

I would have thought there wasn't much there, apart from the actuator(s) and a couple of hydraulic lines.

Hydraulics / electronics actuators. I presume that is why they have the access window to the spat.

LR has an access window a little lower (covered by tape in some photos or seen with water dribbling out).

INEOS had mechanisms within the foil, and you could see they were deconstructing the wing itself fairly regularly by the way the screw holes were covered and re-fared (possibly screw drive or something).

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10 minutes ago, MaxHugen said:

What mechanisms could they move?

I would have thought there wasn't much there, apart from the actuator(s) and a couple of hydraulic lines.

Ps: and some sensors I guess.

I would have thought the sensors would be further upstream.

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4 minutes ago, Mozzy Sails said:

Hydraulics / electronics actuators. I presume that is why they have the access window to the spat.

LR has an access window a little lower (covered by tape in some photos or seen with water dribbling out).

INEOS had mechanisms within the foil, and you could see they were deconstructing the wing itself fairly regularly by the way the screw holes were covered and re-fared (possibly screw drive or something).

OK, I thought they would be using hydraulic actuators.

Getting leverage from an actuator, down from the spat, through the "boot" (part of the foil assembly), and to the foil sounds complicated.

I would have guessed that hydraulic line connections would perhaps be in the spat area.

But we may never know!

 

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11 minutes ago, The Advocate said:

I would have thought the sensors would be further upstream.

Guessing as always, but they may have had pressure sensors on the foil wings? Would be very useful for the designers to get data on when the foil was approaching - or lower than - the water vapour pressure, resulting in cavitation.

Possibly one for the actuator(s) as well, to ensure they had correct pressure there.

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Sensors I think go down all the way out along the wing span. 

I'm not certain what ETNZ used in the end, as with the last set of foils they had distinctly split flaps rather than the connecting piece which was part of the control system. 

However... if you want to use only one actuator to control two control surfaces (each flap counts as a single control surface), then it has to be done electronically. 

Quote

22.7 A hydraulic actuator within an HCC may only be mechanically connected to one control surface.

24.2 Only the following electric actuators permitted within an ECC:
(d) actuators used to rotate or twist the foil flaps;

 

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5 minutes ago, MaxHugen said:

Guessing as always, but they may have had pressure sensors on the foil wings? Would be very useful for the designers to get data on when the foil was approaching - or lower than - the water vapour pressure, resulting in cavitation.

Possibly one for the actuator(s) as well, to ensure they had correct pressure there.

Couldn't they be in the boat though?

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26 minutes ago, The Advocate said:

Couldn't they be in the boat though?

No, the sensors would have to be at the location of interest, although they send the signals to equipment in the boat.

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34 minutes ago, The Advocate said:

Why? 

I'm not sure we're on the same page. How would you measure, say, local pressure at a foil wing, if it's not at the foil wing?

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38 minutes ago, The Advocate said:

At the pump end.

OK, you're talking about the hydraulic pressure for the flaps, sure, that would be up in the boat.

I was referring to the water pressure over the foil wings. :lol:

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You talking at hydraulic pressure versus surface pressure?

I think they will have sensors for flap rotation a several points along the foil. Then probably some fibre optics giving wing deflection. 

Nathan said in that interview about measuring when the load was zero, to raise the foil. I guess you could use pressure on either surface or the deflection of the span... but probably just a load cell within the arm would be the most direct way. 

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29 minutes ago, MaxHugen said:

OK, you're talking about the hydraulic pressure for the flaps, sure, that would be up in the boat.

I was referring to the water pressure over the foil wings. :lol:

I doubt they measure that during racing.

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31 minutes ago, Mozzy Sails said:

You talking at hydraulic pressure versus surface pressure?

I think they will have sensors for flap rotation a several points along the foil. Then probably some fibre optics giving wing deflection. 

Nathan said in that interview about measuring when the load was zero, to raise the foil. I guess you could use pressure on either surface or the deflection of the span... but probably just a load cell within the arm would be the most direct way. 

Was unclear what Max was referring to initially.

Why would they measure deflection during racing? Testing possibly.

Which Nathan? If it is the parameter I think is being referred to, that would also be measured inside the boat.

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41 minutes ago, The Advocate said:
1 hour ago, MaxHugen said:

OK, you're talking about the hydraulic pressure for the flaps, sure, that would be up in the boat.

I was referring to the water pressure over the foil wings. :lol:

I doubt they measure that during racing.

Actually, we need to be less obscure with what we are discussing to add value to this discussion.

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1 hour ago, The Advocate said:

Was unclear what Max was referring to initially.

Why would they measure deflection during racing? Testing possibly.

Which Nathan? If it is the parameter I think is being referred to, that would also be measured inside the boat.

I'm not sure what you would do with deflection along the wing during racing. But, I think it could be very useful for post sailing analysis. And if they're using fibre optics or something similar then it will be baked in to the foil. They're so light and low volume that I can't imagine you'd gain anything from having them be removable (even if it could be done non-destructively). 

Nathan Outteridge in his interview on PlanetSail. He was talking about making sure the foil was neutral (i.e no lifts or sucking down) before trying to raise it, to make a smooth lift. 

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12 hours ago, MaxHugen said:

Rhino at USD 995 is way way beyond my budget, but I'll scout around for an alternative CAD app that can maybe do the same.  Thanks for outlining the procedure.  :)

The important thing is not Rhino itself, but the workflow.  I think just about any CAD package would have similar capabilities.  You might look into Fusion360 fro Autodesk.  It has a free version.

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10 minutes ago, Basiliscus said:

The important thing is not Rhino itself, but the workflow.  I think just about any CAD package would have similar capabilities.  You might look into Fusion360 fro Autodesk.  It has a free version.

Thanks, trying to do just that with FreeCAD, but it's a bit of a struggle at the moment. I shall persevere. :)

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6 hours ago, Mozzy Sails said:

I'm not sure what you would do with deflection along the wing during racing. But, I think it could be very useful for post sailing analysis. And if they're using fibre optics or something similar then it will be baked in to the foil. They're so light and low volume that I can't imagine you'd gain anything from having them be removable (even if it could be done non-destructively). 

Nathan Outteridge in his interview on PlanetSail. He was talking about making sure the foil was neutral (i.e no lifts or sucking down) before trying to raise it, to make a smooth lift. 

Yes they could defiantly have some thin film tech or something like that I guess..

Sounds like NO is taking about tacking.

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Hey @MaxHugen and @Basiliscus , check out ImageJ - a free image analysis software developed at the NIH. It has a line graph analysis tool that does exactly what you want. Long long time ago, I used it to digitalize paper recordings from physiology experiments. Just tested it in the current version and it works like a charm.

Converts a line drawing straight into a csv file or copy to excel. You will have to do the top and the bottom separately, because it's looking for a line graph, you can't have two Y values for the same X.

Download Fiji (Fiji is just ImageJ - literally :D), it has all the plugins already packaged in the download file:

https://imagej.net/Fiji/Downloads

Follow instructions under Analyze Line Graph: https://imagej.nih.gov/ij/docs/menus/analyze.html#graph

 

 

 

 

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This thread is amazing!
While I don't contribute I still read avidly, not always following, until maybe a few days and bouncing around I catch up with the over all ideas.

Thank you all for your contributions!

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3 hours ago, erdb said:

Hey @MaxHugen and @Basiliscus , check out ImageJ - a free image analysis software developed at the NIH. ...

Thanks for the tip - I installed Fiji.  The thresholding tool is very powerful.  However, I think it may be expecting a cleaner image than is often the case.  This drawing is not AC or hydrofoil related, but it is typical of the kinds of things I'd like to convert to CAD.  I'll play around with it some more, and actually import something into CAD to see how that works.

SM55X_ SCALE_WING_CENTER_COCKPIT_DETAIL.jpg

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5 hours ago, erdb said:

Hey @MaxHugen and @Basiliscus , check out ImageJ - a free image analysis software developed at the NIH. It has a line graph analysis tool that does exactly what you want. Long long time ago, I used it to digitalize paper recordings from physiology experiments. Just tested it in the current version and it works like a charm.

Converts a line drawing straight into a csv file or copy to excel. You will have to do the top and the bottom separately, because it's looking for a line graph, you can't have two Y values for the same X.

Download Fiji (Fiji is just ImageJ - literally :D), it has all the plugins already packaged in the download file:

https://imagej.net/Fiji/Downloads

Follow instructions under Analyze Line Graph: https://imagej.nih.gov/ij/docs/menus/analyze.html#graph

Thanks erdb, I'll check it out!

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2 hours ago, Basiliscus said:

Thanks for the tip - I installed Fiji.  The thresholding tool is very powerful.  However, I think it may be expecting a cleaner image than is often the case.  This drawing is not AC or hydrofoil related, but it is typical of the kinds of things I'd like to convert to CAD.  I'll play around with it some more, and actually import something into CAD to see how that works.

SM55X_ SCALE_WING_CENTER_COCKPIT_DETAIL.jpg

That's a pretty hefty looking profile, what is it for?

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2 hours ago, Basiliscus said:

SM.55.  I'm working on the design of a 1/12 scale model.

Cool! First searches produced "sand mixers"... :lol:

image.png.835b45a83428687bd9791cb36ab763b1.png

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9 hours ago, Kiwing said:

This thread is amazing!
While I don't contribute I still read avidly, not always following, until maybe a few days and bouncing around I catch up with the over all ideas.

Thank you all for your contributions!

I totally agree. Thanks guys!

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13 hours ago, Basiliscus said:

SM.55.  I'm working on the design of a 1/12 scale model.

You might then want to check against the real thing - in the Italian Air Force’s excellent museum in Vigna di Valle, near Rome

I saw the only other surviving plane in the Bandeirantes Museum, São Paulo

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16 hours ago, Basiliscus said:

Thanks for the tip - I installed Fiji.  The thresholding tool is very powerful.  However, I think it may be expecting a cleaner image than is often the case.  This drawing is not AC or hydrofoil related, but it is typical of the kinds of things I'd like to convert to CAD.  I'll play around with it some more, and actually import something into CAD to see how that works.

SM55X_ SCALE_WING_CENTER_COCKPIT_DETAIL.jpg

I created a foil profile from this img in XFLR5, although I did not tidy it up using inverse design:

SM.55.dat

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18 hours ago, Basiliscus said:

Thanks for the tip - I installed Fiji.  The thresholding tool is very powerful.  However, I think it may be expecting a cleaner image than is often the case.  This drawing is not AC or hydrofoil related, but it is typical of the kinds of things I'd like to convert to CAD.  I'll play around with it some more, and actually import something into CAD to see how that works.

SM55X_ SCALE_WING_CENTER_COCKPIT_DETAIL.jpg

There is another plugin: https://lukemiller.org/index.php/2011/09/digitizing-data-from-old-figures-with-imagej/

With this, you have to click on data points you want to save, so you're back to manual drawing, but the nice thing is you can calibrate your image to export coordinates in the 0 - 1 range right away.

Cool project BTW!

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Apologies for a hopefully brief interruption, but since this great thread is so active I will post the Q here: 

How do you navigate to Private Messages, in this new format please? My ‘theme’
 

4D0B9C12-6531-4DCF-B20D-DFF04DF63C3A.thumb.jpeg.ad201ae01a5fce80e0da166c180c7681.jpeg

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24 minutes ago, Stingray~ said:

Apologies for a hopefully brief interruption, but since this great thread is so active I will post the Q here: 

How do you navigate to Private Messages, in this new format please? My ‘theme’
 

4D0B9C12-6531-4DCF-B20D-DFF04DF63C3A.thumb.jpeg.ad201ae01a5fce80e0da166c180c7681.jpeg

I get the same on my android phone and haven't been able to find away.

Strangely it works on my android tablet as well as my windblows laptop.

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31 minutes ago, Stingray~ said:

Apologies for a hopefully brief interruption, but since this great thread is so active I will post the Q here: 

How do you navigate to Private Messages, in this new format please? My ‘theme’
 

4D0B9C12-6531-4DCF-B20D-DFF04DF63C3A.thumb.jpeg.ad201ae01a5fce80e0da166c180c7681.jpeg

 

6 minutes ago, jaysper said:

I get the same on my android phone and haven't been able to find away.

Strangely it works on my android tablet as well as my windblows laptop.

Scroll to the very bottom of the page, click "Themes", choose "IPS default", scroll back to the top, click the sandwich and look at the right upper corner. There you'll find the envelope.

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7 minutes ago, Rennmaus said:

 

Scroll to the very bottom of the page, click "Themes", choose "IPS default", scroll back to the top, click the sandwich and look at the right upper corner. There you'll find the envelope.

Awesome! Works perfectly.

Thanks Rennie!

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1 hour ago, jaysper said:

Awesome! Works perfectly.

Thanks Rennie!

+1! Glad to have found the PM, from one of the great denizens in this thread. Thanks, Rennie. 

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7 hours ago, Xlot said:

You might then want to check against the real thing - in the Italian Air Force’s excellent museum in Vigna di Valle, near Rome

I saw the only other surviving plane in the Bandeirantes Museum, São Paulo

Yes, I found a good set of photos from the Brazilian plane taken when it was undergoing restoration.  I thought it was the only intact surviving one.  It's an M model and I'm going with the X model, but lots of good detail.

That's probably enough of a digression from the AC.  There's another forum where I'll be logging the build when I get going on it.

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7 hours ago, MaxHugen said:

I created a foil profile from this img in XFLR5, although I did not tidy it up using inverse design:

SM.55.dat 5.38 kB · 1 download

Thanks.  I'll take a look at it.  I've already extracted some section shapes from that and other drawings, and slightly modified them to be suitable for model Reynolds numbers.

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5 hours ago, erdb said:

There is another plugin: https://lukemiller.org/index.php/2011/09/digitizing-data-from-old-figures-with-imagej/

With this, you have to click on data points you want to save, so you're back to manual drawing, but the nice thing is you can calibrate your image to export coordinates in the 0 - 1 range right away.

Cool project BTW!

Thanks.  It's sounding like ImageJ could be another hobby all in itself.

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4 hours ago, Rennmaus said:

 

Scroll to the very bottom of the page, click "Themes", choose "IPS default", scroll back to the top, click the sandwich and look at the right upper corner. There you'll find the envelope.

Thanks Renni! 

Thought it was me going senile, after searching every corner of the forum for that link to PMs.  :P

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From Max, sequential logic related to small T- foils:

- T-foils work only if they are small

- but then to facilitate take-off, you need to give down rudder for a moment

- the bow goes down, and take-off happens on the rebound

- as a consequence, bow volumes are not ideal for other aspects

 

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1 hour ago, Xlot said:

From Max, sequential logic related to small T- foils:

- T-foils work only if they are small

- but then to facilitate take-off, you need to give down rudder for a moment

- the bow goes down, and take-off happens on the rebound

- as a consequence, bow volumes are not ideal for other aspects

 

Interesting, except there was an excellent side-on video of NZ's take-off, which clearly showed that they maintained a very level pitch throughout  the maneuver. It would seem that the foil AoI of 2° (my estimate) plus flap angle were quite sufficient to get NZ foiling.

Note that at 0° pitch, NZ's canoe shaped bustle presents a minimal wetted area, and with less total drag, would enable NZ to get onto the foils no slower than any other team. IMO.

As to why "T-foils work only if they are small"...  that claim has me stumped. :unsure:

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47 minutes ago, MaxHugen said:

As to why "T-foils work only if they are small"...  that claim has me stumped. :unsure:

I think it's reversed. If you want small foils, you have to go with T foils. 

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So what would happen if for the next AC the boat was entirely open? No class rules are all!

Would the boats that turned up all be pretty much AC75 anyway? 

There are boats that would beat them in a straight line, but not around a W/L course and not even they have to match race and win starts.

I'm not sure a bigger boat would go much faster as these boats are at cavitation limits anyway.

The costs would probably astronomical, but the results would be interesting.

 

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5 minutes ago, sfigone said:

Would the boats that turned up all be pretty much AC75 anyway? 

I doubt that.

  • Firstly the sail plan would become open slather.
  • You would have to assume that at least one of the teams would consider different foils for up and down wind - and yes that would mean some mechanism for switching which foil gets submerged.
  • The grinders would be replaced by batteries or an engine.
  • Pumped ballast would become a consideration.
  • The foil trim would be fully automated with a complete set of sensors to optimise this.
  • Plus  whole bunch of other crap that I can't think of right now.

 

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On 3/24/2021 at 9:38 AM, MaxHugen said:

Do you know of any way to convert SVG to coords, or a different spline-based app that can export to x-y coords?

There is litle program caled CONCORD. Stands for Coordinate- convertter, it is tool for airfoils. If Ibremember it can do dxf, this shoud be close enough. On javafoil website.

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1 hour ago, gigi said:

There is litle program caled CONCORD. Stands for Coordinate- convertter, it is tool for airfoils. If Ibremember it can do dxf, this shoud be close enough. On javafoil website.

Thanks Gigi. 

This appeared to be a very handy tool:
image.png.abcb04cd43c85ee2ff7dd0448b524b27.png

However, it was written a couple of decades ago, and it can't read newer CAD file formats such as AutoCAD R12 or R14. :(   These are the options I have of saving an Inkscape SVG file as a DXF file, from which I'd hoped to convert to a 2 column DAT file.
image.png.a3cbe6b9f02edf52ea8648932b0a110e.png

Still, it might be useful for some other members here?

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One of the issues with the current design is their rather poor or have tricky performance in the marginal light conditions.

I think they could have an out board only foil above the current foil that would lift the boat at a lower speed  say at 10knts once the wetted area declines and the speed builds it would rise above the surface sort of a ladder foil from old.

the benefit would be smaller main foils possibly and much less foil fall of angst. The light wind sailing was great but marred by some wind holes that reversed entire races in what was a bit silly at times.

ETNZ had smaller foils it was an advantage at bigger speeds probably optimized to 30knts if they were 10% smaller and the outboard foil was say 50% of the full area but built for 15knts for max lift these boats would engage more in the starter area and would be game to go slow as a tactic. luffing, or daring a hook it would be fun and light winds with patchy air did extract a good sailing race.     

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46 minutes ago, coercivity said:

One of the issues with the current design is their rather poor or have tricky performance in the marginal light conditions.

I think they could have an out board only foil above the current foil that would lift the boat at a lower speed  say at 10knts once the wetted area declines and the speed builds it would rise above the surface sort of a ladder foil from old.

the benefit would be smaller main foils possibly and much less foil fall of angst. The light wind sailing was great but marred by some wind holes that reversed entire races in what was a bit silly at times.

ETNZ had smaller foils it was an advantage at bigger speeds probably optimized to 30knts if they were 10% smaller and the outboard foil was say 50% of the full area but built for 15knts for max lift these boats would engage more in the starter area and would be game to go slow as a tactic. luffing, or daring a hook it would be fun and light winds with patchy air did extract a good sailing race.     

I was talking to a Bell at a pre COVID wedding ( yes, that Bell family, as in Alexander Graham ) who was intrigued with ladder foils, to the point of designing and having some built and tested, and while they did offer lift in lower wind speeds, he felt drag was a penalty, kind of like Willawaw experienced in lighter wind.  Whether that regime lift was more than Archimedes regime hull drag, friction and wave, he wasn’t sure.  Surface tension entered into things, IIRR.  We got into that during the reception, so you’ll forgive a suspect recollection. :)

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On 3/15/2021 at 12:18 AM, Tornado-Cat said:

TNZ

-          My first meeting with TNZ was in 2009

-          I begain to work in 2010

-          I have aneye on everyting on the boat but works part time because busy on other projects

-          I give ideas but it’s a lot of work, you have to develop it each idea

-          I like a small team because it’s efficient, we are even too many, lots of people coding, too many, we have to keep a global vision

AC75

-          One day day Ray Davis asks me to meet Howard Spencer, willing to get a fun 40 ft.

-          I design a foiling mono

-          Ray says that the keel is too much

-          I tell him it’s possible, however we need stability

-          I remember that a french architect, Martin Defline has made two queels boats who are pretty efficient, so we can do the same thing with ballast at the end of the foil

-          It’s counter intuitive to put weight where we want a lift but calcules show it is 50% more efficient that with the keel for the same mass.

-          The project doesn’t work as too expensive

-          The Italians want a big mono for AC36, we could have a had a smaller boat for economic reasons

-          Ray Davies puts my drawing on the table, everybody laugh. He tells us: I give you one month to test the concept to test If it works in a simulator. I was not there, I did not test, Bobby tested the design and they said it was a fun concept and it works

-          They tried other concepts but came back to the initial one

 

AC75 rule

-          I was willing two rudder foils for better stability to avoid diagonal heel instability like the hydrotère.

-          I was against it but we went to one rudder for a good reason: to avoid cutting a crew falling in the water. That is also why the rules prevent going on the bow.

-          I did not write the rule, Dan Bernasconi did it, I gave my advices.

-          We chose a close rule to avoid mistakes, it took us a year

-          We were very reassured to see that the british model worked, simulation works but is not always reassuring.

-          We surely took some advance compared to the other teams but I don’t think it was so much

-          Once I chose a concept I like to push it to the end.

-          We got symetric foils at the end only in order to learn as much as possible

-          The bulb at the end of the foil arm is just to put ballast, it has nothing to do with hydro but with the rule

 

Our AC75

-          We are given a rule that I hate, the inertial stability in the harbour that imposes a wide flotation beam

-          I understand it but it was not required with the ballasted foils in the water, we did not need that. 10’17

-          I understood that it was obvious that we have to make a central tube like a trimaran hull and a wide ass for the rule and stability, I don’t think other teams understood it right away: narrow hull and wide as far on the back as possible.

-          So we have a narrow hull in the front like a trimaran and a wide ass for static stability in the harbour.

-          Not a big evolution between B1 and B2, B2 is even more like a multi

-          We want a boat easy to foil that lift the stern first and get early on the foils for lower drag asap

-          The brits were capsizing when bearing away as they could not get enough lift from the foil vs the pressure. They were afraid of the transition and they were right to have a first boat with more stability.

-          B1 was an hydro dynamic concept, B2 an aero + hydro

The foil

-          The dihedral is more equlibrated and does not require a big “shaft” that maintain the foil and which creates drag

-          On the other hand a flat design is simpler and has lower drag. Both concepts are good.

B  

I did not have time to finish the translation, here it is, really worth reading it.

Link: https://voilesetvoiliers.ouest-france.fr/regate/coupe-de-l-america/america-s-cup-guillaume-verdier-du-vendee-globe-a-la-coupe-de-l-america-sur-tous-les-fronts-16505d9a-7daf-11eb-a530-8257a05e6295?fbclid=IwAR1NxsAj3wAuWdzn6_P7iVTxshZyq76ZeZcZfnogKPj0O9F0JBzZQrROne8

What the secret of TNZ success

-          When I begun in 2010 what really asthonished me was the horizontal organization, people can speak, there is no real boss. It has advantages but it can be the mess sometimes too, nobody is responsible of anything and everybody responsible for everyting. It works with a small structure, it is not a pyramidal but horizontal structure.

-          The is no restriction to possibility to speak, sailors are integrated to the design team. They often take the decision. They are part of the design meetings.

-          When we decide the piece to design we give ourself a time table and we don’t come back on our decision, we finish the construction as decided. In other places people sometimes come back on their decisions and want modification before finish which causes further delays, not here.

-          We don’t subcontract the construction of the boat, it’s integrated in the team to we control it directly

 

The simulator

-          The simulator took less place that in the previous edition

-          We did less design on the simulator than the last time, we did more fondamental design

-          We modified the simulator

-          Some speak about artificial intelligence, in fact it’s not ture it’s everything but intelligent and very artificial. However we have many persons working on scripts in order to automatize the calcules

-          We use the artificial intelligence for foil profile. We give an objective of lift on a section of the foil, or an objective of ratio of lift vs drag + a few variables. We let the computer work all night, it will draw a part of the section. Then the computer tells what section is best when we give it a criteria. So in fact the machine does  what we ask it but if we think well ourself we can do the same. We have to think and not let the machines do stupidly any objective or it can be very dangerous

How do you find your ideas?

-          We learn the different knoledge in different fields like paragliders who need loft of lift or wing profile of aerobatic plane who need a lot of tolerance to the requirements.

-          We mix all that, we have to look at what is done in other fields of aerodynamics. We are lucky as we can find everything on the net now, NASA studies, European Space Agency.

-          Everything is here and for free. When I remember that when I began to work I had to go and try to buy some book in bookstores. We can even fin Excel sheets with lift/drag, cavitation calcules. All students work on that in all universities

Is there a Verdier method ?

-          No, I work from home, we are a group of architect working from home, the lock down had had no impact. I don’t like working in an office with people around, I prefer working alone.

Do you have a way to approach a project ?

-          Yes, but I can’t tell it is the good one. When I am asked to work on a design I like to work on the full project and I have a feedback loop very quickly, I draw my design very quickly. In some other methods differents persons work on different bricks of the pyramid and it takes months. For me I draw the AC boat in 3 weeks, I judge it, I see the caveouts and do another loop immediately. I want to go quickly otherwise we spend too much time on a detail and another, and another, for me I want to work on the global vision and refine it at each loop.

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1 hour ago, coercivity said:

One of the issues with the current design is their rather poor or have tricky performance in the marginal light conditions.

I think they could have an out board only foil above the current foil that would lift the boat at a lower speed  say at 10knts once the wetted area declines and the speed builds it would rise above the surface sort of a ladder foil from old.

the benefit would be smaller main foils possibly and much less foil fall of angst. The light wind sailing was great but marred by some wind holes that reversed entire races in what was a bit silly at times.

ETNZ had smaller foils it was an advantage at bigger speeds probably optimized to 30knts if they were 10% smaller and the outboard foil was say 50% of the full area but built for 15knts for max lift these boats would engage more in the starter area and would be game to go slow as a tactic. luffing, or daring a hook it would be fun and light winds with patchy air did extract a good sailing race.     

You may have noticed that NZ had no more issue getting onto the foil than other teams, despite their smaller foils. They had a slightly higher AoI, around 2°, compared to ~1.5 for Ineos and LR (IMO). No doubt they had to use more flap angle too.

The problem is that more lift produces more drag. One part of the equation is acceleration, and the inertia from a mass of 7.8t plays a significant part.

That's why a Moth can get on the foils at a much lower take-off speed.

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yes but what about getting on and up quicker so you can slow the team behind into the entry or know that in a light patch you can stay up.

they were very careful they had the the smallest jib possible for the high speed runs so the slow stuff was tricky

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I think there were no teams that would not have welcomed an extra 100% foil lift at takeoff, all the racing would have been different.

A high AoA smaller but upper foil would have allowed a much harsher approach to racing.

We want aggressive competition not this pansy can't do a hook to risky in the lee BS we want passing upwind and being mowed down again downwind wild mode differences.  

We had a glimpse I want more.

Sail changing, brood reaches at 50knts, dummy tacks all that stuff and more. To much paint drying for masses.   

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