Nodrog

Too much data ? Having a guess at Polars

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1 hour ago, Enzedel92 said:

Someone crunch the numbers and tell who will win between AR and ETNZ??

Which numbers do you figure can predict 'who will win between AR and ETNZ??'

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1 hour ago, ~Stingray~ said:

Which numbers do you figure can predict 'who will win between AR and ETNZ??'

I know there are some statisticians on here that can read the tea leaves.  

Are you familiar with Monte Carlo simulation?  Some a little brighter than me chime in

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2 hours ago, Enzedel92 said:

Someone crunch the numbers and tell who will win between AR and ETNZ??

Crunch crunch Crunch!  ETNZ! :D

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1 hour ago, Enzedel92 said:

I know there are some statisticians on here that can read the tea leaves.  

Are you familiar with Monte Carlo simulation?  Some a little brighter than me chime in

If 2 boats competing each other would have exactly the same level of engineering, design, construction and sailing skills, the one with slightly smaller foils in any given say would have slightly faster speed on most of the days and more substantially slower in a very few days. Since AC and challenger final are both point races, time differences at the finish are irrelevant, and the one with those smaller foils would end up as a winner.

In real life there are plenty of differences and monte carlo method would only lead to results if those were known. Since they are not, it  would be the old garbage in garbage out case if monte carlo method would be used.

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I have combined all data from all racing days. 

First, polar speed graphs over all wind ranges:

lUDl8w6.jpg

hvef657.jpg

OkODBYj.jpg

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Gorgeous!!!

Here's my little contribution, for today's races. Have not yet checked how closely it matches the posted stats but will in the next day or two, am sure it is very close.

RACES_BOATS_LEGS_17061003.xlsx

I have data for all Semi Finals, and today's 3 Finals, including boat_separation etc.

edit, official stats:

CFR1L1.PNG.5035012cc831a975135fd82571d49887.PNGCGR1L2.PNG.ee3c3a46082713d31858a1138ee10e25.PNG

 

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8 minutes ago, ~Stingray~ said:

Gorgeous!!!

 

How do you figure out start and end point for legs?

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11 minutes ago, dorox said:

How do you figure out start and end point for legs?

I could, but didn't. If you are looking at Distance_Sailed, I calculate that by the distance they actually sailed between mark roundings. It is a sum of the distances sailed in .2 sec interval. Each .2 sec interval's value is on the order of magnitude of 3m (or 15m/sec or ~30 knots)

 

 

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Next up, upwind performance. This is represented as VMG vs wind speed. Color shows the angle to the wind. Generally, VMG grows with growing wind speed, before hitting a limit of appr. 23-25 kn. It seems like they can go even faster upwind, but something limits the efficiency (air drag or cautiousness?). With higher pointing angle the VMG is higher. So for these boats the optimal sailing angle would be in the range of 30-40 deg. for high wind speed and 50-55 in low winds.

8VYTbA9.jpg

0ZCjKFw.jpg

kPyPt8h.jpg

Here I compare VMG of these teams by overlaying the VMG plots. ART is slower than ETNZ and USA in low to med wind range (5-16 kn), but faster than ETNZ in high wind range. 

73sU0Gc.jpg

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Downwind graphs:

Here the same principle as with the upwind performance: high wind = lower, faster; low wind=higher, slower. Interesting that VMG rises linearly in the region of the 0-35 kn, and then slows down to hit the limit of 35-40 kn. I think this should be a cavitation limit for the foils. The key difference between the teams is how early (in terms of wind speed) they hit this cavitation barrier. For NZL and USA it is appr 12-14 kn of windspeed, while for SWE it is 18-20 kn which means they are slower downwind in moderate and light wind.

dyTP9mm.jpg

woH1wcS.jpg

bcOTiiR.jpg

Comparison of all teams: USA equal or slightly slower (not enough data) than NZL, SWE is the slowest.

pAgeFJ5.jpg

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9 minutes ago, dorox said:

What else can we make out of this data?

 

Who sails in favored wind the most?

Number of tacks and gybes?

Best starts (delta speed across the line, delta across the line, etc)?

Splits allowed/created when it works/doesn't ?

 

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Your very-impressive charts, what all races do they cover? All Semi Finals plus today? Plus all RR's?

Given that boats have improved, would like to see the same but for today's 3 races only, maybe excluding AR's dots after the helm went AWOL.

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Thanks for all the great polar efforts!  Here is a suggestion for improving the analysis for a better comparison of boat performance:

How about normalizing the polars by dividing boat speed by TWS.  Probably separate into 2 ranges of light air (6-13) and medium air (>13-24){which will most likely only cover >13-20}.  Hence, each boat would have 2 colors on the polar.  Then overlay 2 boats for comparison, like ETNZ and OTUSA, or ETNZ and AR.

The normalization should reduce the magnitude noise for a better comparison.

Since the boats keep improving, use only the most recent while-racing data and clearly label what data is included.

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Looking forward to more gorgeous Polars, taken from today.

Dorox, I will auto-import and auto-crunch the latest dataset in append-mode append after it is available and will let you know the new big Zip is up on Google Drive - in case you find that format to be helpful... But later today since it's not there yet and the sun is out :)

 

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10382230.jpg

Before you get too excited, its a couple years old..... it is foiling in 8 - 10 kts, but not an AC yacht ;)... Now are they quicker than this thing... probably not in the light... dunno

 

 

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Thanks Dorox!  Excellent graphics. Those really tell the tale.  Now ETNZ strategy of stay clean at the start and simply grind down AR with boat speed makes sense.  This could change every day depending on how they set-up the boats (foil selection, rudder foil setting, etc.).  This showed they were closer to equal in the upper wind range on Sat.

Well done.

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Today's Race Data is up but still not for those great races on Sunday. Have emailed Abby E to let her know.

Will download hopefully both later today and will add some *_N computed columns (N for North, or for Normalized to North) to make Polar plots across races simpler.

 

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Dorox, fantastic work, knew someone would be able to do a proper job of it. 

Am hoping to have a chance today to compare ETNZ's VMGs vs similar wind speeds earlier in the comp. Pretty sure we're going to see a significant improvement.

Can someone remind me which data set day had ETNZ with the big bat foils in around 10knts?

 

 

 

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2 hours ago, ~Stingray~ said:

Today's Race Data is up but still not for those great races on Sunday. Have emailed Abby E to let her know.

Will download hopefully both later today and will add some *_N computed columns (N for North, or for Normalized to North) to make Polar plots across races simpler.

 

Sunday's is (finally..) up now too, will auto download-crunch and upload my format soon for Dorox and anyone else who PM's me a google-drive enabled email address to share it to.

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Thanks Stingray. 

Did oracle use only one set of foils over challenger series? It would be interesting now to compare their performance to the kiwis. 

Nodrog: it was yesterday and ACEA didn't bother to upload that data yet.

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If you can figure out those OR races you want added, am happy to do it. Currently I have just the Semi's and Finals loaded, after cleaning.

Would be fun to add descriptive 'foil' attributes to the data but it'd be hard to figure a decent value by Race date since even tips seem to vary a lot. 

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Today, in 11 knots of breeze [yTWS, averaged over 3 seconds], orange line, they were consistent in getting 16.5 to 17knts of VMG. The peaks here to the right, as supposed to the longer distributions seen prior indicates to me they were sailing in their groove alot of the time, maxing VMG, rather than a wider range we've seen before. 

I've a file of all the NZL data from the Qualifiers, when they had a variety of set ups, and 15.5 to 16knt VMGs were pretty good [ edit: in 11knts yTWS, averaged] but for many of those they would have been sailing in a lull with a heavier air set-up. 17's were still achieved, and much higher through tacks etc. Need to find a data file for when they had a similar set up to today. 

 

 

ETNZ VMGs 12_6.JPG

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30 minutes ago, Nodrog said:

Today, in 11 knots of breeze [yTWS, averaged over 3 seconds], orange line, they were consistent in getting 16.5 to 17knts of VMG. The peaks here to the right, as supposed to the longer distributions seen prior indicates to me they were sailing in their groove alot of the time, maxing VMG, rather than a wider range we've seen before. 

I've a file of all the NZL data from the Qualifiers, when they had a variety of set ups, and 15.5 to 16knt VMGs were pretty good [ edit: in 11knts yTWS, averaged] but for many of those they would have been sailing in a lull with a heavier air set-up. 17's were still achieved, and much higher through tacks etc. Need to find a data file for when they had a similar set up to today. 

 

 

ETNZ VMGs 12_6.JPG

Wouldn't a polar diagram be a better way of presenting this?  Thankyou to both dorox and nodroG for doing the analysis.

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26 minutes ago, Foyle said:

Wouldn't a polar diagram be a better way of presenting this?  Thankyou to both dorox and nodroG for doing the analysis.

Absolutely would, but I can only get so much out of Excel!

The issue I have is the data is really noisy, and is delivered at differing frequencies, so polars end up with a lot of scattered dots, not the firm 'target line' that we'd like to see.

I don't have the resource to get a firm 'target' boat speed ( i think a 95th percentile?) at every yTWA and yTWS combination. Drawing a line around the maximum ever achieved at each TWS/TWA combo I don't think gives realistic numbers, that would just be a record of all the errors the instruments have logged during racing. 

If someone has access to R / matlab / SQL / real computing.... then a matrix of TWA and TWS, averaged over say 5 seconds (?), with the mean / median / Std Dev in each 'box' would probably help? But not sure the boats are sailing in a steady state long enough for us to get decent averages?

I've taken the approach that VMG is what matters, regardless of the TWA to achieve it, so try to show the highest consistently achieved VMG at different wind speeds. 

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I'm actually using MATLAB. The issue with polars is that boats are really sailing only upwind or downwind. And for both modes I would expect the sailors to go for best VMG mode most of the time. So the best approach is to plot VMG in one way or another.

However polars are very illustrative especially for casual public.

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Today's analysis.

NZL is much faster upwind: average VMG of 14.8 against 13.4 of SWE. This difference of 1.4 kn equals to 200 m gain over 5 min of upwind sailing - pretty much what we saw today.

12JUN.png

12JUNSE.png

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Nice work with the graphics!  Very interesting. 

I'm surprised the sailing efficiency has so much variation.  Maybe that comes from the fact that TWS changes take a while to show up in VMG.  A simple graph of those versus time might identify the significance of this delay effect  Unfortunately the amount of delay would be related to the amount of TWS change.  Perhaps it would be practical to compare the VMG peaks to the prior TWS peak.  Similarly VMG valleys could be compared to prior TWS valleys.

Maybe it would be easier to just average TWS and VMG over a typical delay time and offset the efficiency calculation by that delay time.  For example, if a typical delay time was found to be 4 seconds, then average TWS and VMG over 4 seconds and calculate efficiency by VMG(i+1)/TWS(i).

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1 hour ago, ThrillSeeker said:

Nice work with the graphics!  Very interesting. 

I'm surprised the sailing efficiency has so much variation.  Maybe that comes from the fact that TWS changes take a while to show up in VMG.  A simple graph of those versus time might identify the significance of this delay effect  Unfortunately the amount of delay would be related to the amount of TWS change.  Perhaps it would be practical to compare the VMG peaks to the prior TWS peak.  Similarly VMG valleys could be compared to prior TWS valleys.

Maybe it would be easier to just average TWS and VMG over a typical delay time and offset the efficiency calculation by that delay time.  For example, if a typical delay time was found to be 4 seconds, then average TWS and VMG over 4 seconds and calculate efficiency by VMG(i+1)/TWS(i).

The dots I plotted are at "steady state" sailing. It is defined as change of average SOG over 10 s is  less than 0.1kn and change of a COG over 10s is less than 0.1deg.

Look at the polars - the course is changing within 20 deg when going upwind: sometimes they sail lower/higher, or they might put more or less pressure on the boat by adjusting the wing (they dont need to go 100% all the time, just enough to beat SWE)- this affects VMG.

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What I found interesting is the top limit they hit at high wind speed: appr. 15kn VMG or 25 kn SOG. I think this should be cavitation speed in upwind mode.

Keep in mind that cavitation causes damage to appendages - they do not want to sail 100% unless it is their last cup race :rolleyes:

12JUNSE1.png

ETNZup.png

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I don`t know exactly, but my guess is that because there is larger heeling moment from the wing. This heeling is balanced by higher lift on the foil when compared to downwind. And higher lift equals to bigger angle of attack which leads to lower pressure around the foil.

In simplier terms, for downwind foil is used to support only weight of the boat. For upwind it supports weight plus increases righting moment which requires higher lift.

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25 minutes ago, southseasbill said:

Why would cavitation happen at a lower speed upwind vs downwind?

Not sure if its a relevant comparison, but there are plenty of guys I used to windsurf with, who seemed incapable of sailing a board without cavitating the fin. This seemed to happen more often upwind than down. You could see them putting too much pressure on the fin.

For me, keeping the windward rail of the board in the water pretty much stopped cavitation. Further keeping pressure and weight forward off the fin also decreased cavitation. This seemed simple enough, but others didn't get it. Definitely happened less downwind when you were more "over" the fin, but when it went, it went big :)

SO the answer to your question, may be there is more pressure.

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Foil loading, the reduction of it is one of the reasons why the foils are bigger/longer than most people would expect from a form drag point of view 

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would leeway resistance be responsible for higher foil loading? The boats seem not to be lo-riding depending on the vertical foil component solely to resist leeway this cycle.

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On 14.6.2017 at 0:47 PM, dorox said:

I don`t know exactly, but my guess is that because there is larger heeling moment from the wing. This heeling is balanced by higher lift on the foil when compared to downwind. And higher lift equals to bigger angle of attack which leads to lower pressure around the foil.

In simplier terms, for downwind foil is used to support only weight of the boat. For upwind it supports weight plus increases righting moment which requires higher lift.

Because the boat moves faster downwind, the boards are adjusted to decrease rake to prevent vertical lift increasing too much with increasing speed. The board pivot axis is close to the bottom of the hull, which means the horizontal part of the foil moves aft relative to the hull (and therefore also relative to center of gravity) making the boat trying to pitchpole. This is prevented by making rudder T-foils pull down more, or stopping them to lift upwards at the same time rake is reduced and boat speed increased. The result of that is the overall down force (=gravity + down force from rudder T-foils) is increased, and must be compensated by increase of upwards lift from the daggerfoils to prevent accelerating downwards. That means the boards are raked a bit less, but still the same direction to reduce angle of attack for downwind sailing. At the same time wingsail also have more forward drive and pitching moment during downwind sailing than upwind. That also requires more down pull from the rudders and more upwards lift from the daggerfoils, reducing the amount of rake change needed for daggerfoils in the first place, thus lessening the aftwards movement of center of pressure. There is definitely more vertical lift downwind than upwind (much more than just weight of the boat), but the angle of attack might still be higher upwind due to less speed when only comparing steady state conditions. All of that means cavitation limit for horizontal part of the foil is not very relevant during upwind sailing (the slowest point of sail), but on the reach is most certainly is.

If you are looking for reasons limiting top upwind VMG to the value it's currently maxing out, take a much closer look at air resistance, than what happens below waterline in steady state. Controlling flying altitude might also be quite relevant upwind to optimize performance. Too high and leeway increases and drag with it, too low and wetted area is too high again increasing drag.

Of course allowable righting moment, and thus level of power available is still critical, but pretty much the same for all the boats. There may also be significant differences in aerodynamic efficiency in dynamic situations between the boats.

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On 2017-6-12 at 2:09 AM, dorox said:

Yesterday's data:

10JUN 1.jpg

10JUN 2.jpg

10JUN 3.jpg

Dorox, your data was quoted on a Facebook feed I saw. Some insightful words I thought, essentially I think ETNZ have traded more drag on reaches for more righting moment, and hence higher VMG, upwind 

https://www.facebook.com/Ellway-Aero-Hydrodynamic-Designs-671685749655101/

 

Musings from the Americas Cup – why ENZ won the LV to become challenger.

The AC has provided some great racing and spectacles. Here are just a few thoughts on possible reasons why ENZ went through to face Oracle. 

The attached upwind polars of ENZ v Artemis (from Sailing Anarchy) show superior all-round performance of ENZ, especially in lighter winds. 

ENZ flight control
There has been much discussion on whether bikes provide greater power output or more or less windage. The biggest advantage (by far) is that by using bikes, the cyclor’s hands are free to do other tasks. The most important of which is flight control. Those of you who kitefoil or windfoil know just how many minute control inputs via your CofG are required to keep at the correct pitch and height above the water. In an AC boat, this control is made by altering the AOA of the front foil. On BAR for example, the control function was left to the helm. But on ENZ it is the task of the 3rd member from the stern. He is playing a ‘computer game’ matching his control output to an ‘artificial horizon’. This allows far more rapid control of the foil and much tighter control. In turn, this has allowed the boat to be flown higher out of the water (so less shaft drag), and to maintain better control in manoeuvres (especially tacks), when large control movements are needed to compensate for the rapid changes in speed and thrust.

ENZ hydraulic wing control
Unlike the other challengers, the wing trim appears to be hydraulically controlled rather than using a sheet via a winch. It appears that this allows more rapid and accurate wing trim in order to control the boat’s heel. In turn, this has allowed the boat to be sailed with an amount of windward heel. Windward heel increases righting moment and thus speed once fully powered.

ENZ foils
The foils clearly have large spans. Induced drag (the drag produced as a direct consequence of producing lift) dominates at lower foiling speeds and is a function of effective span^2. So this larger span, if coupled with a suitably small overall foil area, is probably what contributes to the large wind range of the ‘all round’ foils that ENZ most often use.
The foils also appear to have larger taper ratios (tip chord/root chord) and a lot of washout out (trailing edge up twist) towards the tips. This creates a foil which will behave a bit like a twisted sail. At high AoAs the tips will contribute to lift, but a lower AOAs the tips may produce no lift, or even negative lift (push down). The effect of this is to move the centre of pressure (CoP) progressively outboard towards the shaft as the AOA is reduced. This has 2 benefits: The bending loads on the foil are reduced allowing for a thinner, lower drag foil sections towards the root. Also, as speed increases and the AoA of the foil is reduced, the CoP moves outboard increasing the boat’s righting moment.
This foil design will create more induced drag than an elliptically loaded foil of the same span. At higher speeds, it will also create more drag because of the parasitic drag of the tips. I think we saw this latter effect downwind when Artemis (on small foils) was faster on leg1. But overall, these factors may explain the exceptional all-round performance of the foils.

ENZ v Artmeis – final day.
The winds were light, but increased. Artemis was on its large, light wind foils. ENZ on its all-round foils. Artemis appeared able to foil and sustain flight at lower speeds (around 15kts) than ENZ. This suggests that the Artemis foils were of larger overall area, camber and thickness. As soon as the wind increased, this rendered Artemis uncompetitive. But even in the light winds, Artemis appeared to gain no advantage. One possible reason for this is that in vmg terms, it is only faster to foil if the foil offers a better L/D ratio than the displacement hull. For the 50ft AC hulls, I would expect the optimum min drag speed (speed above which flight can be maintained) to be around 18kts. If Artemis was flying at significantly lower speeds, then this would suggest that its foils were unnecessarily large – it would have been better to use smaller/thinner/less cambered foils, foil a bit later, and sail high in displacement mode for longer (e.g. like ENZ).

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This is really crude (the first Polar I have ever generated, gimme a break) but it shows that SWE was pretty dang fast.

The SOG data is from all Semi-Final and Final races, for each boat,  NZL vs SWE, NZL vs GBR, SWE vs JPN 

NZL_SWE_AllSemiFinalsAndFinals.PNG.72f1c9d30886a1f97d9b2ec67353fc2f.PNG 

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is there just not enough data (or are the data apples and oranges) to compare polars for Oracle and ETNZ?

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37 minutes ago, TN_Kiwi said:

is there just not enough data (or are the data apples and oranges) to compare polars for Oracle and ETNZ?

I could for sure pull in the Oracle data from the Qualifiers. I don't have time right now to identify which specific race numbers Oracle were in but if anyone wants to look those up and post here then I'll likely pull those in too, to show an ETNZ / Oracle comparison. Could even post separate charts for different wind ranges.

edit: wasn't it already done above, somewhere? at least for the two ETNZ  vs Oracle races? edit2: I'm sure some superb charts will get posted after R1 and R2 tomorrow, for at least that set of conditions

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Today's portion of "analytics":

  1. Tactics: median TWS for NZL - 8.7kn, USA - 8.5kn.
  2. Tacking: average VMG at TWA<30deg: NZL-13.8, USA- 13.13
  3. Gibing: average VMG at TWA>160deg: NZL - 23.86, USA - 17.86

17JUN.png

17JUN-dww.png

17JUN-polar nf.png

17JUN-polar perf.png

17JUN-upw.png

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Awesome, thank you! That details today's ass-kicking speed differential in good detail. 

That last chart, does it say NZL was (relatively) in a lot more wind?

 

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20 minutes ago, ~Stingray~ said:

Awesome, thank you! That details today's ass-kicking speed differential in good detail. 

That last chart, does it say NZL was (relatively) in a lot more wind?

 

Looks that way.

I for one won't be cracking the cork on the champers just yet.

But if I was to choose which performance I'd want from my team today it would be ETNZ's performance. But still, a lot of fuck ups by them that could have cost both races. Turned monumental arse kickings into much closer affairs than they ever needed to be. 

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2 minutes ago, jaysper said:

Looks that way.

I for one won't be cracking the cork on the champers just yet.

But if I was to choose which performance I'd want from my team today it would be ETNZ's performance. But still, a lot of fuck ups by them that could have cost both races. Turned monumental arse kickings into much closer affairs than they ever needed to be. 

On days like today, you know what we sailors say, Jays. "I'd rather be lucky than good".

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16 minutes ago, ~Stingray~ said:

Fwiw

Avg_Speed, Avg_VMG by Race, Boat, Up/Down, Port/Starboard

RACE_01_02_AvgSOG_AvgVMG.xlsx

 

Thanks! ... from your data: ETNZ was 7.4% faster downwind, and 6.5% faster upwind overall. That's a BFD, in contrast to what Jimmy thought in the presser.

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3 minutes ago, TN_Kiwi said:

Thanks! ... from your data: ETNZ was 7.4% faster downwind, and 6.5% faster upwind overall. That's a BFD, in contrast to what Jimmy thought in the presser.

Of course but it's not enough to confidently determine the cause of the difference. Tactics, boat speed, luck? I think it looked like a combination of all three. 

I do think we had a touch of boat speed advantage over orifice but not as much as it looked like.

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20 minutes ago, TN_Kiwi said:

Thanks! ... from your data: ETNZ was 7.4% faster downwind, and 6.5% faster upwind overall. That's a BFD, in contrast to what Jimmy thought in the presser.

Good job deriving those %'s, thanks for doing and posting it.

Yes, a BFD but like jaysper says, there could be reasons to explain it. Maybe I will plot the wind variations tomorrow unless someone can please beat me to it, to see if the data shows it being pretty flukey out there.

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3 hours ago, ~Stingray~ said:

Awesome, thank you! That details today's ass-kicking speed differential in good detail. 

That last chart, does it say NZL was (relatively) in a lot more wind?

 

Yes, and the median TWS is higher for NZL, which supports the point.

I don't see much speed differential, not at all. Probably the most gains were created by maneuvers. I need to find the way to analyse that.

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21 minutes ago, dorox said:

... Probably the most gains were created by maneuvers. I need to find the way to analyse that.

 Part of my stats is the Geo numbers, computed down to actual separation distance, and vertical windward separation, but not (yet) to windward horizontal separation. Could easily add that but like you say, a way to analyze that would be a big mind-bender. The algorithm would have to do a trend analysis, smartly.

Am still having a mental block trying to rotate COG across races to an adjusted 'true north' COG_N for different TEA angle accurately, am not happy with my formula. If you have that figured, would like to see it? Something like COG_N = COG - TWD but with a few special cases.

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2 hours ago, ~Stingray~ said:

Fwiw

Avg_Speed, Avg_VMG by Race, Boat, Up/Down, Port/Starboard

RACE_01_02_AvgSOG_AvgVMG.xlsx

 

Where do you get this Data from? 

 

I wan't to see SOG, VMG & True Wind Speed for each tack and for each leg. 

 

I'm guessing it shows in the polars but i'm not totaly sure how to read them

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7 hours ago, ~Stingray~ said:

IMG_1538.thumb.PNG.19811441889a505080b5db88365e9c13.PNG

What happened on leg 5 with tnz? It doesn't only look like a couple of bad tacks? Did the wind die? (do we have local wind data for their location?)

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Just now, arneelof said:

What happened on leg 5 with tnz? It doesn't only look like a couple of bad tacks? Did the wind die? (do we have local wind data for their location?)

They had a period where they just sailed into a hole. That's how Orifice came right back.

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You could see them in the distance when Orrifice was rounding the bottom mark, they dropped to 11kts, I thought they had a failure, then they ramped back up to 20 odd and then tacked

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1 hour ago, jaysper said:

They had a period where they just sailed into a hole. That's how Orifice came right back.

Looking at the speeds, two holes actually, a massive one at either end of the leg, they were well out of phase and given the short boundaries, really hard to get back in phase.

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9 hours ago, jaysper said:

Of course but it's not enough to confidently determine the cause of the difference. Tactics, boat speed, luck? I think it looked like a combination of all three. 

I do think we had a touch of boat speed advantage over orifice but not as much as it looked like.

ETNZ hit the sweet spot wind-wise - or close to it. They designed Aotearoa, optimised for those weather expectations.

Unless OTUSA has a radical fix during the 5 days off, the only thing that might save them is decent a blow.

Of course, we'll know whether that's all wishful-thinking-shit by tomorrow. 

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22 minutes ago, Sailbydate said:

ETNZ hit the sweet spot wind-wise - or close to it. They designed Aotearoa, optimised for those weather expectations.

Unless OTUSA has a radical fix during the 5 days off, the only thing that might save them is decent a blow.

Of course, we'll know whether that's all wishful-thinking-shit by tomorrow. 

I think if it gets to 12 knots that's where our sweet spot wears off (and whompers stay in the shed) and Oracle's starts to kick in.

Of course etnz could have been keeping the whoppers in the shed at 12knots previously as a method of obfuscation. 

Right now wind guru is forecasting 10 with gusts to 11, so presumably we will see whompers again't although modern slightly higher.

Do these foils remind anyone else of the Auckland harbour bridge with the nippon clip ons? 

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15 hours ago, ~Stingray~ said:

IMG_1538.thumb.PNG.19811441889a505080b5db88365e9c13.PNG

 

7 hours ago, arneelof said:

What happened on leg 5 with tnz? It doesn't only look like a couple of bad tacks? Did the wind die? (do we have local wind data for their location?)

Here are the numbers, perhaps someone would like to chart it nicely.

R-17061702_Leg-5_Boat-NZL_Speed_Course_TWS_TWD.xlsx

Leg 5 looks basically like this 

R-17061702_Leg-5_Boat-NZL_Speed_Course_TWS_TWD.PNG.24e2dfb97c8a0116b958ba3bd5dd8aa6.PNG

 

Including Course sailed:

R-17061702_Leg-5_Boat-NZL_Speed_Course_TWS_TWD_2.PNG.67a9eb0656209648d6e7f8d5f1ad08ec.PNG

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44 minutes ago, rgeek said:

must feel ominous the way speed leaches away like that

It suggests that tacking when under a certain TWS pressure (around 7 knots?) is deadly. And that you drop off the foils at a boat speed under about a 16 knots limit.

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Today's data.

Oracle had non symmetric foils - look at the speed difference on the polar - port foil was worse.
Not much of the straight line speed difference I would say. Probably tacking is killing them.

 

18JUN-dww.png

18JUN-pol.png

18JUN-pol_f.png

18JUN-upw.png

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16 minutes ago, dorox said:

Today's data.

Oracle had non symmetric foils - look at the speed difference on the polar - port foil was worse.
Not much of the straight line speed difference I would say. Probably tacking is killing them.

 

18JUN-dww.png

18JUN-pol.png

18JUN-pol_f.png

18JUN-upw.png

 

1.jpg

2.jpg

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