Talk:USA 17

Photo Needed
Picture of first sail of BOR 90 in the Straight of Juan de Fuca

The question is: has this photo been released to the public domain with a GNU free license? To use it here, it has to be free. The photographer seems to be Sean Trew. If he would upload the file and release it into the public domain, it could be used on the page.--Paul (talk) 22:55, 5 March 2009 (UTC)

Swiss news link
Here is a link to a recent English-language Swiss newspaper with quite a bit of useful and current information about the next Americas Cup race and the BMW Oracle team. I'll leave it to others to integrate any information into the WP article. N2e (talk) 22:05, 27 April 2009 (UTC)

November 2009 dismasting
I agree with Paul.h: we don't know enough about the dismasting to add it to the article. It could have been caused by some minor error or failure. And, at this stage, it isn't clear that it will have any effect on things. So it may be a minor failure, not worth mentioning.--Gautier lebon (talk) 09:12, 10 November 2009 (UTC)

January 2010 update
Added update of the first time the USA was sailed at the AC33 venue and the first time she was sailed with her name emblazoned. Reference included. 24.188.207.20 (talk) 02:07, 22 January 2010 (UTC)

Correct name
I don't think that "USA 17" is the correct name of the yacht. The name as shown on the CoD and the other official documents is "USA". I presume that "17" refers to the number on the sail. In accordance with ISAF rules, sails carry boat numbers in addition to a counrty designation. Thus I presume that the sail on USA shows the designation "US 17", or something of that nature. Similarly, the name of the SNG yacht is "Alinghi 5" and its sail will show the designation "Z n" where n is some number. I would propose that we name this article "USA (yacht)" and add an entry to that effect in the USA (disambiguation) page.--Gautier lebon (talk) 08:08, 23 January 2010 (UTC)

The correct name is not clear, and it certainly is debatable, but this interview snippet: ''v & v.com: USA-17 is now the official name of your trimaran. USA is the name that you had officially mentioned when submitting your challenge, but why 17?'' James Spithill: ''It is the lucky number for Larry Ellison - perhaps because he was born August 17? Among its vessels, other before our trimaran have increased this figure, like his famous maxi Sayonara or last TP52.'' from this website seems to support "USA 17" as the correct name.--Paul (talk) 16:40, 26 January 2010 (UTC)


 * Indeed. I have added the citation and also used it to document the wing specs.  By the way, I cannot document it yet, but both boats can apparently sail at 10-12 degrees off the apparent wind, which is like an iceboat, and will achieve VMG over 2 times windspeed and speed of something like 5 times windspeed.  I will add that when I have reliable citations.--Gautier lebon (talk) 17:02, 26 January 2010 (UTC)

Specifications
Does anybody know what the source is for the displacement (weight) specification, which is shown as 16 metric tons. Given that the volume of the amas is well over 50 cubic meters and that at times the downwind ama seems to be fully immersed, I wonder about the displacement. The BWM Oracle Racing web site does not appear to give the displacement.--Gautier lebon (talk) 08:44, 1 February 2010 (UTC)


 * I thought it was from reference #10, but after looking, apparently not. I agree that GGYC/BOR have never published a displacement spec. I think it should be shown as "N/A" in the spec table. UPDATED: The February 2010 issue of Sailing Magazine estimates the sailing displacement of A5 at 15.4 metric tons, and USA-17 at 11.8 metric tons --Paul (talk) 18:40, 1 February 2010 (UTC)


 * Hard to believe, I would have thougnt that A5 would be significantly lighter, but who knows. The Geneva newspaper gave an estimate of 18 t for USA, see .The estimate of 12 t for A5 was taken from what the helicopter pilot said when they flew the thing over the Alps, but who knows what the reliability of that number is.  Worse, the link that had the information is dead but I found a new reference, see .  I've updated the displacement for A5.  I guess that we can leave USA as it is for now and update when we have reliable information, unless you think that it is better to fill in N/A and/or to add the citation to the Geneva article that gave an estimate for the displacement of USA.--Gautier lebon (talk) 10:59, 2 February 2010 (UTC)

The Wing
A section on the wing has been added to the BMW Oracle Racing page, see BMW_Oracle_Racing. It seems to me that that section would more appropriately be included in this article on USA 17. Comments?--Gautier lebon (talk) 09:37, 11 February 2010 (UTC)
 * Definitely agree. One article should be about the team and and the other about the boat with appropriate links between the two articles. Boatman (talk) 11:26, 11 February 2010 (UTC)


 * Done. I also rewrote the section, but I think that it could still use some improvement.--Gautier lebon (talk) 09:25, 12 February 2010 (UTC)

VMG in 1st Race
The sentence "As such downwind velocity made good is a nominal value only, not an actual measurement of boat performance." is incorrect. The VMG from the first mark to the finish line is not a nominal value it is an actual value of the VMG USA 17 achieved on the final leg of the course. The VMG as a ratio of the wind speed gives a very good approximation of the boat performance recognising that the wind speed and direction was variable throughout both legs of the race and also USA 17 did not track a direct course from the 1st mark to the finish. Appreciate comments before I update the article. Thanks, Boatman (talk) 12:26, 14 February 2010 (UTC)


 * You are correct. I think that the correct statement would be something like "As such the ratio between downwind velocity made good and windspeed is an approximation".  The facts are that USA took about 1 hour to sail 20 nautical miles downwind in winds that averaged 7 knots at the surface.  Since USA was sailing on the surface, it seems appropriate to use the wind speed at the surface.  In any case, it covered the 20 nautical miles downwind considerably faster than the wind, even if you take the wind at 70 meters, because surely the wind at 70 meters was no more than 12 knots at most.--Gautier lebon (talk) 14:27, 14 February 2010 (UTC)


 * Separately, I would appreciate your comments on the issue being discussed at Talk:Sailing_faster_than_the_wind.--Gautier lebon (talk) 14:27, 14 February 2010 (UTC)


 * The reported course near sea level wind measurements of 5-10 knots don't correlate with the only statement I can find of (true) wind at mast height, stating 15 knots here: Add to this that the true wind direction according to race commentary had changed at the top mark from 180 degrees (when course was set before race start) to 160 degrees when the boats were approaching the windward mark. This renders a claim that the boat sailed "considerably faster than the wind" in the context of actual boat performance to VMG (downwind) as speculation, regardless of it being "common knowledge" that in nominal 5-10 knots of wind, the boat covered a 20 nautical mile nominally downwind leg of course in just over one hour.  I'll edit the page as suggested. 202.180.115.243 (talk) 12:35, 17 February 2010 (UTC)


 * Your edit is OK with me. My point is that, no matter how you slice it and dice it, USA reached the downwind mark faster than a balloon would have drifted down to it, even if the balloon was at 70 meters, because 20 nautical miles in one hour is still faster than 15 knots.  But your paragraph regarding approximation is perfectly correct.  Pity neither side is publishing the actual data that they collected.  Their computers calculated true wind speed and direction, and VMG.--Gautier lebon (talk) 16:33, 17 February 2010 (UTC)


 * 20 nautical miles in 63 minutes in 15 knots of wind doesn't support your pet theory. The true wind direction was not 180 degrees, and as such a balloon would never have reached the downwind mark - it would have missed it by many miles. The "downwind" leg was a reach.  You don't know real windspeed or direction, and if you did then there's still the problem of "deciding" which windspeed to measure - for example is it be the average of measurements taken at various heights on the wing, or at the top? Their computers probably did measure it, but as it conditions would not have been constant, deciphing the data for the purposes of testing your theories would still be a considerable problem.  I don't believe that the USA 17 Oracle page is the place to discuss it, and links to your "downwind faster than the wind" page aren't appropriate. 202.180.115.243 (talk) 03:05, 18 February 2010 (UTC)


 * But there was nowhere near 15 knots of wind. The gradient between the surface and above gets more pronounced with velocity. 5 knots, 2m above the surface is about 7 knots 40m up. 10 knots at 2m is 13.5 knots 40m up. These boats absolutely DO attain VMG's that are multiples of the wind speed. Many observers have commented that upwind they can do 1.5 the windspeed, and 2.0 times downwind. I'll look around a bit a bit later, I have no doubt that we can find references for this to use in the article, and don't have to do our own calculations. UPDATE: here's a press conference where a member of the BOR design team confirms that the boat can sail at 2x windspeed VMG Feb 09 Press Conf. --Paul (talk) 17:21, 18 February 2010 (UTC)talk:Paul.h|talk]]) 14:26, 18 February 2010 (UTC)


 * The "absolute" figures you calculate for gradient can only be very rough approximations, a referenced comment from Wind Gradient it is ... "difficult to predict since the wind gradient may vary widely in different weather conditions". If you don't believe that, then do some research to find out more, also about effect of temperature, sea state, inversion etc.
 * The video link at Feb 09 Press Conf does not present any data at all to support your claim that the boat can attain 2x windspeed (VMG to wind - down or up for that matter) - and is about use of LIDAR for remote wind-speed measurement. 202.180.115.243 (talk) 20:00, 18 February 2010 (UTC)


 * On the press conference, sorry I provided the wrong link. Here it the correct one BOR sailing team press conference February 9, 2010 at about 1:20 Matteo Plazzi, navigator of the boat, says that it will go 1.5 to 2.0 times VMG upwind, and faster than that downwind. As to "difficult to predict since the wind gradient may vary widely in different weather conditions", It is possible to provide obfuscations and objections for a long time, but no where will you ever find a source that will claim 15 knots of wind at 40m when it is 10 knots at 2 meters. But it doesn't matter, Plazzi's statement pretty well nails down the capabilities of this boat.--Paul (talk) 21:52, 18 February 2010 (UTC)
 * "No where will you ever find a source that will claim 15 knots of wind at 40m when it is 10 knots at 2 meters" . Try this site from the Australian Bureau of Meteorology  "This change in wind speed can be easily detected between the masthead and the deck and even though the direction of the true wind changes ever so little in the lowest 30 metres, it's the direction of the relative wind or the wind felt by you and by the sails that can change quite markedly between the deck and the masthead. It all comes down to the stability nature of the air-sea(land) interface. Differences in speed range from very little in unstable air (around 5%) to enormous amounts in stable air (up to 300% )" Please also read comments re stable unstable air definition, and shear in developing sea-breeze conditions.202.180.115.243 (talk) 10:59, 19 February 2010 (UTC)
 * I have found a reliable citation for wind gradient and added it to that article. According to that source, the wind gradient is not significant for sailboats if the wind is over 6 knots.--Gautier lebon (talk) 09:52, 26 February 2010 (UTC)


 * And, if you listen to Plazzi beyond his 2.0 times the wind VMG mark, he is asked specifically if the boat would beat a balloon downwind to the finish line, and he confirms this is true.--148.87.1.167 (talk) 22:30, 18 February 2010 (UTC)


 * Very well stated Paul. Matteo Plazzi's quote definitely suffices for this article and very well indicates the capabilities of the boat. Paul, I 100% support your views on this VMG topic with respect to the USA 17 article. Boatman (talk) 22:04, 18 February 2010 (UTC)


 * I listened to that with a smile on my face as big as his was.  That creates a problem.  Boats sailed on tacks of about 135 degrees from the wind evidenced by them executing 90 degree tacks (gybes) when sailing downwind.  Lets just say that Plazzi's claim really is as it could seem to be superficially, not something "lost in translation" that they do "more than twice" wind-speed, and he really means that as (over) double vmg to wind direction.  There's a very clear problem considering that they seem to have also claimed that the boat can sail on a windward leg as posted on the WP article - with as little as 20 degress apparent wind and "The boat sails so fast downwind that the apparent wind it generates is only 5-6 degrees different to that when it is racing upwind".  Do the vector diagrams / maths, which then show that apparent wind angle would be (less than) half of that 25-26 degree figure.  Please don't dismiss clearly conflicting "evidence" as "obfuscation". 202.180.115.243 (talk) 04:17, 19 February 2010 (UTC)


 * Sorry for not commenting earlier, but I couldn't. According to my calcuations, the boats were sailing at about 13 degrees off the apparent wind, both up and downwind.  Neverthless, I think that we should retain the 20-degree and the 5-6 degree statements in the article because they are taken from reliable citations.  Recall the Wikipedia is about citations, not speculation.--Gautier lebon (talk) 14:10, 19 February 2010 (UTC)
 * Yes - keep the 20 (UW) 25/26 (DW) apparent wind figures from reliable citations and dump links to the "faster than the wind page" until that page is tidied up (see my comment below). 13 degrees is very simply - not believable.  "Data" suggesting that it was achieved should either be deleted, or explained - hence my first edit on this page, resulting in this thread.  I'm not very happy with the wording: "As such the ratio between downwind velocity made good and wind speed is an approximation only." I'll think about a suggested change, and get back. 202.180.115.243 (talk) 02:53, 20 February 2010 (UTC)


 * Why is 13 degrees simply not believable? Iceboats can do better. Remember that these boats are the fastest on-water VMG machines every built.--Gautier lebon (talk) 08:22, 23 February 2010 (UTC)


 * It's not believable simply (without any need for any special math) because you can extend the "logic" to conclude that at any sailing angle to the real wind, the "lemon pip squeeze" explanation tells us that at a fraction of a degree off directly downwind, if frictional losses are reduced to zero, then infinite speed downwind (VMG) in infinitely small wind strength is possible (excl. special relativity effects) - according to you, as apparent wind will always remain <180 degrees. You have missed something very fundamental.
 * You are correct. If there is no friction, then there is no limit to the "lemon pip squeeze" which is why iceboats can achieve such high VMGs.  However, the friction arises not just from the surface, but also from the apparent wind.  So even on a frictionless surface, the speed will be limited.  Please tell me exactly what "very fundamental" thing I have missed.--Gautier lebon (talk) 09:49, 26 February 2010 (UTC)


 * You haven't provided verifiable data that those VMGs have been achieved, only a pile of circular arguments and unverified data - particularly absolutely no hard data only anecdotes and guesses as to true wind speed and true wind direction. The "Greenbird" data does not show VMG (to wind) better than wind speed unless you presume a certain wind-speed and direction.  You might think that "on the balance of evidence" your presumption is correct - but that's just an opinion, regardless of how many nothers share your belief. The necessary data is simply not there. The fundamantal thing that you miss out on is that you can't squeeze a lemon pip when you have both fingers applying force at the same speed and in the same direction, even if you apply "shear" between your fingers. 202.180.115.243 (talk) 08:59, 28 February 2010 (UTC)


 * I guess we disagree regarding what is an anecdote and what is hard data. I've provided numerous citations to the effect that VMG greater than wind speed has been achieved.  You state that all those citations are unreliable, but you don't provide any citation stating that VMG is limited to wind speed or to less than wind speed.  You are correct that the lemon pip analogy does not apply perfectly to sailboats.  In sailboats the forces are not applied in the same direction, nor are they equal, nor do they have equal speeds.  The apparent wind hits the sails at a certain angle and speed, and produces a certain force.  Those are not the same as the angle of the hull with respect to its progress through the water, nor the lift generated by the hull, nor the speed of the hull through the water.  At some point, an equilibrium is reached.  As shown by the elementary trigonometrical calculations in sailing faster than the wind, that equilibrium may well be reached when VMG is greater than true wind speed.  So there is no theoretical impossibility.  The other question is whether this can be achieved in practice.  That is where the various citations regarding iceboats and sandboats come in.  Surely there isn't a vast conspiracy out there of people who, independently, publish information in order to hoax the gullible?  Please refer to --Gautier lebon (talk) 15:27, 1 March 2010 (UTC)


 * Hi 202.180.115.243, Instead of continually disagreeing, for the fourth time of asking, please would you now be specific on the text/words that you would like to use re USA 17's VMG/speed capabilities. The suspense is now too much!! You are have a lot of information on VMG etc please help us by drafting an appropriate paragraph or sentence. Please would you also register with a user name so that we can talk to you. Thanks Boatman (talk) 10:44, 24 February 2010 (UTC)


 * The racing results section needs to be rewritten. Bias suggesting that downwind progress (VMG) faster than the wind was achieved needs to be corrected as there is absolutely no hard evidence that was achieved.  Repeated circular referencing ("but it's possible because ice boats do it") doesn't wash, because much of the data presented for those claims is not of good quality. It may be true that downwind (VMG) faster than the wind was achieved in "semi-official" results, based on original course setting, commentary wind speed reports from remote sensing, and course times.  But that begs explanation of likely variables contributing to this result, real wind direction, real wind speed, wind gradient. 202.180.115.243 (talk) 11:41, 24 February 2010 (UTC)


 * As anybody can verify, the sand yacht record cited in the article on sailing faster than the wind is as official as it gets. And the VMG times windspeed is based on GPS data.  I still don't understand whether you simply do not believe that downwind VMG greater than wind speed is possible.  If you do accept that it can be the case for iceboats, sand yachts, etc., then why do you doubt that it was the case for USA 17?--Gautier lebon (talk) 09:56, 26 February 2010 (UTC)


 * For that example the speed is official. The VMG (to wind direction) is not.
 * "110 deg from the nose is the fastest point of sail. This is actually about the same for all sailboats, independent of speed." reference . The calculation based on 120 degrees is an error - based on nothing more than a "guess" as to wind direction.
 * Redo your calculations based on:
 * 110 degree angle to real wind. Highest wind-speed measured 47 miles per hour, 3 second duration maximum recorded boat speed, and the result shows downwind speed of approx 43 mph, less than maximum recorded wind speed. Despite what you claim here and eslewhere the "Greenbird" data does not constitute reliable evidence that downwind (VMG) faster than the wind was achieved.    —Preceding unsigned comment added by 202.180.115.243 (talk) 02:02, 28 February 2010 (UTC)
 * I did nothing more than reproduce the data given in the citation, and make some calculations based on that. I don't see what justification there is for assuming that one angle would be better than the angle that was actually observed and documented in the record report.--Gautier lebon (talk) 15:27, 1 March 2010 (UTC)


 * Hi 202.180.115.243, You have said ".... needs to be re-written..", ".....no hard evidence.....", .....doesn't wash...", "....data not of good quality...".   So for the fifth time of asking, please please please would you now be specific on the text/words that you would like to use in the racing results section for USA 17's VMG/speed capabilities. You seem to have a lot of information and experience re VMG etc we ask yet again to please help us by writing an appropriate paragraph. For the second time, please would you also register with a user name so that we can talk to you. Thanks, Boatman (talk) 16:23, 24 February 2010 (UTC)

Hi Boatman. I only want that Encyclopedic content must be verifiable. 202.180.115.243 (talk) 10:59, 19 February 2010 (UTC)
 * Hi 202.180.115.243, Please would you now be specific on the text/words that you would like to use re USA 17's VMG/speed capabilities. Thanks, Boatman (talk) 08:07, 19 February 2010 (UTC)
 * Hi 202.180.115.243, We 100% agree with your reply, so what do you think the verifiable statement should be which relates to USA 17's VMG/speed capabilities? Thanks, Boatman (talk) 17:12, 19 February 2010 (UTC)


 * Fully agreed. What, in  your opinion, is not verifiable?  As Paul and others have pointed out, there can be no serious doubt that these boats had VMG of about 2 times the surface windspeed upwind and about 2.5 times the surface windspeed downwind.  There is nothing extraordinary about that, ice boats can do better and sand yachts can do the same.  And, as documented in the article on sailing faster than the wind less extreme sailboats can achieve downwind VMG slightly greater than windspeed.  Those boats, like the 18-foot Skiff, do not have gigantic masts, so the wind gradient effect is negligible.--Gautier lebon (talk) 14:10, 19 February 2010 (UTC)
 * There is serious doubt when there's obvious conflicting data - which there most certainly is in this case. You also need to "get" that 160 degrees (20 degrees off directly downwind course) isn't a downwind course at all - and as such possible progress between the marks would always be faster than on a directly downwind course.  Some of the links on the Sailing faster than the wind page seem seriously misunderstood.  For example, the polar chart for 18 footer here   doesn't show possible downwind progress faster than the wind at all.  It shows peak speed over ground in a 10 knot wind of about 15 knots at 80-90 degrees.  It shows speed over ground of about 9 knots at 135 degrees, and a peak in speed over ground of about 12 knots at about 145 degrees (the peak probably due to use of a close-hauled asymetric headsail when at that angle to the wind).  There's nothing there to show that downwind progress (VMG to wind speed) above wind speed can be achieved, in fact as a reliable source on relative performance of some high-performance sailboats, it's good evidence that it isn't achieved. 202.180.115.243 (talk) 02:53, 20 February 2010 (UTC)


 * Your example polar, using the line for the 18-ft open class skiff proves it is possible to have a VMG greater than the windspeed downwind. If you'll measure a bit more carefully, the graph shows 15 knots boat speed at 142 degrees. This works out ( VMG = bs * cos(deg) ) to 15 * .788 = 11.8 VMG which is greater than the 10 knot wind speed.--Paul (talk) 20:21, 23 February 2010 (UTC)


 * Paul is correct. My comment below refers to the comment preceding Paul's comment, not to Paul's comment.--Gautier lebon (talk) 15:31, 1 March 2010 (UTC)


 * I'm sorry, but I think that you misinterpret what a polar chart shows. A polar chart shows the speed of the boat when it sails in a certain direction.  If you take the projection of the speed vector onto the vertical axis you get, respectively, the VMG upwind and the VMG downwind.  If you take the VMG downwind/upwind and divide by the wind speed, you get the factor that we are talking about.  You seem to still hold the position that a downwind VMG of greater than windspeed is not possible, whereas there is ample evidence to show that it is.  Just look at the sand yacht speed record at .--Gautier lebon (talk) 08:22, 23 February 2010 (UTC)
 * Yes - it's very entertaining, but there is various comment about wind speed, "about" 15 knots, "10 knots" but with no data on how (true) wind speed and direction was measured. There's good detail on how GPS is used to verify speed over ground, but from there this data completely falls apart, as there's not even a description on method used to measure wind speed and direction. 202.180.115.243 (talk) 09:01, 24 February 2010 (UTC)


 * Hi 202.180.115.243, So, what do you think the verifiable statement should be which relates to USA 17's VMG/speed capabilities? Thanks, Boatman (talk) 09:17, 20 February 2010 (UTC)


 * In talking to one of the designers of USA-17 today, he said the boat does about 1.4 x TWS VMG upwind and 1.8 x downwind. --Paul (talk) 23:17, 20 February 2010 (UTC)


 * Citation please. VMG as a factor of windspeed will obviously depend on the strength of the wind.  There is ample evidence to suggest higher figures. Please give the citation for this particular claim.--Gautier lebon (talk) 08:22, 23 February 2010 (UTC)


 * I can't provide a citation because these numbers are from a personal conversation with the design team leader Saturday at San Francisco City Hall. I think they seem low to you because they are based on the true wind speed at the masthead and thus are affected by wind gradient effects, e.g. 15 knots at a 70m meter masthead would be about 11-12 knots at 2m. I was told boat speed is about 2x TWS upwind, 2.5x TWS downwind, and 3.0x on a reach. Apparent wind angles are 15-17 upwind, and 20-30 off the wind. Here are some calculated cases:
 * TWS=10 TWA=45 BS=20 AWA=15 VMG=14.1 (1.4 x)
 * TWS=10 TWA=135 BS=25 AWA=22 VMG=17.7 (1.8 x)
 * TWS=10 TWA=90 BS=30 AWA=18
 * Factoring the gradient between 70m and 2m, the apparent VMGs would be 1.8x and 2.3x. I knew nothing about multi-hulls and VMG greater than TWS before this Cup series. I've learned a lot, and still find numbers like this to be incredible! --Paul (talk) 17:16, 23 February 2010 (UTC)


 * Paul, sorry, I did not mean to imply that the numbers were too low. I just meant that the numbers will depend on many factors.  Indeed, I too was suprised by VMGs much greater than windspeed.  I got into this because I was exchanging E-Mails with somebody who knows a lot more about sailing that I do, and he told me that the boats could be expected to achieve VMG greater than wind speed on the downwind leg.  I told him that that was not possible.  He insisted.  So I did some research to prove him wrong, and found out, much to my surprise, that he was absolutely right.  I agree that we don't have the date to tell whether downwind VMG as a multiple of wind speed was 2.0 or 2.5, but it surely and obviously was well over 1.0, indeed well over 1.5.  So I don't understand what we are arguing about.  As Boatman has stated above, it isn't clear what, if anything, needs to be changed with respect to the current text, which does incorporate a very clear caveat regarding the calculations, wind shifts, wind gradients, etc.--Gautier lebon (talk) 09:49, 26 February 2010 (UTC)


 * There's absolutely no data worthy of WP here. Using Hellman's exponent calculation for shear, 10 knots at 10 metres (not 2 - the difference would certainly be greater - you do the calculations yourself) gives about 14 knots at 70 metres.  You can do the calculations until your fingers bleed and come to no useful conclusion at all - as it's just an estimate, but there's some known data (residual sea state, developing sea-breeze) to indicate that the differential (10 metres -> 70 metres) may have been 8 knots or more, let alone 2 metres -> 70 metres, or whatever "average" you choose to try to prove something.  The "downwind" course wasn't "downwind", it was clearly reported in the commentary as having shifted to 160 degrees.


 * I don't know where you get those wind gradients. I've now looked up a reliable source and added it to the wind gradient article.  As you can see, Bethwaite says that the gradients are insignificant for sail boats (even with 70 meter masts) if the wind is over 6 knots, which was mostly the case here.  Regarding "downwind", we are discussing VMG, so the actual course of the boat doesn't matter.  The actual wind direction does of course matter.  It shifted around during the race, of course.  But I haven't seen any reports to the effect that there was a persistent shift during the downwind leg.  So there is no reason to think that the average wind was not downwind.--Gautier lebon (talk) 09:49, 26 February 2010 (UTC)


 * The gradient is based on Hellman's exponent calculation. Your "reliable" source is probably wrong - here's a source showing wind gradient reasonably consistent with Hellman's exponent with wind speed (10m) at 5.5 metres per second (~ 10.7 knots), a differential of ~35% between 2 and 10 metres.  Any sailor should tell you the comment "gradients are insignificant for sail boats if the wind is over 6 knots" is total and absolute nonsense. You're selectively acquiring poor quality data to suit your "faith", and editing WP pages with great rapidity, then circular referencing your own edits when your "belief" is challenged in discussion.  Here's the extent to which Alighi went to track wind shear : .  Rather pointless when they would only sail a race when wind strength was above your "6 knots" which makes gradients "insignificant" - no?  The wind direction also shifted as a sea-breeze developed and was reported as 160 degrees (a 20 degree shift) before the boats rounded the upwind mark.  Of course it's possible it shifted "back", but extremely unlikely, more likely it shifted more than the 20 degrees.  202.180.115.243 (talk) 08:59, 28 February 2010 (UTC)


 * Dear 202, please avoid ad-hominem attacks. And please don't dismiss as "wrong" any citation that does not match what you think is correct.  I think that we are all working in good faith here, to ensure that Wikipedia content is correct and verifiable.  My source is a published book, by a well-known author and editor, see [].  Your source is an apparently not peer-reviewed web page.  Further, your source does not actually contractict my source.  Your source shows that the wind gradient is very strong between zero and 1 meter, then drops off rapidly.  Surely you don't think that the nominal wind strength reported by the race committee was measured at zero or even at 0.5 meters?  We don't know at what height it was measured, but it was probably at least two meters above the surface.  The article that you cite regarding Alinghi's use of light sea planes doesn't say anything about wind gradient.  It says a lot about the wind varying over a 20 mile course, and about wanting to measure the wind at heights greater than 5 meters.  One reason for doing that is that the wind is more stable and more predictable higher up, as explained in great detail in the book that I cited above.--Gautier lebon (talk) 15:27, 1 March 2010 (UTC)


 * Gautier Lebon. To check your reference, I've ordered a copy of the book you've pulled a reference from.  The various material I referenced is also published and authored by meterologists, engineers etc - "experts" in their field.  Nothing I can find supports the claim that at over 6 knots (even with a 70 metre mast) wind shear effect is "insignificant". 202.180.115.243 (talk) 20:31, 3 March 2010 (UTC)


 * As far as "I can't provide a citation" data (above) goes - please kindly keep it to the yacht club bar - or please front up with verifiable data 202.180.115.243 (talk) 09:01, 24 February 2010 (UTC)
 * Paul was being very helpful. Once again, there are many verifiable citations provided in the article on sailing faster than the wind, I cannot understand why you don't accept them.  Please consider in particular the formal, official, sand yacht record that is cited there.--Gautier lebon (talk) 09:49, 26 February 2010 (UTC)


 * "Please consider in particular the formal, official, sand yacht record that is cited there". There is no formal official record for downwind VMG performance for "Greenbird" linked to in WP that I can find.  The wind direction of " 'about' 120 degrees" is a guess based on nothing more than a casual observation that wind was "Northwest".  Richard Jenkins is quoted here:  stating that optimum speed is achieved at 110 degrees.  Gusts were recorded at 47 mph.  126 mph at 110 degrees gives 43mph VMG (to wind-speed) - a big difference to the 1.5 times wind speed guessed at if wind had been at 120 degrees.  Maximum speed over ground was recorded over a 3 second period.  VMG at claimed best angle to the wind is less than maximum wind speed recorded.  There's absolutely no data on real wind speed where the sand yacht was achieving those speeds, which was probably observed either at "camp" or start of the course - perhaps a mile from where the sand-yacht was, and there's no data on calibration, accuracy etc for wind recording instruments.  So it's not a verifiable citation from the point of "proving" that velocity made good faster than the wind was achieved.  Even if for a three second period, VMG (to wind direction) progress had been faster than wind speed, it still proves nothing unless it can be shown that this was not the simple effect of momentum and a changed bearing. 202.180.115.243 (talk) 06:16, 28 February 2010 (UTC)


 * Yes, the actual wind speed and VMG as a factor of windspeed are approximations. We all know that. You use gusts for your calculations, but I'm using averages, which is surely more appropriate: why not use lulls instead of gusts.  Are you seriously arguing, having looked at the report, that the downwind VMG was not greater than true wind speed?  THe article you cite regarding Greenbird predated the record.  The report at  is, I think, a more reliable source of information. Regarding momentum, this was discussed on the talk page for sailing faster than the wind and it is easy to show that it cannot have a significant effect: the friction induced by the apparent wind is so strong that no iceboat or sandyacht can coast downwind very far relying on its momentum.  I have the impression that you believe that downwind VMG greater than windspeed is impossible because it violates some physical law.  If so, please explain that, and provide citations.  If you are right, we need to correct the article.--Gautier lebon (talk) 15:27, 1 March 2010 (UTC)


 * "Averaging" wind speed measurement is absurd. For a start there are only three points of reference "30mph" to "40mph" with peak gust of "47mph".  None of the measurements are referenced for time the measurement was taken or position relative to the sand-yacht where they were taken.  In the end you have no information on actual wind speed over the 3 seconds when the record speed was achieved.  But we do have data to show that:
 * *The designer of the sand yacht claims that maximum speed (over ground) is achieved at an angle to the wind of 110 degrees. That is not 120 degrees - so where did the 120 degree figure come from?  Is it conceivable that the designer of the vessel would sail at an angle to the wind less than his stated optimum for achieving speed over ground at the time he was achieving world record boat speed?
 * *We know that at claimed optimum angle to the wind (110 degrees) VMG downwind speed over the time period that maximum speed over ground was recorded is less than peak wind speed recorded generally on the course.
 * *So the data does not show clear evidence that downwind progress faster than the wind was achieved.
 * *The known data cannot be used to calculate progress downwind (VMG) without making assumptions about both wind speed and direction, But assumptions have been made, then the "conclusion" published in WP in a sub-section of the article sailing faster than the wind and that "conclusion" referenced in various other related WP articles.
 * That conclusion is not verifiable, it is not neutral, and it should not be in WP. 202.180.115.243 (talk) 20:31, 3 March 2010 (UTC)

One more point: In the first race, USA covered the 20-mile downwind leg in 1h03. That's VMG of 19 knots. If the wind were 15 knots, then a ballon would not have reached the finish line before USA. If the wind were 20 degrees off the course, then, after an hour, the balloon would be 15 miles down that 20-degree vector. If my trigonometry is correct, the balloon would be 5.13 miles off the course, and its "VMG" along the course would be 14.1 miles. USA would have reached 14.1 miles down the course in 14.1/19 hours, that is 44.5 minutes. USA could then turn and sail toward the lateral position that the balloon would reach an hour after having been released. Since USA can sail at well over 20 knots on a reach (more like 30), it would reach that position in less than 15 minutes. So it would arrive before the balloon at the position to which the balloon would drift in an hour. And of course that is an inefficient way for USA to reach that point in space. USA could reach it faster by directly sailing towards it, since the point is not dead downwind, so USA would not need to gybe downwind to reach it. Not to mention that the wind was not 15 knots, but much less, so the balloon would have been considerably slower. If I got something wrong in the above, please do correct it.--Gautier lebon (talk) 16:37, 2 March 2010 (UTC)


 * That entire paragraph is absurd speculation. It's enough to know that the wind was not at 180 degrees, and that as such the hypothetical balloon would have missed the mark, and that at an angle less than or greater than 180 degrees, the boat would have reached the leeward mark in less time than if the true wind direction had been at 180 degrees.  You do not know real wind speed, wind direction, horizontal and vertical shear conditions which affect boat performance, but make assumptions here to reach a non-neutral conclusion. 202.180.115.243 (talk) 20:31, 3 March 2010 (UTC)


 * I guess that we have different views of what is speculation and what is absurd. If the wind was not at 180 degrees, the balloon would go elsewhere.  And one can compute how long it would take the boat to get to the same place.  If the boat gets there before the balloon, it's downwind VMG is greater than windspeed.  The calcuation is based on observed performance of USA 17 and conservative assumptions regarding wind speed.--Gautier lebon (talk) 14:26, 5 March 2010 (UTC)

Summary of VMG discussion and proposal
As far as I can tell, the discussion above can be summarized as follows.--Gautier lebon (talk) 16:20, 2 March 2010 (UTC)


 * Some contributors feel that the actual data from the 2010 America's Cup provides evidence that USA 17 achieved downwind VMG greater than wind speed. They point out that this is not surprising, given the available performace data for iceboats, sand yachts, etc.


 * One contributor correctly pointed out that wind speed direction and strengh for the Cup races are approximate, so any estimate of VMG as a multiple of wind speed must be an approximation. The article was corrected to reflect this.


 * The same contributor, however, also states that further rewriting is required, but does not propose specific edits. The contributor seems to disbelieve the various citations that show that downwind VMG can be greater than wind speed, but does not provide any citation to indicate why downwind VMG cannot be greater than wind speed.

In my view, the article, as it stands, correctly presents the facts. I would propose that we stop this discussion and leave the article as it is, unless someone suggests specific edits or provides new citations.--Gautier lebon (talk) 16:20, 2 March 2010 (UTC)

Gautier Lebon. Some reminders are apparently needed: Wikipedia is not for unverifiable material. Wikipedia is not a democracy. Wikipedia is not a soapbox. 202.180.115.243 (talk) 20:31, 3 March 2010 (UTC)


 * Dear 202, you are correct. But everything that I (and others) have added is verifiable. You claim that the reliability of those citations is low, but that is a different matter.  We have provided citations, you have not.  If Wikipedia is not a democracy, then what is it?  Can a single person prevent verifiable information from being presented?  Regarding soapboxes, again, I would urge you to refrain from making statements that might be considered to be ad-hominem attacks.  As I've said before, I think that we are all working here in good faith to try to make Wikipedia the best possible source of information.--Gautier lebon (talk) 16:28, 4 March 2010 (UTC)

Nor is Wikipedia an Inquisition or a Court of Law. If we are arguing whether or not USA-17 can make VMGs upwind and downwind that are multiples of the True Wind Speed, then there are ample verifiable (at least to normal non-Inquisition and non-Court of Law wiki standards) cites available that testify to that fact. I have personally heard navigator Matteo Plazzi, and design team leader Mike Drummond say so and have provided links to verifiable reports of their saying so. I can't see the basis for argument. Since no one in this debate has suggested any edits to the article, I suggest we regard the matter as closed.--Paul (talk) 23:50, 3 March 2010 (UTC)


 * "ample verifiable" - no there aren't - there are only verifiable approximate reports from remote (to boat) sensing for wind speed and direction, none for actual wind shear, and conflicting referenced data for even a method to estimate wind shear.
 * "have provided links to verifiable reports of their saying so" - no you haven't, you've submitted unverifiable anecdotes.
 * No matter should be considered "closed" on any subject (including this one) by some happy consensus reached between "interested parties/contributors". 202.180.115.243 (talk) 01:48, 4 March 2010 (UTC)
 * Dear 202.180.115.243, The first set of hard verifiable facts are the times that USA 17 took to sail from mark to mark in each of the three races and hence the VMGs to each mark and the VMG over the complete course can be calculated. Do you agree? (Please also register as a Wikepedia user) Boatman (talk) 08:44, 4 March 2010 (UTC)


 * Yes I agree. The VMG calculation (to course) can be calculated. But VMG to wind speed cannot - as it seems that verifiable data is not available, and may never become available.  The problem with offering unverified wind speed/direction data with VMG (to course) based on use of that data in calculation is compounded by this being referenced elsewhere on WP such as the Sailing faster than the wind "it sailed 20 nautical miles downwind in 1 hour 3 minutes, so its velocity made good downwind was about 2.7 times windspeed" presented as if that was verified.  I reject answering the question "so do you not believe downwind VMG progress faster than the wind is possible" - my answer would be an opinion.  There seem to be two conflciting and disputed hypothesis.  The first is that force to provide downwind progress is the result of transfer of kinetic energy from wind to boat, and that as relative wind velocity (with boat VMG to wind direction) is zero when boat velocity (VMG to wind direction) is the same as wind speed, then there is no differential in force and no kinetic energy transfer.  The second is that as long as speed over ground at a vector to real wind direction is maintained, then the vector of apparent wind (when VMG to wind speed is reached and even exceeded) always remains above 0, and from that it is concluded that force (relative to boat direction) can be applied by the wind in order to continue accelerating the boat beyond wind speed (VMG).  It seems that both hypothesis cannot be correct - and "consensus" does not make the decision.
 * Verifiable evidence would be very helpful. Above I questioned how the "Greenbird" data is interpreted.  My criticism and summary that the data is inconclusive is very sound, regardless of how unpalatable that seems to have been to some contributors.  My criticism of (mis) interpretation of USA 17 race data is the same - there is real doubt on true wind speed and direction, and it seems that there's great reluctance to accept this fact, and an apparently non-neutral determination to "cherry pick" data in an attempt to discredit any suggestion that wind speed and direction were anything other than being within parameters to allow interpretation of USA 17's truly outstanding performance, as "proof" that downwind (VMG to wind speed) was achieved. I haven't checked all the data on the Sailing faster than the wind page, but there seems to be a pattern in evidential data, where great attention is paid to method used for verifying speed over ground, but there's little (or often nothing at all) presented to show methodology for ascertaining wind speed and direction.
 * Just to add to the above, if you do the maths to calculate apparent wind speed and direction vs known real wind speed and direction on boats travelling on a downwind tack at a speed over ground several times real wind speed, a very small difference in apparent wind angle, and a very small difference in apparent wind speed makes a very large difference in back-calculation of vectors to estimate VMG to wind speed. In other words, it's potentially very problematic to use data observed from the boat on it's own, or to cross-check validity of data observed remotely. 202.180.115.243 (talk) 23:29, 4 March 2010 (UTC)


 * Dear 202, thank you for having ordered the book by Bethwaite. As you will see, he provides ample evidence that downwind VMG greater than 1 was acheived many years ago by 18-foot skiffs.  He also explains how that was done.  Hopefully, after reading that book, we can continue to work together to improve this part of Wikipedia.  You are correct that the article on sailing faster than the wind is weak regarding actual wind speed data: that's because people don't publish it.  So I agree that it is hard to know if VMG was 1.5 or 2.5 times windspeed.  I think that I accounted for that by inserting "approximate" everywhere.--Gautier lebon (talk) 14:26, 5 March 2010 (UTC)


 * 202 states that there are two mutually exclusive hypotheses: the first is that force to provide downwind progress is the result of transfer of kinetic energy from wind to boat, and that as relative wind velocity (with boat VMG to wind direction) is zero when boat velocity (VMG to wind direction) is the same as wind speed, then there is no differential in force and no kinetic energy transfer. The second is that as long as speed over ground at a vector to real wind direction is maintained, then the vector of apparent wind (when VMG to wind speed is reached and even exceeded) always remains above 0, and from that it is concluded that force (relative to boat direction) can be applied by the wind in order to continue accelerating the boat beyond wind speed (VMG).  Neither hypothesis is exactly correct or relevant, although the second one is closer to being right.  As explained at sailing_faster_than_the_wind, what drives the boat is the force exerted by the wind on the sails, and what limits its speed is the friction from the surface, the friction from the apparent wind, and the angle at which the boat can sail with respect to the apparent wind.  The transfer of kinetic energy from wind to sails is what creates a force that moves the boat.  Of course there is zero transfer when the relative velocity of the boat with respect to the wind is zero.  But what counts is the apparent wind.  Sails see only apparent wind.  The force is generated only by the apparent wind.  And, as explained in sailing faster than the wind (but apparently not clearly enough), there can be a strong apparent wind even when the boat has a downwind VMG greater than the true wind speed.  I am going to expand the sailing faster than the wind article, hopefully it will become clearer.  By the way, this is not my original idea, it is taken from the various citations that appear at the beginning of the article on sailing faster than the wind].--Gautier lebon (talk) 14:26, 5 March 2010 (UTC)


 * Here's my proposal for ending this discussion. In the early part of the article I would change: exhibits very high performance being able to sail at 2.0 to 2.5 times the true wind speed to exhibits very high performance being able to sail at 2.0 to 2.5 times the true wind speed and can achieve VMGs of 1.5x upwind, and greater than that downwind and use BOR sailing team press conference February 9, 2010 (see Matteo Plazzi @ 1:20) for the citation. Then, I propose calculations about VMG be removed from the Racing results section, as being superfluous. As to the veracity of Plazzi's statements, they are based on on-board instrumentation with the wind velocity being measured at the masthead, so they are very conservative. There is no doubt in my mind that both Alinghi 5 and USA-17 can achieve VMGs in excess of the wind speed. It has been documented that the 1988 Stars & Stripes America's Cup boat was capable of 1.4x TWS VMG downwind, and these boats have superior performance. --Paul (talk) 23:51, 4 March 2010 (UTC)

Dear 202, I thought more about your hypothesis which, if I understand it correctly, is that downwind VMG cannot exceed true wind speed. If you work out the trigonometry, this means that VMG must be less that 1/cos(gamma) times wind speed, where gamma is the angle between dead downwind and the course (that is, gamma = 0 if dead downwind). In terms of course with respect to the upwind mark, this means that VMG, in terms of multiples of wind speed, would be limited to 1 for 180-degrees (dead downwind), 1.1 for 155, 1.22 for 145, 1.41 for 135, 2 for 120, 2.9 for 110, 3.9 for 105, 5.7 for 100, and infinite for 90. Of course infinite is not possible, because friction and the limits of how close the boat can sail to the apparent wind will come in. So your hypothesis is that VMG, as a multiple of wind speed, must be less than the minimum of the numbers given at Sailing_faster_than_the_wind and the numbers given above. But your hypothesis is falsified by published polar charts and by information on iceboats, which can go 5 times faster than the wind while sailing lower than 100 degrees off the wind. I realize that you claim that all those citations are unreliable and incorrect. But the fact remains that there are citations that contradict your hypothesis. Also, there should be a physical explanation to support your hypothesis: what physical phenomenon limits to boat to VMG=1? As noted above, it cannot be the wind, because what counts is the apparent wind, and that would not limit VMG to 1. Please also note the following quote from ThinAirDesigns, who is apparently a graduate student in aeronautics: "Most involved here in these discussions acknowledge that it's possible to steady state sail a traditional sailing rig at a fixed angle to the wind where the downwind VMG of the craft is greater than 1x windspeed (even 2x, 3x ...). Those who do not agree with this should review the data collected by NALSA (nalsa.org) on the topic." (see Talk:Sailing_faster_than_the_wind). As stated on their web site, several students, and a professor, believe that it is even possible to build a device that will prove that it is possible to progress dead downwind faster than the wind, see. So, if your hypothesis is correct, then (1) a lot of people have gone to a lot of trouble to fabricate false or misleading reports and (2) many people, including graduate students and professors, have been fooled into believing the impossible.--Gautier lebon (talk) 10:52, 6 March 2010 (UTC)


 * "VMG, in terms of multiples of wind speed, would be limited to 1 for 180-degrees (dead downwind), 1.1 for 155, 1.22 for 145, 1.41 for 135, 2 for 120, 2.9 for 110, 3.9 for 105, 5.7 for 100, and infinite for 90" thanks for working those out. Very handy. So... I need to find a boat that will go faster than 1.41x TWS @ 135 degrees off the wind. I'll bet a Windrider Rave will do that! --Paul (talk) 00:53, 7 March 2010 (UTC)

Following up on the last point, I'd like, once again, to explain how I got into this. Somebody told me that the 2010 Cup yachts would have downwind VMG faster than wind speed. I said it was not possible. He insisted. In order to prove him wrong, I searched the web. I could find nothing saying it was not possible (but maybe you can, in which case I would welcome the citation). On the contrary, much to my surprise, I found evidence to show that it was possible, and not even unusual. And I found the explanation of why it is possible. So I collected that information and published in on Wikipedia. I agree that it would be nice to have more precise data on actual wind speeds. But the people who sail these things don't bother to collect it or publish it because to them it is obvious that the boats are going much faster than the wind. Where I live, there are many people who fool around with high-performance multi-hulls. So I asked around, and nobody could believe why I would ask the question: everybody knew, from experience, that fast designs achieve downwind VMG greater than wind speed. Judging from your IP address, you (202) are in New Zealand, so you should also be able to ask people who know people who have actually seen these things go.--Gautier lebon (talk) 10:52, 6 March 2010 (UTC)

I've removed the reference and comments by Gautier lebon on the wind gradient page - see discussion there. I trust that this edit to the page indicating "the wind gradient is not sigificant for sailboats when the wind is over 6 knots" was a simple mistake in interpretation. 202.180.115.243 (talk) 03:38, 8 March 2010 (UTC)


 * If you did acquire Bethwaite's book, then you can verify that on page 11 he says "The primary characteristic of [winds with average speeds of about 6 knots or more] is that the change of speed with height is confined almost entirely to the one to two meters closest to the surface." I will comment further on this issue on the wind gradient page, which is where the discussion should take place. However, I will add here something that I should have mentioned earlier, but only thought of now. At the press conference after the first race, Bertarelli said that Alinghi 5 had not been correctly configured because they were expecting light air and instead found 10 knots of wind.  Since he was on the boat during the race, one can suppose that he was referring to the wind speed he saw on the boat's instruments.  That wind speed was presumably measured at the masthead.  Is there any citation that would support the statement that, during the races, the wind speed at the masthead was greater than 10 knots?--Gautier lebon (talk) 12:50, 10 March 2010 (UTC)


 * My recollection is that Bertarelli said "17 knots" (this was at the post-race press conference) and Butterworth was quoted as complaining about "18 knots" If this was true, it certainly was at the masthead, and was probably a gust. There was a lot of discussion on the sailing bulletin boards about this seeming incredible, as it didn't look windy at all when watching the races, and the boats never got over 30 knots which they easily would have done with that much wind.--Paul (talk) 14:12, 10 March 2010 (UTC)


 * My disctinct recollection was that Ernesto said "10 knots" at the post-race press conference, but I wasn't quite right. The America's Cup web site has verbatim quotations from the press conference.  Ernesto actually said "12 knots", the full quote is Ernesto Bertarelli (SUI), helmsman and team president Alinghi (SUI): "For sure at the start after the penalty it felt good they were stopped we could gybe and start. The wind changed quite rapidly. We had six or seven knots during the pre start and right off the start we were surprised with the wind coming in so strong, so quickly, 12 knots, but we thought we were doing good. But they caught up. We had to make a sail change which slowed us, but they were fast today and the wing seems to be quite a weapon." (see ) If Brad was serious when he was complaining about 18 knots, I'd like to ingest the same substances, assuming they are legal.  Even at the masthead, there couldn't have been that much, otherwise the sea would have shown many more crests.  When you look at the video, it looks like Beaufort 3 at most.  Regarding wind gradient, please see the citation that I've added there: it cannot have been very significant.--Gautier lebon (talk) 13:45, 11 March 2010 (UTC)


 * I remembered where I saw the 18 knots comment, it was this interview with Loick Peyron--Paul (talk) 15:05, 11 March 2010 (UTC)


 * Indeed, and he says 14 knots for race 2. Again, the state of the sea does not correspond to those numbers.  Maybe he was referring to the apparent wind, not the true wind?  In any case, I don't think that we should change the article to accomodate this discordant statement.--Gautier lebon (talk) 11:14, 12 March 2010 (UTC)

As far as paragraph above commencing "dear 202". I'm not interested in arguing the physics, especially here, except to remind you that there are very clearly two conflicting hypothesis, and that it's disingenuous to refer to the one you disagree with as "yours" referring to me. Yes, the data is weak on wind speed and direction data for all evidence I've seen presented claiming to show that downwind VMG progress faster than the wind is achievable. If you are favouring a certain hypothesis, then you're not going to find evidence in incomplete data, and you should expect to be challenged when you do. 202.180.115.243 (talk) 03:38, 8 March 2010 (UTC)


 * Dear 202, indeed there are two hypotheses. Since you have not given any citations that mention the hypothesis that downwind VMG cannot exceed windspeed, I called that hypothesis "yours", but I'm happy to use any label that you suggest.  For this comment, I will refer to it as hypothesis H0.  If I understand your comment about wind gradient correctly, you have now acquired a copy of Bethwaite's book, so I presume that you have found the polar charts that show that downwind VMG can be greater than wind speed.  Thus H0 is falsified.  H0 was based on the premise that that "force to provide downwind progress is the result of transfer of kinetic energy from wind to boat, and that as relative wind velocity (with boat VMG to wind direction) is zero when boat velocity (VMG to wind direction) is the same as wind speed, then there is no differential in force and no kinetic energy transfer".  Since H0 has been falsified, we should try to understand what might be incorrect in that premise.  What is incorrect is the assumption that when boat velocity is the same as wind speed, then the relative wind velocity must be zero.  As explained elsewhere, what counts is the apparent wind, and the apparent wind can be greater than zero even if downwind VMG is greater than windspeed. So there is a transfer of kinetic energy from the wind to that boat, even when the downwind VMG is greater than windspeed.--Gautier lebon (talk) 12:39, 10 March 2010 (UTC)


 * Dear 202, For the fifth (or is it sixth?) please will you register as a wikipedia user so that your opinions and evidence will be given the recognition that they possibly deserve. It will also give readers the opportunity to talk to you via your 'talk page'. It is apparent that your ambiguity is causing frustration. Thanks, Boatman (talk) 19:51, 8 March 2010 (UTC)
 * Dear 202, The content that you seem to be objecting to reads:- "Winds were 6 to 9 knots. USA reached the windward mark in 59 minutes, so its velocity made good was about 13.2 knots, about 1.65 times wind speed. The course was a triangle, so the velocity made good downwind was only 11.5 knots, about 1.4 times wind speed. USA averaged 26.8 knots, about 3.35 times the wind speed, on the faster first triangular leg". Unless I misunderstand, you have objections which may be totally valid but I cannot find your recommendations/changes to the statement above. Please would you now be constructive and make your proposal on what this should say. We value your recommendation but opinions and defense of theory does not progress the accuracy of the article. It is time for you to be specific (and register as a user) Thanks,  Boatman (talk) 22:04, 8 March 2010 (UTC).

Infobox
Would this article benifit from an infobox? infobox ship is available to use for this article if needed. Mjroots (talk) 18:18, 16 February 2010 (UTC)
 * Yes, it certainly would and would seem to be appropriate and keeping with the context of other ships. 24.188.207.20 (talk) 02:19, 18 February 2010 (UTC)

where will it wind up?
Anyone have any info on what will happen to the USA 17 now that AC33 is over? 24.188.207.20 (talk) 02:43, 27 February 2010 (UTC)

Race Details
Re Trappist's query: please leave the race details in this article, they important information regarding this boat. The results also appear in the 2010 Cup article, but in a different way, so they should be retained here.--Gautier lebon (talk) 07:16, 26 April 2012 (UTC)


 * I dispute the need for highly specific race details in an article about a yacht, even though the yacht's sole purpose for existence was the described race. You have said that the race details are important. What you have not said is why they are important.


 * USA 17's article is one of many articles that describe contending America's Cup yachts. Very few of those articles include detailed race analysis like that included in the USA 17 article. A strikingly similar detailed analysis of the 2010 America's Cup races also appears in the Alinghi 5 article. A reader who is interested in the 2010 America's Cup reads the articles about the contenders and quickly discovers that both articles contain significant amounts of material that has simply been copied from one article to the other.  Where we have essentially duplicate material, the maintenance task grows two-fold because when something is changed in one article, it must also be changed in the other.


 * The detail in §Racing results (and Alinghi 5 §Racing results) amounts to lists of facts and figures stitched together with a few words that don't make for a good narrative. These race details are better placed in a single location as part of 2010 America's Cup §Races where they can tabulated for easier understanding by those of us who aren't schooled in the esoterica of sail powered yacht racing.


 * --Trappist the monk (talk) 14:22, 26 April 2012 (UTC)


 * I think that the race details are important because these are the first (and maybe only) reliable published data showing that high-performance catamarans sail faster than the wind, even downwind. There aren't many sailing yachts that can do that, so the performance of these boats is very significant information.  You are correct that the details appear in several places, but I don't see anything wrong with that: a reader who is interested only the the yacht and its performance shouldn't have to hunt through an article on a different topic to find out what the performance is. I see that you have done the maintenance (and many thanks for that), so I don't think that maintenance will be much of an issue in the future.  Let's see what other editors think.--Gautier lebon (talk) 09:10, 27 April 2012 (UTC)

External links modified
Hello fellow Wikipedians,

I have just added archive links to 4 one external links on USA 17. Please take a moment to review my edit. If necessary, add after the link to keep me from modifying it. Alternatively, you can add to keep me off the page altogether. I made the following changes:
 * Added archive https://web.archive.org/20090823170055/http://www.ggyc.com:80/09%2008%2010%20GGYC%20Press%20Statement.pdf to http://www.ggyc.com/09%2008%2010%20GGYC%20Press%20Statement.pdf
 * Added archive https://web.archive.org/20081115225027/http://bmworacleracing.com/en/news/archive/overview.html?track.refer=/en/news/overview.html&track.type=sn to http://bmworacleracing.com/en/news/archive/overview.html?track.refer=/en/news/overview.html&track.type=sn
 * Added archive https://web.archive.org/20100103012847/http://bmworacleracing.com/en/news/archive/index.html?track.refer=/en/frame/overview/top_americas_cup.4ml&track.type=hn to http://bmworacleracing.com/en/news/archive/index.html?track.refer=/en/frame/overview/top_americas_cup.4ml&track.type=hn
 * Added archive https://web.archive.org/20110711001558/http://www.fillmedia.com/americas-cup-2010-33rd-americas-cup-2010-race-2-live-stream-7730.htm to http://www.fillmedia.com/americas-cup-2010-33rd-americas-cup-2010-race-2-live-stream-7730.htm

When you have finished reviewing my changes, please set the checked parameter below to true to let others know.

Cheers.—cyberbot II  Talk to my owner :Online 11:01, 24 February 2016 (UTC)