From Wikipedia, the free encyclopedia
Jump to: navigation, search
          This article is of interest to the following WikiProjects:
WikiProject Sailing (Rated C-class, Top-importance)
WikiProject icon Sailing is within the scope of the WikiProject Sailing, a collaborative effort to improve Wikipedia's coverage of Sailing. If you would like to participate, you can visit the project page, where you can join the project and see a list of open tasks.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 Top  This article has been rated as Top-importance on the project's importance scale.
WikiProject Meteorology (Rated C-class, Low-importance)
WikiProject icon This article is within the scope of WikiProject Meteorology, a collaborative effort to improve the coverage of Meteorology on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 Low  This article has been rated as Low-importance on the project's importance scale.
WikiProject Water sports (Rated C-class, High-importance)
WikiProject icon Sailing is within the scope of the WikiProject Water sports, a collaborative effort to improve Wikipedia's coverage of Water sports. If you would like to participate, you can visit the project page, where you can join the project and see a list of open tasks.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 High  This article has been rated as High-importance on the project's importance scale.

Downwind faster than the wind[edit]

This paragraph requires revision:

Some extreme design boats are capable of traveling faster than the true windspeed on some points of sail and can even sail downwind faster than the wind, although this is not intuitively obvious[1][2]; iceboats can sail both upwind and downwind at speeds far greater than the wind.[3] Americascupfreak (talk) 20:41, 10 June 2014 (UTC)

1) Boats that are not "extreme" in design are capable of travelling faster than wind speed on a beam reach.

Indeed, this is correct, and the text should be modified accordingly. Please take a look at the proposed new article User:Gautier_lebon/Sailing_faster_than_the_wind and let me know what you think of that.--Gautier lebon (talk) 16:49, 8 December 2009 (UTC)

2) Iceboats may have been demonstated to sail on a downwind part of a course (which by definition is of limited duration) from "A" to "B" faster than the wind on a VMG (to wind speed) basis, but sustained downwind faster than the wind progress on a fixed bearing is not possible. —Preceding unsigned comment added by (talk) 00:46, 1 December 2009 (UTC)

That's what I thought too, until I looked up various references. Please take a look at the proposed new article User:Gautier_lebon/Sailing_faster_than_the_wind and let me know what you think of that. Indeed, usually downwind tacking will be required in order to go faster than the wind, but it is possible to construct a wind-driven cart that can go dead downwind faster than the wind, see the explanation and references in my draft article cited above--Gautier lebon (talk) 16:49, 8 December 2009 (UTC)
Absolutely. "Intuitively obvious", although the writer may not realize, means "it's obvious to me, I imagine it's obvious to others, so I don't want to explain it." As a professional editor, my response is "If it's obvious, then don't say it. If it might not be obvious to some substantial part of the audience, then explain it, don't tell people what amounts to 'Figure it out for yourself.'"
"Some extreme boat designs" belongs in a sports magazine, not an encyclopedia, where facts need to be verifiable. "Extreme" may mean something to the writer, but again, it may mean nothing to the general reader. (Me, for example. I couldn't guess what this means if you offered me free passage to Tahiti.) Cheers, Alpha Ralpha Boulevard (talk) 04:51, 6 December 2009 (UTC)

I'm not familiar with 'extreme' sailing machines, but I can see how moving faster than the true windspeed is possible while tacking downwind. What I can't see, is that you would arrive at a downwind mark faster than the windspeed would get you there if you just floated on it. In other words by deviating away at some angle you may get the 'rush' of going fast, but your VMG towards a directly downwind point, I think, will always be slower than the true wind speed from here to there. Is that right? If so it is a significant drawback, as few people sail just to get the rush of speed, most want to actually get somewhere, either to race to or to arrive at that point. --Nigelj (talk) 19:00, 8 December 2009 (UTC)

OK, I've just read your user-space article, and I see that I am right if we use an ordianry sailing machine. I think I;m right in the other two cases too, as I see the maths ran out long before the downwind speed-of-wind section. I believe that your 'huge spinnaker, negligible-drag towed generator' example has a kind of perpetual motion machine fallacy - if the towed generator is that small it won't make any difference, if its any bigger it'll slow the boat down more than it speeds it up. The downwind cart is the same - if you go at the exact speed of the wind, the propeller will stop. Nice try. --Nigelj (talk) 20:01, 8 December 2009 (UTC)
Dear Nigelj, I felt exactly as you did until I carefully studied various articles on the web. Please look at [1]. The reality of this device was debated, but in the end anybody can see that it is legitimate. For the debate, see [2] and [3], and please note that the initially skeptical physicist wound up admitting that he was wrong and that a wind-powered device can be built that will indeed sail dead downwind faster than the wind. The reason why this is not a perpetual motion machine is that the inherent energy in the wind is very large: if you can harness enough of it, you can do what you want. This is also explained at [4]. My motivation for writing the proposed new article was to assemble in one place the relevant references, precisly because most people would think that such things are impossible. Maybe my explanations aren't clear enough, but then I would appreciate suggestions on how to improve them.--Gautier lebon (talk) 09:30, 9 December 2009 (UTC)
Well if you motor your not sailing! End of story. You would not be sailing either if you have a windgenerator on your yacht charging your batteries while in port and later the batteries will power the yacht faster than the wind. Same thing, different approach. By the way, a yacht will point 45 deg to true wind not apparent wind. Prillen (talk) 10:46, 9 December 2009 (UTC)
A wind-driven machine cannot sail dead downwind faster than the wind using only sails. However, it can sail dead downwind faster than the wind using only energy obtained from the wind while moving (that is, it does not need to stock energy while in the port). Some sort of mechanical device can be used to transfer energy from the surface on which the machine is moving in order to increase the speed of the machine (e.g. the wheels on a sail-driven cart can drive a propeller). I'm not sure whether you (or others) have actually read the citations that I provided. If not, please do so. Regarding pointing, a yacht's sails see only apparent wind, not true wind. So a yacht can sail at a certain minimum angle with respect to the apparent wind. If a yacht can sail at 45 degrees off the apparent wind, then it cannot sail at 45 degrees off the true wind, because of the apparent wind shift induced by the speed of the boat. Boats that sail at 45 degrees off the true wind achieve that by being able to sail closer than that to the apparent wind (say about 35 degrees off the apparent wind.--Gautier lebon (talk) 08:26, 10 December 2009 (UTC)
Sorry, but as long you have to store energy for later use you can't claim to sail faster than the wind. And my point about about 45 degree wind is just a modern cruiser will tack within 90 degrees i.e. sail at 45 deg to true wind. Prillen (talk) 15:19, 10 December 2009 (UTC)
We are on the same wavelength now. As we all know, how high a keelboat can point depends on a lot of things, including quality of the sails and how clean the hull is. I've rarely sailed a keelboat that could tack within 90 degrees in light air, but I've come close to that in stronger winds, because the effect due to the apparent wind shift is relatively smaller. Anyway, you are correct to imply that my text should match more closely what is in the main article on sailing, and I will modify it accordinbly.--Gautier lebon (talk) 07:56, 11 December 2009 (UTC)
Also, please be careful to remember that this article is called 'sailing', so be careful about giving undue (or any) weight to 'wind-driven machines' that do whatever they do by any means other than actually sailing. --Nigelj (talk) 18:50, 10 December 2009 (UTC)
Yes, this is a good point. There is a difference between sailing properly speaking, that is, a device propelled by sails, and the broader notion of a machine that is propelled by the wind. I've modified my text to clarify this. And, in any case, I was not proposing to include my material directly in the article on sailing, I propose to create a new article.--Gautier lebon (talk) 07:56, 11 December 2009 (UTC)

It remains my opinion that the claim and reference to iceboats sailing downwind (VMG) faster than the wind requires qualification (ie that this is not possible on a single bearing) or explanation of the method - accelerating to a velocity much greater than wind speed on a "reach", then turning downwind with minimal frictional loss of forward momentum as is possible with an iceboat, trimming sails to minimise wind resistance while at faster (VMG) speed downwind than the wind, and repeating this action in sequence if required by the duration of the course, to achieve verified progress (VMG) faster than the wind. I made the mistake above (and corrected it) of repeating the common suggestion that progress downwind faster than the wind is possible with an iceboat with "tacking" (gybing). Tacking may be practically needed to go from mark to mark on a fixed course, but it is also possible to achieve downwind faster than the wind (VMG) progress by altering course as described without tacking.

This is a good comment, I will incorporate it.--Gautier lebon (talk) 10:32, 14 December 2009 (UTC)

With regard to the cart with propellor connected by gearing - claimed to demonstrate that indefinitely sustainable directly downwind faster than the wind progress can be made (by "spork33" and others in a clever internet hoax apparently designed to "double-cross" the "Mythbusters" TV programme), the explanation given is inadequate, and the demonstration (videos) of the cart(s) in action does not revoke criticism that the machine uses energy stored in rotational movement to accelerate for a finite duration once "released" at wind speed. It is not capable of reaching wind speed on it's own. Energy "pushing" the cart forward (via the prop) must always be less than energy "braking" the cart (through the wheels) at any velocity. Despite attempts to argue otherwise, the only source of energy for the cart to accelerate is kinetic energy of the wind, which reduces to nil when it is at wind speed. The machine described and demonstrated is a worthy addition to the Wikipedia page on Perpertual Motion Machines. —Preceding unsigned comment added by (talk) 05:59, 14 December 2009 (UTC)

I don't see any theoretical-physics reason why the energy pushing the care forward must always be less than than the energy braking the cart at any velocity. It is clear that the only source of energy is the kinetic energy of the wind. But there is no reason in theory why enough of that cannot be harnessed to go faster than the wind. The thought-experiment involving the intermittent use of a towed electrical generator and batteries shows that there is no violation of basic physical principles in imagining a device that can go dead downwind faster than the wind. I note that the initially skeptical physicist later admitted that the cart in the videos is not a hoax. I don't see any published reference that still suggests that it is a hoax.--Gautier lebon (talk) 10:32, 14 December 2009 (UTC)
The towed electric generator thought experiment is a similar device. I'm deeply suspicious of the initially skeptical physicist who "changed his mind". The discussion became very heated at times and unnecessarily complex. Always it was accompanied by video seeming to demonstrate that the device "worked" as claimed, but these videos never clearly demonstrated that sustained progress faster than wind could be made. The demonstration of "duration" of stored energy release of intertia in the rotating componenents - by lifting the cart and measuring the time until the propellor stopped spinning due to frictional losses - was flawed, as it did not include the significant effect of momentum from forward movement of the cart which was transferred by gear drive from the wheels to the prop. It's hard to grasp forces/energy interactions in a dynamic moving system. I have drawn a diagram here [5] which I hope makes things more evident.
From looking at that diagram, several things should be clear:
1) That the energy "harvested" from the wheels must create more "braking force" than the "driving force" produced by the energy used by the propellor, regardless of gear ratios or velocity of the cart.
2) That in the demonstration, where the cart is held on the belt (equivalent to artificially accelerating the cart to wind speed in a wind tunnel), there is more kinetic energy put in to the total system (the device) than is required to accelerate the mass of the device to wind speed.
3) That this "extra" energy is stored as momentum in rotating components.
4) Release of that stored energy allows the device to accelerate when released. (that's how it "seemed" to work)
5) The energy will be "used up" (lost to friction), and the device will decelerate to below wind speed. (that was never allowed to be seen in videos)
6) That the device could never accelerate to wind speed unaided - exactly the same constraints apply as to any boat with a sail, sailing directly downwind.
I do believe that the device is worthy of inclusion in Wikipedia somewhere, perhaps to the Perpetual Motion Machines page, perhaps a separate page. It was clever - but probably a hoax rather than a mistake. To work as claimed, accepted laws of physics would be broken.
Note that this doesn't proclude making a device which could make sustained downwind (VMG) progress faster than the wind. Iceboats already do it. But not constantly - as when reaching to pick up forward momemtum the VMG progress is temporarily slower than the wind, and they cannot sail directly downwind faster than the wind on a continuous and sustainable basis. But between point A and a directly downwind point B, theoretically possible and evidenced by GPS plots. I was thinking to make a demonstration device to try and "prove it" in a controlled indoor setting, but it would be quite a complex device, and a bit pointless as the evidence from iceboats has already demonstrated that the theory works. —Preceding unsigned comment added by (talk) 23:08, 14 December 2009 (UTC)
I agree. 'Achieving a speed greater than the windspeed', is perfectly possible; and the momentum, or kinetic energy, so created can be used to coast temporarily directly downwind at such a speed too. This is very different to actually arriving under sail at a distant downwind point before molecules of air that were around you when you started. That is what I would understand by 'sailing downwind faster than the wind', and it is not possible without using some previously-stored energy. --Nigelj (talk) 12:54, 15 December 2009 (UTC)

Dear all: again, I thought as you did until I researched the matter. If you look at the polar diagram for the 18ft Skiff at [6], you will see that an the 18ft Skiff can indeed tack downwind faster than the molecules of air. And an iceboat can do so much faster. There is no need for previously-stored energy. If I understand the rules of Wikipedia correctly, one is supposed to report on what has been published elsewhere, not to provide original research. My objective is to summarize various articles and sources on sailing faster than the wind. Unless I misunderstand the rules, criticism of those articles is original research that does not belong in Wikipedia. But I do agree that it should be reported that there is some skepticism, and I've modified my user page draft to reflect that.--Gautier lebon (talk) 13:32, 16 December 2009 (UTC)

Well,in terms of WP:RS and other policies, we include things based on their weight in reliable, secondary sources. Someone's homepages on certainly don't qualify as that, nor do videos on youtube. The publication Catalyst sounds as if it might, until you read, "Opinions expressed are the author’s, and not those of AYRS ... Contributions are welcome from all." That does not sound like a reliable peer-review process at work. I also cannot find in that author's maths any conclusion about VMG downwind being greater than the windspeed - it all seems to focus on maximum speed achievable in whatever direction, and choosing the angle to maximise VMG, but does not contain the text you want that I could see. But it doesn't matter, as it's not a 'reliable source' anyway. I think the best we can say is that there is controversy and individuals continue to try to prove it, but others still disagree with their findings and conclusions (with refs on either side). What we need, to state this as a fact, is a textbook, published by a mainstream publisher (they have review processes) or an article in some other mainstream publication that does stand by what they publish, to actually say it. --Nigelj (talk) 14:32, 16 December 2009 (UTC)
I take it that you both agree that the device presented by "spork" and others does not work as claimed in theory, and has not been demonstrated to work in experiment, so can be eliminated. There seems to have been consensus between some people involved in discussion elsewhere that if the "spork" device can do it, then iceboats can do it, and vice-versa. There are some documents here [7] also claiming to show downwind faster than the wind (averaged point A to point B, VMG) performance recorded by GPS. But there are flaws in this data. One is that there's no certainty that wind direction and velocity is recorded accurately. Another is that speed of the boat after rounding the top mark does not drop to below wind-speed according to recorded GPS data - so some energy stored as momentum from the boat's upwind tack is carried through. This data was from 2004. Hand-held GPS have become more affordable, much more common, and much easier to use, so it's surprising that some more recent data isn't commonplace - or at least more easy to find. —Preceding unsigned comment added by (talk) 19:53, 16 December 2009 (UTC)
What your source say: It's possible to do a VMG downwind faster than the wind. But thats not the point. Thats well known I guess, but you (Gautier lebon) claim it is possible to sail dead downwind faster than the wind. And that's the problem – it is not possible. Prillen (talk) 07:46, 17 December 2009 (UTC)

Thank you for the good comments. I do agree with Nigelj's comment that the article should mention that there is some controversy. But, again, I haven't found any articles anywhere (peer reviewed or not) that suggest that sailing downwind faster than the wind is not possible. It seems to me that the following statements are not controversial and are amply supported by reliable citations: (1) boats can sail faster than the wind on some courses, notably at 90 degrees to the wind; (2) some boats can make good downwind faster than the wind, by tacking downwind, notably iceboats and the 18ft Skiff (and in February 2010, when the 2010 America's Cup takes place, we will have reliable published actual data on velocity made good downwind by high-performance multihulls); (3) no physical law is violated by a boat that makes good downwind faster than the wind. In addition, the following statements seem correct to me: (4) it is possible to conceive of a theoretical machine that would use devices other than sails to capture the energy of the wind in order to sail dead downwind faster than the wind; (5) some people claim to have built and demonstrated such a device, but there is some skepticism regarding the legitimacy of that claim.--Gautier lebon (talk) 08:24, 17 December 2009 (UTC)

By the way, I didn't start by trying to claim that it is possible to sail dead downwind faster than the wind. It is quite the opposite: I was trying to prove that such a thing is NOT possible. What happened is that I got into a discussion with a very experienced sailor regarding the peformance of the giant multihulls that will race in the 2010 America's Cup. He told me that those boats would sail downwind faster than the wind. I scoffed. He insisted. So I decided to prove him wrong by finding polar curves that would show that no boat can go downwind faster than the wind. Much to my suprise, I found exactly the opposite. So I started to think about the physics and to do more research. You've seen the results. For what it is worth, I've asked a physicist to look at my draft page, and he says that it seems correct.--Gautier lebon (talk) 08:24, 17 December 2009 (UTC)

If you believe that it is not possible that a device could sail dead downwind faster than the wind, then you must believe that such a device would violate some basic law of physics. But I don't see which one would be violated, so I would appreciate specifics comments on that.--Gautier lebon (talk) 08:24, 17 December 2009 (UTC)

For directly downwind faster than the wind, powered by the wind, it is absolutely violating laws of physics. Even if a device could be constructed that had no frictional losses, then it is constrained to sailing downwind almost as fast as the wind, as the energy required to overcome the intertia to accelerate the device to wind speed is always greater than the kinetic energy available that can be transferred from the wind to the device. It can get closer and closer, but never quite to wind speed, unless mass of the device was nil, or size of the sail (and amount of steady wind!) was infinite. The device cannot accelerate to and beyond wind speed directly downwind using the wind as sole source of energy. But I agree with you that a device can be constructed that can make VMG downwind progress directly downwind faster than the wind. Take the device with no frictional losses, accelerate it to well beyond windspeed (iceboats can do 5x wind speed on a reach), then turn to point it directly downwind, and it then travels directly downwind much faster than the wind, powered by the wind, and it can do this indefinitely. In reality, add some frictional losses and it's still possible - unless the combined frictional losses make it impossible. It's not possible in my 8 metre sloop, but in an iceboat or the giant America's Cup multihulls, or 18 foot skiffs perhaps, there's no fundamental reason why it isn't possible. But where is the reliable data to show it has been done? —Preceding unsigned comment added by (talk) 09:39, 17 December 2009 (UTC)
You say "the energy required to overcome the intertia to accelerate the device to wind speed is always greater than the kinetic energy available that can be transferred from the wind to the device". This is not obvious to me. Again, take the thought-experiment of the boat with a very large spinnaker that tows a propeller-driven electric power generator behind it. Theoretically, there is no reason why you cannot use a spinnaker that is sufficiently large to overcome the drag from a generator that provides significant energy. Store that energy in batteries, then drop the sails, and use a propellor to sail faster than the wind. Your average VMG dead downwind can be faster than the wind speed. Of course this is not achieved with sails alone. But I don't see what physical law would be violated by such a machine.--Gautier lebon (talk) 12:12, 18 December 2009 (UTC)
Regarding what has actually been achieved in by real boats or iceboats, I agree that it would be good to have more reliable data. In February, we will have the actual data from the 2010 America's Cup. Does anybody seriously believe that those boats will not make good faster than the wind on the downwind run?--Gautier lebon (talk) 12:12, 18 December 2009 (UTC), that is a very good explanation of the physics. But don't go soft at the end! If you accelerate to 5x windspeed on a reach, then turn into a measured, downwind course, and remain going faster than the wind for a while, that means nothing about sailing downwind faster than the wind. You are simply entering the timed course with previously-stored energy. You might as well allow batteries that were charged the night before and an electric motor, or a diesel engine with 40-million year-old sunlight for power. Starting from A, using no stored energy from before, and arriving dead downwind at B faster than the wind from A to B at the time is impossible.
As I've pointed out before, the polar chart for the 17-foot Skiff [8] shows that it can start at a standstill and tack downwind, arriving at the downwind mark faster than the wind. That is, it makes good 14 knots downwind in 10 knots of wind. That is no more impossible than it is to sail on a reach faster than the wind.--Gautier lebon (talk) 12:12, 18 December 2009 (UTC)

The polar chart for 18 foot skiff shows boat speed of about 7 knots directly downwind (180 degrees) and about 14 knots at about 145 degrees. Now that's claiming around (a little less than) 12 knots (VMG) progress directly downwind (not 14 knots - that is boat speed). On a constant bearing of ~145 degrees, that is not possible, an error has been made in the polar chart. The "bulge" around 145/215 degrees is surely (claimed/estimated) speed with spinnaker set - and as such, either speed stated or angle to the wind must be incorrect. The original reference is to a book published in 1996 (The Symmetry of Sailing / Ross Garrett / Sheriden House) - predating GPS with selective availability off, and common availability of small hand-held GPS units. It is almost certain that the information is incorrect. Furthermore, it is not referenced here [9] and if referenced on the sailing page, a comment should be added that the reliability of the data is disputed. —Preceding unsigned comment added by (talk) 06:58, 19 December 2009 (UTC)

You are correct, the polar chart for the 18-foot skiff shows velocity made good of 12 knots, not 14. I made a trascription error. It is indeed possible, and there isn't necessarily an error in the chart. I realize that I didn't explain things clearly enough. Please look at the new section User:Gautier_lebon/Sailing_faster_than_the_wind#Sailing_on_a_broad_reach. The energy available in the wind is essentially unlimited compared to what is required to propell an iceboat (or a high-performance boat). Energy is not the lim[iting factor. What counts is the force produced by the sails compared to the force exerted by the surface. There is a very good explanation at the bottom of the page [10]. Surely that can be considered a reliable source? I also found several other new citations, which I think can be considered reliable, see the footnotes at the end of the introductory paragraph of my draft article. The 18-foot Skiff never uses a spinnaker because it can always accelerate enough so that the apparent wind is ahead of its beam. Same as an iceboat. Same as the giant multihulls that will be used to race the 2010 America's Cup: they don't have spinnakers because the apparent wind will never be behind the beam.--Gautier lebon (talk) 16:04, 21 December 2009 (UTC)
So, at 145 degrees (with wind on the port side) the polar chart claims 14 knots true speed, about 12 knots VMG speed downwind in 10 knots of wind. So the apparent wind direction moves foreward, and apparent wind speed drops, when accelerating at this angle. But that position indicated on the polar chart isn't possible as the apparent wind direction has shifted to about 2 knots on the starboard side. So the chart is absurd and clearly wrong. The 18 footers here use a type of spinnaker - asymetric "reacher". —Preceding unsigned comment added by (talk) 20:29, 21 December 2009 (UTC)
I don't understand your comment. The polar chart shows only boat speed and direction, not the apparent wind. The apparent wind is not 2 knots. See the vector diagram in the section "Why are eighteen footers always sailing upwind?" in the article at [11]--Gautier lebon (talk) 09:25, 23 December 2009 (UTC)
Gautier lebon, just be aware that everything you say in your middle post at 08:24, 17 December 2009 (UTC) is WP:OR and so, while interesting, inadmissible on Wikipedia articles. --Nigelj (talk) 12:19, 17 December 2009 (UTC)
Yes, I am aware of that, and was not proposing that anything like that be included in an article. But I thought that it was worth including in this discussion.--Gautier lebon (talk) 12:12, 18 December 2009 (UTC)
'If you accelerate to 5x windspeed on a reach, then turn into a measured, downwind course, and remain going faster than the wind for a while, that means nothing about sailing downwind faster than the wind'
It's quite possible to start from zero velocity, reach to gain speed faster than the wind, then turn downwind to "coast" during progress on the downwind leg. If distance lost (relative to windspeed, VMG to wind direction) during initial acceleration and "reaching" is less than distance gained when "coasting" at above windspeed, then (VMG) downwind speed faster than the wind is possible averaged over the duration of a course. It seems likely that this can be achieved with iceboats. But I can't find any evidence to show that it has been achieved. The iceboat GPS plots I have seen start with upwind legs, so momentum is always carried through the top mark. —Preceding unsigned comment added by (talk) 21:24, 17 December 2009 (UTC)
When you say "coast during progress on the downwind leg" you seem to be ignoring the effect of the apparent wind. There will be significant apparent wind, due to the speed of the boat, so the sails would have to be close hauled even on the downwind leg.--Gautier lebon (talk) 12:12, 18 December 2009 (UTC)
Yes agreed. Is that what this whole discussion has been about? In that case if we change the phrase to "Appearing to have sailed downwind faster than the wind" I would have agreed from the start. --Nigelj (talk) 21:38, 17 December 2009 (UTC)
I'm not sure what would be meant by "appearing". A boat starts from an upwind mark and reaches the downwind mark some time later. Thus it has a certain downwind VMG. The question is whether the downwind VMG can be greater than the windspeed. Either it sails faster than the wind or it does not. Or maybe we have an issue with terminology here. What I mean by "sailing faster than the wind" is "the boat's speed is greater than the wind speed". There is a separate phenonmenon, which is "the boat's speed make good downwind is greater than the wind speed". I take that that nobody disputes that boat speed can be greater than wind speed on some courses, in particular a 90-degree reach. I trust that everybody accepts that certain high-performance boats (and iceboats) can have downwind VMG greater than wind speed, by tacking downwind, even if they start at a standstill at the upwind mark. I agree that VMG on a dead downwind course cannot be greater than windspeed for a device that uses only sails. So, presumably, the only disagreement is whether, through the use of devices other than sails, it would be possible to build a machine that can use only energy from the wind in order to achieve VMG greater than windspeed while on a dead downwind course. Incidentally, I presume that everybody knows that a windmill-powered boat (with a propeller in the water) can sail directly into the wind, which is of course not possible for a boat that uses sails.--Gautier lebon (talk) 12:12, 18 December 2009 (UTC)
Yes, I think it is what it is all about - my original questions / statements at the commencement of this thread - particularly 2). There are several places in Wikipedia, where the claim is made - without qualifying the claim by stating "appearing to" as you suggest - that downwind (VMG) faster than the wind is possible, including the statement in the main sailing page : "Some high-performance boats are capable of traveling faster than the true windspeed on some points of sail and can even sail downwind faster than the wind[5][6]; iceboats can sail both upwind and downwind at speeds far greater than the wind." This needs to be deleted or further explanation provided. One of the links provided [12] is a hoax. Even the diagram of the device provided on that link completely ignores the "braking" force of driving the prop on the wheels. The device demonstrated on video has larger and heavier components than the original "spork" device - the duration of release of "extra" energy (than is required to propel the mass of the device to wind (belt) speed - so is artificially put in to the device in the video demonstration) is longer, so it appears to be even "more convincing" on a necessarily fixed length treadmill demonstration, but it is still the same hoax, and should not be referenced from the sailing page, except as a curiosity perhaps. —Preceding unsigned comment added by (talk) 05:16, 18 December 2009 (UTC)
You are correct, the reference [13] that appeared in the main sailing article should not appear there. I have corrected that mistake and provided the correct reference to support the statement in the main article. Thank you for having spotted that.--Gautier lebon (talk) 12:12, 18 December 2009 (UTC)
See above for comments on 18 foot skiff polar chart.

The argument seems to vacillate between inappropriate extremes of being a hoax, or a fringe theory about perpetual motion. But also, any subject that is under so much dispute does not belong in Wikipedia. What something "appears to do" is subjective, a perception based in ignorance, and inappropriate for an encyclopedia. The references cited were not professional, reliable sites that are subject to peer review.[14], [15], [16]. As such, the material and references were deleted. My honest mistake. I didn't consider this.[17] Alpha Ralpha Boulevard (talk) 05:32, 20 December 2009 (UTC)

Folks: it is not a fringe theory that sailboats can sail faster than the wind. That is a well-known fact. What some of you are finding hard to believe is that this can happen even if the boat starts off downwind. Please read the explanation at User:Gautier_lebon/Sailing_faster_than_the_wind#Sailing_on_a_broad_reach.--Gautier lebon (talk) 16:04, 21 December 2009 (UTC)

Oh, and P.S. before you go there, Gautier lebon, I worked for years at a NASA center specializing in aerodynamics. We regularly got letters from well-intentioned people who wanted us to explain how their elaborate theories for anti-gravity boots or faster-than-light drive were incorrect. The answer? It isn't NASA's job to disabuse people who have confused themselves with theory. Nor is it Wikipedia editor's job to do the same. There's plenty of material to be contributed to this article from published, reliable sources. Again, I was mistaken.[18] Alpha Ralpha Boulevard (talk) 05:56, 20 December 2009 (UTC)

Indeed, and I am trying hard to provide an understandable explanation of why and how boats can progress at speeds faster than the speed of the wind, by citing what sources I can find. I've found some more reliable sources now, please look at the latest version. For what it is worth, I did 2 years of physics at MIT before switching to mathematics and eventually got a PhD from Harvard in statistics.--Gautier lebon (talk) 16:04, 21 December 2009 (UTC)
Under the selection removed is another contentious paragraph:
"Some non-traditional rigs purportedly capture energy from the wind in a different fashion and are capable of feats that traditional rigs are not, such as sailing directly into the wind. One such example is the wind turbine boat, also called the windmill boat[5], which uses a large windmill to extract energy from the wind, and a propeller to convert this energy to forward motion of the hull. A similar design, called the autogyro boat, uses a wind turbine without the propellor, and functions in a manner similar to a normal sail [6]."
The page referenced for the Autogyro boat has been removed (it seems to have been a personal home page Yahoo/Geocities). The links to the wind turbine boat seem to come to a dead-end, with no real evidence that the device has been shown to work, and links to forums and discussion and a grainy video of a device that doesn't really show anything to substantiate the statement that they can sail directly in to the wind. (talk) 10:06, 20 December 2009 (UTC)
That material was a little closer to being on-topic, but again, there's so much "core" material of the sort that's available in standard texts that could be added to this Wiki article that at best, these kinds of things belong in their own article. I note, for comparison, that Automobile doesn't mention "generator", even though it's an essential part of most cars, nor does the rather technical Steam locomotive seem to mention anything about the secondary and tertiary functions of the motive power: To generate electricity for lights, and to heat passenger coaches. I.e., the articles focus on main functions only.
Noting that wind power on a sailboat can be used for other things than driving the vessel might be worth noting in passing, in a simple sentence, or with a link to another Wiki article, but as a developed topic is seems to complicate, rather than clarify, here. Regards, Alpha Ralpha Boulevard (talk) 15:21, 21 December 2009 (UTC)
This was my intent: to have a short sentence in the main article that would link to an entirely separate article.--Gautier lebon (talk) 16:04, 21 December 2009 (UTC)

Some of you have suggested that an iceboat could turn downwind and use its momentum (kinetic energy) in order to proceed downwind faster than the wind. Although this is theoretically possible, I doubt that it can be done in practice. As explained at the bottom of [19] an iceboat continues to accelerate when moving downwind because there is essentially no friction to stop it. The kinetic-energy approach is easier to understand if you use formulas. Let V be the windspeed, VB the boat speed, VMG the speed made good downwind, D the distance from the upwind starting point to the downwind mark, TR the time spent running downwind, and TS the time spent reaching to accelerate and accumulate kinetic energy. That is, suppose that the iceboat starts at the upwind mark, reaches back and forth for total time TS in order to attacin maximum V, then, when it is back at the upwind mark, turns dead downwind. We are interested in the speed made good downwind including the time required to build up the kinetic energy, that is, we start counting the time when the boat starts moving. So VMG=D/(TR+TS). But TR=D/VG. If VMG>V, then (if you work out the equations) V/VB+V*TS/D < 1. If you plug in realistic values, you will see that this is not likely to hold. But, again, what an iceboat does is not at all to use its momentum to go fast downwind. On the contary, it builds up momentum as it accelarates downwind because of the force of the apparent wind, which does decrease as it accelerates, but remains sufficient to accelerate the iceboat. See the bottom of the page [20].--Gautier lebon (talk) 16:04, 21 December 2009 (UTC)

Gautier lebon, the comments you added throughout this discussion today alternate between arguing that 'a boat can sail faster than the wind' and that 'a boat can sail downwind faster than the wind'. No one that I can see is disputing the former, it's the latter that we disagree about here. Boats sail across the (true) wind faster than the wind because of the trigonometry of doing so. If you put a tapered wedge into a tapered gap, you can (with enough force, and little enough friction) force the wedge out quite fast by closing the gap quite slowly. There must be a word for that, but it is just like gearing or leverage. Of course it normally is used mechanically in reverse, pushing in a tapered wedge, to apply large sideways forces slowly. Back to sailing, a boat or iceboat that cannot move sideways will shoot off quickly across the true-wind direction, until the apparent wind is so far ahead of the beam that friction and drag prevent further acceleration (as the sail inefficiency increases close-hauled). If you turn that boat downwind, all that gearing, or leverage, or cherry-pip-squeezing effect begins to deteriorate with every degree of turn. For every degree you go off the wind, the 'wedge angle' increases: the first few degrees may increase your SOG (even if already greater than windspeed) as available propulsive force increases, but your VMG downwind is still nowhere near windspeed, which is how the trigonometric 'gearing' is working at these angles, to enable SOG above windspeed. As you approach pointing directly downwind, the trigonometric magic totally disappears and you end up, at best, 'floating' at windspeed with your biggest sails up. At no point in this 90 degrees of possible course angles does your VMG directly downwind exceed windspeed. All of this assumes a long course so that momentum gained on the beam reach is not just used to coast downwind significantly. If all you mean is that the momentum of a fast reach can enable you to coast quickly in any other chosen direction, then that is not, to my mind, "sailing" in that other direction.
Thank you for this good comment. Your analysis is perfectly correct up to the sentence "If you turn that boat downwind". You are correct that the "cherry-pip-squeezing" effect is diminished on a downwind course. But it is not zero. Please read carefully my explanation at User:Gautier_lebon/Sailing_faster_than_the_wind#Sailing_on_a_broad_reach and the references. Since the "cherry-pip-squeezing" effect is not zero, it can produce enough force to still accelarate a boat that has very little resistance, in particular an iceboat. Whether or not VMG exceeds windspeed depends on the course and the speed of the boat. If a boat is sailing at 135 degrees off the true wind, and its speed exceeds 1.41 times the speed of the wind, then it is making good downwind faster than the wind. Your sails are not "floating" because you are close hauled: don't forget the apparent wind shift. Again, iceboats etc. do not use spinnakers because they always accelerate until the apparent wind is well forward of the beam. Momentum has nothing to do with it: as I pointed out above with a formula, it isn't possible in practice to build up enough momentum to make good downwind faster than the wind.
I think the reason these arguments go on for hours at every yachtclub bar, is that there are so many options that ever-increasing alcohol enables most people to forget half of the options, half of the time. Let us agree at least that we are talking about sailing downwind faster than the wind, not just sailing faster than the wind, and also that we are not talking about coasting downwind faster than the wind immediately after a very fast beam reach. --Nigelj (talk) 19:25, 21 December 2009 (UTC)
Yes. Lashings of wishful thinking reinforced by anecdotes - instead of good quality data. (talk) 20:48, 21 December 2009 (UTC)

Dear all: thank you for your comments, which are helpful. Indeed, there is no disagreement that a sail boat can sail faster than the wind. The Hydroptère record proves that conclusively. And indeed, as Nigelj says, the matter which seems to raise doubt is whether (1) the wind can power a sailboat on a downwind course so that it proceeds faster than the wind and (2) whether it can go fast enough to make good downwind faster than the wind. I have finally found a citation which appears to me to meet the high standards that you require, namely the official report of the 2009 land speed sailing record [21]. That report includes (at the end) a diagram of the yacht's course. As you will see, the record (about 3 times wind speed) was set on a course about 120 degrees off the true wind. Hopefully you will all agree that this citation is sufficiently reliable, especially when taken together with the explanation of why this is possible? I refer here only to the question of sailing downwind on a broad reach. I agree that the question of sailing dead downwind is a different issue.--Gautier lebon (talk) 08:56, 22 December 2009 (UTC)

Taking your figures: The course is 120 - 90 = 30 deg lower than a beam reach (true wind). The downwind component of speed (VMG downwind) is 3 * sin(30) = 1.5 * windspeed. The component of speed across the wind is 3 * cos(30) = 2.6 * windspeed. So these figures do show VMG downwind greater than windspeed. I'm sure that we cannot use your figures in WP - they're not mentioned in the source and anyway that is not a reliable secondary source. I'm not really sure that we could use these calculations either, they're WP:OR. To help with googling, I said the 'cherry-pip-squeezing effect' must have a name - it's related to Galileo's 'inclined plane' and to 'tapers' in engineering as well as to wedges. The Sin and Cos stuff above is the way you 'resolve vectors into their components'. --Nigelj (talk) 13:44, 22 December 2009 (UTC)
Thank you for having confirmed that my calculations are correct. The source mentions wind speed and direction and boat speed and direction. Why do you consider that the official report of a record recognized by a national association is "not reliable"? The calculations are elementary trigonometry. They are not original research: they are taken from the references given after the opening paragraph of the draft article, see in particular [22], the very bottom of that page [23] and [24]. Anybody can reproduce the calcuations, and please note that I provided links to the relevant bits of Wikipedia on trigonometry and vecor algebra. By the way, a good explanation of the "cherry-pip-squeezing-effect" is given at [25].--Gautier lebon (talk) 09:25, 23 December 2009 (UTC)

Summary of downwind discussion[edit]

If I understand the discussion above correctly, it can be summarized as follows.--Gautier lebon (talk) 11:23, 13 January 2010 (UTC)

  • There is consensus that high-performance boats can and do sail faster than the wind on some points of sail.
  • Skepticism was expressed regarding the ability of a sail-driven machine to achieve speeds greater than the speed of the wind while sailing on a downwind course. I provided various citations to support the claim. The initial citations were felt to be insufficiently reliable. However, I have not seen any criticism of my last citation, to the world land speed record, at [26].
  • Subsequently, I have acquired the book High Performance Sailing by Frank Bethwaite (Adlard Coles Nautical, 2007). This book confirms the trigonometrical calculations contained in my draft article User:Gautier_lebon/Sailing_faster_than_the_wind and provides, on page 405 and elsewhere, data showing that sailboats can indeed progress faster than the wind on a downwind course.
  • There was also skepticism regarding whether a wind-driven machine can make good faster than the wind by tacking downwind. The detailed data regarding the land speed record shows that this is possible. Further, the polar chart at page 405 of the cited book High Performance Sailing shows that, already in 1996, high-performance sailboats were able to make good downwind at 1.5 times the speed of the wind.
  • Finally, there was skepticism regarding the possibilty of building a device that, while not powered by sails, would use only energy from the wind in order to advance dead downwind faster than the wind. Such a device would not violate any basic physical law because, as shown above, a sailboat can, by tacking downwind, make good downwind faster than the wind. However, it is not obvious that such a device could be built in practice. I provided references to a web site that demonstrates a propeller-driven cart that apparently uses only the energy from the wind and that can advance dead downwind faster than the wind. Some comments were posted to the effect that this must be a hoax, but public references to the web site in question indicate that independent viewers consider that it is not a hoax. Nevertheless, I agree that some skepticism regarding this cart may be justified.

Interested parties should take a look at Sailing faster than the wind and talk written with a biased point of view (in my opinion). Prillen (talk) 10:23, 19 January 2010 (UTC)

As to achieving a steady state downwind VMG of greater than 1.0x windspeed with a traditional sailing rig, I don't understand why there is still debate. All that is required is a sufficiently optimized rig and hull. All standard ice-boats and land-yachts do it easily, and as has been shown from readily available polars, there are a pretty fair number of sailboats that can do it as well. As some claim above, it is not necessary to use KE (turn DDW temporarily) to achieve this and can be done on a fixed heading for as long as there is wind and room.

There's no more of an authority on land sailing performance than the folks at NALSA ( and their site is littered with references, article and real world examples of this regular accomplishment:

Note #3 in faq: "The 'velocity made good' down wind is often over twice as fast as sailing directly down wind."

In an NALSA article titled "putting numbers on iceboat performance", Bob Dill (Nalsa BOD member) Bob has recorded GPS data (and includes plots and diagrams from said data) showing DN class craft achieving sustained downwind vmgs of ~3.5x windspeed lap after lap of a NALSA sanctioned race.

As was pointed out before, the NALSA data recorded during the rather recent Greenbird land sailing world record shows sustained downwind VMGs (more than a mile) of greater than 2x winspeed in spite of the fact that the craft was taking a path optimized for ground track speed rather than vmg speed.

(all of the above raw data is available from NALSA btw).

ThinAirDesigns (talk) 22:02, 25 January 2010 (UTC)

'Sailing regulations' section[edit]

I'm worried that this section seems to imply, a couple of times, that sailing boats are not subjects to the international colregs. This is legally and patently untrue. All vessels are subject to these under international law. Individual club and race 'sailing regulations' apply in addition to the colregs, not in place of them. To imply otherwise seems grossly irresponsible of us.

  • "There are three basic rules for avoiding a collision at sea" There are not, there are all the rules in colregs. This is a partial, home-made, uncited summary. In particular it skirts all the issues to do with sail vs power boats that are fishing, towing, restricted etc.
  • "If these rules are not followed in a yacht race, a protest may be called by one of the skippers." - or the offending skipper could be prosecuted under law by anybody else, not involved in the race, but just using the sea or lake at the same time
  • "... sailboats ... may be sharing the same body of water as powered vessels, who are bound by the COLREGS." Sailboats are bound by COLREGS too.
  • "After sunset all boats racing are bound by the International Regulations for Preventing Collisions at Sea (COLREGS) rather than the Racing Rules of Sailing." All boats are bound by COLREGS whenever they are on the open sea.

I think some editor(s) has got mixed up between the rules that may apply on a private course (for example an Olympic event) and what applies to the majority of yacht and dinghy racing that goes on on public waters. There is also the confusion that other members of a yacht-racing club may be under club rules to stay away from racers, but other users of the open water are under no such requirement: if they want to cruise, tow or fish through the middle of a sailboat race, they are perfectly entitled to do so, under nothing but colregs, except that these apply to all. This comes up time and again with offshore racing and such events as 'round the island' races where yacht racers come up against other seafarers and unreasonably expect all kind of strange behaviour from them. I think this section should be greatly clarified. --Nigelj (talk) 18:03, 13 April 2010 (UTC)

I'll profess ignorance, to expedite the discussion. I have limited practical experience with boats, and most of what I have contributed to Wiki comes from books. I have a fairly good idea how to avoid a collision in real world experience, but I had no idea my reading sources were abstracted from something called "COLREGS". That is, I know the rules, but not their source. Nigelj, your comment "partial, home-made, uncited summary" is to the point. Could you do two things? 1) Explain to readers why COLREGS has more authority than other secondary sources. 2) Change the article so that it references the primary source (COLREGS?) Regards, Alpha Ralpha Boulevard (talk) 01:53, 20 April 2010 (UTC)
I came across this discussion again today, having totally forgotten about it in the meantime. I have done a re-write of the section. It is now firmly based in the international COLREGS and cross-referenced with them, but, I hope it also explains the place these have in amongst other regulations that apply for inland waterways and when racing. I kept two bullet points about IALA buoyage and SOLAS, but I see that the article on SOLAS is lacking in detail regarding Chapter V requirements, which are mandatory on leisure boaters at sea now (worldwide, I think?) Maybe that's where the next work should go. Any comments and suggestions regarding this rewrite, as always, welcome of course. --Nigelj (talk) 14:54, 8 June 2010 (UTC)

Re: "In some sailing events, such as the Olympic Games, which are held on closed courses where no other boating is allowed, specific racing rules such as the Racing Rules of Sailing (RRS) may apply. Often, in club racing, specific club racing rules, perhaps based on RRS, may be superimposed onto the more general regulations such as COLREGS or CEVNI."

This is incorrect. The RRS apply to nearly all organized racing events world wide, not just at events on closed courses. Some local club events may choose to use other rules, but this is not common. Classes and clubs frequently modify some of the rules, as permitted by RRS, and sometimes in other ways as well. When racing under RRS, the RRS replace COLREGS when meeting another boat racing under RRS, even a boat racing in a different event. However, "When a boat sailing under these rules meets a vessel that is not, she shall comply with" COLREGS (preface to RRS Part 2.)

Re Nigelj's comment on 13 April 2010: "the offending skipper could be prosecuted under law by anybody else,..." You can not be prosecuted under law for a violation of RRS. However, "responsibility for damages arising from any breach of the rules shall be based on fault as determined by application of the rules..." (US Sailing prescription to Rule 68.) You may not be protested by "anyone else", only someone who "was involved in or saw the incident" RRS (60.1).

The article on the RRS also needs some work.

EricKent (talk) 22:06, 9 November 2011 (UTC)

Bernoulli effect[edit]

I just undid a revision that would have indicated that all the energy from a sail comes from the Bernoulli effect. This is false. Almost all the energy from a sail comes from simply deflecting the air. The Bernoulli has also been greatly over-stated in layman's explanations of the lift generated by aircraft wings. The edit was also problematic because it left a paragraph in the article with strikeouts. If you want to delete something, just delete it and explain yourself in the edit summary and the talk page. Mrees1997 23:38, 6 June 2007 (UTC)

I'm not sure what you expect to be true, Mrees1997, but most of the energy of a sail comes from the lifting action associated with Bernoulli effect of air over the airfoil. You can google "sail bernoulli" to find out more. Here's a reference -- [4] Short answer is: The reason a sailboat wing can pull a boat into the wind (for example, close hauling) is the Bernoulli effect of fluids. This is how most sails work. Sliceofmiami (talk) 22:04, 11 June 2010 (UTC)

I agree totally that a sail is a (thin) aerofoil and that it generates lift. However, I do not agree about the Bernoulli effect at all. Have a look at Lift (force)#"Popular" explanation based on equal transit-time. That explanation, beloved of half-educated science teachers I think, is based on a complete fallacy that the two bits of air that are divided by the leading edge of the foil, somehow are under an obligation to meet up again after the trailing edge has passed. That is nonsense. The reason aerofoils create lift is by action/reaction because they deflect the air. That does cause a pressure difference (e.g. equal to the weight of the aircraft when integrated over the lifting area), and velocity differences, but the lift is caused by the deflection. Honest. --Nigelj (talk) 22:45, 11 June 2010 (UTC)

That article was an interesting read, thank you Nigelj. I appreciated the video at [5]. So let's revisit Bernoulli -- the principle states: "as the fluid velocity increases, the fluid pressure decreases." This causes lift. I'm not really sure I understand how the wiki is trying to deny this, but I'll revisit it again tomorrow. As far as I know, Bernoulli's principle does not hinge on "equal transit time" at all. From a sailor's point of view, Bernoulli's principle is simply stated as, "Sails suck." Sliceofmiami (talk) 03:53, 12 June 2010 (UTC)

I did some more reading after posting the above too, and I still stand by what I said - that we should emphasise lift re sails, but we should stick to deflection and not Bernoulli to explain the lift. If you look further down the Lift (force) article it says that if you like, "then lift can be explained in terms of pressures using Bernoulli's principle (which can be derived from Newton's second law) [etc]" (my emph). So then I looked at Bernoulli's principle#Derivations of Bernoulli equation, opening the top section ('Bernoulli equation for incompressible fluids' since sails don't compress the air at sailing speeds). This reminded me of the physics: Bernoulli's principle is derived from Newton's 2nd Law F=ma (written there as m dv/dt = F) by substituting a few things like m = ρ A dx (mass = density x area x thickness of a very thin layer) and messing around with it. So: Bernoulli's principle is true because it is an application of Newton's 2nd law into fluid flow. Saying lift is caused by Bernoulli's principle is like saying "Cars accelerate because of the accelerator pedal" - it's true but it doesn't get to the heart of it. Sometimes that's the way you want to look at it (e.g. when teaching someone to drive) but the real explanation is deeper. In the case of cars it's more complex, but in the case of sails the deeper explanation (referring to Newton 2) is both simpler and more directly true: Sails (with the wind ahead of the beam, i.e. in laminar flow, not stalled) generate lift by catching some air and deflecting it towards the stern of the boat. The natural reaction is to push the boat forwards. (There's some sideways deflection, and therefore sideways reaction or force too, causing some heeling and leeway). I hope this isn't too technical. --Nigelj (talk) 09:47, 12 June 2010 (UTC)
I think that Nigel is basically correct here. The Bernoulli effect is just another way of explaining the lift induced by the flow of wind past an airfoil. Some aspects are more easily understood and modeled and computed by using the Bernoulli pressure differentials, other aspects are more easily undersood and modeled by using the deflection model. It is like light: sometimes it is easier to think of it as waves, sometimes as particles, but both are true. The most detailed discussion that I have seen on the aerodynamics of sails is in High Performance Sailing by Frank Bethwaite. According to him, the aerodynamics of sails is more complicated than that of wings, because the air flow around a sail has much lower speed than the air flow around a wing, so various surface effects are much more important. But this is very advanced stuff, I think that in an introductory article on sailing it is perfectly OK to say that sails are like airfoils or wings, because that is a correct rough approximation. I'm not quite sure what is being proposed for addition or deletion to the current text. The current text seems fine to me. Again, given that this is an introductory article on sailing in general, I don't think that it is necessary to mention the Bernoulli effect.--Gautier lebon (talk) 14:41, 12 June 2010 (UTC)

The section Sail#Sail_aerodynamics is pretty skimpy. I think that it would be better to beef that out with more on how airfoils work, the analogies between sails and wings, and explanations of the Bernoulli effect. Most people will hear about Bernoulli in the context of sails, and I think that it should be explained in the article on sails, which is of course referenced from the article on sailing. I'm not sufficiently into the aerodynamics of sails to add material, but I would be happy to review anything that anybody wishes to add.--Gautier lebon (talk) 14:56, 12 June 2010 (UTC)

Hmm... I got kind of lost in the car analogy. Gautier, thanks for the information, and you are likely correct -- more references are better. What happened was someone removed all the "airfoil" references from the article. I reverted the changes. Then I found the Bernoulli section and posted a note (instead of starting a new section). Anyway, to keep us on track I'll repost the discussion: "(1) Sails are airfoils, and (2) airfoils derive lift based on Bernoulli's principle."

  • I think we almost agree on Sails are airfoils, but Nigelj cut it with "ahead of beam". To rephrase -- most sails under any point of sail (close hauling, reaching, and downwind especially spinnakers) are in an airfoil configuration, supported by the referenced articles. A dead running boat in wing on wing I think is not in an airfoil configuration, but I could not find reference articles to support this claim. I've never sailed under heavy winds in wing on wing, so I cannot attest to the wings being shaped as airfoils in a dead running configuration.
  • Airfoils produce work based on Bernoulli's principle is I believe the only area that we are really discussing. Here's an article that I think describes what both of you are identifying [6]. I need to read it again. Please provide additional non-wiki articles for everyone's review.

Maybe additional references in the main article will help readers as well. I added a few, please do the same. Sliceofmiami (talk) 14:59, 12 June 2010 (UTC)

This ref looks very good; well found, Sliceofmiami. I like that it references a book by Gale Craig called Stop Abusing Bernoulli! How Airplanes Really Fly. I think that is all I was trying to say.
A few details: My car analogy, "The accelerator pedal makes it go faster", was meant to illustrate that you can explain the same thing in numerous ways, all true but some more useful than others. While moving the gas pedal is one explanation, saying that opening valves in the carburettor "to make the engine go faster" is another, but "putting more fuel and air into the cylinders to make bigger explosions" is yet another and is nearer the physical truth. As I said, the Bernoulli effect can be used to explain a sail, but why is there a wind-speed and so also a pressure differential? The answer is that the air is being deflected. The page makes the point that for an aircraft tons of air per second has to be deflected downwards. That is the 'physical explanation' and Bernoulli just adds an unnecessary extra level of complexity when the physical reality is actually so simple.
Regarding stalled sails, what I was saying was that all this talk of lift, and indeed therefore Bernoulli, relies on laminar flow on both sides of the sail. The purpose of a fat, rounded leading edge on a real aerofoil is to increase the range of angles of attack that it can operate in without stalling. Sails, with a very thin L.E. (like the Wright brothers' wings too) mean that sails begin to stall if oversheeted by just a few degrees. As the wind moves aft of the beam, the boom hits the shrouds and cannot be let out any more, so a few degrees later the mainsail begins to stall. Once all the lee-side tell-tails are flapping on any sail, we do not have lift any more: sails are just trapping air and causing turbulence and drag, not lift. It is true that a well-set spinnaker can have laminar flow roughly from top to bottom. The same is more true of square-rig sails off the wind with sheets eased: top-to-bottom laminar and actual lift, up, out of the water. I will try to find some refs for all this too. --Nigelj (talk) 15:52, 12 June 2010 (UTC)

Commented-out text removed[edit]

I just found the following text commented-out in the article. I have removed it from there and include it here in case anybody wants to make use of it. There was a comment by a previous editor who had said: "being BOLD and removing how-to content." --Nigelj (talk) 08:55, 27 July 2010 (UTC)

I support the deletion.--Gautier lebon (talk) 14:36, 27 July 2010 (UTC)

Sailing safety[edit]

First and foremost:

  1. Stay on the boat
  2. Wear a personal floatation device
  3. Learn to swim
  4. Learn how to recover someone who has fallen overboard
  5. Respect other seamen and the rules of sailing

Sailing requires respect for the risks of being on the water. All sailors therefore should be sensibly prepared. Most jurisdictions have certain minimum regulations that must be met as to equipment. When engaged in publicly organized activities they may be required to take additional precautions, as detailed by the authority which regulates the training or racing.

Safety measures may include:

  • Appropriate floatation aids, including life preservers
  • Provision of a safety boat for rescue purposes
  • Appropriate first-aid and firefighting equipment
  • Carry a knife suitable for cutting rigging or netting in an emergency
  • Install jacklines and have the crew wear harnesses connected to them, to secure the crew to the vessel.
  • Ensure visibility, use the required running lights and mount at least one radar reflector.

Man overboard[edit]

For more details on this topic, see Man overboard.

Aside from what may be required by law or a sailing organization, real safety on the water comes from an informed awareness of risks involved and the exercise of reasonable steps to avoid dangers. A Man overboard situation is likely to be life threatening for any of several related reasons since the most likely cause is rough waters and weather conditions. These degrade the ability to maneuver easily, result in vastly different rates of drift caused by both wind and current to the boat and the unwilling swimmer, and in rough weather the reduced visibility makes fast and sure immediate action to be paramount as it is easy to lose sight of the swimming person. In some waters, including inland Lakes, hypothermia can be a major threat to life, so quick recovery of unwilling swimmers can be life-saving. This requires practice and situational awareness.

The guiding principle is to stop the boat (or slow it, if stopping is impossible) and immediately marking the location by tossing a PFD (personal floatation device) or Man Overboard Pole into the water. To achieve this, the helmsman releases the tiller and dumps (releases) the mainsheet.

A better approach is to heaving to. To do this, the helmsman pushes the tiller to leeward (away from the wind) and loosens the mainsheet, ignoring the jib sheets. (Spinnaker guy also dumped if applicable). The sailing boat will tend to come up to weather and the jib will back. When this backing happens, the tiller must be reversed to point towards the boom. - At this stage, the mainsail is loose and flapping and the jib is backed (or spinnaker floging). The yacht is now nearly stopped close to the location of the man overboard. Correctly executed, this maneuver can be completed in a few seconds. (A wheel steered boat would move the wheel to bring the yacht towards the wind and when the jib backs he reverses the wheel rotation promptly, while also dumping the mainsheet).

This should be an instinctive reaction of all helmsmen. It works on all points of sailing. At that stage the helmsman can accomplish the launching of a LifeSling, unless another crew member has previously done so. With a bit of luck, the yacht will be within the range of the cordage on the recovery apparatus.

Removed stuff about lift[edit]

I just removed a whole piece of text in this edit. It appears that the text was added by User: in this edit a week ago. Various people have tried to tidy it up since then, but really I think the cause was hopeless. It made a complex attempt at explaining the points of sail, nautical terms, and Lift (force). It made a bad job on lift, but that is not needed here as the term is linked and fully described in its own article. We have been through the Bernoulli effect for example recently above, and the topic is really too complex, with some people's views so entrenched, that its full explanation is best kept in one place, I believe. The added text was also completely uncited, and there are numerous texts on each of the topics that it attempted. --Nigelj (talk) 19:23, 10 October 2010 (UTC)

Points of sail[edit]

To the best of my knowledge points of sail are defined relative to the true wind, not the apparent wind. Yoavt (talk) 10:43, 27 October 2010 (UTC)

This is not correct. The points of sail are defined with respect to the wind that the boat and the sails "see", that is the apparent wind. Only modern boats equipped with a precise system for measuring boat speed and a computer coupled to that device and to a device that measures wind speed and direction can determine the direction of the true wind. Boats without electronic equipment cannot determine the direction of the true wind. If you still believe that points of sail are defined with respect to the true wind, then please provide a citation that supports your assertion.--Gautier lebon (talk) 10:26, 31 October 2010 (UTC)
I would agree with you Yoavt. Anyone who actually does sail will look at the water or a flag to determine where the true wind is coming from and not a birgee at the top of the mast. —Preceding unsigned comment added by (talk) 14:29, 25 January 2011 (UTC)
Dear 80.254, indeed, to find the true wind, you will either look at the ripples on the water, or a flag on a buoy, or a sophisticated instrument that calculates true wind. But that is not what I understood Yoavt to say. The expression "points of sail" as used in the article refers to the trim of the sails. That trim has to be set with respect to the apparent wind, not with respect to the true wind. So, as any sailor knows, you will set your sails with respect to telltails on the sails, the shrouds, or at the top of the mast.
Every diagram I've ever seen depicting the points of sail show beam reach as 90 degrees to the true wind. Likewise, the other points of sail are drawn as to the true wind, not the apparent wind. For instance, this one: and the diagram used in the article. I'll look for a cite that states this clearly in words, but everything I've ever read talks about points of sail in relation to the true wind - that is, the point of sail is the heading relative to the true wind.
To take an example, suppose you're running downwind in 10 knots of breeze and your boat speed is 5 knots. Further suppose you sail into a hole where the wind is only 3 knots. Are you still running? Are you in irons? Close hauled? What? I'd say you're still running, but you probably need to adjust your sail trim until the boat settles down into the new lower wind.
Now, that said, sails need to be trimmed to the apparent wind, not the true wind. — Preceding unsigned comment added by Mr swordfish (talkcontribs) 20:41, 17 August 2011 (UTC)
Dear Swordfish, I hate to say this, but I think that you misunderstood the article that you cite ( The text makes it clear that what the sails see is the apparent wind, so the point of sail is with respect to the apparent wind, and the "wind direction" in the lower diagram is the direction of the apparent wind. As every sailor knows, when you sail into "hole in the wind" such as you describe, you either wind up in irons or close-hauled, until the wind comes back.--Gautier lebon (talk) 09:11, 18 August 2011 (UTC)

Gautier, I read that article as saying how to trim sails; that they should be trimmed to the apparent wind. No argument there. I don't see anywhere that they define the points of sail based on the sail trim - one might infer it (e.g. they say close hauled is 30-40 degrees, so they must be talking about apparent wind) but I'm not ready to base the wiki language on that inference.
Now that I've had a day to think about it and re-review a number of materials, here's my take:
  • How to sail manuals usually introduce the points of sail before the concept of apparent wind, so they do not make this distinction
  • When I teach a beginner sailing lesson, I demonstrate the points of sail without talking about apparent wind, thus I'm demonstrating it with the apparent wind, not the true wind.
  • For normal non-high-performance boats, there's not much of a difference.
  • Sailing is not mathematics; we shouldn't expect to find a precise definition of the term "points of sail"
  • Books on high-performance boats (e.g. Bethwaite) freely use the term "point of sail" to refer to the heading relative to the true wind. These boats go several times the wind speed, so their sails are trimmed close-hauled even when on a broad reach course. Presumably, the readers of these books are not confused by using the term in this manner.
So my take is that we (wiki editors) should remain silent on the matter. It's unnecessary hair splitting that obscures the main point, all the references I've looked at elide over the difference, and the the term is used in both senses depending on context.Mr. Swordfish (talk) 12:57, 18 August 2011 (UTC)
UPDATE: I should have read the entire article. Here's what it says under "Trimming the Sails on a Close Reach"
"When sailing on a reach, the experienced sailor, trims the sails based upon the apparent-wind. This is important because sails cannot be efficiently positioned based upon the point-of-sail or the direction of the true-wind."
The clear implication here is that the point of sail is determined by the true wind, not the apparent wind. That said, I don't find this dispositive. Point of sail could be defined either way, and both versions appear in common usage. Absent a clear authoritative precise definition, we should accept that the term is a bit fuzzy and not try to give it precision lacking in the literature.Mr. Swordfish (talk) 14:36, 18 August 2011 (UTC)

Outdent. Dear Swordfish, I fully agree with you analysis and conclusions. We should leave both the Sailing and Points of Sails articles are they are now, without a clear explanation as to whether the point of sail refers to apparent or true wind. The term was no doubt coined in the days when boats did not go fast enough for there to be any significant difference between true and apparent wind, and today the term is probably used in different ways in different contexts, as you ably point out above.--Gautier lebon (talk) 10:25, 19 August 2011 (UTC)

In order to be an acclaimed sailor, you must more so understand how the wind works than how the water works. — Preceding unsigned comment added by Bronwyn owens (talkcontribs) 19:18, 20 December 2012 (UTC)

Sailng Hulls and Shapes[edit]

I see that a paragraph has been added specifically about the Laser. I doubt that this is appropriate. Why mention that particular boat and not other very popular boats such as the Star, Soling, Hobie Cat, etc. etc. I propose that this para be deleted, otherwise we will have to expand to include a large number of popular designs. Comments?--Gautier lebon (talk) 07:41, 28 January 2011 (UTC)

Heeling (sailing)[edit]

The separate article on Heeling should probably be merged with the section in this article.--Felix Folio Secundus (talk) 19:17, 13 February 2011 (UTC)


I'm not sure that the section on licensing is accurate. I only know the rules in 2 countries, US and Switzerland. In the US, licenses are not required unless you are operating as a professional skipper. In Switzerland, licenses are only required if the boat is above a certain size. Shouldn't this section use more tentative, less definitive, language?--Gautier lebon (talk) 09:13, 25 March 2011 (UTC)

Is using ballast during a race allowed?[edit]

Okay, I'm not sure about this... some boats are equipped with ballast systems, can those ballast systems be used during a race?

One writer removed the note that racers use ballast. Here are the two works that I think are part of this.

And here are references to races that used movable ballast --

  • "" -- Movable ballast allowed
  • "" -- "2.2. RRS 51, Movable Ballast will be modified to allow the movement of sails that are not set. 2.3. RRS 51, Movable Ballast, and RRS 52 Manual Power will be modified to allow the positioning of movable ballast by power on boats as designed and as rated by the RA. All movable ballast systems shall be capable of manual operation if powered systems are inoperable."
  • "" -- "1.4.5 RRS 51, Movable Ballast will be modified to allow the movement of sails not in use while racing. 1.4.6 RRS 51, Movable Ballast, and RRS 52 Manual Power will be modified to allow the positioning of movable ballast by power on boats as designed and as rated by RA. All movable ballast systems shall be capable of manual operation if powered systems are inoperable. "

Sliceofmiami (talk) 00:46, 17 September 2011 (UTC)

Under the rules used for most racing, moveable ballast is not allowed (except of course for the crew, which can move around at will). However, some races are run under special rules which allow moveable ballast, including even moving the ballast by using engines, see for example canting keel. But I'm not sure that we need to go into that much detail in this article.--Gautier lebon (talk) 09:54, 19 September 2011 (UTC)

Maritime history[edit]

The section on maritime history seems to be a bit too European centric, Polynesian seamanship and equipment seemed to have been superior yet the Polynesians haven't been mentioned, nor is Ui-te-Rangiora. The Polynesian catamaran (7th century) was even superior than the best 18th century European vessels. See Talk:Maritime_history#Speed_of_historical_ship_types91.182.55.169 (talk) 08:39, 20 March 2012 (UTC)

Can you provide references, and text based on them?--Gautier lebon (talk) 09:15, 20 March 2012 (UTC)

Polynesian seamanship was indeed excellent. Their craft design has given rise to western catamarans but they are faster not better and catamarans are still not suited to all boat usage and have unrecoverable dangers. Many many polynesians were drowned during their migrations and their technology was not a pancea for all the problems of stormy oceans. — Preceding unsigned comment added by (talk) 12:15, 18 June 2013 (UTC)

Beating is not really defined[edit]

The section "Beating or working" doesn't actually define what beating and working are. It describes a number of actions but doesn't define 'beating', then starts using 'beating' as if it was defined. I think 'beating' refers to the zig-zag maneuvering, and that is hinted at elsewhere in the article, but as someone who knows nothing about sailing I was left uncertain. I think all that is needed is a change from

    "By this method of zig-zagging into the wind it is possible to reach any upwind destination."

to something like this:

    "This method of zig-zagging into the wind is called beating (or working) and makes it possible to reach any upwind destination." (talk) 18:24, 28 June 2012 (UTC)

Beating is used in two ways, one the zig zag process you describe, and the other as a simple synonym for close-hauled. Rjljr2 (talk) 16:39, 18 May 2013 (UTC)


I recently edited the section on knots to bring the section in line with Wiki standards. My edit was reverted, and rather than get into an edit war I thought I'd give my reasons here.

The current section on knots is not in line with the Wikipedia manual of style. For instance

knots are among the most important things a sailor needs to know.
the bowline in particular is essential
A more complete grasp...
The essence of knots used in the day-to-day work of sailing...
Even experienced sailors may forget their knots if they are not performed on a regular basis. Forgetting how to tie an important knot can damage a boat or cause injury.

These are examples of peacock terms, weasel words, and editorializing. The last sentence reads like a |how-to guide or advice column.

We need to replace this section with something that is more neutral in tone and stick to the facts. If we're going to present opinions then we need to clearly indicate that they are someone else's opinions and provide attribution. Mr. Swordfish (talk) 14:28, 9 July 2012 (UTC)

Dear Swordfish, thank you for this. I see your point about style. I reverted your first edit because I thought that you were only concerned about the fact that there was no citation, so I found one. I'm not an expert on avoiding the style pitfalls that you mention above. I do think that the basic information is correct, supported by a citation, and very useful. Would somebody care to propose text that avoids the stylistic pitfalls while providing the basic information?--Gautier lebon (talk) 06:40, 10 July 2012 (UTC)
I've had a go at the section in this edit. I have referenced it to the page already linked, and to two RYA syllabus books, as these are what I have to hand. Whether it's necessary to attribute the statements, as "The RYA says..." rather than just saying it in Wikipedia's own voice, I don't know. It's not as if anything there is controversial. --Nigelj (talk) 14:50, 10 July 2012 (UTC)
Thanks, your change is an improvement. My understanding is the if it's a statement of fact, then we (wikipedia editors) can just say it without attribution (although it should still be cited). If it's an opinion or qualitative assessment, then it should be phrased as "XXX says YYY". I think the present version strikes the right balance. Mr. Swordfish (talk) 15:50, 10 July 2012 (UTC)
I concurr. Nigel, will you update the article?--Gautier lebon (talk) 07:58, 11 July 2012 (UTC)

Outdent. I see that the section has now been updated very nicely. I'd like to thank all editors for this good teamwork.--Gautier lebon (talk) 09:52, 12 July 2012 (UTC)

MOS: Discussion regarding the use of "she" to refer to ships[edit]

There is a new Manual of Style talk page discussion that questions the practice of referring to commercial and naval vessels as "she" and "her" taking place here. One or more editors have proposed a change to the Manual of Style which would require the use of the gender-neutral pronoun "it" when referring to vessels. Please take the time to express your opinion on this matter. Dirtlawyer1 (talk) 00:58, 28 May 2013 (UTC)

Reducing Sail and Vertical Battens[edit]

In the section on Reducing sail, it says: 'newly developed vertical battens'. I question this statement. Firstly, it is not dated, so there's no way to know what it means by 'new'. Secondly, it doesn't provide any reference to justify the assertion. Thirdly, I don't believe the statement! I don't have a reference for the date - that's what I was looking for - but my memory tells me that I've known about vertical battens in mast-reefing mainsails for a long time. I believe they were invented by North, but I'm not sure of that. In any case, I believe the article is inaccurate and of poor quality in this specific regard. — Preceding unsigned comment added by (talk) 18:40, 5 January 2014 (UTC)

I need some help on Universal Rule editing[edit]

I started to edit the Universal Rule page. Can we collaborate?Americascupfreak (talk) 20:29, 10 June 2014 (UTC)

Bringing the article into complance with wiki policy[edit]

My take on the current article is that it reads as a how-to or instruction manual in many places. I'd ask my fellow editors to take a look at WP:NOTHOW for details on the policy, and I'd like to see the article cleaned up to bring it into compliance with these guidelines.

Several recent edits, although well meaning and basically correct (if un-cited), have taken the article deeper into "how-to" territory. Let's try to move teh article in the other direction. Mr. Swordfish (talk) 22:09, 5 February 2015 (UTC)

  1. ^
  2. ^
  3. ^ław_Marchaj Czesław Antony Marchaj (born in Słomniki, Poland, on July 9, 1918) is a Polish ...Aero-hydrodynamics of sailing, ISBN 0-229-98652
  4. ^
  5. ^
  6. ^