Talk:High-performance sailing/Archive 5

Archiving
I have no problems with the use of archives for this page, but an unintended side-effect is that the links to the Discussion Page from the main article (in particular in the Warning paragraph at the beginning) are no longer correct. Is there an automatic way to fix that? If not, I will correct manually, but before doing that I wanted to check with people that are more familiar with archives.--Gautier lebon (talk) 07:18, 1 July 2010 (UTC)
 * That is an ongoing problem with automatic archiving. AFAIK, the only way is manually to fix links after archiving. It might be a question for User:MiszaBot I's owner/carer/feeder? --Nigelj (talk) 08:49, 1 July 2010 (UTC)
 * OK, I will fix the links manually.--Gautier lebon (talk) 08:36, 2 July 2010 (UTC)

Death roll article
I came across this yesterday. It may be more to do with racing tactics in boats that can't bring the apparent wind ahead of the beam on a broad reach, but it seems to contradict some of the stuff here. Viz, it suggests steering off the wind as the apparent wind goes forward, to achieve best VMG downwind. I don't know how or if we could get well-sourced data on such folk-lore-ic practices. --Nigelj (talk) 08:57, 1 July 2010 (UTC)
 * I've actually seen death rolls happen in real life in regattas on Lake Geneva. Fortunately there are enough security boats around that nobody has been killed that way.  Regarding the relation to VMG downwind, there is no contradiction.  These boats cannot sail fast enough to get the wind to shift very far forward, but they become unstable if the wind shifts to be abeam.  So it is better to stay on a broad reach, if necessary by steering lower as the apparent wind shifts forward.  I'll look at my sailing books to see if I can find a citation, but give me a couple of weeks.--Gautier lebon (talk) 08:41, 2 July 2010 (UTC)

Conservation of energy and energy transfer
I watched the lectures at and gained some additional insight. We all know that the energy that drives a sailboat (or sand yacht or iceboat) comes from the wind. Some of the wind's kinetic energy is transferred to the boat, through the sails. The effect of the sails is to slow down the wind, by absorbing some of its kinetic energy.--Gautier lebon (talk) 23:48, 5 July 2010 (UTC)

Now let's look at things from the reference frame of the wind. If a square-rigged boat is moving dead downwind at the speed of the wind, then the boat looks stationary with respect to the wind. If a boat is moving at right angles to the wind, and at the speed of the wind, then, in the frame of reference of the wind, the boat is moving at 1.41 times the speed of the wind at an angle of 45 degrees. That is, an individual wind molecule will "see" the boat moving toward it at an angle of 45 degrees. But that molecule is moving, so it will be slowed down when the sail moves into it and it hits the sail. And there will be a transfer of energy.--Gautier lebon (talk) 23:48, 5 July 2010 (UTC)

The dead downwind cart's propeller generates a wash that moves in the opposite direction of the true wind. In the true wind's frame of reference, there is a wind generated by the propeller. That generated wind is opposite to the true wind, so it slows down the true wind, and that results in a transfer of kinetic energy.--Gautier lebon (talk) 23:48, 5 July 2010 (UTC)

Now consider the iceboat sailing at 135 degrees off the true wind at a speed of 1.41 times the speed of the wind. In the wind's frame of reference, the iceboat will appear to have a course of 45 degrees. That is, the boat will appear to be moving into the wind, just like the case when the boat is moving at right angles to the wind. And again there will be a transfer of energy.--Gautier lebon (talk) 23:48, 5 July 2010 (UTC)

Directly Downwind Faster than the Wind Record Certified
See here http://kimballlivingston.com/?p=3922 No time for more right now.--Paul (talk) 23:16, 2 August 2010 (UTC)

Indeed. The NALSA page on this is at http://www.nalsa.org/DownWind.html .--Gautier lebon (talk) 07:35, 3 August 2010 (UTC)

Additional article from Kimball Livingston (editor at Sail Magazine) http://kimballlivingston.com/?p=3971 ThinAirDesigns (talk) 16:53, 3 August 2010 (UTC)

Downwind Faster than wind a hoax?!!
Cetainly reads like one. The "explanation" in certainly weak, compared to the rest of the article. The references simply quote the source of the hoax, with no explanation anywhere of how this machine supposedly works.

A simple analysis shows that when the craft is traveling at the same speed as the wind, there is no apparent wind to the craft. Much like riding a bicycle downwind at the same speed as the wind. At this point there is no energy to be transfered.

It looks essentially like a perpetual motion machine.

If the section is to be believed, then these obvious concerns need to be addressed.

talk) 22:36, 6 November 2010 (UTC)


 * Your concerned are addressed, in depth, in the cited references. Please read them carefully.  You will find university papers containing formuals, and a video of university lecture that explain in great detail the physics behind this.  There is no reason to think that this is a hoax, particularly given that nobody has yet been able to explain what law of physics might be violated.  At this point, it is up to skeptics to produce reliable citations to the effect that it is a hoax, rather than the other way around.--Gautier lebon (talk) 14:28, 8 November 2010 (UTC)

No one ever claimed that it can be in steady state travelling at the same speed as the wind. It can't. It accelerates past this because of the propeller and eventually reaches steady state when it is travelling faster than the speed of the wind.

I am not claiming to understand, but just consider these things - the vehicle has friction kept to an absolute minimum and thus is able to accelerate up to a speed close to that of the wind. In addition to this, the wheels are linked with the propeller and the propeller is also giving the vehicle and extra push forwards. —Preceding unsigned comment added by 24.86.20.3 (talk) 05:06, 7 November 2010 (UTC)
 * Contrary to your assertion, it *is* and has always been claimed that it can be "in steady state travelling at the same speed as the wind." -- It's claimed, supported through math and *done*. These devices harvest energy from the true wind rather than apparent wind and thus there is the same amount of energy to harvest at *all* speeds, including exactly wind speed. ThinAirDesigns (talk) 16:33, 10 November 2010 (UTC)

It's difficult to understand but it does follow physics and doesn't violate energy conservation or other laws. The wind is traveling at a different speed than the ground. A mechanism that is physically linked to both the ground and the wind can extract energy from this difference, regardless of how fact the mechanism itself is going. The end result will be a slowing of the wind and a force on the car.

Essentially, this uses the same principles as a sailboat moving perpendicular to the wind, which can clearly travel faster than the wind. While the car itself doesn't move perpendicular, the propeller blades do, by spinning faster and faster as the car accelerates. By linking the blades to the wheels mechanically, it ensures that no matter how fast the car is moving the blades will always act as a sail that is moving perpendicular and will be able to continue to provide force even when moving faster than the wind.

Another way of explaining it more directly: You are probably thinking of the propeller as a turbine that powers the wheels, but it's not. It is actually a sail: The forward momentum for the car is not achieved from the perpendicular push of the wind on the blades spinning the propeller, but actually the straight forward push against the blades. When the wheels start moving, the propeller actually spins backwards into the wind to make sure the wind can keep pushing it. When the car is moving, the propeller blades will be spinning in an unintuitive direction, which is what makes most people question this at first: They picture the blades moving the other way, in which case the achievement would indeed be impossible. —Renevith (talk) 16:15, 7 November 2010 (UTC)

Renevith's explanation is bogus. When there is no apparent wind speed you cannot capture energy from it. If you are capturing energy from the relative movement of the ground via friction, a perfectly efficient machine can at best maintain relative velocity, but a real device will lose relative momentum.

All of the claims about these vehicles fail to exclude the possibility of storing wind energy and then releasing it in short bursts to go faster than the wind. The vehicle would only be able to store energy at wind speed or slower. Unfortunately this doesn't enthrall the public nearly as effectively.

I can't currently find it, but I saw an official video that claimed that a ship traveling crosswise to the wind could beat a balloon even if the ship didn't tack. A hypothetical cylindrical ocean was used for effect. This is also bogus as the only way a sail powered ship is able to beat the wind is during tacking when inertia allows it to temporarily exceed windspeed in the direction of the wind. —Preceding unsigned comment added by 67.237.232.111 (talk) 02:15, 29 April 2011 (UTC)


 * Renevith's explanation is not bogus. The propeller sees a non-zero apparent wind and draws energy from that.  If you prefer to think in terms of short episodes of storing energy and then releasing it, you can do that, but you have to shrink the time-duration of the episode towards zero, so that you get the continuous movement that is observed in practice.  It is indeed possible for a ship to make good downwind faster than a balloon, even without gybing, please study carefully the article and the cited references.  Of course it will not reach the same point as the balloon unless it gybes, but it can be further downwind than the balloon.  It is not correct to state that "the only way a sail powered ship is able to beat the wind is during tacking when inertia allows it to temporarily exceed windspeed in the direction of the wind".  Again, please study carefully the article and the cited references and you will see that that statement is not correct.--Gautier lebon (talk) 12:23, 2 May 2011 (UTC)

Clarification of Last Paragraph of "Sailing perpendicular to the wind"
The paragraph is quoted below. I believe this can be simplified. The apparent wind velocity vector (direction and speed) is simply a vector sum of true wind velocity and the actual vehicle velocity (direction and speed). I don't believe any reference to "hull speed" or "surface resistance" is required. These factors simply slow down the boat and change the angles and speeds that occur. In other words, if you know the apparent wind velocity and the true wind velocity then you can calculate the vehicle velocity (speed and direction) by subtraction. This is true for any vehicle including horses, automobiles, etc. An "iceboat" does not need to be referenced. The only unknown is the boat speed - the boat direction is given, as is the true wind speed and direction and the apparent wind speed and direction. Examples: If the apparent wind velocity is exactly equal to the actual wind velocity, you are not moving. This would occur when a boat makes no headway (groundspeed in aircraft terms) in an attempt to go upwind. If the apparent wind speed is less than the actual wind speed (but in the same direction), you are making sternway (going backwards and leewards).

''If hull speed is not a limiting factor, and if the strength of the wind is sufficient to overcome the surface resistance, then the speed of the boat as a multiple of the wind speed will depend only on how close it can sail to the wind. For example, assuming that surface resistance is negligible (as for an iceboat), if a boat sails at 90 degrees to the true wind, but at 45 degrees to the apparent wind, then it must be sailing at the same speed as the true wind. That is, if the wind speed is V, then the boat's speed is also V. Elementary trigonometry and elementary vector operations can be used to show that, if a boat sails at 90 degrees to the true wind, but at alpha degrees to the apparent wind, and the wind speed is V, then the boat's speed must be V×cotan(alpha). The table below shows the values of this function, as a multiple of windspeed.'' Codwiki (talk) 18:04, 10 November 2010 (UTC)


 * What you say above is perfectly correct, but, if you look at the archives of the talk page, you will find that many people don't know this and find it difficult to understand. The cited text is an attempt to explain, in a way that most people can understand, how and why a boat can sail faster than the wind.  However, I am all in favor of simplification, so I would invite you to post here your proposal for an alternative paragraph.  We can then work on that text and agree on changes in the text of the article.  The reason for citing the iceboat is that most sailors are familiar with boats whose speed is limited by the resistance of the water, so it is easier for them to understand if you provide a real situation where surface resistance obviously does not matter.--Gautier lebon (talk) 08:43, 11 November 2010 (UTC)

"Sailing" directly upwind
Now that the controversy with sailing directly downward faster than the wind has abated, maybe we should ad a section on sailing dirextly upwind? It is being done exactly like the other, with land vehicules where wheels are linked to a propeller. When going upwards the propeller works as a turbine, and is thus closer to what people expect of a sailing ship. It is theoretically possible do do this on a ship, however I have not seen it implemented, and am not sure it is practically possible today ( perhaps with a kite?).

Anyway, there are (annual?) competitions in this, mostly between universities, see the homepage for lots of video footage of wind powered vehicles going directly upwind: 

Last years winner went at 75% of windspeed directly upwind, so they are not yet faster than the wind, however there are no physical/theoretical limits to the speeds attainable (just as for going downwind, just more drag to overcome).

PS: Perhaps we should also mention, that when going upwind, energy is transferred from the wind to the vehicle, ie the wheels act as propulsion. However going downwind it is opposite - energy comes from the ground, and the propeller acts as propulsion. (This is actually the same in a sailing ship, where the sail and the keel actually have exactly similar functions, just working in two different media. Energy comes from the difference in velocity of the two media. And the energy flow will actually reverse, going downwind. This is not how most see ships though, so I guess sources will have to come first on that one).

Tøpholm (talk) 07:55, 2 September 2011 (UTC)
 * I do think that such an article would be useful, but I don't think that it should be a section in this article, which is about sailing faster than the wind. I would propose that it be made a new article called "sailing directly into the wind".  Regarding the PS, as you say, that could only be included if you can find sources that say that.

--Gautier lebon (talk) 08:21, 2 September 2011 (UTC)

Not convinced yet, and yet do not understand how possible
You can say whatever you want and show me a long list of articles and formulas, but at the end you have apparent wind from the front, and you reach steady state with front wind of (2.8wind_speed - wind_speed = 1.8Wind_speed)! This suggests that you may have a vehicle that after reaching a certain speed with no wind, or front wind, can sustain motion. This is a perpetum-mobile! Without wind at all you even need less wheel rotation speed. Something looks fishy to me. Has it been done in a wind-tunnel with accurate 180 degree wind?

Absolutetechie (talk) 20:42, 8 September 2011 (UTC) (from the Blackbird discussion)

I suggested there, and it is well known, that this is possible for <180 degrees. This is a crucial point: Even if you tack a little down-wind (i.e., have a small wind component from the side) you may get speeds faster than the wind, and with a good design even VMG greater than the wind. Absolutetechie (talk) 20:58, 8 September 2011 (UTC)

Winds regularly fluctuate in direction, and I wonder how exact 180 degrees was kept beyond visually, with the obvious delay of human (driver) reaction in correcting direction to exact 180. Absolutetechie (talk) 21:06, 8 September 2011 (UTC)

How about little help of gravitation, though I believe (but not sure) that this lake is completely horizontal, with no even small slops (which are hard to be seen by eye). Absolutetechie (talk) 21:14, 8 September 2011 (UTC)

Resolved. Also, this is not the place for such discussion. Apologies. See Talk:Blackbird (land yacht) Absolutetechie (talk) 02:05, 9 September 2011 (UTC)

Beta Theorem
The main article is misleading in that it implies a defined and consistent relationship between reaching speed and upwind apparent wind angle.

Ross Garrett's book "The Symmetry of Sailing" http://www.amazon.com/Symmetry-Sailing-Physics-Yachtsman/dp/1574090003 is a fascinating read, and on page 67 he articulates the Beta Theorem, otherwise known as the Course Theorem.

Simply stated, the sum of the hull (below-water) and rig (above-water) drag angles of a yacht are equal to the apparent wind angle (the angle between the apparent wind and the course sailed).

The drag angles are composite, and are found from the inverse trigonometrical tangent of the lift to drag ratios. For the hull drag angle for example - you would fist take the total drag of the keel-centreboard-fin and the hull, and divide this by the total sideways force (ie this matches the sail's sideways force) - and then take the inverse tan of this ratio. Similarly for the rig drag angle. (See Note 1)

The Beta theorem always applies to a yacht, no matter what direction it is sailing, and no matter what the sheeting angle (yes even luffing). This latter point illustrates that the Beta theorem must use the actual current drag angles, not the optimum ones of the craft. Ross Garrett emphasises this point.

Therefore the conclusions of the main article are not correct where it implies in the speed tables that a craft may sail at the same apparent wind angle on a reach as it would upwind.

The drag angles clearly vary greatly between upwind and reaching of every component, including sails, keel/centreboard/fin, hull. And of course the parasitic drags increase enormously.

About the only drag angle contributor that would ever remain almost constant would be that of the lift from a planing hull. A windsurfer sailed with a constant angle of attack (around 5 degrees) is a good example of constant lift-drag, and might have a lift-drag ratio of about 8:1. By contrast, both Displacement hulls and hydrofoils get worse drag-angles (ie lift-drag ratios) in practice as speed increases.

A further illustration of the inconsistent relationship between reaching speed and upwind apparent wind angle would be to compare the upwind and reaching states of a 12m Americas cup yacht with a Tornado catamaran and with a windsurfer. Charco21 (talk) 05:46, 20 September 2011 (UTC)


 * Note 1 - The drag-angle for the lift and drag of the hull are derived from the orthogonal below-water forces relative to the true course, and for the rig the forces are relative to the apparent wind. At constant speed the resultant force on the hull is equal and opposite to the resultant force on the rig. Charco21 (talk) 02:20, 1 October 2011 (UTC)


 * Could the author of the above post please sign it? It would be good to add this material to the main article in some form, but the main article is not incorrect, because it assumes that the drag angle is insigificant in order to present a theoretical maximum.  Of course in practice this cannot be attained by sea-going boats, and the article says that.  But I suspect that the drag angle is so small for ice boats that they do approach the theoretical maximum shown in the article.--Gautier lebon (talk) 09:40, 19 September 2011 (UTC)

Picture request
In my opinion, the article does not have picture, describing all possible speed for ice boats, capable of moving with a known minimum "angle alpha" for the apparent wind.

The picture is very simple and corresponds to the known fact of school geometry. It's - two circles with a common chord (true wind). Something like http://www.ljplus.ru/img4/n/i/nik_vic/step2.gif - there is only one circle is drawn. Here http://forum.exler.ru/uploads/129/post-1281696562.gif already 2 laps.

Unfortunately, I have not found a reference to such a description (and do not know about such interpretation). Besides, I have linguistic and technical difficulties to edit the wiki. So please make a box with a similar picture. nikvic. — Preceding unsigned comment added by Nikvic (talk • contribs) 14:38, 29 November 2010 ‎(UTC)

Maximum speed course sailing angle
' "A yacht which can sail faster than the wind will sail at its maximum speed when the apparent wind and the true wind are at right angles." '

According to this theory:


 * a windsurfer capable of sailing at twice the windspeed, should sail at 120 deg off the true wind to achieve this, and would have an apparent wind angle of 30 deg
 * a land yacht like Greenbird sailing at 3x the true windspeed should choose a tighter sailing angle of 109.5 deg off the wind, and would have an apparent wind angle of 19 deg
 * an ice yacht doing 10x windspeed should sail the correspondingly tighter angle of 101.5 deg, and would have an apparent wind angle of 12 deg
 * conversely, a yacht which can only just exceed windspeed would sail almost straight downwind for maximum speed

Can anyone can verify or disprove this fascinatingly simple but seemingly consistent theory? Charco21 (talk) 05:55, 20 September 2011 (UTC)


 * Can the author of the above post please sign it? I don't think that this theory is correct.  Is there a reference for it?  In any case, it cannot be included in Wikipedia if there isn't a reliable reference: we cannot include the results of WP:OR.--Gautier lebon (talk) 09:49, 19 September 2011 (UTC)


 * I do not have a reference for this, it is just one of those "facts" I have known from way back. The empirical evidence suggests it may be true, especially when you look at the speed sailing efforts of the windsurfers and kites over the past 15 years. Charco21 (talk) 05:56, 20 September 2011 (UTC)


 * The last item (a yacht which can only just exceed windspeed would sail almost straight downwind for maximum speed) is demonstrably false, so I doubt your hypothesis is correct. In any case, as Gautier says, we can't include it without a cite. Mr. Swordfish (talk) 12:23, 20 September 2011 (UTC)


 * Yes I agree with Mr Swordfish, the hypothesis is not a good model for sailing speeds less than maybe 1.5x windspeed. I think this is probably because a high drag sail configuration is a benefit for those lower performing craft, whereas maximising lift to drag of hull and rig (per Beta theorem) would be the objective for faster craft sailing on tight reaches. Interesting that no other suggestions have been forthcoming for the best direction to sail for maximum speed. The more fundamental question intrigues me .. why does a speedsailing kite surfer, for example, sail broader than Greenbird? Charco21 (talk) 12:22, 24 September 2011 (UTC)


 * >Interesting that no other suggestions have been forthcoming for the best direction to sail for maximum speed.


 * The direction of max speed depends on the boat design, the wind strength, and the sea state, so a simple explanation that accounts for all this is unlikely. Mr. Swordfish (talk) 13:43, 26 September 2011 (UTC)

Proof of the 90-degree course theorem by example
Achieving maximum speed would normally be done by choosing the optimum sail and fin configuration and of course a flat sea state. Maximum speed corresponds to minimum apparent wind angle relative to the yacht (ie minimising the Beta angle of the Beta theorem. Then by inspection of the Beta theorem, clearly this would be obtained by the hull and the rig each operating at their minimum drag angles. In practice this could be achieved by choice of sail area and fin area so that they are each operating at the optimum angles of attack.

Using the example of a yacht which has a Beta of 30 degrees (eg a slalom type windsurfer) this craft will sail at exactly 2x windspeed at a course angle of 120 degrees off the wind, and with this the apparent wind is exactly at right angles to the true wind.

Changing the course angle slightly from this - and assuming that the sail and fin are changed in size to maintain optimal drag angle operating points - the speed drops off.

Changing this suggested optimum course angles by just 1 degree to 119 or 121 deg the speed drops by 0.02%;

changing by 5 deg to 115 or 125 deg the speed drops by 0.4%,

and changing by 15 deg to 105 or 135 deg the speed drops by 3.4%.

ie sailing at 19.319 knots at 105 rel true wind of 10 knots yields an apparent wind angle of 30 deg;

sailing at 20.000 knots at 120 rel true wind of 10 knots yields an apparent wind angle of 30 deg;

etc

In the first example the apparent wind is 75 deg relative to the true wind; and in the second example the apparent wind is 90 deg relative to the true wind.

Since the apparent wind is stronger in the first example, a smaller sail would be used for sailing as fast as possible in that direction.

The key assumption in all of the above is that the objective is to sail as fast as possible in a given tight reaching direction, which corresponds to a minimum Beta angle or sum of drag angles. Furthermore, having chosen the sailing angle, rig and fins can be varied to achieve optimal Beta.

The example shows that the 90-degree course sailing hypothesis holds true. Differential calculus could be used to prove the general case, by solving this equation -

(d/d.Theta) [ (Wa x cos(theta) - Wt) / cos(theta + beta) ] = 0

Where -

Theta = course sailed rel true wind

Beta = apparent wind rel course sailed = sum of drag angles = constant

Wt = true wind speed

Wa = apparent wind speed

Charco21 (talk) 03:45, 1 October 2011 (UTC)

'Sailing dead downwind faster than the wind' - Non encyclopedic - Cleanup request
The section "Sailing dead downwind faster than the wind" is terribly technical, not clear, and, it seems, leaning on fringe science - although claiming not to. Please clear up the section, make it MUCH shorter and less technical. If you are referring to technicalities, leave them for the remarks, or add some graphic that clarifies the idea.

How does one mark the section as such? I couldn't find the correct template. Non-encyclo is a last-resort template meant as a warning to the writer, after entering too many non-encyclopedic articles, which is not the case here. Its the article that needs a rig-up. פשוט pashute ♫ (talk) 10:30, 9 June 2013 (UTC)

I'm adding a cleanup request accordingly. פשוט pashute ♫ (talk) 10:36, 9 June 2013 (UTC)


 * I've done some work to provide a clear explanation. More could be done, you are welcome to try. Being technical is fine, there are much more technical articles than this.  But it is also a bit confused.  Tuntable (talk) 10:48, 9 June 2013 (UTC)


 * I agree with Tuntable, many Wikipedia articles, in particular on science and mathematics are more technical than this one. The science involved here is not "fringe" in the sense of non-accepted, but it does concern an unusual phenomenon that does not interest most people.  However, that is the point of an encyclopedia: to give information on obscure topics, and to provide information that cannot easily be found elsewhere.  I do agree that clarification is always welcome, but the topic is counter-intuitive, so it is not easy to provide any simpler explanations.  Specific suggestions are most welcome.--Gautier lebon (talk) 14:46, 9 June 2013 (UTC)

I put back the explanation that was deleted by User :Pashute. Improve the explanation by all means, but one is required for such an unintuitive phenomenon. Particularly as the rest of this article is about explanations.

Incidentally, most other explanations that I have seen are terribly confused, and add all sorts of noise such as energy considerations. The Cart approach is relatively very easy to understand, and involves no equations. Tuntable (talk) 07:34, 10 June 2013 (UTC)


 * No, I disagree. You are not giving a cart explanation but a mixed up repeated non sequential account of what this was all about. Perhaps adding two sentences at the beginning of what I wrote would clarify the problem better. I'll give it a second try HERE, and you can decide what to do with it. I do not wish to enter an editing war. Please see my reply to the bold edit. My new proposal: tomorrow. (gotta go now) פשוט pashute ♫ (talk) 01:29, 30 June 2013 (UTC)


 * I'll work on a better version, and include your ground yacht example.
 * but will try to return the rest of the corrected text. Lets work together.
 * Meanwhile: I'm leaving this here for the record:


 * This sounds counter intuitive, since it seems that when using a sail, one cannot exceed the speed of the wind, pushing that sail itself.


 * In order to understand this intuitively, it is sometimes proposed to conciser the issue of a person pushing a wagon that they are holding on to. The wagon cannot go faster than feet of the person pushing it. But if the person uses gears, as when riding a bicycle, a mechanical advantage can be achieved with transmission, using the same power to leverage a higher speed albeit a lesser force, and thus exceed the speed of the advancing feet (and their stronger force).

פשוט pashute ♫ (talk) 02:07, 30 June 2013 (UTC)


 * One of the limitations of Wikipedia is no OR and no SYN. In a much earlier version of this article, I had included some explanations, but they could not be retained because there was no source for the explanation. So please do try to stick to explanations that are found in the sources.--Gautier lebon (talk) 16:18, 30 June 2013 (UTC)

BOLD EDIT NOTICE
While I appreciate the work that went into the dead-downwind section, I concur that it was unclear and utilized a physics-style technical approach poorly suited to a sailing article. I blanked all but the first sentence and re-wrote it from scratch from a sailing perspective. I don't claim my version is particularly good, I merely hope it's better than what was there before. I eagerly encourage anyone to hack away at my version or completely replace it with something better.

Regarding the suggestion that this "seems, leaning on fringe science", dead-downwind faster than the wind is documented out the wazoo with Reliable Sources in the Blackbird_(land_yacht) article and there are, as far as I am aware, zero Reliable Sources disputing it. (Some of the Blackbird sources are probably appropriate to replicate over here.) As far as Wikipedia is concerned dead-downwind-faster-than-the-wind is a firmly Reliable-Source established scientific phenomena, and any edit disputing it should be scrubbed as Fringe unless that edit is supported by multiple reliable sources. (A contrary edit supported by just a single Reliable Source would almost certainly constitute Undue Weight of a Fringe claim.) Alsee (talk) 15:19, 28 June 2013 (UTC)


 * I like Alsee's bold edit. Let's see what others think.--Gautier lebon (talk) 09:59, 29 June 2013 (UTC)


 * Ah! I see where you say about my claim to fringe. I meant that THE WAY THE ARTICLE WAS WRITTEN it SEEMED like fringe science. I corrected it, shortened it and clarified it, in a way that made the whole thing CLEAR and crisp. See my response above. Anyway the way it is now, its back to looking like a fringe science article. Sad, because its a SIMPLE principle. Using a turbine, you can, in fact, use the wind energy received, to move a boat at speeds that are faster than the speed of the moving air around the boat, i.e the wind. This is opposed to a sail downwind which cannot go faster than the wind pushing it, and in other words can use much less energy out of the wind.


 * An intuitive explanation of the problem is that it seems counter intuitive that a boat can sail downwind, faster than the wind pushing its sail.


 * An intuitive explanation of the phenomenon would be that a giant bull pulling a wagon, can't make it go faster than its legs pushing it, but with gears, just like a person riding a bicycle, the wheels can move faster than the speed of the legs. The power is turned to work in what is called a mechanical advantage using transmission. The same power is used at a higher speed but with less force. (so when it crashes into a slower moving but more forceful wagon, with the same power, the two will cancel each other out.) פשוט pashute ♫ (talk) 01:29, 30 June 2013 (UTC)


 * One of the limitations of Wikipedia is no OR and no SYN. In a much earlier version of this article, I had included some explanations, but they could not be retained because there was no source for the explanation. So please do try to stick to explanations that are found in the sources.--Gautier lebon (talk) 16:18, 30 June 2013 (UTC)


 * Reliance on the availability of good RSs leads to a good encyclopedia, but this technique has limitations. Once in a while (surprisingly, not often) a Talk page provides some NOR explanation that is clearer that the one given in the article. Here, I believe, is such a case. While this isn't the purpose of a Talk page, it is a very valuable service for WP readers who read the Talk pages as well the articles, as I do. It also shows a limitation of the RS+NOR policies. An improved policy would be to allow NOR explanations or knowledge until someone provides a good NOR reason to object to them, or an RS is found that supports a good replacement. David Spector (talk) 15:14, 11 August 2013 (UTC)


 * David, I agree with you. In fact I had done exactly what you say, namely posted an OR explanation, on the talk page way back.  That explanation showed that there was no violation of the principle of conservation of energy.  But I was told that OR was not allowed even on the talk page.  I made some attempts to suggest modifications to the SYN policy, but was unsuccessful.  But maybe it's worth a new try?--Gautier lebon (talk) 15:27, 12 August 2013 (UTC)


 * Agree. But this is more than a problem with SYN. I have already proposed changes to OR and RS or a new policy in what I hope is the proper place. This may be one of the biggest problems with WP, and is not difficult to fix, so, who knows, it may be adopted someday. But it may take a long time to be noticed. Readers can help by drawing the attention of WP movers and shakers to my proposal, if you agree with it. Or by revising the language of my proposal to make it more acceptable or persuasive. Until it is adopted, it will be best for all of us to work within WP policies. David Spector (talk) 16:07, 13 August 2013 (UTC)

If a topic is uncontroversial (like this one) then reasonable editors shouldn't be seeing Wikipolicies as a significant obstacles. The first, simplest, unstated rule, is not to pointlessly challenge content that everyone agrees is good.

No Original Research prevents people from using Wikipedia from promoting their own ideas. The Synthesis rule is quite clear that it only refers to attempts to advance a position not advanced by the sources, you can't take a source that says "crime is bad" and "poor people commit more crime" to manufacture "poor people are bad".

If Reliable Sources say that helium balloons rise, if it says the reason is buoyancy, then there's nothing wrong with an "original" explanation that a balloon can fall upwards in the same way a wooden ball under water will fall upwards (i.e. it floats). The only idea being advanced there is an accurate uncontroversial understanding of the source ideas, that helium balloons rise. There's no need for a source using the underwater wooden ball example, not unless someone has a genuine concern that I'm advocating that "wood floats" or something. Chuckle.

In controversial topics the challenge is resolving inevitable disputes, and keeping bad or position-advocacy content out. On topics like this the main concern is coming up with good content to put in. There's no barrier to putting uncontroversial and valuable explanations of faster-than-the-wind into this article.

Oh, and Original Research is not prohibited on talk pages... but it can be a red flag. In some cases it can be helpful in sorting out and developing content which is appropriate to the main article. However there was a problematic comment above suggesting Original Research on talk pages as a "valuable service for WP readers who read the Talk pages as well the article". If that's what's crossing your mind then you're treading on thin ice. Wikipedia is not a vehicle for advocacy. Talk pages are work zones with few restrictions, but using a work zone for advocacy will rapidly blow up in your face. If there are people actively objecting that particular Original Research on a talk page is unhelpful or disruptive then almost by definition it's not aiding work on the article, and any further posting of such material would likely be a problem. But don't be afraid to use talk pages to discuss Original Research that other editors do find useful. Alsee (talk) 16:04, 11 September 2013 (UTC)


 * Alsee, I agree with most of your comment, so much so that I wish it were merged with the actual WP policies. However, I didn't understand your use of the term "advocacy", so I didn't follow the part of your discussion about "using a work zone for advocacy"... My original comment had to do with being permitted to offer good explanations of things (like the example in this article) without risking deletion due to NOR and/or lack of a RS. In practice, frequently, editors are intelligent and don't apply WP policies literally. They think about the actual case... I frequently refrain from applying policy myself in some cases, but apply it strongly in others, using guidelines similar to the ones you mention. The point of my three proposal entries was an attempt to make the WP rules conform to what most of us want and actually practice, not what the practices currently literally say. If we applied the policies uniformly, much of WP would be deleted; that would not be a good result. The current policies are therefore neither accurate nor complete. I will have to leave it to future efforts by myself or others to amend the policies appropriately, since my attempt failed to move editors to agree. Thank you for your great comment. David Spector (talk) 18:20, 12 September 2013 (UTC)


 * Wikipedia has a narrowly defined purpose. Wikipedia helps people by accurately summarizing what the Reliable Sources say. When there is a controversy on something, obviously both sides feel they would be helping readers by showing why something is (or isn't) true, good, or beneficial. Trying to help readers, in regards to a controversy, is advocacy. You suggested that Original Research on a talk page could be a "very valuable service for WP readers who read the Talk pages". You said so yourself that is not the purpose of a talk page. If I post an Original Research cure for cancer on a talk page, and I'm hoping it will help WP readers who happen to view the talk page, then that's advocacy. If I discover a cure for cancer I could discuss it here for the purpose of seeing if any other editors have (or can find) relevant Reliable Sources discussing it, working to see what (if anything) might be appropriate in the article. There's certainly a grey area there. Hoping something will help WP visitors is a big red flag for advocacy, and as I indicated the key issue is whether other editors do (or do not) view it as reasonable work towards article development. Alsee (talk) 22:59, 15 September 2013 (UTC)

Sailing Perpendicular to the wind
This whole section, and the first section is not very well explained for people new to this. It needs to be simplified and made clear. — Preceding unsigned comment added by 97.93.114.155 (talk) 05:21, 21 September 2013 (UTC)


 * Simplifications and clarifications are of course always welcome, but unfortunately the two paragraphs that you added were not correct. When a boat sails at 90% to the real wind, the apparent wind (the wind as seen by the boat) increases and shifts forward, as explained in the article. It does not stay constant as you implied in your text.  Maybe you can propose some simpler way to make the correct statement?--Gautier lebon (talk) 09:11, 21 September 2013 (UTC)

Directly down wind faster than the wind vehicle (DDWFTTW)
I changed the title of this section to refer to the vehicles that do this. One issue with the old title is that such vehicles are not sailing, but instead using a wheel driven propeller to generate an upwind thrust (geared to produce greater thrust (force) at lesser speed than the opposing ground force and speed, compensating for power losses). I also simplified the description since the Blackbird article goes into more detail.

For a reference source, note that the principle behind DDWFTTW vehicles was used back in 1877 by the Brennan_torpedo. I updated the practical vehicles section to include a reference to the Brennan_torpedo and how it would relate to DDWFTTW vehicles. In moving water with the wires attached to fixed posts, it would travel downstream faster than the stream.

Rcgldr (talk) 09:28, 18 August 2015 (UTC)

Sailing dead downwind faster than the wind
I put back the explanation deleted by user:Alsee. I think that the current explanation is fairly good, and better than what was there before, the trick being to keep the description in terms of geometry rather than motion. Better explanations welcome, but not just removal.

I also reluctantly removed Alsee's addition shown below. I think it is plain wrong. The key is absolutely not just that the propeller blades move and so are "tacking", but rather that they are driven by the wheels which then pushes air backwards.


 * The key to achieving directly downwind speeds greater than windspeed is to utilize a sail that can tack across the wind while the hull of the craft is traveling directly downwind. This can be accomplished by mounting a pair of sails on a rotating axle. This arrangement is more commonly known as a standard propeller. Rotating the propeller results in the sails tacking across the wind much like a conventional sailing craft tacking across the wind, only in this case the sail follows a circular tack while the hull travels directly downwind. The keel is a crucial active component required for a tack to work. In a conventional sailing craft the keel drags in the water and that drag force is directed sideways to drive the sail (and the entire craft) across the wind. In a dead-downwind land craft wheels take on the role of the keel, and the wheels drag against the ground to generate a rotational force driving the propeller blades across the wind in a circular tack. In a dead-downwind sea craft the keel would have to take the form of a turbine dragging through the water, generating a rotational force driving the propeller blades across the wind in a circular tack.

Tuntable (talk) 02:11, 29 September 2013 (UTC)


 * 1) There is no contradiction between "rotor blades are tacking on broad reach" and "rotor is acting as a propeller". Both are correct statements.


 * 2) It doesn’t matter what you think is "plain wrong", but what is supported by the sources. The blades-on-broad-reach-analogy has been used in multiple articles:
 * http://www.wired.com/magazine/2011/02/ff_fasterthanwind/all/
 * "Cavallaro knew that a sail on a tack and a spinning propeller blade were aerodynamically the same."
 * http://www.wired.com/autopia/2010/08/ddwfttw/all/
 * "This would ensure the blades of the prop would make one foot of “sideways” movement for each foot they went downwind – just like PlayStation on a broad reach."
 * http://www.seahorsemagazine.com/current-issue/84-rules-are-there-to-be-broken
 * "The trick, of course, is that neither propeller blade is going directly downwind, but tie them together and they form a propeller whose centre of mass is going directly downwind."
 * --Wikipedicus (talk) 14:35, 30 September 2013 (UTC)

If it wasn't for efficiency issues, the propeller could be replaced with a centrifugal pump with an axis parallel to the wheel axis, a forward facing inlet, and a rearward facing output. There would be no component of movement perpendicular to the wind by the blades of such a pump. The wheels could also drive a treadmill with sails attached that would be vertical when moving backwards along the upper portion of the treadmill and collapsed when moving forwards along the lower portion of the treadmill. The only issue with these methods is the efficiency factor, but the principle is the same, effective reduction gearing from the ground to the thrust source allows a greater thrust (force) at a lower speed than the opposing force and speed of the ground. Rcgldr (talk) 11:09, 18 August 2015 (UTC)

This becomes more clear if the vehicle interacts with other media which are moving at different speeds. Take the case of a yo-yo being pulled by a string that is getting wound or unwound from a hub. In the case where the diameter of the hub is less than the diameter of the yo-yo, the string winds around the hub from below, and the yo-yo advances along the ground at a faster speed than the string. No tacking involved. Now say the yo-yo has wheels similar to a train and rides on two rails with an open gap between and below the rails, and that it's hub has a greater diameter than the wheels. In this case, the yo-yo moves in the opposite direction that the string is pulled. Then continue with this case, only now the string is attached to a fixed post, and that the rails are moving. Then the yo-yo moves "downrail" faster than the rail. Again no tacking involved. The Brennan_torpedo, made back in 1877, operates on this same principle. The walkway cart video linked to below may help in understanding the principle behind effective gearing and it's affect on the direction of the cart, less than 1 and it's a down stream cart, greater than 1 and it's an up stream cart. Not shown is the less than zero (negative ratio) case, which is down stream slower than the stream cart (like a turbine driving the wheels downwind, air goes forward through the turbine, while it drives the wheels backwards, a negative gearing ratio). With a negative gearing ratio, there's excess power from the turbine that could used as a source of power. In the case of negative infinity gear ratio, it's a windmill (it doesn't move). Not explained in the video is that the closer the that the effective gear ratio is to 1, the faster the cart goes, assuming it's efficient enough and doesn't stall.

walkway carts

Rcgldr (talk) 23:03, 18 August 2015 (UTC)

Reason for tag
I can see in the archives that there was a lot of debate about this article, which indicated that it was difficult even for those well-versed in the subject to understand. I understand it, but I don't feel that it is well explained here. Make technical articles understandable offers some good advice on how to improve this article. I'll try my hand at it, as well. User:HopsonRoad 14:14, 22 January 2017 (UTC)

Awkward title
"Sailing faster than the wind" is such an awkward title, that it's hard to compose a first sentence that conforms to MOS:BEGIN. I'm not sure that I have a better title in mind, but here are some possibilities, together with possible lead sentences, that I would like to hear from other editors about: Remember a new, less awkward title will have a redirect from the phrase, "sailing faster than the wind". Cheers, User:HopsonRoad 04:36, 22 January 2017 (UTC)
 * Sail-craft speed is a function of forward surface resistance encountered by a sailboats, iceboats or land sailing craft to the motive power obtained by its sails.
 * Sailing speed is a function of forward surface resistance encountered by a sailboats, iceboats or land sailing craft to the motive power obtained by its sails.
 * High-speed sailing is achieved with low forward surface resistance, as encountered by sailboats, iceboats or land sailing craft, as the craft obtains motive power with its sails.
 * High-performance sailing is achieved with low forward surface resistance—encountered by catamarans, sailing hydrofoils, iceboats or land sailing craft—as the craft obtains motive power with its sails at speeds that are often faster than the wind. (User:HopsonRoad 19:01, 22 January 2017 (UTC))


 * 3: "High-speed sailing" seems about right from reading the article, though I know little about ships — Iadmc  ♫ talk  13:47, 22 January 2017 (UTC)


 * I agree, I think High-speed sailing is probably the best choice. Sailing speed and Sail-craft speed seem a bit general for the specifics of the article. I think only the lead would need rewriting. - Ahunt (talk) 15:44, 22 January 2017 (UTC)


 * I agree the title is a bit awkward, but I don't like any of the proposed alternatives because they say nothing about sailing faster then the wind, which is the subject of this article. High-speed sailing, for example, could just mean running downwind at 20 knots in a 30 knot wind, while it's not obvious that making 5 knots in a 4 knot wind is "high speed." I have checked the few sailing books on my shelf and none suggest a good term for this concept. I did come across the term "apparent wind sailing" but I'm not crazy about that. I think the math was first set out in a book titled "The Aerodynamics of Sails" but it covers far more than just sailing faster than the wind. Kendall-K1 (talk) 17:31, 22 January 2017 (UTC)
 * How about, "High-performance sailing is achieved with low forward surface resistance, as encountered by catamarans, sailing hydrofoils, iceboats or land sailing craft, as the craft obtains motive power with its sails at speeds that are often faster than the wind." (temporary emphasis)? See: . User:HopsonRoad 17:52, 22 January 2017 (UTC)
 * Since its sourced and explains the relationship between "high-performance" and "faster than the wind", that's even better — Iadmc  ♫ talk  19:08, 22 January 2017 (UTC)
 * I agree with that, best option so far! - Ahunt (talk) 19:18, 22 January 2017 (UTC)

Wind-rotor propulsion out of scope for this article?
The section, Sailing faster than the wind seems to be out of scope, since this is an article about sailing craft. There are also wind-rotor-propelled watercraft (see Windmill ship), which are out of the scope of most sailing articles. I recommend a "See also" for wind-rotor propulsion, directed in this case to Blackbird (land yacht), which seems to be the primary example of this concept. User:HopsonRoad 23:38, 22 January 2017 (UTC)
 * Agreed. Kendall-K1 (talk) 00:09, 23 January 2017 (UTC)


 * Disagreed and reverted, pending other's aggreement/disagreement.GliderMaven (talk) 04:08, 23 January 2017 (UTC)


 * I also disagree. And I disagree with the recent name change also. This article was originally about using wind power to travel faster than the wind, and its overall content has remained largely unchanged since wrote this article over the period August 2009 to January 2010. While the emphasis was always on sailing craft, the longstanding nature of the article has always been to encompass any means of traveling faster than the wind. Sure, consensus can change, and if it does, the text to be removed should be preserved in another article. ~Anachronist (talk) 06:44, 23 January 2017 (UTC)
 * Thank you for your comments, GliderMaven and Anachronist. It seems to me that the topic is adequately covered at Wind-powered vehicle to which the material could be added appropriately. Regarding this article, in addition to having an original title that incorporates poorly into a lead sentence, the original article seemed to consist largely of original research—there being many notes, but few reliable sources. There are many articles in the topic area of sailing that need a lot of work and this one seemed to be one. I also changed it from WikiProject:Ships to WikiProject:Sailing, because it appeared not to be about ships. Sincerely, User:HopsonRoad 12:55, 23 January 2017 (UTC)


 * I would agree with a legitimate merging of this article into wind-powered vehicle, failing that, the current article name seems a poor choice, the old article name was better.GliderMaven (talk) 22:53, 25 January 2017 (UTC)
 * Thanks for this input, GliderMaven. I was thinking of drafting a clearer explanation than now exists, regarding the section on faster-than-the-wind performance of wind-powered vehicles in a Sandbox, subject to discussion here, and—once that looks good and consensus is attained—move that section to wind-powered vehicle, with a brief mention in this article. I feel that make for a cleaner division between the two methods of wind-power—sail versus rotor. Sincerely, User:HopsonRoad 03:27, 26 January 2017 (UTC)