Difference between revisions of "3090: Sail Physics"

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==Explanation==
 
==Explanation==
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{{incomplete|This page was created by a wind-blown electron. Don't remove this notice too soon.}}
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{{incomplete|This page was created by a wind-blown electron from a man on a boat. Don't remove this notice too soon.}}
  
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This comic shows what initially appears to be an explanation of how boats sail upwind. However, it quickly devolves into wrongness, where, instead of mentioning {{w|tacking (sailing)|tacking}}, it dives into a totally wrong{{citation needed}} explanation involving electrons and magnetism.
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This comic starts off looking like a typical explanation of how {{w|sailboat}}s can travel upwind — a topic that continues to spark debate and refinement in physics circles. However, it quickly takes a strange tack into a completely fictional and incorrect theory involving triboelectric charging and the Lorentz force, rather than referencing real mechanisms like {{w|airfoil}} aerodynamics.
  
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This humor works at another level - all\* interaction of physical things at macro scale (humans and boat sized objects) are of electromagnetic in nature (this is considering, that at this scale, among the 4 fundamental interactions, only electromagnetic interactions are of reasonable strength {{citation needed}}). So one unaware of sailing mechanics may start to explain the situation with electromagnets, and could come to this line of thinking, but it is wrong. If we are to consider this, {{w|Triboelectric effect|Triboelectric effect}} is the mechanism of acquisition of static charge. Though, it depends on relative frictional forces invloved between two objects, which inturn depends on effective interaction surface area. But the charge acquired would be very small, and not be of comparitive order of magnitudes with gravity. There is more charge generated due to running of water across the boat in a realistic situation {{citation needed}}. Then the comic assumes motion in direction of downstream, due to effective normal forces on the sail. Then the comic considers this motion as motion of charged object in Earth's magnetic field. If we are to consider this magnetic field to be roughly parallel to Earth surface, which would be true for situations close to equator (as Earth's magnetic field is effectively that of dipole bar magnet, which is roughlly aligned with our planetary rotational axis (as of writing of this explaination, as the magnetic field dipole keeps on maoving, and is also expected to do a complete flip in a few 10000 years, so there would be some time where it is in the equitorial plane at some point (assuming a continous motion of Earth's dipole))). In which case, the net lorentz force on the boat would be $ F = q (v \times B) $, and since both velocity of both and magnetic field lines are in thae same plane (as viewed in the above sketches, a top-down manner) then the force would be perpendicular to plane, that is, parallel to radius vector towards Earth's core, so it will not cause any motion in plane due to this force. If we consider magnetic field lines to be perpendicular to Earth's surface (close to poles), even then the magnitude of the force is very small. If we consider a net charge of 1 Coloumb across the boat (which is a extremely high amount of charge, at which point, the charge would try to acumulate on sharp objects, and due to this high charge density, the sharp objects would start to break of from the boat (this is due to high self electrostatic energy, which is roughly proprtional to square of charge density divided by radius of curvature of object), assuming that this charge does not cause the ship to break or the charge to leak out to water body), and also consider field strength of order $ 10^(-4) $ Tesla (close to typical values on surface {{citation needed}}), and take wind speeds of 10000 m/s (also very high {{citation needed}}) then the net force on ship would be *1 N*, which for a boat of mass 10 Kg (less for a typical boat, but is appropriate for a makeshift raft {{citation needed}}) cause a net acceleration of 0.1 m/s^2. Which is not extremely small, but due to friction across the boat, would be cancelled (by 1 or 2 orders of magnitude {{citation needed}}).
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This humor works at another level — most interaction of physical things at macro scale (humans and boat sized objects) are electromagnetic in nature. So one unaware of sailing mechanics may start to explain the situation with electromagnetism, and could come to this line of thinking, but it is wrong. If we are to consider this, we find that either no force is appearing in the direction shown, or very little.
  
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==Transcript==
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The first panel is a fairly accurate diagram used to explain the reasons why a boat can sail into the wind (see below), it just sets up the scenario.
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{{incomplete transcript|Don't remove this notice too soon.}}
 
  
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[Panel 1]
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The second panel portrays the {{w|triboelectric effect}}, which is transfer of static charge through the motion between two 'objects', which in turn depends on effective interaction surface area. It shows charge being accumulated by the wind stripping electrons from the sail of the boat, leaving the sail positively charged. Among other problems, the charge that can be acquired is typically very small.
  
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How sailboats use physics to sail upwind:
+
The third panel shows the boat being blown sideways by the wind, which a sideways-facing boat hull would highly resist (see below). This motion of a charged body through the {{w|Earth's magnetic field}}, however,  results in a {{w|Lorentz force}}. Depending upon the relative directions of motion and the magnetic field, this ''could'' generate a perpendicular force in the direction the hull is pointing, as indicated, assuming the entire premise was even as promised.
  
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[A schematic boat with a sail is shown (top-down view). Winds shown with directional arrows (going towards 4:30 on a clock face).]
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The final panel demonstrates this force diverting the downwind (and sideways) motion of the boat forward. As well as the various other problems that exist with the whole scenario, this is contrary to promise of allowing the boat to sail upwind, as the originally indicated wind direction and the finally indicated path results, if anything, in movement slightly downwind.
  
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[Panel 2]
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The title text invokes further {{w|technobabble}} to suggests using a magnetised {{w|centreboard|retractable keel}} to adjust the nature of the forces. It conflates {{w|ocean current}}s (the global flow of water) and {{w|electric current}}s (the movement of charged particles). Perhaps from the supposed ability to move the magnet through the charge, as opposed to the other way round. It invokes the "Laplace force", which is just a {{w|Lorentz force#Force on a current-carrying wire|technical variation}} of the Lorentzian one.
  
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1. Wind passing over the sail strips away electrons via the triboelectric effect.
+
Sailing into the wind was also the topic of [[3013: Kedging Cannon]].
  
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[Schematic similar to panel 1, but with charged ions shown across both sides of the sail]
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=== The More Correct Explanation ===
 +
[[File:Forces on sails for three points of sail.jpg|thumb|An indication of the forces on a sailboat in various directions relative to the wind direction. V<sub>T</sub> is the true velocity of the wind, V<sub>A</sub> is the apparent velocity, as seen by the moving boat. Various forces (F) arise from the way the wind hits the sail, which translate into the forward velocity of the boat, V<sub>B</sub>.]] The actual manner of how a boat is able to sail into the wind relies upon the way the wind hits the boat's angled (and curved) sail, producing forces that are divided between those in the direction the boat is heading and perpendicular to it. Sideways forces encounter resistance from the water, leaving a net motion forward, a direction through the water by which a boat hull is designed to more easily pass. This allows a boat to sail at an angle into the wind (though not directly into it), with the right use of sails. The same effect also allows you to travel faster ''with'' the wind, at a slight angle away from its direction, than if you just ran exactly in its direction; using the sail square on will limit you to going no faster (and usually significantly slower than) the wind that you are relying upon to push you, whereas an angled sail and boat track can convert the forces into greater speed than even the following wind.
  
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[Panel 3]
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Your speed of sailing perpendicular to the wind tends to be greater than that which you can achieve heading at any angle into the wind, but this is no use if you wish to sail to a destination directly where the wind is coming from. Aiming at an angle into the wind and {{w|Tacking (sailing)|tacking}} (briefly use your existing speed to turn directly across the wind), lets you combine sets of aiming off to slightly one side of the wind and doing the same slightly to the other, as required to reach your destination. The expert sailor can choose the {{w|point of sail}} to the wind that makes for the fastest journey time, combining the possible speed and the necessary amount of additional distance. Similarly, turns ('{{w|jibe}}s') across the wind allow a more optimal passage to a directly downwind destination than running straight with it.
  
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2. The positively charged boat is blown downwind; its movement in Earth's magnetic field produces a Lorentz force.
+
Supposing that the comic physics ''had'' been more capable of doing what it suggests, tacking/gibing could also be important concepts. With two sails made of different materials, one could unfurl that which is able to accumulate a positive charge (by losing electrons) or else another that accumulates a negative charge (by 'borrowing' electrons from the air). In this way, you could account for how the effective direction (and {{w|Magnetic declination|declination}}) of the magnetic field would be different for any given location, wind direction and intended destination and ''perhaps'' eventually make progress in whichever direction the vessel is required to go.
  
−
[A force vector is shown in direction of wind, and a perpendicular force vector (along 1:30 on watch face) is shown with a dashed arrow.]
+
==Transcript==
 +
:[Four panels show a schematic sail boat, seen from above, to indicate how it can sail into the wind. In the first panel the boat is heading straight up in the panel. The sail is fixed at the bow and describes a slight curve going to the right of the boat and then curving to the left, ending close to the stern. The rudder can be seen behind the boat. Five arrows, pointing towards 4:30 on a clock face, are drawn at the top left part of the boat, indicating the direction of the wind. There is a frame above the drawing of the boat with text. And then the arrows are labeled, and small lines going to the sail and the hull of the boat connects with two more labels:]
 +
:How sailboats use physics to sail upwind:
 +
:Wind
 +
:Boat
 +
:Sail
  
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[Panel 4]
+
:[In the second panel the boat is drawn similar to panel 1, but the wind arrow have been changed to showing how the wind now blows past the sail on either side. This is done with two lines of three arrows that goes on either side of the sail, and the second and third arrow bends to follow the curve of the sail. Charged ions are shown across both sides of the sail with positive on the left side of the sail, (over the hull of the boat) and negative on the right side, over the sea to the right and behind the boat. The positive charges are small + signs in circles and the negative minus signs in circles. Above the drawing there is the following text:]
 +
:1. Wind passing over the sail strips away electrons via the triboelectric effect.
  
−
3. The Lorentz force acts perpendicular to the direction of motion, redirecting the boat upwind.
+
:[In the third panel the boat has turned towards right and has been moved closer to the bottom of the panel (this could be to acomodate more text above though). The entire hull is now covered in positive charges. A large broad dashed vector is shown going in the direction of the wind. The arrow is not over the boat but on either side of it, with the arrow head ending right of the stern of the boat. Two thin arrows are shown above the end of the force vector. A short solid arrow, that points along the same direction as the large arrow. And then a dashed arrow is drawn perpendicular to the first of these thin arrows (pointing along 1:30 on a clock face. Above the drawing there is the following text:]
 +
:2. The positively charged boat is blown downwind; its movement in Earth's magnetic field produces a Lorentz force.
  
−
[A net force vector is shown perpendicular to downstream vector.]
+
:[In the fourth panel the boat has turned even more towards right and is back to the same height in the panel as the first two panels. The entire hull is still covered in positive charges. The broad dashed vector is still shown, but after starting in the wind direction it can be seen to turn slightly upwards before reaching the boat. And then when it comes out the other side of the boat it points in the direction of the bow of the boat, the arrow ending in front and a bit to the right of the boat. The two thin arrows from before are now shown to the left of the boat , with the short solid arrow pointing along the same direction as the start of the large arrow. And then a the dashed arrow drawn perpendicular to the first of these thin arrows pointing in the direction the boat is sailing. Above the drawing there is the following text:]
 +
:3. The Lorentz force acts perpendicular to the direction of motion, redirecting the boat upwind.
  
 +
{{comic discussion}}<noinclude>
  
−
{{comic discussion}}<noinclude>
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[[Category:Physics]]

Latest revision as of 08:22, 20 May 2025

Sail Physics
Turning in other directions can be accomplished by using a magnetized centerboard and ocean currents, since a current flowing through a magnetic field induces a Laplace force.
Title text: Turning in other directions can be accomplished by using a magnetized centerboard and ocean currents, since a current flowing through a magnetic field induces a Laplace force.

    Explanation[edit]

    Ambox notice.png This explanation is incomplete:
    This page was created by a wind-blown electron from a man on a boat. Don't remove this notice too soon. If you can fix this issue, edit the page!

    This comic starts off looking like a typical explanation of how sailboats can travel upwind — a topic that continues to spark debate and refinement in physics circles. However, it quickly takes a strange tack into a completely fictional and incorrect theory involving triboelectric charging and the Lorentz force, rather than referencing real mechanisms like airfoil aerodynamics.

    This humor works at another level — most interaction of physical things at macro scale (humans and boat sized objects) are electromagnetic in nature. So one unaware of sailing mechanics may start to explain the situation with electromagnetism, and could come to this line of thinking, but it is wrong. If we are to consider this, we find that either no force is appearing in the direction shown, or very little.

    The first panel is a fairly accurate diagram used to explain the reasons why a boat can sail into the wind (see below), it just sets up the scenario.

    The second panel portrays the triboelectric effect, which is transfer of static charge through the motion between two 'objects', which in turn depends on effective interaction surface area. It shows charge being accumulated by the wind stripping electrons from the sail of the boat, leaving the sail positively charged. Among other problems, the charge that can be acquired is typically very small.

    The third panel shows the boat being blown sideways by the wind, which a sideways-facing boat hull would highly resist (see below). This motion of a charged body through the Earth's magnetic field, however, results in a Lorentz force. Depending upon the relative directions of motion and the magnetic field, this could generate a perpendicular force in the direction the hull is pointing, as indicated, assuming the entire premise was even as promised.

    The final panel demonstrates this force diverting the downwind (and sideways) motion of the boat forward. As well as the various other problems that exist with the whole scenario, this is contrary to promise of allowing the boat to sail upwind, as the originally indicated wind direction and the finally indicated path results, if anything, in movement slightly downwind.

    The title text invokes further technobabble to suggests using a magnetised retractable keel to adjust the nature of the forces. It conflates ocean currents (the global flow of water) and electric currents (the movement of charged particles). Perhaps from the supposed ability to move the magnet through the charge, as opposed to the other way round. It invokes the "Laplace force", which is just a technical variation of the Lorentzian one.

    Sailing into the wind was also the topic of 3013: Kedging Cannon.

    The More Correct Explanation[edit]

    An indication of the forces on a sailboat in various directions relative to the wind direction. VT is the true velocity of the wind, VA is the apparent velocity, as seen by the moving boat. Various forces (F) arise from the way the wind hits the sail, which translate into the forward velocity of the boat, VB.
    The actual manner of how a boat is able to sail into the wind relies upon the way the wind hits the boat's angled (and curved) sail, producing forces that are divided between those in the direction the boat is heading and perpendicular to it. Sideways forces encounter resistance from the water, leaving a net motion forward, a direction through the water by which a boat hull is designed to more easily pass. This allows a boat to sail at an angle into the wind (though not directly into it), with the right use of sails. The same effect also allows you to travel faster with the wind, at a slight angle away from its direction, than if you just ran exactly in its direction; using the sail square on will limit you to going no faster (and usually significantly slower than) the wind that you are relying upon to push you, whereas an angled sail and boat track can convert the forces into greater speed than even the following wind.

    Your speed of sailing perpendicular to the wind tends to be greater than that which you can achieve heading at any angle into the wind, but this is no use if you wish to sail to a destination directly where the wind is coming from. Aiming at an angle into the wind and tacking (briefly use your existing speed to turn directly across the wind), lets you combine sets of aiming off to slightly one side of the wind and doing the same slightly to the other, as required to reach your destination. The expert sailor can choose the point of sail to the wind that makes for the fastest journey time, combining the possible speed and the necessary amount of additional distance. Similarly, turns ('jibes') across the wind allow a more optimal passage to a directly downwind destination than running straight with it.

    Supposing that the comic physics had been more capable of doing what it suggests, tacking/gibing could also be important concepts. With two sails made of different materials, one could unfurl that which is able to accumulate a positive charge (by losing electrons) or else another that accumulates a negative charge (by 'borrowing' electrons from the air). In this way, you could account for how the effective direction (and declination) of the magnetic field would be different for any given location, wind direction and intended destination and perhaps eventually make progress in whichever direction the vessel is required to go.

    Transcript[edit]

    [Four panels show a schematic sail boat, seen from above, to indicate how it can sail into the wind. In the first panel the boat is heading straight up in the panel. The sail is fixed at the bow and describes a slight curve going to the right of the boat and then curving to the left, ending close to the stern. The rudder can be seen behind the boat. Five arrows, pointing towards 4:30 on a clock face, are drawn at the top left part of the boat, indicating the direction of the wind. There is a frame above the drawing of the boat with text. And then the arrows are labeled, and small lines going to the sail and the hull of the boat connects with two more labels:]
    How sailboats use physics to sail upwind:
    Wind
    Boat
    Sail
    [In the second panel the boat is drawn similar to panel 1, but the wind arrow have been changed to showing how the wind now blows past the sail on either side. This is done with two lines of three arrows that goes on either side of the sail, and the second and third arrow bends to follow the curve of the sail. Charged ions are shown across both sides of the sail with positive on the left side of the sail, (over the hull of the boat) and negative on the right side, over the sea to the right and behind the boat. The positive charges are small + signs in circles and the negative minus signs in circles. Above the drawing there is the following text:]
    1. Wind passing over the sail strips away electrons via the triboelectric effect.
    [In the third panel the boat has turned towards right and has been moved closer to the bottom of the panel (this could be to acomodate more text above though). The entire hull is now covered in positive charges. A large broad dashed vector is shown going in the direction of the wind. The arrow is not over the boat but on either side of it, with the arrow head ending right of the stern of the boat. Two thin arrows are shown above the end of the force vector. A short solid arrow, that points along the same direction as the large arrow. And then a dashed arrow is drawn perpendicular to the first of these thin arrows (pointing along 1:30 on a clock face. Above the drawing there is the following text:]
    2. The positively charged boat is blown downwind; its movement in Earth's magnetic field produces a Lorentz force.
    [In the fourth panel the boat has turned even more towards right and is back to the same height in the panel as the first two panels. The entire hull is still covered in positive charges. The broad dashed vector is still shown, but after starting in the wind direction it can be seen to turn slightly upwards before reaching the boat. And then when it comes out the other side of the boat it points in the direction of the bow of the boat, the arrow ending in front and a bit to the right of the boat. The two thin arrows from before are now shown to the left of the boat , with the short solid arrow pointing along the same direction as the start of the large arrow. And then a the dashed arrow drawn perpendicular to the first of these thin arrows pointing in the direction the boat is sailing. Above the drawing there is the following text:]
    3. The Lorentz force acts perpendicular to the direction of motion, redirecting the boat upwind.

    comment.png  Add comment      new topic.png  Create topic (use sparingly)     refresh discuss.png  Refresh 

    Discussion

    After the last step, the sailors would then need to ground the boat to avoid being pushed in a circle, wouldn't they? Sophon (talk) 20:47, 16 May 2025 (UTC)

    But if you ground the boat you won't be able to go anywhere. At least until the tide comes in a bit further.162.158.216.191 15:00, 19 May 2025 (UTC)

    Note that for eastward wind, the boat will be propelled upwards, while the opposite is true for westward winds. This provides a basis for the functioning of airships and planes (Helicopters are more complicated, and additionally rely on their own magnetic fields) 162.158.217.45 21:21, 16 May 2025 (UTC)

    Hence why you should always touch an earthing rod before approaching a helicopter, to avoid the magnetism pulling you into their rotors. Kev (talk) 03:11, 17 May 2025 (UTC)

    Is this actually wrong? Wouldn't it still be a force on a sailboat, even if it's not the strongest? Smurfton (talk) 22:20, 16 May 2025 (UTC)

    I added some explaination on direction and magnitude of the lorentz force, maybe that will help - sga 172.68.234.227 (talk) 22:33, 16 May 2025 (UTC) (please sign your comments with ~~~~)
    Yeah, is it more or less effective than the kedging cannon? StapleFreeBatteries (talk) 23:47, 18 May 2025 (UTC)

    The explanation states that of the four forces, only the electromagnetic force operates at the macro level. This is incorrect, as gravity is also directly observable by humans. There should also probably be a link to https://en.wikipedia.org/wiki/Airfoil to provide an explanation for how sails actually allow a boat to sail upwind. I recommend removing the remark about the poles potentially flipping in the future, as this is irrelevant. 172.68.55.124 23:52, 16 May 2025 (UTC)

    What i meant was, for 2 objects at scales of humans =, maybe did not prase it well. In this case, it is the wind and the sail. Wind does not have a "mass" (the atoms most certainly do, but) we essentially have a pressure force, or momentum of wind, where instead of using the energy of atoms (and hence the mass) as given by kinetic theory is not used (that is random (as given by boltzman maxwell statistics)) and uniform (in the sense that for any direction, number of particles going against and towards is equal) and what we have is just pressure applied by a effective "group velocity" of the wind atoms. The gravity interaction between wind and boat, or the local waves and boat is negligible, and planetary gravity is not considered because that is not relavant for in plane motion. the pole fillping was added just for future proofing the article. I am sorry for the puns. I have rewwritten some parts, and reduced the part about pole flipping, and also added the average case scenario for the force, hope it is better now. - sga 172.70.143.75 (talk) 02:37+, 17 May 2025 (please sign your comments with ~~~~)
    That is one huge rambling paragraph, if it's (mostly) yours. I'm no stranger to writing huge rambling paragraphs, myself, but I gave up only a little way in on trying to make it read better. Grammatically, prosaically and with relevence.
    May I suggest that each 'frame' is treated to its own (shorter) paragraph, explaining what effect it tries to convey, what logic it individually tries to follow, but where it fails and what actual forces dominate a true example. (e.g. the hull-shape, including keel, helping convert roughly lateral sideways forces into forward ones against the water; those lateral ones having already been a conversion of largely head-on winds in the first place, thus two "almost up to 90 degree" redirections of force allow very nearly a 180-degree reversal of wind-blown movement. Feel free to discuss the comparisons and differences between 'flappy sail', though blown taught by the air, and an 'upright aircraft wing' solid design. ...See, told you I could ramble, but someone can surely do better at segmenting and summarising the basics of this.) 172.71.178.32 08:32, 17 May 2025 (UTC)

    This is super embarrassing to admit, but I came here to verify whether this was a serious thing or not. I had no idea how a sailboat sails against the wind. Catgofire (talk) 23:58, 16 May 2025 (UTC)

    You aren't alone - I think I was an adult before I understood tacking in the sailboat sense of the word. 162.158.174.127 02:45, 17 May 2025 (UTC)
    I'm wanting to add in some wisdom about "science-y" explanations that appear to be sensible but are completely wrong, segueing into how generative language models appear to be far more reliable than they are. However this margin is too narrow Kev (talk) 03:09, 17 May 2025 (UTC)
    To answer the question: sailboats move by using the Coriolis effect. That's why sailboats can't sail directly in the direction of Earth's spin, and why ships often get becalmed at the equator. Modern vessels create their own Coriolis effect by using steam powered turbines as gyroscopes. RegularSizedGuy (talk) 16:52, 18 May 2025 (UTC)

    I've been really annoyed with ExplainXKCD in the last few months ever since the initial posting has always been LLM generated. It requires more brain power to make sense of AI slop and edit it, than to contribute to a blank page. 162.158.162.103 162.158.162.103 (talk) 15:44, 17 May 2025 (please sign your comments with ~~~~)

    I don't think that LLM has been used for the most troublesome bits. LLMs can 'hallucinate', but tend (unless specifically asked) to make a lot more grammatical sense if you don't look too much further. 162.158.33.240 18:29, 17 May 2025 (UTC)

    Any chance we can add an explanation of how it *actually* works? 162.158.216.174 10:03, 17 May 2025 (UTC)

    Through judicious angling of sail, wind (from any direction other than fully head-on) is deflected(/uses 'wing-effect') to create a force, trying to push the boat, that might be mostly sideways but also a bit forward. Because of the shape of the hull, any sideways force is resisted by the water, reinforcing the remaining forward component which the hull is far more ready to take advantage of. Enough sail (and enough stability to resist rolling) gives a large amount of movement towards, but not exactly towards, the wind. 172.69.224.72 10:41, 17 May 2025 (UTC)

    The joke is that the most commonly used explanation for why flow over a foil generates lift - particles going one way have a longer way to travel than the other, which generates a difference in speed and therefore a pressure differential - is wrong. 172.69.109.91 (talk) 10:36, 17 May 2025 (please sign your comments with ~~~~)

    What is wrong with the explanation which you say is wrong? What is the more correct explanation? 172.71.150.33 20:28, 17 May 2025 (UTC)
    That explanation usually implies/assumes that the portion of air going above the wing and the portion going below have to arrive at the other edge of the wing at the same time. So if a particle that happened to go underneath took exactly x seconds, then an identical particle that happened to go over would also take exactly x seconds. This turns out not to be true. It is true that (most wing-generated) lift comes from a pressure differential, and it is generally true enough most of the time that most (not all) of that pressure differential is tied to an airstream speed differential. (I say "tied to" because I am not in the mood to argue about how the causality runs.) JimJJewett (talk) 06:41, 18 May 2025 (UTC)

    The picture seems to show an axis of rotation (the mast) for the sail being on the end of the sail. Is that correct for a certain class of sailing vessel?~~ 162.158.146.128 (talk) 15:57, 17 May 2025 (please sign your comments with ~~~~)

    Yes. Though offhand, I can't think of a good sailboat with only 1 sail where it was true beyond a first approximation. JimJJewett (talk) 06:41, 18 May 2025 (UTC)
    There's the catboat class, and a smaller dinghy may not have (or always use) a foresail. Obviously it doesn't look like a square-rigger 'sail hanger' of most larger ships, but a mast with a single outward stretch of sail fabric is a very good way to demonstrate how any given sail sits in the wind, without complicating matters by showing a combination of gaff-rigged, bermuda-style, spritzers, etc. 162.158.74.14 17:50, 18 May 2025 (UTC)

    Currently the explanation says "most interaction of physical things at macro scale (humans and boat sized objects) are electromagnetic in nature" I have certainly read that, and have seen examples of electromagnetic interactions between atoms. However, I also encounter explanations that describe interactions in terms of Pauli exclusion principle (see for instance Contact force). This makes me question the view presented in the first sentence. Since my physics is a bit rusty I haven't tried to fix it, but I think it may need clarification. 172.71.150.33 20:28, 17 May 2025 (UTC)

    I split up the example calculating Lorentz force on a boat. It still needs some work (I was just untangling it so I could see what it said). The paragraph about one coulomb of charge I left as is - it needs untangling, so be bold. In the example - somebody should recheck the math (I just copied what there, but in changing units to be more familiar, like km/h, I might have introduced errors). I also changed the field strength to the right order of magnitude for Earth's surface, and multiplied the wind speed by 10 to compensate. As best I can figure the numbers for the example may have been chosen to get a force of 1 Newton. (I can't see any other reason for the ludicrous wind speed of thousands of km/h.) Might be better example to use a reasonable wind speed (e.g. dial it back to hurricane force) and a reasonable charge (something like what you could accumulate with an automobile, or when you zap yourself after getting out of a car seat) wind up with an even more negligible force. Then we could dispense with the paragraph explaining why 1 Coulomb is silly. 172.71.151.93 22:15, 17 May 2025 (UTC)

    If anybody wants to restore parts of it or play with it, the version with the calculation of Lorentz forces is here [1] I thought it somewhat interesting just as physics problem to show what the effect was.
    I got curious about how much charge is involved when one zaps oneself on a car seat. A lighting bolt is a few coulombs. 172.71.142.188 23:40, 17 May 2025 (UTC)

    Extreme apologies to an(other) IP editor who may have made several possibly great improvements to the article. I had so many problems with what was already there that I did a massive rewrite and set things up so differently that I'm not sure that (at a very long glance, but maybe not as long as it diserves) much of that effort is really worth feeding back in. Or even capable of being. Obviously, it's up to the rest of the you (including the person/people I overrode) to make your own judgement about that. I will also go back in to carefully check what I may have desecrated. 162.158.74.68 22:37, 17 May 2025 (UTC)

    No problem. I remade a few tweaks. The calculation is linked above is anybody wants to restore part of it. 172.71.142.188 23:40, 17 May 2025 (UTC)

    Talking of multiple sails (as the explanation does, at least right now), I'm reminded of a children's SF-based book I read when I was... well, a child. It was set on a (mostly) waterworld, as I recall, that had multiple suns (in orbit around it..? ...already we can be sure it was probably not the hardest of hard-SF settings, of course). The boats/skiffs/whatever had multiple sails to move around. Multiple solar sails. Depending upon which ones were deployed (kite-surfing-like), they'd get pushed (and you'd get pulled) by the sun that they were for. So if you wanted to go <- thataway, deploy one particular sail, or thataway -> deploy another instead. As if solar sails even work that way. (Or even would work that way as effectively as a kite might in the... I presume there was an atmosphere... if there wasn't, then that'd explain the need for no-air sail-like solution, but raise significant other questions ...though clearly could not raise kites.) I may have misremembered some of the details, even perhaps some of the 'wrongness', but... I definitely remember I had to suspend quite a lot of disbelief (don't ask me from which sun it is hung!) when I read that. 172.68.205.187 23:25, 17 May 2025 (UTC)

    I was just looking at some things about solar sails and similar. This comic got me curious about: Whether one could use a solar sail to sail "upwind"? -- you can - thanks to gravity and orbital mechanics. e.g., Sail in direction of your orbit - shifts apogee out, perigee in. Whether you could build a {{w|magnetic sail))? -- yes - doesn't work quite like the one in the comic (sun provides wind of particles, sail is magnet to redirect them). There is also a version of solar sail using electric fields to redirect charged particles. One question I haven't found anything about is do solar sails (conventional ones, not electric) accumulate charge, and what effects that might have. I just mention here in case anybody thinks way makes sense in comic explanation. 172.71.142.188 23:40, 17 May 2025 (UTC)

    Well, if you send charge along a long conductor (which might be what you do if you're sending/receiving the sail-charge through the thing that the sail is attached to the payload with), and pass through any magnetic fields (planetary, solar... galactic?) then you're into the territory of the Electrodynamic tether as also useful for propulsion. 172.68.205.187 00:24, 18 May 2025 (UTC)

    Related to the question of how sails might work (against the wind), and the relationship to wing effects, I'm reminded of how a comedy radio sitcom dealt with the wings thing. In case it's not quickly obvious (and with some non-obvious info added), characters are Arthur ('simple' but questioning Air Steward), Carolyn (his mother, bossy owner of the airplane and chief Air Steward/everything else that's not actually flying), Martin (chief pilot/captain, knowledgable but inexperienced) and Douglas (second in command, but senior in years and experience and 'street smart'/air-smart to the point of (usually well-deserved) smugness).

    Excerpt dialogues from Cabin Pressure, series(/season) 1, episode 1
    [Arthur:] No, never! It’s just always exciting! That amazing moment when twelve tons of metal leaves the earth – and no-one knows why!
    [Carolyn:] Yes, we do.
    [Arthur:] Yeah, but ...you know, not really. I mean, we know you need wings and engines and a ...sticky-up bit on the end for some reason, but it’s not like we actually know why a plane stays in the air.
    [Carolyn:] No, no, Arthur, we really do. We-we do, we do know that.
    [Arthur:] Oh! How, then?
    [Carolyn:] Well ...er, because...
    [...some minor diversionary tactics break the conversation all too briefly...]
    [Carolyn:] Because there are four forces acting on the plane, and so long as two of them are bigger than the other two, the plane flies.
    [Arthur:] ...Mum, I don’t mind that no-one knows.
    [Carolyn:] But we do! We do! That’s it! What I said: that’s how.
    [Arthur:] Well, what are the four forces, then?
    [Carolyn:] Yes! Well, I will tell you what they are. Lift ...weight ...er...
    [Arthur:] Up and down?
    [Carolyn:] No, no, no, no, no. Tho-Those are up and down. No, it’s lift, weight...
    [Arthur:] Left and right.
    [Carolyn:] No, no, no, no. Lift, weight...
    [Arthur:] En...gines?
    [Carolyn:] No, no ...well, yes, yes, yes, sort of. Um, thrust, thrust. Lift, weight, thrust and...
    [Arthur:] Time.
    [Carolyn:] Drag. Lift, weight, thrust and drag. So, the weight and drag are overcome because the engines give the plane thrust, and the wings give it lift. And that’s how a plane flies.
    [Arthur:] How do the wings give it lift?
    [Carolyn:] What?
    [Arthur:] The wings are really heavy. How does bolting two ginormous lumps of metal to a ginormous lump of metal give it lift?
    [Carolyn:] Well, because they are wings. Well, they’re like birds’ wings.
    [Arthur:] Yeah, but birds’ wings flap. Ours don’t flap. They’ve got flaps, but I once watched the flaps all the way to Stockholm and, take it from me, they are seriously mis-named. So-so why does having wings make a plane leave the runway?
    [conveniently timed distraction occurs to take Carolyn away...]
    [Arthur:] Yeah, but how do the wings...
    [...letting the conversation and action move on, until...]
    [Douglas:] And now it’s back to the boring old plane flying.
    [Arthur:] Oh, yes. About that. Um, I wanted to ask you something, Skipper. Mum was telling me this morning that planes fly because they’ve got wings.
    [Douglas:] Is there anything that woman doesn’t know?
    [Arthur:] But she didn’t really explain – why do wings lift us up?
    [Douglas:] Ah, well. Essentially...
    [Martin:] Uh, Douglas, he asked me. Listen carefully, Arthur. The wing is curved on top but flat on the bottom. When it meets the air, it splits it in two. The air that goes over the top has further to go, so it has to go faster to keep up with the air underneath. That reduces the pressure above the wing, giving us lift.
    [Arthur:] Ah, fantastic! Thanks, Skipper! I totally get it now.
    [Martin:] You’re welcome.
    [Arthur:] Except ...why does it have to?
    [Martin:] Why does what what?
    [Arthur:] Why does the air on the top have to keep up with the air on the bottom? Why don’t they just split up?
    [pause]
    [Douglas:] ...for the sake of the kids?
    [action moves on again, until...]
    [...they need to distract Arthur from something else]
    [Douglas:] Arthur, you were asking why the air over the wing has to keep up with the air underneath.
    [Arthur:] Ooh, yes. Do you know?
    [Douglas:] Indeed I do. Attend: the air is not passing over the wing; the wing is passing through the air, so the curved upper side stretches the air forced over it apart, reducing pressure, producing lift. The lift pushes up; the weight pushes down – so as long as the lift is more than the weight, up we go. And that, my friend, is how an aeroplane flies.
    [Arthur:] Got it! Right, yes! Cracking! I completely get it now.
    [Douglas:] Good. You see, it’s actually quite easy to grasp when it’s explained properly by someone who understands...
    [Arthur:] So that’s why planes can’t fly upside down.
    [Douglas:] Er, yes they can.
    [Arthur:] Can they?
    [Douglas:] Well, of course they can. Haven’t you seen the Red Arrows?
    [Arthur:] But ...doesn’t that mean the curved side of the wing is on the bottom, so the lift is pushing down as well as the weight? How does that work?
    [Martin:] Yes, Douglas. How does that work?
    [Douglas:] Well, Arthur, there’s a very simple explanation; but just to finish what we were saying, Martin...

    [...the something else is raised as a distraction from the question]

    [Douglas:] No-one wants to hear the explanation. What a shame.

    ...just thought anyone who hadn't heard this (or had, but liked the comedy involved) might like to read it. 172.68.205.187 00:24, 18 May 2025 (UTC)

    Sounds like comic 803. StapleFreeBatteries (talk) 23:21, 18 May 2025 (UTC)
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