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NORDHAVN Rewrites Physics Textbooks
"Steve Firth" wrote in message ... Paul Cassel wrote: Steve Firth wrote: Bill wrote: Umm well we can, water can be made to flow up hill on a slope. http://www.livescience.com/environment/060329_water_uphill.html No, it can't. The water is propelled by steam. It's not flowing, it's boiling. And steam makes a frictionless cushion so it should be shooting downhill. There was also another URL which you have conveniently snipped from your reply. And water vapor goes up to make clouds all without the help of scientists or steam. Gravity does not exist at the LaGrangian point. Oil droplets could go up or down under the control of Milliken. If one accelerates toward the earth at the correct rate the gravitational field disappears. Photons do not change speed due to acceleration in the earth's gravitational field. They change colour. Electrons can exist in large, dense clusters without repelling each other. A clock runs at two different rates for two observers travelling at different speeds. In spite of all these wonders there still ain't no such thing as a free lunch. Also no matter how you turn your boat in a calm, the wind is always directly on your nose. If you're not moving how can the wind be on your nose? |
NORDHAVN Rewrites Physics Textbooks
"toad" wrote in message oups.com... On 14 Oct, 16:52, Andy Champ wrote: toad wrote: Care to explain why a windmill which is capable of powering itself forward against it's own drag can only do it with a true wind? How does it know if the wind it is 'feeling' is true or not, it has no concept of true wind which is merely the wind speed and direction at an arbitary stationary point. There will be a level of gearing low enough somewhere, so that the boat can wind itself forward against the winch. Even so, if the true wind is zero you get no excess of power whatever you do. How does the windmill know the wind is not true wind? It has no concept of 'true' wind, it lives exclusively in apparent wind. Assume the windmill direct into wind concept works: You can take your windmill cart, put it on another cart and tow it at 20kts. It sees 20kts and will move forwards along its cart. If you stop the cart and blow 20kts at the windmill cart it will move forwards at exactly the same speed. In other words there is some spare energy left over to drive the cart forwards after the energy required to hold the windmill in equilibrium with the wind is expended. In my example above that spare energy is used to drive the cart forwards but in your example of the windmill on the foredeck that surplus energy can be used to save petrol. Now we both accept that idea is laughable so you have to explain why it's not laughable when the wind blowing is caused by nature. ...but most importantly, why oh why oh why doesn't someone just post the mathmatical proof, the last time this came up I said I'd leave the thread 'till proof turned up and none did. Odd that. http://www.boatdesign.net/forums/showthread.php?t=14182 Reality beats proof. |
NORDHAVN Rewrites Physics Textbooks
Umm well we can, water can be made to flow up hill on a slope.
http://www.livescience.com/environment/060329_water_uphill.html No, it can't. The water is propelled by steam. It's not flowing, it's boiling. And steam makes a frictionless cushion so it should be shooting downhill. There was also another URL which you have conveniently snipped from your reply. "Bill" wrote: And water vapor goes up to make clouds all without the help of scientists or steam. Nice backpedal. You really urped on that one "Bill." Gravity does not exist at the LaGrangian point. Yes it does. Gravity always exists. At a LaGrange point, the gravity of one mass is cancelled by the mass of another. So gravity has no effect on free bodies at a LaGrange point, but gravity still exists. Oil droplets could go up or down under the control of Milliken. Wrong again. Oil droplets could appear to go up or down under his telekinetic control. "Seems" is not the same as "is" no matter how much it appears to be. If one accelerates toward the earth at the correct rate the gravitational field disappears. Nope. It is cancelled out by the acceleration (the "correct rate" happens to be 32 ft/sec/sec, or about 1 g.... how difficult is it to figure this out?) but gravity never "disappears." Photons do not change speed due to acceleration in the earth's gravitational field. They change colour. An energy effect nontheless. Does a net change in energy always cause a change in velocity and only a change in velocity? There are other forms of energy. A clock runs at two different rates for two observers travelling at different speeds. No they don't. They run at different rates relative to the observers. In other words, "Bill" you flunked the physics test and you don't know as much as you think you do. In spite of all these wonders there still ain't no such thing as a free lunch. Got that one right.... the 1/2 pt extra credit doesn't save your grade though. DSK |
NORDHAVN Rewrites Physics Textbooks
Wilbur Hubbard wrote:
"Stephen Trapani" wrote in message ... If the apparent wind, say, decreases *any* resistance by, say lifting the boat a fraction, or changing the effective hull shape that is hitting the water, then NORDHAVN's statement is technically correct. Poppycock! NORDHAVN's statement is fiction. Pure fiction! Had they said light air instead of dead air they would have been correct on any point of sail other than with the wind dead ahead but they didn't say that. They said dead air which means NO WIND. No wind will always cause the apparent wind to be from dead ahead when motoring ahead and this dead ahead wind can't impart any forward force to the boat because it can only shake the sails around and cause drag on the sails and rigging which slows the boat. Any chance they have some type of special rigging or innovative hull shape to make what they are saying true? Ever seen what a dead air wind dead ahead can do for an airplane? Stephen |
NORDHAVN Rewrites Physics Textbooks
"Bill" wrote in message ... "toad" wrote in message oups.com... On 14 Oct, 16:52, Andy Champ wrote: toad wrote: Care to explain why a windmill which is capable of powering itself forward against it's own drag can only do it with a true wind? How does it know if the wind it is 'feeling' is true or not, it has no concept of true wind which is merely the wind speed and direction at an arbitary stationary point. There will be a level of gearing low enough somewhere, so that the boat can wind itself forward against the winch. Even so, if the true wind is zero you get no excess of power whatever you do. How does the windmill know the wind is not true wind? It has no concept of 'true' wind, it lives exclusively in apparent wind. Assume the windmill direct into wind concept works: You can take your windmill cart, put it on another cart and tow it at 20kts. It sees 20kts and will move forwards along its cart. If you stop the cart and blow 20kts at the windmill cart it will move forwards at exactly the same speed. In other words there is some spare energy left over to drive the cart forwards after the energy required to hold the windmill in equilibrium with the wind is expended. In my example above that spare energy is used to drive the cart forwards but in your example of the windmill on the foredeck that surplus energy can be used to save petrol. Now we both accept that idea is laughable so you have to explain why it's not laughable when the wind blowing is caused by nature. ...but most importantly, why oh why oh why doesn't someone just post the mathmatical proof, the last time this came up I said I'd leave the thread 'till proof turned up and none did. Odd that. http://www.boatdesign.net/forums/showthread.php?t=14182 Reality beats proof. I'm surprised that the fact that this (windmill boat sailing directly upwind) is viable isn't intuitively obvious to more people. A sailboat tacking upwind is an airscrew blade (the sail(s)) driving a waterscrew blade (the keel), operating in their respective mediums. There is no inherent difference between the back-and-forth motion of the conventional sailboat to the rotary motion of the 'windmill' type boat. Another mental experiment would be to think of a very wide catamaran with a side-to-side track on which runs a car which holds the mast and sail above and a centerboard sticking into the water below. Both are angled and a mechanism in the 'car' causes both to change angle towards the center of the catamaran when either end is reached. The 'car' effectively 'tacks' back and forth on it's track while the catamaran moves straight ahead into the wind. |
NORDHAVN Rewrites Physics Textbooks
On 15 Oct, 05:33, "John Smith" x@y wrote:
"Bill" wrote in message ... "toad" wrote in message roups.com... On 14 Oct, 16:52, Andy Champ wrote: toad wrote: Care to explain why a windmill which is capable of powering itself forward against it's own drag can only do it with a true wind? How does it know if the wind it is 'feeling' is true or not, it has no concept of true wind which is merely the wind speed and direction at an arbitary stationary point. There will be a level of gearing low enough somewhere, so that the boat can wind itself forward against the winch. Even so, if the true wind is zero you get no excess of power whatever you do. How does the windmill know the wind is not true wind? It has no concept of 'true' wind, it lives exclusively in apparent wind. Assume the windmill direct into wind concept works: You can take your windmill cart, put it on another cart and tow it at 20kts. It sees 20kts and will move forwards along its cart. If you stop the cart and blow 20kts at the windmill cart it will move forwards at exactly the same speed. In other words there is some spare energy left over to drive the cart forwards after the energy required to hold the windmill in equilibrium with the wind is expended. In my example above that spare energy is used to drive the cart forwards but in your example of the windmill on the foredeck that surplus energy can be used to save petrol. Now we both accept that idea is laughable so you have to explain why it's not laughable when the wind blowing is caused by nature. ...but most importantly, why oh why oh why doesn't someone just post the mathmatical proof, the last time this came up I said I'd leave the thread 'till proof turned up and none did. Odd that. http://www.boatdesign.net/forums/showthread.php?t=14182 Reality beats proof. I'm surprised that the fact that this (windmill boat sailing directly upwind) is viable isn't intuitively obvious to more people. Intuitively it does seem obvious. As do all the best perpetual motion machines. It's only when you think about it that the flaws become apparent and you start to look around to look for the figures. ...and there are none. The last time this came up we had a 300 post argument fest and still nobody was able prove it worked. As for reality beats proof. FFS. There was a photo of a perpetual motion machine in the daily mail a few weeks back. |
NORDHAVN Rewrites Physics Textbooks
On 14 Oct, 17:18, "Bill" wrote:
Read this about lift: http://home.hccnet.nl/m.holst/LiftDrag.html Particularly the part about "by definition lift does NOT do work". What force do you think does work against gravity to allow aeroplanes to ascend? Ian |
NORDHAVN Rewrites Physics Textbooks
On 14 Oct, 23:07, (Steve Firth) wrote:
If you're not moving how can the wind be on your nose? Motoring? What you wrote before was "If one is motoring in a calm on a flat millpond then there is an apparent wind equal to the speed of the boat from dead ahead." You then seemed to claim that by changing course this apparent wind could be made to do useful work. Ian |
NORDHAVN Rewrites Physics Textbooks
On 14 Oct, 19:14, (Steve Firth) wrote:
toad wrote: How does the windmill know the wind is not true wind? It has no concept of 'true' wind, it lives exclusively in apparent wind. Most amusing that you call me a troll for pointing out that this also applies to motor sailers. But you seem to be claiming that a sail can produce forward force from a headwind. It's obvious how a windmill might do that, but a sail ... ? Ian |
NORDHAVN Rewrites Physics Textbooks
On 15 Oct, 07:09, toad wrote:
Intuitively it does seem obvious. As do all the best perpetual motion machines. It's only when you think about it that the flaws become apparent and you start to look around to look for the figures. ...and there are none. The last time this came up we had a 300 post argument fest and still nobody was able prove it worked. Toad, my dear fellow, please don't make an arse of yourself over this yet again. Windmill powered sailing boats which can go directly upwind have been built many times. Details have been given here - have you been to see the one in the Scottish Maritime Museum yet? As I recall, your main failure to understand came from thinking that there was only a windmill involved, so it case you have forgotten, please remember that all these designs use a PROPELLOR IN THE WATER COUPLED TO THE WINDMILL. Ian |
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On 15 Oct, 07:41, Ian wrote:
As I recall, your main failure to understand came from thinking that there was only a windmill involved, so it case you have forgotten, please remember that all these designs use a PROPELLOR IN THE WATER COUPLED TO THE WINDMILL. Errr, no. My failure to understand is I don't know how much energy a windmill can harness, and I don't know how much energy is required to push a windmill into the wind. What mechanism turns that energy into forward motion is irrelevant. If the surplus energy is there it can be used to drive the boat with any mechanism you choose. If the energy a windmill can harness is greater than the energy required to push it onto the wind it must go forward. Claiming I don't understand is rather futile. Of course, _I_ don't understand. The point is you claim you do. So post the figures that you base your understanding on and then I will share the same understanding and this issue will be put to bed for good: 20kts of wind on the nose. Assume no friction or drag anywhere in the system apart from the push backwards on the windmill. How fast does it go. Show your workings. |
NORDHAVN Rewrites Physics Textbooks
On Sun, 14 Oct 2007 23:31:30 -0700, Ian
wrote: What force do you think does work against gravity to allow aeroplanes to ascend? Thrust from the engine, of course. Casady |
NORDHAVN Rewrites Physics Textbooks
On Mon, 15 Oct 2007 00:09:08 -0700, toad
wrote: 20kts of wind on the nose. Assume no friction or drag anywhere in the system apart from the push backwards on the windmill. How fast does it go. Show your workings. If it is unobvious that a windmill can power a prop and proceed upwind consider something similar on land, with a rack and the pinion on the machine. They do make gear driven railroads, there is one at Pike's Peak. Why wouldn't it accellerate indefinitely with no friction anywhere in the system. In real life, of course, props are not very efficient. Casady |
NORDHAVN Rewrites Physics Textbooks
On 15 Oct, 14:27, (Richard Casady) wrote:
Why wouldn't it accellerate indefinitely with no friction anywhere in the system. .....because as it approaches the speed of light it will require infinate energy. |
NORDHAVN Rewrites Physics Textbooks
On 15 Oct, 08:09, toad wrote:
On 15 Oct, 07:41, Ian wrote: As I recall, your main failure to understand came from thinking that there was only a windmill involved, so it case you have forgotten, please remember that all these designs use a PROPELLOR IN THE WATER COUPLED TO THE WINDMILL. Errr, no. My failure to understand is I don't know how much energy a windmill can harness, and I don't know how much energy is required to push a windmill into the wind. What mechanism turns that energy into forward motion is irrelevant. If the surplus energy is there it can be used to drive the boat with any mechanism you choose. Well, you went completely silent the last time the presence of a propellor was pointed out to you. I think it was pretty obvious that you didn't realize its significance. But here - yet a-bloody-gain - is what you need to know. 1) There is a downwind force on the windmill. 2) There is a change of wind speed across the disk of the windmill. 3) The shaft power produced by the windmill is the downwind force times the change in wind speed. 4) The power required to move the windmill disk relative to a fixed point is the force multiplied by the upwind velocity component of the disk 4a) So to move the disk directly upwind requires power, 4b) To move the disk downwind produces power (in addition to any shaft power) and 4c) To move the disk across wind requires no power 5) The shaft power produced by the windmill may be fed into a device capable of moving the windmill - gears, propellor, paddles, generator and linear electric motor. 6) If, after efficiency has been taken into account, the shaft power produced by the windmill is greater than the power needed to move it, it will move. 6a) So a windmill craft will always be able to go down wind 6b) Will be able to go crosswind if the shaft power equals the propellor losses and 6c) Will be able to go directly upwind as long as the shaft power exceeds the propellor losses, the maximum speed attainable upwind being determined by the size of those losses. If the energy a windmill can harness is greater than the energy required to push it onto the wind it must go forward. Good. Since the energy required to push it into the wind is proportional to the absolute forward speed of the disk, it can be as small as you like. To - again bearing in mind inefficiences in the propulsion system - any available shaft power can produce forward motion. QED. Claiming I don't understand is rather futile. Of course, _I_ don't understand. The point is you claim you do. So post the figures that you base your understanding on and then I will share the same understanding and this issue will be put to bed for good: Can I assume that you have a rasonable base in fluid dynamics and Kelvin-Froude actuator disk theory? 20kts of wind on the nose. Assume no friction or drag anywhere in the system apart from the push backwards on the windmill. How fast does it go. Show your workings. You have given insufficient information. But the important thing to remember is ... IT HAS BEEN DONE. By lots of people. I've seen one of the vessels capable of doing it myself - it used to live at Tighnabruiach and is now in the Scottish Maritime Museum Collection. Arguing about theoretical possibilities is one thing. Arguing that, because you don't understand the theory, working machines are mass delusions is a little bit silly. Ian |
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On 15 Oct, 14:27, (Richard Casady) wrote:
Why wouldn't it accellerate indefinitely with no friction anywhere in the system. Kelvin-Froude actuator disk theory is your friend. Ian |
NORDHAVN Rewrites Physics Textbooks
On 15 Oct, 14:19, (Richard Casady) wrote:
On Sun, 14 Oct 2007 23:31:30 -0700, Ian wrote: What force do you think does work against gravity to allow aeroplanes to ascend? Thrust from the engine, of course. Nope. How many aircraft do you think are capable of vertical takeoff? A Boeing 747-400 has a take off weight of 875,000 lbf and a total thrust of 4 x 63,300 = 253,200 lbf. My own aircraft has a take off mass of 370kg and no thrust whatsoever, and yet I can get it to go up. Ian |
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On 15 Oct, 15:54, Ian wrote:
Claiming I don't understand is rather futile. Of course, _I_ don't understand. The point is you claim you do. So post the figures that you base your understanding on and then I will share the same understanding and this issue will be put to bed for good: Can I assume that you have a rasonable base in fluid dynamics and Kelvin-Froude actuator disk theory? No, but I will be able to verify your formulas and check your maths fine. 20kts of wind on the nose. Assume no friction or drag anywhere in the system apart from the push backwards on the windmill. How fast does it go. Show your workings. You have given insufficient information. Fine, make you own assumptions - just explain what the are when you post the maths. |
NORDHAVN Rewrites Physics Textbooks
wrote in message oups.com... Umm well we can, water can be made to flow up hill on a slope. http://www.livescience.com/environment/060329_water_uphill.html No, it can't. The water is propelled by steam. It's not flowing, it's boiling. And steam makes a frictionless cushion so it should be shooting downhill. There was also another URL which you have conveniently snipped from your reply. "Bill" wrote: And water vapor goes up to make clouds all without the help of scientists or steam. Nice backpedal. You really urped on that one "Bill." Please explain. I don't understand your comment. Gravity does not exist at the LaGrangian point. Yes it does. Gravity always exists. At a LaGrange point, the gravity of one mass is cancelled by the mass of another. So gravity has no effect on free bodies at a LaGrange point, but gravity still exists. How does one know it exists there? By measuring it? Or by postulating it? If gravity of one mass is cancelled by another then it does not exist, the net force is zero. Zero means nothing. Anyway, you are completely wrong. Gravity can be higher at a Lagrangian point provided it is countered by acceleration forces. It says so on this NASA website: http://www-spof.gsfc.nasa.gov/Education/wlagran.html "There exists another Lagrangian point L2 at about the same distance from Earth but on the night side, away from the Sun. A spacecraft placed there is more distant from the Sun and therefore should orbit it more slowly than the Earth; but the extra pull of the Earth adds up to the Sun's pull, and this allows the spacecraft to move faster and keep up with the Earth. " Here we see no cancellation of gravity at all. Your definition of a Langrangian point is incorrect. There are many places in space where there is no local gravity. Oil droplets could go up or down under the control of Milliken. Wrong again. Oil droplets could appear to go up or down under his telekinetic control. "Seems" is not the same as "is" no matter how much it appears to be. Milliken won the Nobel Prize for measuring the charge to mass ratio of electrons. He used an electric field to lift or drop oil droplets. "Telekinetic control" is in the realm of pseudoscience. Milliken was not a stage actor who entertained audiences, he was a real scientist who discovered some of the fundamentals we use today. Here is some information on the man and the experiment: http://en.wikipedia.org/wiki/Oil-drop_experiment I may be missing something, but could you refer me to where he used "Telekinetic control" on the oil droplets. There is some controversy over his fudging of the data which would indicate he could not use his mind to control the outcome of the experiment. Could you explain more please? If one accelerates toward the earth at the correct rate the gravitational field disappears. Nope. It is cancelled out by the acceleration (the "correct rate" happens to be 32 ft/sec/sec, or about 1 g.... how difficult is it to figure this out?) but gravity never "disappears." Gravitational field disappears to the observer. The correct rate depends on altitude and location over the earth. See: http://en.wikipedia.org/wiki/Gravity_anomaly http://www.bun.kyoto-u.ac.jp/~suchii/free-fall.html Quotes Einstein as follows: "Just as is the case with the electric field produced by electromagnetic induction, the gravitational field has similarly only a relative existence. For if one considers an observer in free fall, e.g. from the roof of a house, there exists for him during his fall no gravitational field---at least in his immediate vicinity. (A. Einstein, manuscript written in 1919" Photons do not change speed due to acceleration in the earth's gravitational field. They change colour. An energy effect nontheless. Does a net change in energy always cause a change in velocity and only a change in velocity? There are other forms of energy. Actually it causes a net change in momentum which is a change in velocity or mass or one looks at the total differential. Furthermore a change in color is a change in velocity, the photon vibrates about its central position faster or slower according to its new frequency. If it maintains the same amplitude and a higher frequency it must oscillate faster. Where do you think the higher energies come from at higher frequencies (shorter wavelengths)? Since the ensemble velocity is fixed and the mass is fixed then the velocity of oscillation must increase to account for the higher energy. Velocity is the only form of energy. Heat is the movement of particles, electromagnetic energy is the movement of charge, etc. Potential energy (energy not realized) is the only form not involving velocity because it is static. Furthermore, the velocity must be relative to a reference. A clock runs at two different rates for two observers travelling at different speeds. No they don't. They run at different rates relative to the observers. I'm talking about a single clock. Why are you talking about 2 clocks? All measurement is relational. In other words, "Bill" you flunked the physics test and you don't know as much as you think you do. By your standard? Please correct my responses to your comments above. In spite of all these wonders there still ain't no such thing as a free lunch. Got that one right.... the 1/2 pt extra credit doesn't save your grade though. I look forward to your help and comments with my replies to your scientifically astute and accurate commentary. It's not often we get someone here who really knows their **** and is willing to help others. Thanks immensely. Bill DSK |
NORDHAVN Rewrites Physics Textbooks
"Ian" wrote in message ups.com... On 14 Oct, 17:18, "Bill" wrote: Read this about lift: http://home.hccnet.nl/m.holst/LiftDrag.html Particularly the part about "by definition lift does NOT do work". What force do you think does work against gravity to allow aeroplanes to ascend? Ian Work = force x distance |
NORDHAVN Rewrites Physics Textbooks
"Ian" wrote in message oups.com... On 14 Oct, 19:14, (Steve Firth) wrote: toad wrote: How does the windmill know the wind is not true wind? It has no concept of 'true' wind, it lives exclusively in apparent wind. Most amusing that you call me a troll for pointing out that this also applies to motor sailers. But you seem to be claiming that a sail can produce forward force from a headwind. It's obvious how a windmill might do that, but a sail ... ? Ian The sailboat does go forward doesn't it? (Hint: break down the vectors) |
NORDHAVN Rewrites Physics Textbooks
"toad" wrote in message ups.com... On 15 Oct, 05:33, "John Smith" x@y wrote: "Bill" wrote in message ... "toad" wrote in message roups.com... On 14 Oct, 16:52, Andy Champ wrote: toad wrote: Care to explain why a windmill which is capable of powering itself forward against it's own drag can only do it with a true wind? How does it know if the wind it is 'feeling' is true or not, it has no concept of true wind which is merely the wind speed and direction at an arbitary stationary point. There will be a level of gearing low enough somewhere, so that the boat can wind itself forward against the winch. Even so, if the true wind is zero you get no excess of power whatever you do. How does the windmill know the wind is not true wind? It has no concept of 'true' wind, it lives exclusively in apparent wind. Assume the windmill direct into wind concept works: You can take your windmill cart, put it on another cart and tow it at 20kts. It sees 20kts and will move forwards along its cart. If you stop the cart and blow 20kts at the windmill cart it will move forwards at exactly the same speed. In other words there is some spare energy left over to drive the cart forwards after the energy required to hold the windmill in equilibrium with the wind is expended. In my example above that spare energy is used to drive the cart forwards but in your example of the windmill on the foredeck that surplus energy can be used to save petrol. Now we both accept that idea is laughable so you have to explain why it's not laughable when the wind blowing is caused by nature. ...but most importantly, why oh why oh why doesn't someone just post the mathmatical proof, the last time this came up I said I'd leave the thread 'till proof turned up and none did. Odd that. http://www.boatdesign.net/forums/showthread.php?t=14182 Reality beats proof. I'm surprised that the fact that this (windmill boat sailing directly upwind) is viable isn't intuitively obvious to more people. Intuitively it does seem obvious. As do all the best perpetual motion machines. It's only when you think about it that the flaws become apparent and you start to look around to look for the figures. ...and there are none. The last time this came up we had a 300 post argument fest and still nobody was able prove it worked. As for reality beats proof. FFS. There was a photo of a perpetual motion machine in the daily mail a few weeks back. The guy who built the windmill boat could be a lying crackpot. I have not seen one with my own eyes so your point is valid. |
NORDHAVN Rewrites Physics Textbooks
"Richard Casady" wrote in message ... On Mon, 15 Oct 2007 00:09:08 -0700, toad wrote: 20kts of wind on the nose. Assume no friction or drag anywhere in the system apart from the push backwards on the windmill. How fast does it go. Show your workings. If it is unobvious that a windmill can power a prop and proceed upwind consider something similar on land, with a rack and the pinion on the machine. They do make gear driven railroads, there is one at Pike's Peak. Why wouldn't it accellerate indefinitely with no friction anywhere in the system. In real life, of course, props are not very efficient. Casady Things can go to infinity: http://www.oddparts.com/acsi/motortut.htm "Caution: If a DC motor suffers a loss of field (if for example, the field power connections are broken), the DC motor will immediately begin to accelerate to the top speed which the loading will allow. This can result in the motor flying apart if the motor is lightly loaded. The possible loss of field must be accounted for, particularly with shunt wound DC motors. " Here the back EMF of the motor is redirected into the armature and the motions speeds up infinitely until it flies apart. |
NORDHAVN Rewrites Physics Textbooks
"Wilbur Hubbard" wrote in message anews.com... "toad" wrote in message s.com... On 14 Oct, 15:16, (Steve Firth) wrote: Nor in the case of the motorsailer will the apparent wind be from dead ahead. Oh yes it will! If only these ******s could learn to draw a simple vector diagram. They would soon see there are no other vectors than one from the rear (motor power) and one from the front (apparent wind drag). Duh! The vector from the rear will be longer than the one from the front. But the one from the front will effectively shorten the vector from the rear. The result is a slower forward speed than if the boat was powering forward in a vacuum where there would be no vector from the forward (from the apparent wind, at least.) Only when there is some wind other than apparent wind can you add any sort of sideways vector to the diagram. The advert is WRONG! It demonstrates a common ignorance that many sailor harbour. Wilbur Hubbard Best way to look at it! |
NORDHAVN Rewrites Physics Textbooks
"Stephen Trapani" wrote in message ... Ronald Raygun wrote: Wilbur Hubbard wrote: "Steve Firth" wrote in message .. . Wilbur Hubbard wrote: Among other things, they claim to be able to create something from nothing. The advert states, "Even in dead air the apparent wind when motorsailing generates lift and reduces the amount of engine power needed to maintain the same speed the engine would produce on its own." Huh? Tell me I ain't dreaming . . . You're not dreaming, they're right and you don't understand physics. Is there any more help that you need? I had the utmost confidence that the post would usher forth the Looney bin, perpetual motion crowd! Welcome, to you, sir. It's good to see a Brit is the first to insert his foot into his mouth. Well, perhaps the idea is that when sailing into a "dead" wind, the sails be set horizontally, so that the lift generated by them is in the direction which is traditionally associated with "lift", i.e. "up". Like hydrofoils, these aerofoils would cause the hull to ride a fraction of an inch higher in the water, reducing water resistance. Alternatively, the idea might be to back the sails, which would generate a sideways force on the boat, so that it actually travels with some leeway. If the leeway angle is big enough, and the drag from all this doesn't slow down the forwards speed much, the effective speed will be enhanced by the Pythagoras effect. The helm must be instructed to steer a few degrees off the intended destination, to compensate for this beneficial leeway. Ronald Raygun might be right, if the boat is designed in such a way to take advantage of these effects. The actual effect proposed by NORDHAVN will have to be known to know if Wilbur is entirely wrong, but we do know that Wilbur is partly wrong because NORDHAVN doesn't claim any type of perpetual motion, just that they can return *some* energy back to the system to *lessen* the energy needed to propel the boat. Stephen There is perpertual motion. I will cite 3 examples, which are irrefutable. 1. Law of inertia. An object in motion tends to stay in motion (perpertually) unless acted upon by an outside force. That's the law! 2. The electrons spinning around atoms. They have been doing it since the beginning of time. The stout electron never tires, never wears out, never slows down he just keeps going and going. What powers the little bugger? If he required power the universe would have stopped a long time ago. He can orbit under just about any condition, anytime and anyplace. 3. Electromagnetic waves and photons. Current theory has them going on and on forever, never slowing down. Our world is bathed in perpertual motion. One has only to look and think. Bill |
NORDHAVN Rewrites Physics Textbooks
On 15 Oct, 16:20, "Bill" wrote:
"toad" wrote in message The guy who built the windmill boat could be a lying crackpot. I have not seen one with my own eyes so your point is valid. You wouldn't have to lie. Natural wind isn't all in one direction. You could be steaming ahead in your windmill boat on the components of the wind that are not directly on the nose and really believe yourself to be sailing upwind. Pyro actually posted a picture of his cart working - but in the photo he was blowing downwards on it. He wasn't lying, he realy did think it was going upwind, he just didn't have a handy head protractor! It's also worth noting that some of the windmill craft identified in the course of this 'debate' as craft that could sail directly into wind turn out to be incapable of going direct into wind! It's a futile to debate this in words. We need figures. It will be resolved one day when somebody who genuinely knows (as opposed to guessing based on gut feeling and justifying it with wordy posts using analogies) simply posts the worked formula to prove it one way or the other. You only have to look at the Conundrum thread to realize just how much of a pinch of salt you have to take with armchair physicists on usenet! |
NORDHAVN Rewrites Physics Textbooks
Steve Firth wrote:
If one is motoring in a calm on a flat millpond then there is an apparent wind equal to the speed of the boat from dead ahead. Hoist a sail and you can make no use of that wind, agreed. However that only applies if you maintain the same course. Now do what any sensible bloke would do and adjust your course to make use of the wind as well as the motor. You now have wind in your sails and you still have an apparent wind. If you look at the force triangle there is still a component from the apparent wind. But since you are creating this apparent wind yourself from your own forward motion, it will come from dead ahead wherever you go. Changing course will not bring the apparent wind aft so that you can use it. Jeannette |
NORDHAVN Rewrites Physics Textbooks
"Jeannette" wrote in message t... Steve Firth wrote: If one is motoring in a calm on a flat millpond then there is an apparent wind equal to the speed of the boat from dead ahead. Hoist a sail and you can make no use of that wind, agreed. However that only applies if you maintain the same course. Now do what any sensible bloke would do and adjust your course to make use of the wind as well as the motor. You now have wind in your sails and you still have an apparent wind. If you look at the force triangle there is still a component from the apparent wind. But since you are creating this apparent wind yourself from your own forward motion, it will come from dead ahead wherever you go. Changing course will not bring the apparent wind aft so that you can use it. Jeannette Suppose the boat could be trimmed under the waterline so it moved in the water skewed. Then the apparent wind could come in several degrees off of the bow. Then would it work? Bill |
NORDHAVN Rewrites Physics Textbooks
"toad" wrote in message ps.com... On 15 Oct, 14:27, (Richard Casady) wrote: Why wouldn't it accellerate indefinitely with no friction anywhere in the system. ....because as it approaches the speed of light it will require infinate energy. My flashlight shoots out photons at the speed of light and it is powered by a 1 1/2 volt battery. Even better, my flashlight moves away from the photons at the speed of light with the same 1 1/2 volt battery. When do I need to change the battery? |
NORDHAVN Rewrites Physics Textbooks
"Ian" wrote in message oups.com... On 15 Oct, 14:27, (Richard Casady) wrote: Kelvin-Froude actuator disk theory is your friend. Isn't that valid only in the inertial range? |
NORDHAVN Rewrites Physics Textbooks
"toad" wrote in message ups.com... On 15 Oct, 16:20, "Bill" wrote: "toad" wrote in message The guy who built the windmill boat could be a lying crackpot. I have not seen one with my own eyes so your point is valid. You wouldn't have to lie. Natural wind isn't all in one direction. You could be steaming ahead in your windmill boat on the components of the wind that are not directly on the nose and really believe yourself to be sailing upwind. Pyro actually posted a picture of his cart working - but in the photo he was blowing downwards on it. He wasn't lying, he realy did think it was going upwind, he just didn't have a handy head protractor! It's also worth noting that some of the windmill craft identified in the course of this 'debate' as craft that could sail directly into wind turn out to be incapable of going direct into wind! It's a futile to debate this in words. We need figures. It will be resolved one day when somebody who genuinely knows (as opposed to guessing based on gut feeling and justifying it with wordy posts using analogies) simply posts the worked formula to prove it one way or the other. You only have to look at the Conundrum thread to realize just how much of a pinch of salt you have to take with armchair physicists on usenet! If the windmill did work we could put small wind turbines on bicycles and reduce the pedaling load for cyclists and even increase their speeds into strong headwinds. Or just cut the field current on their dc powered assist motors and watch them cruise off into the sunset - perpertually! |
NORDHAVN Rewrites Physics Textbooks
Steve Firth wrote:
If you're not moving how can the wind be on your nose? You are MOTORING. That means MOVING. You can't motor / move on, say course 180 degrees in a dead calm and then turn say 40 degrees to port and expect the resultant relative wind to help your progress because the relative wind is always directly on your nose. Yes, the steam would make the water move in many directions but the point is that it's not RUNNING uphill. It's being propelled uphill. |
NORDHAVN Rewrites Physics Textbooks
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NORDHAVN Rewrites Physics Textbooks
Gravity does not exist at the LaGrangian point.
Yes it does. Gravity always exists. At a LaGrange point, the gravity of one mass is cancelled by the mass of another. So gravity has no effect on free bodies at a LaGrange point, but gravity still exists. "Bill" wrote: How does one know it exists there? By measuring it? Or by postulating it? If gravity of one mass is cancelled by another then it does not exist, the net force is zero. There is a big difference between "does not exist" and "net force = zero." ... Zero means nothing. Anyway, you are completely wrong. Gravity can be higher at a Lagrangian point provided it is countered by acceleration forces. It says so on this NASA website: So, you said gravity doesn't exist, now you say that it not only may exist but that those who know most about it say it is greater; then you say that I'm "completely wrong." Good work. I look forward to your help and comments with my replies to your scientifically astute and accurate commentary. It's not often we get someone here who really knows their **** and is willing to help others. Thanks immensely. You're welcome immensely. DSK |
NORDHAVN Rewrites Physics Textbooks
On 15 Oct, 17:46, "Bill" wrote:
"toad" wrote in message ps.com... On 15 Oct, 14:27, (Richard Casady) wrote: Why wouldn't it accellerate indefinitely with no friction anywhere in the system. ....because as it approaches the speed of light it will require infinate energy. My flashlight shoots out photons at the speed of light and it is powered by a 1 1/2 volt battery. Even better, my flashlight moves away from the photons at the speed of light with the same 1 1/2 volt battery. If you are saying you flashlight moves at the speed of light relative to you, I'm impressed. If your flashlight moves at the speed of light relative to it's own output I'm less impressed! |
NORDHAVN Rewrites Physics Textbooks
On 15 Oct, 17:56, "Bill" wrote:
"toad" wrote in message ups.com... On 15 Oct, 16:20, "Bill" wrote: "toad" wrote in message The guy who built the windmill boat could be a lying crackpot. I have not seen one with my own eyes so your point is valid. You wouldn't have to lie. Natural wind isn't all in one direction. You could be steaming ahead in your windmill boat on the components of the wind that are not directly on the nose and really believe yourself to be sailing upwind. Pyro actually posted a picture of his cart working - but in the photo he was blowing downwards on it. He wasn't lying, he realy did think it was going upwind, he just didn't have a handy head protractor! It's also worth noting that some of the windmill craft identified in the course of this 'debate' as craft that could sail directly into wind turn out to be incapable of going direct into wind! It's a futile to debate this in words. We need figures. It will be resolved one day when somebody who genuinely knows (as opposed to guessing based on gut feeling and justifying it with wordy posts using analogies) simply posts the worked formula to prove it one way or the other. You only have to look at the Conundrum thread to realize just how much of a pinch of salt you have to take with armchair physicists on usenet! If the windmill did work we could put small wind turbines on bicycles and reduce the pedaling load for cyclists and even increase their speeds into strong headwinds. Forget that, you could put windmills on the bonnets of sports cars, gear their output to the drive and turn that 100mph headwind into even more power. |
NORDHAVN Rewrites Physics Textbooks
On Sun, 14 Oct 2007 11:57:47 -0700, toad
wrote: On 14 Oct, 19:38, Andy Champ wrote: Same speed *relative to the the surface it is on*. Yes, so you accept it has spare energy left over after it has overcome the drag of the windmill. So the windmill on the foredeck of our power boat has enough energy to push against the wind pushing back on it. It also has enough energy left over after this to move it forwards. Which means you can gear that spare energy to the engine and save some petrol. Yet you and I both accept you can't do that. So there's a paradox. In other words there is some spare energy left over to drive the cart forwards after the energy required to hold the windmill in equilibrium with the wind is expended. In my example above that spare energy is used to drive the cart forwards but in your example of the windmill on the foredeck that surplus energy can be used to save petrol. Now we both accept that idea is laughable so you have to explain why it's not laughable when the wind blowing is caused by nature. ...but most importantly, why oh why oh why doesn't someone just post the mathmatical proof, the last time this came up I said I'd leave the thread 'till proof turned up and none did. Odd that. Lets take this step by step. Or to put it another way "Lets take this step by step so I can keep talking rather than posting the maths that I claim is simple to prove my case." Do you accept that it is possible for the cart to move directly upwind? It is essential that we assume that to be the case so you can explain the paradox exposed by the windmill on powerboat example. If in a headwind the windmill pushes back harder than it is pushed then it must do that no matter how that headwind comes about. Which leaves us with a power boat with a windmill on it's foredeck getting a net gain in energy from wind that it is creating. No it gets energy from a reduction of the kinetic energy of the _true_ wind. |
NORDHAVN Rewrites Physics Textbooks
wrote in message ups.com... On 15 Oct, 17:46, "Bill" wrote: "toad" wrote in message ps.com... On 15 Oct, 14:27, (Richard Casady) wrote: Why wouldn't it accellerate indefinitely with no friction anywhere in the system. ....because as it approaches the speed of light it will require infinate energy. My flashlight shoots out photons at the speed of light and it is powered by a 1 1/2 volt battery. Even better, my flashlight moves away from the photons at the speed of light with the same 1 1/2 volt battery. If you are saying you flashlight moves at the speed of light relative to you, I'm impressed. If your flashlight moves at the speed of light relative to it's own output I'm less impressed! My flashlight is not that impressive. If it gave off enough photons it could move at the speed of light relative to me. |
NORDHAVN Rewrites Physics Textbooks
"Ian" wrote in message ups.com... On 15 Oct, 14:19, (Richard Casady) wrote: On Sun, 14 Oct 2007 23:31:30 -0700, Ian wrote: What force do you think does work against gravity to allow aeroplanes to ascend? Thrust from the engine, of course. Nope. How many aircraft do you think are capable of vertical takeoff? A Boeing 747-400 has a take off weight of 875,000 lbf and a total thrust of 4 x 63,300 = 253,200 lbf. My own aircraft has a take off mass of 370kg and no thrust whatsoever, and yet I can get it to go up. Ian But in your example, gravity is still causing you to descend through the air. Unless converting excess speed to height, you only climb because the air in which you are flying is rising faster than your sink rate. Presumably, if a boat's motion is generating apparent wind from dead ahead and a fully battened sail (I say fully battened because it's a better aerofoil shape) could be set far enough out to achieve sufficient angle of attack to produce some lift, then a keel boat "may" go a little quicker. Would the lift produced be greater than the drag though? Graham. |
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