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NORDHAVN Rewrites Physics Textbooks
NORDHAVN Rewrites Physics Textbooks
Well-known and well-respected motorboat manufacturer, NORDHAVN has produced a new addition to their lineup, a 56-foot motorsailer called the 56MS. On page 109 of SAIL magazine, October 2007 issue they have a full-page advertisement touting how great it is. 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 . . . Now let me see if I got this straight. In dead air one assumes there is no wind from any direction. Right? Therefore, any motion of the boat produced by the motor in forward gear would result in an apparent wind from dead ahead. Agreed? So, unless they've hired Old Thom Stewart, who knows nothing about apparent wind, to write the ad script there's no way they actually believe this nonsense that sails can be powered up by a wind from directly ahead, is there? Seems to me the sails would just luff and cause drag thus reducing the speed through the water produced by the motor. But, I guess when you're selling motorsailers you can count upon your customers being quite stupid so perhaps some will fall for this ruse. Wilbur Hubbard |
NORDHAVN Rewrites Physics Textbooks
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? |
NORDHAVN Rewrites Physics Textbooks
"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. Wilbur Hubbard |
NORDHAVN Rewrites Physics Textbooks
On 2007-10-13 18:35:33 -0400, "Wilbur Hubbard"
said: 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 . . . Yup, that's advertising BS. If there's no wind, there won't be a benefit while motor-sailing or any other condition. Still, most of the time when there's too little wind for sailing, motor-sailing will benefit from quite a few wind inputs. If nothing else, having a sail aloft will dampen the boat's side-to-side motion much of the time. There are many times on the Chesapeake when having a sail up doesn't mean squat as even a couple of knot's wind speed won't affect anything at all. -- Jere Lull Tanzer 28 #4 out of Tolchester, MD Xan's new pages: http://web.mac.com/jerelull/iWeb/Xan/ Our BVI pages: http://homepage.mac.com/jerelull/BVI/ |
NORDHAVN Rewrites Physics Textbooks
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. |
NORDHAVN Rewrites Physics Textbooks
On Oct 13, 12:46 pm, (Steve Firth) wrote:
Wilbur Hubbard wrote: ... 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 don't have that rag and I looked at the Nordavn web site and they don't make that claim there. If, however, the claim was made as Wilbur represents it then Wilbur is right and Nordhavn is wrong. I'm assuming that "dead air" means that the apparent wind is zero as seen by an object floating freely on the ocean's surface. Over here in the Pacific the term for that condition is "calm". As far as I know, "dead air" means that a broadcast radio station has gone silent. I've never heard it used as a meteorological term. Maybe the ad guy meant "light air", in which case the claim is plausible. -- Tom. |
NORDHAVN Rewrites Physics Textbooks
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NORDHAVN Rewrites Physics Textbooks
Wilbur Hubbard wrote:
It's good to see a Brit is the first to insert his foot into his mouth. Ah no, that would have been you, as usual, Craptain. I bet you think that ice yachts can't reach 146mph either. |
NORDHAVN Rewrites Physics Textbooks
"Wilbur Hubbard" wrote in message anews.com... NORDHAVN Rewrites Physics Textbooks Well-known and well-respected motorboat manufacturer, NORDHAVN has produced a new addition to their lineup, a 56-foot motorsailer called the 56MS. On page 109 of SAIL magazine, October 2007 issue they have a full-page advertisement touting how great it is. 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 . . . Now let me see if I got this straight. In dead air one assumes there is no wind from any direction. Right? Therefore, any motion of the boat produced by the motor in forward gear would result in an apparent wind from dead ahead. Agreed? So, unless they've hired Old Thom Stewart, who knows nothing about apparent wind, to write the ad script there's no way they actually believe this nonsense that sails can be powered up by a wind from directly ahead, is there? Seems to me the sails would just luff and cause drag thus reducing the speed through the water produced by the motor. But, I guess when you're selling motorsailers you can count upon your customers being quite stupid so perhaps some will fall for this ruse. Wilbur Hubbard Their claims are true. I've seen large Nordhaven motorsailers go dead into a strong wind and rise up out of the water from displacement mode onto a full plane. |
NORDHAVN Rewrites Physics Textbooks
Steve Firth wrote:
Wilbur Hubbard wrote: It's good to see a Brit is the first to insert his foot into his mouth. Ah no, that would have been you, as usual, Craptain. I bet you think that ice yachts can't reach 146mph either. Wilbur seems to have it right this time. Either the article is misquoted, very badly written, or just plain wrong. An apparent wind from dead ahead can add nothing but a force directly astern. The case where a true wind from ahead can be used to drive a windmill that can drive a propeller to propel the vessel is different; but this requires a true wind. BTW ice yachts cannot make 146mph *directly* upwind. Andy |
NORDHAVN Rewrites Physics Textbooks
On 14 Oct, 14:17, Andy Champ wrote:
An apparent wind from dead ahead can add nothing but a force directly astern. The case where a true wind from ahead can be used to drive a windmill that can drive a propeller to propel the vessel is different; but this requires a true wind. 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. As far as the windmill is concerned it has a 20kt headwind and (alledgedly) it can take that energy, use some of it to hold itself stationary against the wind and _still_ have surplus energy to drive forwards. If it can do that you could gear it to the engine of the 20kt powerboat and save petrol equivalent to the surplus power that is left over once you subtract the energy required to overcome the windmill's own drag from the total energy harnessed by the windmill. |
NORDHAVN Rewrites Physics Textbooks
"Andy Champ" wrote in message
news:j-idnSDiMoeUio_anZ2dnUVZ8q- An apparent wind from dead ahead can add nothing but a force directly astern. The case where a true wind from ahead can be used to drive a windmill that can drive a propeller to propel the vessel is different I have such a vessel you can buy, she's called "Bhaskara's Wheel". |
NORDHAVN Rewrites Physics Textbooks
Andy Champ wrote:
BTW ice yachts cannot make 146mph *directly* upwind. I didn't say they could, in fact close hauled at those speeds they are usually sailing close to downwind, an apparent wind close to directly ahead. Nor in the case of the motorsailer will the apparent wind be from dead ahead. |
NORDHAVN Rewrites Physics Textbooks
toad wrote:
On 14 Oct, 14:17, Andy Champ wrote: An apparent wind from dead ahead can add nothing but a force directly astern. The case where a true wind from ahead can be used to drive a windmill that can drive a propeller to propel the vessel is different; but this requires a true wind. 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. As far as the windmill is concerned it has a 20kt headwind and (alledgedly) it can take that energy, use some of it to hold itself stationary against the wind and _still_ have surplus energy to drive forwards. If it can do that you could gear it to the engine of the 20kt powerboat and save petrol equivalent to the surplus power that is left over once you subtract the energy required to overcome the windmill's own drag from the total energy harnessed by the windmill. MY recollection of this is that with a windmill it's simply not possible to reduce the drag sufficiently to get a sufficient energy to make it useful. Wingsails are much better at it or even even proeprly trimmed sails. ASCII news isn't the best medium to get the point across, but I'll try. 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. No doubt the craptain also doesn't beleive in back EMF or any of the other phenomena which appear to produce "something from nothing" however it's not the case that something is being produced from nothing and in this case the extra energy is achieved at the usual expense of not being able to sail directly into the apparent wind. |
NORDHAVN Rewrites Physics Textbooks
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! |
NORDHAVN Rewrites Physics Textbooks
On 14 Oct, 15:28, (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. Yet you've just twice denied that to be the case: "Nor in the case of the motorsailer will the apparent wind be from dead ahead." "they're right and you don't understand physics. " If you must troll pick a consistent line of argument. |
NORDHAVN Rewrites Physics Textbooks
On 14 Oct, 15:28, (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. Umm. What happens to the apparent wind from dead ahead when you turn and make "dead ahead" a different direction? Ian |
NORDHAVN Rewrites Physics Textbooks
On 14 Oct, 15:16, (Steve Firth) wrote:
Nor in the case of the motorsailer will the apparent wind be from dead ahead. It's flat calm. Where does the sideways component of the apparent wind come from? Ian |
NORDHAVN Rewrites Physics Textbooks
On 14 Oct, 16:12, Ian wrote:
On 14 Oct, 15:16, (Steve Firth) wrote: Nor in the case of the motorsailer will the apparent wind be from dead ahead. It's flat calm. Where does the sideways component of the apparent wind come from? I fear that the Craptain has finally flipped and has created the Steve Firth ID in order to argue with himself. |
NORDHAVN Rewrites Physics Textbooks
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 |
NORDHAVN Rewrites Physics Textbooks
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. I thought we'd done this to death. Don't think force, think energy. Imagine the boat is still, the wind is blowing over it, and the mill is connected to a winch to a fixed point. There will be a level of gearing low enough somewhere, so that the boat can wind itself forward against the winch. As you increase the gearing, you will increase the amount of power needed to drive the winch. (not the torque, AKA force, but the POWER). As you increase the speed of the winch with more gears you will need more and more power. Be careful when you crunch the numbers on this. Drag from the mill is proportional to the square of the apparent wind, power proportional to its cube, and power to propel the boat proportional to boat speed times drag. If you forget hull and aerodyamic drag and transmission losses you can fool yourself into thinking the boat *will* keep accelerating forever. Even so, if the true wind is zero you get no excess of power whatever you do. This is from an Excel spreadsheet. Real Wind-- 10 Boat Apparent req'd Avail. Excess speed Wind Drag power power Power (%) 1 11 121 121 1331 1000% 2 12 144 288 1728 500% 3 13 169 507 2197 333% 4 14 196 784 2744 250% 5 15 225 1125 3375 200% 6 16 256 1536 4096 167% 7 17 289 2023 4913 143% 8 18 324 2592 5832 125% 9 19 361 3249 6859 111% 10 20 400 4000 8000 100% 100 110 12100 1210000 1331000 10% If I reset the real wind to zero, all the excess power figures go to zero - which implies zero losses in the system. To make it easy for anyone else, the formulae on the "9" line of that read: =A11+1 =A12+B$1 =B12*B12 =C12*A12 =C12*B12 =(E12-D12)/D12 Andy |
NORDHAVN Rewrites Physics Textbooks
"Steve Firth" wrote in message ... toad wrote: On 14 Oct, 14:17, Andy Champ wrote: An apparent wind from dead ahead can add nothing but a force directly astern. The case where a true wind from ahead can be used to drive a windmill that can drive a propeller to propel the vessel is different; but this requires a true wind. 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. As far as the windmill is concerned it has a 20kt headwind and (alledgedly) it can take that energy, use some of it to hold itself stationary against the wind and _still_ have surplus energy to drive forwards. If it can do that you could gear it to the engine of the 20kt powerboat and save petrol equivalent to the surplus power that is left over once you subtract the energy required to overcome the windmill's own drag from the total energy harnessed by the windmill. MY recollection of this is that with a windmill it's simply not possible to reduce the drag sufficiently to get a sufficient energy to make it useful. Wingsails are much better at it or even even proeprly trimmed sails. ASCII news isn't the best medium to get the point across, but I'll try. 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. Doesn't the wind still appear to come from dead ahead? Or does your motion cause the wind to blow? 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. No doubt the craptain also doesn't beleive in back EMF or any of the other phenomena which appear to produce "something from nothing" Back EMF actually works to negate the driving field to zero or to its initial condition. It's more like "nothing from something". however it's not the case that something is being produced from nothing and in this case the extra energy is achieved at the usual expense of not being able to sail directly into the apparent wind. Yes, and the extra energy from back EMF is not usuable either because it is cancelling the driven field. With logic like yours we are only steps away from perpertual motion. Just think of all the extra energy generated by friction - it's "free energy", if only we can redirect it along the applied force we would have all the energy problems solved. Perhaps if one runs or drives in a zig-zag or back and forth motion we can trick friction into going in our favor - just like you do with apparent wind in sails. You whole argument and reasoning is just that - wind in sails. Wilbur Hubbard's mind is not cluttered with useless memorized facts or dimmed with fuzzy thinking. Basic principles and a strong application of rigorous logic brings correct and defendable conclusions. |
NORDHAVN Rewrites Physics Textbooks
Does a properly designed sailboat keel provide forward lift? Same thing? Gordon |
NORDHAVN Rewrites Physics Textbooks
"Gordon" wrote in message ... Does a properly designed sailboat keel provide forward lift? Same thing? Gordon Read this about lift: http://home.hccnet.nl/m.holst/LiftDrag.html Particularly the part about "by definition lift does NOT do work". |
NORDHAVN Rewrites Physics Textbooks
Bill wrote:
Perhaps if one runs or drives in a zig-zag or back and forth motion we can trick friction into going in our favor Umm well we can, water can be made to flow up hill on a slope. http://www.livescience.com/environment/060329_water_uphill.html http://www.telegraph.co.uk/earth/mai...07/10/05/sciwa ter105.xml Wilbur Hubbard's mind is not cluttered with useless memorized facts or dimmed with fuzzy thinking. The Craptains mind is untroubled by thought of any kind. |
NORDHAVN Rewrites Physics Textbooks
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. |
NORDHAVN Rewrites Physics Textbooks
"Andy Champ" wrote in message
... 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. I thought we'd done this to death. Don't think force, think energy. Imagine the boat is still, the wind is blowing over it, and the mill is connected to a winch to a fixed point. There will be a level of gearing low enough somewhere, so that the boat can wind itself forward against the winch. As you increase the gearing, you will increase the amount of power needed to drive the winch. (not the torque, AKA force, but the POWER). As you increase the speed of the winch with more gears you will need more and more power. Be careful when you crunch the numbers on this. Drag from the mill is proportional to the square of the apparent wind, power proportional to its cube, and power to propel the boat proportional to boat speed times drag. If you forget hull and aerodyamic drag and transmission losses you can fool yourself into thinking the boat *will* keep accelerating forever. Even so, if the true wind is zero you get no excess of power whatever you do. This is from an Excel spreadsheet. Real Wind-- 10 Boat Apparent req'd Avail. Excess speed Wind Drag power power Power (%) 1 11 121 121 1331 1000% 2 12 144 288 1728 500% 3 13 169 507 2197 333% 4 14 196 784 2744 250% 5 15 225 1125 3375 200% 6 16 256 1536 4096 167% 7 17 289 2023 4913 143% 8 18 324 2592 5832 125% 9 19 361 3249 6859 111% 10 20 400 4000 8000 100% 100 110 12100 1210000 1331000 10% If I reset the real wind to zero, all the excess power figures go to zero - which implies zero losses in the system. To make it easy for anyone else, the formulae on the "9" line of that read: =A11+1 =A12+B$1 =B12*B12 =C12*A12 =C12*B12 =(E12-D12)/D12 I hope for your sake you are trolling, joking or both. |
NORDHAVN Rewrites Physics Textbooks
On Sun, 14 Oct 2007 15:28:23 +0100, (Steve Firth)
wrote: o doubt the craptain also doesn't beleive in back EMF or any of the other phenomena which appear to produce "something from nothing" however it's not the case that something is being produced from nothing and in this case the extra energy is achieved at the usual expense of not being able to sail directly into the apparent wind. I believe in entropy. The so called extra energy comes directly from the thrust bearing of the engine, and it will drink more with a sail developing lift. I don't necessarily say there is no benefit to having a sail up. Lift means drag. The ratio, in an airplane, is equal to the glide angle. The longer and skinnier the wing the better it will glide. There is a name for that, aspect ratio. Generally low for sails. My father had a gaff rigged schooner: now there is real low. Casady |
NORDHAVN Rewrites Physics Textbooks
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. |
NORDHAVN Rewrites Physics Textbooks
UglyBetty wrote:
I hope for your sake you are trolling, joking or both. I'm not. It's just the knowledge of basic physics in these groups leaves a lot to be desired, and it *really* bugs me. Andy |
NORDHAVN Rewrites Physics Textbooks
On 14 Oct, 19:24, Andy Champ wrote:
UglyBetty wrote: I hope for your sake you are trolling, joking or both. I'm not. It's just the knowledge of basic physics in these groups leaves a lot to be desired, and it *really* bugs me. You can't find it that basic or you'd show the formula for energy required to push a windmill against a certain windstrength, show the formula for energy you can gather from a windmill in a certain windstrengh and triumphantly substitute numbers to prove your case beyond any argument. If you or anyone else on UKRS found the maths "basic" this issue would have been kicked into touch months ago. |
NORDHAVN Rewrites Physics Textbooks
I trust you studied my numbers?
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. It doesn't know the difference. 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. Same speed *relative to the the surface it is on*. 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. Do you accept that it is possible for the cart to move directly upwind? Andy. |
NORDHAVN Rewrites Physics Textbooks
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. |
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. You claimed the apparent wind on boat motoring in a flat calm would not be on the nose. Like saying that if I sit on a motorway in a convertable the wind blast will be coming from the left! |
NORDHAVN Rewrites Physics Textbooks
toad wrote:
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. 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. There are other ways hull design can return energy to the sytem. Look at hydrofoils. NORDHAVN never claim that their design produces a net energy, just that it returns some energy to the system, thus reducing the amount of energy needed to propel the boat. This surely is physically possible. Many designs, like hybrid cars, capture the energy of one engine for another engine which then returns some of that energy. In the sailboat example, this amount may be trivial, but their statement would still be technically correct, if energy is returned. Stephen |
NORDHAVN Rewrites Physics Textbooks
"Ian" wrote in message oups.com... On 14 Oct, 15:28, (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. Umm. What happens to the apparent wind from dead ahead when you turn and make "dead ahead" a different direction? Ian That's where unimaginative folks go astray. If there's no wind and the only wind is the apparent wind, in this case a wind from straight ahead, you can turn the boat through 360 degrees and the wind will continue to be directly on the bow. In other words the apparent wind, when there is no other wind, is the sole function the speed and direction of the boat. It will always come from dead ahead provided the vessel is moving forward. Wilbur Hubbard |
NORDHAVN Rewrites Physics Textbooks
"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. There are other ways hull design can return energy to the sytem. Look at hydrofoils. Sorry but the the 56MS has no hydrofoils. NORDHAVN never claim that their design produces a net energy, just that it returns some energy to the system, thus reducing the amount of energy needed to propel the boat. This surely is physically possible. It is only physically possible if there's a wind and provided the wind is not from dead ahead. It is physically impossible in "dead air" as claimed by NORDHAVN. Wilbur Hubbard |
NORDHAVN Rewrites Physics Textbooks
"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 |
NORDHAVN Rewrites Physics Textbooks
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. Also no matter how you turn your boat in a calm, the wind is always directly on your nose. |
NORDHAVN Rewrites Physics Textbooks
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. 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? |
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