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On May 22, 5:36 pm, Some Other Guy wrote:
BDS wrote: There is an interesting article in Flying magazine by Peter Garrison that talks about lift theory. I thought that one of the most interesting points he made was that the lift force generated by an airfoil is greater at the optimum angle of attack than would be the force imparted to it if you were to move it through the air perpendicular to the air flow at the same speed. I first experienced this as a kid, sticking my hand out the car window with the thumb as a leading edge, forming a crude airfoil. When at the right shape and angle of attack, the lift is amazingly strong. I always found it remarkable that when my hand was completely perpendicular to the wind, the force didn't seem as strong. Definitely a visceral lesson in lifting versus stalling. I have a copy of that article here. Very, very good. The coefficient of lift, as he described it, was a ratio related to the lift generated by a unit area of wing compared to the flat-plate drag created by the same unit area perpendicular to the airflow. The Wright brothers did this in their wind tunnel, so they were able to develop efficient airfoils. A common airfoil (NACA 23012, IIRC) has a max lift coefficient of 1.8 , which means that it generates 1.8 times the lift as the drag of the perpendicular surface of the same area. He made things really clear when he pointed out that this is why boats and ships no longer use paddlewheels. The wheel will produce forward thrust equivalent to the power required to force the paddle back through the water, while the propeller (they call it a "screw") will produce much more forward thrust for the same torque required by the paddlewheel. So it's a process to cause the air to exert a force in a direction perpendicular to the airflow. It fools the air, if you like, which is why we call it an "air foil." A foil is a device to deceive. Bernoulli is right, and so is Newton. There's a pressure difference because of the difference in airspeeds between top and bottom, and there's a movement of air downward to which there's an upward reaction. The equal-transit time theory is bogus, since the airfoil is much more efficient than that theory would imply. See this page: http://www.av8n.com/how/htm/airfoils.html And, again, Mxmanic has declared, for about the 12th time, that positive AOA is necessary for lift. If this was so, and it isn't, and he has been shown many times that it isn't, then airfoils like the Clark Y wouldn't generate lift at AOAs as low as -4 degrees. That's negative 4 degrees, airfoil chord pointing downward. A graph can be found a third of the way down this page: http://lpmpjogja.diknas.go.id/kc/a/air/airplane.htm That page also deals properly with both Newton and Bernoulli. Dan |
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On May 23, 12:46*pm, wrote:
* * * So it's a process to cause the air to exert a force in a direction perpendicular to the airflow. It fools the air, if you like, which is why we call it an "air foil." A foil is a device to deceive. Nonsense, the derivation is from a blade or leaf. Cheers |
#3
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Foiled again!
On May 23, 5:56 am, More_Flaps wrote: On May 23, 12:46 pm, wrote: So it's a process to cause the air to exert a force in a direction perpendicular to the airflow. It fools the air, if you like, which is why we call it an "air foil." A foil is a device to deceive. Nonsense, the derivation is from a blade or leaf. Cheers |
#5
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![]() "Bertie the Bunyip" wrote in message ... Good link but I think he kind of munged up the lift/drag thing as being seperate entities, when they're inextricably linked. IOW you create lift and drag is a by product. Not to say, BTW, that the correlation is rigid! Bertie Where did you read that dumb ass, ya got a link? |
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"Maxwell" luv2^fly99@cox.^net wrote in news:aPAZj.2623$7k1.2040
@newsfe24.lga: "Bertie the Bunyip" wrote in message ... Good link but I think he kind of munged up the lift/drag thing as being seperate entities, when they're inextricably linked. IOW you create lift and drag is a by product. Not to say, BTW, that the correlation is rigid! Bertie Where did you read that dumb ass, ya got a link? Nope, I know it. Bertie |
#7
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On May 23, 7:52 am, Bertie the Bunyip wrote:
wrote i So it's a process to cause the air to exert a force in a direction perpendicular to the airflow. It fools the air, if you like, which is why we call it an "air foil." A foil is a device to deceive. Actually it's a synonym for blade. Not quite. From the Merriam-Webster Dictionary: Foil: 1 obsolete : trample 2 a: to prevent from attaining an end : defeat always able to foil her enemies b: to bring to naught : thwart (foiled the plot) synonyms: see frustrate. So my "deceive" is much less accurate than "frustrate." Your definiton matches one of the the Cambridge Dictionary's definitions: foil (SWORD) gatiful noun [C] a thin light sword used in the sport of fencing Dan |
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wrote in news:380a3b72-e9e1-4b9f-86a5-
: On May 23, 7:52 am, Bertie the Bunyip wrote: wrote i So it's a process to cause the air to exert a force in a direction perpendicular to the airflow. It fools the air, if you like, which is why we call it an "air foil." A foil is a device to deceive. Actually it's a synonym for blade. Not quite. From the Merriam-Webster Dictionary: Foil: 1 obsolete : trample 2 a: to prevent from attaining an end : defeat always able to foil her enemies b: to bring to naught : thwart (foiled the plot) synonyms: see frustrate. So my "deceive" is much less accurate than "frustrate." Your definiton matches one of the the Cambridge Dictionary's That definition isn't relevant to this application, though. definitions: foil (SWORD) gatiful noun [C] a thin light sword used in the sport of fencing More relevant, I suppose, but that definition is dervied from leaf or blade as well. Foil as in thwart and foil as in blade have two completely different origins, from waht I've been able to find... http://www.thefreedictionary.com/foil So I'd say arfoil was not used becasue of it's ability to frustrate air ( engineers just don't think like that, they seek harmony) but more because of their resemblance to a leaf or blade. Actually, the one in that link that stands out is the architectural one. Bertie |
#9
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On May 24, 2:59*am, wrote:
On May 23, 7:52 am, Bertie the Bunyip wrote: wrote i * * * So it's a process to cause the air to exert a force in a direction perpendicular to the airflow. It fools the air, if you like, which is why we call it an "air foil." A foil is a device to deceive. Actually it's a synonym for blade. Not quite. From the Merriam-Webster Dictionary: * * Foil: 1 obsolete : trample 2 a: to prevent from attaining an end : defeat always able to foil her enemies b: to bring to naught : thwart (foiled the plot) synonyms: see frustrate. * * * So my "deceive" is much less accurate than "frustrate." * * * *Your definiton matches one of the the Cambridge Dictionary's definitions: If you look a bit further in the MW disctionary you will see both blade and keaf. But the key is to use a proper dictionary like the OED. Your definition of foil is a verb, not a noun and an aerofoil or air foil is a noun. Cheers |
#10
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![]() "Bertie the Bunyip" wrote in message ... Good link but I think he kind of munged up the lift/drag thing as being seperate entities, when they're inextricably linked. IOW you create lift and drag is a by product. Not to say, BTW, that the correlation is rigid! Bertie Posted by a forger. |
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