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#91
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Backwash Causes Lift?
Dudley Henriques wrote:
Crash Lander wrote: I'd like to see what his thoughts are on String Theory. LOL. I'm sure he'd most likely say that twine was better :-)) What, and discount the obvious implications that Duct Tape has on modern thinking? TheSmokingGnu |
#92
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Backwash Causes Lift?
"Bertie the Bunyip" wrote It´s the main reason I´m here. Remind me again. What is the main reason you're here? Why do you feel the need to answer his posts? -- Jim in NC |
#93
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Backwash Causes Lift?
Le Chaud Lapin wrote:
You can have lift of an object with no Bernoulli. It's simple vector addition. 1. You are talking about nature's abhorrence of a vacuum. 2. Vacuum abhorrence is not lift. 3. Airplanes do not generate lift as a result of vacuum abhorrence. ---------- Conclusion: you are not talking about how aircraft generate lift. QED. TheSmokingGnu |
#94
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Backwash Causes Lift?
TheSmokingGnu wrote:
Dudley Henriques wrote: Crash Lander wrote: I'd like to see what his thoughts are on String Theory. LOL. I'm sure he'd most likely say that twine was better :-)) What, and discount the obvious implications that Duct Tape has on modern thinking? TheSmokingGnu Ah, duct tape!! Where would aviation be without it ? -- Dudley Henriques |
#95
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Backwash Causes Lift?
On Oct 3, 8:29 pm, wrote:
After all the years of reading this stuff and seeing wind- tunnel demos and graphs and all such, I know there's an awful lot of information out there on the generation of lift. Most of it is available on the 'net. The strangest thing is the newbie who starts to argue with his textbooks, very publicly (as on a newsgroup) without Googling it for himself first. He knows better, he's sure. What's strange is CFI'S (two of them) who did not know how to explain VOR to an electrial engineer (me), who, after reading the discription of how it works, could probably make after reading the technical specs. What's strange is one of the recognized leaders in flight training materials using words like "energy" when they mean "power". I might be a newbie to flying, but I'm not a newbie to physics. -Le Chaud Lapin- |
#96
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Backwash Causes Lift?
On Oct 3, 9:26 pm, TheSmokingGnu
wrote: Le Chaud Lapin wrote: You can have lift of an object with no Bernoulli. It's simple vector addition. 1. You are talking about nature's abhorrence of a vacuum. 2. Vacuum abhorrence is not lift. 3. Airplanes do not generate lift as a result of vacuum abhorrence. ---------- Conclusion: you are not talking about how aircraft generate lift. Yes, I am. It's a combination of many things taking place at once. Vacuum generation by the forward motion of the wing is one of them. QED. -LCL- |
#97
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Backwash Causes Lift?
On Oct 3, 8:38 pm, Tina wrote:
"We" are not in need of getting to the bottom of this. Most of us have been there and done that.This particular writer, if she chooses to analyse physics problems, tends to use the Newtonion approximations as first principles. The good news is my profession doesn't demand those skills often. I would, however, be interested, as I mentioned earlier, how you derive conservation of mV from Newton's force/acceleration relationship. I think you made that claim earlier in this thread. Hmm...I was afraid you would say that. A non-hand-waving explanation would too close to the quantum, and so...it's a bit much to discuss, at least right now. I've posted more messages in this thread in small period of time than I have ever for any other topic, in the history of using USENET, or...as one might say, dN/dt 0, where N is number of messages. -Le Chaud Lapin- |
#98
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Backwash Causes Lift?
Le Chaud Lapin wrote:
Yes, I am. It's a combination of many things taking place at once. Vacuum generation by the forward motion of the wing is one of them. Then why do wings generate lift at negative AOA? Surely the immense vacuum pressures generated would immediately pull any flying craft desperately into the Earth the moment the wing crossed that threshold (say, in a descent). My goodness, it's a good thing you got on here to tell us all this; imagine all those airliners going overhead that have been doing it wrong all this time, actually descending to a destination. They ought very well to know that they could never do such a thing because the vacuum pressures won't allow it! TheSmokingGnu |
#99
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Backwash Causes Lift?
On Oct 3, 9:26 pm, TheSmokingGnu
wrote: Le Chaud Lapin wrote: Yes, I am. It's a combination of many things taking place at once. Vacuum generation by the forward motion of the wing is one of them. And the other is the displacement of air downward. Then why do wings generate lift at negative AOA? Surely the immense vacuum pressures generated would immediately pull any flying craft desperately into the Earth the moment the wing crossed that threshold (say, in a descent). Must be careful not to mix attitude up with angle of attack. The path of the wing's chord line through the air determines AOA. If the airplane is pointed downward a bit so that the chord line is down 2° with respect to the horizon, and the descent path of the airplane is 3°, the AOA is still 1°. An airplane in a steep climb, with its nose up 20°, does not have a 20° AOA. Its flight path is upward at maybe 10° so that its AOA is only 10°. Some wings (thick, heavily cambered wings) will generate lift at up to -4° AOA. The bottom surface of the wing is not the chord line; that's the line between the leading and trailing edges. The bottom surface might be angled downward even more in level flight. the old Champ was a good example: the bottom surface was angled quite visibly down in level cruise flight, but the chord line was still at a positive degree or two. Admittedly there are instructors who don't understand this stuff well at all and think they know more than they do. I'm still learning 34 years after starting to fly. I'm old enough now to realize how little I knew when I thought I knew it all, and to know that I'll now never have a good handle on it all. Too little time and too many other responsibilities. But private pilots need to have the basics, because that's all they have time for and because they'll kill themselves without them. I'm appalled when I see a pilot do a low-and- over and yank back hard for the vertical zoom. They have no idea how close they come to an accelerated stall doing that. Those that manage to get the stall don't live to avoid the same mistake again, and the accident report gives a bland, uninteresting and uninformative "pilot lost control in the climb after the low pass." They don't give the real reason: the pilot did not understand AOA, never did, and thought he was safe because the airplane's speed was well above the stall speed. Dan |
#100
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Backwash Causes Lift?
It's curious. Nobody who's ever stood in the sllipstream of a
rotating propeller on a stationary plane says that a propeller merely sucks an airplane through the sky. But people get into a tizzy if one mentions Newton's third law wrt a wing. Bernoulli and Newton are not alternatives; they are both universally and simultaneously the same thing. It's like those ladder-against-the- wall problems in Statics. The forces don't change, but depending on what you're calculating, sometimes you choose one reference point for your moments, sometimes another. Conservation of Energy: it's not just a good idea, it's the Law. Don |
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