Lift of an airfoil

| The purpose of you doing the experiment is you might learn something. | But I seriously doubt if many on here have the intellectual curiosity | to do a simple experiment and fewer still will have the guts to report | the results if they do the experiment.
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Doug McLaren
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A couple managed to figure out how to privately contact me on my spool of thread experiment. I first saw this experiment over 50 years ago when I took a college course in Aero E. The prof did the demo on the first day. His objective was to get it solidly in our heads that turning air streams is a very complex problem and intuition on what will happen when you turn an air stream is worthless. Yep, you are right. If you follow the directions you can not blow the card off the spool. In fact in that long ago demo the prof also used house air to show that a fair hunk of pressure would not blow the card off the spool. I have no memory what the pressure of house air was. Twenty years ago I replicated the experiment with a spool I made myself that was 2.5 inches diameter and tried it with a air compressor with a gauge on it. I found that a pressure of over 100 psig would not blow the card off my spool. I used a hole diameter in the spool of 1/8th inch. It would be easy enough to design the experiment so that you blew a hole thru the card before you blew it off the spool. Better make the spool out of metal if you want to try that.
To all of you who have seen pics on the net of planes topping a cloud layer claiming to show downwash I can only say I think I have seen most of those pics. I have yet to see a single one that showed downwash. They do show very nicely the results of tip vortexes. Tip vortexes really are awesome big devils.
If you want to think about lift in terms of non Bernoulli ideas simply thinking about downwash is a red herring. Every atom of air that an air foil forces down at some point behind maximum thickness of the airfoil must first be forced up in front of that point. A air foil does not create matter. Nor does it compress air when well subsonic like rc models are. When the air foil forces air up in front of the leading edge it is doing work on that air. This work results in acceleration of the air mass over the top of the wing. Then when it returns to its original streamline. This mass of accelerated air can be viewed from a momentum standpoint as the cause of lift. The math has to do with the momentum vectors at various points of travel of the air over the air foil. If you exam the math carefully this is exactly where Bernoulli comes from. They are exactly the same analysis. They both say the air pressure on the top of the airfoil is lower than the air pressure on the bottom and that this is what causes lift.
It is a shame that not a single person seems to have spotted the error I put in on purpose about air flows over a foil in supersonic flight. I sure hoped at least one person was bright enough to spot that error. Oh well, no luck. And the error is not my statement that in supersonic flight there is always upwash behind the trailing edge. That is fact.
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Sir, Any valid points you may have had on lift I dismissed because of your insults. I'm glad you have a passion for this science but it seems your real passion is for belittling others. I don't think that makes you any more "right". mk ( a fan of Bernoulli)
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