Airplanes with flat plate wings

Yes. tip vortexes are bloody awesome. That is why FAA has a ten mile, if I recall correctly, spacing rule for aircraft flying the same path. A plane following closer could stick a wing in one vortex and find himself in trouble in the blink of an eye just as you say. Many years ago I had a friend who flew lite planes into big airports at times. He said this was a real danger during takeoff following a commercial plane. He had some waiting rule which drove the big airports nuts because he would not take off until the vortices had died. His fear was one might drift back over the runway just as he was going down the runway and he would wind up inverted at ground level. I do not know if he was on target or not. I just recall the story he told. Neat story you tell also.

By the way, check the record. I do not think I have once said that there is no such thing as downwash.

Well, I saw no pressures above ambient whatsoever anyplace on the airfoil. I will admit I did not try to measure the pressures immediately on the leading and trailing edges. These are the so called stagnant areas. On a model they are so small it would be bloody hard to measure them. But it does not matter. The stagnant areas can not be causing lift as they are not pushing up (or down). Also what very small push they have is over such a tiny area that force x area = so close to zero as to be not relevant. I did see a small reduction of pressure on the forward third of the underside of the foil thou. And that is just what you should see.

Thanks for all the comments. It is nice to know more then two of us are still on this thread.

Reply to
bm459
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He might have been a bit overcautious. The vortices move outward and downward, and >I think I said I was standing 500 - thats hundred - not 5000 feet below

No, of course not. Air is heavy (the air in a room, at .078 pounds per cubic foot, can easily outweigh the room's occupants) and has terrific damping qualities. If someone blows at you from six feet away, do you feel much breeze on your face? Not feeling downwash at 500 feet doesn't mean it's not there, it just means the effect didn't reach you. As I said earlier, vortices are formed at the wingtips due to the lift/downwash/pressure differences, as well as along the trailing edge. These vortices absorb most of the downwash energy, turning it into heat. It's not the same effect as a wave travelling across water after being generated by a boat, since water is neither compressible nor will similar vortices form in it. Downwash is real and a result of displacement by the wing. Or propeller. Or rotor. Only a balloon doesn't create downwash. Does Bernoulli account for all the thrust generated by a propeller?

Dan

Reply to
Dan_Thomas_nospam

Absolutely correct. I have tried to address this exact topic with another poster but he consistantly refuses to even come close to a statement such as you just made.

As I said earlier, vortices are formed at the wingtips due to the

Well, I can not quite agree with everything you said here. Correct, the air movement behind a wing are not the same as waves in water. Also correct that the turbulance eventually winds up as heat. No other choices are there? However, air is also an incompressible fluid in any unconfined space and being effected by a way subsonic surface such as a model airplane or even a commercial plane during landing. And water forms exactly the same types of votices at the end of a lifting surface or prop as we see in air. They do not persist nearly as long because of the high viscosity of water vs air. They turn into heat a lot faster.

Downwash is real and a result of

Well, it is hard enough to understand a wing, let alone a rotating wing. But just let me say this. Many people think Bernoulli is a weak force that is inconsequencial. Much to small to do anything useful. Yet many years ago I was working with some real highly corrosive materials that also were VERY water sensitive. One common way to work with such stuff is in what is called a vaccum line. A vaccum line is simply a low pressure hunk of glass tubing with a variety of fittings on it so you can put vaporized things you are working with into the line and transfer them. This presumes they are volitile which the things I was working with were. Because of corrosion problems I did not want to use a standard mechanical vacuum pump as my forepump. It would have been tough to keep the volitiles out of the pump and if they got in there they eat the pump up and also wind up in the lab air I was breathing. One of the corrosive was gaseous hydrogen chloride. Trapping it would have been a constant headache as long as I was running the line. So I decided to use a real simple solution. I used one of those $5 plastic Bernoulli aspirators you see in just about every Chem Lab in the world. Although most are metal rather then plastic. They are a pure Bernoulli device that will pull a vaccum down to just about the vapor pressure of the lab water running through them. In my case about

30 mm pressure. So just with Bernoulli I have gone from 760 mm down to 30 mm. That is about a 95% reduction in pressure. Not too bad for a "very weak" effect. But scientists do it every day. Then between the vac line and the aspirator I put first a three stage mercury diffusion pump and a high pressure mercury diffusion pump I built myself. I used to be a half decent glass blower. Mercury diffusion pumps are also pure Bernoulli devices. The high pressure pump would take the pressure from 30 mm down to about 1 mm. And the three stage pump took it from 1 mm down to 10**-6 mm in the actual vac line itself. Thus I removed 99.9999999% of the air from my vac line. Or in pressure terms I made a 15 pounds per square inch vacuum. If an airplane wing could do this it would have a lifting force of 2160 pounds per square foot. So do not tell me Bernoulli is a weak effect. The devil is in the details.

I will say there is a heck of a lot more to a prop then simply blowing air. In fact a prop installed backwards will blow about 90% as much air as it blows if installed frontwards. I know because I measured it on a 9x6 prop at 11,000 rpm both ways. But just try to fly your plane with it on backwards and see how it flys. Actually I was surprised it did this well blowing air when backwards as you give up a ton of angle of incidence with the flat bottom foil used on a prop. Not the result I expected and still I am not sure why it did so well. It must be in part because the air speed was a fair bit below the pitch speed of the prop.

Reply to
bm459

| Doug McLaren wrote: | >

| > No, I haven't. What I have clearly stated is right up there, and I | > didn't trim it out so you can refer to it if desired. | | Well I have refered to it and do not have a real clue as to what you | think other then downwash behind the wing causes lift. So I am going | to try finding out what you think by simply asking yes/no questions.

Allow me to restate my position on the matter (though I did change it a bit to add in the word `wing', so it's more clear) --

I don't believe that a wing can create aerodynamic lift without also creating downwash. (At least without creative definitions of the terms lift or downash.)

You'll notice that I'm saying nothing about vortexes, Bernoulli, the Coanda effect, specific airfoils or anything else in that statement. I'm keeping it simple.

I'm still not quite certain ... do you agree or disagree with my premise? | 1.Do you believe tip vortexes are created somehow by wings? Please | answer yes or no.

I've not really said anything about tip vortexes. But it does look like wings create them, or are at least involved in their creation. Is that your point?

| 2. If tip vortexes are created by wings do you think they cause lift? | Yes means they cause lift. No means they do not cause lift. Please | answer yes or no.

I've never really said anything about what causes lift in this thread, at least not since I made my `I don't believe that aerodynamic lift can exist without downwash' statement.

| 3. Does a model airplane wing compress the air somehow someplace? | Please answer yes or no.

If the model airplane wing is creating lift, it's also creating downwash. Anything else is not something I was discussing.

Aerodynamics of far-subsonic flight is generally based on the the assumption that air isn't compressible (and that therefore the air is not compressed.) This is just an approximation and isn't completely true, but it generally works and gives us reasonably accurate results.

| 4. Is the Conanda effect a direct and demanded result of Newton's | laws? Please answer yes or no.

I've said nothing about the Conanda effect, or the Coanda effect for that matter.

Do I believe that the Coanda effect is real? It seems to be. Do I believe that the Coanda effect obeys Newton's laws? Yes.

Do I believe that Newton's laws require the Coanda effect? I don't think so, but I really haven't given it a lot of thought. Ultimately, the `laws' of aerodynamics are the end result of applying Newton's laws and other similar `fundamental' laws to large numbers of particles, so it wouldn't surprise me if the Coanda effect could be seen as ultimately the result of some application of Newton's laws. I don't see how it's relevant, however.

| 5. If I define efficiency of lift production as follows:

{ `lift divided by drag' was the general definition, which I have no problem with. }

... I don't feel like looking up airfoil data. If you have a point, provide the figures yourself, and use it to come to your point.

| 6. Do you think that the incidence meter you buy at the hobby shop | measures the correct angle of incidence for all airfoils? Please | answer yes or no.

I've never bought an incidence meter. Your question is based on an incorrect premise, and is therefore moot. That, and my fundamental premise doesn't really discuss how a wing creates lift and downwash -- instead, it just says that if you have one, you have the other.

Model airplanes are often grossly overpowered, so eyeballing this stuff often gives very acceptable results. And while I've been flying gliders a lot lately, they're ARFs or kits and so I let the designers worry about the incidence of the wing. They seem to fly well, so I'm happy with them. Perhaps I could tweak out 1.2% better performance by adjusting some things, but I don't care enough to do it.

| 7. If the answer to question 6 is no do you think the meter measures | angle of attack for all airfoils? Please answer yes or no.

Moot. My premise says nothing about angle of attack.

| > If it's 5000 feet up, the weight of the plane is spread out over many | > millions of square feet, and so only a very tiny part of that would be | > pushing on you -- and the atmosphere is pushing up on you too, so you | > won't feel it. | | I think I said I was standing 500 - thats hundred - not 5000 feet below | the plane. If I mistyped I am sorry. I intended to say 500. No | downwash. No movement of leaves.

Right, you did say 500 feet. But even so, the weight of the plane is spread out over what probably amounts to millions of square feet.

Also note that the plane is probably flying 300+ mph -- that's 440 feet per second. It's only approximately 500 feet away for a tiny fraction of a second. One second later, it's 666 feet away (assuming it's flying level, and it was directly overhead.)

If somebody blows a fan on you from across the room for one second, you're not likely to even feel it. If they left it on for many seconds, you might eventually feel it.

A helicopter involves a wing moving through the air, and yet not leaving the scene of the crime if it's hovering. Allow me to give you two yes/no questions --

1) do you believe that a hovering helicopter's blades are are fundamentally just wings/airfoils? (If you think that they somehow follow different aerodynamic rules, please be explicit about how you think they differ.)

2) do you believe that a hovering helicopter creates downwash?

| > Either way, the Earth is ultimately supporting (on the average) the | > entire weight of the plane, both when it's landing and when it's | > flying. | | Yes, I understand the conservation of mass.

It's not so much a matter of conservation of mass, but that the plane is pushing down with certain amount of weight and it has to be supported somehow, or it'll fall down. If the air is supporting it, then something has to be supporting the air, and that would have to be the Earth.

In large amounts, air is very heavy. The weight of a plane, even a

747 or so, is pretty insignificant compared to the air around it to 500 feet or so. The mass that the plane adds to a square of air 1000 feet on each side is a very small percentage of the total mass, so it's not likely to be detected by a human, but I imagine that the right equipment could detect it easily enough.

| > This stuff really isn't on-topic at all. Would you like to move it to | > sci.physics? (I suspect that the regulars there would rip you to | > pieces, but you might enjoy that.) | | You know how to copy the thread to a new news group just as well as I | do. But thinking that physicists are the sole authoritys on fluid | mechanics is a bit of a push.

I'm not saying that at all. I'm saying that it's the most appropriate Usenet group I can find for a discussion of this sort. There aren't any aerodynamics groups that I can find, and there's no rec.aviation.technology group that I can see.

I'll crosspost this post to sci.physics, and I'll set followups to go only there. If you wish to continue this discussion with me on Usenet, let's do it there rather than here.

| 10. In a link provided very kindly by another poster: | |

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| | Please refer to figure 3.2. Do you believe this diagram reasonably | accurately displays the actual air flow patterns around an airfoil.

I'm not so sure about the upwash part, but the downwash part looks good. It's hard to tell from the picture, but I'm assuming that the air well in front of the wing was horizontal.

| I will specify that this diagram is for an airfoil which has an | infinite aspect ratio (which is a detail the author of the web site | probably felt was unneeded detail which would confuse the casual | reader).

If infinite bothers you, just pick a wing that's a mile long. Or ten miles long. Or whatever. As the aspect ratio gets larger and larger, the relative effects of the ends of the wing will have to get smaller and smaller.

| I will also specify that this diagram is for one specific reynolds | number and is not intended to be accurate in every detail for every | single reynolds number(which is also detail the author did not feel | was needed).

He is obviously simplifying things ... probably because he wanted to just write a few pages on it, rather than a book. Seems a reasonable compromise.

| Further I will specify that the airflow past the foil is well under | the speed of sound which I honestly do not recall if the author | addressed in any way.

His overall web site is about general aviation, so assuming speeds well below that of the speed of sound seems appropriate. Usually if somebody is talking about supersonic aerodynamics, or even aerodynamics near the speed of sound, it's usually clear.

| By the way, I have seen the pic of the plane coming out of the clouds | before as I am sure most people on this group have also. All I see is | a very striking picture of tip vortexes.

Yes, it does show the tip vortexes very well. But you'll notice that there's also a `hole' in the cloud where the plane just flew through ... but I can see where it would be convenient to blame that hole on the vortexes rather than on downwash. It seems reasonable that one wouldn't even be able to visually separate the two phenomena on any normal sized wing, at least not in a carefully controlled environment like a wind tunnel. I guess it wasn't a very convincing example -- I can see that.

| Sorry but I see no evidence | of downwash in this picture at all. But it still is a really neat | picture. The pic I am referring to is Figure 5 at the web site: | |

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| | It is going to take me a while to learn what you actually think by | asking yes no questions. But it seems the only way forward.

I've already made my position (at least the one I'm defending in this thread) clear. It seems to me that you're just trying to confuse it with many of your questions, but so be it.

Reply to
Doug McLaren

In general a bunch of very vague stuff that can be interpreted to mean almost anything. I suspect he thinks I may just have him by the short hairs and am about to drag him around the parking lot. Well, I am getting bored so will just cut to the chase.

The problem with claiming lift is caused by downwash is perfectly simple. We have all seen the pictures over and over. All you have to do is look at the smoke streamer pictures of an airfoil in a wind tunnel. I am sure we will all agree that an airfoil in a wind tunnel is producing lift. If you look far ahead of the airfoil ( say 15 chords of the airfoil) you will see the smoke is traveling in a perfectly horizontal fashion. If you look the same distance behind the airfoil it is again traveling in a horizontal fashion. A bit in front of the leading edge you see the smoke streams BELOW the foil bending in an upward direction. Just behind the airfoil that same stream bends down until it is at its entry position. You have not "blown" any air downwards at all. You simply bent the flow up and then bent it back down. The problem with thinking about downwash as causing lift is then you have to admit that upwash caused an exactly equal downwards lift per standard Newton force relationships. F = MA You accelerated a given mass up and accelerated exactly the same mass back down. The wing got nothing out of this deal. Want to refresh your memory go to this link and look at figure 3.7 for a picture of how the air flows:

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The only weakness of this diagram is it only shows the flow for less then one chord in front and behind the airfoil. But I am sure if you think about it you will realize that when you get a little bit farther away both flows will be horizontal in any wind tunnel and at exactly the same altitude for both entry and exit. Well, when a plane flys in the atmosphere far from any other surface it is just as they are in the wind tunnel. That is why an aircraft 500 feet over your head does not produce any detectable downwash. It is not deflecting any air from where you are upwards so it can not send any back down to you.

As I have said before in other threads there is no conflict whatsoever between Newton's laws and Bernoulli. Bernoulli did no more then take Newton's laws and apply them to a moving fluid. His equations are a direct derivation from Newton's laws and are required to be correct by Newton's laws. Anyone who has taken first year undergrad physics better know this. Although I will admit they graduate people from college today who do not seem to know anything much about even their major area so who knows?

What an airfoil actually does is divert air up and at the same time accelerate it a whole bunch. If you look carefully at the cited diagram this acceleration is clearly shown by the smoke dots on the top of the airfoil. The dots are lengthened as the air is moving faster. What is not shown clearly is the air is also accelerated under the airfoil just behind the leading edge. But this acceleration is not nearly as dramatic as that over the top. But both accelerations result directly from work done on the air by the passing airfoil.

Why does the air in front of airfoil know that something is approaching causing it to start moving? That is pretty simple. For all practical purposes every fluid has viscosity. I only know of one exception. Viscosity means a force on any one partical is transmitted in a reduced state to the next partical. In other words air is a little sticky. Due to viscosity the air ahead of the airfoil feels the approach of the airfoil and is pushed out of the way. It is this push that accelerates the moving air. The foil is doing work on the air and the work comes out as faster moving air. The air under the leading part of the airfoil also is moving faster as air needs to flow into the space being vacated by the air diverted from well under the leading edge up and over the top of the wing.

Per Bernoulli, anytime a fluid moves, its lateral pressure (the pressure at right angles to the movement) is reduced. A direct result of Newton's laws. No conflict at all.

It now should be clear that the air on top of the airfoil will exert a lower downward pressure on the foil then stagnant air would exert. Also the air below will exert a tiny bit lower upwards pressure on the bottom of the foil then stagnant air as it also has been accelerated a little. I have long since addressed why you can not get any compression of air at the tiny fraction of the speed of sound at which a model airplane flys. This is usually clearly stated in any text about subsonic flight below speeds of 350 or 400 mph. Even at those speeds the compression effects are so small as to hardly warrent consideration. So there is no place on an airfoil that the pressure can exceed the pressure of the surrounding air if is is not moving relative to the airfoil. Thus lift results from the difference in pressure caused by the accelerated air and the consequence of Bernoulli and nothing else.

Ok it is now a perfectly fair question to ask where in the world does all that tip vortex come from that we all know exists. In any airfoil which has ends to it and is producing lift the air under the end of the foil is at higher pressure then the air on top. So the air tends to flow outwards and upwards to get to the low pressure region. Air will always try to flow towards lower pressure.This air curling up and back winds up with a bunch of angular momentum and just keeps on spinning behind the wing. A vortex turns out to be a pretty stable thing relative to most distubances in air. Watch a smoker blow smoke rings sometime and note how long they will stay intact vs just blowing a puff of smoke out into the air. Another way to think of a tip vortex is as a cylinder of air spinning with a low pressure center. And we know the vortexes off a wing tip must have a low pressure center because they cool down so much water vapor often condenses causing a condenstation trail. The fast moving outside would like to collapse into the low pressure region in the center. But conservation of angular momentum prevents this from happening fast. Watch an ice skater doing spins. They start with their arms outstretched and pull their arms in. As they pull their arms in the spin speeds way up. Again conservation of angular momentum.

Just about inevitably someone in a discussion of lift brings up the Coanda effect. I asked McLaren the question about Coanda because his favorite web site on what causes lift makes it out to be a big deal. Well it is not a big deal at all. But first a word about the language of science. Some things that are basic, like Newton, are called laws. When anything is called an effect it is not a law. It is the result of some underlying law. Coanda simply says that a moving fluid will tend to cling to a solid surface until conditions are reached that induce turbulance. The real question is why does this happen? Well recall that any moving fluid exerts a lower lateral pressure then a nonmoving fluid. On an airfoil next to the top surface you have fast moving air according to Figure 3.2 above. As you go farther from the surface the air is moving slower. This slower air exerts a higher lateral pressure then the faster moving air and thus pushes the faster moving air as far away as it can. As the airfoil is present the fast moving air is trapped. Pure Bernoulli as derived from pure Newton. By the way, all the stuff on McLaren's favorite web site about boundry layers somehow being at the root of Coanda is someones dream stuff.

Lift decreases fast as you go towards the back of the airfoil. How come? Again perfectly simple. That overlying air above the fast moving stream next to the foil is slowly producing drag due to viscous effects as is friction with the airfoil. This causes the air to slow as it passes over the top of the airfoil. As it slows the pressure increases just like any number of actual pressure measurements on foils in wind tunnels have shown. The real fast stuff is towards the front and produces lots of Bernoulli and lots of lift at the front. The slower stuff at the back produces ever decreasing amounts of lift. Net result is center of lift is someplace around 30% of the chord measured from the front.

Does there even have to be any downwash behind the airfoil to cause lift? Well, for practical lift perhaps. However, if you slow the air down more and more you will reach a point at some speed where the foil no longer bends much air in front of the leading edge. Think for a moment about a slow moving foil where only the air above say the 80% point on the chord is pushed up in front of the leading edge and flows over the top. If the foil is at a few degrees angle of incidence the air flowing under the foil behind the 80% point of the chord will be pushed down by the bottom of the foil to the trailing edge. When it hits the trailing edge it must flow UP to get back to its original streamline. But that airfoil is still accelerating air over the top and will still produce lift. Not very bloody much I will be the first to admit. But more then zero. And with an upflow behind the wing instead of a downflow. In fact if you look real close at figure 3.7 you will see something interesting in the bottom illustration. The author happened to chose a flow rate and angle of attack such that the flowline passing just under the foil would just touch the bottom trailing edge of the foil if there were no diversion at all of the airflow. Look at it real close. The author correctly shows this flowline bending up to the bottom of the foil, going to the back and exiting the foil with no up wash or down wash whatsoever.

What if you do not want to believe any of the above? Well we have never passed any laws that say you must believe it or anything else in science. Personally I think computers run mostly on magic and were invented by communist devils. Some smoke also as every time it leaks it's smoke it stops working. About all I can suggest is go to any decent college entry level text book on the theory of lift and spend some time reading. I think Richard Von Mises book that I cited in an earlier post would be a fine starting point. It seems to me if it is good enough for Harvard University as a text book it is good enough for me. Brace yourself for some ugly math thou. Entry level for such courses are usually about junior year I think. Maybe senior.

If someone wants to talk about thrust from a prop and how important blowing air is go ahead and start a new thread. This one started on using flat plates for airfoils. So props is a little off topic. Besides, McLaren still can not understand the clear citations I offered to show that a flat plate is very efficient at creating lift and wants to pull drag into the discussion. I never said a flat plate was any good at all relative to other foils when it comes to drag. The topic was LIFT not DRAG.

Reply to
bm459

The air below bounced it back up, but downwash was created nonetheless. Just as a planing boat shoved water down, which was displaced back up until things were smooth again. The orchard owners who rely on downwash to keep the frost off must be badly mistaken, according to your ideas, as are the small-airplane owners who get nervous around helicopters. Downwash is a product of lift, and Bernoulli. Wind tunnels have their limitations, being so confined, and only the airflow immediately around the foil is of any real interest. The atmosphere isn't a wind tunnel.

Dan

Reply to
Dan_Thomas_nospam

A better look at real-life downwash can be found here:

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Be sure to see the picture at the bottom. The next page:
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how the energy is ultimately dissipated. Not that in both cases the downwash does not contine downward for any great distance, perhaps

50 to 100 feet, before it's damped out. Note, too, that the vortices play a significant role in generating it. Asnd as an earlier reference,
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out, Bernoulli and Newton are not at odds with eash other. Many people make the mistake of insisting only one is true.

Dan

Dan

Reply to
Dan_Thomas_nospam

Hi all I keep trying to visualize wingtip vortices produced by swept-forward wings, and am having a hard time with it. It's easy enough to visualize how standard and swept-back wings produce the vortices from the natural 'spillage' off the wingtip. But with forward sweep, it *seems* like the flow should be vectored more inward toward the wing root, with more 'spillage' occuring at the wing root than off the tip. The result should be less vortex-induced drag. After much Googling, I haven't found this question addressed in any depth. Not being the brightest bulb on the tree, I thought I'd inquire of the greater pool of wisdom found here. Thanks.

Bill(oc)

Reply to
Bill Sheppard

| Doug McLaren wrote: ... | In general a bunch of very vague stuff that can be interpreted to mean | almost anything. I suspect he thinks I may just have him by the short | hairs and am about to drag him around the parking lot.

... more likely is while he was suspecting it before, he's pretty sure now that he's being trolled, and so he'll just let it be after this post.

| The problem with claiming lift is caused by downwash is perfectly | simple.

Of course, I wasn't even directly claiming that. And your post goes downhill from there.

| As I have said before in other threads there is no conflict whatsoever | between Newton's laws and Bernoulli.

Of course not. Which post are you repsonding too? It doesn't appear to be any of mine.

| to show that a flat plate is very efficient at creating lift and wants | to pull drag into the discussion.

Well, I did say `Mostly they're just less efficient than a proper airfoil', where `they' = flat wings. I guess I can understand if your idea of the efficiency of an airfoil is different than mine. And certainly, nobody has denied in this thread that a flat wing can create lift.

| I never said a flat plate was any good at all relative to other | foils when it comes to drag.

Well, Ok. Perhaps we agree more than it seemed, though I'm still not sure what we were arguing about in the first place.

| The topic was LIFT not DRAG.

Actually, the point I made back then was about efficiency, not merely lift (though I hadn't defined what I exactly I meant by efficiency until you had issues with it.) And then you yourself even defined the efficiency of an airfoil as lift divided by drag in a later post in this thread, which seemed reasonable to me ...

Ok, I've been trolled enough ... [past] time to let the thread die.

Reply to
Doug McLaren

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Not much lift for the payload. I wonder if angle of attack has something to do with it and the control surfaces are for stability...

DF

Reply to
Dastardly Fiend

On a sunny day (Tue, 27 Dec 2005 14:19:13 GMT) it happened "Dastardly Fiend" wrote in :

Have you seen these it flight? Thse flap the wings ;-)

Reply to
Jan Panteltje

And then the simple fool wrote even more drivel. In fact I cross posted my explanation of lift to sci.physics just as the fool requested. Now you need to understand the people who reside over there. They make Doc Holliday after a hard days drinking at the Long Branch look as mild as Mother Teresa compared to anything I have ever posted on usenet. Check the record over there. Not a single one of them has had the first negative thing to say about my post on what causes lift in a wing.

As I understand the intellectual rating system current among physicists to goes from best to worst as halfwit, nitwit, pickwit and lowest known is phuchwit. Well, on that scale McLaren is about 200 milliphuchwits. That puts his analytical skills about equal with Alex the African Grey Parrot at the U of Ill.

If this guy really has the science education he claims I can only assume he went to some bible school where heavy duty science was consideration of intellegent design. He has repeatedly posted pure unadalterated nonsense about aerodynamic stuff. He has also posted pure unadalterated nonsense about electronic stuff at times according to friends of mine who actually know electronics and how electronic stuff works.

If all this were not enough he comes back and could have simply said yes you were right all along and I blew it 100%. But his ego is so overblown he has to claim I said things I never said and a simple check of the record proves I never said them. In the absence of the capablitiy to admit he is stupid and incapable of the slightest original thought if he were any kind of decent human he would simply go away and let people with a functioning mind give advice to people who are trying hard to understand some difficult topics.

Sure I have been baiting him for probably the last three years. I have given the idiot leading thought after leading thought on why just perhaps he should reconsider. But you must have a functioning mind to reconsider. I would never do this with anyone who did not claim he was trained as a scientist and forcfully claimed he knew what made something work. The last two people who have commented on this thread have been thoughtful and asked real decent questions. Dan has also gone to the trouble to check and see if perhaps I was giving misleading information on some lift topics and concluded what I said was correct re Newton vs Bernoulli for instance. That is fine and I never will have a problem with such people. As far as I am concerned people like McLaren cause so much misinformation in this world that clear demonstrations like I have done that show they are so stupid they can hardly figure out how to use toilet paper is the only fair outcome. Once in a while it is sufficient to get the morons to go away forever. But at least the rest of the time when they come back it gives a nice clear record of how stupid they really happen to be such that in the future they have no credibiltiy and can be dispatched promptly.

The simple fool denies what he has said over and over and over.

I doubt if you even knew there was no conflict. But you can check any number of back threads. You seem to have no memory at all. Not surprising for someone with such a tiny mind.

It not only can create lift it is very good at creating lift. In fact most models have flat plates that create lift very efficiently. They are called the horizontal and vertical stabalizers. If drag is such a big deal we sure do build our models improperly.

You live in a dream world sonny. I never defined efficiency in any such way. And neither would anyone else. ..

Then why not simply say I was 100% correct in every single thing I said rather then post meaningless generalitys and misquotes like a gutless wonder? Oh yes, also an admission you did not know much of anything about lift or aerodynamic design would have been accurate and appropriate. But rather then behaving as a responsible adult you want to avoid the issue.

Look, I never said this stuff was easy to understand. Most of the readers of this group have little formal training in science and math. I daresay most have never taken a course in calculus. And there is not one single thing wrong with this. We do need diversity in this world to allow it to function decently. But it is easier to understand why time is not a constant in a high gravity field then it is to understand why an airplane wing generates lift. Giving them a lot of misleading crap does not help them at all. It just leads them to believe science is so complicated that science may not even be true and for sure scientists can not be trusted. Then they wind up as protestors against the local nuclear power plant because they have an emotional distrust of all scientists. But I forget, you are not a scientist and know nothing about the topic.

Reply to
bm459

This one flaps its tail feathers.

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And this one has no tail feathers:
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Reply to
Dastardly Fiend

On a sunny day (Tue, 27 Dec 2005 18:06:04 GMT) it happened "Dastardly Fiend" wrote in :

I killed several hundred of those 2 years ago, they fought back, stuck me

4 times too. You should have seen me with that home made protection suit (no they did not get through that) when I attacked their nest. Just emptied the bug spray can into it. There was an interesting 'body language' thing that followed, the hordes that came back to the nest were signalled away by the survivers, then they all moved. Very clever how Creator(tm) put so much navigation and object recognition in such a small space, our best electronics cannot do [it]. Man they were really pissed at me, flying at high speed and then turning and hitting with that feather-less back speer.
Reply to
Jan Panteltje

In article , wrote: | Doug McLaren wrote: ... | And then the simple fool wrote even more drivel.

I'm hardly simple. Fool, maybe. (After all, I'm still posting.)

In any event, you're a nut. Just how many strawmen can you build up and tear down in a single thread? The mind boggles!

| In fact I cross posted my explanation of lift to sci.physics just as | the fool requested.

Actually, I requested that you post only to sci.physics, and set the headers appropriately. You chose not to (which is your prerogative.)

| Not a single one of them has had the first negative thing to say | about my post on what causes lift in a wing.

Clever statement. :) Technically accurate, but ...

| > And then you yourself even defined the efficiency of an airfoil as | > lift divided by drag in a later post in this thread, which seemed | > reasonable to me . | | You live in a dream world sonny. I never defined efficiency in any | such way.

And this is the only reason I'm still posting -- you're right. You did not define efficiency that way -- I misread your statement. Sorry.

| And neither would anyone else.

If you say so. From --

Because lift and drag are both aerodynamic forces, the ratio of lift to drag is an indication of the aerodynamic efficiency of the airplane. Aerodynamicists call the lift to drag ratio the L/D ratio, pronounced "L over D ratio." An airplane has a high L/D ratio if it produces a large amount of lift or a small amount of drag.

But saying `L/D ratio' would certainly be more precise, and I do prefer to be precise.

| > Ok, I've been trolled enough ... [past] time to let the thread die. | | Then why not simply say I was 100% correct in every single thing I said

... as soon as you post something that is 100% correct, and I'm already responding to it, sure. For now, this thread has degenerated into `he said she said' (and not even a good game of that), and it's just a waste of time.

Reply to
Doug McLaren

You should not kill helicopters.

I never do that to bees. I did give a wasp nest a whiff of acetylene to put them to sleep, hoping to transport them to safer location, together with a sniff of oxygen to revive them. Unfortunately the two gases had some sort of chemical reaction and a fire broke out in the nest. Alas, there was little I could do to save them. I felt so bad. How was I to know an oxy-acetylene torch is for cutting steel? DF.

Reply to
Dastardly Fiend

On a sunny day (Tue, 27 Dec 2005 20:24:48 GMT) it happened "Dastardly Fiend" wrote in :

LOL :-)

Reply to
Jan Panteltje

You have real decent intuition Bill. Nice to know at least a few people around this place are capable of independant thought.

The easy way to think about airflow over a wing is to start with an infinitely long, straight wing and then change one thing at a time. In a long wing the air has no choice but to simply flow straight over or under the wing and leave the back at some angle depending on how much air the wing bent up in front. Now if we sweep this infinitely long wing forward what happens? Still no real option but to flow straight over or under the wing. If the wing angled any significant amount of air towards the center it would cause a huge airflow at the fuse and I think we know that does not happen.

Ok, now lets chop off the end of the wing at an angle so that it matches the angle of the fuse and make the wing finite in length. From past analyses and all kinds of actual measurements we know that the fast moving air on top exhibits a lower lateral pressure then the slower moving air on the bottom of the wing. So air will tend to flow off the end, up over the end and curl around towards the top of the wing. But I think common sense thinking also tells you that if you now swept the wing back towards straight this tip vortex would tend to get worse. And it does.

Sweep forward is simply one way of reducing tip vortex and thus induced drag. But swept forward also reduces yaw stability so you need a bigger vertical stab. It also acts as anhedral in upright flight so you need to build in a bit more dihedral to make it however forgiving you wish it to be. And probably worst of all it moves the point of first stall in a wing without built in twist from the tip to the root. Stalling first at the root tends to cause the nose to pitch up with the stall instead of down so recovery can be a bear. For these reasons you do not see any planes with wings severely swept forward to reduce tip vortex and thus induced drag.

Besides there are other ways to reduce the vortex without making all kinds of other problems for yourself. The after market swept up tips on the MD11 and 727 are examples. Some STOL light planes have put flat plates on the end of the wings. The USSR MIGs had air dams built right into the wing.

By the way, there is one application where tip votex is desired. Take a look at the planes used as crop dusters. Things like the Ag Wagon have short stubby big chord wings. ie very low aspect ratios. This maximizes the tip vortex so, if you fly a half wingspan above the crop you are spraying, the tip vortex smashes the spray right down into the crop. This minimizes droplet evaporation and wind drift both of which are critical concerns in the business.

Personally I think your bulb is burning just fine.

Reply to
bm459

To bm459: Thank you sir for the insights on forward sweep. The reason i was curious is because of a little scratchbuilt 30=BD inch span RC plane that flies incredibly well with none of the deficits you mentioned. It has no problem with adverse yaw and no problem with roll stability despite having zero dihedral. Also it is utterly benign in stall, with no tendancy to pitch up or drop a wing. This may be due to the airfoil being semi-symetrical at the root, transitioning to flat-bottom at the tip.. thus moving the point of first stall forward(?). The plane is a real sweety and (almost)daily driver, weather permitting. It goes like stink and slows to land like a thistle. =

Some pics of it are shown here-

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Reply to
Bill Sheppard

I do not doubt you a bit. Just about every type of problem can be designed out of a plane if you know about it ahead of time. Or get lucky and compensate for it by accident. Swept forward does give a neat looking plane to boot.

Reply to
bm459

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