Why Airplanes Fly - Voids Above A Planar Sheet

If "Getting on the same page" means learning some of the physics of
flying, I'd enjoy knowing how these 'experiments' are related.

Are you suggesting that a table top under the paper is in any way
representative of what goes on in a dynamic airfoil?

Are you really educated as an engineer?

On Oct 4, 9:13 am, Tina wrote:
If "Getting on the same page" means learning some of the physics of
flying, I'd enjoy knowing how these 'experiments' are related.

Are you suggesting that a table top under the paper is in any way
representative of what goes on in a dynamic airfoil?

Well I was trying to illustrate what goes on between the two sheets of
paper, but I guess a table will do. Technically, if you place one
sheet of paper on top a table, and yank up hard on the paper, there
will be a tendency for the table to lift off the ground, but since the
mass of table is so great, the net pressure upward on table is not
enough to counteract gravity so the table remains at rest (actually,
at a quantum level it does not completely "not move", but for our
purpose we can say that it doesn't).

So I used two sheets of paper because the bottom paper will rise.

So yes, I believe this experiment illustrates an important phenomenon
in aerodynamics. It is not the only phenomenon that plays a role, but
it has one, nevertheless. The decriptions of lift that I read in
flight books seem to ignore it. This weekend I am going to download
material on aerodynamics and read what it says.

There is another experiment that could demonstrate this principle more
dramatically, using an actual airplane wing:

SMOKING CIGARETTES/AIRPLANE WING EXPERIMENT:

I would take an airplane wing, and mount it rails that can move in the
forward and aft directions along what would be the longitudinal axis
of the airplane if if the wing were so attached. Then I would take a
bunch of cigarettes, light them, and hang them up-side-down from a
high ceiling above the wing of the aircraft. The wing would have an
exaggerated AoA, say 30%, no flaps, displaced slightly so that it is
ahead of the hanging cigarettes, but so that the cigarettles cannot
touch. The cigarettes would be lit so that stream of smoke floats
upward.

Then I would use a tremendous force applied to move the wing forward
along the rails, say, by linear induction motor, or whatever, to move
the wing forward, being careful that the apparutus doing so is already
ahead of the wing and connected by steel wire to minimize interference
effects.

You would see that, if the impulse is great enough, not only would the
smoke be diverted from upward and moved in the direction that the wing
went (forward), but the hanging cigarettes themselves would move.

If flat pressure sensors were mounted above the wing, close to the
trailing edge, they would show a momentary decrease in pressure.

If flat pressure sensors were mounted below the wing, close to the
trailing edge, they would show a momentary increase in pressure.

After the force stops, there would be relaxation where the
rarefication above the wing and compression below the wing are
elminiated by flows due to the pressure gradient.

In a real airplane, this is what is happening, but because the the
wing is constantly moving foward, the rarefication above the wingg and
the compression below the wing are never quite normalized by to normal
atmosphere.

The downwash above wing is due to air rushing in to fill the void.

SMOKING CIGARETTE/HARD-COVER BOOK EXPERIMENT:

There is an similar, not-as-dramatic experiment you can do at home
that is closely related to experiment above. Let a piece of stiff
cardboard be your wing. Hold it from the side at an angle of attack,
as above, but don't rest your arm on top of a table. That would
create a boundary condition beneath the wing. Light a cigarette and
inverted so that it is the hot part is near the top of the wing, so
where in middle between leading and trailing edge. Get your arm out of
the way of the void that is about to be created. Now, in one quick
motion, move the cardboard forward. Notice the tremendous net impulse
force that is generated on the cardboard. The smoke will follow.

These things are happening in flight, along with Bernoulli.

Are you really educated as an engineer?

Yes, electrical/software.

-Le Chaud Lapin-

"Le Chaud Lapin" wrote...
On Oct 4, 9:13 am, Tina wrote:
If "Getting on the same page" means learning some of the physics of
flying, I'd enjoy knowing how these 'experiments' are related.

Are you suggesting that a table top under the paper is in any way
representative of what goes on in a dynamic airfoil?

Well I was trying to illustrate what goes on between the two sheets of
paper, but I guess a table will do. Technically, if you place one
sheet of paper on top a table, and yank up hard on the paper, there
will be a tendency for the table to lift off the ground, but since the
mass of table is so great, the net pressure upward on table is not
enough to counteract gravity so the table remains at rest (actually,
at a quantum level it does not completely "not move", but for our
purpose we can say that it doesn't).

So I used two sheets of paper because the bottom paper will rise.

So yes, I believe this experiment illustrates an important phenomenon
in aerodynamics. It is not the only phenomenon that plays a role, but
it has one, nevertheless. The decriptions of lift that I read in
flight books seem to ignore it. This weekend I am going to download
material on aerodynamics and read what it says.

There is another experiment that could demonstrate this principle more
dramatically, using an actual airplane wing:

SMOKING CIGARETTES/AIRPLANE WING EXPERIMENT:

I would take an airplane wing, and mount it rails that can move in the
forward and aft directions along what would be the longitudinal axis
of the airplane if if the wing were so attached. Then I would take a
bunch of cigarettes, light them, and hang them up-side-down from a
high ceiling above the wing of the aircraft. The wing would have an
exaggerated AoA, say 30%, no flaps, displaced slightly so that it is
ahead of the hanging cigarettes, but so that the cigarettles cannot
touch. The cigarettes would be lit so that stream of smoke floats
upward.

Then I would use a tremendous force applied to move the wing forward
along the rails, say, by linear induction motor, or whatever, to move
the wing forward, being careful that the apparutus doing so is already
ahead of the wing and connected by steel wire to minimize interference
effects.

You would see that, if the impulse is great enough, not only would the
smoke be diverted from upward and moved in the direction that the wing
went (forward), but the hanging cigarettes themselves would move.

If flat pressure sensors were mounted above the wing, close to the
trailing edge, they would show a momentary decrease in pressure.

If flat pressure sensors were mounted below the wing, close to the
trailing edge, they would show a momentary increase in pressure.

After the force stops, there would be relaxation where the
rarefication above the wing and compression below the wing are
elminiated by flows due to the pressure gradient.

In a real airplane, this is what is happening, but because the the
wing is constantly moving foward, the rarefication above the wingg and
the compression below the wing are never quite normalized by to normal
atmosphere.

The downwash above wing is due to air rushing in to fill the void.

SMOKING CIGARETTE/HARD-COVER BOOK EXPERIMENT:

There is an similar, not-as-dramatic experiment you can do at home
that is closely related to experiment above. Let a piece of stiff
cardboard be your wing. Hold it from the side at an angle of attack,
as above, but don't rest your arm on top of a table. That would
create a boundary condition beneath the wing. Light a cigarette and
inverted so that it is the hot part is near the top of the wing, so
where in middle between leading and trailing edge. Get your arm out of
the way of the void that is about to be created. Now, in one quick
motion, move the cardboard forward. Notice the tremendous net impulse
force that is generated on the cardboard. The smoke will follow.

These things are happening in flight, along with Bernoulli.

Are you really educated as an engineer?

Yes, electrical/software.

-Le Chaud Lapin-


Are you crazy?! Do you know what cigarettes cost these days??!!

BDS

"Le Chaud Lapin" wrote in message
ps.com...

So yes, I believe this experiment illustrates an important phenomenon
in aerodynamics. It is not the only phenomenon that plays a role, but
it has one, nevertheless. The decriptions of lift that I read in
flight books seem to ignore it.

Subsequently, all the airplanes are falling from the sky.

I recommend building an airplane sometime. The ultimate way to prove your
theory is to be like the Wright Brothers; build it and fly it.

Folks on this forum have logged hundreds of thousands if not millions of
collective hours and all of them have put their asses on the line based on
the aerodynamic principles in books, so you're not going to get much respect
here if you want everybody to do experiments just to discuss to your
otherwise-unproven theories. Some people here have built their own planes,
or engineered airplanes, or maintained them so -their- science is
sufficiently proven. All the discussions and textbooks and usenet theories
in the world aren't worth your first solo flight around the pattern. That
demonstrates that the aerospace engineers proved their wing design and that
the pilots here proved their ability to manipulate that technology. That's
what it takes.

About once a month somebody comes in here and wants to talk about how
aerospace science is all wrong but the thing is, none of 'em ever seems to
have flown an airplane. If you don't do their math for them just the way
they want you to, however, somehow it's all the pilots and plane builders
out here who don't know what they're talking about.

I think your theory would be great put into practice on an experimental
aircraft. I promise you, if you fly it they will come. Best of luck to
you.

-c

On Thu, 4 Oct 2007 14:36:55 -0700, "Gatt"
wrote:


"Le Chaud Lapin" wrote in message
ups.com...

So yes, I believe this experiment illustrates an important phenomenon
in aerodynamics. It is not the only phenomenon that plays a role, but
it has one, nevertheless. The decriptions of lift that I read in
flight books seem to ignore it.

Subsequently, all the airplanes are falling from the sky.

I recommend building an airplane sometime. The ultimate way to prove your
theory is to be like the Wright Brothers; build it and fly it.

Folks on this forum have logged hundreds of thousands if not millions of
collective hours and all of them have put their asses on the line based on
the aerodynamic principles in books, so you're not going to get much respect
here if you want everybody to do experiments just to discuss to your
otherwise-unproven theories. Some people here have built their own planes,
or engineered airplanes, or maintained them so -their- science is
sufficiently proven. All the discussions and textbooks and usenet theories
in the world aren't worth your first solo flight around the pattern. That
demonstrates that the aerospace engineers proved their wing design and that
the pilots here proved their ability to manipulate that technology. That's
what it takes.

About once a month somebody comes in here and wants to talk about how
aerospace science is all wrong but the thing is, none of 'em ever seems to
have flown an airplane. If you don't do their math for them just the way
they want you to, however, somehow it's all the pilots and plane builders
out here who don't know what they're talking about.

I think your theory would be great put into practice on an experimental
aircraft. I promise you, if you fly it they will come. Best of luck to
you.

-c


I will first admit I haven't done the experiments outlined in Lapin's
posts. I will second admit that airplanes do fly. Thirdly I will
admit there are many very good reference books on "why" airplanes fly.
The key word here is "why". The fact that people can design and build
a machine that flies, means they have mastered the elements of design
that allow an aircraft to fly. It doesn't mean they know "why" it
flies. There are accepted theories, disproved theories, questionable
theories and unproven theories, but they are all theories.

Le Chaud Lapin has posted some experiments that in their present form
exhibit some interesting characteristics. Whether or not these
characteristics can be extrapolated to winged aircraft remains to be
seen. Certainly further, much more complex, testing would have to be
done. However, that fact should not provoke the kind of vitriolic
attacks I've seen in this forum. Just because someone posts something
outside the box of conventional thinking is no reason to attack them.
Ron Kelley

On Oct 5, 12:03 am, Ron wrote:
I will first admit I haven't done the experiments outlined in Lapin's
posts. I will second admit that airplanes do fly. Thirdly I will
admit there are many very good reference books on "why" airplanes fly.
The key word here is "why". The fact that people can design and build
a machine that flies, means they have mastered the elements of design
that allow an aircraft to fly. It doesn't mean they know "why" it
flies. There are accepted theories, disproved theories, questionable
theories and unproven theories, but they are all theories.

Le Chaud Lapin has posted some experiments that in their present form
exhibit some interesting characteristics. Whether or not these
characteristics can be extrapolated to winged aircraft remains to be
seen. Certainly further, much more complex, testing would have to be
done. However, that fact should not provoke the kind of vitriolic
attacks I've seen in this forum. Just because someone posts something
outside the box of conventional thinking is no reason to attack them.
Ron Kelley

Thanks Ron.

Given the ratio of ad hominem attacks I have experienced in my first
few days here versus true exploration, I was beginning to wonder if
the 10 people or so who have been responding are representative of
this group, since they do seem to generate the most messages. I saw
your post about 30 seconds after and concluded that perhaps they are
not.

-Le Chaud Lapin-

Le Chaud Lapin wrote:
Given the ratio of ad hominem attacks I have experienced in my first
few days here versus true exploration, I was beginning to wonder if
the 10 people or so who have been responding are representative of
this group, since they do seem to generate the most messages. I saw
your post about 30 seconds after and concluded that perhaps they are
not.

First, I finally found time to read your initial post to this thread. It is
true that all the explanations you've read over the years are not quite
right - that is due to the nature of fluid dynamics. Except for some
trivial examples, the mathematics can't be solved except by numeric
approximation methods. The Bernoulli theorem for example assumes a pre-
existing streamline. It does not actually provide the all-important
streamlines! Otherwise the theorem does take account of all the applicable
conservation laws - but not in a form that can shed much insight into lift
(IMHO).

As to the response you've seen - well, I have some theories but if they are
correct there is nothing I can do, except possibly indirectly. Such as
making this post.

I think for the purposes of piloting that one does not need to know the
Navier-Stokes equations. Because quite honestly the real explanation of
lift is to be found in the differential equations (or integral form)
governing mass continuity, momentum, and energy. All those simple
explanations are just that - simple and obviously incomplete. Rest assured
you're correct in your observations on the inadequate explanations - but
don't make the mistake of assuming a simple _and_ accurate one must exist,
if only you think hard enough on it.

If you are interested in some books on the subject I'd be happy to make
some suggestions.

On Oct 5, 1:11 am, Jim Logajan wrote:
Le Chaud Lapin wrote:
I think for the purposes of piloting that one does not need to know the
Navier-Stokes equations.

That's true.

Because quite honestly the real explanation of
lift is to be found in the differential equations (or integral form)
governing mass continuity, momentum, and energy.

Yes, I agree.

All those simple
explanations are just that - simple and obviously incomplete. Rest assured
you're correct in your observations on the inadequate explanations - but
don't make the mistake of assuming a simple _and_ accurate one must exist,
if only you think hard enough on it.

I never thought that my explanation was complete or accurate. I
offered it because, IMO, it has a sificant influence on airfoil
dynamics. But after reading several books that ignore the partial
vacuum, and one book that was wrongly employing Newton's thereom...
[which is intolerable on any grounds, let alone aerodynamics], I had
to read more.

In his book, "The Proficient Pilot", on page 8, Barry Schiff writes:

"There is, for example, this amusing fable: 'Air flowing above the
wing has a greater distance to travel (because of camber) than air
flowing beneath the wing. Therefore, air above the wing must travel
faster so as to arrive at the wing's trailing edge at the same time as
air flowing underneath. This is pure nonsense."

In his book Learning to Fly With Rod Machado, on page 70, Rod Machado
writes:

"Because air flowing over the wing bends, it is forced to travel a
greater distance than the air flowing underneath. Because it travels a
greater distance, the bent air must move faster on its journey over
the wing. It's this relative increase in wind speed above the wing
that lowers pressure and productes lift."

Since I was new to piloting, I asked a few pilots if they understood
aerodynamics about an airfoil, and they all said yes. The reason they
gave is the one that Rod Machado gave. I asked the older pilots if
they knew who Barry Schiff was, and they said yes. I asked them if
they realized that Barry Schiff did not think that was the reason, and
they said I was mistaken, that Barry Schiff would never be as confused
as I seemed to be about flying. I asked them if they knew who Rod
Machado was. They said yes. I asked them if they thought that Rod
Machado and Barry Schiff would agree. They said yes. I asked them if
they were 100% certain, and they said yes.

Thus began my earnest interest in aerodynamics. I had always been
interested in flying, but this accelerated the interest quite a bit.

I took a sheet of paper and blew over it, the trick that we've all
done, and it went up of course, but I suspected that the reason it
went up was not the reason that was being given by so many people.

I visited a few aero/astro departments online, and while no one is
going to argue with the mathematics of field theory...I did get the
feeling that there were experts in the field saying the opposite
things. So before digging into the math [afterall, there is nothing
wrong with math], I decided to refresh my understanding of Bernoulli's
theorem from my old physics book, and while reading that book, it
occured to me that Barry Schiff's view is more likely right than
not...that is, until I read his explanation of relationship between
Newton and downwash on the next 2 pages of his book. I found a couple
of other books that gave the explanation of downwash that was
similar. Most importantly, I also notice that there was a ***HUGE***
amount of hand-waving going on, far more than one would expect in a
field that has been researched for over a century. I still need to
find a book that I can trust.

I went to the WWW and started reading more aero-astro excerpts, and
concluded that not only is theory still in flux, the experts do not
even agree on the basics. The very basics. Huge amounts of money had
been spent on wind-tunnels. But after all that, I could not get two
experts to agree on the basics. And this was a not simply a matter of
different styles, using integral instead of differential form of
equations, for example, or, deciding where to put a constant, as we
electrical engineers do in our expressions of the Fourier
integrals...there was *fundamental* disgreement about what causes lift
on an airplane.

I asked one of the pilot's again..."How sure are you that the aviation
world understands the basics?" He said he was very sure. He started
rattling off things about NASA.

I begin to imagine airflow over a wing and concluded that pinching at
front of wing must be very important, more important than one would
think, reading the explanations. I also concluded that a glider
should have wings that are very long but with a short cord, which aslo
turned out to be true. I then revisited my physics book...and it
_appeared_ that the application of Bernoulli to flying is wrong in
many contexts, but I decided to not discuss that just yet because it
would be too controversial.

I ask one of the pilots if he thought rarefication had anything to do
with it. He said, "No, it's all Bernoulli." I asked him what would
happen if I did the paper experiment, the one mentioned in my OP, and
he did not know, but said it does not matter because a piece of paper
is not a wing and it does not fly through the air. I asked him if he
understood why the paper would move, and he said, again, it does not
matter. I asked him if he saw any relation between my paper experiment
and the movement of a airfoil, and he said, finally, no, there is
none, because it is all Bernoulli.

I asked a CFI one last time, and he too said it was all Bernoulli,
precisely the argument that Barry Schiff refutes in his book.

So I started imagining, with no mathematics, what goes on with fluids
around surfaces, which lead me to these various experiments.

If you are interested in some books on the subject I'd be happy to make
some suggestions.

Sure.

-Le Chaud Lapin-

Le Chaud Lapin wrote in news:1191561472.221396.70520
@w3g2000hsg.googlegroups.com:

On Oct 5, 12:03 am, Ron wrote:
I will first admit I haven't done the experiments outlined in Lapin's
posts. I will second admit that airplanes do fly. Thirdly I will
admit there are many very good reference books on "why" airplanes fly.
The key word here is "why". The fact that people can design and build
a machine that flies, means they have mastered the elements of design
that allow an aircraft to fly. It doesn't mean they know "why" it
flies. There are accepted theories, disproved theories, questionable
theories and unproven theories, but they are all theories.

Le Chaud Lapin has posted some experiments that in their present form
exhibit some interesting characteristics. Whether or not these
characteristics can be extrapolated to winged aircraft remains to be
seen. Certainly further, much more complex, testing would have to be
done. However, that fact should not provoke the kind of vitriolic
attacks I've seen in this forum. Just because someone posts something
outside the box of conventional thinking is no reason to attack them.
Ron Kelley

Thanks Ron.

Given the ratio of ad hominem attacks I have experienced in my first
few days here versus true exploration, I was beginning to wonder if
the 10 people or so who have been responding are representative of
this group, since they do seem to generate the most messages. I saw
your post about 30 seconds after and concluded that perhaps they are
not.

Except we both know that isn't what you are doing.


Bertie

Le Chaud Lapin writes:

Given the ratio of ad hominem attacks I have experienced in my first
few days here versus true exploration, I was beginning to wonder if
the 10 people or so who have been responding are representative of
this group, since they do seem to generate the most messages.

Those who engage rapidly in personal attacks are the most active posters, but
are not necessarily representative. Personal attacks are very easy to
construct and thus can be launched very quickly. Rational argument or debate
is much more difficult.