visualisation of the lift distribution over a wing

Alan Baker wrote:

No one understands "suction" to actually mean a pulling force.

Remember folks: no more talk of sucking soda through a straw!
Just suck it up!

... don't pretend that there is a force acting upward on the surface
of the liquid inside the straw...

...because you'll be wrong.


You still don't get it Alan. This level of attention to minutiae is
impressive in Junior High science classes, and paradoxically is quite
correct but trivial. Get over it.

Just so you can savor the general idea - let me phrase the general
concept so it won't trip your OC reaction:
In the general case, two thirds of the lift provided by a wing is due to
the depression over the upper surface - (actually towards the front...)
and a third due to the air flow over the lower surface.

THERE. Are you happy now?

Brian W

On Nov 30, 12:19 am, Alan Baker wrote:

Nope.

I'm making the point that the upper surface contributes absolutely *no*
lifting force.

None.

Zero.

In fact, it provides a downward force. Every time.

Sorry, Alan, old boy, I find must disagree.

Disagree all you want, it won't make the upper surface of the wing
experience anything but a downward force.



In actuality, BOTH surfaces are below ambient pressure.
('splain why?)

Bernoulli.



But without that reduction of the pressure across the top curve of the wing,
the pressure below it can't do much at all, can it?

Which I never disagreed with.

But anyone who thinks the upper surface of the wing is experiencing
anything but a downward force is just sadly misinformed.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

Unfortunately for you, Alan, I have some actual observations of a
fabric-covered wing in flight. My Jodel, being a fabric-covered low-
wing aircraft, has a top surface easily observed during flight. The
fabric actually pulls up between the ribs in flight. It actually does.
And near the trailing edge, it's pushed down just a little between the
ribs. Which agrees perfectly with the distribution of lift on airfoil
diagrams.

And don't give me any baloney about pressure inside the wing bulging
the fabric.If that was the case, it would all bulge, not just the 90%
aft of the leading edge.

http://www.cartage.org.lb/en/themes/...y/Velocity.htm

I have a picture here of a biplane that had a poor fabric job. The
fabric hadn't been tensioned properly during application, and the view
from above of the wing in flight showed the fabric bulging upward
between the ribs quite amazingly. Positive pressure on the top surface
sure isn't going to do that.

There really isn't much substitute for actual observation. Flights of
imagination are usually way out to lunch. We have a few guys of in
homebuiltairplanes.com who are similarly convinced that all the
experts are wrong and have been for 150 years.

Dan

In article ,
brian whatcott wrote:

Alan Baker wrote:

No one understands "suction" to actually mean a pulling force.

Remember folks: no more talk of sucking soda through a straw!
Just suck it up!

... don't pretend that there is a force acting upward on the surface
of the liquid inside the straw...

...because you'll be wrong.


You still don't get it Alan. This level of attention to minutiae is
impressive in Junior High science classes, and paradoxically is quite
correct but trivial. Get over it.

Just so you can savor the general idea - let me phrase the general
concept so it won't trip your OC reaction:
In the general case, two thirds of the lift provided by a wing is due to
the depression over the upper surface - (actually towards the front...)
and a third due to the air flow over the lower surface.

THERE. Are you happy now?

Brian W

I was happy to begin with. Read my initial reply:

"Ummmm...

It sort of depends what you mean.

If you mean that suction is actually providing an upward force, you're
quite mistaken.

If you mean that the difference in pressure between upper and lower
surfaces is 2/3 the result of lower pressure on the upper surface, then
you might be right. I don't know."

You see, I never had any problem sorting out the "minutiae" from the
important. But a whole bunch of people (well, *some* people) jumped in
and certainly made statements that they actually believe the air was
pulling up on the wing.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

In article
,
wrote:

On Nov 30, 12:19 am, Alan Baker wrote:

Nope.

I'm making the point that the upper surface contributes absolutely *no*
lifting force.

None.

Zero.

In fact, it provides a downward force. Every time.

Sorry, Alan, old boy, I find must disagree.

Disagree all you want, it won't make the upper surface of the wing
experience anything but a downward force.



In actuality, BOTH surfaces are below ambient pressure.
('splain why?)

Bernoulli.



But without that reduction of the pressure across the top curve of the
wing,
the pressure below it can't do much at all, can it?

Which I never disagreed with.

But anyone who thinks the upper surface of the wing is experiencing
anything but a downward force is just sadly misinformed.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

Unfortunately for you, Alan, I have some actual observations of a
fabric-covered wing in flight. My Jodel, being a fabric-covered low-
wing aircraft, has a top surface easily observed during flight. The
fabric actually pulls up between the ribs in flight. It actually does.
And near the trailing edge, it's pushed down just a little between the
ribs. Which agrees perfectly with the distribution of lift on airfoil
diagrams.

And it is only deflected upward by the fact that the air *pushing* on
the bottom of the fabric's surface is doing so with greater force than
the air *pushing* down from above.


And don't give me any baloney about pressure inside the wing bulging
the fabric.If that was the case, it would all bulge, not just the 90%
aft of the leading edge.

I would only bulge where the air is at lower pressure than the air
inside the wing.


http://www.cartage.org.lb/en/themes/...cs/FlyingDynam
ics/Aerodynamics/SelectedTopics/Velocity/Velocity/Velocity.htm

I have a picture here of a biplane that had a poor fabric job. The
fabric hadn't been tensioned properly during application, and the view
from above of the wing in flight showed the fabric bulging upward
between the ribs quite amazingly. Positive pressure on the top surface
sure isn't going to do that.

Not on it's own, no. But greater positive pressure on the bottom surface
than on the top surface sure is and does.


There really isn't much substitute for actual observation. Flights of
imagination are usually way out to lunch. We have a few guys of in
homebuiltairplanes.com who are similarly convinced that all the
experts are wrong and have been for 150 years.

Observation can lead you astray: and that is clearly the case here if
you actually think that air can *pull* on a surface.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

In article ,
Alan Baker wrote:

But without that reduction of the pressure across the top curve of the
wing,
the pressure below it can't do much at all, can it?

Which I never disagreed with.

But anyone who thinks the upper surface of the wing is experiencing
anything but a downward force is just sadly misinformed.


Unfortunately for you, Alan, I have some actual observations of a
fabric-covered wing in flight. My Jodel, being a fabric-covered low-
wing aircraft, has a top surface easily observed during flight. The
fabric actually pulls up between the ribs in flight. It actually does.
And near the trailing edge, it's pushed down just a little between the
ribs. Which agrees perfectly with the distribution of lift on airfoil
diagrams.

And it is only deflected upward by the fact that the air *pushing* on
the bottom of the fabric's surface is doing so with greater force than
the air *pushing* down from above.


And don't give me any baloney about pressure inside the wing bulging
the fabric.If that was the case, it would all bulge, not just the 90%
aft of the leading edge.

I would only bulge where the air is at lower pressure than the air
inside the wing.


http://www.cartage.org.lb/en/themes/...mics/FlyingDyn
am
ics/Aerodynamics/SelectedTopics/Velocity/Velocity/Velocity.htm

I have a picture here of a biplane that had a poor fabric job. The
fabric hadn't been tensioned properly during application, and the view
from above of the wing in flight showed the fabric bulging upward
between the ribs quite amazingly. Positive pressure on the top surface
sure isn't going to do that.

Not on it's own, no. But greater positive pressure on the bottom surface
than on the top surface sure is and does.


There really isn't much substitute for actual observation. Flights of
imagination are usually way out to lunch. We have a few guys of in
homebuiltairplanes.com who are similarly convinced that all the
experts are wrong and have been for 150 years.

Observation can lead you astray: and that is clearly the case here if
you actually think that air can *pull* on a surface.

BTW, Brian:

This is precisely why I bother with "minutiae". The PP clearly believes
that the air is actually pulling...

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

Alan Baker wrote:


This is precisely why I bother with "minutiae". The PP clearly believes
that the air is actually pulling...




I'm with Einstein. It's relative. If I'm floating above a wing in
flight and the wing is "climbing" it looks like it's being sucked toward
me. If I'm floating below a wing in flight and the wing is "climbing"
it looks like it's being pushed away from me.

In all reality, as an airplane USER, I don't really care what is really
happening. I know how to manipulate the controls I have to make it do
what I want it to do.

Alan Baker wrote:


Observation can lead you astray: and that is clearly the case here if
you actually think that air can *pull* on a surface.


Why can't air PULL on a surface? Air is made up of molecules.
Molecules have mass. Anything with mass can attract anything else with
mass, can't it?

In article ,
Scott wrote:

Alan Baker wrote:


Observation can lead you astray: and that is clearly the case here if
you actually think that air can *pull* on a surface.


Why can't air PULL on a surface? Air is made up of molecules.
Molecules have mass. Anything with mass can attract anything else with
mass, can't it?

Gravity?

You're not serious.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

On Sat, 28 Nov 2009 19:07:16 -0600, brian whatcott
wrote:

Stealth Pilot wrote:
/snip/ it is the air below pushing
you up that lifts the wing.
Stealth Pilot

In most circumstances, suction on the upper surface contributes about
2/3 rds of the lift, and pressure on the lower surface contributes about
1/3 rd.
That's one reason which rib stitching for rag wings is a biggy.

Brian W

I have never noticed the fabric lifting on my wings, however I have
seen the fuel siphon out of a wing tank due to an improperly applied
fuel cap.

In article ,
Ed wrote:

On Sat, 28 Nov 2009 19:07:16 -0600, brian whatcott
wrote:

Stealth Pilot wrote:
/snip/ it is the air below pushing
you up that lifts the wing.
Stealth Pilot

In most circumstances, suction on the upper surface contributes about
2/3 rds of the lift, and pressure on the lower surface contributes about
1/3 rd.
That's one reason which rib stitching for rag wings is a biggy.

Brian W

I have never noticed the fabric lifting on my wings, however I have
seen the fuel siphon out of a wing tank due to an improperly applied
fuel cap.

And greater pressure in the tank than outside of it...

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg