Planetarion Forums

queball · 22 Sep 2003, 02:18

Check this out:
http://humane.sourceforge.net/publis...da_effect.html

I tried the experiment with bendy bits of paper and that's fine. But I don't quite see how a traditional wing helps a plane fly upside-down, or how a paper plane's wing can produce lift apart from the usual air resistance from having a high angle of attack.

Sketch:

Code:

              smooth change in direction,
              air isn't forced onto the wing
              /
            \/_
 >>>>>>>>>
      oooo>>>
 >>>>>ooooooo>>>>
      >oooooooooo>>>>>>> <- airflow on top
       >ooooooooooooo   <- inverted wing
    /|\  >>>>ooooooooooo
     |      >>>>>>>>>>>>   <- airflow below
abrupt change
in air's direction

Now there might be extra forces from eddys and things but I don't feel I've really grasped the principle here. Surely a wing is simply a machine for changing the direction of the plane as efficiently as it can. How does the Coanda effect make a curved wing more efficient than the linear wing of a paper aeroplane?

guest · 22 Sep 2003, 02:54

Planes flying upside down either dont fly as such, more like fall, or their rear wings can rotate causing lift, ref. f18 hornet

ive never seen a paper plane in my life achieve lift

Structural Integrity · 22 Sep 2003, 07:10

What happens if air flows (or any other substance)?
It affects the air around it, bringing it into motion. It pulls the air around it with it.

For the spoon example, when the water flows next to the spoon, it pulls a certain amount of air with it. According to BERNOULLI, the pressure will decrease because air is removed from the area.

Where you hold the spoon, the lost air will not be replace as fast (the spoon blocking the airflow of the surrounding air that tries to fill the gap) thus between the spoon and the flow of water, there is a lower pressure as on the other side.
The stream is then pulled towards the spoon.

I'm familiar with the Bernoulli principle, but I never heard of the coanda thing. So I might be totally off, but what I said seems quite logical to me.
What do you really want to know? How planes make lift?

MrL_JaKiri · 22 Sep 2003, 08:05

Planes cannot fly upside down with the standard wing shape.

The pilots have to open the flaps to increase the path distance on the previously top side of the wing.

Anyone who says otherwise ISN'T A PILOT and HASN'T ASKED A PILOT

W · 22 Sep 2003, 08:50

Quote:

Originally posted by MrL_JaKiri
Planes cannot fly upside down with the standard wing shape.

The pilots have to open the flaps to increase the path distance on the previously top side of the wing.

Anyone who says otherwise ISN'T A PILOT and HASN'T ASKED A PILOT

True to the last two, but I still say it. Queball is right, "path distance" has little to do with it as opposed to the direction of the path.

Structural Integrity · 22 Sep 2003, 09:18

Quote:

Originally posted by MrL_JaKiri
Planes cannot fly upside down with the standard wing shape.

The pilots have to open the flaps to increase the path distance on the previously top side of the wing.

Anyone who says otherwise ISN'T A PILOT and HASN'T ASKED A PILOT

euh... don't the flaps go down? Don't they increase the pressure on the UNDERSIDE of the wing?

MrL_JaKiri · 22 Sep 2003, 10:08

Quote:

Originally posted by Structural Integrity
euh... don't the flaps go down? Don't they increase the pressure on the UNDERSIDE of the wing?

Ariel Sharons, whatever.

meaple · 22 Sep 2003, 10:10

Ailerons dear <3

Kåre Willoch · 22 Sep 2003, 12:34

Quote:

Originally posted by guest
Planes flying upside down either dont fly as such, more like fall, or their rear wings can rotate causing lift, ref. f18 hornet

ive never seen a paper plane in my life achieve lift

You must have bad paper plane skills, or wouldn't you say that a paper plane going down towards the ground, and then changing direction, flatting out and going up, is achieving lift ? (Just asking in case I misunderstand "lift" here...)

Structural Integrity · 22 Sep 2003, 16:14

Quote:

Originally posted by meaple
Ailerons dear <3

Ailerons control the roll of the aircraft and are located on the outside half of the main wing. Flaps are used to increase lift when the aircraft is flying slow and are located on the inner half of the main wing.
Then we have the elevators in the tail wing that control the pitch, and the rudder in the tail that controls the jaw.

Now, I don't know if they came up with some revolutionary technology that changed this, but I believe this has been like this ever since the invention of these components. Or ofcourse they could have taught me wrong

.

Also, I don't think that an aircraft can fly upside down and maintain its altitude without changing the angle of attack, but I haven't fully read the article in the opening post, so I might be off.

guest · 22 Sep 2003, 16:27

Quote:

Originally posted by Kåre Willoch
You must have bad paper plane skills, or wouldn't you say that a paper plane going down towards the ground, and then changing direction, flatting out and going up, is achieving lift ? (Just asking in case I misunderstand "lift" here...)

id call it wind

the same effect often happens with plastic and paper bag

ref. american beauty plastic bag scene

MrL_JaKiri · 22 Sep 2003, 19:01

After a quick experiment (inside, very little air movement, heating not on so not thermals), I have concluded that paper aeroplanes can produce lift.

Leshy · 22 Sep 2003, 19:13

Quote:

Originally posted by Structural Integrity
I'm familiar with the Bernoulli principle

Which incidentally is not the reason an aircraft can achieve lift.

Structural Integrity · 22 Sep 2003, 19:43

Quote:

Originally posted by Leshy
Which incidentally is not the reason an aircraft can achieve lift.

Explain? Bernoulli said that the difference in air pressure under and above the wing cause lift and that this could be achieved by using a curved suface on the topside and a flat surface on the underside of the wing.
Or am I missing something here?

Leshy · 22 Sep 2003, 19:49

Quote:

Originally posted by Structural Integrity
Explain? Bernoulli said that the difference in air pressure under and above the wing cause lift and that this could be achieved by using a curved suface on the topside and a flat surface on the underside of the wing.
Or am I missing something here?

An airplane wing creates lift because of Newton's 3rd Law.

The curvature of an airplane wing is not designed to create a difference in air pressure. It's designed to push air downwards as it flows across the wing. According to the third law of Newton, for every force, there is an identical force in the opposite direction. At the same time an airplane wing pushes air down, the air also pushes the wing up. Which is the reason an aircraft flies.

MrL_JaKiri · 22 Sep 2003, 19:50

That's exactly the same explanation you know.

W · 22 Sep 2003, 19:52

Quote:

Originally posted by Structural Integrity
Ailerons control the roll of the aircraft and are located on the outside half of the main wing. Flaps are used to increase lift when the aircraft is flying slow and are located on the inner half of the main wing.
Then we have the elevators in the tail wing that control the pitch, and the rudder in the tail that controls the jaw.

Now, I don't know if they came up with some revolutionary technology that changed this, but I believe this has been like this ever since the invention of these components. Or ofcourse they could have taught me wrong .

Also, I don't think that an aircraft can fly upside down and maintain its altitude without changing the angle of attack, but I haven't fully read the article in the opening post, so I might be off.

The fact that you CAN change the angle of attack and still fly even with the convex side of the wing facing mostly downwards was much of the articles point.

Structural Integrity · 22 Sep 2003, 19:59

Quote:

Originally posted by Leshy
An airplane wing creates lift because of Newton's 3rd Law.

The curvature of an airplane wing is not designed to create a difference in air pressure. It's designed to push air downwards as it flows across the wing. According to the third law of Newton, for every force, there is an identical force in the opposite direction. At the same time an airplane wing pushes air down, the air also pushes the wing up. Which is the reason an aircraft flies.

MrL, no it's not the same explanation... he claims the wing pushes air down.

Leshy, I find it a bit hard to grasp, so explain this.
Does it have to do with the COANDA effect? The air following the wings shape closely and when it reaches the end of the wing having a downward motion?

Then still, the air pressure on the topside of the wing is still lower. This should have effect on the lift... no?

I'm open for new ideas here!

Leshy · 22 Sep 2003, 20:00

Quote:

Originally posted by MrL_JaKiri
That's exactly the same explanation you know.

Not entirely, but I can't remember the entire technical explanation in the difference. It was in the Science & Education section of the newspaper a good while ago.

MrL_JaKiri · 22 Sep 2003, 20:01

I changed his argument a bit in my mind because as it stands it says that 'the plane pushes air down and an equal amount of stuff is pushed up' which just leaves it falling at g.

Marilyn Manson · 22 Sep 2003, 20:04

Are Jakiris aerodynamic, and if not, why not?

Leshy · 22 Sep 2003, 20:07

Quote:

Originally posted by Structural Integrity
Leshy, I find it a bit hard to grasp, so explain this.
Does it have to do with the COANDA effect? The air following the wings shape closely and when it reaches the end of the wing having a downward motion?

Yes.

Let me see if I can find the article somewhere.

Structural Integrity · 22 Sep 2003, 20:13

Quote:

Originally posted by Leshy
Yes.

Let me see if I can find the article somewhere.

I don't know... it sounds like you are able to build an airplane with a big air intake and a curved tube to convert the air down.

Leshy · 22 Sep 2003, 20:35

Quote:

Originally posted by Structural Integrity
I don't know... it sounds like you are able to build an airplane with a big air intake and a curved tube to convert the air down.

It's called a Harrier

Structural Integrity · 22 Sep 2003, 20:37

Quote:

Originally posted by Leshy
It's called a Harrier

yeah, but that one has a big engine thrusting down... I mean with natural forces and a good portion of forward motion.

MrL_JaKiri · 22 Sep 2003, 21:16

Quote:

Originally posted by Marilyn Manson
Are Jakiris aerodynamic, and if not, why not?

I fly through the air with the greatest of ease, flitting hither and thither.

JammyJim · 22 Sep 2003, 21:20

erm planes CAN fly upside down?

The wing isnt 'flat' on on the bottom side?

The controls merely reverse? i.e. you move down to go down and up to go up?

MrL_JaKiri · 22 Sep 2003, 21:21

Quote:

Originally posted by JammyJim
erm planes CAN fly upside down?

Someone's never seen the red arrows!