Wing box

[duncan1297]

i just got this random idea.

say you take some type of airfoil and put it in a sealed container like this.

assuming the wing got enough lift would the box float?

[Rune]

Not really. I mean, the wing as an isolated part would feel some lift, but if you consider the whole system, conservation of momentum would tell you something else will feel being pushed against. In a standard airplane, being an open system, that doesn't matter since the air around the plane can take that downwards force without the plane noticing. But in such a closed system, the "box" would end up supporting it, and all you would create is a very complicated way of creating internal forces.

Rune. "For every action, there is an equal an opposite reaction". Some smart dude said that.

[Nibb31]

Of course it won't.

It's like putting a fan on the back of a sail ship to push the sails, or trying to move your car by pushing against the back seat while sitting in the trunk.

Edited June 9, 2013 by Nibb31

[Nibb31]

..........

[MBobrik]

You might as well try to lift yourself in the air by pulling yourself up by your own neck...

[Tex_NL]

Of course it won't.

It's like putting a fan on the back of a sail ship to push the sails, or trying to move your car by pushing against the back seat while sitting in the trunk.

Contrary to popular belief this IS actually possible.

You are however absolutely right about the fact his box won't float and why. But the sail ... that's where you missed the proverbial boat.

[Nibb31]

Contrary to popular belief this IS actually possible.

It's not the sail that's pushing the boat. The boat is being pushed by the wind that is deflected off the sail. It's acting like a thrust reverser on a jet engine. Nothing that contradicts our old pal Newton.

Edited June 9, 2013 by Nibb31

[K^2]

Contrary to popular belief this IS actually possible.

You are however absolutely right about the fact his box won't float and why. But the sail ... that's where you missed the proverbial boat.

I actually did that very experiment way before the MB episode due to an argument on the MB message board.

It's acting like a thrust reverser on a jet engine.

Of course, but the analogy falls flat for that very reason. A closed box is a closed system. Fan on a sailboat is not.

[drakesdoom]

Specifically you would generate a high pressure region under the wing and a low pressure section above it. If your box was really weak the top would cave in and the middle partition would be pushed down into the fan. Most likely you would have just made a white noise machine.

[Acidum]

Interesting...but no.

Open-closed system explanation is already here.

Imagine a situation where You persuade ALL the aeroplanes on Earth to come and fly around same spot on one part of the planet (creating cylinder-like flying group). Will the lift from the wings move entire planet (or its atmosphere) in that direction?

[Kerbface]

Nah, it's just like the "magnet on top of pole attatched to rocket to go to space" thing.

[Cranium]

If it's a closed box, then how is the lift being transferred to the outside? If the wing is fixed in the box then there would be no way for anything to happen, except making some turbulence int he box. If the wing was free floating, it would move around a bit, but it still wouldn't really affect the box in relation to the ground.