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right or wrong????

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Lrjtcaptain

Well-known member
Joined
Oct 28, 2002
Posts
927
Alrighty,
I'm down at the FAA academy and had an argument with another student today about lift.

Here it goes.
We have one of those balsa wood airplanes with the rubber band and little propeller.

Anyways, he insists that the flat wing of that little plane produces lift. I know it doesnt because it has absolutly no practical airfoil. The wing is flat and symetrical.

Anyways, he said not to argue cause he has an enginering degree....evidently my aerosci degree from riddle means nothing to him.

How can i prove that **CENSORED****CENSORED****CENSORED****CENSORED** thing doesn't produce lift. I should let it go but he kept insisting and making the comment that its okay that he knew i was wrong. little things that piss me off.
 
little wood planes

That wing has no camber to it therefore Bernoulli's Principle does not apply (no high & low pressure differential). Remember that in a normal little airplane, impact air pressure accounts for 10-15% of a lifting force generally speaking. It's my opinion that they've kept it light enough to be supported in flight by such.

I'm guessing they've got a slight angle of attack built into the wing placement.
 
I know there is no high low in effect here, but he claims that since when your throw it downward, since it initally starts a climb that it generating lift.

so i told him if that is the case, then rocks float cause you can skip them accross water
 
He's right.

There are two types of lift: dynamic and induced.

Dynamic lift is the whole Bernoulli (sp?) thing..airfoils, low pressure above the wing, etc.

Induced lift is what happens when the slipstream strikes the bottom of the wing (or any other part of the airplane, for that matter) and forces it upward. If you stick a flat board out the window of your car on the highway and "feather" it, you get no lift, But as soon as you tilt the leading edge of the board upward, it rises.

So yeah, the flat balsa wood of one of those toys produces lift. Not very efficiently, but it works.
 
Lrjtcaptain said:
...evidently my aerosci degree from riddle means nothing to him.
Nor anybody else.

Keep your shirt on...I'm just kidding! :D
 
Hence, put enough horsepower on a barn door, it will fly.

Or, you build it light enough, and with a little horse power, an follow the rules, physics will win.

There has been competitions in the past with radio controlled airplanes that test these ideas.
 
Re: Re: right or wrong????

Typhoon1244 said:
Nor anybody else.

ROTFLMAO!
 
Lrjtcaptain said:
Anyways, he said not to argue cause he has an enginering degree....evidently my aerosci degree from riddle means nothing to him.

How can i prove that **CENSORED****CENSORED****CENSORED****CENSORED** thing doesn't produce lift. I should let it go but he kept insisting and making the comment that its okay that he knew i was wrong. little things that piss me off.

ERAU Aero Sci degree does not make a rocket scientist. I know I have one. You better get used to being pissed off. A barn door will generate lift if held in a relative wind at the right angle. Ever seen the wing on an F-5, F-104, etc?
 
There are some wings that are symmetric (same shape top and bottom) that produce no lift at a 0 angle of attack, but once you tilt them you are off to the races. I want to say the Spitfire in WW2 had a wing like that (or was that an elliptical wing, or both? it has been a while). I searched around and can't really determine what kind of wing the Spitfure had but it seems like many of the aerobatic planes have symmetric wings, which makes sense. Seems like it would be easier to fly upside down if you didn't have all the curve Bernoulli stuff pushing towards cumulous granite and just had to maintain a slight up nose attitude (I guess down nose from the view of the upside down pilot though) to maintain altitude even though you're inverted, like Maverick of course.

I think that your friend was right though, even a flat board will produce lift if you give it AOA and airspeed.
 
firstthird said:
There are some wings that are symmetric (same shape top and bottom) that produce no lift at a 0 angle of attack, but once you tilt them you are off to the races.
The F-104 was like that. In fact, it's wing cross-section looked like a flattened diamond. Very weird.

It certainly flew, though!
 
Yey it flew with a dern Saturn V rocket engine stuffed inside it.
Those planes are smaller than I imagined them.
 
Was Lrjtcaptain the guy who bitched out that pilot for not being in proper uniform a while back??? I wondered where he went off to.
 
The F-104 used to have guards installed on the leading edge of their wing when they were worked on. It seems the dog gone thing was so sharp, and just the right height that guys were cracking their heads on it. And yes it was symmetrical.

There is another principle that typhoon alluded to and that is the kite principle. Without a high pressure area underneath the wing, there is no way modern fighters can generate the G forces they do just by Bernoulli's principle. If you take the weight of an aircraft and divide that by the square inches of the wing you can find the loading in psi. Times that by 9-15 (the structural limit is 1.5 times the G limit) (we had an F-4 put 13 G's on it at Homestead in the early eighties; the only thing that amazed McDonald was that the airplane was in one piece) and you'll find it exceeds a perfect vacuum needed on the top surface with only 14.7 psi on the lower surface.

I used to do this with rudder and stick inputs where I could "flat plate" the airplane and abruptly change direction. But I'm older now and a whole lot less bold, besides, it would spill the coffee.
 
If the wing wasn't producing lift, what was?
 
Of course the wing is producing lift. Don't be stupid.

A wing doesn't have angle of attack built into it. It is mounted with angle of incidence. Angle of attack is strictly a relationship between the relative wind (local airstream) and the aerodynamic chordline of the airfoil.

Forget Bernoulli. Consider AoA.

The amount of lift produced by "Bernoulli's Principle" is very minor; roughly akin on most light aircraft to the same force exerted by a baby sucking on a bottle. It accounts for only a small portion of the total lift vector.

Measure the downwash, understand the lift, and see it as angle of attack.

The wing needs NO camber to produce lift. Only angle of attack. Throwing degrees and accolades about won't change that.
 
No Bernoulli-Only Newton

Check out this article on the web. According to it, Bernoulli's Principle has absolutely nothing to do with lift. It says Newton's third law accounts for 100% of the lift on a wing. Make sure you read the whole article (fairly short) not just the first part of it.

http://www.textbookleague.org/105wing.htm

I read somewhere that if it weren't for Newton's third law, and a wing only used Bernoulli's principle, a Cessna 152 would have to go 400 knots to lift off the ground! Maybe it's Newton-90% of lift, and Bernoulli-10% of lift?
 
That article poses no evidence for either side of the argument. However, it does do a great job slandering Bernoulli.

Stated in the article:

Third -- and this is the most serious -- the common textbook explanation, and the diagrams that accompany it, describe a force on the wing with no net disturbance to the airstream. This constitutes a violation of Newton's third law.

That doesn't seem to me to be true. There is a downward force that is produced. On a cambered wing, the average realtive wind created creates a downward force. Basically, a curve upward from the leading edge flowing over the wind and then finally curving downward off the trailing edge. Which does not violate Newton's 3rd law of motion.
 
Re: No Bernoulli-Only Newton

liv'n_on_credit said:
Check out this article on the web. According to it, Bernoulli's Principle has absolutely nothing to do with lift. It says Newton's third law accounts for 100% of the lift on a wing.


Exactly. The Conservation of Momentum, Law of Coanda, and Newton's Third Law of Motion convincingly debunk the time-honored Bernoulli Theory of Lift that has been perpetrated on the aviation community for ions. With respect to the Principle of Equidistant Transit Time, which is the foundation of Bernoulli's Theory, how could a symmetrical airfoil develop lift? Well, based on Bernoulli, it couldn't because both distances for that parcel of air would travel the same distance.

Bernoulli would have you believe that the increase in speed causes the decrease in pressure. But, as has been proven many times over via the Law of Coanda and Mr. Newton's 3rd Law, it's the decrease in pressure that causes the incease in the speed of the air.
 
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