The Physics of Wing Lift...Logic versus tradition.

[Trevor]

I have long been dissatisfied by the currant arguments relating to how aeroplanes fly and often has resulted in heated arguments between boffs or groups with different viewpoints.
I will not mention names or the origin of the theory or step on anyone's toes, but merely state my personal findings and how I came to the logical explanation as opposed to tradition.
The first subject in my next post will be the fallacy of how the vacuum is produced on the top surface of the wing.

[Unbalanced]

http://www.youtube.com/watch?feature=pl ... qBmdZ-BNig

edited to add:

http://www.youtube.com/watch?v=aFO4PBolwFg

Unbalanced: Pilot, instrument land and sea

maker of three airplanes (still alive)

Wings are my thing

[Trevor]

So do you see what I mean?...they still cannot agree!

[Trevor]

Ditto!

[oldNick]

http://www.youtube.com/watch?feature=pl ... qBmdZ-BNig

edited to add:

http://www.youtube.com/watch?v=aFO4PBolwFg

Unbalanced: Pilot, instrument land and sea

maker of three airplanes (still alive)

Wings are my thing

So what shape of wing do you prefer ? and which do you think is the most efficient ?

[Unbalanced]

Oldnick asks

So what shape of wing do you prefer ? and which do you think is the most efficient?

My brother and I have been hammering out aircraft since we were less than ten years old. Fortunately for us, none got lethally high off the ground. All the football pads and helmets in the world wouldn't have saved us.

My preference has changed over the years. My brother and I taught ourselves how to fly in a Rotech Rally 2B kit we built in 1980.


https://www.google.com/search?q=rotec+R ... 38&bih=586

This aircraft had a single surface wing that I thought was the same as the Bleriot 1909 airfoil that he crossed the English Channel on. It was also used in the tricycle version of the Quicksilver MX ultralight.

John Ballantyne (founder and past president of the USUA – United States Ultralight Association) related this anecdote: “I used to laugh out-loud when folks asked about the airfoil shape on the Quicksilver MX. The factory called it the 640X15 airfoil because they bent the ribs over the tire of one of their trucks which had 640X15 tires. It worked great!�

So I don't suppose it was an exact science. This was a great beginner's airfoil because it didn't stall until you got below twenty knots. We never flew if there was the least wind but we saw hundreds of sunrises from several thousand feet up.

Yours is a loaded question in a way. My preference for wing shapes would be the best for the current application. The Cessna 180 wing was my favorite for many years but now that I leave the flying to others, I like whatever gets me there. As they say, any landing you can walk away from is a good one.

I learned that I had dyslexia and would never go on to be a commercial pilot but my brother is flying interisland for Aloha Island Air.

[Trevor]

To respond to both your queries, Oldnick and unbalanced...Yes you are right!..wing shape is important for the task it is best suited.
For the most efficient use of the air flow the shape is chosen according to the load and forward speed of the aircraft.
What I am mainly concerned with is; What is the main reason why even a flat wing glider can fly so beautifully without dropping like a stone.
I respect both your extensive experience in planes and I hope you will allow me to contribute with my viewpoint.

[Fletcher]

For Those Interested.

Much discussion of aerodynamics & the un-unified theories of flight etc in this thread, & the fact that all present theories use the same mathematical expressions of lift & drag forces regardless of the particular theory of flight used.


http://www.besslerwheel.com/forum/viewt ... 8487#98487

[Trevor]

Yes I agree Fletcher, I am not questioning the validity of the formula because once you have a model you can get any equation to work using coefficients or constants.
What I am questioning is the flawed logic that gives rise to fallacies which,if not challenged,eventually become accepted tradition.

[Trevor]

Okay here goes controversy number one.
Most guys who know planes know that the vacuum effect over the wing is caused by the angle of attack on the air mass,and because of its inertial mass it is slow to fill that space the front shoulder of the wing has left,creating reduced pressure.
Now we get another school that insist that the vacuum is created by the venturi effect.
They say that high speed air lowers it's atmospheric pressure on top of the wing and that is what allows a plane to fly.Unfortunately they cannot say why this happens but it just does.
My contention is that they have actually got the proverbial,'Cart before the horse'.
Here's what actually happens.
The angle of attack into the air creates reduced pressure over the wing and the highest vacuum is closest to the surface,being air that has far less mass and under the greatest constraint to flow in the direction of travel.As a result this thin skin of air will expand much faster exponentially in the direction of travel than,the denser layer,...the whole reason for its higher speed.
So in short it is actually the vacuum that creates the high speed air and not the high speed air that creates the vacuum.

[daanopperman]

Hi Trevor ,

At what angle will a wing cease to create reduced pressure over the wing .

[daanopperman]

Trevor ,

You can have a low pressure area without a wing or airfoil shape , remember the Luky Dip , inside was a gadget that resembled a pipe , with a small light ball that you placed on top of the pipe and blow into the pipe , the ball would stick in the airflow because of the low pressure area in the airstream even if you tilted the pipe at an angle .

Take a sheet of paper , hold it at face level , and blow over the paper , the paper will rise due to the low pressure area above , although there is no airfoil involved . If there is no airfoil , there is no angle of attack .

The airfoil is shaped to increase the flow of air over the wing , if you change the angle of attack , you change the position of the airfoil relative to direction of the airflow and increase the velocity of the air flowing over the wing , increasing the lift . To much angle and the airflow will start to create turbalense and the lift diminish . This turbalense cause drag .
Supersonic aircraft will use this turbalense to slow down when coming in to land to reduce airspeed , but they have to use 80 % power or they will stall at a very high speed and loose all control , IOW , they use a little VTO stunt , but to land . The tires is 16 ply , but coming in at 300 km/h they don't last very long ,
On all high lift wings , planes that carry high loads , just behind the leading edge , on top of the wing , they place small defusers to increase the airflow over the wing . It is small deflectors that bunch up the airflow in " streams " of faster moving air , you might call them " venturi's " , or " super chargers " , for they increase the velocity of the air even before the air is at it's highest velocity .
A auto carburetter uses the same venturi principle , but there is no " angle of attack " present , for it is a elegant shaped restriction in a tube that cause increase in velocity of a fluid or gas . Giovanni Battista Venturi discovered the effect , but it was not used for a 100 years .

If it was because of the inertial mass was slow to fill that space left by the front shoulder of the wing , there would be a high pressure area at the wing leading edge , and no flow would occure over the wing . The air would simply bunch up on the wing and nothing would reach the area where the low pressure was to be created .
The venturi effect will " suck " air from below the centerline of the leading edge of the wing that would have passed below the wing , so that there is a constant increase in velocity from front to back of the wing .
Just to show how effective this venturi effect is , can be seen on a tapered wing , where the wing root is longer/broader than the wing tip . The airflow on top of the wing will flow from the wing tip towards the wing root , and at the bottom the air will flow from the wing root to the wing tip . Here the wing can be the same thickness throughout , it is only the shape of the venturi that changed , yet the vacuum formed did not depend on the time it took to fill the space the wing shoulder has left .
There is a thing called a standing wave , that occure on a wing leading edge , pressure waves , but that is only when the wing reaches supersonic speed , and depends on the wing area , for it will form more quicker on a small narrow wing like a tail wing , where the controll surface will cease to function . This was known to the English , but not by the Americans when they started supersonic flight . This standing wave will do what you suggest , it will bunch up the air in front of the wing , both top and bottom , and no low pressure/high pressure can be generated by the wing , all the air will pass in a " arc " over and under the wing . This complete loss of air around the wing made the controll surface useless , as there was no working medium for the controll surface to work on , thus was created the all moving wing , like on the elevators . From the Bell rocket on , the flying tail was developed on like the F86 Saber .
The boundry layer is something that is known for a couple of years , and much investigation is currently going on , I think it was known to the Germans during WW2 . I think they suggested that by removing the boundry layer , there will be no friction or drag and ultra high speeds could be reached , also by submerged submarines , just emagin , a supersonic sub , so fast they can operate from Area 51 .

[terry5732]

Bernouli's principle is pretty much just irrelevent to flight of aircraft

Ever see an airplane with flaps that increase the top curve?

Your flat wing, dime store balsa or paper airplane won't fly?

[Trevor]

Hi Trevor ,

At what angle will a wing cease to create reduced pressure over the wing .

Daanopperman, ...That depends on the wing shape. If you have a flat wing say in a wind tunnel unloaded, supported with no angle of attack,the atmospheric pressure will be equal both sides.

[Trevor]

Bernouli's principle is pretty much just irrelevant to flight of aircraft

Ever see an airplane with flaps that increase the top curve?

Your flat wing, dime store balsa or paper airplane won't fly?

terry5732, ...you are quite entitled to disagree,but have you done a firsthand test.
My flat wing plane with no angle of attack glides perfectly,simply because the downward glide is in fact creating its own angle of attack automatically.