So according to you, an airplane with flat wings will fly just as well with those wings removed, and, on the other hand, paper airplanes cannot fly at all.
Another example of good lift from a flat wing - the keel (centre board/dagger board) of a sailing dinghy. It is lift of this piece of flat ply that gives the dinghy, inter alia, the ability to sail up wind.
Guy
I know lots of people were brought up believing that shape creates lift. It does not. It minimises drag, increases stalling speed and creates necessary volume between the surfaces.
The reason curved wings work better (top side) is that the downward speed of the air steadily increases during the wings passing. The benefit of this is the pressure difference (for the same wing loading) is spread over a larger area and this reduces the stalling speed of the wing giving it a greater wing loading and operating speed range.
To look at the same thing in another way, in a flat wing, once the air is flowing parallel to the surface there is no longer an angle of attack. Therefore all the work is being done at the front and the rest is doing very little. In a curved wing the angle of attack can be kept approximately constant for a period and more of the wing is doing work
Stalling occurs when the air is torn off the top surface of the wing into a massive turbulent flow. The bottom of the wing is a different scenario, however much you increase the stress here it is not going to be pulled off the surface of the wing (on the contrary) and thus there is not the same requirement for a curve on the bottom.
This is very convenient for the designers of wings because a curved top and flat bottom give the wing volume, which is needed for the structural members to carry the load and for other things such as fuel.
The shape of the front part of the wing is primarily to streamline the thick shape so that the air is accelerated as smoothly as possible preventing turbulence and thus drag.
The shape of the rear part is also to minimise drag by reducing turbulence. There are two considerations; the first is that there should be no sudden turning of the air – no vertical back end; the ideal is a razor sharp edge. The second is that, as the edge cannot support a pressure difference (obviously as the air can flow round it), ideally we want the air above and below to be coming together at the same pressure. This implies flat surfaces (curves create angle of attack, angle of attack creates pressure differences) and those flat surfaces should be at zero angle of attack, i.e. parallel to the airflow exiting the wing.
Sorry, have I gone on? My flight has been cancelled, apologies if I am imposing my boredom on everyone else.
Guy
P.S. The reason the dinghy can have a flat keel is that the boat never moves at a significant angle to its centre line and thus the keel is never at risk of stalling.
The rudder, on the other hand, can stall as it can be turned relative to the centre line of the boat. There are some interesting consequences of this.
For example, when sailing on the wind boats are designed so the centre of pressure is behind the keel. This means that the rudder needs to be generating lift in the same direction as the keel to keep the boat straight, known as “weather helm”. (This is a far more stable situation than the reverse, which is very unstable and would make the boat virtually uncontrollable when driven hard on the wind).
Every sailor will recognise the following situation when the boat is being driven hard in a good wind on a close reach. The boat is going really well, maximum speed stuff. And then the helmsman discovers the helm has reached a limit point. If he eases the helm the boat, naturally, bears away from the wind. But, unsettlingly for him, if he hardens on the helm the same thing happens! He can sail the boat straight but there is no way he can make the boat turn, even a fraction, towards the wind.
What has happened is that the rudder has reached its stalling point. The only way the boat can be turned towards the wind (e.g. to tack) is to ease the sails and remove the drive so allowing the angle of attack on both the keel and the rudder to be reduced. Time for a reef.
Sorry everyone, I will go off and pester someone else now!
oops! that should say “decreases stalling speed”.
Double ooops! I got this the wrong way round. The boat cannot bear away. All the helmsman can do is sail straight or luff up. (He can tack, he can’t gybe).
I promise to read my posts before I send them instead of afterwards in future!
Guy
Please don’t. Your response is well said.
A perfectly curved wing creates a stable boundary layer with no internal vortices. A flat wing thus has very limited range of lift by fluid.
A wing lifts by harnessing segment of vortex. A perfectly curved wing therefore follows the rule of vortex (f=ma). Yet, even a flat wing can induce greater force of vortex with flap or slat. Thus a perfect wing changes according to rule of newton.
ItS
Peace
rwj
Aerodave: Now is a good time to revise an answer that will never die in peace.
If you were to respond to the question with your current understanding, what would be your new title?
I might suggest ‘Lift is inverse airmass acceleration as defined by f=ma’ as appropriate understanding and explanation and symbol of lift for higher schooling. Yet how does one convey force so even a child might understand? ‘Wings force air; air forces back?’
What is better title? Guy?
peanutgallery: In reaction: please feel free to suggest following sentences.
How do airplanes fly really?
For every action there is a reaction. Airplanes fly by forcing airmass downward in vortex (the balance of inertia by pressure in fluid).
Really.
ItS
Peace
rwj
And bicycles work by making the Earth spin in the opposite direction.
It is true, but it is not a description of the mechanism by which it happens.
Guy
It is indeed taking so much longer than expected.
Bicycles work by forcing against the massively greater inertia of earth. Mass differential predicts the observation that a bicycle’s action on earth is negligible.
I will grant you that your conjectures are consistent; even if it is with lack of understanding. Yet still I am undecided to conjecture whether this results from willful ignorance or simple blindness.
Please check for me, which way does your clock tick?
Yet predictions from conjecture can easily be tested and observed; no matter the understanding. I propose a simple test to demonstrate once and for all whether your claims hold true.
If you would have us believe that a bicycle can reverse the spin of earth, then it follows that your head can also reverse the spin of hammer.
There should be no difficulty in finding a willing volunteer to spin a hammer against your forehead. Simply please tell us whether you can discern any timeflow or asymmetric or irreversible effects of this action.
If no, I would suggest that inadequate force or vision contributed to the failure. Until you see the light, please feel free to continue the experiment by increasing the inertia of the hammer. I would suggest that if you but hit your heard long or hard enough, the truth might more easily be seen; even if not by you.
Until then, good night guy.
It matters not how hard or fast one might pedal; no bicycle carries the force of energy required to re-verse the vortex that is earth’s spacetime mass. Accept or understand it not, but in our 'verse, spacetime and clocks tick into the future. A bicycle cannot make Earth spin in the opposite direction.
Peace
rwj
Reverse direction = reverse to the bicycle direction obviously!
Guy
Dear Mr Jefferson,
As I received no quick response I offer the following for clarity.
The inertial frame of reference for my bicycle turning the Earth example is the entire Earth viewed from a satellite that is in geostationary orbit before the bicycle starts to accelerate.
You belive that changing the speed of rotation of the Earth has an effect on time. It does not.
You say
yet it is equal in momentum to the acceleration of the bicycle and is thus it cannot be ignored when considering that mechanism. Indeed it is the reverse of negligible, it is the essence of the matter.
When I fall off my stool, really what happens is that the stool no longer keeps the Earth and me apart, I accelerate towards the Earth but also the Earth accelerates towards me. And momentum is conserved.
Can I ask you to explain how momentum is conserved in your model of flight? The air is maintaining the separation of the aircraft and the Earth (just as my stool) but you have additionally a downward change of momentum in the air and I see no momentum change opposing it in your description, surprising considering the Newtonian attribution. I appreciate from your comments that you would not value my explanation of the answer to this but I would value yours.
In answer to your question, the head/hammer example complies with the same laws of physics as the bicycle/Earth however I do not see a tangential force in the former case.
I neither accept it nor understand it. As it overtly specifies no limit on the force to be applied how can the same sentence say the force has a limit? I find the statement to be almost as bizarre as your continued peppering of your text with irrelevant use of the words “vortex”, “spacetime” and so on.
I always try to avoid considering a statement that I do not understand or agree with to me made by someone who is deliberately wrong, as that would create an absolute block on my ability to learn and understand anything new.
The following quotes from you however cause me to ask the question why you direct any comments to me at all? Clearly it is not because you have any interest in my response. I can think of other reasons but suggest that your comments almost certainly have the reverse effect from that which you seek.
Best wishes,
Guy
Please forgive.
Alas, seen even from a geosynchronous orbit, the bicycle still has no virtual effect on earth. The bicycle effect is lost in fluid mass as chaos. Still, I will concede there is much research yet to be resolved on that particular derivative.
I do confess that in my passion for truth, I am much too easily frustrated by those that deny and claim other. Alas, you are consistent as you deny and claim. Please forgive.
Alas and again, relativity has not yet been disproved.
Thus I am inclined to believe that the confusion might lie with the tock of your clock.
Earthmass predicts acceleration of 1G by space and inverse by time. These predictions hold true by observation of heavens and earth. Increasing velocity toward the speed of light slows the flow of time.
In free fall, you and wing are carried by force as gravity toward the center of earthmass. Momentum is conserved with the insignificant force of you and wing on earth.
Yet in earth and stool, the magnitude greater force as solid electromagnetic matter easily holds you and aircraft against force as gravity. Momentum is conserved as you and stool push inverse with equal force.
Yet the electromagnetic force of still air carries not enough viscosity to fully arrest the inertia of you and wing. Displacement of fluid mass conserves momentum as inertia of you and wing are slowed by air.
In wing, the momentum of increasing airmass deflection of airmass is conserved as lift.
Peace
rwj