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Joined: 8/12/2008
Msg: 2
How do airplanes fly?Page 1 of 7    (1, 2, 3, 4, 5, 6, 7)
its called lift... air travles around the object... pushes on the side it comes in contact with, and pulls the side in wich it leaves... look at a sail, pressure on one side and vacume on the other, wings have the same princible... the higher the wind potental, the less of a slope thats needed... until you get a rocket or a jet shape.... horible arinotical desighn, simple all thrust
Joined: 7/5/2009
Msg: 3
How do airplanes fly?
Posted: 12/12/2009 5:59:55 AM
Pixy dust. Everything flies with pixy dust.
 Island home
Joined: 7/5/2009
Msg: 5
How do airplanes fly?
Posted: 12/12/2009 6:33:45 AM
Well that was food for thought plentyofroosters

There may be nothing new under the sun but our understanding

have always had a niggle about my understanding of flight not that I fully understand it now, its just that my understanding is now limited by my ability rather than lack of info.

Would love to see a similar explanation of a boat sail
Joined: 5/6/2009
Msg: 8
view profile
How do airplanes fly?
Posted: 12/12/2009 12:02:27 PM
All objects that fly work under the same basic rules of physics.

The forces applied to an object create a situation where more forces are lifting than pulling down.

The movement of air over an airfoil creates an upwards force greater than the mass of objects like birds, helicopters, airplanes and gliders.
The movement of gases leaving a rocket nozel lifts it by generates a force greater than the forces pulling it down.
Balloons lift by buoyancy, “Any body submerged in a fluid is acted upon by an upward, or buoyant, force equal to the weight of the fluid it displaces” EUREKA! Archimedes.

The artfull application of these forces makes very cool flying things.
 Super Ryan
Joined: 9/15/2007
Msg: 11
How do airplanes fly?
Posted: 12/12/2009 2:02:45 PM

It can't be true because then this plane could not fly:

If you watch the "how to build" video, you will see that the top of the wing does have more surface area because of the wood frame mounted above the tissue skin of the wing. Also tissue is flexible, enough that when the plane is in flight, the tissue flexes upwards causing the top of the wing to have even more surface (the upward curve of the bottom will cause an air pocket, negating the extra surface area to the bottom).

As another poster mentioned, the cause of lift is the Bernoulli effect.
The easiest way to see the Bernoulli effect in action is with a strip of paper.
Step 1. Get a small piece of paper, about 1 in. by 6 in.
Step 2. Place one small edge of the paper against your chin, hold it with your index finger just below your bottom lip, so the strip of paper goes over top of your finger and just hangs down in front of your mouth.
Step 3. Blow.

Now it seems logical that by blowing the paper will be pushed down even further, but that is not what happened (if you followed the directions right).
What should happen is that the paper strip rises to meet the stream of air from your mouth.
This is the Bernoulli effect.
The air pressure under the strip stayed the same, but the air pressure above the strip has changed (due to the higher rate of speed) causing the strip of paper to be pulled up.

Here's a page that also debunks that myth..

Failed to debunk the Bernoulli effect. It only shows that other forces are working as well.

Remember are little paper strip. This proves that you do not need the air from the top of a wing to meet the air from the bottom of the wing to create lift. All you need is lower pressure on the top of the wing. Faster moving air has less pressure than slower moving air.
A good way to think of the effect, think of the wing as stationary and the air is moving over the surfaces of the wing.

I find it kind of funny people are trying to disprove the Bernoulli effect. All modern planes are designed with the knowledge of the Bernoulli effect, and they seem to all fly in the way they were designed to fly.
Joined: 4/19/2007
Msg: 12
view profile
How do airplanes fly?
Posted: 12/12/2009 6:38:34 PM
RE Msg: 6 by Appreciative9809:
The one that says that the air flowing over the curved top of the wing has to go faster, so that it can arrive at the trailing-edge at the same time as the bottom-air, which only has to go in a straight path. For one thing, I've read that it isn't even true that both evern arrive there at the same time anyway.
It doesn't have to. Consider 2 motorcycle gangs, both driving the same types of motorbikes, both at top speed. They both approach a curved bridge, with a road going straight through. One gang member goes over, and the rest of his gang follow him. The other gang go along the road straight through.

The gang going over will naturally have to climb. They can't speed up, because the engines are going at top speed. So they slow down as they are going over the bridge. So the point at which the bridge starts to climb bottlenecks, and then less can go over the bridge at any one moment. So the average pressure on the bridge is less.

The gang going under will just keep going at the same speed. So the same number of bikers will go over at any one moment. So the average pressure on the road remains the same.

The same is true, even if the bridge is just a flat road, angled upwards.

The idea of wind lift generated by a half-moon wing is slightly simplified. But it's the same principle, nonetheless. The amount of air moving past any point on the upper side of the wing is less, and so there is less air to naturally also push down. The faster you move, more air moves past, and the more the difference is increased.

It's the same problem in cars. If the car is rounded on the top, at fast speeds, it starts to lift. If the car is flat above, but angled upwards from the back, then the same thing happens.

RE Msg: 7 by Paul K:
How do sailboats work..... I thought you woujld never ask. Two sails increaase the speed of a sailboat not because of more area, but because of Bernoulli's principle. The main sail is usually smaller than the jib....... the jib is the sail in the front. We are discussing a simple sloop, with one sail from the big stick in the middle, calle d the main mast, and one sail, the jib,attatched to the front of the boat at the bottom by the pointy end, to the top of the main mast at the top of the main mast, and the bottom corner has two ropes, one goes to either side of the boat. When the jib is set, it forces wind past the main sail on the leeward side, at a higher speed than it is going on the windward side of the mainsail, thereby creating a low pressure area that actually pulls the boat forward.

Good explanation.
Joined: 4/19/2007
Msg: 14
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How do airplanes fly?
Posted: 12/12/2009 8:37:38 PM
RE Msg: 13 by quietjohn2:
Try Googling lift by circulation.

I've never encountered a completely convincing scientific explanation of lift.
It's all to do with Brownian motion: Take a glass jar with a glass lid. Put a whole load of pollen grains inside. Then seal the lid. Wait a few minutes. Then if you examine the grains with a microscope, you'll see that they are all bouncing around in a random pattern.

The reason is the laws of thermodynamics.

The Third Law of Thermodynamics says that all particles have to have a positive temperature. But the temperature of a particle is directly related to its kinetic energy, which is a measure of how fast it is moving. So the Third Law also implies that all particles have to keep moving.

The Second Law of Thermodynamics says that in any closed system, the particles will spread that temperature equally. But this can be observed even locally. So in the atmosphere, in any area of air, the temperature spreads around until it is roughly the same for all those particles. They all have the same mass. So the speed of each particle is roughly the same.

So now we have a group of air molecules, all fairly close together, all moving around at the same speeds, generally high speed. They naturally bump into each other. But since they have the same speed and mass, they have the same momentum and the same kinetic energy. The First Law of Thermodynamics says that the energy must be preserved. Newton's Third Law of Motion says that the momentum is preserved as well. So in any one collision, they both enter with the same mass, energy and momentum, and they leave with the same mass. That results in them leaving with the same energy and momentum, which results in both particles leaving with the same speed. But the angle of collision determines the new directions they go in. So these particles change direction every time they collide.

These collisions happen so often, that the end result is that the particles end up knocking each other in all directions. So you have a basic force that happens in all directions simultaneously. That's pressure.

The internal pressure between different parts of air is always going to be dependent on their collisions between each other, which is going to be roughly the same either way. So they cancel each other out.

So we only see pressure when the air collides against something else, "not air", and that's when we see the pressure act on the "not air".

That pressure is a constant barrage of particles, each of which acts like a force, making a constant force. When each particle strikes the body, it loses a little bit of momentum to the body, and the body gains a bit of momentum, making for a little bit of force acting on the body. But we don't notice any change in the the speed of the particle, because it quickly collides with another particle, and then another, and then another, and by the Second Law of Thermodynamics, the slight change gets spread around all the air in the surroundings, and there are so many trillions of particles, that each hit loses only the tiniest fraction of energy overall. Remember, that there are far more than trillions of air particles in a single cubic centimetre, and the loss is spread over several cubic metres of air. So it takes a lot to show even the slightest difference. The almost constant collisions means that there is an almost constant force on the surface area of the body in every direction that the air can hit it, and that's the pressure, force per measure of area, Newtons per cubic centimetre, that is the same for any one second.

That pressure is acting on the body from all directions that the air can assault the body. As long as the body can withstand the general air pressure, then the only effects are the result of pressure differences between one part of the body and another part of the body.

The pressure is proportional to the number of particles hitting the body at any one moment, and the speed at which they are travelling.

The particles hitting the top are hitting it from the left right-wards, from the right left-wards, and from above downwards, but not from the bottom, because the rest of the body is touching the top from the bottom and so that side is not exposed to the air, so the air cannot reach it. The same is true for the bottom of the body. The particles hitting the bottom are hitting it from the left right-wards, from the right left-wards, and from below upwards, but not from the top, because the rest of the body is touching the bottom from the top and so that side is not exposed to the air, so the air cannot reach it. Those forces are equally spread by the particles of the body throughout the body, again by the Second Law of Thermodynamics. So the overall up force is spread all over the body equally, and so is the down force, and so are the leftwards and rightwards forces.

The horizontal forces, pushing left and right, are normally constantly about equal. The vertical forces, pushing up and down, are normally also constantly about equal. So normally, the forces cancel each other out.

In lift, the air pressure on the top acting downwards is lower than on the bottom acting upwards. So there is an almost constant force that is pushing the body down, and an almost constant force that is pushing the body down, but the constant force up is more than the constant force down. So the sum effect of the force acting on the body is upwards.

That can happen either because the air hitting the top downwards slows down for some reason, or the air hitting the bottom upwards speeds up for some reason, or the average number of particles hitting the top downwards in any one second becomes less, or the average number of particles hitting the bottom upwards in any one second becomes more, or any combination.

I hope that helps.
 Super Ryan
Joined: 9/15/2007
Msg: 15
How do airplanes fly?
Posted: 12/12/2009 11:41:39 PM

I've never encountered a completely convincing scientific explanation of lift.

Well, I'm no scientist.

Paper airplanes fly and they don't need curved wings. Simply the angle of attack (orientation of a surface to the airflow) modifies the airflow around around the surface. Even a brick will generate lift if properly oriented, allbeit not enough to fly.

Just like a brick can create lift, but not fly, a flat winged paper airplane doesn't really sustain flight (there are paper airplane designs that do have shaped wings).

Bernoulli is an observation, not a scientific explanation.

It is a scientific explanation of a series of observations.
The Bernoulli principle doesn't just deal with wing shapes. It also applies to Bunsen burners, the Venturi tube on a carburetor, and many other devices that rely on moving fluids (liquids or gases) and pressure.
The Burnoulli principle has been applied to the world of physics and calculus. It is very scientific.
The simpleist explanation I can give is; the Burnoulli principle states that fluids moving at faster speeds will exert less pressure then slower moving like fluids.'s_principle
I know it's wikipedia, but it should give enough of a scientific explanation of the Bernoulli principle.

The general sentiment seems to be that a wing works because it deflect air downwards, thus applying an equal upward force on the wing.

Not really. The shape of a wing causes much more of a pulling up on the wing, then a pushing up on the wing. Read the Burnoulli principle.

If you think about it, a flat sheet placed at an angle to an airflow deflects air downwards.

Yes, making it an alright idea for a kite, but not for an airplane.
The biggest problem with this idea is that simply using a flat wing at a steeper angle will cause huge amounts of drag. Not only will the wing push air downwards, it would also go forward requiring extra energy to push the plane forward, and the vacuume effect on the top of the wing will also pull the wing with a backward force.
With a shaped wing, there is very little drag. The bottom of a wing has very little drag, they are mostly flat with the angle of attack parallel to the planes direction of travel, this causes nearly zero drag or lift. The top of a wing is curved, forcing air to travel faster over the top causing lift as well as drag, but not nearly as much as a flat wing with a steep angle of attack.
It works for a kite becase drag is mostly irrelevent to a kite. Kites are powered by the wind and a stationary point, no matter how much drag, it only comes down to lift over weight.

The Coanda effect describes the tendency for a moving stream of fluid in contact with a curved surface to follow the curvature of the surface rather than continue traveling in a straight line.

Another interesting sail design utilizes the Magnus effect. Jaques Cousteau used it on his sailing vessel, Calypso II. A cylindrical sail oriented vertically rotates and thereby modifies airflow around it to create aerodynamic lift.

Both of these could be called special applications of the Burnoulli principle.
Both deal with moving fluids causing different pressures at different speeds.
But the Burnoulli principle was first published in 1738, long before man had achieved flight, and there is no evidence Burnoulli was even aware how his principle could be applied to flight.
Like most scientific discoveries, the start of a theory is almost never the end. It takes time for all of a subject to be known, and although the world of fluiddynamics has come a long way since Burnoulli's day, there is no reason to discount his discovery or claim it is false, simply because further discoveries have been made on the original theory.
Joined: 4/2/2008
Msg: 16
How do airplanes fly?
Posted: 12/13/2009 2:05:57 AM

Bernoulli is an observation, not a scientific explanation.

If you have any education in either physics or engineering, you'd know what you don't know now.
Joined: 12/6/2009
Msg: 19
How do airplanes fly?
Posted: 12/13/2009 6:58:26 AM
What is the difference between a fluid such as air and room full of ping pong balls that are vibrating so they bounce around like molecules?

Can't we just sum up the forces from the wing colliding with the ping pong balls? I mean molecules?

The wing is deflecting the balls down so the net force is up. Some guy came up with this think about equal and opposite reactions. I think his name was like Newton. Wait, it's Olivia Newton John.
Joined: 7/5/2009
Msg: 20
How do airplanes fly?
Posted: 12/13/2009 9:03:11 AM

If you have any education in either physics or engineering, you'd know what you don't know now.
I do think it is funny. I swear this was in high school physics. I loved my teacher telling us about the different forces by saying things like, if I threw John out the window and Jenny at the same time who would hit the ground first. He gave such great examples. May he rip...or is he floating...hmmm
Joined: 4/19/2007
Msg: 25
view profile
How do airplanes fly?
Posted: 12/13/2009 5:39:45 PM
RE Msg: 24 by Appreciative9809:
It's in the "because" part where you get in trouble:
That can happen either because the air hitting the top downwards slows down for some reason, or the air hitting the bottom upwards speeds up for some reason, or the average number of particles hitting the top downwards in any one second becomes less, or the average number of particles hitting the bottom upwards in any one second becomes more, or any combination.
...But those things haven't happened. The air over the wing is moving faster, not slower. Due to Bernoulli's effect.
I stopped there. But yes, one can go on. Bernoulli's Equation applies to Incompressible Flows. In situations where the density of the air is constant, the air cannot change flow density, and so the number of particles hitting any part of the plane will be constant everywhere. So if pressure is different from one area to another, it must be because of a change in velocity.

Bernoulli points out that the energy is going to be roughly the same for each particle, as the Second Law of Thermodynamics predicts. Bernoulli then points out that since the energy is roughly the same, then as the velocity increases, this increases the kinetic energy, and that will lower the energy available for pressure, lowering the pressure. However, if the velocity striking downwards on the body increases, then the velocity of each particle striking the body is more, making more force, and more pressure. Thus, when Bernoulli says that a greater speed of air makes for lower pressure, he cannot be talking about the downward speed of the particle. Bernoulli is pointing out that there are TWO velocities, the first being the general speed of the particles moving around in a random way, whose square is proportional to the pressure, and an entirely separate velocity, the speed of the velocity as it goes alongside the body. THAT velocity doesn't cause the particle to strike the body at all. If THAT velocity, called "air speed", is higher, then the velocity that causes pressure is lower.

But that's ONLY in incompressible flows, where the number of particles per cubic inch cannot ever change, either more or less, because that eliminates the other factor.

That's why I was careful to state that "because the air hitting the top downwards slows down for some reason, or the air hitting the bottom upwards speeds up for some reason". I wasn't discussing lateral air speed there.

That's also why I was careful to state that "or the average number of particles hitting the top downwards in any one second becomes less, or the average number of particles hitting the bottom upwards in any one second becomes more", as I considered that the flow might be compressible.

The reason you get both flows, is that although the particles are flying in all directions, a substantial number are all moving in the same direction. So when those particles collide with other particles, they pass that momentum onto the second particle, and that generally pushes them forwards overall. The first particle is now knocked into a random direction by the second particle, and so the first particle becomes the random one. So you still have quite a number that are moving in all directions. So you end up with 2 components in the general velocity of the particles, one, the velocity of the air flow, due to the particles that are currently moving in the direction of the air flow, and the other, the general random directions that any particle might move in, due to the particles that are moving in any random direction, that is due to the huge number of collisions due to Brownian Motion.

And, as the wing goes through the air, it doesn't initiallly find less air over it than under it. But, due to the wing's downward curvature, the wing is leaving vacated space behind it, creating a suction in the air, lowering the air's pressure, as some of the force of the atmospheric pressure is used for accelerating that air downward into that newly-vacated space, and therefore isn't available to be exerted on the wing-surface.
Problem is, that if there is less force downwards, you still have gravity pulling you down. You need a physical force pushing you up, to overcome gravity. It's true that you do have a reaction force that acts from the body, that pushes up, in response to the air pressure from above that pushes the body down. But that disappears as soon as the air pressure from above is lowered. So you have gravity pulling you down, and nothing to push you down on top, but still you have gravity pushing you down. So to have a force counteracting gravity requires that there is pressure from below, pushing upwards, and that can ONLY come from particles from below, pushing the body upwards.

That happens because the air particles are flying everywhere in all directions, and so they are ALSO pushing upwards, and those particles that strike the body from below, are striking upwards, and that makes for trillions of tiny little collisions all along the bottom, pushing you up. That is normally countered by the same number and speed of the particles pushing you down from above.

But when the plane's shape is such that the plane makes a space behind it, the air particles at the top just shoot out at the tangent, as al things do naturally, and that simply makes them go horizontally backwards, leaving less particles per cubic inch in the area where the curvature lies, and that means that less particles are there in the first place to strike that part of the surface area of the body from above.

So we have a greater force pushing upwards from above, than the force pushing downwards from below, and thus you have a constant force pushing up.

I realise that's not how they teach it in engineering. But I was taught these things in mathematics, and I was taught by my old maths teacher to always prove things from first principles, so that if I ever made a mistake, or forgot something, I could work out what I was missing or was in error about. So that's how I tend to do things. I tend to start out from first principles and work it out from there.

It means it takes longer for me to learn the basics of a subject. But once I've done that, I know the basics much better. The advanced stuff is only a consequence of the basics. So by knowing the basics very well, the advanced stuff simply flows from there. Makes it much easier to learn the advanced stuff.

Pressure is pounds per square inch, or newtons per square centimeter (not newtons per cubic centimeter)
Fair enough. It's measured over the surface area, because it's measured by the force of the particles striking the body, and they can only strike the surface. So it's a square and not a cubic.
Joined: 11/10/2009
Msg: 27
How do airplanes fly?
Posted: 12/14/2009 6:48:54 AM
Airplanes fly by climbing the air. Their wings act as feet that push down on air. The air gets solid enough to push against when it is pushed on hard and fast enough. It's like if you slip into water slowly the water has time to move away and feels soft, but when you slam into water at a great enough speed the water can't react fast enough to get aside, and feels hard. Air is like water, which we know because both are the color clear, and acts much the same way. The force of gravity pulling a plane down through the air, in the case of a glider, or the force of the engine pushing a plane ahead through air, in the case of powered flight, provides the hardness and speed with which the plane pushes, and the shape of the wing directs that push downward onto the air. If you turn the wings upside down and run the engine backward, that plane would not fly.
 James Bottomtooth III
Joined: 5/19/2008
Msg: 28
How do airplanes fly?
Posted: 12/14/2009 7:09:37 AM

The main sail is usually smaller than the jib....... the jib is the sail in the front.

Around the 1990's sail developers and boat builder realized that a small head sail and larger main was the way to go. That is why you see all grand prix boats with smaller non-overlapping jibs (code 0's excluded) and larger mains.

Moving the power more to the main also gives you more control of the boat, especially downwind as you are not relying mostly on your headsail. Probably why the old MKI -MKII C&C's where called Broach-O-Matics. (very small mainswith large headsails and large masthead kites = wild downwind rides in +20K conditions)

Actually, when a sloop is sailing upwind, just a jib is sufficient. However, since the boat "wants" to rotate around a spot usually just aft of the mast, the rudder must be turned to compensate for this. Rudder angling induces huge amounts of drag in the water, so the mainsail is used to "balance" the boat.

You have it backwards.

To much load on the main will induce a round up and will force the helmsman to use more rudder input.

To much load on the headsail will induce more heel and increase side slip and reduce the sails ability to convert presser into forward momentum due to spill from the exaggerated heel of the boat. Which is why most racing boats now use smaller jibs and larger mains, as it is easier to spill some power off the main with out sacrificing point angle.

That is why you do not adjust the main sheet tension and only drop your traveller and depending on water conditions and the type of rig you have you may also increase back-stay tension, thus spilling power out the back and reducing the load on the helm.
Joined: 1/8/2007
Msg: 30
How do airplanes fly?
Posted: 12/14/2009 9:57:20 AM
I prefer to study nature to find my understandings and not so much a text book.

Like an eagle flying will use blood flow within the wings to create a thermal area under the wing resulting in lift.

Planes heating the fuel within their wings has a similar effect. The shape of the wing is simply used in the ability to trap the bubble of heated air used in lift.

Your example of the little model plane that was able to fly both right side up and upside down was because the tissue paper flexes depending on which direction it was flying in thus still creating that bubble and since it is so light weight that little bit of heat trapped due to the friction of it moving through the air still resulted in it being able to fly in both directions.

jets use a slightly different princliple of flight though they use the wake effect by slicing the air both above and below the air craft like a knife it creates a pinch point as a result of the pressure created both above and below the jet. It can be likened to basically the air acting as a hand that is literally holding the jet within its fingers through use of the smaller wings as the handles for those air fingers to hold onto.

Much greater friction as well as heat both above and below the wing surfaces are the result so basically jets are a slap in the face to normal understanding of flight.

Just my observations and understandings.
Joined: 7/5/2009
Msg: 31
How do airplanes fly?
Posted: 12/14/2009 10:01:53 AM
Interesting information about the sails. I really didn't know any of that. Nice to learn about how the boats fly across the water. Nice actually to learn new things on here.

Last boat I was on was the tall ships. That was way too long ago. (Ferry's don't count.) But I really think the tall ships are still pretty great.

I also still love to watch people hang glide and the birds catching the thermals. I don't know if nature itself will ever stop amazing me.
Joined: 12/6/2009
Msg: 32
How do airplanes fly?
Posted: 12/14/2009 2:13:44 PM
Dreams, you might have your observations wrong.

Airplanes with rigid wings that are flat on the bottom and curved on the top can flight both upside down and right side up. I've done it myself.

Also airplanes with symmetrical wings (curved on both top and bottom), can fly both ways. (I've done this too).

Both the above examples, the wing is rigid and does not change it's shape.

Also, your idea that an eagle's blood creates a mini thermal that it can use for lift sounds fishy. I don't think there are enough calories of heat to do much and even if there were, the wing is always in contact with fresh air.

Eagles do fly off thermals but they don't create them.
Joined: 1/8/2007
Msg: 35
How do airplanes fly?
Posted: 12/14/2009 4:26:48 PM

Dreams, you might have your observations wrong.

ok then try turning your wings upside down and try to take off then.... The reason you can still fly upside down is the pinch point effect i stated talking about the jets.. it is because you are already in the air that you are allowed to fly upside down.

as for wrong about eagles watch them with thermal imaging cameras when they are changing elevations in the air... their wings flex and get hotter.

Yes i know your wings didn't change shape in a full sized airplane but he did not show a video of a full sized ridgid plane he showed a video of a toy plane made of tissue paper and balsa wood and questioned how it was able to fly both right side up and upside down... zoom in on the wing when it inverts in that video and you can see the paper of the wing switches to the other side in curving.
Joined: 1/8/2007
Msg: 37
How do airplanes fly?
Posted: 12/14/2009 4:53:53 PM

Full-size genuine airplanes can fly upside-down without changing their wing-shape

look at the SR-71 My opinion is that is ALMOST perfect.... it just has a few design flaws.

I mean seriously it would have to be desined pretty good to allow 130k ibs of rock to be able to fly as high and as fast as it does.

The troubles i see is with the uprights as well as its landing systems and choice of fuel... pitty there is no way for normal people to talk to the skunkworks team....
Joined: 4/19/2007
Msg: 39
view profile
How do airplanes fly?
Posted: 12/14/2009 4:59:38 PM
RE Msg: 35 by Appreciative9809:
A few first principles first: When the topic is physical science, and when I'm sure that what you've said is incorrect, and that my correction is correct, then I might talk more argumentative-sounding than I would if the topic were metaphysics. If I'm sure that you're mistaken, I might make that clear in my manner.
I get that you are talking from an engineer's POV. I get that you were taught engineering. I'm not disagreeing with what you've been taught.

I also get that from an engineer's POV, what I'm saying sounds crazy. That's because mathematicians first figure things out, then produce theorems, condense them into formulas based on certain ways of looking at things, and then the engineers learn the condensed stuff. From that perspective, when an engineer hears what a mathematician says, he tries to squeeze it into how he's been taught to approach things. But what the mathematician says doesn't even assume what the engineer's been taught. So in order for the engineer to make sense of it, he's got to assume that the mathematician is making dozens of assumptions, just to make sense of it. Then he thinks the mathematician is wrong, because he's still making assumptions, and the mathematician is not.

I've had this happen to me many times. Each time, we argue and argue, and then eventually, the person finally starts to "get it" that I'm not assuming what he's been taught, and then he asks me if I agree with what he's been taught, and then, I say "NO". Then he looks a little shocked.

I then explain that what he's been taught is true only in SOME cases, under some assumptions, but that we don't even need to make those assumptions to figure things out. Then he says "Wow! But is that even possible?" Then I say "Yes." Then I go on to explain my POV, and then the person gets it.

I'd rather not spend 3 pages arguing either. I can see that at this point in your life, you are firm in your views, and that it would take a lot for you to dislodge them, and consider more than one way of looking at things. So I can already see that it's likely for me to need to argue with you at great length, and produce lots and lots of sources for every little logical step, rather than just follow the logic of it. That would take a lot more than 3 pages, and as you put it, it would NOT be fair to everyone else.

Plus, all that would derail the thread.

I've made my point. I've explained it in great detail. That's enough for anyone to understand, if they have a mind to.

FYI, the point of Brownian motion is to show how air works, by taking particles that mimic the actions of air particles in the normal atmosphere, but that are visible with a microscope. That's why I used it to explain how air works.

I suggest you ring up your alma mater, and ask them if that is true. They'll verify it for you. I don't need to, because that's something we covered in maths at mine.
Joined: 12/6/2009
Msg: 42
How do airplanes fly?
Posted: 12/14/2009 6:56:55 PM
Actually many planes could take off with their wings installed upside down. In fact, if it's a plane with a symmetrical wing it would not be much different if you flipped the wing over. That's one of the properties of a symmetrical wing. If you flip it over it's still the same.

I have seen model airplanes with landing gear on the top as well as the bottom. I've also seen models do a touch and go inverted. After touching their fin, they scoot back up into the air. That's the same as taking off by the way. I once saw a bunch of guys flying in the winter and they were taking turns touching the snow upside down with all sorts of planes.

You're quite wrong about that, wings can give lift both inverted as well as upside right. Some airplanes have the wing optimized for flying upside right. But they can still fly upside down.

Aerobatic airplanes have a wing that is symmetrical or nearly symmetrical. That' so they can do manoeuvres better. But the consequence of not specializing the wing to fly upright is that they can't fly as slow.

Here's a video of Pitts Special that happens to have landing gear mounted on the top. It does a landing and a take off. By the way, pretty well every plane you see at that airport could take off upside down if it had landing gear on top assuming the engine could run upside down.

I'd like to see some of those videos that show what you're saying about eagles. Where are they?
Joined: 10/14/2009
Msg: 44
How do airplanes fly?
Posted: 12/15/2009 8:24:10 AM
Joined: 12/6/2009
Msg: 45
How do airplanes fly?
Posted: 12/15/2009 9:46:00 AM

You can learn more about aviation if you try building a few models and test your ideas out. There are lots of simple designs to start with:

Just google "simple model plane" or something.

Joined: 1/8/2007
Msg: 46
How do airplanes fly?
Posted: 12/15/2009 11:09:22 AM


You can learn more about aviation if you try building a few models and test your ideas out. There are lots of simple designs to start with:

I actully do know a bit about it. I just don't have the materials at the moment. My friends father had an old 60's vintage piper cub we would fly in.

I have built model rocets, planes, and once a chopper.

I have made my own wind tunnel using one of those big shop sized high speed fans before... just cobbled together junk basically.

I have used foam that was shaped using hot iron wire cutters and sand paper then dipped it in latex to make it smooth to try a few things in my home made wind tunnel before....

in my cheap wind tunnel made from scraps i have used fishing line attatched to the designs connected to cheap force gauges made from straws filled with water and rubber plungers to be able to observe what the different shapes create for pressures.

I guess what i am saying is yes I understand flight. It may not be the same understanding as you or other people. It just works for me... I am a builder and not so much a mathmatician.

I just get my hands dirty and dig in and build what comes to mind then test and adjust.

Like the other poster said there is more than one way to make a plane fly. learning about flight is not limited to following the rules.... because if you think about it flight itself is not following the rules. that is kinda what sets us apart from all the other creatures on this planet though isn't it? We humans will always try to push the boundries of what is suppose to be possible.

I found it kinda funny how people were talking about boats within this thread because oddly enough water sometimes acts similar to air when at high speeds, so it too can be used as a way to test high speed designs when there is not funding enough to pay for engines capable of the thrust needed to reach those speeds... It is just a bit harder to imagine the ratio's in term of atmoshperes of pressure is all...

Best design so far i have done using both my cheap wind tunel and water was shaped like an "H" with curved angles both lower and above the wings. using landing gear like a hydroplane boat that folds up to allow the plane to lift from the water surface once the speed is fast enough to allow flight.

I am just working on trying to locate the materials to make a full sized or at least a fully functional remote version of some of my designs. ramjet engines are not cheap due to the amount of titainium needed and the refining and forging process needed to make the
Joined: 12/6/2009
Msg: 47
How do airplanes fly?
Posted: 12/15/2009 11:20:26 AM

I didn't get the videos of eagles you mentioned (the ones where the eagles blood heats the wings and then they get lift from the hot air that is in contact with their wings). If you know of any youtube or other video surely you can directly to an article on that.

I'm a bit concerned that there's no support for your theory of eagle flight.

If you'd put landing gear on the top of your piper cub it would be able to take off upside down. Your original statement that an airplane can't take off upside down is still looking rather frail since I gave a video of a Pitts Special doing it.

I'd like to see a picture of your wind tunnel as well. About your comment that an airplane can't fly upside down. Did you measure the pressures around a wing that was upside down with your wind tunnel?

I made one a few years ago. It only measured drag though.
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