Air foil shapes and wings

The artical says that an air foil shape, flat on the bottom curves on top produces a lot of life. This type of air foil is not good for inverted flight. Lift is down instead of up when flying inverted.

Cemetrical air foil shapes produce the exact same amount of lift on both sides of the wing there for this shape is excellent for stunt and combat flying.

The theory that the inboard wing should be longer than the outboard wing for cemetrical air foil shapes because the outboard wing is traveling faster and producing more lift is non since because no matter what speed the wing is traveling it never produces any more lift. All it has to do is over come gravity.

The artical goes on to talk about other things like thicker ribs makes a wing turn better, thinner ribs produces less drag, longer ribs, shorter ribs, longer wings, etc.

This got me to thinking. Many of the 1/2a airplanes have flat solid balse wings. I have never seen a large airplane like 52" wing span with a flat solid balsa wing like 1/2a type airplanes. It seems to me a flat wing would have very LOW drag and an airplane that would normally need a 40 size engine to fly would fly good on a .15 size engine. It seems to me a flat 52" wing would fly slow with no problem, probably fly great at about the same speed or a bit faster that 1/2a airplane 35 to 40 mph. One thing would effect another so flying this slow would reduce line tension and might be hard to fly in 60 ft lines unless the lead outs were set back, way back to create more line tension.

Symmetrical. And symmetrical wings predate the existence of the combat event.

>The artical says that an air foil shape, flat on the bottom
>curves on top produces a lot of life. This type of air foil
>is not good for inverted flight. Lift is down instead of up
>when flying inverted.
>
>Cemetrical air foil shapes produce the exact same amount of
>lift on both sides of the wing there for this shape is
>excellent for stunt and combat flying.

As demonstrated by Davey Slagle in the mid-late 40's.

>The theory that the inboard wing should be longer than the
>outboard wing for cemetrical air foil shapes because the
>outboard wing is traveling faster and producing more lift is
>non since because no matter what speed the wing is traveling
>it never produces any more lift.

Not correct at all.

>All it has to do is over
>come gravity.

Not correct unless all you do is fly straight and level.

<snip rest of post>>

Wow.

There are many opinions dealing with airfoils right down to whether lift is produced by Bernulli's law or by what I call deflection which is actually the pressure pruduced on the bottom surface of a wing because of the angle of attack. I believe that the answer lies somewhere in between and you can see that in a symmetrical airfoil. From your definition a symmetrical airfoil can produce the same amount of lift on both sides. If there where no angle of attack then a symmetrical airfoil would cancel itself and gravity would keep it from flying. However, a slight raising of the leading edge causes a bias in the airflow slowing (theoretically) the air across the lower camber and accelerating (theoretically) the airflow across the upper camber. Bernulli's law states that as velocity increases pressure decreases. So, the faster flow over the top lowers the pressure on the top and the slower flow raises the pressure over the bottom thereby producing our freind, lift. The action seems to bear out the theory but then there is the board wings that also fly. It could be argued that the same thing happens to the flat wing with increased and decreased velocities creating differencial pressure between the upper and lower surfaces of the wing. However it could also be argued that the flat surfaces only react on the lower surface since it is presented to the relative airstream.

Do you see where I'm going? I don't have a solid position on this, I see merit to both veins of thought. That's why its impossible to make these discussions conclusive. I am a Free Flighter normally and we use some very radically different airfoils with deep undercambers and thin sections to creat high lift at low speeds. Yet, some of the most successful free flight models ever designed used simple flat bottom airfoils, in fact most gas models use them while rubber powered and towline glides use undercambered foils.

What we can do is simply apply what we know works without the arguement of theory. A wing produces lift, why isn't important. We learn how to improve the lift and how to control it for our particular activity.

I, like you, find it all fascinating and have for all my life. I'm no aerodynamicist but have learned by experience over the years what I can make work and what doesn't work for me. That's not to say others can't make it work, maybe I use a different approach. I guess what I'm saying is that you'll get all kinds of opinion on this subject since to this day it still isn't fully understood. Yet even though that's true, we've learned what it takes to get extreme performance from our aircraft, and believe me, stunt is on the extreme end.

If you take that same sheet of flat cardboard 4 feet square and hold it out in front of you and let go it falls like a parachute. Is it flying?

Do the same experement again with a wing shape flat sheet of cardboard 12" by 48". You can't run fast enough to keep it in the air. You can hold it in one hand and swing it through the air and it will stay up only if you have the leading edge higher than the trailing edge.

Is the cardboard flying or just sliding through the air? If you hold the cardboard parallel to the ground as it moves through the air the cardboard slides through the air and produces no lift. If you tip the cardboard up in the front then it stays in flight but it is not producing lift. It stays in flight only because it has to flow over a mass of air because of the angle it is moving.

If a cemetrical model airplane wing moves throught he air parallel to the ground like the cardboard it produces no lift either. If the wing is tipped up in the front then the wing stays in the air only because it has to flow over a mass of air like climbing a hill. If you turn the cemetrical wing upside down again it stays in flight because it is sliding over a mass of air like climbing a hill.
There is no lift on a cemetrical wing it simply slides through the air and the angle it slides determines if it goes up or down.

If a cenetrical wing produces lift then that means you should be able to hold it exactly parallel to the ground and with enough speed it will stay airborn. Won't happen.

Like you said everyone has an opion.

That magazine artical that I read was talking about people flying model airplanes in the 1920's. I had not idea people were flying models then. It said that it was in the 1930 then the british finally convenced the americans to use cemetrical wings.

How in the world do you spell cemetrical? My spell checker says cemetrical but this does not look right. Looks like cemetary with rial on the end.

Yes, it is producing lift.

>If you take that same sheet of flat cardboard 4 feet square
>and hold it out in front of you and let go it falls like a
>parachute. Is it flying?

no, it is not

>Do the same experement again with a wing shape flat sheet of
>cardboard 12" by 48". You can't run fast enough to keep it
>in the air. You can hold it in one hand and swing it
>through the air and it will stay up only if you have the
>leading edge higher than the trailing edge.
>
>Is the cardboard flying or just sliding through the air? If
>you hold the cardboard parallel to the ground as it moves
>through the air the cardboard slides through the air and
>produces no lift. If you tip the cardboard up in the front
>then it stays in flight but it is not producing lift. It
>stays in flight only because it has to flow over a mass of
>air because of the angle it is moving.

Here's where you missed it Gary, it IS producing lift, otherwise it could not support itself in the airstream. Your senarios ignore, gravity, without gravity there is no need for lift. Lift is a force that opposes gravity. In heavier-then-air flying machines "lift" is produced by the movement through the air of a plane (wing, rotor blade, lifting body etc.) that create a pressure differential that lifts the mass of the machine. Which ever theory you choose, the result is the same.

>If a cemetrical model airplane wing moves throught he air
>parallel to the ground like the cardboard it produces no
>lift either. If the wing is tipped up in the front then the
>wing stays in the air only because it has to flow over a
>mass of air like climbing a hill. If you turn the
>cemetrical wing upside down again it stays in flight because
>it is sliding over a mass of air like climbing a hill.
>There is no lift on a cemetrical wing it simply slides
>through the air and the angle it slides determines if it
>goes up or down.

The angle is relative to the airflow.

>If a cenetrical wing produces lift then that means you
>should be able to hold it exactly parallel to the ground and
>with enough speed it will stay airborn. Won't happen.

Not sure what you mean here, but it does produce lift as long as it in the airstream at angle of attack.

>Like you said everyone has an opion.

But, the opinions I mentioned are one or the other and you have argued both. One thing that cannot be a matter of opinion is that regardless of a flat or curved cambered wing surface lift cannot be produced without the surface being at an angle to the relative wind.

>That magazine artical that I read was talking about people
>flying model airplanes in the 1920's. I had not idea people
>were flying models then. It said that it was in the 1930
>then the british finally convenced the americans to use
>cemetrical wings.

These old publications are pretty good for laughs and contain some interesting material to think about, but the fact is that even though there is still an incomplete understanding of lift, we know a whole bunch more then they did then.

>How in the world do you spell cemetrical? My spell checker
>says cemetrical but this does not look right. Looks like
>cemetary with rial on the end.

Brett and I both have given you the correct spelling SYMMETRICAL, meaning of the same shape about a plane or line. The human is said to be bilaterally symmetrical (on the outside of the body)

>Gary Weaver

What I am thinking is there are 2 kinds of lift. Air lift and wing lift produced by the air foil shape.

If a wing is placed in a wind tunnel and air flows over the wing parallel to the center line of the cemetrical wing, LE and TE are horizonal with each other, if the wing is producing lift then it should lift when the air flow reaches a certain speed.

If the wing will not lift without tilting the leading edge up and the trailing edge down then the wing is not producing lift it is being lifted by air flowing under the wing. The air that flows under the wing bounces off like light reflection off of a mirror forcing the wing up.

I read some research data that the Wright Brothers did. They built a wind tunnel and tested about 300 airfoil shapes. They had some way to measure the lift of each air foil shape. As the air flows over the wing certain air foils produce more lift than others.

Nova did a show a few years ago where they put smoke in a wing tunnel so you could see exactly what was happening to the air as it flows over a wing. Wings with a flat bottom and concave bottom produced a lot of lift without being tilted up in the front.

I don't think a cemetrical wing produces any lift of its own, it is being lifted by air flowing under it when it is tilted down in the back or tilted up in the front which ever way you look at it.

How did we get off in left field on this? I was wondering why there are no large airplanes with flat solid balsa wings. I might build a large 1/2a type airplane about the size of a Ringmaster. It should be easy to build.

Well, you are thinking incorrectly. The word lift has a distinct meaning, and it's not that there are two kinds.

>If a wing is placed in a wind tunnel and air flows over the
>wing parallel to the center line of the cemetrical wing, LE
>and TE are horizonal with each other, if the wing is
>producing lift then it should lift when the air flow reaches
>a certain speed.
>
>If the wing will not lift without tilting the leading edge
>up and the trailing edge down then the wing is not producing
>lift it is being lifted by air flowing under the wing. The
>air that flows under the wing bounces off like light
>reflection off of a mirror forcing the wing up.

This is a distiction that is not overly important. And you are not correct about the "reflection" theory, nor in ignoring the air going over the *top* of the plate.

>I read some research data that the Wright Brothers did.
>They built a wind tunnel and tested about 300 airfoil
>shapes. They had some way to measure the lift of each air
>foil shape. As the air flows over the wing certain air
>foils produce more lift than others.
>
>Nova did a show a few years ago where they put smoke in a
>wing tunnel so you could see exactly what was happening to
>the air as it flows over a wing. Wings with a flat bottom
>and concave bottom produced a lot of lift without being
>tilted up in the front.

Of course. There's books and books full of such data. A cambered airfoil produces lift at a zero angle of attack. An airfoil with no camber (i.e. symmetrical) will produce lift at some non-zero angle of attack. In both cases, aside from a "zero bias" the amount of lift at varying angles of attack are not significantly different assuming the rest of the shape is the same.

>I don't think a cemetrical wing produces any lift of its
>own, it is being lifted by air flowing under it when it is
>tilted down in the back or tilted up in the front which ever
>way you look at it.

All wings of any shape are being lifted by air flowing around them, top and bottom. Your sharp distinctions are simply not relevant or valid.

>How did we get off in left field on this? I was wondering
>why there are no large airplanes with flat solid balsa
>wings.

Because a "flat plate" airfoil, of solid balsa, is both inefficient and heavy. It will fly but there are perfectly well-understood other approaches that will, on average, work better.

I admire your desire to understand things, but you really can't make up your own definitions of things and expect everyone else to agree, or even understand what you are saying. The things you are discussing here are not new revelations or new information - it goes back to at least the Wrights.

Who is it that came up with air molecules named Hans and Fritz to explain supersonic flow? I want to say Von Karman, but I could be wrong.

I do not believe your interpretations are that far off. Observed experience does not mean invalid results. Much of what you ask seems beyond the capability for some to explain. They interpret it as a misunderstanding of the facts, which I do not believe is fair.

Even your description of "reflection" is an observed reaction that does not conflict with theory. Air flow directed perpendicular to a surface will create a region of super-low pressure as the air stream is deflected in all directions away from the point of impact. Depending on minute deflection differences, the stability of the object in the fluid flow field fails in the direction of maximum flow velocity.

This can be illustrated by your cardboard example, or by the analogy of holding your hand outside a car window while driving. At certain positions (infinitely controllable by your muscles, brain, and sense of feeling in your hand) stability is achieved, while other positions fail in a catastrophic way (your hand is blown away).

To explain your question about a flat wing at larger sizes involves a complex set of conditions including stability, control, lift, and energy. The Reynolds Number teaches us that the size of air molecules is fixed. Some things that may work on a small scale, do not necessarily hold true at a larger scale, and vice-versa. Flat wings with 049's work well because the molecules are so large, and the energy leverage is so great.

Your observations are fairly sound. What happens with a flat wing is that it is neutrally bouyant in level flight, the same as a symmetrical airfoil. The situation is different when the flat surface is deflected (maneuvered). In fact, the example of a "flat plate" is one of the fundamental tools used to teach aerodynamic lift theory. As the angle of attack increases, the flow field fails to streamline, and vortices develop. The trick with any wing is to delay the separation of the flow field, which stops lift and wastes energy.

An airfoil shape maintains the flow field beyond the thick point of a wing by the curved shape - "streamlining." In general, the thicker the wing, the more powerful the deflecting force, but it's more difficult to maintain the stream field. Thinner airfoils will maintain the field more easily (less drag), but with less lift. As soon as a flat plate is deflected, there is nothing to stop the separation of the flow field, and lift is quickly lost.

An 049 airfoil is in the regime where brute force of the engine's airflow is enough to overcome the extreme drag and loss of lift - kind've of like why some insects can fly, but without theoretical proof. I have no doubt that a flat wing in a 35-sized plane will fly, but as soon as you try to maneuver it, it will fly like the "rock" it really is. Also, any symmetrical wing - whether flat or airfoiled shape, must provide enough initial lift to achieve a cruising altitude, and must allow for the infinite corrections necessary to maintain that movement in the flow field, in spite of minute changes.

Finally, that flow field must be preserved enough, after passing the wing, to allow control surfaces to "deflect" those flow fields, creating enough minute changes in lift to maintain stability.

A lot of generalizations, but they can be proven with an open mind.

>Even your description of "reflection" is an observed
>reaction that does not conflict with theory.

Actually, it does, unless you are talking about hypersonic speeds or mega-high Reynolds numbers. Air at subsonic speeds does not act like a bunch of unconnected BB's.

The basic idea that lift is created by deflecting the air through which the airplane is travelling *is* right. The wing induces the air to move, relative to it's undisturbed position. This requires the wing to apply forces to the air, and thus the air is also applying a force to the wing. This is a mandatory condition for conservation of momentum. Some of the air is acclerated to move along with the airplane and this creates the drag force. Some of the air is deflected perpendicular relative to the line of travel, and this results in a lift force.

But the mechanism is definitely not one of hitting a plate and bouncing off like a reflection of light in a mirror.

>
> But the mechanism is definitely not one of hitting a
>plate and bouncing off like a reflection of light in a
>mirror.
>
> Brett

Respectfully, it depends on your view of semantics. Is controline centripetal force or centrifugal force? Does a wing lift because of high pressure underneath, or low pressure on top? Does a block move because you're pushing on it, or does it sit still because it's pushing back? The analogy is similar to pointing a hose at an object (or flying a kite) - the difference is that air is compressible, and that's where the complications (semantics?) begin ...

One may observe that air can be deflected after striking an object. That doesn't mean that calling it "reflective" is wrong. Turbulence itself is partially the act of air molecules bouncing back in the opposite direction. It's just that the end result is that the "reflective" energy is absorbed into changes of the local pressure field.

I tried ...

No, that's not really a matter of semantics at all. It's simply not a matter of "bouncing off" as suggested, except, as Howard says, at hypersonic speeds (when Hans and Fritz don't know the wing is coming). It is a matter making air move, but the mechanism is certainly not like a reflection. And the air going over the top is also driven downwards, which couldn't possibly be understood with the reflection analogy.

Airflow over our toy airplanes isn't compressible, either, except maybe on combat plane props.

I won't make this long since there is growing lenthy information flowing now, that's exactly what I refered to before.

Your statement about 2 different kinds of lift are exactly the 2 schools of thought I was talking about in my first reply. Brett's statement about the definition of lift is correct. There are indeed airfoil sections that will produce lift in a wind tunnel at 0 degrees AOA, however there are no actual working situations (that I know of) where that is true. In all cases, a wing plane producing lift is at an angle to the relative airflow. Then there is the the actual center line of the foil itself. An airfoil may appear in cross section to be "level" but the line from the leading edge "center" to the trailing edge "center" creates an angle of attack. Wings at higher speeds require a shallower AOA then those at low speeds. Have you looked at the site I gave earlier, it has interactive demonstrations on lift vs AOA related to speed, very good and its produced by NASA. Have a look.

Huh? There may not be many man-carrying aircraft that fly level with 0 AoA, just because the wing loading is high, but the basic idea that you can have lift at a 0 AoA (or the converse, that to get 0 lift you might need a negative AoA) is not just a tunnel phenomenon, it's definitely real.

No, you are holding it. It *is* producing lift.

>If you take that same sheet of flat cardboard 4 feet square
>and hold it out in front of you and let go it falls like a
>parachute. Is it flying?

Depends on your definition. It is not producing lift in that case. Lift being defined as an aerodynamic force perpendicular to the airstream.

>Do the same experement again with a wing shape flat sheet of
>cardboard 12" by 48". You can't run fast enough to keep it
>in the air. You can hold it in one hand and swing it
>through the air and it will stay up only if you have the
>leading edge higher than the trailing edge.

That's a tricky experiement - and it doesn't really prove the point you are attempting to make.

It's not an aerodynamic effect -it's the result of how you are doing the experiment. The center or pressure is much further away from the "pivot" in the first case, thus it takes less forward speed to generate enough torque to hold the carboard up. The wing loading is the same (assuming the carboard is of a constant areal density) and a 12x48 wing (assuming also that the 12" is the chord) is a much more efficient lift producer than a 48x48 sheet.

>Is the cardboard flying or just sliding through the air? If
>you hold the cardboard parallel to the ground as it moves
>through the air the cardboard slides through the air and
>produces no lift. If you tip the cardboard up in the front
>then it stays in flight but it is not producing lift. It
>stays in flight only because it has to flow over a mass of
>air because of the angle it is moving.
>
>If a cemetrical model airplane wing moves throught he air
>parallel to the ground like the cardboard it produces no
>lift either.

True

> If the wing is tipped up in the front then the
>wing stays in the air only because it has to flow over a
>mass of air like climbing a hill. If you turn the
>cemetrical wing upside down again it stays in flight because
>it is sliding over a mass of air like climbing a hill.
>There is no lift on a cemetrical wing it simply slides
>through the air and the angle it slides determines if it
>goes up or down.

This "angle" is *how* it produces lift. It's not that it has no lift - it's that it has no lift at a zero angle of attack. Meaning you fly at a positive angle of attack in level flight. Flat plates generate lift just like any other shape - by deflecting air. "Airfoiled" shapes just do it more efficiently.

Lift is *any* aerodynamic force produced in a direction perpendicular to the airstream. Your distinction above is moot.

>If a enetrical wing produces lift then that means you
>should be able to hold it exactly parallel to the ground and
>with enough speed it will stay airborn. Won't happen.
>
>Like you said everyone has an opion.

Right, but you are not entitled to your own facts.

>That magazine artical that I read was talking about people
>flying model airplanes in the 1920's. I had not idea people
>were flying models then. It said that it was in the 1930
>then the british finally convenced the americans to use
>cemetrical wings.

No - C/L had not been invented in 1930. Lots of people flew model airplanes back into the teens FF airplanes, and indoor. And models date back to the 1800's (or even earlier, depending on how you define model).

C/L probably dates back to 1937, more or less, when Oba St. Clair invented his 4-line system (elevator and ailerons):

http://www.aeromaniacs.com/historyofcl.htm

Nothing resembling a symmetrical aifoil on a stunt plane appeared until after the war, as far as I have been able to determine. The first well-known use was Davey Slagle's. There is no evidence that I am aware of that it was invented in Great Britain, although I see no reason not to give anyone credit.

Symmetrical airfoils were used in full-scale and other applications far before they appeared on stunt planes.

>How in the world do you spell cemetrical? My spell checker
>says cemetrical but this does not look right. Looks like
>cemetary with rial on the end.

SYMMETRICAL!! As mentioned above.

I'd really be fascinated to see this article. What issue of what magazine was this in?

Just for a bit of trivia, the Boeing B-17 (not Paul's) had a symmetrtical airfoil, NACA 0018 at the center tapering to NACA 0010 at the tip. ref. Flying Fortress by Jablonski, pp 314.

had to take that shot - forgive me ...

I imagine the undercambered airfoils used in a lot of WWI airplanes didn't help, and most of the Golden Age airplanes used flat-bottomed ones.

As to how you recover from inverted flight with a flat bottomed wing - I suppose climbing high and doing a half inside loop ought to work. But if your plane is light enough, I imagine it'd still be able to half-outside loop, flat bottomed wing or not.

As well, all of us instrument pilots fly behind the very panel set-up devised by Jimmy all those years ago (1928).

Very cool. Well thought out.

I fly a non-symmetrical airfoil equipped airplane in competition aerobatics. I am able to perform outside manuevers without difficulty. The Citabria's wing in which my dad taught me to fly acro was not only non-symmetrical, it has undercamber. I did my first slow rolls and sustained inverted flight in this airplane.

It is a matter of AOA when flying these airfoils inverted, the "flat bottom" wings will need more AOA than a symmetrical airfoil but are capable of inverted flight nontheless.

Chris I am sure your Citabria will fly inverted but how about five foot off the ground? Or twentyfive foot. Not for me.

Don

p.s. Good luck at Clovis, would like to be there but a long haul from Fort Worth.

The worst aifoil I've used is the one from the Veco Kit Smoothie.
I'm looking forward to getting a Bordak ARF Smoothie, 1st I would like to compare it to my 1958 Veco Smoothie and also have an instant old time plane to fly!

Or rather, he's the engine. He's giving the thing forward velocity.

>>If you take that same sheet of flat cardboard 4 feet square
>>and hold it out in front of you and let go it falls like a
>>parachute. Is it flying?
>
> Depends on your definition. It is not producing lift in
>that case. Lift being defined as an aerodynamic force
>perpendicular to the airstream.

In this case, there's no "engine" and no forward speed. But if he puts some noseweight on that piece of cardboard, to the point where it will glide, and give it a shove, it will produce lift (up to the point where it stalls or tucks under and stops moving forward).

That's true too. But the setup is more complex than that, and the conclusion that he seems to be reaching is a function more of the way he's pushing it forward than it does any intrinsic aerodynamic effect.

"No one will have a lighter Tip Weight Box than Me."
"Homer Simpson."

"No one, I repeat no one will have a lighter Tip Weight Box than me."
"Homer Simpson"

If one of you catches me taking a peek at whatever he is up to, or in a moment of extreme weakness actually responding to same, please, *please*, *PLEASE* drop by the house and cut off all my fingers.

Ron B.
F4Fguy

Dan:

NYAAA!NYAAA!NYAAAHH! I resisted longer than yououou!

Gary,

Take a look at this site, there's a section on lift and angle of attack. There's even a real time lift simulator that you can experiment with.

If there are any openings, prehaps you could get GW a job working in your dept. I am sure that he would be an asset and I'll bet you guys could use some new ideas.

His experiment with the cardboard is brilliant and something that I don't remember anyone else around here thinking up. I mean, lets get real here. It could be that our planes, along with fullsized aircraft, arn't really flying at all. That some other principle is at work. I for one, have thought this for a long time.

Think about this a minute. Fish live in water, right? Well, water is kind of like air, just thicker, and the fish fly through that just fine. Don't see any airfoils do you? Aha! Thats 'cause the fish are SWIMMING. Get it?

OK! Check this out...

If airfoiled surfaces actually produced lift we would have come to a better understanding of the principals involved, a long time ago. The fact that we have not, is clear evidence that at least a portion of our scientific/technical community has gone pretty far down the road of no return (Or perhaps the one that goes to Sandusky Ohio!).

Many years ago I read a magazine article about some guy from India. He was flying long distances, at extremely high speeds, using a totally non-airfoiled plate type of device, made from some kind of fabric. I have given this a lot of thought, and yes, perhaps the fabric took on an airfoil shape because of the forward motion and created lift. I guess it could but I really don't believe that is the case. The answer lies elsewhere.

This is something that deserves a second look and perhaps some serious investigation and experimentation. If these devices were in operation when I was a kid, why aren't we seeing this technology in use today?. Probably because of the stodgy thinking going on in the military-industrial complex today. On the other hand, this technology could be being kept under wraps by those intent on the accumulation of power, to be used in ways that the rest of us don't yet understand.

What ever...

The FACT is, that there are a lot of other systems that work and we have long had proof that an airfoil is totally unnecessary for flight. The bee that stung me last week didn't need an airfoil, so why should your stunt plane? (That wasn't a real question. I just said it, so that you can understand my thinking process.)

Quite some time ago, I duplicated one of these aircraft working from an illustration that I found in a book. It didn't take long for me to create a working model. When I tossed from a third story window, my fabric, flat plate model exhibited every characteristic of flight that I could think of. It went forward in a controlled fashion and landed undamaged in my yard. The flights were short but I thought that they could be a lengthened if I could solve the control system issues. The picture that I was working from didn't show how a pilot controlled the aircraft. I couldn't be too hard though, since those guys figured it out so long ago.

Another stumbling block was the power system. At the time, I couldn't quite figure out how to mount an engine. That's probably the big secret, since they didn't show that a propulsion system in the picture either.

Anyway, I abandoned these experiments about the time I went to college and began working towards my degree in woodworking. Today, I am far too busy with work commitments and family matters to further pursue my experiments.

Since you guys know so much more about this subject than I do, I would be happy to forward you my notes, drawings and calculations. Math was never my best sugject but hey, that was before computers! I'm sure that with a modest expenditure of time and attention, you could really make some headway.

A little fresh thinking goes a long way. Try it sometime!

So much for venturi effects, huh?

I'd be interested in reading the details of this.

[photo not recovered: 3e69bb3870f12ad5.jpg]

"An expert is someone who knows some of the worst mistakes that can be made in his subject and how to avoid them." -Werner Karl Heisenberg

Each wing or air foil has a certain radius it will turn before it stalls. The elevator should be set so it can not make the airplane turn so sharp that it is too sharp for the wing to turn. Seems to me an airplane kit and all airplanes should have some type of data sheet telling the person something about the air foil wing shape of the airplane. Certain air foils can turn sharper than others. Kits need a code number like R10 means this airplane will turn in a 10 ft radius, R20 would mean this airplane will turn in a 20 ft radius.

Most Fish are symmetrical shaped.

We live at the bottom of an ocean of air.

A guy in San Diego made combat kits awhile back with a lot of specifications on the label. It was sufficiently detailed that one could calculate the density of air that statisfied the numbers on the label. It was about 2.2 atmospheres, as I recall.

As for elevator limiting, that's what we do with combat planes so we won't stall the things in panic maneuvers. At the 1984 Nats in Reno, Reynolds number was so low that we had to limit the travel to a lot less than what worked at sea level.

Yes, a top view of a fish looks a lot like an airfoil.

In a way it is confusing the issue to refere to such airfoils as flat bottom. If you consider an airfoil to be a symetrical teardrop shape developed over a camber line, then the same can be said of any cambered airfoil. There are different camber line shapes that exibit different characteristics. Flat bottom sections can then be viewed as the result of combining a particular camber line with a particular symetrical section. Of course they are not developed that way, usually for building simplicity.

>The theory that the inboard wing should be longer than the outboard >wing for cemetrical air foil shapes because the outboard wing is >traveling faster and producing more lift is non since because no >matter what speed the wing is traveling it never produces any more >lift. All it has to do is over come gravity.

Part of this is true and part not. In level flight, the overall lift is equal to weight. In a turn lift is equal to the combined effects of centrifugal force and the componant of weight perpendicular to the airstream at any instant in time. However while the total lift remains unchanged, there is a velocity differential across the span and since lift is proportional to velocity squared, there is a lift differential across the span as a result. The outboard wing produces more while the inboad wing less. The total lift is the same but the centre of lift has moved outboard by a small amount. Placing the CG at this location cancells the rolling moment. Offsetting the engine thrust line through the CG (now somewhat outboard) cancels thrust/drag/enertia moments, everything ballances nicely. Depending on the fuselage configeration, this can lead to a slightly longer inboard wing and a nicely trimmed model. Of course I have seen many models where this has been far overdone.

>The artical goes on to talk about other things like thicker ribs >makes a wing turn better, thinner ribs produces less drag, longer >ribs, shorter ribs, longer wings, etc.

This is because the thicker blunter sections maintain good airflow over a wide range of angles of attack at the expense of some drag.
A very thin flat plate will stall the upper surface at even low angles of attack due to the sudden angular change of the upper flow behind the LE. At any angle of attack you get smoother flow from a curved plate where the LE is tangent to the airflow but that only works well at one angle of attack. Reduce the AOA and the lower surface stalls, increase it and the upper surface stalls. This is exactly like a sail. Using some nose radius reduces the severity of the change in flow direction helping the air to remain attached in a smooth flow. The blunter the airfoil, the greater the opperation range of angles of attack. As lift is proportional to angle of attack in the region before stall. A blunt airfoil will be capable of a greater range of lift. Remember this is at the expense of some drag.

>This got me to thinking. Many of the 1/2a airplanes have flat solid >balse wings.

Yes but not a sharp LE

>I have never seen a large airplane like 52" wing span with a flat >solid balsa wing like 1/2a type airplanes. It seems to me a flat >wing would have very LOW drag and an airplane that would normally >need a 40 size engine to fly would fly good on a .15 size engine.

The thin flat section might produce less drag, TE sharpeness is a factor as well. If thrust is greater than weight, almost anything will lift on the prop but it isn't necessarily flying anymore than a helicopter is flying. Just try to define flying anyway. It comes down to degrees of efficency. A thin flat plate wing can be made to fly but it's performance will not be good over a wide range of conditions compared to a true airfoil wing.

>It seems to me a flat 52" wing would fly slow with no problem, >probably fly great at about the same speed or a bit faster that 1/2a >airplane 35 to 40 mph. One thing would effect another so flying this >slow would reduce line tension and might be hard to fly in 60 ft >lines unless the lead outs were set back, way back to create more >line tension.

It might fly level OK but would it have the power for climbs or to accelerate out of tight turns?

Would it produce enough lift for tight turns?

You can get away with this sort of ting at 1/2A size because power to weight is heigh but even a 1/2A benifits from good design.

Nonetheless, let me try to shed a little light on things that seem to be causing confusion.

First, camber.

There has been some discussion of camber and its effects on the ability to produce lift. Here's some basic stuff about it.

Camber is nothing more than a line connecting the leading edge and the trailing edge of an airfoil (in cross section). Sounds easy? While not quite that simple.

Most airfoils have "three" cambers. (1) the upper camber which is simply the upper surface of the wing. It's what you see when you look down on your stunter.

(2) the lower camber. This is nothing more than the lower surface of the wing...what you'd see if you slipped under the wing. It might be simpler, of course, to turn the airplane over but, hey, whatever works.

(3) and most germane to our discussion is the "mean" camber. This isn't as clearly viewed. What it is is a line (again connecting the leading edge to the trailing edge on the airfoil profile)which is at each point on its length equidistant from the top and bottom cambers. When one discusses the relative "camber" of an airfoi section they are really talking about the mean camber. It is the shape of this line that determines if a wing section is, in the vernacular, a "lifting" section or, as in this case a "symetrical" or "non-lifting section.

Surprisingly (until you think about it) the 12" X four foot flat sheet of cardboard Gary discusses has "exactly" the same "camber" as does the ubiquitoes symetrical "stunt" airfoil. In each case the "mean camber" line, equidistant from the top and bottom surface (upper and lower cambers) is a straight line and they are by definition "non lifting" sections.

Now, does this mean they can't produce lift. Obviously not. WE've all seen both 1/2 A Wizards with flat plate wings and Impacts with big thick wings fly. To fly they need to produce lift, ergo, both these "non-lifting sections" do, in fact, produce lift under the proper conditions.

Note that per this discussion of camber, it is entirely possible for a wing which has a convex camber on both the top and bottom surfaces to qualify as an "undercambered" section if the top surface has a greater arc than the bottom.

Let's discuss lift and the dueling definitions thereof. Whichever definition suits your fancy, in the final analysis what matters is the "difference" in pressure between the upper and lower surfaces of the wing's surface. Don't get bogged down in the esoterica of the pushers and pressure advocates. The bottom line is that any sort of shape can produce lift if the pressure on one part of it is less than the pressure on another part. It ain't rocket science (sorry, Brett).

For proof of this note how a well struck golf ball flies. At first simply a projectile launched by a good blow at an angle consistent with the loft of the club and the club head path at impact. Almost immediately, however, the spin of the ball (back spin) produces a lower pressure on the top of the ball than on the bottom and you will see the ball actually rise above the initial launch trajectory. Ta Da, difference in pressure, difference in lift the object rises! (Unless, of course, your golf skills are akin to my own in which case if the ball is struck with the club face pointed right or left much of the spin created will be at a sideways vector and the dreaded slice and/or hook sends you into the woods. Once again, difference in pressure produces lift)

Now, how do we produce lift. (by the way, the fish analogy isn't a real good one because fish are, not unlike submarines or blimps, subject to buoyancy considerations, i.e. the displacement of an amount of the fluid in which they operate...thus able to be "suspended" in that fluid. The do then move up and down in that medium by virtue of directed thrust...too much. sorry)

Nonetheless, in air we produce lift by moving a "surface" (as we already know that surface can be almost ("almost") any shape) through the appropriate medium. Let's say just for fun...air.

Unless the camber of that surface is precisely at zero angle of attack relative to the air it "will" produce a pressure difference between different parts of the surface.

The amount of lift thus produced will depend on only a few things (all of which effect the pressure difference on which the lift depends).

1st. the thickness of the air, known as air density. No surprise here. Thick stuff is better than thin stuff.

2nd. The efficiency of the shape of the surface we're moving through the air. We generally call this the co-efficient of lift. This is nothing more than a measure of how effectively a particular airfoil utilizes the other forces we're talking about to produce pressure differential (*lift*!)

3rd, the angle of attack at which the surface strikes the air. Not surprisingly, as the angle increases the same chunk of wing will make more lift...up to a point. That point, of course, is where the airfoil will no longer support flow over the upper surface and the airfoil stalls, no longer producing lift.

4th ... and most importantly because pressure differential goes up as the square of it ... is the speed at which the air flows over (and under) that surface. The faster your lifting surface goes the more lift it will produce with all the other factors remaining the same.

So, there you go. Lift is a simple combination of a surface that will separate areas of lower pressure from areas of higher pressure. Thus, as simply as dropping a sheet of cardboard or plywood, a pressure differential will exist that causes, at least initially, the object to drop more or less like a parachute. Of course, unless like a parachute the center of gravity is well below the "lifting surface" the object will (by force of air pressures) quickly rotate to a less "draggy" relationship to the air and start an alternating ballet of flopping around itself as it falls to the ground at some speed faster that the "parachute" configuration but slower than a mass of the same "weight" that is uniform in shape...like a bowling ball.

Curiously enough, even that bowling ball will have a maximum speed based on pressure differential and gravity. Were it not for the pressure differential the bowling ball would simply go faster and faster and faster until it struck earth. It's what we call terminal velocity and it could well be defined as "lift"!!!!

Any of this make the concepts you're struggling with any easier, Gary?

Many of us call something else the coefficient of lift.

"Curiously enough, even that bowling ball will have a maximum speed based on pressure differential and gravity. Were it not for the pressure differential the bowling ball would simply go faster and faster and faster until it struck earth. It's what we call terminal velocity and it could well be defined as "lift"!!!!"

It's defined as "drag", though.

OK, get technical on me. It does mean that some shapes produce lift more efficiently than others.

>Many of us call something else the coefficient of lift.
>
>"Curiously enough, even that bowling ball will have a
>maximum speed based on pressure differential and gravity.
>Were it not for the pressure differential the bowling ball
>would simply go faster and faster and faster until it struck
>earth. It's what we call terminal velocity and it could well
>be defined as "lift"!!!!"
>
>It's defined as "drag", though.
>
>

Perhaps so, but would you agree that the pressure on the bottom of the ball is greater than that on the top? Again, not a very efficient shape in terms of lift; in other words the L/D isn't very impressive.

Lift coefficient doesn't have anything to do with efficiency. It's just nondimensionalized lift. It's lift divided by wing area x dynamic pressure, which puts it into a form that is convenient for some calculations.

These are merely definitions, and don't have anything to do with the physics, but give us a standardized way of talking about it.

Well, double heck. If you want to really get down to the basics we haven't even started to address the more important criteria for our use...aspect ratio.

The planform of our wings is ever so much more important than the airfoil. Take an otherwise identical plane (wing loading in particular, i.e. weight to wing area) and fly it with a flat plate wing at five or six to one aspect ratio (wing five to six times greater span than average chord) and then make a wing of the same area with a theoretically perfect airfoil but at an aspect ratio of "one", i.e. span equal to average chord, and the flat plate will beat the sox off the "perfect" airfoiled version in a stunt contest everytime.

When it comes to maneuvering the stubby version will be not very dissimilar to a bowling ball in fact. (OK, that's an exaggeration. It "will" fly...just not very well unless it's got a whole bunch more thrust than the flat plate version to overcome all the drag at any angle of attack high enough to generate the lift necessary to maneuver)

This is probably true, but the negative effect of induced drag is not as great as predicted by the old classical theory for aspect ratios from about .75 to 1.5. In this range, CLmax peaked at over 1.8 at an aoa of about 45 degrees for an unflapped circular wing (A/R = 1.27) in Zimmerman's tests using the Clark Y section (NACA TR #431, 5/5/32), because of the effect of "tip" vortices reattaching the flow over normally separated areas at high angles of attack. These wind tunnel tests were for a 14" chord at standard atmospheric pressure. These affects were observed for circular and elliptical, planforms, but not for rectangles.

In the full-sized realm, the Snyder "Arups", Johnson "Uniplane", Hoffmann wing, and Zimmerman V-173 and XF5U-1 (to the limited extent of its tests) demonstrated wide speed ranges and some short takeoff and landing ability. I have a VHS tape of an old film showing the Arup S-4 doing touch-and-go's at South Bend's Bendix Field in 1933, Some low-speed landings and steep climb outs are apparent with 70 hp/1200 lb.

If you dodn't mind high angles of attack and (as you suggest) slowing in turns, low-A/R models should turn tightly with the power advantages we have.

SK

Ed.: Spelling Correction

Aha! Note the clever insertion of the words "power advantage"; thus proving my point!

Ted

p.s. Yes, you could get the body angle to change pretty abruptly but actually getting it to fly through a corner and complete, for instance, a square eight would seriously tax anything you would call a normal stunt power loading. Try doing a stunt pattern with one of those flying saucer 1/2As that I see kids learning to fly with.

A correction:

>That point, of course, is where the airfoil will no longer support flow over the upper surface and
>the airfoil stalls, no longer producing lift.

It just produces less lift.

SK

I think youre getting zero angle of attack and zero lift angle mixed here .. only a symmetrical section has a zero lift angle at zero AoA - an airfoil with *any* (mean) camber will produce lift at zero AoA, and zero lift at some other angle.

It gets a whole lot more interesting when you put flaps on the wing. Then you can do squares, triangles and anything that models with fat wings can do. The point is you are making a cambered airfoil by deflecting the flaps, just like models with fat wing sections. This seems to largely overcome the shortcomings of the actual wing section. You are right in one respect. With models using 15-19 size engines, drag is reduced & the whole shebang works better with sheet wings than fat ones in my opinion.

Going much larger gets into stiffness problems and I have to concede that the engineering advantages of fat wings really do take over.

Yep - pretty hard to make air go around sharp corners, so it separates and stalls.

>It gets a whole lot more interesting when you put flaps on
>the wing. Then you can do squares, triangles and anything
>that models with fat wings can do. The point is you are
>making a cambered airfoil by deflecting the flaps, just like
>models with fat wing sections. This seems to largely
>overcome the shortcomings of the actual wing section.

I think it's partly because of the camber, and partly because the AoA is set by the deflected flap, so the fixed portion - the wing - is at a much lower angle to the oncoming air. So it doesn't have to try to get around the corner at the LE.

A friend of mine in NASA sent me some of the tunnel test data on the Kline-Fogelman. "Worst airfoil we ever tested," paraphrases his description.

I guess it was similar to 049's: put it on a small hand-launch glider, and it gave good results. Scaled up, it was a disaster.

So yes …. It is question of semantics. We are automatically thinking about usual “fluid mixing” theory of lift using mass inertia of a liquid, but it is really not the only way how to make lift – in meaning to keep a vehicle in air. And I do not mean only aerostatic flying. It is that “reflexing” in supersonic aerodynamics or even low RE method of “drag flying” used by small insects at very low RE numbers using its viscosity instead of mass inertia (did you hear about Strouhal number?). Yes, it is rather swimming then flying, but it not needs usual wings at all – for example an insect Mymar regalis does not have wings (I mean area sealing higher and lower pressure) and still can fly – using viscosity. But it is extreme, what about compressor pushing air under the wing and making that necessary “pressure difference” … or forget wings at all – we know vertically launching aero plans … I think they do not need wings at all … or shall we go to rockets? They do not need even the air around … they are just putting air of proper pressure in proper time to proper place … so what is flying and what is not?

If we speak about usual lift on our stunters in usual speeds and usual wing loads, then it is really about mass inertia in liquid and its acceleartion. It IS about acceleration in liquid which makes pressure difference and which makes lift over and under some sealed area. But what and how is deflected on our wings looks like a big mystery – at least I see it that way reading articles about lift production. Brett is completely right – it is NOT deflecting airstream down on lower wing surface and it is also NOT interpretation problem or semantics or whatever - it is just misinterpretation – the same type of misinterpretation like that airfoil makes lift because it upper surface is longer then lower surface and therefore the speed is higher there – as we see it in most of books. It is based on presumption that particles separatet at LE must meet again at TE – that is far from true, they do not meet at all – just opposite is true the lift production is based on fact that they do NOT meet anymore, that upper will come far earlier.

Yes we accelerate the air on our airfoils, but we do not do it downwards. Initially we do it upwards. If you have any plain body and if you give him a positive AoA, then you make a “restriction” to airflow under the wing. The air acts like an incompressible liquid and just cannot slow on lower side “ramming” to its area. The only way is to run OVER the leading edge to upper surface (therefore initial acceleration upwards) and then follows to TE ad fills the area right of the angled wing. So it all means much larger volume of air leaks over the upper side of wing – and yes, the only chance for that incompressible volume is higher speed on upeer than on lower side. We are just pushing fraction of air from lower side upwards to upper side.

Now comes the Bernoulli saying HOW MUCH lift we have, but he did only a tool to enumerate that pressure. His equation does not explain anything, it is only analogy. The truth is, that we are ACCELERATING air stream to follow surface of wing (initially from bottom to front, then up over the wing, then back to TE and then down the angled area). But mass inertia wants to go straight and we are FORCING it somewhere and that needs FORCE = LIFT. The pressure difference is just another expression for that phenomenon (and equivalent).

So the lift depends how much air we are mixing (the volume = area of wing), how heavy is that amount (the density) and how strong we do it (angle of attack). So far really does not matter what is the airfoil. And … honestly it really does not matter IF there is ANY airfoil. We know that there are really well flying rotating wings (like if you throw a sheet of thin balsa – it rotates and still fly really well) or we know wings made on base of rotating cylinders – or even that Ted’s ball. The only what matters is, that there is something forcing that air to upper surface – the angle of attack, the curvature of lower side (chamber), the flap, the draggy lower surface like we see on BE props or rotation of round body. Everything is based on the same base – circular flow around the sealed body – that is the secret. So if you have ANY usual airfoil with such described airflow and you will add say 1 deg on AoA you will get 0.11 on lift coefficient. Really does not matter what is the shape of the airfoil.

Yes, we can do it wrong and that comes the airfoil effect. If we go to extremes, we can lose that nice smooth airflow. I am peaking about separation – does not matter if on LE, on TE, on hingeline or on lower side in chamber. Only in this case the shape of airfoil makes the difference. One airfoil separates earlier than another, and one airfoil makes more drag than another. That lift and drag makes that “efficiency” mentioned above. But if you take ANY usual airfoil, you will see on lift/alpha curve that adding 1 deg AoA in working area of that polar makes the same amount of lift – 0.11 per 1 deg – does not matter what is the airfoil. And that also makes that straight (linear) segment of that curve – between two extremes when the airfoil loses its regular airflow. The airfoil shape only makes boundaries for that regular flow.

And why that conflict with Bernoulli? That is also misinterpretation. That equation jus says something about constant internal energy. It speaks about conversion of that energy without exchanging out of that fluid. It does not speak about “quick particles having low pressure”. That is misinterpretation. It even do not say that airstream of higher speed has lower pressure. That is also big misinterpretation. It says that if you ACCELEARTE such a stream to some higher speed, you will have lower pressure. Or if you decelerate that stream back, you will have higher pressure. It is pretty simple – how you want decelerate that stream if you not act by higher pressure? And what is the amount? That is simple it must eat its energy – so that is that “conservation” of constant energy in stream. Bernoulli does not speak bout viscosity, so no surprise that its equation does not work well in our high-speed thin and long venturies where boundary layer thickness is comparable to its crossection. That is just wrong usage of the equation – Howard did nice test of that – if I remember well the viscosity in boundary layer was major effect making suction in vetnury – exactly as we expected. We have another equation dedicated for pressure in pipe - the Bernoulli equation is just wrong hammer for that nail , but it does not mean out wings do not fly

The main drawbacks, as pointed out above, they have pretty narrow limits where they work effectively. MarisD got it right. Flat plates are OK on small, light models. Once you get over 18 in. or so, or over a6-7 ounces with a Half A you get into trouble. Not to say someone couldn't figure out how to build something bigger and faster.

Watching some of the flat plate RC stuff fly, they generally are pretty terrible flyers- touchy, subject to overcontrolling, lousy glide, etc. But they are cheap, fast and easy to build.

1/ Those models are very slow and small, so the RE number is very small and you look to airfoil properties, thicker airfoils make sence only in higher RE numbers >30000. Thin flat 3% airfoil has same properties in wide range of RE number sub or super critical, so that thin airfoil is ADVANTAGE on that model.

2/ Those models do not fly on wing, they has large angles of attack and prop makes coparable thrust to lift of wing. The wing is rather another stabilizer against the prop torque - ailerons are typically 40% of wing area.

This opens a point I have been curious about for some time.

Cdi = Cl^2 / (Pi . AR ) . k

where K is the planform correction factor.
When is K = 1 (eliptical plan form)?

Is there a quick and dirty way to estimate k or some guide like value for rectangle, value for eliptical?

I did some estimates based around vectors of local induced incidence which I derived from local Cl. I based local Cl on the proportion of local chord to local eliptical chord as that seems to be roughly ture. However I do not know if that is really a valid approach.

Any comments or hints please?

Maybe this needs a new topic.

Yes k=1 for elliptical planform.

You can find chart in another thread:

http://www.clstunt.com/cgi-bin/dcforum/dcboard.cgi?az=show_thread&om=10123&forum=DCForumID1&viewmode=all#61

in message #61

It just means that optimal taper is if the tip is 40% of root, but typically the k is no more that +10% (k=1.1) on our ususal wings.

Sweep back under 10 deg does not make any signifficant difference, ~20 degrees make +10%, 30deg makes terrible 40%, but 45 deg makes already worticles FRONT of leading edge and k=2.4!!! That is reason why to build supersonic planes landing with different geometry on wings. For example Concorde had clearly visible worticles front of tip leading edge at landing. It completaly kills lift on tips at that low speed. The rurvature of leading edge helps little bit, but not too much.

I don't think I've seen any with flat plate wings. They're usually flat bottomed wings, with a curved top surface. Have to put those (yardstick) spars somewhere.

I have a "Shock flyer" from Ikarus, whole model is from polystyrene homogenous foam 3mm thin and comes already colored (that is the beauty of electric power) - you can see building notes on internet:

http://www.backyardflyer.com/click_trips/sep04/shock_1.asp

... and yes, I am thinking how to convert it to CL, but problem is it's low speed - it does not give too much chances for line tension ... it will need some trick ... like centrifugal regulator ... something like CL slowflyer ... winter is long

http://www.spadtothebone.com

The Shock Flier is more or less the sort of plane you find on:

http://www.foamyfactory.com

Yeah, they look very interesting, not to mention simple and inexpensive. I think they can be made to work for CL by decreasing the gear ratio and using a smaller prop, and if all else fails, use a brushless motor. We're not interested in 3D flying, which is the reason I think they're set up to fly so slowly.

To the shock flyer - the engine is not problem, the problem is rigidity, if you fly it at higher speed, it is terribly flattering. It must go slowly – that is the only way that it makes sence.

BTW - why you think we are not interested in 3D flying? I saw hovering CL model (originally carried deck model) and it was biiiig fun … just try 2 minutes long wingover and you will see

I can imagine such a model on 5m long lines with automatic throttle flying very slowly. Probably not stunt champion, but it can make lot of fun.

I will cry Uncle from knowing little much more specific than my compressible and incompressible fluid pipe and duct flow.

Flame suit secure, fire away!

Randy,

That's what I thought.

I would note that this thread is far and away the most popular currently on SSW in terms of contributors.

Often it seems that the supposedly "artsy/fartsy" threads do attract the greatest response. That isn't all bad.

It might, in fact, be a little frustrating for Gary to weed through all the responses, but, looked at another way, he could print them all out and refer back to the ones he didn't fully comprehend after some of the more basic ones have become clear. Eventually, I've no doubt, should he persevere he will come to understand those that provide valuable information and reject those which his own intellect tells him lack foundation.

I've written a lot of articles with exactly that expectation. The same approach I advocate in terms of reading Wild Bill's CL Aero Made Painless. Every time you read good information you will pick up a little bit more as a result of what your mind processed from the previous exposures.

Readers shouldn't bemoan the appearance of technically advanced info on a thread. In fact, it should excite one because it is indicative of a question that has piqued the interest of those most likely to provide valid data...even if at first blush it seems like jibberish.

Enjoy the fact that Howard shoves his needles deep into Ted's hide. It forces a response which will further illuminate the discussion.

Let's face it. The guys who are truly top drawer on this stuff, Paul, Brett, Howard, Igor, Randy, etc. are unlikely to be drawn into a discussion of how to make your 1/2 A Wizard fly inverted. But subject matter that does draw their attention will elicit information that will provide the answers for not only the Wizard flyer but also the next Paul, or Howard or Igor.

Let's face it. They all work the same way. It is simply a matter of how to make your plane perform as well as you want it to. My bet is that every time you make it fly that well, your expectation for the next flight will be even greater.

That's the beauty of Len's place.

I apologize for not remembering who did this, but...

A number of years ago Big Art (Adamisin) came back from a trip to Australia as a guest of the stunt flyers in the Sydney area. When he came back he was quite complimentary of a flyer from the area who competed in a contest he judged who flew a flat plate winged stunter. I highly respect Art's opinions regarding stunt model performance and was intrigued by his report.

As I recall, the ship was flapped (which makes sense) but it was still basically a big 1/2 A Wizard ... maybe powered by a .15 or .25. Anybody down under who is familiar with this airplane could make an interesting contribution to this thread.

I remember it flew quite well, and would certainly do reasonable squares.

I think it was powered by an Enya 25, maybe a diesel, installed inverted in a kind of "pod" that supported the engine mounts & tank.

I certainly can't argue your reasoning. But with that said I still wish a simple question would get a simple answer sometimes. Gary
really is having a ball learning and experimenting and sometimes I think pulling our legs. But when he gets into something like this he's really searching but is quickly buried. Responses have ranged from sacrastic ridicule to effects of hypersonic airflow. He was just trying to understand the basic phenomena of lift. Instead of working to that end, the thread was commandeered and people quickly forgot its origin.

Hi Randy,

I don't disagree at all with your underlying premise. In fact, your litany of "otherworldly responses" was the catalyst for my attempts to address the pressure differential approach in a more elemental way (not without making myself a bit of a bullseye, I might add).

Still, we're all adults (or at least near adults) and I've no doubt Gary is entirely capable of reading, digesting and/or discarding responses as he sees fit. If we assume that an apparently naive question presupposes a naive and incapable individual I'm afraid our responses would come off as condescending. Such a result might well be more offensive than what we've seen happen time and again when a thought provoking but seemingly basic question draws the rave reviews represented by dozens of responses.

IMHO threads like this represent the best of a forum. Yeah, half the time I only understand about 50% or less of responses from the mathmatically inclined amongst us like Igor and Brett. Heck, I only understand about every other word of Howard's posts...which ain't much since his average post is about five words! (That, by the way is why mine are always divided by chapters. Somebody has to balance Howard or the earth will tilt off its axis)

Nonetheless, I always learn something from them and understand more the next time they post. Education without the Principal's Office. It's a grand thing!

Fly Stunt

This is a widely held belief at the places where I live and where I work.

Hope to see you tomorrow.

The desirability of a "simple" response is precisely why I posted regarding the flat plate stunter from down under (Hi back to Tim Gee and my Kuringai friends, by the way).

One of the things I've always felt was desirable for conversations amongst stunt flyers was the need to talk more about principles and less about the esoteric mathmatical derivations of same. Not because the math ,etc. isn't valid, but because from the average stunter's point of view it lacks pragmatic value.

Once again, it is informative to quote Wild Bill. Although a lover of math and the scientific explanations of aerdynamic phnomena, he also understood well the need to express the mathmatical material in a manner easily understood by the "masses".

One of his statements that I've always remembered (perhaps not verbatim but an honest paraphrase thereof) was to the effect that"... the most scientifically derived airfoil is only a couple of percentage points superior to one drawn around the outside edge of the sole of his best dress shoe". Precisely! Especially if you're talking about symmetrical airfoils. (How do you spell symmetrical, anyway? I don't have a spell checker and never know how many mmmmmms to put in)

That Wild Bill quote was precisely the motivation for the comments in my posts regarding aspect ratio/vice airfoil, etc. Ditto for the mention of the flat plate winged stunter down under. The message wasn't to belittle the accuracy of the comments of the more learned posts, only to point out to the readers attempting to make sense of the material they aren't yet ready for that a doctorate in math and/or aerodynamics is not a prerequisite for a saisfying venture in stunt design and flying.

Fly Stunt

http://www.aviation-history.com/theory/lift.htm

Frank Williams has added a reply (#94) containing a site that illustrates both sides of your "2 kinds of lift" thoughts. I don't necessarily agree with this gentlemans's conclusions but its a good example of the 2 schools of thought I mentioned.