Looks like the administrator is being too lax.  Some people just know what button to push.

When a guy whose aeronautical knowledge is magazine-article deep continually claims technical superiority over the rest of us because we "don't understand"  the concept of the gyroscopic effect on a propeller being a function of it's distance from the airplane's cg, the stupidity of full-span flaps because of their excessive wing tip "vortexes", or the special aerodynamics of weather vanes and lawn darts not taught in school, it's pretty hard to keep from picking on him.

When a guy whose aeronautical knowledge is magazine-article deep continually claims technical superiority over the rest of us

BS.  Those are the low self esteem voices in your head, Howard.  I never claimed any such thing.  I just don't agree with everything you and your substantial group of self proclaimed "definers of the everything stunt that is right" say.

By not agreeing with you (in any case) it means that means I am "claiming superiority" over you.

In fact, I have never claimed to be a member of the SACRED BRAIN trust that you, Buck, and all the other aerodynamic supra geniuses belong too.  I have gone out of my way in my articles to say that I make no claim whatsoever to being an aerodynamic engineer. 

Now go find ManBearPig...  I am cereal.

I think Sparky should create a new forum, called the "EGO parking lot", and that it should be the first place we all go.

You know what it is for.

What's missing is how beams work.  The max stress in beams, as I recall, is proportional to the moment of inertia of the cross section, so, for a given strength, the thicker the wing, the lighter.  Similarly, for a given torsional stiffness, the thicker the wing, the lighter.  Brett's story was about how he was able to exploit these properties when better engines reduced the drag penalty for thickness.   Indeed there's stuff like paint that is proportional to surface area.  You could trade these and see how they come out.  By my ciphering-- and you guys can check--, an NACA 0018 has 0.094% more surface area than an NACA 0015, and the square of thickness ratio is 1.44.  So the weight that's in an 0018 wing for bending strength would be 69% as heavy as for an 0015 wing, and the stuff that's proportional to surface area in an 0018 wing would be .094% heavier than that of a 0015.   

I miscalculated on my last Impact and used the sheeted airfoil as the template for the unsheeted root rib, so the root was .15" thicker than that of the previous Impact.  The new dog weighs 63 oz., and the old dog weighed 66 oz.  There you have it.

Now listen up all science people...

Stop using the word *proved*.

Little if ANYTHING in stunt has been *PROVEN* as there has been very little (if any) *real* SCIENTIFIC METHOD applied to the application.  There are rare examples of real science, and little if any *real* modern aerodynamic testing or data collection has taken place to date when it comes to our stunt models that fly about 55 MPH held by a string in cross winds that can reach nearly half that of the forward air speed.  Even in the case of wind tunnel testing I REALLY DOUBT the conditions and speeds that we fly at have been tested by Boeing, NASA, Lockheed, etc.

When it comes to stunt airplane designs, there are "theories", "observations", "opinions" (both informed and uniformed), consensus (be it large or small), a whole crapload lot of conjecture, and finally a huge dose of political posturing from the brass collectors to mix it all up (you know...so and so's design is "the best" because he won XXX number of contests with it----never mind he mind have superior hand eye coordination and simply be a superior pilot or a frothing at the mouth completely obsessed type A perfectionist winaholic).

Aside from the extremely few times that someone actually made apparatus, collected data, or performed calculations or simulations (as in the case of Frank Williams experiments, Line 2, and now the ESC feedback in flight load data from electric) very little data has been collected, or analysis performed to conduct real SCIENCE.  No real conclusive *PROOF* of superiority is evident in any of the stunt designs that are in use today.

To mock the simple methods of observation used typically be just about everyone in this sport with pseudo scientific claims of "consensus" claimed as "absolute proof" is an insult to every stunt flier that does not have a formal education, and relies on simple observation, simple experimentation, sweat, and open mindedness to try new things to achieve better performance.  

All this "show me your data" stuff is just elitist bull.  Nobody has data.  If I say full span flaps cause drag...  it is because that is what I saw in the models that I built.  It is not my responsibility to "prove" that I am right, maybe you should PROVE that I am wrong!!!  You can't!!!  You can give your "opinion", and throw out your pedigree but I doubt you have the facilities or willingness to do any real testing to show one way or the other (and frankly, I don't care what flaps you use---go with God my son...).

To throw the word "proven" around simply shows how little science is actually being discussed.  REAL scientists take this word *proven* very seriously...  

What you have here people is consensus science (Al Gore), not proof, and usually the consensus groups are very small.  Try to get a consensus among the world's stunt fliers on anything!!!  I dare you!!!

Finally, I tell you what, I will show my doctoral thesis on stunt design when you show me yours.  Even if you had one, it would just be one....waiting to be disproved by the next.

I don't think I'd settle for less than a "Triple Dog" dare, but I'd concur anyway on the unlikelihood of any sort of universal agreement.

>Even in the case of wind tunnel testing I REALLY DOUBT the conditions and speeds that
>we fly at have been tested by Boeing, NASA, Lockheed, etc.

Here I'll disagree some. While I don't think that exact conditions or any sort of comprehensive set of conditions for hemispherical flight can be duplicated and definitively handled, useful data for stunt-model design has been found and presented. I think the NACA researchers of the past have been underrated, along with current NASA folks too. In particular, on this thread is evidence that NACA did try to duplicate our conditions in a limited but very useful way. If there is a problem in disemination of information, it may well lie at least as much in reluctance to examine what is presented as in a shortage of research. Data on page one of this thread is an example. It answers the original query and then some, but has just sat there relatively unheeded, while people continued to discuss the topic.

There were some fine minds conscientiously working on problems we have, and while their data may be modest, it is also good. So I'll just say for this thread that NACA TR 586 ('Airfoil Section Characteristics as Affected by Variations of the Reynolds Number') and NACA TN 364 (deals with scale (RN) and turbulence affects on the actual NACA sections found in a large number of stunt models today) are relevant, although TN 364 was probably done before the full effects of tunnel wall interference were known. Even then, these guys tried their best to solve that problem and presented revised data later. Having read through a lot of this NACA/NASA literature, I have high respect for the people who researched and wrote it. One has to look for the material, but I have found it to explain a lot about the evolution of stunt and why certain things work the way they do so many years after the research was done. Newton's Laws need to be understood too.

"Pseudo science" is not what is practiced by serious science and engineering types; it is jargon thrown around by people who don't know the basics. The tools and language of science help handle complex ideas. They do not create the ideas, but rather make progress possible. Fortunately, we can enjoy this hobby with a pretty good margin of success, without much scientific background. Knowing real causes and dynamics helps make things right at the top end. I only see a problem with the spreading of misinformation, some of which is not even a matter of opinion; I lost count long ago of the mistaken attributions of causes to effects. The problem here, as elsewhere, though is intolerance.

So, before anyone gets paranoid about anything further here, this has not been aimed at any particular individual, even though it began with a response to Brad's quote. My "rules of engagement" from some years ago on the "other" forum included the caveat that whenever a disagreement includes  any statement about another party involved, there is a liklihood of unnecessary damage being done. I think we should lighten up a bit. There is really nothing wrong with kindness, regardless of how ridiculous you feel another person's behavior. Well, that's my "opinion" anyway. FWIW.

SK

There's lots of pertinent science extant.  It merely takes some effort.  Much of it is now available free on the Web, so it's easier than ever to acquire.  Serge's mention of page 1 of this report is a good example.  When I was in high school, my family moved to a town in Indiana where there wasn't much to do.  I was into combat, and I figured that if I could get a killer airfoil, I could do me some winning.  My reasoning was that good airfoils and bad airfoils weighed the same and took about the same effort to build, so a good airfoil would be "free".  There was a good library in town (Serge knows it well), so I went there and looked up aerodynamics.  That led me to the stacks in the back room where they kept the old NACA reports.  I found the airfoil plot from NACA TR 586, which Serge posted here on page 1.  That, plus one other NACA paper gave me the killer airfoil.  Without anything I learned in college, that airfoil gave me, a mediocre flier, the advantage I needed to win the Nats and make the US team twice. 

As for control line airplanes in wind, we discussed that on SSW.  I added a little to the explanation of flying in sideslip last night, including my guess at how Brad thinks of the effect of wind on stunt planes.  All you need (except for a couple of definitions) is in NACA Report 1098, http://naca.central.cranfield.ac.uk/reports/1952/naca-report-1098.pdf .  The ironic thing is that, rather than claim that science cannot explain the forces on a stunt plane flying in wind, a guy with no formal training could spend a couple of hours looking at that report and have a better understanding of the forces on a stunt plane flying in wind than 80% of aeronautical engineers.     

"All this "show me your data" stuff is just elitist bull.  Nobody has data."

There are the NACA report examples above. Here's another example just above.  Folks were discussing wing weight.  I wondered how wing surface area varied with thickness, so I calculated it.  With Excel, it took me 15 minutes, using no elitest math.  The answer I got was that it's a trivial amount.  In fact, I hardly believed how little it is.  I figured that somebody, particularly somebody who asserts that fatter wings are heavier, would spend a few minutes of his own doing a calculation to refute mine.  Nope, too much work. 

Did you just "prove" what I said?  I think so... thanks.

You said the answer was trivial in the case of the surface area...comparing what two airfoils?  A Strega and a Smoothie?  Did you count the added finish weight which also a function of surface area?  Fully sheeted?  Partially sheeted?

Of course, surface area is only one consideration in the discussion.  Yes, indeed one can *compensate* in the construction of fat winged models so that the weights are comparable to thinner winged models, but it inherently obvious that a larger structure, all things being equal, will weigh more than a smaller structure.  Heck the music wire that suspends the bell crank is longer on a fatter wing...  there is one weight gain right there.

Then their are the other compensations that must be made in the model to accommodate a big fat airfoil.  Typically, the fuselage has to be taller to accommodate the fatter wing (this is doubly true in the case of requiring clearance for a tuned pipe--which when I believe all that *beneficial side area* came into vogue).

If you feel these are all acceptable weight gains, then fine.  It does not change the facts that in every apples to apples comparison larger=heavier.

I cannot even believe this is even up for debate.

PS:  My "elitist" comment was made in regards to the attitude that there are some who feel their logic is just a little bit better than everyone else's logic.  I have no problem with using science as much as possible. 

There is a wealth of material out there about thicker wings allowing lighter structure to accomodate equal loads.

I never said otherwise. 

Of course, what "loads" are required?

In the case of the foam wing, very little cane be done to reduce the weight of the wing.  Most foam cores are cored to the same thickness, and the sheeting is the same.  I would not hazard a guess at how strong a foam wing really is compared to in flight loads that are actually required.  Probably serious over kill.

I never said that thicker wings cannot be built light.

Assuming that it applies to model airplanes, one could calculate the incremental weight of that bellcrank axle.  Steel is about .283 lb./cubic inch.  For a 12" chord, the difference between the 15% and the 18% wing, assuming the bellcrank axle is at the max thickness, is .03 * 12  inches * Pi * .0625^2 sq. inches * .283 lb./cubic inch. * 454 gm. / lb. = .57 gram.  You might want to go to a thicker axle because of the increased stress, but the lighter, thicker wing might let you get away with a thinner one.  Which would it be?

The .094% increase in weight for the surface of the 18%-thick wing relative to the 15% wing still looks suspicious to me, but I'm safe, because nobody will ever check it.

Ironically, my structures advisor is flabbergasted that I don't weigh every component of my airplane as I'm building it.  Heck, it weighs what it weighs.  The last one came out OK.  I did break down and weigh before and after the fancy clearcoat to see if the plane could tolerate another toot of it.
 

Geez, I just finally tossed my ancient CE233 "Strength and Materials" text.. And to think, there was a probably a wealth of good information pertinent to model airplane structure in there!

I kept my Statics and Dynamics texts (also ~40 years old), however, just in case I had to discuss distributed loads on a beam or design a bridge or something. I remember those (sophomore ME) classes, they were easy and fun.

(I also tossed my Thermo book - I hated that class, and despised steam tables or anything related to them. Only the Carnot Cycle seems to have any lasting value to me..)

((Yes, most of that NACA material is approaching 60 years old, but that doesn't mean it has no value..))

Steer me to a thesis on CL Stunt airfoil design.

L.

"My experience is that as soon as people are old enough to know better, they don't
know anything at all." -Oscar Wilde

>((Yes, most of that NACA material is approaching 60 years old, but that doesn't mean it has no value..))

Ah, old air too? Sometimes I think our (sometimes) wry humor bemuses even ourselves!

A bit of whimsy suggested by Larry's observation... I remember reading in John Paulos' book, Innumeracy - Mathematical Illiteracy and Its Consequences , his simplified computation of the probability that one is presently inhaling an air molecule exhaled by Julius Caesar with his dying breath. His conclusion, based on thorough mixing of all air molecules over the intervening millenia, was that the probability exceeded 99%.

...So a couple of these molecules, long ago expelled from the Langley wind tunnel, meet up somewhere over Muncie some summer, and one says to the other, "Oh-oh, here we go again! 'another of those d**ned NACA 0018's headed this way - all painted up and shiny, with strings attached!"

Hmmmmf. 'just a ...thought.

SK

Just an additional note to Howard's posted URL's:

The index on Martin Hepperle's site includes control-line topics not otherwise listed, including a derivation for approximate wing asymmetry due to air-speed variance across the span, as well as prop moments of inertia and gyroscopic precession, among various interesting technical topics. I think all his low-RN airfoils are for soaring, FW's, and racing though.

SK

Is there a formula for calculating the total surface area of a wing in there somewhere? I was looking over on Nasa.gov today and didn't find anything...

Steve-

I haven't looked for one, but I think you'd come close enough if you just measured along the outline of your preferred wing section with a flexible rule or marked strip of paper, took the ratio of that measurement to the chord, and multiplied it by the computed wing area.

Otherwise, I think it would be kind of a complicated calculus problem or perhaps something for a CAD program to do, since wing sections differ and have lengthy mathematical definitions. Whatever you might find would be limited to specific sections or "How-to's". Maybe there's a formularized approximation, but there really can't be a generalized exact formula.

SK

What I did was to take the NACA formula, calculate the ordinate for a thousand points with Excel, then add up the straight line distances between each of the points.  Pretty crude.

Pretty neat! Sort of the poor man's integration again.

SK

AAAGGGGHHHH.....

Don't even ask me why but....My favorite airfoil is 20-21% with about 1/2 to 5/8" leading edge radius.

It just seems to me that the overall performance is good enough in all conditions.  Kinda like what Dave
Fitz was looking for.........out!

Jim Pollock

Stunt guys have ballast boxes at the right wingtip.  They pick an asymmetry, add a bunch of ballast, then remove ballast until it comes out right.

Did you notice the Son of Snort wings?  They're a result of that kind of calculation.  The left tip chord is 3/4" more than the right tip chord.  That and the 2-degree skew in the leading edge kinda cause vertigo when you look at it.   

That is a generous offer, up upon which I have taken Gary.  I asked him to run a plethora of flap positions.  Although I have a history of abusing Gary's generosity, I didn't want him to spend a lot of time at work with his laptop screen up in front of him, so I wrote an Excel spreadsheet that calculates upper and lower surfaces as a function of flap deflection.  If that format works for Gary, I can send the Excel file as a template to anybody wanting Gary to analyze his airfoil.  I'll also explain the laptop joke and include a Reynolds number calculator.    

You sound like Ted Fancher.  What is "too much lift"? 

So bottom line I would not worry about the  tiny amount of extra weight in a really thick wing but the added drag would be my major concern.

Back to the weight issue, why would a thick wing be heavier than a thin one? 

Back to the weight issue, why would a thick wing be heavier than a thin one? 

Hi Howard

You will notice I said a tiny amount of weight differance...however if i build a wing say 1 inch thick and the same size wing 3 inches thick I willl need a longer metal rod for my BC mount, this will add weight, I also will need more material to glass and epoxy the center section, this will weigh more etc..

However as I stated the tiny amount of weight is not worth talking about

Regards
Randy

You sound like Ted Fancher.  What is "too much lift"? 

While I am sure Ted said it, look at the wing David is now using combined with absurd power. For years we have had tons of adequate lift with coupled flaps....and not enough controlled power despite some feather weights on the flight line. "To much lift" is the opposite of "not enough"! I used all Teds published data, Al Rabes stuff, Gialdini etc. and turned up with an airfoil that was just a dandy drag wagon for a conventional 60 but was hard to get to track with a piped 61. Sure, smaller flaps/throw, but the problem pointed to excess lift and inability to lock in during hard corners and oddly round shapes suffered as the CG moved back despite a good sized stab. The proof resides at David's house.

Hmmm ... my native language is Slovak, but I would say that opposite of "not enough lift" is "enough lift" and that is what I think is happening here. I did excel analyze of model and what I found, is, that what we need is the airfoil which gives "enough" lift. Anything more than that "enough" is not useful (means it cannot bring anything positive, because we cannot employ it).

I remember this thing years ago on compuserve.

Centrifugal force (quadrate of speed) needs some amount of lift coefficient (also related to quadrate of speed).

Both thin airfoil and also thick airfoil (to some extent) gives lift coefficient which grows 0.11 per 1 deg AoA. The difference is where this linear part of polar stops (where is critical AoA). So what we really need is the airfoil which will cover all our needs in that linear part of polar. Anything over is not important.

So what we really need is simple. The airfoil must:
- make enough lift in linear part of polar
- that part of the polar must be smooth in drag and in moment polars (without bumps, stairs etc)
- and that all must be true in all used angles of flaps deflection

I would say that any statement “too much lift” is related to improper flap/elevator ratio or too low wing load leading to improper (too low) AoA during the corner.