Leading edge sweep

[Paul Walker]

Howard,
What you're forgetting is that 98% of the people on this forum have no idea what the Hell you are talking about and don't understand anything you have said...but did get the jist of what Keith ment by Yaw...  I definitely do not agree with his conclusion but did understand what he meant.  But then I probably know him a little better than you do and talk to him more often.

I would never try to explain it to you!

Bottom line is don't be such a bully you'll get your point across jbetter if you simply realize you are talking to intelligent people who don't understand your language...you have to speak in theirs if you want them to understand...if you can't do that it simply means you're a good engineer and a lousy reference for normal folks!

Peace!

Randy Cuberly

Bully you call Howard....


You better go back and read what you have written.

Sad.

[Howard Rush]

Do you really really think wing LE sweep back is bad?  I was going to ask you then, why do you build your CLPA airplanes with swept back LE edges?  But then, I guess you sort of answered that conventional wisdom (whatever that is, like - where is this conventional wisdom?) sort of says that it is better than say having "way-swept-forward flaps".

I don't think of LE sweep as an independent variable.   Data I've seen such as in NACA Report 1098 are given as functions of quarter-chord sweep and taper.  I think sweep is bad because of rolling moment due to sideslip.  The more sweep a plane has, the bigger the tendency to roll changes as maneuver placement relative to the wind changes.  There are other design considerations that outweigh this, so the optimal stunt plane probably has some sweep.  There's the flap problem.  To make rolling moment due to sideslip go away, flaps would need to be swept forward 30 degrees or so.  I haven't found any data on the aerodynamic effect of way-swept-forward flaps, nor do I know how to calculate it.  I just intuitively think it would be bad.  I have intended to make a plane like that to find out for 35 years.  It will have to wait another few months, at least.  Another disadvantage of swept forward wings is that the nose gets long, as Dick said above.  In 1983 I switched from a straight LE to a straight quarter chord on my F2D planes to shorten the motor mounts.  It seemed to be a good trade, but in retrospect I should have lightened the tail.  Of course, the issue of sweep effect maneuver placement relative to the wind will be moot when we can use 2.4 GHz radios to shift ballast.

Where's the conventional wisdom?  One sees few airplanes on Saturday at the Nats with 30 degrees forward sweep in the flap hinge line.  

Another reason is that a tapered wing is closer to a more optimal elliptical wing planform without the fabrication difficulties of building an elliptical wing.  The tapered wing comes closer to giving elliptical lift distribution across the wing than a straight wing working on the premise that elliptical lift distribution is good because tip losses are minimized and drag is reduced.  (I have my own thoughts about elliptical wings on CLPA models, but I will not get into that here.)

Good point.  I forgot about that one.  To cancel that disadvantage, you'd need to bump up the aspect ratio of the rectangular wing a little, which would add even more structural weight.  I look forward to hearing your elliptical thoughts.  Elliptical wings look so cool.

And as has been suggested here, some may feel that a tapered wing (which sort of results in LE sweep) is more attractive.  So, go for what looks good.

The rectangular wing looks more attractive to Dennis.  He should be able to make up for its structural weight penalty with originality points.

... equal moments...

You're messing with me, aren't you, Col.?

Howard, I am not trying to argue with you, nor am I going to get into the discussion about whatever is the difference between side slip and yaw.

Sorry, Keith.  I was on a tear about language abuse, and yours was the first target I came to.  

[Derek Barry]

Bully you call Howard....


You better go back and read what you have written.

Sad.

A bully he is, on backwards he said my canopy was.

Derek

[Kim Doherty]

Just for some perspective from the full size world, I have some significant time in the LET Blanik L13 which has swept forward leading and trailing edges. One of the most well connected, well balanced planes I have ever flown. A pleasure to fly aerobatics in. (well, at least till the wing spar AD      )

Kim

[Serge_Krauss]

Marske Pioneer III - 42:1, so far?

[proparc]

Bully you call Howard....


You better go back and read what you have written.

Sad.

Some of Howard's Jive Combat Team rhymes, can be pretty intimidating!!

[Ted Fancher]

Right. Igor. I agree with you. I didn't think your discussion focused on whether or not leading edge sweep back was of benefit in CL Stunt airplanes.

I don't know why you would conclude that a reduction in body roll is of benefit to the less skilled flier, not so to the more skilled flier. In any case, I think we can agree that a flier who edges close to top five is of above average skill. Within a hair of demonstrable top 5 skill. I am talking of Dan Banjok and his Vista. A near straight leading edge plane. Total sweep back of 1/2" from center to tip. Miniscule on a 60" span thick airfoil model. I am interested in knowing whether anyone made a systematic comparison of the performance of sweep back vs non-sweep back models flying at typical stunt speeds. Side note: combat planes that need to be aimed accurately and are flown in all kinds of wind conditions, use straight leading edge wings.

Hi Dennis,

FWIW, Bob Hunt once judged a flight of my Johnson "little s" powered Chief at a VSC and told me years later it was one of the better flights he had ever judged.  Nothing much straighter than a Veco Chief leading edge!

My Imitation was the best airplane I ever designed to fly well easily and it had the least taper of any of my designs (save the very straight winged Doctor/Medic EMT designs).  None of my "competition ships" had so little taper because it looked ugly.  Didn't say I was smart, did I!!!

Ted

[Igor Burger]

The more sweep a plane has, the bigger the tendency to roll changes as maneuver placement relative to the wind changes.

I am not sure, but I remember some text or may be NACA report showing several properties of yawed wing with sweepback (pressure distribution, CP position, bending moment etc ...). I think somewhere in conclussion was written that sideslip does not make expected sidewise shift of centre of pressure. Additionally we are flying circular path, it can also change situation as the effective span make speed differences on tips lower. It will be nice to make some simulation and find real center of pressure with reaspect of side wind on circular path.

The effect of side slip also varies with angle of attack. 

[Mike Keville]

...Bob Hunt once judged a flight of my Johnson "little s" powered Chief at a VSC and told me years later it was one of the better flights he had ever judged... 
Ted

==============================================================

I saw that flight.  Bob wasn't kidding.  It was textbook.

[Igor Burger]

Just for some perspective from the full size world, I have some significant time in the LET Blanik L13 which has swept forward leading and trailing edges. One of the most well connected, well balanced planes I have ever flown. A pleasure to fly aerobatics in. (well, at least till the wing spar AD      )

Kim

Nice to see our airplane in our newsletter comming from Canada :- ))

[Ted Fancher]

My first recolletion of the terms "Moments" as generally (OK, erroneously) applied to CL Stunt aircraft came from the MAN atricle that accompanied George Aldrich's Nobler article.  The distances from the engine thrust washer to the leading edge of the wing at the root, was described (erroneously) as the "nose Moment".  The distance from the flap hinge line to the elevator was described (erroronously) as the "tail moment".  I recall a diagram with dimensions describing those parameters.

I think these terms simply stuck in the CL Stunt community.  It's entirely possible that George got them from somewhere else (erroneously).

At any rate, I would say that while they certainly are not engineering discriptions, they have been adopted to actually mean some specified linear dimensions that, while not used in any meaningful aerodynamic calculations, can certainly be used to describe a particular general arrangement of the physical elements of a CL stunt aircraft.

As such they do have a generalized purpose that has come to mean something in the Stunt community, and therefore any criticism aimed at their use simply means that the folks leveling the criticism are being "Prudish" technocrats that actually do know what is meant by their usage in general terms but insist on trying to show everyone else that they are too smart to acknowledge that changes,or additions, in general terminology do and can coexist with numerically generated engineering reality.

Besides, sometimes the real engineering terms don't do much better at describing the actual physical function of the surrounding world except in numbers (sometimes erroneously).  Especially since they are understood only by a very small portion of the population.

I've learned to just smile and accept reality.  After all, the ultimate level of education is Philosophy is it not?  Isn't that why they call it PhD.  

Randy Cuberly  

Bravo, Randy.

My definition of a valuable post is that somebody can read it in English he understands and employ the information in a positive manner to improve his performance at the flying field.  Snarky criticism in and of itself seldom fulfills that standard.

I agree, it can't hurt any of us to learn more precisely accurate descriptions/definitions, etc. of aerodynamic subjects but, it is my belief, that any attempt to point out the technical fallacies of a given post should include helpful commentary to not only illuminate the fault but to advise what is accurate and what the enhanced effects might be at the flying field from employing the technically esoteric but precise terminology as opposed to the apocryphal language of the lay pilot.

Ted

[Ted Fancher]

I have to agree  with Howard here,
I visit several photography sites,, its a real crapshoot to communicate because people dont use the proper terms for things
so when you respond you never know whether they are refering to the real definition, or the one they imagine it to be

words have specific meanings,, to communicate you must use the words that refer to the proper topic,,or risk confusion
its like stating the wing percentage thickness is it with or without flaps,,
stating the tail "moment" (sic),, is it from the CG or the flap hingeline,,

Mark,

Although your points are well taken, taken literally they pretty much eliminate everyone from participation on the forums besides Howard, Igor, Brett, Serge and maybe a couple of others. 

While if, like Brett, they can do so in language decipherable to the non-cognoscenti, such a site might be more valuable from a precision standpoint it would also be pretty much a bore since--without the foolish commentary which generates the high brow responses--there wouldn't be much to read.  Almost all of the wisdom which arises in these threads is the result of responses to the "foolish" input from people who just like to be involved in the discussion.  Without those triggers I wonder how many threads there would be in our treasured fora?

I just don't like "snark".  I much prefer information that helps the now foolish become less so.  Anybody that hasn't seen the improvement in the "average" stunt flier since the advent of the forums just hasn't been paying attention...to say nothing about those way above average types that are currently kicking some pretty serious "good old boy butt" of late.

Ted

[Howard Rush]

My definition of a valuable post is that somebody can read it in English he understands and employ the information in a positive manner to improve his performance at the flying field.  Snarky criticism in and of itself seldom fulfills that standard.

I agree, it can't hurt any of us to learn more precisely accurate descriptions/definitions, etc. of aerodynamic subjects but, it is my belief, that any attempt to point out the technical fallacies of a given post should include helpful commentary to not only illuminate the fault but to advise what is accurate and what the enhanced effects might be at the flying field from employing the technically esoteric but precise terminology as opposed to the apocryphal language of the lay pilot.

I have read a lot of expert advice on these fora that I flat out don't understand.  For example, I never learned what stunt people mean by "power", nor if they all mean the same thing.  I only knew they didn't mean power.  What if the writer and reader don't have the same private definition?  There is no place the reader can look it up.  In such a case, no, I can't include helpful commentary, because I don't know what's being said.  You think I should just shut up, but I figure if a guy with more background in flight mechanics than the usual reader can't make heads nor tails about some flight mechanics advice from an expert stunter, he might do a service to his fellow readers by saying, "Huh?".  I don't think I'm the only person who doesn't understand.   We agree that it's best to use language decipherable to the non-cognoscenti.  Instead of "lift", it's better to say "force perpendicular to the flight direction" or even something wordier if you need to be more precise.  We evidently disagree whether it's OK to use a technical term not to mean its standard definition, but to mean something we're guessing that the reader thinks is its definition.  If the reader has a different definition than you're guessing, or if he looks the term up in a book or on the Internet, he won't understand what you mean.  If one uses a technical term, it's easy enough to look it up to see if it's what he thinks it is.  Heck, I just looked up "cognoscenti".

Also, I don't think that all these posts should have to be universally accessible.  I have learned a bunch from Igor, Frank Williams, etc. here, talking cognoscenti talk.  Sparky thinks we should take such vile language to the Engineering board, which is OK with me.

Meanwhile, I could be nicer, but it's against my nature.

Snarker in Chief

[Curare]

Mark,

Although your points are well taken, taken literally they pretty much eliminate everyone from participation on the forums besides Howard, Igor, Brett, Serge and maybe a couple of others. 

While if, like Brett, they can do so in language decipherable to the non-cognoscenti, such a site might be more valuable from a precision standpoint it would also be pretty much a bore since--without the foolish commentary which generates the high brow responses--there wouldn't be much to read.  Almost all of the wisdom which arises in these threads is the result of responses to the "foolish" input from people who just like to be involved in the discussion.  Without those triggers I wonder how many threads there would be in our treasured fora?

I just don't like "snark".  I much prefer information that helps the now foolish become less so.  Anybody that hasn't seen the improvement in the "average" stunt flier since the advent of the forums just hasn't been paying attention...to say nothing about those way above average types that are currently kicking some pretty serious "good old boy butt" of late.

Ted

I followed you up to 'non-cognoscenti', but I didn't know what you meant. So I stopped listening. 

[Howard Rush]

I am not sure, but I remember some text or may be NACA report showing several properties of yawed wing with sweepback (pressure distribution, CP position, bending moment etc ...). I think somewhere in conclussion was written that sideslip does not make expected sidewise shift of centre of pressure. Additionally we are flying circular path, it can also change situation as the effective span make speed differences on tips lower. It will be nice to make some simulation and find real center of pressure with reaspect of side wind on circular path.

I just looked at the ancient NACA Report 1098 that I keep referencing, and indeed that's what it says.  The authors recommend that those data be used only to extrapolate from characteristics of airplanes for which there's wind tunnel data, and that they give the largest change to be expected.  I have done some experiments with combat planes.  The sweep effect exists, but I haven't quantified it.

The effect of side slip also varies with angle of attack.  

The 1098 data show it as proportional to angle of attack.  So on a windy day, flying a great circle path on the upwind side of the circle is probably safe, but you might not want to do either inside or outside loops upwind.  

[Paul Walker]

Howard.  Help!

On my new plane I lengthened the nose moment, added power, and now it doesn't track good.

Now what do I do?

[Trostle]

Good point.  I forgot about that one.  To cancel that disadvantage, you'd need to bump up the aspect ratio of the rectangular wing a little, which would add even more structural weight.  I look forward to hearing your elliptical thoughts.  Elliptical wings look so cool.

You're messing with me, aren't you, Col.?

Hi Howard,

Regarding the first point above, we are talking about stunt ships with elliptical wings.  I agree.  Elliptical wings do look good.  Years ago, I had a series of these things and I had some of my initial successes in competition with them.  I definitely have some thoughts about them regarding CLPA.  (There are photos from the 60's recently posted in another section of this forum but since this is a thread on LE sweep, there is no need to post them here.)  This can be a subject we can discuss some quiet evening coming up in August.  (I tried to get on that same airplane with you out of Chicago.)  I also have some comments about stunt ships with "higher" aspect ratios than usually seen on our CLPA airplanes, something else outside the scope of this thread.  I also have comments about stunt ships with wings with more sweep back than usually seen out our CLPA airplanes, something else outside the scope of this thread.

Now the other comment was in regard to my term "equal moments".  Given the technocratic perfection of this thread, I guess I should have known better than to use that term when I was trying describe a hypothetical pair of CLPA models that only differed in taper ratio.  They were to have equal spans, equal weights, equal wing areas, equal tail areas, same power plants, and same trim for flying the best pattern (if that can be achieved).  AND, they were to have equal nose lengths (measured from "some technically acceptable reference point on the wing to the nose) and equal tail lengths (measured from "some technically acceptable reference point on the wing to another acceptable reference point with respect to the horizontal tail).  I carelessly called out that this otherwise identical pair of CLPA models except for taper ratio would have equal moments.  (Also, to save you the bother of pointing out that there could not really be such a pair of "identical stunt models except for taper ratio", I am fully aware that the differences in airfoil percentages  because of the differences in the root chords and differences in the tip chords cannot be fully accounted for as being "identical".  So forgive me for not being as descriptive as I should have been when I called for "equal moments".  But my "opinion", not based on any hard data, is that the CLPA airplane with a "typical" taper ratio found on our stunt models (say around 0.7) will perform the CLPA pattern better than the otherwise similar CLPA model with no taper.  At least, it has been my experience that it is easier for me to fly a better pattern with that.

Keith

[Tim Wescott]

I followed you up to 'non-cognoscenti', but I didn't know what you meant. So I stopped listening. 

Cognoscenti?  I thought this thread was about aerodynamics, not sniffing gears!

[Dennis Moritz]

Hi Ted,

Yeah. I think Dan's plane flies pretty well. The Vista. Even looked good a few years back. We dig the the thirties pylon racers. Most of them had rectangular wings with Carl Goldberg looking Buster tips. Looks good to us. A Brown B2 with swept back leading edge. Ugh.

[Paul Walker]

Hi Dennis,

FWIW, Bob Hunt once judged a flight of my Johnson "little s" powered Chief at a VSC and told me years later it was one of the better flights he had ever judged.  Nothing much straighter than a Veco Chief leading edge!

My Imitation was the best airplane I ever designed to fly well easily and it had the least taper of any of my designs (save the very straight winged Doctor/Medic EMT designs).  None of my "competition ships" had so little taper because it looked ugly.  Didn't say I was smart, did I!!!

Ted

Based on this input, I just measured my Skylark I used at VSC last year. It has a 1/4 chord that sweeps aft 0.8 degrees. That's not much, and it flies well.

[Igor Burger]

I just looked at the ancient NACA Report 1098 that I keep referencing, and indeed that's what it says.  The authors recommend that those data be used only to extrapolate from characteristics of airplanes for which there's wind tunnel data, and that they give the largest change to be expected.  I have done some experiments with combat planes.  The sweep effect exists, but I haven't quantified it.

The 1098 data show it as proportional to angle of attack.  So on a windy day, flying a great circle path on the upwind side of the circle is probably safe, but you might not want to do either inside or outside loops upwind.  

OK, I found it after all, now I read it and I see it is not so consistent for example CP does not move sidewise but rolling koefficient is positive ... probably needs more reading ... may be later

http://naca.central.cranfield.ac.uk/reports/1955/naca-rm-l54k15.pdf

Yes I understand what you mean and I agree it should be so, but that report says something else, that is what I wanted to point out

[Igor Burger]

Howard.  Help!

On my new plane I lengthened the nose moment, added power, and now it doesn't track good.

Now what do I do?

Now, when I read this thread, I learned you need more lift ...

[Ted Fancher]

I followed you up to 'non-cognoscenti', but I didn't know what you meant. So I stopped listening. 

Sorry, Curare.  One of my lifelong pleasures has been looking up interesting sounding words I don't know the first time I see/hear them and afterwards often try to use them appropriately when the occasion arises.  Sort of a hobby, like building stunt ships.  Most of the world finds stunt boring as well and also looks the other way when they see grown men playing with their funny looking toys (unless, of course, the toys are built by companies with fancy names like Apple,  Callaway or Porsche, that is! )

Ted

p.s.  Cognoscenti are "people in the know" on some, often arcane, subject.  With the "non" attached to it, of course, the implication is the reverse...sort of the condition into which this thread has devolved.   My actual thought was that, without those whose knowledge base is empirical (based on, concerned with, or verifiable by observation or experience rather than theory or pure logic[per a Google search])  rather than book l'arnin', Sparky's pages would be pretty barren.  It is their empirical (if technically flawed) observations that drag the Cognoscenti off their lofty perches to enhance the the manner in which the empirically trained refine their understanding and, ultimately, improve the manner in which they inform others.  Sort of a classic win, win arrangement.

[Ted Fancher]

I have read a lot of expert advice on these fora that I flat out don't understand.  For example, I never learned what stunt people mean by "power", nor if they all mean the same thing.  I only knew they didn't mean power.  What if the writer and reader don't have the same private definition?  There is no place the reader can look it up.  In such a case, no, I can't include helpful commentary, because I don't know what's being said.  You think I should just shut up, but I figure if a guy with more background in flight mechanics than the usual reader can't make heads nor tails about some flight mechanics advice from an expert stunter, he might do a service to his fellow readers by saying, "Huh?".  I don't think I'm the only person who doesn't understand.   We agree that it's best to use language decipherable to the non-cognoscenti.  Instead of "lift", it's better to say "force perpendicular to the flight direction" or even something wordier if you need to be more precise.  We evidently disagree whether it's OK to use a technical term not to mean its standard definition, but to mean something we're guessing that the reader thinks is its definition.  If the reader has a different definition than you're guessing, or if he looks the term up in a book or on the Internet, he won't understand what you mean.  If one uses a technical term, it's easy enough to look it up to see if it's what he thinks it is.  Heck, I just looked up "cognoscenti".

Also, I don't think that all these posts should have to be universally accessible.  I have learned a bunch from Igor, Frank Williams, etc. here, talking cognoscenti talk.  Sparky thinks we should take such vile language to the Engineering board, which is OK with me.

Meanwhile, I could be nicer, but it's against my nature.

Snarker in Chief

Howard,

No way do I think you should shut up.  You and a few others bring informed expertise that is bullion for those who would excel at things aerodynamic. 

Which is exactly why you should write informative articles on the subjects which would inform rather than inflame those who share your passion for model aircraft but lack your excellent technical background.  If you were to do so, however, I would encourage that you utilize language which those who could value from your contributions can understand and recognize that, at the average age of those readers, are unlikely to be willing to go back to school for five or six years to learn the prerequisites for understanding at the level with which you are prone to inform.  Tough to do but not as destructive to the common weal as belittling competent modelers whose real world expertise hasn't been devoted to the subject they find of interest--yet who like to opine on their empirically learned wisdom.  More or less the idea behind special interest web sites

Your thought of a devoted board hosted by and restricted to commentary from the people you mention would be an excellent way to go about providing that information.  I bet Sparky could be talked into providing the access and necessary band width or whatever it takes.  It would also put all of the valuable information in a single location which would simplify access to those who truly want to understand how these things work.  I encourage you to initiate discussions that would turn your idea into reality. 

You might want to include an "in only" mail box for readers to ask questions from which you could choose the subject matter for each resulting commentary.  When I wrote the (most likely incorrect) column for Model Aviation for four or five years questions from readers were my primary source for subject matter.  Might be equally valuable for your Expert Panel.

Ted

[Serge_Krauss]

I have to look up "snarky".

Having read all the criticism and pseudo criticism last night, I spent a couple hours typing a post to meet the criteria requested. I defined key terms in this thread, pointing out those that are misused and the mistakes to which they lead. I stated why they were necessary to understanding. I then stated precisely as I could what was relevant to stunt design and trimming and their relation to sweep. I did not post for the following reasons:

1) I realized I'd already posted this information before.

2) It was too long.

3) I just didn't give a darn anymore after reading all the flack above.

SK

[RandySmith]

 " Quote from: Paul Walker on February 25, 2014, 09:33:37 PM
Howard.  Help!

On my new plane I lengthened the nose moment, added power, and now it doesn't track good.

Now what do I do?

Now, when I read this thread, I learned you need more lift ... Devil  "


LOL  I thought that more practice was in order !!   :-)

[Gerald Arana]

Serge,

Snarky: "Testy or irritable" according to my Websters Unabridged Dictionary. 

PS: I don't know about the rest of the readers but I'm "IMAO" at this column. And I'm learning something (what I don't know) about airplanes..............No, people!

Jerry A.

[Dennis Moritz]

looks right flies right

[Ted Fancher]

Based on this input, I just measured my Skylark I used at VSC last year. It has a 1/4 chord that sweeps aft 0.8 degrees. That's not much, and it flies well.

Hi Paul,

I expect that was a "needle"...to which my only mea culpa excuse would be that Dennis was asking only if stunt ships with essentially constant chord (non-swept leading edges per the original subject of the thread) could not be competitive with their more aesthetically pleasing cousins.  To which I provided examples of very good flying airplanes that didn't conform to the swept leading edge norm.  My way of saying heck yes they can be competitive.

Here I tend to agree with Howard.  I think tapered and/or swept back leading edges are ubiquitous simply because, to the vast majority of us, they look better.  Oh, another good flying essentially constant chord airplane was Bob Emmett's Howard Ike which is, like the airplane's Dennis favors, a classic Gee Bee era racer.

Ted

p.s.  Yes the Skylark flew well.  My best guess is that it would only take .02 degrees less sweep to optimize its response rate as biased by Coriolis force, thus allowing maneuvering flight at greater than 4 seconds per lap .

[Paul Walker]

Hi Paul,

I expect that was a "needle"...to which my only mea culpa excuse would be that Dennis was asking only if stunt ships with essentially constant chord (non-swept leading edges per the original subject of the thread) could not be competitive with their more aesthetically pleasing cousins.  To which I provided examples of very good flying airplanes that didn't conform to the swept leading edge norm.  My way of saying heck yes they can be competitive.

Here I tend to agree with Howard.  I think tapered and/or swept back leading edges are ubiquitous simply because, to the vast majority of us, they look better.  Oh, another good flying essentially constant chord airplane was Bob Emmett's Howard Ike which is, like the airplane's Dennis favors, a classic Gee Bee era racer.

Ted

p.s.  Yes the Skylark flew well.  My best guess is that it would only take .02 degrees less sweep to optimize its response rate as biased by Coriolis force, thus allowing maneuvering flight at greater than 4 seconds per lap .

Roger that Captain!

Gee, I thought classic planes were supposed to fly fast. Dang, another thing I got wrong!

[Trostle]

p.s.  Yes the Skylark flew well.  My best guess is that it would only take .02 degrees less sweep to optimize its response rate as biased by Coriolis force, thus allowing maneuvering flight at greater than 4 seconds per lap .

Well now, we need to better understand the impact of the polar vortex coupled with the variables created by electric motors and all of those pesky electrons that envelop the model when being driven by either left hand or right hand props.  It really becomes necessary to optimize LE sweep-back and to tailor that with the LE radius of the horizontal stabilizer.  Maybe deBolt was on to something with his 80 mph Stunt Wagon with its short "moments".

Keith

[Dick Pacini]

I was going to post again but had a senior "moment" and forgot what I was going to say.

[Curare]

Ted I was with you all the way, but I was indulging one of my hobbies, which is making asinine groanworthy jokes to lighten the mood.

As a bit a layman, I can tell you that discussions on this board occasionally stray from my realm of knowledge, but if that happens, I only have to do some googling and I can find enough information to peice together the crux of the argument.

As an engineer it does make things difficult if the nomenclature used is incorrect or misleading.

[Ted Fancher]

Ted I was with you all the way, but I was indulging one of my hobbies, which is making asinine groanworthy jokes to lighten the mood.

As a bit a layman, I can tell you that discussions on this board occasionally stray from my realm of knowledge, but if that happens, I only have to do some googling and I can find enough information to peice together the crux of the argument.

As an engineer it does make things difficult if the nomenclature used is incorrect or misleading.

Curare,

No worries.  Your point (and Howard's) is well taken but the underlying problem is pretty much irreparable. 

The problem arises due to the unintended but no less effective development of an "arcane"  language among the handful of stunt devotees around the world who, over a period of 70 or so years, have used certain words in a consistent fashion, notwithstanding their meaning in the language used by others (engineers, for instance) that has become accepted and understood by the "tribe".  That these meanings differ from the meanings ascribed by other tribes is pretty much irrelevant (a huge percentage of words in the nominally "English" language have, over time, assumed a variety of meanings that must be understood via the context in which they are used.  Power, for instance is used to describe a force, a deity, coercion and, almost certainly others that don't come immediately to mind.  All meanings correct in their context.)

Just because stunt fliers are a small tribe doesn't make the words in their "language" wrong.  Their words mean nothing more than what the tribe knows them to mean.  It's not surprising that those whose mother tongue is different can find the stunt tribe's definitions irritating but it means nothing more than they aren't yet conversant in the tongue (or prefer not to speak the language which is, of course, their right).

In stunt, IMHO, it is important to note that George Aldrich, who wasn't to the best of my knowledge an aero engineer, pretty much wrote the code for the tribe with the Nobler 60 or so years ago and, despite subsequent language difficulties, not a great deal of importance has been divined since.  Every top stunt ship all these years later is pretty much a thinly disguised Nobler, whatever the pedigree of the "designer"...and I happily include myself among those who has poached on George's territory in print.

It hardly seems necessary to me to excoriate one another because we don't all speak the same language when those with the greatest speech impediments are often perfectly capable of beating the socks off of our Stunt Shakespeares.

Ted

*(Arcane definition: known or understood by very few; mysterious; secret; obscure; esoteric: She knew a lot about Sanskrit grammar and other arcane matters.)

[Ted Fancher]

Well now, we need to better understand the impact of the polar vortex coupled with the variables created by electric motors and all of those pesky electrons that envelop the model when being driven by either left hand or right hand props.  It really becomes necessary to optimize LE sweep-back and to tailor that with the LE radius of the horizontal stabilizer.  Maybe deBolt was on to something with his 80 mph Stunt Wagon with its short "moments".

Keith

Exactly, Kernel!  See you soon.

[Ted Fancher]

Cognoscenti?  I thought this thread was about aerodynamics, not sniffing gears!

Actually, Tim, Cognoscenti is an Italian wine.  A pink, I think.

Ted

p.s.  That's probably not true; although I don't speak Italian so who knows?

[Serge_Krauss]

Serge,

Snarky: "Testy or irritable" according to my Websters Unabridged Dictionary.  

PS: I don't know about the rest of the readers but I'm "IMAO" at this column. And I'm learning something (what I don't know) about airplanes..............No, people!

Jerry A.

Thanks for the def. I hadn't looked it up yet. You probably already know most of what there is to be learned about people here. Ha! Now that I've finished glassing my model with 45^o bias weave and epoxy and made the annual mess, I'll have time to work off the irritability in sanding,...and sanding,...and probably sanding. That's before I sand through something and fix it, but sometimes that doesn't happen ('didn't happen on a few occasions recently).

Well, I should get a little bit "on topic." So a remark: I think that a well-conceived and built plane with a "Hershey-bar" shaped wing can stunt just fine. However, as I and others have posted from time to time, there are advantages to tapered wings that often outweigh their disadvantages, especially as models increase in size. Keith covered at least two of them. Another tapered-wing advantage that is more or less epitomized by the elliptical wings is resistance to lateral gust upsets. Tapered wings also probably recover from yaw quicker and I think (Howard will correct me, I'm sure) have less yaw-roll couple. That means that I think that the tapered wing will roll less with a given yawing motion (Howard?).The strange thing about leading-edge sweep is that despite its drawbacks and those of any concomitant wing sweep, mentioned above, it does accomodate spanwise-straight trailing edges, which some reports I've read indicate increase the efficiency of given wings. If the designer can get past the elementary mistake of picking a.c.'s and/or c.g.'s from just looking at the root, there are interesting compromises possible. Also interesting - to me anyway - is that the calculation of MAC and a.c. for elliptical wings at any sweep is much easier than for straight tapered wings, although you can easily have the a.c. and MAC calculated at sites on line, as has been posted often. That's what I do.

SK

[Ted Fancher]

Roger that Captain!

Gee, I thought classic planes were supposed to fly fast. Dang, another thing I got wrong!

Don't get too down on yourself, Paul.  What the heck, you've gotten a few things right over the years.  Glad I could help you out on this one.

Ted

[Trostle]

"Moments"

Howard,

Now I am really lost.  Reference is made to the most recent issue of Model Aviation, , March 2014. page 126 for the "FF Sport" column.  There is a photo of a stick and tissue FF Scale model of the Vindicator.  Included in the caption is the statement "It has good wing area and MOMENTS..."  (Emphasis added.)

Gad, what on earth does that mean?  Surely, FF guys understand appropriate terminology used in aeronautics.

Keith

[Tim Wescott]

I dunno Keith.  I have my good moments, too.  Mostly on the practice field -- I'd like to have more of those good moments in official flights.

[Ted Fancher]

I dunno Keith.  I have my good moments, too.  Mostly on the practice field -- I'd like to have more of those good moments in official flights.

Tim,

Exactly my point!   
If every word had only one definition, Webster's voluminous volume would be a puny pamphlet.

Ted

[Tim Wescott]

Exactly my point!   
If every word had only one definition, Webster's voluminous volume would be a puny pamphlet.

Actually I think it'd be way bigger, and there'd have to be a "word inventor guy" in every community.

Either that or we wouldn't fly model airplanes -- we'd be flying "well they're not really birds but they're more like little toy wagons that fly through the air, y'know".

[Curare]

Hehehe, you'd be suprised how many languages call aircraft "flying things"

[Serge_Krauss]

...

[Tim Wescott]

Dang.  I look for an insightful post by one of the reliable model-techie types, and instead I find that some idiot has pulled the thread off topic.

[Curare]

[Mark Scarborough]

Mark,

Although your points are well taken, taken literally they pretty much eliminate everyone from participation on the forums besides Howard, Igor, Brett, Serge and maybe a couple of others. 

While if, like Brett, they can do so in language decipherable to the non-cognoscenti, such a site might be more valuable from a precision standpoint it would also be pretty much a bore since--without the foolish commentary which generates the high brow responses--there wouldn't be much to read.  Almost all of the wisdom which arises in these threads is the result of responses to the "foolish" input from people who just like to be involved in the discussion.  Without those triggers I wonder how many threads there would be in our treasured fora?

I just don't like "snark".  I much prefer information that helps the now foolish become less so.  Anybody that hasn't seen the improvement in the "average" stunt flier since the advent of the forums just hasn't been paying attention...to say nothing about those way above average types that are currently kicking some pretty serious "good old boy butt" of late.

Ted

Ted,
respectfully,, were people to take a few minutes to understand the accurate usage of the words a great deal of the "snarky" responses would be eliminated. Most come from the misuse rather than any inherent snarkyness of the writers.. I agree some people can describe things using "non technical " terms,, but usually it leaves more room for missinterpretation.

I dont see how using proper verbage would eliminate anyone from the discussion, it would allow more people to communicate since we are talking apples and apples,, If you call me to ask why your pictures are so dark, and I ask what aperture and shutter speed you are using,, and what your ISO setting is,, and you say,,k I push the button on the camera and it goes click, but the number is 60,,, how on earth can I help you,, relatedly,, ISO on a camera relates to the sensors gain ( light sensitivity) but in other worlds it means "in search of" so you do have to use the right terms in the right place,,

and as a gentle nudge, , your use of non-mainstream words of the 5 dollar variety could be taken in the same way using proper aero terms is,, IOW,, if ya dont know, look it up and enhance your knowledge.. I always enjoy reading your posts because most times there is a word that forces me to use google at least once,,
The same holds true for Igor, Howard and some others,, they discuss something and it forces me to use my brain to understand,,( and google) and that is a good thing..

[Dennis Moritz]

I like snarky. Like the old aftershave commercial. Whack whack wake up.

[Dennis Toth]

Sooo, getting back to sweep, it seems like we do this for looks and either way works. I'm ok with that because the "look" adds or detracts from the illusion of the maneuvers.

What about airfoil thickness tapper? If you are at 18% root thickness what happens aero wise if the tip is 20% or 10%? How far can you go? I had a wing that my uncle built in the 50's that was 2 1/4" at the root tapered to 3/8" at the tip. It looked cool but how would that work for todays designs?

Best,         DennisT

[Dave_Trible]

Dennis I built something like that as a teen but as a combat ship.  It turned like a demon due to the thick center section generating gads of lift but had little roll stability.  If not careful engine torque could try to roll it.  I learned then to keep the tips at least equal to, if not thicker by percentage than the root so that the tips don't stall first.  One must also be mindful of where the high point occurs by percentage in relation of root to tip.

Dave