Hinge-to-hinge distance

[Matt Piatkowski]

Hello,
I have collected some of the hinge lines distances in the C/L stunt models.
For example: one of the older designs (Tiger Shark) has 17.625", profile Berserker: 17.15", my own MPBee, made in 2018: 18.25", my own Big Red (Max Bee II, 2019) 18.875".

Original, ICE powered, Mace R-2 Shark from the Yatsenko Brothers has 18.50" and the electric versions of the same model have even larger hinge-to-hinge distances (up to 19").

My F2B colleagues in Poland, especially those flying the models with counter-rotating propellers, have this distance in 18-19" range, with the growing trend to increase it even further.

There must be some optimum for this distance. The magnitude of it is closely related to the size of the horizontal empennage, the wings air foil geometry and other parameters but there is no credible data to prove it.

I would like to initiate the discussion on this complex subject.

Stay Safe,
M

[Howard Rush]

Tail length has been one of my favorite subjects for the last 57 years. First, the parameter you are using, hinge-to-hinge distance is easy to measure, but is only useful if you're comparing airplanes that are the same otherwise, and if you aren't calculating anything.  A more useful measure is the distance between the quarter aerodynamic chords of the wing and tail: call it l_t.  For most purposes, one would compare  l_t / wing mean aerodynamic chord among different airplanes. Brett, as I recall, thinks that, for stunt planes, l_t by itself is of interest, because the maneuvers we fly are of fixed size, rather than proportional to mean aerodynamic chord. 

The longer the tail, the greater the maneuvering stability.  Igor explained that in his Stunt News article.  Long tails can cause pitch rate limiting, because the stabilizer operates at a perverse angle of attack.  There are other tail length effects, like being able to fit your airplane into a Tesla, but they are probably of lesser significance.

"Tail volume" [quotes used correctly] is something that's sorta useful, but it doesn't tell the whole story. F2B airplane flight characteristics are so refined now that it's too crude a measure.   
 

[Brett Buck]

Hello,
I have collected some of the hinge lines distances in the C/L stunt models.
For example: one of the older designs (Tiger Shark) has 17.625", profile Berserker: 17.15", my own MPBee, made in 2018: 18.25", my own Big Red (Max Bee II, 2019) 18.875".

Original, ICE powered, Mace R-2 Shark from the Yatsenko Brothers has 18.50" and the electric versions of the same model have even larger hinge-to-hinge distances (up to 19").

My F2B colleagues in Poland, especially those flying the models with counter-rotating propellers, have this distance in 18-19" range, with the growing trend to increase it even further.

There must be some optimum for this distance. The magnitude of it is closely related to the size of the horizontal empennage, the wings air foil geometry and other parameters but there is no credible data to prove it.

    Well, there is plenty of experimental evidence. There is no particularly sound analytical solution.

     As before, counter-rotating or not is *mostly* irrelevant, the one possibly relevant difference being that the gearbox or other mechanism increases the moment of inertia, which is part of the optimization between pitch acceleration (enhanced by longer tail/increased tail volume), and peak pitch rate (inhibited by the longer tail). Basically, the longer tail or more volume will give you more torque *to begin with*, starting from steady level flight or when switching directions, but it will fall off faster with pitch rate (as the angle of attack is reduced more quickly with rate).

     On one extreme would be the Ringmaster, which has such a short tail that you can very easily, in fact, almost always, drive the pitch rate so high that you stall the wing, sometimes uncontrollably. That's why it requires such slow control setup, do that, and it's merely a poor airplane, rather than a complete disaster as it is stock. The other ends of the spectrum were explored in the 90's with tail moments of some competitive models in the 20-22" range (hinge to hinge), which I think were too long for conventional systems. But even with them, probably, too long, the airplanes were certainly flyable and certainly won a fair number of contests.

    Making it longer makes the rapid transitions from straight to curved better, and also has the reverse-exponential effect that we find desirable - and any one who flew an Imitation back-to-back with a Nobler can tell you, and why the Imitation was such a breakthrough.   

    I think the optimum for conventional-sized models is around 18", but I wouldn't be concerned with it becoming uncompetitive until it got much longer, as long as you don't get into absurd noseweight to balance it.   With electric, and with a counter-rotation gearbox, that doesn't seem like a problem.

    I would note that what probably matters is the distance from the CG, not from the flap hinge line or the Cp, or anything like that And, that running the CG forward (as with electric, for whatever reason) makes it longer and give the tail more starting torque, and more rate falloff. Unfortunately that increases the negative pitching torque from the wing much faster than improving it from the tail, which is why it also makes the controls heavier

          You can get more torque by making it larger, too, for the same "balance moment". I have, after a lot of experimentation, gone back to 18" or so for my models, the 20, 22, and 24" options suggesting that Ted got it right back in 1978.

     "Tail volume coefficient" and the various methods of measuring tail volume, as Howard notes, are sort of ad-hoc measures that are good in some situations and will weed out the obviously wrong solutions, but don't really accurately tell you how it will fly,

   Brett

[Peter in Fairfax, VA]

There are likely other effects.  I'd imagine that "clean air" is an issue.  For example, there might be turbulence near the main wing, as well as power plant turbulence.  And the height of the stab relative to the wing height would also be an influence. 

[Tim Wescott]

... Brett, as I recall, thinks that, for stunt planes, l_t by itself is of interest, because the maneuvers we fly are of fixed size, rather than proportional to mean aerodynamic chord.  ...

So does Frank Ziac -- see "Circular Airflow".

[Matt Piatkowski]

Thanks, guys.
I have found Ted's article and plans of Imitation. Do you know if the electric version of this model was ever built?

Brett wrote: "pitch acceleration (enhanced by longer tail/increased tail volume), and peak pitch rate (inhibited by the longer tail).."
What about the arrangement in which the l_t is variable for the given stunt plane and can be modified by shifting the horizontal empennage FWD and AFT? What about changing the stabilizer and elevator surface areas?

I can actually try both methods in one of my new stunt planes but first I have to fly to Poland to pick them up...Hmm. 

Stay safe, kill this virus and fly happily ever after.
Regards,
M

[Brett Buck]

I have found Ted's article and plans of Imitation. Do you know if the electric version of this model was ever built?

   There was certainly no mention of an electric version in either of Teds articles.  I have seen/flown an Imitation electric *twin*. And there have been plenty of models that were, er, undocumented tribute models of the Imitation, which I decline to point out. This is the not-electric twin (LA 25s, I think) but Bob Duncan also has an electric twin, and probably an electric single, all my flights were after 8-10 hours in the 100+ degree central valley sun.

Brett wrote: "pitch acceleration (enhanced by longer tail/increased tail volume), and peak pitch rate (inhibited by the longer tail).."
What about the arrangement in which the l_t is variable for the given stunt plane and can be modified by shifting the horizontal empennage FWD and AFT? What about changing the stabilizer and elevator surface areas?

 I_t? I_yy (pitch moment of inertia)?   

   If you can shift the entire stab/elevator assembly easily fore and aft, then that would be a fine way to do the experiment. Of course, at a particular arrangement of the stab, you will have to re-optimize everything else for that position, which means flap deflection and/or area, CG, , control ratios, even the motor/prop/feedback setup, and fly it in each configuration in sufficiently varied conditions to determine how it really works. Then change the tail, and re-do everything to optimize it for that group of settings.

     If you just move the tail and leave everything else alone, and judge which one flies the best, what you have done is not to determine which tail moment/volume is ideal, but which one is ideal for the other settings you did not change. That's interesting by itself, but doesn't tell you if the tail moment is the determining factor.   

That's why it is so difficult to conduct controlled experiments in stunt (or actually, any field), and why so many people tend to hit on something that worked great one day, and then build up a whole world of reasons behind it - when it actually was something else. It's very difficult to avoid jumping to a conclusion on partial data. And it can be extremely frustrating, as I think you have discovered.

    Don't let that discourage you from trying, just don't expect it to be a weekend's worth of work, or a month, or a season to come to a conclusion. It also helps to have other people of equal or superior skills to bounce things off of, and to help with the evaluation.

   We are here to help, whether it seems that way or not.

      Brett


p.s. one thing we have found over the years is to *make the changes big enough to be sure that you are seeing the effect of the change*. For the tail moment, you might be inclined to go in 1/4" increments, you know, really fine-tune it. I would suggest instead changes of more like 2", because anything less is probably too small a difference to make you have to re-optimize it. People, myself included, tend to think they have things refined a lot more than they really do, and aren't aggressive enough with changes. There are some things where tiny variants matter (like tip weight, where Howard can attest that you can tell the difference in 3 grams in tip weight while drinking a pop and talking with your buddies and more-or-less just listening to the way the corners sound...) but most things are not like that. I have gotten burned repeatedly by making too small a change in needle settings, just because I can make infinitely fine adjustments. A decent click-type needle more-or-less prevents that.
   

[Matt Piatkowski]

Hi Brett,
Howard designated I_t as the distance between the quarter aerodynamic chords of the wing and tail.

Please see the attached. This plane (MP Bee II) is waiting for me in Poland and may need the increase of the I_t . It currently has the hinge lines distance ~18.50" (like Yatsenko's Shark in the typical configuration) but the wings have larger span (~62-64") and the surface area (~710 - 720 in^2). The builder of this model (Aleksandr Leonidov from Kharkiv, Ukraine ) likes to keep "secrets" and I had to press hard to squeeze the approximate numbers above from him. Old habits die hard....

If I can get to Poland before the next winter, I will continue my "C/L stunt research" work. At this moment, the "to do" list has five items:
1. Measure MP Bee II 
2. The I_t changes impact on corners
3. Using 13.5x5.5x3 carbon composite propellers (weight=0.63 oz., extremely stiff blades) with different kv=530-550 motors and 6S and evaluation of the gyroscopic moment effect in corners
4. Effect of wind on maneuvers for the single propeller and contra powered planes (MP Bee II, Big Red and another 60" stunt model - no name yet)
5. Modification of the logarithmic control system in my Big Red (Max Bee II) to allow for larger flaps and elevator deflections

I hope the next winter will be mild, otherwise I would not be able to fly enough to collect a reasonable body of evidence.

Two motor stunter plans are gathering dust in my workshop but one day I will build such plane.

Stay safe, kill the virus and fly happily ever after,
M

[Tim Wescott]

   If you can shift the entire stab/elevator assembly easily fore and aft, then that would be a fine way to do the experiment. Of course, at a particular arrangement of the stab, you will have to re-optimize everything else for that position, which means flap deflection and/or area, CG, , control ratios, even the motor/prop/feedback setup, and fly it in each configuration in sufficiently varied conditions to determine how it really works. Then change the tail, and re-do everything to optimize it for that group of settings.

     If you just move the tail and leave everything else alone, and judge which one flies the best, what you have done is not to determine which tail moment/volume is ideal, but which one is ideal for the other settings you did not change. That's interesting by itself, but doesn't tell you if the tail moment is the determining factor.   

If that's not clear enough -- if you just change one thing and your plane flies better, that means it was trimmed wrong for where things were before.

The only exceptions to this that I can think of are if you're starting with an utterly wrong power system (prop, motor/engine, etc.), or maybe going to a lighter handle.

[Howard Rush]

l_t where l is lower-case L.  I regret the confusion.

[billbyles]

snip<There are some things where tiny variants matter (like tip weight, where Howard can attest that you can tell the difference in 3 grams in tip weight >snip

quote:

When I was first setting up my first Impact Bob Whitely was helping/teaching me to trim it.  He would fly a flight and then I would fly one, making trim changing things as we went.  I started out with 3/4 ounce of tip weight.  At one point RJ said "Take out 1/8 ounce of tip weight and I thought to my self "Huh, that won't make any difference, but what the heck, OK."  So I took out 1/8 ounce, we re-flew it and it got quite a bit better.  Lesson learned, listen to the guys who know.  We put sixteen flights on that morning at Mile Square Park in Fountain Valley and it was well worth it.

[Paul Walker]

matter (like tip weight, where Howard can attest that you can tell the difference in 3 grams in tip weight while drinking a pop and talking with your buddies and more-or-less just listening to the way the corners sound...) but most things are not like that.


Wow, 3 grams is a lot. Yes, that is easy to feel. Let me know when you can feel 1 gram!

[Howard Rush]

Brett can watch your airplane and tell when you need to add one (1) gram. 

[Dan McEntee]

   I had a big "Ah HA!!" moment in this regard with tip weight a few years ago. I have a profile Cardinal that I acquired and was flying it with a LA.40, and thought it flew pretty well. The only thing I saw with the trim after my initial changes from the previous owner was that it would bang the out board wing down on corners, both inside and out. I check for tip weight and there was very little in it, maybe just a few of the stick on weights in 1/4 ounce increments. I thought that "damn, I need to have some tip weight in there, don't I??" So I just took one 1/4 section out and put it up for a flight and wow! I had never in a million years thought that 1/4 ounce would make that much of a difference. That is about 7.5 grams?? I have a SIG P-Force that I had the same issue with and worked with that for a flying session, and ended up with no tip weight in that, if I recall. That model has a bazillion flights on it and has been de-greased and recovered but the out board wing may still have some oil soaked parts in it, I think. It's those subtle little tweaks that I have always had trouble figuring out and executing.
  Type at you later,
   Dan McEntee

[Jim Svitko]

   I had a big "Ah HA!!" moment in this regard with tip weight a few years ago. I have a profile Cardinal that I acquired and was flying it with a LA.40, and thought it flew pretty well. The only thing I saw with the trim after my initial changes from the previous owner was that it would bang the out board wing down on corners, both inside and out. I check for tip weight and there was very little in it, maybe just a few of the stick on weights in 1/4 ounce increments. I thought that "damn, I need to have some tip weight in there, don't I??" So I just took one 1/4 section out and put it up for a flight and wow! I had never in a million years thought that 1/4 ounce would make that much of a difference. That is about 7.5 grams?? I have a SIG P-Force that I had the same issue with and worked with that for a flying session, and ended up with no tip weight in that, if I recall. That model has a bazillion flights on it and has been de-greased and recovered but the out board wing may still have some oil soaked parts in it, I think. It's those subtle little tweaks that I have always had trouble figuring out and executing.
  Type at you later,
   Dan McEntee

A side mounted engine will affect the tip weight required.   I forgot about this on a plane I built some time ago.  It was a full fuselage but side mounted engine.  I had a terrible time trying to trim it.  Finally, I realized what was happening and I had to remove a good bit of tip weight.  I rarely build profiles or any side mount set ups and on this model I had installed the usual amount of tip weight in the weight box for an inverted engine mount.

[Matt Piatkowski]

Hello everybody,
Please be kindly reminded that the subject of this thread is hinge-to-hinge distance ( or l_t following Howard's designation) and not the tip weight.
I know that all parameters of the C/L stunt plane are connected (ref: Paul Walker's Trimming Guide) and influence each other. How much, or rather what is the sensitivity of, for example, hinge-to-hinge distance changes for the wing tip weight changes, remains to be discovered.

Latest news: One of the very good F2B fliers in Europe, has increased the h-t-h (hinge-to-hinge) distance in his newest model to 515 mm. (20.27"). At the same time, he increased the width of the horizontal stabilizer from 95 to 115 mm., leaving the horizontal stabilizer's span the same as before. "Before" means in his previous model that I saw flying the pattern very well  many times. The "before" h-t-h distance was 500 mm. (19.7"). The model is full size electric stunt plane (~60" span, 65-66 oz. RTF weight). Except this change, the model remains the same.

20.27" h-t-h distance is most likely the largest distance ever in the full size stunt model flown by the very good F2B pilot (comments, please, if applicable)

The flight tests of the new arrangement is not possible at this moment because of the global pandemic. I will keep everybody posted.

Stay safe,
M
 

[Brett Buck]

20.27" h-t-h distance is most likely the largest distance ever in the full size stunt model flown by the very good F2B pilot (comments, please, if applicable)

   No. I have had airplanes with tail moments of 22 and 24", and I know of at least several others. Phil Granderson has at least one like that, Bruce Perry, as I recall, had at least one at 22 or 24, I would check the SSW archives, if it still existed. I am sure several of Windy airplanes were at least that big.

   The idea goes back to at least 1978, where Ted Fancher was the first to write clearly on the topic, and the first well-known example to deviate from the "magic numbers" school where people took ratios of successful models and slavishly copied them, in this case, the almighty sacred 5:8 ratio of "nose moment" to "tail moment.

    These sort of experiments went on through the 80's and 90's, after which I think most people have settled on Ted's original solution, 18" or so. 20 or 22" didn't seem to hurt anything other than the balance. It's not that critical and even a 2" change doesn't make a big difference in the result.

     Brett

[Matt Piatkowski]

Hi Brett,
Thank you for your comments.
22-24" is a veeery loong tail.
Could you , please, check your archives?

Would you agree that the corners of the world's, say, fifteen best stunt pilots are becoming progressively sharper when considering the period 1978 -2020?
To put it differently: sharp corner in 1978 is no longer considered sharp in 2020.

I was watching on YouTube the corners of Orestes Hernandez' Shark in slow motion. I do not know which one of his Sharks he was using in this movie but I know that he had (still has?) four Sharks having the h-t-h distances of 470, 475, 480 and 485 mm. I also know that the Shark that won F2B in 2016 in Australia had the h-t-h distance 470 mm.

Perhaps shorter is actually better these days?

Stay safe,
M

[Brett Buck]

Hi Brett,
Thank you for your comments.
22-24" is a veeery loong tail.
Could you , please, check your archives?

   What do you mean "check my archives"?  You think I am making it up? You want me to post pictures of a ruler next to the fuselage of a 31-year-old airplane!? 

   And in any case, I said earlier that this is probably too long, and that most people have settled on something around 18", which after converting your metric to conventional units, is about what you showed - "485 mm" is about 19".

    All else being equal, you would not be able to tell the difference between 17.5, 18, and 19, it's just not that critical or important. In most cases, other factors that you are not considering would dominate the performance. I caution you again about jumping to conclusions - just because you and others are doing experiments with tail moments, does not mean the differences you note from airplane to airplane are due to that change, and not the 1000 other things that are probably different. It took *a long time* with *many competent experimenters* and a *vast number of carefully-evaluated results* to come to the current level of understanding.

Would you agree that the corners of the world's, say, fifteen best stunt pilots are becoming progressively sharper when considering the period 1978 -2020?
To put it differently: sharp corner in 1978 is no longer considered sharp in 2020.

      I am not sure how you are determining the "world's 15 best pilots" without seeing most of them fly, but it's not that important.

     At the FAI level, people are flying tighter than they were because that appears to win contests, but *the reason people are doing it better* is largely because of what was started in 1978, i.e. longer tail moments. The other factor is getting much better power systems, starting in 1988. It simply wasn't possible to do what people are doing now with 1978 engines, still isn't, which is what drives me nuts about the "Engine Forum" - because people are still trying to thrash away with something has been obsolete for 40 years.

  In any case, the original Imitation with the original ST46 probably still turns sharper than most people are doing or are capable of handling, and would be a tremendous upgrade for most people. Most of the competitive west-coast airplanes, in particular the Trivial Pursuit, Infinity, and Thundergazer, are attempts to replicate the original performance of the Imitation with a full fuselage. The Thundergazer, in particular, is about as close as you can get without a Xerox machine - except with a piped 75.

     The current standards were set, effectively, in 1990 or so, with the combination of genuinely sharper corners, and the very superior ability to start and stop the corners that make it look sharper whether it is or not.  Paul Walker set the standard to such a degree that he won the NATs 5 years in a row, to the point he got bored with it. A few of us caught on and became competitive, far more people never got it, still don't, and some of them came the conclusion that the contests were rigged. Nothing has changed all that much since then, there was a brief degeneration during the 4-stroke "revolution" that proved to be a dead end, now Paul is back setting the standards again, along with his cohorts, with even better propulsion systems.

    Throughout that time, one of the big knocks on the FAI was that the Chinese were winning contest after contest doing square 8s you couldn't tell from round 8s, they were so soft. Now, particularly since Igor demonstrated it (since nothing is ever real to the FAI until Europeans do it...) in spectacular fashion, the pendulum has swung the other way dramatically, now, cornering is the only thing that seems to matter. Either approach is wrong for reasons that seem rather obvious.

     Point being, something isn't new just because you happened to notice it.  This has been going on a very long time.

      Brett

[Matt Piatkowski]

Hi Brett,
I hoped you were sort of done with your "combative communication style" but not yet.

What are SSW archives?

I had a pleasure to watch several contests in the EU with the best Slovak, Czech, Polish, Ukrainian, Lithuanian and Israeli F2B pilots. In five of them I competed, gaining valuable international experience.
I saw one, very good, Chinese pilot and Russian, French and German fliers.
Having this in mind, I know very well what level of performance is needed to win the F2B World Cup or the WChamps.

I have never seen the US Stunt Team in action and hoped to do it during the WChamps in Wloclawek. The next three months will show if this event happens or not in 2020.

Thank you for your opinions and comments - some of them are quite useful.
Best Regards, stay safe,
M

[Howard Rush]

I have never seen the US Stunt Team in action and hoped to do it during the WChamps in Wloclawek.

You are in for a treat.

[Peter in Fairfax, VA]

SSW = Stuka Stunt Works, a forum / archive that has recently become unavailable.

[Matt Piatkowski]

Hi Howard,
I hope to meet you and other members of the US Stunt Team during the WChamps.
Could you please satisfy my never ending curiosity...what will you fly? Any photos?

If the event is cancelled in 2020, it will be next year and I will be there.

Hi Peter,
Indeed, Stuka Stunt Works archives are inactive/inaccessible.

Regards, stay safe,
M
 
 

[Ted Fancher]

Hi Matt,

I'm pretty much out of my league here re aerodynamics but I think it would clarify your thoughts with respect to the inherent importance/impact of "hinge line to hinge line distance" in terms of stunt model design if you considered the following:

Are you willing to accept as valid and design a stunt ship based on the premise that an 18" hinge line to hinge line distance has the same impact on a 200 square inch, 4 to 1 aspect ratio wing area stunt ship as on a 700 square inch one with a 6 to 1 aspect ratio?  How about with a stab/elevator with an area of 15% of the wing area vice one with 25%?  How about with a tail aspect ratio of "four" vice "six"?

I believe your answer will be "has Ted lost his mind?  Of course not".

IMHO, the distance between the flap and elevator hingelines has no intrinsic value except when considered in concert with these (and many other factors) all of which will work together...for better or worse...to produce the desired result on a specific design.

Interesting thread nonetheless.  Hope you get to go to Poland for the big meet.  Sure up in the air now, I guess...or has it been cancelled???

Ted Fancher

Ooops.  Posted this shortly after Matt's latest advising re the WCs.  Guess it's still "up in the air", huh.  (Sorry, Howard.  Couldn't help myself!)

[Matt Piatkowski]

Hi Ted,
Nice to hear from you!
I saw the photo of you and Imitation from the 1979 - we both had mustache at that time but I never had beard.
I still have mustache and my wife says that this was one of the reasons she noticed me.

In 1979 the h-t-h distance was moderate and the downhill skis were veeery loong and narrow. Now, the h-t-h distance seems to be growing (this is my opinion...) but the skis are shorter and wider.

Of course I agree with you that ".. the distance between the flap and elevator hingelines has no intrinsic value except when considered in concert with these (and many other factors) all of which will work together...for better or worse...to produce the desired result on a specific design".

The only thing I would like to add is: the target function in whatever we, "Fliers of the Circle" do, is SOMEHOW put many things together to achieve the highest possible scores.
As banal as it sounds, it is very difficult but also exciting.

In my never ending quest to improve and understand, this EXCITING is the most important part.

The WChamps 2020 are still possible, though Antonis Papadopoulos, CIAM President, published recently a letter, stating that until May 31, 2020,  the WChamps Co-ordinators will be in constant communication with the Polish organizers.

All we can do is wait and pray for this nasty virus to disappear worldwide no later than in July.

Stay safe,
M

[Howard Rush]

Hi Howard,
I hope to meet you and other members of the US Stunt Team during the WChamps.
Could you please satisfy my never ending curiosity...what will you fly? Any photos?

Here is what I shall fly, although with new stabilizer and right wing.  I shall also have a new model of similar configuration. 

I have no mustache.  I do not want the ladies to notice me in these dangerous times. 

[Ted Fancher]

Hmmm.  Howard's got his "game face" on!

Ted

p.s. the quotation marks are appropriate.  I actually said game face before I typed it...ergo, it was a quote whether you could hear it or not.  I've elected to apply that method to all of my subsequent utilizations of the doubled apostrophe!

[ptg]

   No. I have had airplanes with tail moments of 22 and 24", and I know of at least several others. Phil Granderson has at least one like that

    These sort of experiments went on through the 80's and 90's, after which I think most people have settled on Ted's original solution, 18" or so. 20 or 22" didn't seem to hurt anything other than the balance. It's not that critical and even a 2" change doesn't make a big difference in the result.

     Brett

Brett there are 6 planes I can remember that are at least 24" and 2 of them are Classic Legal. The longest was a plane I named "Triumph" designed and built in 1966.  I was a senior in high school (also a senior AMA flyer). It featured a fully sheeted wing my 'dynamic airfoil' where the high point at the root cord was 50% and gradually moved forward to 20% at the tip. It it had a tail of 25" and a metal flake paint job.  It also had a balanced elevator.  I remember flying it at a contest and the late Denny Shauer (sp) who was I believe the designer of the Gladiator (if not the designer he definitely flew a red and yellow one back then).  Denny came over and scrutinized every inch of the plane and said " this is really different, what makes this thing turn so good?  Is it the tail?

I know Wynn Paul has a picture, I'll contact him.  Also I know EVERYBODY wishes he would release his chronicles in some form and would happily pay any amount he asked. I'd pay double!

Ted may have written something about tail lengths in the late 70s but I was flying very long tails way before that.  There 8 currently hanging on the wall.  Needless to say my opinions are quite different than those in this thread are somewhat different from those expressed here. I've been here since the mid 60s.  If I could build and fly I'd still be crankin 'em out.

[Crist Rigotti]

Hi Phil!  Hope all is well.

[ptg]

Hi Crist,
My brain is working good as ever but my body refuses to cooperate!

[Brett Buck]

Ted may have written something about tail lengths in the late 70s but I was flying very long tails way before that.  There 8 currently hanging on the wall.  Needless to say my opinions are quite different than those in this thread are somewhat different from those expressed here. I've been here since the mid 60s.  If I could build and fly I'd still be crankin 'em out.

   I wish you were! I miss you.

    My point was/is this is not a remotely new phenomenon.

     Brett

[John Leidle]

   Phil ,
  It's truly nice to see your typing here... you have been missed at the Northern contests lately.
  John L.

[Trostle]

Here is what I shall fly, although with new stabilizer and right wing.  I shall also have a new model of similar configuration. 

I have no mustache.  I do not want the ladies to notice me in these dangerous times.

That is a really neat grass flying field! 

Keith

[Crist Rigotti]

Hi Crist,
My brain is working good as ever but my body refuses to cooperate!

Well, it's good to hear from you.  Take care.

[Ted Fancher]

Brett there are 6 planes I can remember that are at least 24" and 2 of them are Classic Legal. The longest was a plane I named "Triumph" designed and built in 1966.  I was a senior in high school (also a senior AMA flyer). It featured a fully sheeted wing my 'dynamic airfoil' where the high point at the root cord was 50% and gradually moved forward to 20% at the tip. It it had a tail of 25" and a metal flake paint job.  It also had a balanced elevator.  I remember flying it at a contest and the late Denny Shauer (sp) who was I believe the designer of the Gladiator (if not the designer he definitely flew a red and yellow one back then).  Denny came over and scrutinized every inch of the plane and said " this is really different, what makes this thing turn so good?  Is it the tail?

I know Wynn Paul has a picture, I'll contact him.  Also I know EVERYBODY wishes he would release his chronicles in some form and would happily pay any amount he asked. I'd pay double!

Ted may have written something about tail lengths in the late 70s but I was flying very long tails way before that.  There 8 currently hanging on the wall.  Needless to say my opinions are quite different than those in this thread are somewhat different from those expressed here. I've been here since the mid 60s.  If I could build and fly I'd still be crankin 'em out.

Hey, PTG!

So good to hear from you.  You and I seem to be more or less on the same subway car...sit'en and wait'en' to get wherever it is we're going.  I can count on both hands the flights I've flown in the last several years...whatever the "hinge to hinge" length was down to fractions of inches!

I would be delighted to hear what it was you were looking for and what you found during your "tail length" journey.  Was there magic everywhere?: somewhere?; anywhere?  What had you expected to learn and what did you learn?  Most important...where did you end up finding the answer to be???  Was it "magic" or just interesting?

So nice to be able to experiment without astronauts in the seats, don't you think?

All the best to you and your lovely spouse.  A joyous Easter to you both.

Ted Fancher

p.s. Boy am I with you re Wynn's stunt history books.  Like you, he's another of stunt's great contributors I was once close to on regular basis but for whom years, ages and lack of propinquity have proven difficult to overcome.  The CLPA fraternity will be ever thankful...and better informed...when they are available.

[Bruce Perry]

Brett mentioned me earlier. I don't get here very often anymore, so this may be late.

I have airplanes of similar lineage from 17.5. 18.5. And 20 inches even. I stopped at 20. I felt there were mild differences at each step.  Ones that I enjoyed.  However, like Brett said, there are 1000s of variables at play and I can't isolate hth as the sole cause of the characteristics that I preferred in the long tail planes.  That said I haven't gone shorter again either.

Every pilot has personal preferences that the model must perform within.  As we are all different, our models must be too.

Bruce

[Ted Fancher]

"snip"
Ted may have written something about tail lengths in the late 70s but I was flying very long tails way before that.  There 8 currently hanging on the wall.  Needless to say my opinions are quite different than those in this thread are somewhat different from those expressed here. I've been here since the mid 60s.  If I could build and fly I'd still be crankin' 'em out.

Just a note of clarification regarding Phil's last paragraph and some other discussion on this "hinge-to-hinge" thread.

I don't believe I've ever written or experimented with anything regarding "hinge line to hinge line" length.  Although the development of my "junior bird man, wet finger in the breeze" theories would have resulted in changes in that aspect I don't believe I ever discussed let alone utilized that measurement during my experimentation with or writing about my ultimate "theories".

What I did work and experiment with diligently during late '70s to, maybe, early '90s was a trial by error (designing, building, flying and competing) examination of: CG/CL (chordwise center of lift) locations; tail area as a percentage of wing area; aspect ratios of both wings and tails; aspect ratios of flaps and elevators as a percentage of wings and tails and, more modestly-on a case by case flight trim basis-flap vice elevator deflection to optimize the amount of deflection of each to permit aggressive cornering but not provide excessive feedback (effort required) to the pilot.  My ultimate goal was to produce a ship that could maneuver agilely with modest handle inputs in calm to significant winds, requiring as little as possible large scale actors--elbows, shoulders, entire arm-- displacement.  A stunt ship that would seldom if ever demand modified pilot inputs to achieve the desired maneuver tracks...i.e. arm waving and/or handle yanking to achieve the necessary control system deflection to achieve the desired result.

I hasten to add that I have/had no unique/formal training in the aerodynamic realm other than those fundamentals necessary to qualify to fly "big" airplanes, i.e. tiny ones to B-747s.  Thousands of hours in those aircraft did, however, provide a "feel" for the effects of control system displacement to alter the "pitch" of whatever I was in.  Training in those aircraft also exposes the student to the concept of the effects of CG "loading/location" on aircraft trim and response, etc.

In other words I pretty much fiddled with it on a "wing and a prayer" plus a pretty accurate mental gauge of what causes what...although no clue as to how much of "what" would do "what".  Ergo, toy airplanes with significant needs for optimal trim in the pitch axis.  My designs during my grown up competitive years were an ongoing search for what seemed to me to be pretty ideal "to me" combination of the factors mentioned above.  I wouldn't pretend to tell you I could quantify any of the trim factors I believed to be of value mathematically.  Nonetheless I always felt that my kinetic evaluation was reasonably valid enough to discuss.

Sorry, all this solely to advise that my experimentation in the subject matter of this thread was never considered or discussed as "hinge-to-hinge".  Although that dimension and such changes are certainly reflected in the finished product I don't believe I ever once based a dimension based on that "fixed" measurement.

Finally, an admission.  My ultimate kick in the a$$ to work hard at this goal came from a long ago Nats in Nebraska won by a guy you all know, whose last name sounds like he needs a two handed rolling support to walk.  The top five flyoff that year was flown in a gale and some of the biggest names in the stunt business were getting their butts pretty soundly whipped...except this guy.  The only time I can recall watching the observers stand and applaud was after one of his flights during as bad a wind as anyone encountered.  I was so impressed that I went to the pits and, showing modest interest, picked up the ship under each wing...and almost dropped it on its tail.  The CG was so much further aft than I thought was in the "normal" range that I would never forget my shock.  I then and there decided design changes to allow such a CG would pay great dividends.  So it proved to be.

All the rest of this drivel was the result of that--maybe one minute--visit with an airplane the designer of which ignored the then "norms" of stunt design.

Ted

[Brett Buck]

Just a note of clarification regarding Phil's last paragraph and some other discussion on this "hinge-to-hinge" thread.

I don't believe I've ever written or experimented with anything regarding "hinge line to hinge line" length.  Although the development of my "junior bird man, wet finger in the breeze" theories would have resulted in changes in that aspect I don't believe I ever discussed let alone utilized that measurement during my experimentation with or writing about my ultimate "theories".

   The Imitation article is the first time someone at a high competitive level talked about longer tail moments, in particularly, violating the sacred 5:8 ratio of "nose moment" to "tail moment". It was certainly the basis of my experiments and many others.

      Brett