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Author Topic: engine, wing, elevator-stab center line; why not in a straight line?  (Read 1450 times)

Offline Charles Hofacker

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There are numerous comments on the subject of symmetry but I don't get the "why". I was browsing Aerofred free plans and it seems most of our c/l models have the wing c/l below the engine c/l and the stab c/l above the engine c/l to varying degrees as far back as I could see plans. Would somebody jump in here and explain why the asymmetry is used? I did see a few designs with the wing and stab c/l aligned and at least one design had all three c/l aligned but these seem to be the exception. We seem to have evolved to a configuration but why?

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #1 on: September 12, 2020, 10:50:54 AM »
the thrust line is up to give clearance to the cylinder head and the tail is up to eliminate the Z bend in the push rod.


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Online Dan McEntee

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #2 on: September 12, 2020, 12:34:43 PM »
There are numerous comments on the subject of symmetry but I don't get the "why". I was browsing Aerofred free plans and it seems most of our c/l models have the wing c/l below the engine c/l and the stab c/l above the engine c/l to varying degrees as far back as I could see plans. Would somebody jump in here and explain why the asymmetry is used? I did see a few designs with the wing and stab c/l aligned and at least one design had all three c/l aligned but these seem to be the exception. We seem to have evolved to a configuration but why?

     When all three components are all lined up, that is called an in line configuration and has been around for quite a while, and it tends to come and go. I believe, but not 100% sure, that Paul Walker has gone back to it on his current model as have a few others. I have built a few in line models over the years going back to 1990 or so.. There is an aerodynamic reason for both set ups that I'm positive that Brett, Bob Hunt or Howard and some others can elaborate on in great detail that I would be sure to screw up if I tried, I just know from being in this event for a lot of years and reading stuff in Stunt News and on the forums. I'll just say that this is one subject that you can stay up all night ling while drinking a lot of beer and arguing about. They both work, and both are subject to how accurate your alignment and over all construction is.
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Online Jim Svitko

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #3 on: September 12, 2020, 01:39:46 PM »
As Dan said, both configurations work.  I have built and flown both and I am not able to see a difference in performance.  But, I have not yet built the same plane with each configuration to make a valid comparison.

One item that can be factor here is the vertical CG position.  This might not matter very much but it can be a problem, depending on configuration.

If you mount the engine inverted and everything is in-line (thrust line, wing, stab), you will need a longer landing gear for prop clearance.  The power train CG is below the wing chord.  The longer landing gear will also pull the vertical CG down.  There might not be enough structural weight above the wing chord (fuselage, vertical tail) to compensate.  Your leadout exit location will have to move down as well.  Depending on where the vertical CG ends up, you could have a situation where the wings will not be level in flight.

When I saw my first KA10, I noticed that the leadouts exited the wing below the wing chord line.  If my memory is correct here, the KA10 is an in-line design.  When I asked about the leadouts, I was told that it was necessary due to the vertical CG position.

You can make some calculations to get things very close to keeping the vertical CG on the wing chord so you do not have to make any leadout position change.

 

Offline Ken Culbertson

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #4 on: September 12, 2020, 02:54:13 PM »
the thrust line is up to give clearance to the cylinder head and the tail is up to eliminate the Z bend in the push rod.


Motorman 8)
It may be as simple as that.  You center the wing on the 3" side sheet, put the elevator on the top in the back(Sunk in of course) and place the motor mounts to the top in the front and you have just laid out 75% of the stunt ships designed in the last 50 years.

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Offline Dave_Trible

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #5 on: September 12, 2020, 05:49:16 PM »
As Dan said, both configurations work.  I have built and flown both and I am not able to see a difference in performance.  But, I have not yet built the same plane with each configuration to make a valid comparison.

One item that can be factor here is the vertical CG position.  This might not matter very much but it can be a problem, depending on configuration.

If you mount the engine inverted and everything is in-line (thrust line, wing, stab), you will need a longer landing gear for prop clearance.  The power train CG is below the wing chord.  The longer landing gear will also pull the vertical CG down.  There might not be enough structural weight above the wing chord (fuselage, vertical tail) to compensate.  Your leadout exit location will have to move down as well.  Depending on where the vertical CG ends up, you could have a situation where the wings will not be level in flight.

When I saw my first KA10, I noticed that the leadouts exited the wing below the wing chord line.  If my memory is correct here, the KA10 is an in-line design.  When I asked about the leadouts, I was told that it was necessary due to the vertical CG position.

You can make some calculations to get things very close to keeping the vertical CG on the wing chord so you do not have to make any leadout position change.
Jim I think you have hit upon 98% of why we do this-the vertical CG position.  The bulk of the engine, pipe or muffler, landing gear with wheels and what else is attached (pants, spats) will all fall below the tether point in the vertical plane and that may cause the airplane to bank inwards slightly.  It can be trimmed out but will still vary with flying speed and then maybe different yet overhead.  All that rests above the tether is a small portion of top fuselage and maybe the stab.  Also in-line setups can look unusual and might have less curb appeal. A good representation to look at would be the Baron Avanti.  If it weren't sort of jet-styled it would be hard to be made to look good.  Most full scale monoplane airplanes are low wingers and we are used to looking at them.  Another reason many are like that in both model and full scale is to shorten (lighten, stiffen) the landing gear.  In any event there should be moderation when designing a stunt airplane in this respect.  When the wing centerline goes too far south the inside/outside turn rate goes asymmetric, the stab placed too high, or V tailed as well.  These can be trimmed out with handle bias or control system adjustments but it's just easier to color inside the lines......

Dave
« Last Edit: September 12, 2020, 06:22:21 PM by Dave_Trible »
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Online Dan McEntee

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #6 on: September 12, 2020, 07:29:09 PM »
the thrust line is up to give clearance to the cylinder head and the tail is up to eliminate the Z bend in the push rod.


Motorman 8)

   The Sakitumi is an in line design that flies quite well and mine has a carbon tube for a push rod with no off sets in either end of the push rod.
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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #7 on: September 12, 2020, 09:24:34 PM »
Ain't got flaps.
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Online Dan McEntee

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #8 on: September 13, 2020, 07:00:15 PM »
Ain't got flaps.

    So? The model that got me out of beginner, through intermediate and won an advanced trophy or two was an in line design, had flaps, and dave brown pushrod with no zig zag bends.
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Online Igor Burger

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #9 on: September 14, 2020, 07:14:09 AM »
It was covered several times here or on stuka ... short answer is that drag under the thrust line helps beat prop precession pushing nose up (therefore it does not work with pusher props) ... the long answer is really long, because there are many other variables in he formula, like motor offset, elevator coincidence, L/G drag, p-factor, down wash  ... so better stay with that short answer  VD~

Offline Steve Berry

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #10 on: September 14, 2020, 07:37:55 AM »
I'm going to really throw in a monkey wrench and add another couple of variables. Built-up fuse vs profile for inline designs, and then electric vs glow.

Years ago, I took the wing from an old Sterling Mustang, cut off the flaps, and built a plane that we dubbed "The Drone." It was in line and only 2" thick. 2" x 36" profile fuse, motor mounted  on centerline, along with stab on centerline, and 2 little rudders on either end of the stab. I was tired of breaking off the rudder if I landed inverted (whether through engine quitting at wrong time, or pilot error) and so built a plane that was symmetrical top to bottom with nothing sticking above the fuse. Turned into the best flying, best tracking plane I've ever had. Equal turns, solid line tension, and would do anything I asked of it.

Next, with electric, there's no cylinder hanging down, so the only thing to worry about would be weight of landing gear. This assumes you mount the battery directly inline with the motor.

Now, let the arguments really begin.

Online Ted Fancher

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #11 on: September 14, 2020, 03:20:30 PM »
Apropos of nothing I have a unique story re "in-line" stunt ships.  The events occurred at the 1980 Nats and starred Bob Baron and his Avanti II in line designed stunt ship with which he finished 4th that year...obviously pilot and plane flying exceptionally well.  I, on the other hand, managed a 5th place finish just behind Bob flying the Imitation, having crashed my Excitation due to a control system failure warming up that AM prior to the Top five flyoff....that's my excuse and I'm sticking with it!

After the flyoff was over Bob asked if I would like to fly his Avanti II.  Because, historically, the Bob Baron/Wild Bill Netzeband team had been in the forefront of then current "innovative" stunt design I was delighted to take him up on his offer.  Again, the Avanti was exactly the design concept under discussion in this thread...thrust line, wing and stab/elevator on exactly the same vertical  plane.

Long story short (I know, I know you don't believe it) following an uneventful but not necessarily assisted by the pilot take off I was struck by the fact that I was unable to fly the ship in steady state level flight and, in fact, was concerned about two things...it didn't want to fly at level flight altitude and I was thus unwilling to do any maneuvers beyond a handful of inside/outside test loops and was scared to death about getting the ship on the ground in one piece.  It simply felt unresponsive to inputs and I felt I had no ability to even maintain "level" flight so simply held on as the ship went up and down more or less at will. 

Even more strangely, when the engine quit and I braced myself for impact the ship simply gently lost altitude and without assistance on my part made pretty much a 40 point touchdown!  Weird! The plane with which I found myself unable/unwilling to attempt even a “safe altitude pattern” had just finished a very competitive fourth below Les, Bubba and Billy; the reigning Championship US FAI team.

I was totally embarrassed and unable to account for what had just happened.  At the time I more or less in my mind thought it possible that the all in-line configuration was likely the culprit, but...Bob had kicked my butt with it!  Looking at the construction article in my "library" just now I noticed a couple three other things that were "different from the norm at the time that could be extrapolated by a non-aerodynamicist like myself to have contributed to the apparent instability. 

The elevators on the plans were significantly thinner than the stab; perhaps as little as 50% of the stab's thickness.  Could there have been a "null" or something in pitch response to initial pitch inputs due to the elevators needing to first transit that "gap"???  The flaps were a larger percentage of the chord than I would prefer now but hadn't given it any thought back then.  The stab/elevator was ~a solid 23% of the wing area which seemed just fine but the empty CG (on the mag plans) seemed a bit forward of where I would plan it nowadays at 18% (wagged) MAC...and of course, due to the fuel load, forward of that following takeoff when I first noticed the "instability" (for me, I must add...Bob flew it like it was on rails)

I find my assessment now…some 40 years later…not much different than the above thoughts.  I suspect Bob was simply perfectly comfortable with much greater inputs at the handle and was thus able to overcome the “gap” in response that I felt unwilling to apply.  How he flew it straight and level, however, escapes me to this day.

Combined with the top crop's current “love affair” with “in line set-ups” my suspicion is that Bob’s ship was anomalous with respect to the general concept likely, in part, for the reasons. I’ve suggested.

At any rate, for the balance of my competitive years I blatantly shunned any such configuration on my own ships.

Ted



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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #12 on: September 14, 2020, 08:06:12 PM »

(Clip)

  I suspect Bob was simply perfectly comfortable with much greater inputs at the handle and was thus able to overcome the “gap” in response that I felt unwilling to apply.  How he flew it straight and level, however, escapes me to this day.

(Clip)

Ted

Hi Ted,

I am not going to get into the discussion on in-line stunt designs.  However, I can relate to my experience of having the opportunity to fly one of Bob Baron's airplanes.  I do not remember which one I flew, there were several that I flew when Bob lived in the LA area, so it would have been well before his Avanti and his Nats win.  Several of us in the LA area were well aware of Baron's ability to fly extremely good patterns.  I was anxious to fly one of his airplanes as was at least one other previous Walker Cup winner.  We had much the same impression that you just wrote about.  I was glad to get the things on the ground in one piece, not doing anything more than a couple of loops.  Our consensus was that Baron had a way to trim his airplanes that somehow suited how he flew and he was extremely good at doing so.

Keith

Online Mike Alimov

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #13 on: September 15, 2020, 09:01:29 AM »
I'm going to really throw in a monkey wrench and add another couple of variables. Built-up fuse vs profile for inline designs, and then electric vs glow.

Years ago, I took the wing from an old Sterling Mustang, cut off the flaps, and built a plane that we dubbed "The Drone." It was in line and only 2" thick. 2" x 36" profile fuse, motor mounted  on centerline, along with stab on centerline, and 2 little rudders on either end of the stab. I was tired of breaking off the rudder if I landed inverted (whether through engine quitting at wrong time, or pilot error) and so built a plane that was symmetrical top to bottom with nothing sticking above the fuse. Turned into the best flying, best tracking plane I've ever had. Equal turns, solid line tension, and would do anything I asked of it.

Next, with electric, there's no cylinder hanging down, so the only thing to worry about would be weight of landing gear. This assumes you mount the battery directly inline with the motor.

Now, let the arguments really begin.

I don't think this will invoke too many arguments.
- Profile vs built up should not really influence the inline design;
- Electric vs glow technically should not either, but of course glow engines shake, and the resulting vibration of the tail helps shake / energize stagnant bubbles and boundary layers, so you have to be more carful designing electrics;
- your Drone likely was tracking well not because it was inline, but because of a healthy tail moment; 36" fuselage is pretty long for a Sterling Mustang wing; I had similar experience with my Trickie (wing from crashed Tucker + fuselage from my long-tail Quickie);
- If you still have a lot of inverted engine stall incidents, install a second set of landing gear on top.  It will save the airplane if landing inverted, AND create a truly symmetrical inline design - including compensated landing gear drag;
- If you've mastered flying inverted and don't want a second set of LG, move the battery up about 1 inch above centerline to compensate for the weight of the landing gear, and your inline airplane will be happier.
« Last Edit: September 15, 2020, 09:26:50 AM by Mike Alimov »
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Online Mike Alimov

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #14 on: September 15, 2020, 09:23:52 AM »
[snip]

I find my assessment now…some 40 years later…not much different than the above thoughts.  I suspect Bob was simply perfectly comfortable with much greater inputs at the handle and was thus able to overcome the “gap” in response that I felt unwilling to apply.  How he flew it straight and level, however, escapes me to this day.

Combined with the top crop's current “love affair” with “in line set-ups” my suspicion is that Bob’s ship was anomalous with respect to the general concept likely, in part, for the reasons. I’ve suggested.

At any rate, for the balance of my competitive years I blatantly shunned any such configuration on my own ships.

Ted

Ted's and Keith's recollections of their experiences flying Baron's airplanes made me remember the times I've flown a number of OPPs (other people's planes).  Interestingly, I also declared the majority of them virtually un-stuntable after the first few laps, even though I watched their owners put in complete patterns on them just hours earlier.  Some OPPs were flyable, but not 100% to my liking.  And now we have evidence that some NATS winners flew other NATS winners' planes and found them almost dangerous to fly.  I used to think that my experiences were unique or applied to flyers/ planes of Intermediate/ Advanced level only.  It turns out the individual "feel" and "trim" factor extends all the way to the top levels.

I doubt that Avanti was so tricky to fly due entirely to the in-line design.  Anatoly Kolesnikov, who placed 1st at the Worlds in 1986 and 2nd in 1988 (besides being tops in Europe a bunch of times), popularized his in-line KA-10 design, which had been built countless times, with everyone reporting very positive experiences with the airplane.  It also heavily influenced Yatsenko's Classic and its derivatives, which they write about in their article on the origins of their Classic design.  As we know, these airplanes now comprise a healthy share of aircraft competing at the Worlds every year.
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Offline Steve Fitton

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #15 on: September 15, 2020, 09:30:48 AM »
...  It also heavily influenced Yatsenko's Classic and its derivatives, which they write about in their article on the origins of their Classic design.  As we know, these airplanes now comprise a healthy share of aircraft competing at the Worlds every year.

Where can this article be found?
Steve

Online Mike Alimov

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #16 on: September 15, 2020, 11:42:44 AM »
Where can this article be found?

It's been on their website for years:
 http://discovery-aeromodels.com/en/yuriy-yatsenko-classic-f2b-model.html

Now, the article is written by non-native speakers, and may be difficult to understand.  The essence of what it says on this topic:

- One of the ideas given by Kolesnikov to the Yatsenko brothers was an inline design (engine, wing, stab);
- The reason for that is that it provides the most symmetrical feel for inside vs outside maneuvers;
- They also had first-hand experience flying Compostella's plane (retro-styled stunter with very high placement of the stab above the wing; past European Champion), and experienced highly asymmetrical feel for inside vs outside maneuvers, which they explain is due to aerodynamic shading of the stabilizer by the wing at typical cornering angles of attack.

For a complete translation of the article, contact me about my PayPal address   >:D
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Online Ted Fancher

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #17 on: September 15, 2020, 12:11:53 PM »
Hi Ted,

I am not going to get into the discussion on in-line stunt designs.  However, I can relate to my experience of having the opportunity to fly one of Bob Baron's airplanes.  I do not remember which one I flew, there were several that I flew when Bob lived in the LA area, so it would have been well before his Avanti and his Nats win.  Several of us in the LA area were well aware of Baron's ability to fly extremely good patterns.  I was anxious to fly one of his airplanes as was at least one other previous Walker Cup winner.  We had much the same impression that you just wrote about.  I was glad to get the things on the ground in one piece, not doing anything more than a couple of loops.  Our consensus was that Baron had a way to trim his airplanes that somehow suited how he flew and he was extremely good at doing so.

Keith

Whew!  Thanks for posting that, Keith.  I was afraid to fly my own airplanes for months after my experience with Bob's.  Felt certain I had had 
a brain hemorrhage or something!

Just kidding of course, but Boy was that a weird experience.  Probably the strangest stunt flight I ever had and to this day have no explanation why or how such outstanding patterns could be flown with it by Bob no matter how many practice flights he had.  Very interesting also that we almost certainly flew two different airplanes both of which affected us in the same way.  I had absolutely no idea where I would have started if I had been asked to re--trim it to suit myself.  That day I simply thanked him for the flight and said I wasn't comfortable trying to fly a pattern with another person's airplane with which I didn't feel comfortable.  As I recall we had no conversation about the details of my reluctance and he didn't appear to have taken any offense.

Too bad we've lost Bob and can't have him participate in this chat.  We all could probably have learned something in both directions!

Hugs to the tall blonde!
 

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #18 on: September 15, 2020, 03:50:11 PM »
For what its worth, I just started the trimming process on my first new electric profile, Circulas 46 IIe which is an all in-line model. I was trying to get 5.3 second lap times. I started out at 5.8 second laps, though slow it flew decently in level flight with only minor hunting. But once we progressively started to lower the lap times (increase the speed of the plane) the hunting became more pronounced with each increase. Once I got the plane to fly at 5.3 second laps it was very difficult to maintain level flight due to the hunting. Also when the motor stopped the plane floated and was difficult to control on landing.

I knew that the C/G needed to be further forward than a conventional IC plane. I though I had it far enough forward. For whatever reason, I decided to move the C/G further forward along with moving the leadout forward. Sure enough as I incrementally move the C/G and leadouts forward the hunting started to disappear and I had more control during the landings.

The chord dimension at the wing root is 9.25" from leading edge to trailing edge. The C/G is at 6.75" from the trailing edge with the C/L of the leadouts at 5.0" from the trailing edge, a difference of 1.75". I still want to experiment with moving the C/G even further forward.

Is this a symptom of an all in-line design?. I don't think so. I think its more related to be an electric model and is certainly different from a conventional IC model.


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Online Mike Alimov

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #19 on: September 15, 2020, 05:33:58 PM »
... it was very difficult to maintain level flight due to the hunting. Also when the motor stopped the plane floated and was difficult to control on landing.
...
Is this a symptom of an all in-line design?. I don't think so. I think its more related to be an electric model and is certainly different from a conventional IC model.


Dennis

Agreed, this likely has nothing to do with an inline layout.  I've built a few and they tracked dead level.
I don't have specifics on your airplane, but assuming conventional 46-size and shape wing, you're roughly at 18-19% MAC for your CG location.  I think it's a pretty good location based on what we fly around here.  Without substantial changes (installing a larger and longer tail - unlikely...), moving CG back is not feasible. 
Many planes are being "designed" for electric propulsion simply by converting the motor mounts on old designs, maybe along with CG/balance considerations (longer or shorter nose).  We forget that we no longer have a piped beast spinning a heavy prop at some 12k RPM.  Most electrics run much slower than that (many at < 10k RPM) and spin much thinner, lighter propellers.  Thus, the gyroscopic stabilizing effect of the prop is greatly reduced, and needs to be compensated with something else.  Igor, for example, dramatically increased horizontal tail area.  Paul moved CG forward quite a bit.
So there you go, yes, you can't trim electrics to the same numbers as IC-powered ships.  The principles remain the same, but numbers are different.
Now, I'm not defending an in-line design (although have been a proponent of it for years).  Igor laid out sound reasons why our planes cannot be totally symmetrical if pulled by a single propeller. 

And when it comes to hunting, other factors play a role - unintended stab and motor incidence (even 1 degree off is huge), stab leading edge radius and airfoil, etc.
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Offline TDM

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #20 on: September 23, 2020, 07:34:36 PM »
I had a discussion with Windy Urtnowski, about the in line setup, when I laid the design for Revolutions . He did in fact described the exact same characteristics of the flight of a plane with in line design that he built in early 1990 Cardinal that he said he hated the way it flew. I will not repeat that because you have already did describe it already basically saying the same thing different ways through this thread.
The think with in line layout of stunt planes is that the elevator placement which is always flying in the wing wake and this makes tracking a chore. This can be trimmed out with the CG far forward from a natural normal position. It is true that as soon as the plane is turning the response is even and the wake is outside the elevator region but as soon as you return to straight line flight the tracking problem will return. So the plane will also be trimmed very nose heavy and will take heavy impute to make it change direction.
Windy also said the Tigercat had the best handling lock and tracking of all his designs and he attributed it to the high degree of offset between the wing center line and the stab position. He said that as this distance increased and the stab was flying in clean air the better the plane tracked turned and staid locked in to flight.   
Revolutions is not an in line design and the turn between outside and inside as far as I can tell is equal and it is actually ridiculous easy to fly model it tracks nicely it turns stops and tracks like a beast and is is calm like a baby in the loops.
That being said there is the feel that every pilot likes and is searching for. Some like the way in line planes feel some like the feel of the other classical feel. One thing is for sure that no real life planes have the motor wing and tail in line, they all have the elevator in clean air as much as possible and it is even with dihedral in the elevator to make sure the plane is smooth predictable and tracks. 
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Offline Dave Hull

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #21 on: September 25, 2020, 12:54:04 AM »
I've always been intrigued by the Jean Pailet Skylark (Flying Models, Dec. 1962) which was an in-line design. He said it had one flight peculiarity:  it did not fly well as originally set up with 1:1 controls. He had to change it to have much more flap movement than elevator movement, after which change, he said it flew very well. I wonder what contributed to that?

Dave

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #22 on: September 25, 2020, 09:12:27 AM »
I've always been intrigued by the Jean Pailet Skylark (Flying Models, Dec. 1962) which was an in-line design. He said it had one flight peculiarity:  it did not fly well as originally set up with 1:1 controls. He had to change it to have much more flap movement than elevator movement, after which change, he said it flew very well. I wonder what contributed to that?

Dave
Dave I can only guess that due to the far forward CG it required it became sluggish and needed more lift. I would bet that all in line setups are running forward CG to compensate for the hunt, that means slower pitch sensitivity thus more flaps, and a lot of deflection on surfaces to make them turn.
 
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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #23 on: September 25, 2020, 03:09:51 PM »
Let’s see
Current Nat’s champ Orestes Hernandez and second place Paul Walker fly in-line planes with E power
Current world champion, second, 4th all in-line planes
Criss cox top five flyer in-line plane
I have owned multiple in-line models with none of the effects described above

1988 and 89 Nat’s champ Jimmy Cassale in-line model

Please read the Yatsenko articles reference above about why the classic and all other Yatsenko models are in-line

The pattermaster stab sits at 2-1/4” above the wing. They require 1/4 to 3/8” down Elev for equal turning
( I have built 20 pm all trim the same)

Al Rabe also used high stab placing on His mustang and Seafury in order to have equal turns he used down elevator
 
Many above have opinions on in-line models after flying half flights
We need to hear from modelers that currently fly in-line models Paul Walker, Chriss Cox

I will agree that the high stab locks in after turns.

High stab placing require down Elev for equal inside and outside turning

The Yatsenko shark ( in-line ) turns the same on inside and outsides
Jose modesto

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #24 on: September 25, 2020, 03:31:59 PM »
A story about Bob Baron and the in-line Avanti. Mike Rogers one of the most accurate builders on the planet and best friend with  Bob  Baron Built a perfect Avanti (1984)
This model would not fly level  it would make you sea sick to fly or watch lol
Baron comes to flushing meadows park (nyc) and proceeds to fly Mikes plane as if nothing is wrong  perfect flights
Mike takes a few flights and it hunts up and down Lap after lap
The Avanti was a one man plane Lol
Jimmys Cassale  88/89 Nat’s winner ( in line) used the Baron Avanti wing and layout
Jose modesto


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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #25 on: September 25, 2020, 09:05:04 PM »
" The pattermaster stab sits at 2-1/4” above the wing. They require 1/4 to 3/8” down Elev for equal turning "

Id put a few degrees incidence , on the Strega at least . Used the P.M. Airfoil, aft . So the elevator root fairings mate , at neutral .

Seems to turn pretty even and tight . ( Ive just dropped a good P.D.P. 4 window S Tigre 60 in it , Tradition & Balance, mainly .
Though found the last SF 46 efforts id fitted the wrong to-big venturie , was cutting outta hard squares - to level inside .

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #26 on: September 26, 2020, 07:31:17 AM »
Did you build the Flying models Straga or the Brodack Straga
Neither has the PM 60 Big Jim Wing
The FM Straga has a shorter root and span than the BJ PM 60.
You have the PM plans by Mike Rogers  you have posted them
Jose modesto

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #27 on: September 26, 2020, 07:39:17 AM »
A story about Bob Baron and the in-line Avanti. Mike Rogers one of the most accurate builders on the planet and best friend with  Bob  Baron Built a perfect Avanti (1984)
This model would not fly level  it would make you sea sick to fly or watch lol
Baron comes to flushing meadows park (nyc) and proceeds to fly Mikes plane as if nothing is wrong  perfect flights
Mike takes a few flights and it hunts up and down Lap after lap
The Avanti was a one man plane Lol
Jimmys Cassale  88/89 Nat’s winner ( in line) used the Baron Avanti wing and layout
Jose modesto

Eric Viglione and I both built Avanti 60, a Dixon version of the original using a PM airfoil.  Both were all but untrimmable.  Mine went apeshit in the second corner of the hourglass and got creamed, Eric kept trying things on his for a few years more before giving up.
Steve

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #28 on: September 26, 2020, 12:14:47 PM »
Motor horizontal
  Vertical CG problem

Jose modesto

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #29 on: September 26, 2020, 02:14:55 PM »
Hi Steve,I still have that "kit" by Tom Dixon.  What changes would you make to it to make it "flyable".   D>K

   Take the Impact plans and cut away anything that is different?   And in any case, once it was "fixed" with a different airfoil and whatever other changes, there's no reason to think it has anything to do with or in any way flies like Baron's version. Although Baron also supposedly said he could fly 4 good flights out of 10 with the Avanti and 9/10 with a (*stock*) Patternmaster, which doesn't surprise me. Good thing he never had a Trivial Pursuit, I guess.

     We have an epic email thread going about boundary layer control devices, where at least some aspects of it involved trying to maintain flow over the flaps and elevators in all conditions. So, anything that puts a fat wedge airfoil stabilizer, with a sharp trailing edge, right in front of a thin elevator,  is about as diametrically opposed to that as you can imagine. That alone probably makes it (the original Avanti) impossible to trim it to fly level, never mind the rest of it.

     Brett

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #30 on: September 26, 2020, 08:13:25 PM »
Eric Viglione and I both built Avanti 60, a Dixon version of the original using a PM airfoil.  Both were all but untrimmable.  Mine went apeshit in the second corner of the hourglass and got creamed, Eric kept trying things on his for a few years more before giving up.

John Blanchard has an excellent flying Avanti with a K77 in it. He’s flying it this weekend in Tulsa and it doesn’t do anything wrong that we can see. I think it was built by Dixon originally so I’m not sure what’s different about it compared to a stock Avanti
Matt Colan

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #31 on: September 26, 2020, 10:59:46 PM »
Quote
Did you build the Flying models Straga or the Brodack Straga
Neither has the PM 60 Big Jim Wing
The FM Straga has a shorter root and span than the BJ PM 60.
You have the PM plans by Mike Rogers  you have posted them
Jose modesto

Mine is a Brodak ARC Strega . or was .

I did new stiff flaps , to the P.M. Chords . New Horns . New Tailplane to P.M. Plan . So it must be a Patternmastrega . !  :-\ :-X

Now youve had ' us ' up all night . As its been a cold snap . Reading the F.M. Casale Spectrum & B. B. Avanti s#!t .

Its the Stectron Columbia thats in line . He states its his ' best ship since the Spectrum III ' which is the white one , with the vertical fin on top . With the AVANTI wing . He states in the Text .
( Out with the ruler . Baron flew a ' Hallmark ' , at a world champs & one season . At least thats what it says on trhe wing . Wondering if Avanti & Hallmark wings are the same . )

To quote Baron in theFeb. 81 F.M. Avanti II artical ,  :P

" The only problem introduced by lining up everything in one line is that inverted flight requires a little more down control than we are used to on conventional planes "

assume thats ' top ' or is it ' bottom ' , in Bob Hunt speak .  :-\

A issue of hyper touchey ships , is they aint ' wrist steerers ' in the rounds , at least . Ive found - anyway .

A Fairly extended arm , with movement as much from the shoulder as the elbow - tracing the rounds . SEEMS YOU DONT LOWER IT ALLS THE WAY < GOING DOWNHILL > not untill your used to it, at least .  :-X

A flick of the wrist and the squares are been & gone , though . Still keeping the extended arm tracing the horizontal & vertical legs of the hard corner manouvers * though .

* ( Sexist term. no longer politically correct . Suggest renaming ' personouvres ' so gender neutral . )  VD~ mw~ :##

RIGHT , also gotout the Bob Hunt Thunderchief to get a 25 % copy & 400%'s of fuse etc , for a four foot . 25 FSR / FP IN LINE sucker . Maybe I might build it, perhaps.

Also gotta set of ribs cut for a 89 % P.M. for the ST 46 or FSR 40 . Keen to do a .25 size one or LJ though . WHERE does it ALL END .  >:(
Big Hurricane for Stalker 76 requires the attentions , and dithering on Flap Span / Configuration for repeat of ' 60 ' 72 in Mewgull . Likely half span , swept hinge , even % round fr & wing channel so flush .  :P

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #32 on: September 26, 2020, 11:04:39 PM »
Back Bits and wire bits .



Most Bits, at 45 FSR Stage . Just wrecked a liner with swarf . Any FSR 45 P/L sets gladly accepted .  ???



This might not be ' in line ' , niethers a T Tail . The threads not about them either . But forgive & forbear . H^^

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #33 on: September 27, 2020, 05:02:32 AM »
84 WC Baron flew the Avanti  with the LJ 46 as his back up plane. Changed from LJ to Avanti two days prior to contest
Jimmy flew the Spectrum 3  To big to loud for WC judges

The Hallmark a Gene Shaffer design is a 46 size model. Much smaller than the Avanti
Bob Barron was not well physically and used the smaller Hallmark

Yes I should of included Columbia

The US team resided to paint their models the same and name them after the space shuttles
Paul named his Columbia

Good luck with your model That wing is thicker than the PM 60 and that leading edge to sharp. Hard to get it rounded

Watched jimmy fly his in-line ( Columbia)plane many times he was unbeatable in the north east circuit “
Great showman. The contest started the minute he walked into the park.  Greeted everyone. Well dressed hair well done
Great show Always and his wing over all were in attention.
He built six spectrum 3 one season and crashed 6 lol
The pipe planes were his demise

Jose modesto

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #34 on: September 27, 2020, 04:49:51 PM »
Did Ty's post vanish? Or is something wrong with my computer.  I see where Brett quoted Ty but not the original comment by Ty.

Ty, When Eric sees this thread he might have some ideas for that "Kit".  Matt is right that a few of them flew decently.  I have no doubt that I did something inept in building mine, but I do think more conventional designs are *far more forgiving* of minor goofs than my Avanti was.

I'm guessing that Eric will say move the stabilizer up and out of the downwash of the wing.
Steve

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #35 on: September 27, 2020, 05:16:15 PM »
Aside from the aerodynamics, I've found that an in-line design, the beam motor mounts interfere with the wing.  So the mounts have to be short, leading to weakness in fuselage front end.

Of course, an electric installation does not deal with maple motor mounts.
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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #36 on: September 27, 2020, 08:01:16 PM »
Did Ty's post vanish? Or is something wrong with my computer.  I see where Brett quoted Ty but not the original comment by Ty.

Ty, When Eric sees this thread he might have some ideas for that "Kit".  Matt is right that a few of them flew decently.  I have no doubt that I did something inept in building mine, but I do think more conventional designs are *far more forgiving* of minor goofs than my Avanti was.

I'm guessing that Eric will say move the stabilizer up and out of the downwash of the wing.

I asked John today about his Avanti. His leadouts are 1/4-1/2” below the centerline of the wing. And the tail is a fully tapered unit without the step between the stab and elevator. Seems like that’s what it took to get it flying decent
Matt Colan

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #37 on: September 28, 2020, 01:10:49 PM »
I asked John today about his Avanti. His leadouts are 1/4-1/2” below the centerline of the wing. And the tail is a fully tapered unit without the step between the stab and elevator. Seems like that’s what it took to get it flying decent

My ears were burning so I guess I had to reply to this thread. Heh.

Interestingly Matt, Randy's SV designs off set the leadouts in the tip also, not to that extent, but Vert CG might be helped here also. Not blanketing the elevator, on a stab/elev package that may already be suffering from blanketing from the short coupled in-line wing isn't a bad idea either... so I can't argue with your friend John's modifications, they sound in the right direction. You ever draft an 18 wheeler? There is a sweet spot, and a rough spot, and a dead spot. I think that is what is going on here, the stab is somewhere inbetween the rough/dead spot, distance wise from the wing.

One thing I noted in the Dixon release of the "last Avanti" that Bob never published, is that it the abrupt departure from controlled flight at odd moments is speed specific. I found the faster you fly it, the harder it gets to fly accurately. Slow it down and its not as bad, which I thought was really weird at the time, but sorta put me on to the problem. Flying it slower gives the air more time to normalize behind the wing, or at least the elipse of disturbed air is a different shape/distance back from the wing... I dunno, without a wind tunnel and smoke its all hangar talk.

I hate to theory-craft (but isn't that what we all do?) If I had to guess, I think that the wing wash from the super thick blunt Avanti 60 airfoil is blanketing the rather short coupled in-line stab/elevator at faster speeds. Add to that, the Avanti 60 stab wouldn't be my first choice in how to make a modern stab...

If I were to ever build another, and wanted to keep it an in-line design I would stretch the tail moment out to 18", and build the stab flat without that odd airfoil shown in the Avanti 60 plans and stretch the stab chord another 5/8" for obvious reasons, plus reducing the stab aspect ratio. As long as its no longer an Avanti and not trying to qualify for any Nostalgia events, might as well fix that crazy thick wing while your at it, and use a GeoBolt airfoil. There ya go, now you have an in-line Bear Nobler without the stab fences, that should work great.  LL~

FWIW, I've also built a stock Patternmaster and it's a totally different animal... MUCH better plane, if you just took the PM wing to stab config with Avanti aesthetics, and not in-line, it would probably fly great... oh wait, it did!  ;) With modern power it would be almost as good as anything. (though I would re-think the thin PM flaps, they tend to flex or warp easy. Layer up with carbon maybe?)
EricV


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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #38 on: September 28, 2020, 03:08:57 PM »
There ya go, now you have an in-line Bear Nobler without the stab fences, that should work great.  LL~
Without the stab fences, how are you going to keep the neighbors kids from cutting across your elevators?
I am going to put "No Hunting" signs on my next set. LL~

Ken

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #39 on: September 28, 2020, 11:14:48 PM »
Quote
That wing is thicker than the PM 60 and that leading edge to sharp. Hard to get it rounded

OH NO ITS NOT ! .  S?P

Did you take any photos of Gene's Hallmark ? ( One of the ' on the brain ' ships, here . )

Thinking ( a few random thoughts ) these ' In Line ' designs seem to go for the ' Trapezoid ' or ' wedge ' Tailplane & elevator .

Maybe the angle of the top surface , in rounds , is NECCESARY ! to the concept for stability . ( same as the ARC Strega set up . ( not mine ) ) .

-----------------------------------------------------------------------------------------------------------------------------------------------------------------

The T Tail , as Im doing a bit of renovation . This and the strega are both accurate to fly . The immediate impression with the Whirlwind is the tail cutting through its own clean air . so firm & accurate control modulation .

Lastly , a THING showing a 1/4 Sq L.E. with 1/16 sheet ( at 400 % there ) with a radius or two .

Even with the Rad. starting at the front of the 1/4 Sq. ( rather than 1/16 th back, as shown , you get a fair radius. Throw a circle template on and try it .

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------

Will trow some drivle on the P.M. Thread ( you can edit first post and acces heading , if ya wanna loose the typo .

Would be good to see L J templates pictures on graph paper , and other drawings . To promote the breed .    H^^






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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #40 on: September 28, 2020, 11:16:28 PM »
Note the TAILPLANE ( & elevator ) section . Seems Casale thought highly of this version, in retrospect .


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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #41 on: September 29, 2020, 08:45:53 PM »
Just a few late remarks concerning what has been said above:

1) Because of P-factor, gyroscopic precession, vertical c.g.'s, etc., NO plane is symmetrical, and that includes "in-line" models. Trimming and design variances are necessary to achieve near symmetrical behavior, even in in-line planes. landing gear vs raised-tail drag have to be balanced with precession, for instance.

2) I don't know what cylinder head location has to do with anything but c.g. height. It's the prop clearance that matters. For in-line planes, you need longer landing gear to accommodate equal prop diameters. I had to put ungainly wheels on or re-design my landing gear legs to accommodate the larger prop that finally evolved on my own in-line design.

3) From what some of you have remarked about Bob Baron over the years, it seems that he had an incredible ability and probably preferred  or could tolerate twitchy handling characteristics that few others would like. I wish I'd talked to Bill Netzeband about that, but it never came up in our chats.

4) We've had many discussions about adding a degree of positive incidence to the horizontal stab to achieve good flight characteristics and stop "hunting." That fits with the idea of deflecting the elevator downward in what we have come to call conventional designs. This is related to the upward pitching moment caused by tail drag for raised tails.

5) The early post about moving the cg and leadouts forward is probably an example of just lengthening the tail moment arm to tame the level flight behavior. It may have also profited by putting more wing area behind the c.g. to resist pitch changes or adding rotational inertia. This is probably more of a "band aid" measure, since the cg should be placed relative to the aero center of the plane in the design phase. Ideally, moving the cg any great amount for trimming is sort of the tail wagging the dog. Flap size and deflection add into this.

6) I think that most probably trim their planes to fly differently inverted and upright and just don't notice it, since the wrist may not feel the same giving up vs. down. So symmetry of flight behavior in those regimes may be felt differently by different pilots. Do we, for instance,  really prefer perfect control symmetry (equal up/down elevator for equal handle input? I'm not good enough to know.

Anyway, I see advantages to both main types of thrust-line/wing-chord/stabilizer arrangements that can be made to be harmonious, probably by similar amounts of designing and trimming. I really prefer shorter landing gear and less turbulence on control surfaces in level flight. So you can guess my preference. Of course as soon as flaps deflect, one's best compromise (like Ted's rule of thumb on stabilizer area vs. wing area giving c.g. position) is necessary anyway.

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #42 on: September 29, 2020, 09:43:54 PM »
Note the TAILPLANE ( & elevator ) section . Seems Casale thought highly of this version, in retrospect .

   Good for him, but there is a 100-ish post email thread where numerous national champions and NATs high finishers where, among other things, we are trying to *prevent it* from working like that with various boundary-layer-altering gadgets.

   A very great deal has been learned about this sort of thing in the last 35-40 years.

    Brett

Offline Ken Culbertson

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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #43 on: September 29, 2020, 10:28:05 PM »
6) I think that most probably trim their planes to fly differently inverted and upright and just don't notice it, since the wrist may not feel the same giving up vs. down.
I am going to get roasted on this one.  Thank you for saying what I have believed like forever.  Much is said and written about "muscle memory".  Your brain learns a pattern and commands the muscles to do something.  It doesn't care much how much up you used on an inside when it learns how to do an outside loop.  I don't discount those who insist on equal movement, maybe they need it, and many of them would clean my clock in a contest but I simply don't need it.   My brain got trained early to follow that imaginary projection of the maneuver and it gives it whatever it takes up or down to achieve it.  That does not mean that you don't need to trim to get the plane as equal as possible, you just don't make it the Holly Grail.  IMHO the goal should not be to have a plane that turns equal both directions but one that you can turn equal both directions with the same effort.

Ken
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Re: engine, wing, elevator-stab center line; why not in a straight line?
« Reply #44 on: September 29, 2020, 10:55:47 PM »
We used to ' hang it on a line ' , sorta sumersult .

Rotate about 5 to 8 foot diameter loop . The old profile pommy version of the peacemaker . / Flite Steak . And OTHERS .

General observastion was if theyed go around 1 1/2 times , they might work , if the went round three , they were o.k. , if five , not bad at all . some'd go round indefinately . Till the line jammed .
Combat Wings generally . They might buck and wallow, perhaps . But if they held the lines tight & instantly reverse or exit , it wasnt an issue , for thet. Combat .

Intresting the Muscle Memory .

Kieth'd asked if the T Tail did a initial reverse pitch .

Id thought Id noticed it on the first flight or two . Seems improbable , but a small reverse flick / twitch of the wrist mayve been developed straight off , for straight corners .
not that youd notice of believe it, flying it . But cant see it dosnt feature .

Horses for courses . looked at the Columbia Tailplane . the Inline Job . Thats the same depth elevator & tailplane ( thickness ) .

I dont belive theres a ' one solution fits all ' , but differant combinations , variables & trims . With some overiding general princaples .  :(

If youve seen a 6 inch wake , from a 60 foot schooner , doing 5 to 8 knots . Where some twelve foot runabouts disturb more than there width for metres aft , you see all things arnt equal .

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