Not one word was changed

[RC Storick]

I don't care I just re posted verbatim Bills writings. The peanut gallery started bashing.

[Doug Moon]

I don't care I just re posted verbatim Bills writings. The peanut gallery started bashing.

You knew if you posted the article this very thread would happen.

History, and a ton of other threads about this same topic, for the past several years
tells us when posts are made stating BC position matters or doesn't matter there will
be endless arguments about it.

The conclusion we have some too over the years is some say it doesn't matter and some say it does.
Ok.
Neither are changing their minds about it.
So, with that in mind, what is the point of this thread?

[RC Storick]

Doug you said you never read it. So I posted it for you.

[RC Storick]

I will not lock this, I will just delete any ignorant responces .

[Steve Helmick]

I will not lock this, I will just delete any ignorant responses.

 Fixed it for ya...

Robert, I think you're actually very close to doing what everybody does, in actuality. Including Ted and Brett. However, if you're going to mount the BC at the CG, you really should figure out where the CG should be relative to the entire wing, not just the root chord. There are various ways to get it done; some don't even require much math at all. As I see it, what you're doing could just as well be done by TLAR. Everybody is going to be adjusting CG and LO locations to make it work, but the engineering staff is merely trying to get closer before the flying and adjusting begins. I doubt if moving the BC location 1/2" fore or 1/2" aft (of the CG) would be noticeable at the handle.   Steve

[Mark Scarborough]

If you're not trying to have working flaps, then just make up a bunch of different elevator pushrods of different lengths, to match whatever stations you can install the bellcrank at.

For that matter, if you do have working flaps, then instead of doing the usual bellcrank -> flap -> elevator linkage, go bellcrank -> elevator -> flap.

To really be conclusive you probably want to correct for the geometry change that Howard cited -- this could probably be safely neglected in a no-flap plane until the bellcrank was quite close to the elevator.  Ditto for a bellcrank -> elevator -> flap setup.  But the usual bellcrank -> flap -> elevator already has some pretty severe side-effects from the control geometry (as, no doubt, Howard's spreadsheet calculates) that would only get more severe as the bellcrank approaches the flap.

if the flaps were driven off the elevators, a person could make the elevator bellcrank pushrod different lenghts, without having to change the elevator flap pushrod,, given they are rigid enough not to introduce issues there

[Mark Scarborough]

I guess I wont have to re trim it judging from your experience

assuming it is in proper trim to start with, I think the answer is no you wont

[Tim Wescott]

if the flaps were driven off the elevators, a person could make the elevator bellcrank pushrod different lenghts, without having to change the elevator flap pushrod,, given they are rigid enough not to introduce issues there

That's what I was thinking.  And it wouldn't change the flap/elevator behavior as you played around with bellcrank position, and until you had the bellcrank halfway to the tail it wouldn't change the bellcrank/elevator behavior, either.

So, for the purposes of Sparky's experiment it would isolate any center of gravity effects from any jommetry-changing effects.

[Air Ministry .]

This isnt a debate then . 

[wwwarbird]

Let me say this while putting it anywhere will work. My SWAG is putting it in one spot will work in one state of trim. Moving it the airplane will have to be re trimmed for optimal flight.

 True, that is why we use adjustable leadouts.

[Trostle]

Let me say this while putting it anywhere will work. My SWAG is putting it in one spot will work in one state of trim. Moving it the airplane will have to be re trimmed for optimal flight.

 

Well, you have made it clear that your statement here is your opinion and your understanding of these toy airplanes of ours.

However, just to explain the other point of view  -- If there were two identical models, same weight, same power, same CG location, and the position of the leadouts are in the same location but the bellcrank in each is in a different location - either vertically or longitudinally or laterally or any combination of these positional components and the one airplane will "work in one state of trim", the other model will "work" and "feel" the same without any need to be "re trimmed for optimal flight".  So sayeth those who understand these things and also who understand how to construct a force diagram that illustrates all pertinent factors.

One thing to consider regarding IC engines where the weight of the full fuel tank may represent as much as 6% (maybe more or less) of the total weight at the beginning of a flight that is consumed during the flight and the fuel tank is generally somewhere between the engine and the CG, there will be no optimal leadout position for the entire flight.  Rather, the leadout position for a "well trimmed" stunt ship is a compromise to give the "best" "performance" (however one wishes to define "best" and "performance" or even "feel") throughout the entire flight.

Indeed, Bill Netzeband discussed bellcrank and CG positions in the article quoted at the beginning of this thread.  In another article in American Modeler, October 1962, Netzeband states that the "bellcrank has no effect on locating the CG.  Rather the bellcrank should be on the CG to prevent binding...  CG will always fall in line with the center of the line lead-out spacing during flight.  Locate hour leadouts relative to the CG to produce desired yaw angle for proper tug.....Next time a guy tell you to locate your CG forward of the BC or in front of the lead out, shun him.  He don't know the facts.  The CG comes first. all else is related to it.""

I think it only fair to further quote some more of Netzeband's writings since this entire thread was initiated with a rather lengthy Netzeband quote that in some places in this thread has been misconstrued to mean something else.  Yes, anyone can have their own opinion on this matter, but Netzeband's writings should not be twisted contrary to what he wrote.

Now, how long will this post be allowed to remain on this thread.  (I have now had my posts removed from this forum by two of the forum's best.)

Keith

[RC Storick]

This will not be removed because it was not a Smart A response it was your thoughts.

Next time a guy tell you to locate your CG forward of the BC or in front of the lead out, shun him.  He don't know the facts.  The CG comes first. all else is related to it.""


OK Try the bellcrank ahead of the CG let me know your findings. All I have tried to get across is if it makes no difference why does he make statements like ALMOST and CG because it doesn't make any difference? If it made no difference why didn't he say just that?

Once again I don't care where anyone mounts them, Its a reposting of his writings not mine.

[Serge_Krauss]

Next time a guy tell you to locate your CG forward of the BC or in front of the lead out, shun him.  He don't know the facts.  The CG comes first. all else is related to it.""


OK Try the bellcrank ahead of the CG let me know your findings. All I have tried to get across is if it makes no difference why does he make statements like ALMOST and CG because it doesn't make any difference? If it made no difference why didn't he say just that?

The bold face quote is meant to convey the principle that one should not "choose" a CG position to suit BC or LO positions. The CG is located solely for stability considerations and relates to the aerodynamic center (ac) of the whole apparatus only. First you create the stable plane, locating the CG where it must be located in order for the plane to fly controllably, with th desired degree of stability. Then you locate all controls and mechanisms to accomplish their functions without causing other problems (like unwanted yaw and roll).

"Almost" refers to those other things we've mentioned so often: control friction and wear, structural strength.

I believe that some here who think some of these things are just a matter of opinion should read carefully what Howard said, rather than skimming over it and "interpreting" it. Take it literally. You'll see that a couple interpretations implied by later posts haven't quite gotten his points. Tim also said that feel comes from other effects. Finally, as all seem to agree, forces change throughout a flight. We choose the best compromise trim. However, this does not change the basic point  about the bellcrank position. The balances of forces that control the plane are independent of it. The CF is not, and you'd better build the bellcrank post robustly enough. Don't confuse these things.

SK

[Tim Wescott]

Tim also said that feel comes from other effects.

Tim only said that first in this thread, and does not wish to take credit where it is not due.  Howard was the one who pointed it out in another thread; it came as an epiphany to me: http://stunthanger.com/smf/index.php?topic=33674.msg339076#msg339076.

[Tim Wescott]

<snip>

However, just to explain the other point of view  -- If there were two identical models, same weight, same power, same CG location, and the position of the leadouts are in the same location but the bellcrank in each is in a different location - either vertically or longitudinally or laterally or any combination of these positional components and the one airplane will "work in one state of trim", the other model will "work" and "feel" the same without any need to be "re trimmed for optimal flight".  So sayeth those who understand these things and also who understand how to construct a force diagram that illustrates all pertinent factors.

<snip>

What Keith said, except you have to carefully control for other things that may change with changed bellcrank location.  Given Howard's comment, I suspect the biggest culprit is changes in control system geometry.

Here's my stronger, shorter version:

If all else is equal -- weight, strength, friction and the exact relationship between line motion and surface motion, etc. -- then where the bellcrank is mounted relative to the CG cannot make a difference.

Not "does not".  "Can not".  Not without violating the laws of physics.  Rearranging the internal controls without changing any of the external qualities of the airplane cannot change the way it flies unless magic is involved, and the laws of physics rule out magic.

The fact that -- per various people's experiments -- moving the bellcrank does seem to make a difference can only mean that one or more of that "all else" must not be equal when you move the bellcrank position.  Like Howard*, I suspect it's the control system geometry that's either changing the flap to elevator relationship, or possibly that's changing the degree to which the controls tend to self-center under line tension.  I doubt that its friction.

* http://stunthanger.com/smf/index.php?topic=33674.msg339076#msg339076

[RC Storick]

Give it a brake

[Serge_Krauss]

It's interesting to me that the most recent posts have answered a direct question and clarified something entirely missed by everyone, but the only thing anyone found significant about them, and that includes by the person who actually asked the question, is that something has been posted about a subject they no longer want to hear about, but continue to harp about themselves. Well, I have good news for you. I'm outta here. If you don't care about what's been said, then you'll be relieved. If you really want to understand something about which you are unclear, then you'll actually read the posts for understanding and invest a little effort. Christmas leftovers await, but no visit to this thread again. Thanks for the ride.

[Trostle]

What Keith said, except you have to carefully control for other things that may change with changed bellcrank location.  Given Howard's comment, I suspect the biggest culprit is changes in control system geometry.

Here's my stronger, shorter version:

If all else is equal -- weight, strength, friction and the exact relationship between line motion and surface motion, etc. -- then where the bellcrank is mounted relative to the CG cannot make a difference.

Tim,

I know we are beating a dead horse here.  And you did a nice job of expressing what I was trying to say. I agree, you cannot move the position of the single bellcrank, all else being the same, without changing, even minutely, something in the control response because the geometry of the control system is changed.  Even if that single bellcrank is moved is very small increments, the angles of the pushrod/pushrods from the bell crank to the control horn/s change.   Thus there will be a change in the "feel" of the airplane, not because of the change of the bellcrank position relative to the CG but due to the geometry of the pushrod/s, control horn/s and the single bellcrank.  This minute difference in feel will probably not be detected for small changes in bellcrank position.  However, the more the bellcrank position is changed, the more that control system geometry changes and the effect on control response will eventually manifest itself to a noticeable difference in "feel" of the model unless other "trim" changes are incorporated.

It is interesting in the Williamson article where he changed the bell crank position from 6 inches in front of the CG to 10 inches in back of the CG, he used two bellcranks mounted on the bottom side of the fuselage.  The one bellcrank that was moved to the various positions was connected to the leadouts to the inboard wing.  The second bellcrank was permanently attached to the fuselage for this test and connected to the elevators of this flapless test bed.  Different pushrod lengths were used between the two bellcranks for the difference in the distances between the two bellcranks.  This resulted in the geometry of the bellcrank/pushrod/elevator horn remaining constant throughout his test program.  And as has already been reported, there was no difference in the way the airplane flew.

Keith

[Shultzie]

 
Wonder why I keep getting A CARTOON VISION OF A CAVE MAN TWIRRRRLLING' AROUND AND AROUND A ROCK THAT IS TIED TO THE END OF A LONG SINGLE STRING VINE?

[Howard Rush]

I was wondering how Windy got the notion that having the bellcrank in front of the CG is bad.  My hypothesis is that he took an airplane with the bellcrank at about 30% chord, then tried different CGs.  When the CG got behind the bellcrank, the plane got unstable.  Attributing this to CG position relative to the bellcrank seems to be a natural consequence of thinking that bellcrank location affects the airplane's dynamics or feel.     

[Brett Buck]

Ballancing line drag by CG position front of LO guide is perfect idea, but I affraid perfect only for speed and team racers ... what will happen if I fly overhead, gravity will lower the CG pull, line drag will be realtively stronger and model nose will look to me standing down on ground  ... something goes wrong here 

    This is where the subjective part comes in. The physics are unassailable, it's not a debatable point how the leadouts and bellcrank work, nor how the lines drag backwards. Bill's nomographs and LINEII tell the same story. There are some experimental results in the line drag equation, but it has proven out to be very close to right over the years in hundreds of cases.

    The subjective part is using the calculated line drag angle to set the leadout position. I think that's an ideal starting point that will let you get the rudder set to more-or-less neutral regardless of building variations. What anyone does with it beyond that is up to the pilot.

     Brett

     

[FLOYD CARTER]

On my next stunter, I'm not going to tell anyone just where the bellcrank is located. 

It's safer that way.

F.C.

[Mark Scarborough]

On my next stunter, I'm not going to tell anyone just where the bellcrank is located. 

It's safer that way.

F.C.

Floyd, you could mount it on the canopy,, that way you would not have to tell anybody

[Igor Burger]

  The physics are unassailable, it's not a debatable point how the leadouts and bellcrank work, nor how the lines drag backwards.

Right, physic is not debatable but theories based on physic are  And this is good example, that theory and the program are based on some presumptions, and if presumptions are not fullfilled, then theory could be proped, but its usage in such case is simply wrong, and this is clear example, this thery expects that the only aerodynamical forces are from line drag and forces to CG are only from centrifugal force. This is fullfulled only in case of speed models (or TR) flying in level, so the theory works well and also program is perfectly usefull in such case.

But stunt models have rudder, motor offset and we have also gravity since we fly also overhead, so while the thery and also programs are perfect tools, it usage on stunt model is simply wrong. Fortunately while that programe is not applicable its result still could be usefull (just because it is not applicable - measn the result could be also good    ... accidentally )

It is like misusing hammer and screwdriver, you can nail by screwdriver, and you can also convince screw by hammer, both will somehow work, but result is not always so perfect 

And I also see difference between slovak and english here ... if my model falls from sky because it looks down while it flies overhead, I use word which my dictionary translates to "wrong" ... not "subjective" ... or may be I am wrong subject :- ))))))))))))))))))))))))   

(hey it is end of year, little bit joking is OK I hope :- ))))))) ... HNY )

[Doug Burright]

This was kind of interesting...

I just built a 1/2A , A-7 Corsair II for another deal, and the plane is just a profile fuselage, with a flat wing. I maintained the scale outline fairly close - so that means the wing is significantly swept. I mounted the bellcrank pivot at about 1/4 of the root chord, but installed a leadout guide, far forward of the leading edge, because I felt that aft placement - where the wingtip is - wouldn't work. I wasn't sure why...but it just didn't look right. Now, it has a wire - with two little loops on it - sticking out, forward, from the inboard tip.

So... this thread started out as exactly the information that I needed to actually determine the optimum location for the control system on the A-7. Lots of the information provided is way above my pay-grade, but, I have yet to fly the plane, and see if my approximation will work. That's how I'm going to apply what I know about all of this. I'll keep you guys posted, too. This discussion has put another wrinkle in my gray matter.

[Douglas Ames]

This was kind of interesting...

I just built a 1/2A , A-7 Corsair II for another deal, and the plane is just a profile fuselage, with a flat wing. I maintained the scale outline fairly close - so that means the wing is significantly swept. I mounted the bellcrank pivot at about 1/4 of the root chord, but installed a leadout guide, far forward of the leading edge, because I felt that aft placement - where the wingtip is - wouldn't work. I wasn't sure why...but it just didn't look right. Now, it has a wire - with two little loops on it - sticking out, forward, from the inboard tip.

So... this thread started out as exactly the information that I needed to actually determine the optimum location for the control system on the A-7. Lots of the information provided is way above my pay-grade, but, I have yet to fly the plane, and see if my approximation will work. That's how I'm going to apply what I know about all of this. I'll keep you guys posted, too. This discussion has put another wrinkle in my gray matter.

Get with Bob Reeves on leadout/ bellcrank placement for a swept wing. He built a few FJ Furys for Carrier that fly great.

[RC Storick]

It is like misusing hammer and screwdriver, you can nail by screwdriver, and you can also convince screw by hammer, both will somehow work, but result is not always so perfect 

  I like this, this is engineering. 

[Bob Reeves]

Get with Bob Reeves on leadout/ bellcrank placement for a swept wing. He built a few FJ Furys for Carrier that fly great.

Carrier is a little different on bellcrank placement especially with a line slider. Bellcrank has to be well behind the CG, centrifugal force will move the leadouts when the slider is released. For the high speed leadout position I use LineIII and place them where it tells me. To find the MAC and CG I cheated and used an on-line calculator for a swept wing. End result worked great. No engineering other than make use of what others already had figured out.

[BillLee]

I sure get the impression that some here think

"Engineering is to ignore physics."


Any "engineer" that ignores the "physics" of the problem may end up with a solution, but .... some expressions apply:

Kludge
Rube Goldberg
Unintended consequences
Unrepeatable unexplainable results

[RC Storick]

I sure get the impression that some here think
"Engineering is to ignore physics."

They are still working on gravity..  

Physicist Questions Gravity's Existence

by Brian Thomas, M.S. *

Does gravity exist?

While few would deny that objects attract at-a-distance, some physicists are questioning whether or not this universally observed effect is caused by a stand-alone force called "gravity." The root causes of this well-established law are still not understood by science. If something this basic can be called into question, how should this affect one's confidence in other widely-held scientific claims like "evolution is a fact"?

In a landmark paper that is causing a stir in the world of theoretical physics, University of Amsterdam string theorist Erik Verlinde provided a totally new perspective for understanding the effect that has been called gravity. He is convinced that it is not an independent force at all.

If it's not, that would be good news for scientists such as famed cosmologist Stephen Hawking who have spent lifetimes trying in vain to merge the fundamental formulas that express gravity and electromagnetism into a single "theory of everything."

Instead, Verlinde posits that gravity results from objects that had been stretched apart from one another and are just relaxing back into more "comfortable" positions. In this view, "Newton's law of gravity emerges in a surprisingly simple fashion."1 He told The New York Times, "We've known for a long time gravity doesn't exist. It's time to yell it."2

Reactions to Verlinde's proposal provide an interesting contrast to the reception provided to certain others who've been willing to examine scientific presuppositions. In countless conversations around the world, people with sincere questions about evolution's particles-became-people story have been accused of being as ignorant as someone who would question gravity. Now, Verlinde has actually questioned gravity and yet is being treated to serious consideration rather than demeaning personal attacks.

The difference may be that those who have heard of Verlinde's pioneering work are actually thinking about what he has said, instead of dismissing it before even giving it a serious look. Some physicists believe that Verlinde's model is brilliant, while others admit they do not understand it or do not believe it will prove accurate. But in all cases, they are considering Verlinde's proposal.

The formulas used to defend his thesis are elegant and persuasive. In his paper--posted on a Cornell University website that houses technical papers and peer comments--Verlinde used the analogy of a long, loose strand with one end tethered to a fixed point to illustrate his concept that gravity is just a byproduct of thermodynamics.1

Imagine the strand so loose that its shape randomizes into something like a wadded-up spaghetti noodle. Then somebody gathers the wad and straightens out a portion of it by pulling it away from its attachment point. After it is let go, the strand randomizes again, its increasing crinkles causing it to shrink back toward the object to which it is attached. In a similar manner, the apparent force drawing objects together is just the effect of the space between those objects randomizing, curling up, and pulling inward.

His theory has already been applied by other physicists to successfully solve certain problems in physics.3 Whether or not gravity is an independent, fundamental force in the cosmos or just the consequence of thermodynamics, as Verlinde and a growing cadre of physicists are thinking, the fact that the basics of a phenomenon so universally observed as gravity are still being discussed seems remarkable in the face of all the bluster that science holds all the answers.

A physicist has provided a radical re-think on the fundamentals of gravity, accompanied by sound reason and solid observations. And physicists are listening. In a profession dedicated to finding accurate explanations, it should hold equally true that when a biologist provides a radical re-think of Darwinian origins--also accompanied by sound reason and solid observations--his or her case should also be heard.

[Trostle]

This was kind of interesting...

I just built a 1/2A , A-7 Corsair II for another deal, and the plane is just a profile fuselage, with a flat wing. I maintained the scale outline fairly close - so that means the wing is significantly swept. I mounted the bellcrank pivot at about 1/4 of the root chord, but installed a leadout guide, far forward of the leading edge, because I felt that aft placement - where the wingtip is - wouldn't work. I wasn't sure why...but it just didn't look right. Now, it has a wire - with two little loops on it - sticking out, forward, from the inboard tip.

Doug,

Let's take your example a step further and it may make your experience even more "interesting".  When you take your 1/2A Corsair, look at the chord at the mid span, half way from the fuselage to the tip.  Measure that chord and determine where the 20% position is.  This places what should be a good approximation of where your balance point is on the longitudinal axis of your model.  If your model flies well (like really stable), your actual balance point might be slightly ahead of that 20% position.  Now that you have determined the balance point on your longitudinal axis, at the inboard wing tip, a desirable center of your two leadouts would be around 3/4 inch" (maybe slightly less) behind that CG position assuming the span of your model is around  24 to 28 inches.  Depending on the LE sweep of your A-7, that would still likely put your leadouts slightly ahead of you tip LE.  (Notice, none of this has anything to do where you have the bellcrank mounted.)

Let us know what you find.

Keith

[RC Storick]

Once you find it fly's there, move that bell crank forward and inch in front of the CG and let us know you findings. Must be gravity  

[Derek Barry]

I have not read through all of this topic. So, what exactly are you guys arguing about? Whether or not the bellcrank location has anything to do with trim and or flight performance? Sparky, are you saying that it DOES matter and the other guys are saying that it DOESN'T?

Just trying to see what all the hubbub is about.

Derek

[RC Storick]

 It don't mater.. Mount it on the rudder but please let us know how that worked out.

[Mark Scarborough]

Once you find it fly's there, move that bell crank forward and inch in front of the CG and let us know you findings. Must be gravity  

by his description,, the bellcrank is already ahead of the CG,, it its at 20% at the root,, the CG will be behind that because of the sweep

[RC Storick]

What I am getting at is mount it anywhere and move the leadouts to where it works best. Now move the bellcrank. If you have to re-trim the model It does make a difference. I am not sure why this concept is so hard to grasp.

[Tim Wescott]

I have not read through all of this topic. So, what exactly are you guys arguing about? Whether or not the bellcrank location has anything to do with trim and or flight performance? Sparky, are you saying that it DOES matter and the other guys are saying that it DOESN'T?

As far as I can tell the argument is over whether the bellcrank position relative to the CG is what matters or if what matters is the bellcrank position with respect to the other mechanical bits of the plane.

The engineers in the crowd seem to feel that toy airplanes are going to obey the same laws of physics as every other object in the known universe, and are trying to hold onto this point.

[Serge_Krauss]

What I am getting at is mount it anywhere and move the leadouts to where it works best. Now move the bellcrank. If you have to re-trim the model It does make a difference. I am not sure why this concept is so hard to grasp.

Holy Cow! What am I doing back here again?! Ah, well...

This would be a very good point, IF it were not for needing to configure the control horns to make the plane the new bellcrank position is servicing to be the same plane in which the original functioned. The change of position, as we've said all too often does influence leadout bend/friction, control geometry, and sometimes structure. As long as the flaps and elevators are working with the same motions and mechanical advantages, the bellcrank position can be wherever you want it. If you find a trim change, you'll be able to trace it to control changes, rather than where the bellcrank is. Fortunately, needed adjustments aren't complicated.

The post on gravity is interesting, and I doubt that any reasdonable scientist would not give it its due. For things like gravity, we've searched through numerous theories and models. Some are interpretable among themselves. There are often more than one way of modeling natural phenomena. Some involve what simplifying assumptions to choose, and some are matters of perspective. This article seems to be written by someone with an ax to grind; there really shouldn't be an argument, and that a new perspective or model has surfaced has absolutely no relevance to another theory describing phenomena and actions we see unfolding every day. I'm happy to read about it, but certainly do not see any reason for anyone to have allegedly been upset by it.

For Igor: surely it's complex, especially when we elevate the plane along the hemisphere. However, design and trim are a big set of compromises, and for a given aircraft, once that total compromise is chosen, you will have it, wherever that silly gadget is located.

SK

[Steve Helmick]

What I am getting at is mount it anywhere and move the leadouts to where it works best. Now move the bellcrank. If you have to re-trim the model It does make a difference. I am not sure why this concept is so hard to grasp.

We're not sure why the concept is so hard to grasp either. There is certainly some point where the friction at the LO guide is going to be a big negative, but someday, somebody will invent a ball bearing leadout guide. Then, it won't matter (at all) where you put the bellcrank pivot.

Hang any model by the LO's and note the angle of the fuselage. Add 10 lbs at the CG, and note the angle of the fuselage. Add 10 pounds at 6" forward and 10 lbs at 6" aft of the CG at the same time. Report back.  Steve

[Trostle]

Once you find it fly's there, move that bell crank forward and inch in front of the CG and let us know you findings. Must be gravity  

Robert,

Looking forward to your findings (and by others) when you do your test bed that you said you will or might have at the Nats.  Unfortunately, I have other pressing things on my schedule in July so will not be able to witness what I think will be a total surprise to at least one individual, maybe more.

(Actually, he will be able to move the bellcrank several inches in either direction, assuming there is structure to do so and the experience will be the same.  There will be no difference in the way the airplane flies other than there may be a bit of a sluggish feel due to the friction (almost negligible) through the leadouts.  This has been tested and demonstrated before.)

Keith

[Tim Wescott]

This would be a very good point, IF it were not for needing to configure the control horns to make the plane the new bellcrank position is servicing to be the same plane in which the original functioned.

So, use that English feller's 'lectronic bellcrank (what's his name??), a single leadout guide so that leadout jommetry doesn't mess things up (yes, a single leadout guide will cause other problems -- we're doing things in the name of science here!), and always point the center of the bellcrank toward the leadout guide, again so that we don't mess up the jommetry.

The electronics and bellcrank mount alone should be worth the price of admission.

[Howard Rush]

Once you find it fly's there, move that bell crank forward and inch in front of the CG and let us know you findings. Must be gravity  

Not that it would convince you of anything, but the airplane below operated nicely with the bellcrank in front of the CG.  I built it with the bellcrank at the standard Impact zero-fuel CG location.  This particular airplane flew best with the zero-fuel CG .3 to .4" aft of that, so the last quarter of the flight was with the bellcrank ahead of the CG.  

[RC Storick]

My point Howard exactly "This particular airplane flew best with the zero-fuel CG .3 to .4" aft of that" If it flew best there wouldn't it make sense to try and keep it where it fly's best? If it made no difference why would it fly best in one spot and not in another? Just think about it.

Now if it flew best there what would it have flown like behind the CG ? Should make no difference according to the physics right? It also means no trim changes. But if you had to make a trim change did it make a difference? Any added weight or movement of weight changes the airplane characteristics , So would it matter? I say yes! You say no.

[RC Storick]

Robert,

Looking forward to your findings (and by others) when you do your test bed that you said you will or might have at the Nats.  Unfortunately, I have other pressing things on my schedule in July so will not be able to witness what I think will be a total surprise to at least one individual, maybe more.

(Actually, he will be able to move the bellcrank several inches in either direction, assuming there is structure to do so and the experience will be the same.  There will be no difference in the way the airplane flies other than there may be a bit of a sluggish feel due to the friction (almost negligible) through the leadouts.  This has been tested and demonstrated before.)

Keith

I will make it in the extremes so some not as sensitive as I can feel it. Normal position and 3 inches either way. Plane will be trimmed in the normal position and not changed in the others (AT ALL). If the ones who do get to fly the test bed can't feel it, I don't know what to tell you. But from the outside you will certainly see it in a hard corner. It will all try to line up with the centrifugal force applied by the hemispherical flight path. GRAVITY.  

I know I will add a wiggly rudder to counter act this force. (Just a joke)

I think then people see the wing hinge most believe it all in the tip weight. Well my thoughts and findings its mis aligned Lead out's , tether , tip box locations. Anyone can think anything and put them anywhere. I just try to edge my bet.

[Howard Rush]

My point Howard exactly "This particular airplane flew best with the zero-fuel CG .3 to .4" aft of that" If it flew best there wouldn't it make sense to try and keep it where it fly's best? If it made no difference why would it fly best in one spot and not in another? Just think about it.

Now if it flew best there what would it have flown like behind the CG ? Should make no difference according to the physics right? It also means no trim changes. But if you had to make a trim change did it make a difference? Any added weight or movement of weight changes the airplane characteristics , So would it matter? I say yes! You say no.

I was refuting Windy's assertion that the bellcrank can't be ahead of the CG, which you were offering as evidence that bellcrank location affects something about how the airplane flies.  Everybody agrees that adding or moving weight changes both the airplane dynamics and the yaw angle for a given leadout position, which is what Netzeband and Line III calculate (for a given set of assumptions). 

[Steve Thomas]

Just to extend the discussion: how about a hypothetical model with control horns extending above and below the flaps/elevators. Flexible leadouts enter the wing at the normal place, but are routed via hypothetical very-low-friction control runs, and attach directly to the control horns.  We then have a control system which works in the normal manner, but has no bellcrank at all.  Will the model still fly normally (considering we have hypothetical very-low-friction control runs)? What does this then say about the bellcrank/CG relationship?   

[RC Storick]

I was refuting Windy's assertion that the bellcrank can't be ahead of the CG, which you were offering as evidence that bellcrank location affects something about how the airplane flies.  Everybody agrees that adding or moving weight changes both the airplane dynamics and the yaw angle for a given leadout position, which is what Netzeband and Line III calculate (for a given set of assumptions).  

In your case its not much ahead of the CG. The Mustang in the video was way more. The airplanes we fly have different forces applied than real aircraft. Who knows in your case it might ease the control load a small amount. I don't know and NO ONE knows for certain what is happening under a 10-15 G turn flying in a hemisphere in changing winds and loading from one line to the next.

It's as magical as building two airplanes exactly the same with the same power trains and them not flying exactly the same. Must be magic Voodoo sorcery or some mystical force you can't Pie times radius square .

[RC Storick]

Just to extend the discussion: how about a hypothetical model with control horns extending above and below the flaps/elevators. Flexible leadouts enter the wing at the normal place, but are routed via hypothetical very-low-friction control runs, and attach directly to the control horns.  We then have a control system which works in the normal manner, but has no bellcrank at all.  Will the model still fly normally (considering we have hypothetical very-low-friction control runs)? What does this then say about the bellcrank/CG relationship?  

I would not want to try this because it would be tethered in a different location other than the center line of the airplane. These experiment's have been tried on Boom aircraft and it also has been found the tether location worked best in the center line of the plane. The worst place being mounted inboard of the first boom.

[Dave_Trible]

Just to extend the discussion: how about a hypothetical model with control horns extending above and below the flaps/elevators. Flexible leadouts enter the wing at the normal place, but are routed via hypothetical very-low-friction control runs, and attach directly to the control horns.  We then have a control system which works in the normal manner, but has no bellcrank at all.  Will the model still fly normally (considering we have hypothetical very-low-friction control runs)? What does this then say about the bellcrank/CG relationship?   

This is not so hypothetical. Some of the very first controlline airplanes did just that.  However it was a way to worm around Jim Walker's bellcrank patent.  The lines ran through tubing with a large-radius 90 degree turn towards the tail.  The obvious problem was friction but nothing other than the lead out exit location would have mattered in regards to this discussion.  It's about CG/lead outs, not CG/ bellcrank.

Dave

[Howard Rush]

The airplanes we fly have different forces applied than real aircraft.

Well, then, show us what they are.  Let's see a free-body diagram.  Same goes for you guys with the book learning.  Stop the dad gum arm waving.  Sum the forces, sum the moments.