Leadouts

There have been many references made to the spacing of lead out guides lately. No explanations have been given why, so perhaps it's time to review the reasons for the desire to have them as close together as possible. I can think of benefits for both narrow and "wide", so please enlighten me, I'd really like to know!
Cheers!
Mo

>There have been many references made to the spacing of lead
>out guides lately. No explanations have been given why, so
>perhaps it's time to review the reasons for the desire to
>have them as close together as possible. I can think of
>benefits for both narrow and "wide", so please enlighten me,
>I'd really like to know!
>Cheers!
>Mo
My theory in favor of narrow spacing (or even over/under) is that with wide spacing, moving from full "up" to full "down" shifts the tether point, causing a yaw. Becomes a problem especially with combat planes and their violent maneuvers, going from lock to lock nearly constantly. (Hang it on the up line; hang it on the down line; repeat endlessly). Maybe stunt ships, with usually limited input, maintainng an even line tension, don't have this problem, I don't know.
--Ray

>>There have been many references made to the spacing of lead
>>out guides lately. No explanations have been given why, so
>>perhaps it's time to review the reasons for the desire to
>>have them as close together as possible. I can think of
>>benefits for both narrow and "wide", so please enlighten me,
>>I'd really like to know!
>>Cheers!
>>Mo
>My theory in favor of narrow spacing (or even over/under) is
>that with wide spacing, moving from full "up" to full "down"
>shifts the tether point, causing a yaw. Becomes a problem
>especially with combat planes and their violent maneuvers,
>going from lock to lock nearly constantly. (Hang it on the
>up line; hang it on the down line; repeat endlessly). Maybe
>stunt ships, with usually limited input, maintainng an even
>line tension, don't have this problem, I don't know.
>--Ray

Ron B.
F4Fguy

ANY control input, up, or down, loads the line causing the input,and unloads the opposite line, causing an effective change in lead-out position.The farther apart the leadouts, the greater the effect,and conversely closer spacing has less effect.

Another reason is that any unwanted yaw (from wind, turbulence, precession) also makes unwanted input to control system (like if you move the handle). Narrow spacing minimizes that input.

Here is a little something to yaw on:

Al Rabe uses a "wiggly rudder" so that when you feed in down elevator the rudder deflects outboard. This is to correct the model yawing its nose IN on down elevator. The theory (which I think is sound)for this is documented in volumes elsewhere so I don't want to re-hash it here.

Leadout position is another way of achieving a similar result. (I'm not saying it's as effective as the Rabe rudder but it has some effect). The further rearward you place the leadouts the more outward yaw will be produced, (imagine for example the ridiculous case of the leadouts exiting the model at the stab). So...... if you place the UP leadout forward and the DOWN leadout to the rear, there is a tendency for the model to fly with more equalised yaw during inside and outside manoeuvres.

I personally don't think it makes a huge difference but it's enough for me to have the up line at the front and the down line 1.5" behind it.

Cheers all Tim

Yes, counterballancing the gyro moment by moment from lines theoretically works, but if you try it, you come to 3 problems:

1/ We try to be as far as possible from Netzeband wall and it means small difference in line tension in maneuvers, so if you want ballance it by line separation, you will typically end up at very large sepration. Only then you have enough force to arm.

2/ That large sepratation wil make it sensitive to turbulen air. Side kick will make up/down input to elevator.

3/ If your front line is up line and you do not ballance the precession kompletatly (and it is not possible because yaw depends on pitching rate, while lift of evevator is not), then if you do a wanted input up, it will point your nose out (precesion), that will add even more up and that is postive feedback which ca make model instable od difficult to control precisely or even hunting.

Hello Igor!

If I take your reasoning further: I have been flying models with a normal belcrank whole my life. Front line is down. When I would swap to an inverted bellcrank after years of practise with this normal one, would I have to re-adjust my reactions when flying in the wind and turbulance to cope with the opposite yaw induced control movements?

Strange that I haven't read anywhere about problems with control when swapping from normal to inverted belcranck. Of course I don't read everything.... And especially not the Russian, Check or Slovak publications! Might be a language issue

See you!
Paul

I can send you some dictionary. I have French and also Dutch, so if you want learn Slovak language, no problem … but it is FAR more difficult then German/English/French language .

But … 90% of my models has front line down. I also always try both ways and I use that better (I do leadouts interchangeable). I cannot say that front down is always better and I cannot promise that it makes always difference. But typically I feel difference. It depends on how much throw you need for full deflection, feedback to lines and how much are leadouts separated.

Try to check your leadouts and if it is possible to exchange them, just try it, you will see if it is better or not.

Hallo Igor

Is that the reason, why some pilots have the leadouts above each other?
What is your experiance with having the leadouts above each other and what would you say is the minimum spacing so the connectors don't touch each other?

with kind regards
Frank Wadle
Germany

Real men don't need instructions!

Frank Wadle

Frank, I never tried such configuration, so I can not say how well it can work, but theoretically you will have same problem with roll. Every input makes a roll to some extend and that will make similar unwanted input to control system. We have typically more tip weight then necessary, so theoretically the up line should be down in that case.

But there is also another problem - roll transfers to yaw and yaw back to roll. So if you do not solve precession and you have lines one over the other, and you model yaws, the that yaw is converted also to roll and you have still some influence

But anyway, you are definitelly right, the key is to keep lines as close as possible and/or to have linkage as slow as possible (or practical).

I am personally very confortable with slow controls and front line down making some more stability - it is nice especially on our turbulent fields.

Have to ask the obvious question: why not bring the leadouts through the SAME hole? (Or leadout guides that are siamesed.) Build the line connections so they do not interfere under max control excursion. Or take the lines through the leadouts and into the wing and connect them internally.

Yes that would be solution for this one problem, but if you really need another position for up line and another for another line?

And as I wrote I am perfectly happy with little amount of damping with down line front.

you can run them through the same hole. People have done it for years on combat planes. Doesn't seem to make much of a difference, compared to a moderate 3/4-1 in. separation. Main reason in combat was to have only one leadout guide to make.

Main problem you run into is line clips sticking to each other. Of course, if you don't use leadouts, no problem!

I have a set of plans that shows the lead outs, one on top the other with the spacing very close about 5/8" apart. Most airplanes have the lead outs in line, one in front of the other. Most plans show the lead out in the back as the UP and the lead out in the front as the DOWN. I always make my adjustable lead outs 3/4" to 1" apart.

>I have a set of plans that shows the lead outs, one on top
>the other with the spacing very close about 5/8" apart.
>Most airplanes have the lead outs in line, one in front of
>the other. Most plans show the lead out in the back as the
>UP and the lead out in the front as the DOWN. I always make
>my adjustable lead outs 3/4" to 1" apart.
>
>Gary Weaver

I use over-and-unders on my combat planes, spaced about 1/2" apart vertically. Works well. Seems to me to produce smoother transitions. (At the "x" of an eight, for instance).
--Ray

I have built a number of 1/A - 15 size stunt/sport airplanes. I find that the smaller the airplane the more effect a difference in leadout spacing makes. On a 40-size ship, I don't notice any yaw with leadouts 1/2 apart. On a 1/2A I see yaw with leadouts 1/8 apart. So on my 1/2A's I now make one hole for the leadouts.

Thanks for the input everyone. I think I get the idea now.
Cheers!
Mo