Advantage of the forward line being the up line?

[Tim Stagg]

All,

I feel really dumb asking this question at this point in my flying.......but should the forward line be the up or the down line?

Does it matter?   Is one better than the other?

I checked on all of my airplanes and all of them have the forward line being the down line.

Thoughts??

Thanks

[Motorman]

If your lines are spaced less than an inch apart it doesn't really matter. The thinking is at the top of the hour glass the rearward down line will give you more nose out when you're in the outside turns.

Motorman

[Istvan Travnik]

When your engine / motor revs conventionally (ccv looking from the front), the front line "up" is disadvantageous, since the bigger or smaller yawing movements of the model makes an amplifying effect on jumping of the model, after corners.
Not amplifying (destabilizing) but damping is desired.
We discussed this topic some 4-5 years before, very thoroughly. Sorrowfully I cannot remember the precise title, but you will find it.
Istvan

[Istvan Travnik]

Well,
Here is that topic for you:
https://stunthanger.com/smf/building-techniques/bellcrank-normal-or-reverse/msg386941/#msg386941

Istvan

[Dennis Toth]

Tim,
It is a small trim tool that some top fliers feel helps on outside corners with conventional clockwise engine/motor rotation (looking from the front). It puts a little more of the control force on the back down line (pretty small unless you are on one line full down) and adds a little yaw to counteract the inward force of the prop on the downward turning. In stunt heaven wind you might not notice anything but in stunt hell wind in could be a positive advantage and easy to do so why not. People have flown both arrangements and won, you kinda have to try it and see what you like.

Best,   DennisT

[Paul Smith]

I've flown both stunt & combat for decades.  It makes no difference unless you hang the model from one line, which you really shouldn't do.

Unless the bellcrank is pushed to the limit, the force will be equal on both lines.

In Carrier, where you can let the Down line go slack and hang from the Up & Gas lines, it helps a lot to have the down line way in front.

[Brett Buck]

I've flown both stunt & combat for decades.  It makes no difference unless you hang the model from one line, which you really shouldn't do.

Unless the bellcrank is pushed to the limit, the force will be equal on both lines.

     It definitely will not be the same on each line. It takes torque to deflect the controls, even when they are not pegged out, so there will definitely be a differential tension in the lines. In the extreme, you hang it on one line *without* pegging anything out, just because it takes so much torque that the differential tension equals the line tension. That's the Netzeband wall, and it certainly a matter of interest in stunt.

    Brett

   

[Dan McEntee]

  As I was learning coming through the ranks, I was influenced into having the down line in back by several people and articles in magazines. I took it as that by itself, it is not an all encompassing solution to problems but when used in conjunction with other trimming and set up tips, it helps make the overall package more acceptable. So, I have always done it this way unless I just flat out forget what I'm doing when building the wing!
   Type at you later,
   Dan McEntee

[Perry Rose]

The advantage of front line up shows up best on a profile model. It puts the push rod on the side away from the engine exhaust. Makes cleaning easier.

[Ken Culbertson]

The advantage of front line up shows up best on a profile model. It puts the push rod on the side away from the engine exhaust. Makes cleaning easier.

Unless you use a logarithmic which reverses the reversal and puts the down line back in front.  

Ken

[De Hill]

If you are flying a sport model upright and very low in deep grass, having the up line in front is an advantage.
If you get low enough, the tall grass will hit the up line and make the airplane climb out of the grass.
Having the down line in front would make the airplane descend into the grass.

[Tim Stagg]

Thanks everyone,

I think I will continue down the path i have been on, just wanted to make sure I wasn't missing a major advantage I was not aware of.

I may experiment at some point just to see the difference, but for now...if it not broken, don't fix it

Thanks again

[Paul Walker]

Unless you use a logarithmic which reverses the reversal and puts the down line back in front.  

Ken

Unless you reverse the bellcrank!

[Ken Culbertson]

Unless you reverse the bellcrank!

Is there any other way to properly learn things other than the hard way!

Ken

[Motorman]

I guess the way to have the down line aft would be to have the push rod arm on the bellcrank inboard. This means a custom bellcrank if you want to have it self centering or neutral. Of course with the current state of affairs we're getting back to the days when you have to make everything yourself anyway.

Motorman

[Sean McEntee]

I guess the way to have the down line aft would be to have the push rod arm on the bellcrank inboard. This means a custom bellcrank if you want to have it self centering or neutral. Of course with the current state of affairs we're getting back to the days when you have to make everything yourself anyway.

Motorman

Nope, just flip the bellcrank so that the pushrod is inboard of the bellcrank post or mount.  An inboard pushrod on profiles does clean up the appearance from outside the circle, if one is concerned about that sort of thing.  As far as other reasons, well, whatever you choose to believe.

[Ken Culbertson]

An inboard pushrod on profiles does clean up the appearance from outside the circle, if one is concerned about that sort of thing.

I am and that why I do it that way regardless of which line is in front.

Ken

[Motorman]

Motorman: "I guess the way to have the down line aft would be to have the push rod arm on the bellcrank inboard".

Sean: " Nope, just flip the bellcrank so that the pushrod is inboard of the bellcrank post or mount".

 LOL,
Motorman

[Sean McEntee]

Motorman: "I guess the way to have the down line aft would be to have the push rod arm on the bellcrank inboard".

Sean: " Nope, just flip the bellcrank so that the pushrod is inboard of the bellcrank post or mount".

 LOL,
Motorman

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