Rudder pull pull question
 

Ok it's been about 15 years since I built my last plane, took a break, and now I am putting together a new plane.

I have run into an issue with the fuse being very narrow at the servo tray. I did some reserch on pull pull to refresh my memory and I got this out of it, the distance between the control horn connection holes and the distance between holes on the servo arm must be the same distance. Is that right or can the distance be less?

Thanks

RE: Rudder pull pull question
 

I don't think I have ever done a pull-pull setup where they were the same. But then I do sport and scale models, not ultraprecision aerobatics.

RE: Rudder pull pull question
 

From my modeling experience you can have the distance narrower at the servo end then at the rudder end. But not in reverse as the lines will get too much slack when pulled to one direction or the other. the difference can't be too great either as binding will occur. I've used pull - pull on my airplanes and have always tried to keep the distance the same. If it meant that I had to move the lines in closer in on the rudder control horn then that's what I did. Do a search on this site for pull - pull control type installations and you'll get a lot of info.

Cheers

RE: Rudder pull pull question
 

It doesnt have to be exactly the same. I actually prefer for the servo arm to be narrower in order to take advantage of the full range of motion and torque of the servo.

RE: Rudder pull pull question
 

They do not have to be the same, and either one can be narrower

RE: Rudder pull pull question
 

I'll add that I like to set the rudder horn slightly behind the center of the hinge. This allows the non pulling cable to go slightly slack, eliminating binds.

RE: Rudder pull pull question
 

Thanks to all, that will greatly help as there was not enough room to equal distances.

RE: Rudder pull pull question
 

With the horn hole just behind the hinge line, and one line going a bit slack, can this cause flutter? It doesn't seem like it because with air pressure pushing on the rudder it can't move foreward.......

Thanks for any info,

Ernie

RE: Rudder pull pull question
 

No Ernie, the airflow is hitting the pulling side, so it really can't flutter

RE: Rudder pull pull question
 

Okay, so if there is any positioning error when mounting the control horn (and trying to get it's holes lined up exactly with the hinge line...... if there is any error, it should be on the side of being slightly behind the hinge line. Otherwise, one line would go too tight with deflection. Right?
Or perhaps jus always mount the horn a hair behind the hinge line?

Ernie

RE: Rudder pull pull question
 

Right you are. If you mount the horn ahead of the hinge line, it will bind. Right on the hinge line, or a little behind is best.