I have heard alot about pull-pull rudder setups but have never actually used one. I would like to build a Goldberg Chipmunk and need to get some insight into how this is done..... I want to do it right the first time.... Can you please enclose pics of your setup as you explain?? Thanks.

Pick up a set of Pull-Pull cables from Dubro...4-40 size if you are overpowering your plane. VERY easy to set up, just look at the instructions.......(on the cables)....Use a ball bering servo and just run two lines (one from each side of the servo arm), one the one side of the rudder, the other to the opposite side.

Once you do one, you will always want to do more!

Even did one 'scale'....

To which engine sizes or aircraft weight is Dubro pull-pull 4-40 recomended for?

I prefer 4-40 cable if I'm using 4-40 threaded rods on the plane - usually 1/4 scale or larger.

Ok. Do you guys know of any other pull-pull that is not as heavy as the Dubro is? I have used the Dubro earlier on my Extra 300 .60 and it worked great. However I have always thought that the bult boing thru the rudder is a heavy piece being made from steel. Also Im now in the start up for building a 1/4 scale Extra and would like it to as light weight as possible.

You could use 2 control horns back to back with bolts between them. But that may weigh about as much as the Thru-bolt type.

When you reduce weight, sometimes you sacrifice strength too.

Maybe a piece of epoxy glass printed circuit board cut to size and glued into the rudder structure?

Carbon fiber?

You can go as far as your pocketbook can take you.

Depending on the placement of the C of G perhaps place the rudder servo at the rear fuz bottom and use 2 carbonfiber push rods, one for each side, instead of pull-pull but still pull-pull hook up design. This assumes one could get the a/c into balance with an additional rear mounted servo without having to add weight for C of G purposes or it will be pointless.
I like the idea of using two horns instead of the heavy steel bolt. Lets see what horns and solution to possibly reinforce the structure I will come up with whenever I get to that stage.

Sullivan makes a Kevlar pull pull set up might save a few grams on the steel lines. If this is your first time with a pull pull rudder linkage. try and get the rudder servo centered in the fuselage if possible. you can run two control horns one on each side of the rudder or my favorite a long 6-32 bolt thru the rudder. on the goldberg chipmunk i would have no problem using 2-56 on the pull pull again it will save a few grams over the 4-40. Any doubts about the strength of 2-56 i have been running them on my 140 equipped pattern planes for a few years now and have been completly happy.

Dennis

Hi!
I have used thinnest possible fishing wire on many different airplanes for 30 years. Both scale and pylonracers as well as sport airplanes.

Regards!
Jan K
Sweden

Tjena Janne,

What strenght fishing wire are you using for what size plane. Are you just making sure that the wire is stronger than the strenght of the servo? The Dubro pull-pull system comes with plastic coated wire. I don't really see the point in having a coated wire but perhaps someone else here might know the benefit? ...unless it is to prevent corrosion?

By the way Jan, I have got myself another Extra kit and are truly enjoying the build. I guess you will see it at the field when finished.

C.

I make up my own systems and use 30 Lb. stainless steel leader with the plastic coating. You can wrap the wire A few times and melt the plastic A bit and it fuses to itself. I also use very thin tubing and slide it over the wire ends and crimp it. Pull/pull is really an easy system and you can get very creative on how you do it. I have even attached two carter pins to the end that goes to the servo arm and then slid those through A couple of quick connectors. The 30 Lb wire slips right on through that yellow flex tub and I run that through the fuselage.

Gray B,
30 lbs wow... On what size plane?