I have an option on my Chipmunk to use either the pull pull or normal hard wire push rod on the rudder... so which one is better? For pull pull I have to move the servo a little back with some more work but push rod systems is straight forward.

So which one should I prefer...?

If the pull-pull system is within your grasp, definately use it.

1. It weighs less.
2. Much more effective use of the rudder.
3. It will not flex or bend as with a pushrod.


If using a pushrod, I would highly recommend carbon fiber as opposed to nyrod, metal, dowels, etc...

JMHO

Hi!
Thin fishing wire is best, and lighter than a pushrod. And does not transfer vibration back to the servo eighter!
Carbon fiber rod or aluminum arrowshaft is what I use if I have to use a rod.
In small planes, around 150cm span, I use 10x10mm balsa rods for elevator and rudder were I can´t use wires.

Regards!
Jan K
Sweden

Thin Fishing wire may not transmit vibration but it can be a source of glitching. I Use only Kevlar string and exit the fuse using teflon Tube. does not stretch with heat or cold like wire can...
Don///

I second the use of Kevlar. Holds up very well and soesn't stretch. I also think it is easier to work with than wire.

I have used pull pull wire cable a long time . It has worked for me on everything from park flyers to 1/4 scale. There are a lot of ways to rig with wire and it has never failed me yet

One of Kevlar's best attributes is that it doesn't stretch. I first encountered it when it was used in the early 80s as suspension lines on parachutes. However, it doesn't have much abrasion resistance, so mount your system in such a way as to prevent the Kevlar from rubbing on exit tubes, etc..

Otherwise, it'll "fuzz" up.

Mike,

You are right about that! If you use kevlar you should inspect it occasionally as it is subject to fraying. I have both wire and kevlar pull/pull systems. My wire system is about 12 years old and still in good shape. My kevlar system has been restrung once, after about 3 years of use, due to fraying at the fuselage exit. Good systems, both of them, but they all need periodic inspections.

Have fun!

Bedford

The abrasion factor s the reason I use the Teflon Tubing to exit or where the lines cross. Had a Pull pull on a 1/4 scale plane for years with no known problems

Don//