I have a SIG Four Star 60 that I would like to do some mods to. I will first increase the rudder by an inch. This will be easy and from what I've read give me more rudder authority.
The second one is a little harder. I would like to set up a pull pull rudder system on it. Here's what I've gleaned off the net concerning pull-pull rudders {correct me if I'm wrong}.

1. Make sure the length of the wires are the same.
2. Make sure the servo horn and control horn are the same distance.
3. 1 and 2 make the geometry the same which is good.
4. You can cross the wires but this creates other problems.

Included is a pic of one another member did. The back one is the rudder setup. This looks like a good option and I realize I will need to glue some plastic rods into the fuse for the wires to exit.

In summary, I would like to install a simple pull-pull system to get maximum throw and help stabilize the rudder better than the standard set up. Any photos, methods, suggestions would be appreciated.

This is well covered here http://members.cox.net/bdfelice/Pull-pull/pull-pull.htm

Make sure you start with the extra long servo arm.

Thanks to my son's computer skills - my 4 Star 60 pull pull setup.

Here is another article that might give some info...

http://www.mini-iac.com/EditModule.a...iew&ItemId=199

One of the things that I do when I cross the cables (which is the only way I've done it so far) is to use ball-joints on the servo end and put one ball-joint on the top of the servo arm and the other on the bottom. This way, the cables aren't rubbing where they cross. Works great on my Funtana and it looks like it's going to work well on my GP Skybolt (kit, not ARF).

Once you've done it once, you'll see how easy it really is and how well it works.

-Todd

This can give rise to a problem unless you use a really stiff horn.

The ball joint is not on the centre line of the horn. Therefor a torque is created which will twist a plastic or weak metal horn.

This might not matter on a SIG Four Star 60 flown at training speeds but anything bigger, faster or with larger control surfaces could have problems.

I agree... I wouldn't do that on a larger aircraft. But on something this size, it works great. Any time you use ball joints, there's the possibility of twisting a weak control horn/servo arm, not just on a pull-pull.

On something larger, I would run the cables through a tube of some sort to prevent rubbing/hitting each other. The other option is to mount one side of the servo higher than the other.

-t