may i ask what is the purpose of a pull-pull system and why is it even neccesary as im not into 3d yet and dont know how it all works

Pull-pull is where you have horns on both sides of the control surface, and use wires instead of rods to activate the surface, I find it to be a effective and easily adjustable means of control, I'm sure there will be a lot of dissagreement though. A little more challenging to make and set up for some. [&o]

Pull Pull is not exclusive to 3D type aircraft. Sig has an LT 25 kit that uses pull pull on the rudder and it is a trainer model. Alot of the models from WW 1 have pull pull systems. Gunfighter has described how it is done, and I agree, it is harder to set up than the regular control horns, but it is a much more positive way of setting up the control surfaces. Good Luck, Dave

Pull pull gives you more prcise control because you dont have the rod
flexing when it is pushing.

There are pro's and con's to both systems. The pull pull rudder is pretty common on bigger planes. Pull pull is harder to get right (with no binding and no slack). On pull pull the surface deflections are always symmetrical with the servo throw. Also the torque applied to the surface at max deflections is the same for both directions (push pull is not). Pull pull has shorter servo extensions, push pull servo extensions are very long. As someone mentioned the push pull rods flex.

I agree 3D has nothing to do with it. Pull-pull VS push pull has mostly to do with how you want to setup the plane. In most cases I'm just trying to achieve the proper balance.

I find that the only benefit of pull pull is in a plane where you would normally put servos in the tail. It will allow you to put the servos near the CG to better balance the plane.

Flexing of the pushrod will not happen with the proper rod. Your local sporting goods store will have arrow shafts which make excellent pushrods. If you perfer to spend a little more money, go to central hobbies and get there CF pushrods.

Also Dave Brown's pushrod system works very well, If you bore it out to accept 4-40 rod