RE: pull pull system on GP Sportster
decombs21, pullpull verses rods. Lets do a little experiment here, get a brick and a plastic drinking straw. glue the straw to the brick. Now try to push the brick away from you using only the straw, you see it will only bend. NOw pull the brick, and you can do it. So it is with the pull pull system. Your servo is pulling either way. With rods you pull one way , and push the otherway. Control surfaces in flight need a lot of force to make them deflect in flight, so it is easier on the servo to pull the surface into the slipstream than it is to push them, also you are saving on weight , as the cables weigh much less than the push rods. Also because the cables are always kept tight , the chances of in flight flutter is reduced dramatically also. I use pull pull in all my models from the humble spad to my 3D
pattern ships, and i use them on rudder and elevator.
the_madgenius , instructor downunder.