Pull pull or Push Pull

[ericb]

Love push/pull. I will use pull/pull as a last resort if needed.

 

[Bunky.F.Knuckle]

I think if you go with stock mufflers and enough battery you "should" be able to go push pull.

 

[pawnshopmike]

Thanks guys! Now just have to figure out which would suit my 3dhs 106' edge. Would like to try push pull but I believe the edge has a tendency to be tail heavy.

Just put some extra weight up front, aka BIGGER engine.

 

[Lojik]

Im contemplating push pull on my 3dhs yak. Its gonna have a 70 twin up front so the rudder down back might be a better option.

For larger birds 3m+ would you run a servo each side and match them to maintain power in the rudder or go pull pull?

 

[Knife-Edge]

I think if you go with stock mufflers and enough battery you "should" be able to go push pull.

Plan on going with the GP123 on stock mufflers.

 

[Bartman]

in an ideal world, all of the weight/mass associated with power, controls, structure would be concentrated at the CG making the tips, tail, nose as light as possible so the plane would start and stop maneuvers instantly. i understand the problem with slop in controls but the more we put heavy servos in the tail and out in the wings we move away from the ideal for an airplane that is supposed to be maneuverable.

one more servo in the tail might not make a huge difference but it would be interesting to see how much of a difference it would make if the servos were all centrally located near the CG with the batteries and fuel tank. unless you pull a P-39 then engine is likely staying out in the nose but everything else in a large airframe could be mounted in the fuselage. the challenge is to maintain really tight positive control without slop.

just thinking out loud

 

[Bunky.F.Knuckle]

Plan on going with the GP123 on stock mufflers.

If it does balance tail heavy, you can shift the engine fwd some, to counter act.

 

[Knife-Edge]

If it does balance tail heavy, you can shift the engine fwd some, to counter act.

Hope it doesn't

 

[Islandflyer]

Pull-pull and push pull both work fine
The ideal push-pull system is two servos, one pushing when the other pulls. This set up is more critical than pull-pull, as the geometry and programming has to be perfect in order to avoid one servo fighting the other at all points of the travel.
Single servo push-pull is not ideal: pulling action is fine, but each time the servo pushes, you are essentially trying to de-hinge the rudder, and resistance from the hinges at the control horn location is what makes the rudder turn. With hard flying and lots of rudder use, these hinges often don't last very long.

 

[Pistolera]

in an ideal world, all of the weight/mass associated with power, controls, structure would be concentrated at the CG making the tips, tail, nose as light as possible so the plane would start and stop maneuvers instantly. i understand the problem with slop in controls but the more we put heavy servos in the tail and out in the wings we move away from the ideal for an airplane that is supposed to be maneuverable.

one more servo in the tail might not make a huge difference but it would be interesting to see how much of a difference it would make if the servos were all centrally located near the CG with the batteries and fuel tank. unless you pull a P-39 then engine is likely staying out in the nose but everything else is a large airframe could be mounted in the fuselage. the challenge is to maintain really tight positive control without slop.

just thinking out loud

Totally agree Bart. Last IMAC contest we were discussing this idea. I've often wondered why no one has put the aileron servos in the fuse, using a CF tube torsion rod for the hinge, with quick connect couplings for wing removal. Could have multiple ganged servos all neatly tucked in at the center of mass. Also less wiring.

Elevators could be done with a CF push pull and bellcrank.

OK @Terryscustom there's your next project !!!