Servo size vs airspeed

[INewton]

I noticed that when I started to push up the airspeed on my pattern plane, the elevator wouldn't move until I backed off on the speed.

What's the best servo/configuration for next level of performance elevator control?

Pull-pull?
Flying elevator (one piece)?
self actuating (with small tab on elevator)?
a huge high torque servo?
larger arm with reduce throw?

Newt

[Sparky Paul]

What size is the plane?
Do you know what others with that airplane are using?

[Ollie]

The torque needed depends on the square of the air speed. If you double the air speed then the torque needed is four times more. That is all. To use the torque of the servo, you couple the original control surface then you need coupling stronger and stiffer.

However, the flying tail can be designed to make the servo torque load near zero. The pivot line goes thru 23% to 25% of the mean aerodynamic chord of the tail surface. It helps to mass balance the tail surface around the pivot too.

The flying tail stalls at about 10 to 15 degrees depending on tail aspect ratio. So the servo has about maximum 45 degrees rotation and the tail has about 10 to 15 degrees maximum rotation. So, the tail arm length is about three or 4.5 times the servo arm length.

[INewton]

Ollie,

Thanks, that's what I needed to know.

***

Sparky,

The plane is a .46 2C pattern plane, but it's converted to electric. At the same weight, the plane has .60 to .90 performance. So it's a short and fast flight or a long and slow one. I'm using 3004 servos with a fairly long steel rod link (which when stressed appears to bend before/after tube).

[Sparky Paul]

Simplest is to upgrade the servos to higher torque types.
Flying tails are not used in pattern. They can't provide the extreme amounts of force a flapped tail can.

[Joe Minton]

INewton:

Could be either servo torque capacity and/or control linkage rigidity. You need to make sure of both.

While you're at it, make sure that the linkage is play-free and that the hinge line is sealed. Otherwise you invite flutter at speed.

Joe

[AERO3DPat]

http://www.coloradogliders.com/servotorquecalculator.htm

[Rodney]

Your problem appears to be a soft or flexing control rod, not servo power although it could be both. As to your question on pull-pull, yes that is usually more foolproof than push rods and can be definately made to have no slop or blowback.