I have a Enya SS40 powered Wot4, a symetrical wing, first aerobatic plane, fairly light.

I want to replace the single servo controlling both ailerons with 2 individual servos. We have a short downhill strip and running off the end on landing is always a problem that the guys with flaperons/spoilerons don't suffer. (they are probably better pilots too).

I have bought 2 Topaz mini servos rated at 1.8Kg/cm, thinking the pair of them would be close to being a replacement for the existing std servo. Std servos are in the 4-5kg/cm range, so I figured that 2 x 1.8=3.6 would be pretty close.

Until I got them home and took them out of the box and they are TINY!
Now I'm not so sure I want to entrust my plane to them.

How can I decide if they are going to cut it or just strip the gears? I figure there is a considerable safety margin in a std servo, and I'm only recently off my trainer, so I won't be going ballistic with it.

Short of driving down the road at 50mph with the wing out the window and a spring scale attached to the the aileron control arm, I can't see how I can make an informed judgement.

Does anyone know of a formula that would allow you to predict the pressure exerted by airflow on a fully deflected aileron?

Ailerons are 60cm (24") x 4cm (1.5") each.

Any suggestions much appreciated.
Thx

Someone was nice enough to give all the formula and rough sizing over in the Aerodynamics Forum about one month ago. It is mostly based upon expected size, air speed, hinge point, and area. As you may be using a lever to alter the torque value, that also has to be added in.


Wm.

The minis may have sufficient torque, but the small gears in these servos can strip if shocked...

Yup. I'd stick with a pair of standards

ThereĀ“s a servo torque calculator at the link below

http://www.csd.net/~cgadd/eflight/calcs_servo.htm

Hope this helps,
/Leo

Thanks all, especially Leo & Wm for the info and useful links, that then led me to further info.

From all of this, I got the impression that they should do the job, if they don't get shocked.

However, after flying the plane for the first time today [with a single servo in place], I came back with such a big grin on my face that I don't think I need to bother. The thing lands like a hummingbird in half a strip length!

If I do get around to putting them in, I'll post the results at some future time.

Cheers.
Steve