How do I calculate the control surface throw for a scratch built model? Next would be how much servo torque should be needed. I'd like the formulas for this rather than 'It's been my experience to use this much on high rate and this much on low rate for this size model," or, 'Just throw in some of them there BB servos and that will take care of it."

OK, as an example lets take a 60 size sport plane and find the throws and servos needed. I'd like to use the lightest servos on the market so I'd need to know how much torque is required. No need to use standard servos if mini's running on 6 volts will do the job.


Engine ST 61
Model weight 5.7 LPs

Wing position Shoulder
Wing span 60.5
Wing average cord 11
Wing area 665.5
Dihedral 2.5 degrees
Wing loading 20 oz/ft

Fuselage length 42.25
Nose length 8.25
Tail length 34

Barn Door Aileron Length 14.5
Barn Door Aileron cord 2.75
Horizontal Stab Chord 7
Horizontal Stab Span 21
Vertical Fin height 10.5
Vertical Fin cord 8.5

Need to know the speed of the plane, and the length of the control horn and the servo arm for each surface...oh and the control throw you need as well.

You also need the span and chord of the elevator and the rudder.

And beware, a servo can have a high torque value but have little tiny gears that cannot take the loads.

Check here -

http://www.coloradogliders.com/servo...calculator.htm