To answer the original question we don't need any calculations......the main reason we have exposed linkages is because our servos have a rotary output which in most cases has to be converted to linear movement. The full size control surfaces we are talking about are moved using hydarulic actuators which have linear movement already.

Incidentally even using linear hydraulic acuators a lot of full size aircraft still have part of some linkages external but use fairings/covers to protect/streamline.

Whatever happned to the linear servo?

Rob.