Is it allowed to use servo for controlling the tension in the backstay?

Relevant  Class Rules

Part 2
The rules of Part 2 are open class rules in which anything not specifically prohibited by the class rules is permitted.

C.8 EQUIPMENT
C.8.1 PROHIBITED
(a) Except where achieved by mechanical systems, automated control of rig and/or sails.

Answer

Servo may be a part of mechanical system used for controlling the tension of the backstay. It is allowed to use a servo controlled by the transmitter in the way that there is proportional or non proportional linear or rotational movement of the servo when actuated by the movement of a stick and/or a switch on the transmitter. In described way it is obvious that tensioning of the backstay is done by the competitor at his/her discretion. This is not automated control of rig prohibited by the class rule C.8.1(a).

However, using of servo to activate and deactivate an automatic tensioning system controlling the backstay is prohibited.