This is the controller

The controller is attached to the pedal of the foot switch by a clevis at the top.
The plunger is drawn upward by the movement of the pedal. This plunger has cam faces on it so that the three micro switches are operated in sequence as the plunger is withdrawn.
The plunger is returned by a small spring.

It is important that the wire is clamped securely as it enters both the plug and the controller to reduce the possibility of a broken wire in use.

The plug has a retaining nut so that it won't be pulled out of the winch accidentally.

A four wire cable is required for the three speed winch.     I have found this very difficult to find.
It is important to get a heavy duty cable with multicore wires. Three core cable of suitable weight
is easier to find as it's used on many electrical appliances and is fine if a two speed winch is to be built.

Then there's the winch electrical circuit .... as shown below it comprises of three sections.
1) the foot switch controller
2) the motor control circuit
3) the winch resistor control.

The foot switch controller is operated by the pilot and switches the three solenoids and directs the current through the resistors to allow speed control of the motor.

The foot switch itself is designed so that the pilot can stand on the switch to keep himself balanced and then press down with his toes to operate the switches. This is important if he is also launching his model.

The conections between the solenoids and to the motor are done with 25mm x 4mm copper bus bars. The conections to the battery are with the heaviest flexible cable that can be found. This is to keep the resistance of the control circuit to a minimum. A typical control circuit has a resistance measured from the battery to the motor of about 1milliohm.