Thanks Dave,
Sorry for delay in reply, but had problems trying to send replies.
Of the 3 R/C sailing boats I now have. I can only see the working part of the sail adjustment in one, which has extended arm on servo with a pulley system. the other 2 aren't visible , only space under hatches for battery access and crystal change.
Will try to put some photos on later.
Thanks Colin.

HI Colin
Not rocket science, very simple really. There will be a rudder servo and some form of winch to pull in and release the sails via cords, one for the mainsail and one for the jib. Winches can be either of the arm type or use a drum. Basic designs usually use a simple elongated arm on a powerful servo.
Control is simply use of the rudder to control direction and use of the winch to control the sails, letting them out to catch the wind and to prevent the yacht from being blown flat.
As you have already sailed yachts you will understand the basic principles of sail so the use of RC is an extension of free sailing with the ability to steer and adjust the sails.
The cords usually join the boom near the mast and run to a fixing point along the boom with a bowsie attached to allow for initial adjustment. Both sides of the sail arm are used on dor the main sail and one for the jib.
Be good to see some pics as this is very basic info and you might have a more advance system installed.
Cheers
Dave