Abstract: A sail winder, more particularly a mainsail winder tube, made of a tube or similar profile rotating about its axis under the action of a control system, to which the sail is rigidly connected and about which it winds, and wherein a control system, made of a toothed pulley, is accommodated inside the mast foot or beneath the mast foot.The winder includes, for hauling the sail, a halyard passing in a higher portion of the winder tube over a pulley rigidly connected to the tube and rotating therewith, with the halyard passing inside the tube and exiting from the winder tube via another pulley rigidly connectd to a fixed portion of the winder.