A gaff rig is a fore and aft mainsail arrangement consisting of a square, peaked sail suspended at its head on a spar known as a gaff and at either end of its foot on a boom. Both the gaff and boom pivot on the mast on jawed fittings secured with beaded lines. The gaff is hoisted or lowered on the mast by two lines known as halyards, one at the throat and one at the peak. Once set, the gaff rig sail is peaked or pitched up at its leech outer edge. Gaff rigs are efficient, develop minimal heeling movement, and offer large sail areas for any given mast arrangement.
Gaff rigs are similar in design and setup to lug rigs and allow for square sails to be used as fore and aft configured mainsails. The gaff rig gets its name from the spar of gaff from which the sail is suspended at its head. The gaff pivots at its inner end on the mast with a jawed fitting secured by a line equipped with wooden beads to prevent chaffing. The gaff is usually hoisted on the mast by two halyards, one on the outer or peak end and one at the inner or throat end. The lower edge, or foot, of the sail is attached at either end to a boom which pivots on the mast in a similar fashion to the boom.
The gaff rig is a popular mainsail choice for schooner and barquentine vessels and is often used on smaller single mast designs. The rig offers several benefits, one of the most notable being the comparatively large sail areas possible with the design. The gaff arrangement allows for mainsail rigs with almost twice the sail area as triangular fore and aft designs. The pitched gaff orientation also permits the mast to be shorter than the highest point of the sail.
Another significant gaff rig benefit is the reduction in heeling movement inherent to the design. Heeling is the tendency vessels have to lean away from the pressure of the wind in their sails. For any given sail area, the gaff rig has a relatively small heeling movement, thereby making for easier sailing. Multimast gaff rigged ships usually carry gaff mainsails in combination with jibs, staysails, and triangular topsails. Smaller vessels typically feature a gaff mainsail and a jib although several sail combinations are possible.
