Gazela is rigged as a barkentine, a ship of three masts, fore and aft rigged (the sails set parallel to the center line of the ship) on the main and mizzen masts and square rigged (the sails set perpendicularly to the center line of the ship) on the fore. A full rigged ship has three or more masts, square rigged on all. Square sails are good at catching the wind and pulling the ship along with them and, thus, are good at sailing downwind. They do sail well to windward but require plenty of sea room and can be difficult to maneuver.
To improve the handling qualities of the ship-rig, a spanker was added. This is a gaff-headed (a sail that is lashed to a spar attached to the mast at one end) fore and aft sail set on the mizzen mast. Since fore and aft sails are very good at sailing to windward this worked very well and eventually the spanker was set on its own mast which created the bark rig. There are and were barks with three, four and five masts.
The barkentine was developed at a time when the steam ship was beginning to compete in the sailing trade. Since the fore and aft sails require less men to work them, it was possible to get by with a smaller crew which increased the ship’s profits.