rigged vessels to keep the mainsail in an aerodynamically efficient shape.) Such loose-footed sails can also be found on gaff-rigged Norfolk wherrys and the bawley class of vessel. The spritsail was a feature of the Cromster where the ability to furl the foot of the sail and raise the sheets, made gunnery much more readily possible. The sail could still be controlled using the vangs. In a commercial vessel, the rig has the advantage of allowing a high stack of deck cargo and freeing the cargo hatch of obstructions when loading and unloading. The entire sail can be quickly brailed to the mast. The overriding advantage is safety in open water. Barges are unballasted and, if overpressed, will heel excessively and must be pulled to wind. The sheet will be eased and the aft end of a boom could drag in the water making the rudder ineffective and a capsize inevitable. The sheet of loose footed boomless barge is just released and control is regained. The boom does not project outboard so that the vessel can pass through a narrow gap between moored vessels. Loose footed sails suffer from sail twist which reduces their aerodynamic efficiency when sailing off the wind, which usually is not a commercial issue. It can be an advantage in light air. The vangs control the head of the sail which can be set so as to make use of the air above the wind-shadow of moored ships, warehouses and so on. This fine control of the sail without need for the crew to leave the deck, is achieved by brailing up. Rather than lowering the mainsail, it is gathered up against its own luff and head by means of lines called brails. This technique is an effective way of stowing the mainsail and gives fine control over the power obtained from the sail. In narrow channels, and in the lee of tall buildings the mailsail and mizzen are brailed and the bowsprit topped up, and she sails on topsail and foresail alone. A gaff rig was far more suitable for heavy weather and long sea passages, but when a daff rigged boomie takes in the mainsail, she cannot set the topsail. However, it means that the sail is stowed aloft and unreachable from the deck. It also means that the sail cannot easily be covered when it is stowed, and thus protected from the elements.