Square rig

Square rig is a generic type of sail and rigging arrangement in which the primary driving sails are carried on horizontal spars which are perpendicular to the keel of the ship and the masts. These spars are called yards, the tips of which, beyond the last stay, are called the yardarms. Square rig was the main design in the age of sail, (1571—1863). A ship at least partially so rigged is called a square rigger.

Square rig can also describe individual four-cornered sails suspended from yardarms, and carried on either a square rigged or a mainly fore-and-aft rigged vessel, such as one with either a bermuda rigged or gaff rigged mainsail.

Square rig can also describe the uniform of a rating in the Royal Navy. This term is slang and refers to anyone wearing the non-peaked cap worn by Petty Officers and Officers this 'rig' includes the famous blue bib on the shoulders and bell-bottomed trousers. This perhaps reflects the fact that it was these men who managed the square rigged sails.

A mast is considered square rigged if its lowest sail or course is square rigged, but normally if this is the case it will have a complete set of square rigged sails. If the course is fore-and-aft, square topsails can still be carried in front of the mast.

Even square rigged masts may also have staysails that are deployed fore and aft between masts.

Square rigged vessels ranged in size from small boats to full rigged ships, however, today the rig in common use is a form of fore-and-aft gaff rigs and bermuda rigs. The reason for this change is technology. The strains imposed on cordage and sails in the Age of Sail meant that a large number of sails were necessary for larger ships. Fewer larger sails would not have survived the rigours of the larger commercial and military ships. To get the large number of sails to effectively collect wind and provide motive power they had to be square to the hull. There were no examples of the more efficient fore and aft rigs on larger vessels for this reason. Despite the large overall sail areas and even when sailing on their best points of sail it was sometimes the case that large warships could only make 6-8 knots, some of the faster clippers for whom speed was critical could make much faster speeds.

The square rig breaks up the sail area into many smaller sails, each of which can be individually handled by a small team hauling by hand on the lines. Having many smaller sails allowed warships to manage the impact of weapons upon them. Instead of losing one very large sail to a hole from a cannonball, which would tear, the damage was constrained to a much smaller sail area and therefore less impact on the motive power of the vessel. With the development of more advanced fittings, equipment and cordage, particularly geared winches, the load on an individual line became less of an issue, and the focus moved to minimising the number of lines and hence the size of the crew needed to handle them - a situation that favoured a few large sails instead of many small ones.

Similarly, hybrid vessels carrying some square-rigged sails have largely disappeared. The low aspect ratio of square rigged sails (usually 1/2 to 1/3) produce large amounts of drag for the lift they produce, and thus give very poor performance to windward. This means that they cannot sail as close to the wind. The Bermuda rig is the (nearly) undisputed champion of windward performance in soft sails, due to its very low drag and high lift to drag ratio. Square rigs do have their advantages, however; they are more efficient when running, where the high lift to drag is irrelevant and the total drag is the most important issue. Not only do square rigged sails provide better downwind performance, but they also are less prone to broaching when running than Bermuda rigs.

On a square rigged mast the sails had names which indicated their position on the mast. The lowest square sail was the course or mainsail, the next sail up the mast was called the topsail, the next the topgallant sail. If the ship were a large one it would have a fourth sail called the royal above the other three. Sometimes in lighter winds a ship, so equipped, would put out studding sails which would be fixed outboard of the sail on both sides of it. These studding sails were principally used on the higher sails only and were relatively small and time consuming to attach and detach. In some ships, especially commercial vessels, the topsail and topgallants were each split into upper and lower sails again to minimise the strain on the rigging and crew. Sails are referred to by their mast and then name so, for example, the fore topgallant sail ofetn shotened to fore t'gallant.

A square rigged sail is not in fact square, but more nearly trapezoidal, being symmetrical but longer in the foot than the head. Like all sails it is three-dimensional, and its curve or belly means its foot is not a straight line at all. It is fixed to a spar along its head (the yard), and its clews are controlled by sheets, often run to blocks on the spar immediately below the sail. The lower sails, without a spar below them, may also have tacks.

Modern square rigged ships are still used for training, tourism and ceremonial purposes.

• A barque has three or more masts, with the aftermost entirely fore-and-aft rigged, while the fore, main and any others are square rigged.
• A brig has two masts, both square rigged.
• A full rigged ship has three or more masts, including a foremast, mainmast and mizzen, and all masts are square rigged.
• A sloop has only one mast.

All the above rigs normally carry a number of jibs and at least one spanker, and may also carry fore-and-aft staysails between the masts.

• A barquentine has three or more masts, the fore square rigged, the main, mizzen and any others fore-and-aft rigged.
• A brigantine has two masts: A square rigged foremast and a fore-and-aft rigged mainmast.
• A square-topsail ketch carries one or more square-rigged topsails (commonly two, an upper and a lower topsail) on its mainmast, in addition to its mainsail, mizzen sail and jibs.
• A square-topsail schooner carries one or more square-rigged topsails on its foremast. This rig is often simply called a topsail schooner as topsails above the gaff-rigged sails are a standard part of the schooner rig.
• A square-topsail cutter or sloop carries one or (less commonly) two square topsails on its only mast, in addition to its mainsail and jib or jibs.

• The Maltese Falcon, a modern square rigged yacht
• Sail Training Ships, Square rigged training ships