In eastern Asia, the [ junk rig ] as used is a refined, multipurpose sailboat rigging type which, while not being effective close winded, has its efficiencies off the wind. The appeal of the junk rig is the ease with which it can be set and reefed, operating on the same principle as horizontal-slatted window shades. Originally junk sails were made from closely-spaced split bamboo or vegetable fibres, and lending itself to quick reefing with the modern junk sail having full-length battens made of bamboo, which self-stow when lowered.
To control the twist and set the sail is by control lines leading from the helmsman to a single, solid wood block with lines leading to the end of each batten. Other lines control hoisting and determining the fore-and-aft position of the sail on the unstayed mast. Large junks can have up to four masts, but two or three is the norm.
Junk masts mostly are raked forward, along with a similar forward rake used by the seamen of the Arabian seas which supported the weight of the lateen rigs of the dhows.
The [ dhow's mast ] is short but the yard that supports the sail is both long and heavy. The triangular sail has a long leading edge and can be sheeted closer to the wind. The feluccas of the Nile carry a similar rig, but higher in order to catch the wind above the river banks. This trading rig again was developed over thousands of years, and used in every type of boat on the Nile until engine power arrived.
The other is the [ crab's claw rig, ] similar to a lateen sail in basic shape except there is a spar on each of the two longer edges. The crab's claw sail is set pointed down with both spars angled upward. Research shows that it may have the potential to produce more power than other types of sails on all but a close-hauled course.
The [ square sail rig ] is popular as a downwind rig as it can be wider than it is high, keeping its centre of effort or the capsizing factor down low, but the square sail rig is impossible to use closer than 60 degrees to windward. The square sail has a spar at its upper edge controlled by lines to set it, and turn the sail to the desired angle to the wind.
The development of square sails on small inshore boats led to the sprit and lugsail versions. The lugsail has its tack set at the mast, resulting in the yard being cocked up at an angle or commonly, led forward to the windward gunwale attaching to a tack hook. When changing tacks, the yard is lowered on the mast traveller dipping around the mast to be hoisted and set on the leeward side; meantime, the tack was moved to the windward tack hook.
A gaff rig's mainsail has four sides and set on a relatively short mast, with the boom at its foot and another spar or gaff along its head. The gaff rig’s popularity, with or without a boom, arose because it is a rig which has the power needed by fishermen, pilots and coasting trading vessels. Being a fairly complicated rig, the gaff rig requires considerable effort to hoist and control but up and drawing from a close reach to a run is efficient at harnessing the wind's power.
The Gunter rig transition the four-cornered sail into something resembling the Bermuda rig. The gaff is hoisted, almost parallel to the mast, to give the sail height and in dinghies, this system ensured that the spars were short enough to stow.
A Bermuda rig mainsail has three sides and is the most common mainsail on modern boats. With its triangular sails, the bermuda rig has evolved from the sails used on the islands' dinghies. The transition from the two spars of the Gunter rig to the single Bermuda spar is a natural development. With triangular sails used as headsails on most square-riggers, their efficiency came to be renowned. The triangular sail rigs are a continually being developed for upwind work but require additional sails for downwind work.
Single-sailed Bermuda rigged boats, or those which have no headsails, are described as being cat-rigged or una-rigged; multiple-masted versions are cat-rigged ketches or cat-rigged schooners. The una or cat rig has the mast stepped right forward and in dinghies it is usually unstayed. The mainsail is rigged with a sleeve over the mast and there is no headsail.
The sloop rig is the most common with one mast, a gaff or a Bermudan mainsail, and single headsail. Bermudan sloops are described as masthead or fractional with a masthead sloop having a larger headsail with the forestay attaching to the top of the mast.
A fractional sloop carries a smaller headsail set on a forestay that is fixed to the mast some three quarters the way down from the top. Fractional sloops allow sail control through the action of mast bending so many dinghies are fractional sloops, but many yachts are masthead sloops.
The cutter rig is popular for long-distance yachts having one mast that carries two headsails, each on their own stay. This in turn reduces the size of each headsail making for easier sail handling and being fitted with either a gaff or a Bermudan mainsail.
Two-masted boats are not common these days but ketch or yawl rigs are found on older boats greater than 11 metres long. A mizzen mast is stepped aft of the main mast with the ketch having a larger mizzen mast than the yawl.
The schooner and the ketch differ in that the main mast on the schooner is taller than the foremast and this rig was developed by the fishing schooners of the Grand Banks. The small mizzen and larger main of the ketch gave the inshore fisherman the correct degree of balance when trawling, above all with the addition of a powerfully large overlapping tow foresail.
Keels development has improved over the years with most modern yachts built with variations on the fin keel however, a number of other keel types are available. The keel has two purposes to resist leeway and provide stability. Draught or the depth of the keel, is an important consideration with many cruising yachts drawing 2 metres or less.
A fin keel is a single ballasted keel and is narrow on racers, creating less drag from surface area, to fairly wide on cruisers. Some variations of fin keel have bulbs or wings at the tip that concentrate the weight down low. The rudder is hung on a narrow skeg or with spade rudders, cantilevered on their shafts.
Twin keels, known as bilge keels allow yachts to dry out sitting upright and sometimes used in conjunction with a fin keel. Bilge keels are less efficient than fin keels, however, the yacht can be kept afloat in drying harbours and sail comfortably in shallow waters.
Traditional keels are long, running for half to three-quarters the length of the vessel with the rudder hung on the trailing edge. The reason for these keels on traditional wooden vessels is the strength that it gave the hull but nowadays long keels are only on heavy-displacement yachts.