Junk is a type of ancient Chinese sailing ship that is still in use today. Junks were used as seagoing vessels as early as the 2nd century AD and developed rapidly during the Song dynasty (960–1279). They evolved in the later dynasties, and were used throughout Asia for extensive ocean voyages. They were found, and in lesser numbers are still found, throughout South-East Asia and India, but primarily in China. Found more broadly today is a growing number of modern recreational junk-rigged sailboats.
The term junk may be used to cover many kinds of boat—ocean-going, cargo-carrying, pleasure boats, live-aboards. They vary greatly in size and there are significant regional variations in the type of rig, however they all employ fully battened sails.
The term may stem from the Chinese chuán (船, "boat; ship"), also based on and pronounced as [dzuːŋ] (Pe̍h-ōe-jī: chûn) in the Min Nan variant of Chinese, or zhōu (舟), the old word for a sailing vessel. Junk entered the English language in the 17th century through the Portuguese junco from the Malay jong or Javanese djong. The modern Standard Chinese word for an ocean-going wooden cargo vessel is cáo (艚). Views diverge on whether the origin is from a dialect of Chinese; Pierre-Yves Manguin, amongst others, points to a probable Old Javanese origin. European writings from 1345 through 1601 use a variety of related terms, including jonque (French), ioncque (Italian), iuncque (Spanish), and ionco (Dutch).
The historian Herbert Warington Smyth considered the junk as one of the most efficient ship designs, stating that "As an engine for carrying man and his commerce upon the high and stormy seas as well as on the vast inland waterways, it is doubtful if any class of vessel… is more suited or better adapted to its purpose than the Chinese or Indian junk, and it is certain that for flatness of sail and handiness, the Chinese rig is unsurpassed."
The structure and flexibility of junk sails make the junk fast and easily controlled. The sails of a junk can be moved inward toward the long axis of the ship. In theory this closeness of what is called sheeting allowed the junk to sail into the wind. In practice, evidenced both by traditional sailing routes and seasons and textual evidence  junks could not sail well into the wind.
Classic junks were built of softwoods (although after the 17th century of teak in Guangdong) with the outside shape built first. Then multiple internal compartment/bulkheads accessed by separate hatches and ladders, reminiscent of the interior structure of bamboo, were built in. Traditionally, the hull has a horseshoe-shaped stern supporting a high poop deck. The bottom is flat in a river junk with no keel (similar to a sampan), so that the boat relies on a daggerboard, leeboard or very large rudder to prevent the boat from slipping sideways in the water. Ocean-going junks have a curved hull in section with a large amount of tumblehome in the topsides. The planking is edge nailed on a diagonal. Iron nails or spikes have been recovered from a Canton dig dated to circa 221 BC. For caulking the Chinese used a mix of ground lime with Tung oil together with chopped hemp from old fishing nets which set hard in 18 hours, but usefully remained flexible. Junks have narrow waterlines which accounts for their potential speed in moderate conditions, although such voyage data as we have indicates that average speeds on voyage for junks were little different from average voyage speeds of almost all traditional sail, i.e. around 4–6 knots. The largest junks, the treasure ships commanded by Ming dynasty Admiral Zheng He, were built for world exploration in the 15th century, and according to some interpretations may have been over 120 metres (390 ft) in length, or larger. This conjecture was based on the size of a rudder post that was found and misinterpreted, using formulae applicable to modern engine powered ships. More careful analysis shows that the rudder post that was found is actually smaller than the rudder post shown for a 70' long Pechili Trader in Worcester's "Junks and Sampans of the Yangtze".
Another characteristic of junks, interior compartments or bulkheads, strengthened the ship and slowed flooding in case of holing. Ships built in this manner were written of in Zhu Yu's book Pingzhou Table Talks, published by 1119 during the Song dynasty. Again, this type of construction for Chinese ship hulls was attested to by the Moroccan Muslim Berber traveler Ibn Battuta (1304–1377 AD), who described it in great detail (refer to Technology of the Song dynasty). Although some historians have questioned whether the compartments were watertight, most believe that watertight compartments did exist in Chinese junks because although most of the time there were small passageways (known as limber holes) between compartments, these could be blocked with stoppers and such stoppers have been identified in wrecks. All wrecks discovered so far have limber holes; these are different from the free flooding holes that are located only in the foremost and aftermost compartments, but are at the base of the transverse bulkheads allowing water in each compartment to drain to the lowest compartment, thus facilitating pumping. It is believed from evidence in wrecks that the limber holes could be stopped either to allow the carriage of liquid cargoes or to isolate a compartment that had sprung a leak.
Benjamin Franklin wrote in a 1787 letter on the project of mail packets between the United States and France:
As these vessels are not to be laden with goods, their holds may without inconvenience be divided into separate apartments, after the Chinese manner, and each of these apartments caulked tight so as to keep out water.— Benjamin Franklin, 1787
In 1795, Sir Samuel Bentham, inspector of dockyards of the Royal Navy, and designer of six new sailing ships, argued for the adoption of "partitions contributing to strength, and securing the ship against foundering, as practiced by the Chinese of the present day". His idea was not adopted. Bentham had been in China in 1782, and he acknowledged that he had got the idea of watertight compartments by looking at Chinese junks there. Bentham was a friend of Isambard Brunel, so it is possible that he had some influence on Brunel's adoption of longitudinal, strengthening bulkheads in the lower deck of the SS Great Britain. Bentham had already by this time designed and had built a segmented barge for use on the Volga River, so the idea of transverse hull separation was evidently in his mind. Perhaps more to the point, there is a very large difference between the transverse bulkheads in Chinese construction, which offer no longitudinal strengthening, and the longitudinal members which Brunel adopted, almost certainly inspired by the iron bridge and boiler engineering in which he and his contemporaries in iron shipbuilding innovation were most versed.
Due to the numerous foreign primary sources that hint to the existence of true watertight compartments in junks, historians such as Joseph Needham proposed that the limber holes were stopped up as noted above in case of leakage. He addresses the quite separate issue of free-flooding compartments on pg 422 of Science and Civilisation in Ancient China:
Less well known is the interesting fact that in some types of Chinese craft the foremost (and less frequently also the aftermost) compartment is made free-flooding. Holes are purposely contrived in the planking. This is the case with the salt-boats which shoot the rapids down from Tzuliuching in Szechuan, the gondola-shaped boats of the Poyang Lake, and many sea going junks. The Szechuanese boatmen say that this reduces resistance to the water to a minimum, though such a claim makes absolutely no hydrodynamic sense, and the device is thought to cushion the shocks of pounding when the boat pitches heavily in the rapids, as it acquires and discharges water ballast rapidly supposedly just at the time when it is most desirable to counteract buffeting at stem and stern. As with too many such claims, there has been no empirical testing of them and it seems unlikely that the claims would stand up to such testing since the diameter or number of holes needed for such rapid flooding and discharging would be so great as to significantly weaken the vulnerable fore and aft parts of the vessel. The sailors say, as sailors all over the world are inclined to do when conjuring up answers to landlubbers' questions, that it stops junks flying up into the wind. It may be the reality at the bottom of the following story, related by Liu Ching-Shu of the +5th century, in his book I Yuan (Garden of Strange Things)
In Fu-Nan (Cambodia) gold is always used in transactions. Once there were (some people who) having hired a boat to go from east to west near and far, had not reached their destination when the time came for the payment of the pound (of gold) which had been agreed upon. They therefore wished to reduce the quantity (to be paid). The master of the ship then played a trick upon them. He made (as it were) a way for the water to enter the bottom of the boat, which seemed to be about to sink, and remained stationary, moving neither forward nor backward. All the passengers were very frightened and came to make offerings. The boat (afterwards) returned to its original state.
This, however, would seem to have involved openings which could be controlled, and the water pumped out afterwards. This was easily effected in China (still seen in Kuangtung and Hong Kong), but the practice was also known in England, where the compartment was called the 'wet-well', and the boat in which it was built, a 'well-smack'. If the tradition is right that such boats date in Europe from +1712 then it may well be that the Chinese bulkhead principle was introduced twice, first for small coastal fishing boats at the end of the seventeenth century, and then for large ships a century later. However, the wet well is probably a case of parallel invention since its manner of construction is quite different from that of Chinese junks, the wet well quite often not running the full width of the boat, but only occupying the central part of the hull either side of the keel.
More to the point  wet wells were apparent in Roman small craft of the 5th century CE.
Leeboards and centerboards, used to stabilize the junk and to improve its capability to sail upwind, are documented from a 759 AD book by Li Chuan. The innovation was adopted by Portuguese and Dutch ships around 1570. Junks often employ a daggerboard that is forward on the hull which allows the center section of the hull to be free of the daggerboard trunk allowing larger cargo compartments. Because the daggerboard is located so far forward, the junk must use a balanced rudder to counteract the imbalance of lateral resistance.
Other innovations included the square-pallet bilge pump, which was adopted by the West during the 16th century for work ashore, the western chain pump, which was adopted for shipboard use, being of a different derivation. Junks also relied on the compass for navigational purposes. However, as with almost all vessels of any culture before the late 19th century, the accuracy of magnetic compasses aboard ship, whether from a failure to understand deviation (the magnetism of the ship's iron fastenings) or poor design of the compass card (the standard drypoint compasses were extremely unstable), meant that they did little to contribute to the accuracy of navigation by dead reckoning. Indeed, a review of the evidence shows that the Chinese embarked magnetic pointer was probably little used for navigation. The reasoning is simple. Chinese mariners were as able as any and, had they needed a compass to navigate, they would have been aware of the almost random directional qualities when used at sea of the water bowl compass they used. Yet that design remained unchanged for some half a millennium. Western sailors, coming upon a similar water bowl design (no evidence as to how has yet emerged) very rapidly adapted it in a series of significant changes such that within roughly a century the water bowl had given way to the dry pivot, a rotating compass card a century later, a lubberline a generation later and gimbals seventy or eighty years after that. These were necessary because in the more adverse climatic context of north western Europe, the compass was needed for navigation. Had similar needs been felt in China, Chinese mariners would also have come up with fixes. They didn't.
Junks employed stern-mounted rudders centuries before their adoption in the West for the simple reason that Western hull forms, with their pointed sterns, obviated a centreline steering system until technical developments in Scandinavia created the first, iron mounted, pintle and gudgeon 'barn door' western examples in the early 12th century CE. A second reason for this slow development was that the side rudders in use were, contrary to a lot of very ill-informed opinion, extremely efficient. Thus the junk rudder's origin, form and construction was completely different in that it was the development of a centrally mounted stern steering oar, examples of which can also be seen in Middle Kingdom (c.2050–1800 BCE) Egyptian river vessels. It was an innovation which permitted the steering of large ships and due to its design allowed height adjustment according to the depth of the water and to avoid serious damage should the junk ground. A sizable junk can have a rudder that needed up to twenty members of the crew to control in strong weather. In addition to using the sail plan to balance the junk and take the strain off the hard to operate and mechanically weakly attached rudder, some junks were also equipped with leeboards or dagger boards. The world's oldest known depiction of a stern-mounted rudder can be seen on a pottery model of a junk dating from before the 1st century AD, though some scholars think this may be a steering oar; a possible interpretation given is that the model is of a river boat that was probably towed or poled.
From sometime in the 13th to 15th centuries, many junks began incorporating "fenestrated" rudders (rudders with large diamond-shaped holes in them), probably adopted to lessen the force needed to direct the steering of the rudder.
The rudder is reported to be the strongest part of the junk. In the Tiangong Kaiwu "Exploitation of the Works of Nature" (1637), Song Yingxing wrote, "The rudder-post is made of elm, or else of langmu or of zhumu." The Ming author also applauds the strength of the langmu wood as "if one could use a single silk thread to hoist a thousand jun or sustain the weight of a mountain landslide."
The first records of junks can be found in references dating to the Han dynasty (220 BCE–200 CE).
The 3rd century book "Strange Things of the South" (南州異物志) by Wan Chen (萬震) describes junks capable of carrying 700 people together with 260 tons of cargo ("more than 10,000 "斛"). He explains the ship's design as follows:
The four sails do not face directly forward, but are set obliquely, and so arranged that they can all be fixed in the same direction, to receive the wind and to spill it. Those sails which are behind the most windward one receiving the pressure of the wind, throw it from one to the other, so that they all profit from its force. If it is violent, (the sailors) diminish or augment the surface of the sails according to the conditions. This oblique rig, which permits the sails to receive from one another the breath of the wind, obviates the anxiety attendant upon having high masts. Thus these ships sail without avoiding strong winds and dashing waves, by the aid of which they can make great speed— Wan Chen, 
A 260 CE book by Kang Tai (康泰) also described ships with seven masts, traveling as far as Syria.
The great trading dynasty of the Song employed junks extensively. The naval strength of the Song, both mercantile and military, became the backbone of the naval power of the following Yuan dynasty. In particular the Mongol invasions of Japan (1274–84), as well as the Mongol invasion of Java, essentially relied on recently acquired Song naval capabilities.
The enormous dimensions of the Chinese ships of the Medieval period are described in Chinese sources, and are confirmed by Western travelers to the East, such as Marco Polo, Ibn Battuta and Niccolò da Conti. According to Ibn Battuta, who visited China in 1347:
…We stopped in the port of Calicut, in which there were at the time thirteen Chinese vessels, and disembarked. On the China Sea traveling is done in Chinese ships only, so we shall describe their arrangements. The Chinese vessels are of three kinds; large ships called chunks (junks), middle sized ones called zaws (dhows) and the small ones kakams. The large ships have anything from twelve down to three sails, which are made of bamboo rods plaited into mats. They are never lowered, but turned according to the direction of the wind; at anchor they are left floating in the wind.
A ship carries a complement of a thousand men, six hundred of whom are sailors and four hundred men-at-arms, including archers, men with shields and crossbows, who throw naphtha. Three smaller ones, the "half", the "third" and the "quarter", accompany each large vessel. These vessels are built in the towns of Zaytun (a.k.a. Zaitun; today's Quanzhou; 刺桐) and Sin-Kalan. The vessel has four decks and contains rooms, cabins, and saloons for merchants; a cabin has chambers and a lavatory, and can be locked by its occupants.This is the manner after which they are made; two (parallel) walls of very thick wooden (planking) are raised and across the space between them are placed very thick planks (the bulkheads) secured longitudinally and transversely by means of large nails, each three ells in length. When these walls have thus been built the lower deck is fitted in and the ship is launched before the upper works are finished.
The largest junks ever built were possibly those of Admiral Zheng He, for his expeditions in the Indian Ocean. According to Chinese sources, the fleet for Zheng's 1405 expedition comprised nearly 30,000 sailors and over 300 ships at its height.
The dimensions of Zheng He's ships according to ancient Chinese chronicles are disputed by modern scholars (see below):
Some recent research suggests that the actual length of the biggest treasure ships may have been between 390–408 feet (119–124 m) long and 160–166 feet (49–51 m) wide, while others estimate them to be 200–250 feet (61–76 m) in length.
In 1661, a naval fleet of 400 junks and 25,000 men led by the Ming loyalist Zheng Chenggong (Cheng Ch'eng-kung in Wade–Giles , known in the West as Koxinga), arrived in Taiwan to oust the Dutch from Zeelandia. Following a nine-month siege, Cheng captured the Dutch fortress Fort Zeelandia. A peace treaty between Koxinga and the Dutch Government was signed at Castle Zeelandia on February 1, 1662, and Taiwan became Koxinga's base for the Kingdom of Tungning.
Nusantaran archipelago is also known as the producer of large junks (Javanese: Djong Jawa / Jung Jawa). Portuguese account said about how Javanese people already had advanced civilization when they arrived:
(The Javanese) are all men very experienced in the art of navigation, to the point that they claim to be the most ancient of all, although many others give this honor to the Chinese, and affirm that this art was handed on from them to the Javanese. But it is certain that they formerly navigated to the Cape of Good Hope and were in communication with the east coast of the island of San Laurenzo (Madagascar), where there are many brown and Javanized natives who say they are descended from them.— Diogo de Couto, Decada Quarta da Asia
Duarte Barosa reported that the ships from Java, which has four masts, are very different from Portuguese ships. It is made of very thick wood, and as the ship gets old, they fix it with new boards and in this style they have four closing boards, stacked together. The rope and the sail is made by osier. The Javanese junks is made using jaty/jati wood (teak) at the time of this report (1512), at that time Chinese junks is still using softwood as the main material. The Javanese ship's hull is formed by joining planks to the keel and then to each other by wooden dowels, without using either a frame (except for subsequent reinforcement), nor any iron bolts or nails. The vessel was similarly pointed at both ends, and carried two oar-like rudders and a lateen-rigged sail. It differed markedly from the Chinese vessel, which had its hull fastened by strakes and iron nails to a frame and to structurally essential bulkheads which divided the cargo space. The Chinese vessel had a single rudder on a transom stern, and (except in Fujian and Guangdong) they had flat bottoms without keels.
Encounter of giant Djong ship occurred before the invasion of Malacca. Passing by Pacem (Samudera Pasai) the Portuguese came across a very large junk, larger in fact than even their flagship, the Flor do Mar, could not reach it. The Portuguese currently has one squadron (40-43 ships). The Portuguese ordered it to halt but it promptly opened fire on the fleet, after which the Portuguese quickly followed suit. Reported by Gaspar Correia:
"Because the junco started the attack, the Governor approached him with his entire fleet. The Portuguese ships began firing on the junco, but it had no effect at all. Then the junco sailed away .... The Portuguese ships then fired on the junco masts .... and the sails are falling. Because it's so tall, our people dare not board it, and our shots did not spoil it one bit because the junco has four layers of board. Our largest cannon was only able to penetrate no more than two layers ... Seeing that, the Governor ordered his nau (carrack) to move to the side of junco. (Portuguese Ship) This is Flor de la Mar, the highest Portuguese ship. And while trying to climb the junco, the rear of the ship could barely reach its bridge. The junco's crew defended themselves so well that the Portuguese ships were forced to sail away from the ship again. (After two days and two nights of fighting) the governor decides to break the two rudders at the side of the vessel. Only then did the junco surrender."— Albuquerque
Once aboard, the Portuguese found a member of the royal family of Pacem, whom Albuquerque hoped he could exchange for the Portuguese prisoners.
In January 1513 Paty Onuz, Patih Yunus or Pate Unus tried to surprise Malacca, brought about 100 ships with 5,000 men, Javanese from Jepara and Palembang; Although defeated, Patih Unus sailed home and beached his warship as a monument of a fight against men he called the bravest in the world, his exploit winning him a few years later the throne of Demak. In a letter to Afonso de Albuquerque, from Cannanore, 22 Feb. 1513, Fernao Peres de Andrade, the Captain of the fleet that routed Pate Unus, says:
"The junk of Pate Unus is the largest seen by men of these parts so far. It carried a thousand fighting men on board, and your Lordship can believe me . . . that it was an amazing thing to see, because the Anunciada near it did not look like a ship at all. We attacked it with bombards, but even the shots of the largest did not pierce it below the water-line, and (the shots of) the esfera (an old large kind of cannon) I had in my ship went in but did not pass through; it had three sheathings, all of which were over a cruzado thick. And it certainly was so monstrous that no man had ever seen the like. It took three years to build, as your Lordship may have heard tell in Malacca concerning this Pate Unus, who made this armada to become king of Malacca."— Fernao Peres de Andrade, Suma Oriental
Giovanni da Empoli (a Florentine merchant) said that in the land of Java, a junk is no different in its strength than a castle, because it had three and four boards, one above the other, which cannot be harmed with artillery. They sail with their women, children, and family, and everyone keeps his room by himself.
Niccolò da Conti in relating his travels in Asia between 1419 and 1444, matter-of-factly describes huge junks of about 2,000 tons:
They make ships larger than ours, about 2,000 tons in size, with five sails and as many masts. The lower part is made of three decks, so as to better resist storms, which occur frequently. These ships are separated into several compartments, so that if one is touched during a storm, the others remain intact.— Niccolò da Conti, 
Also, in 1456, the Fra Mauro map described the presence of junks in the Indian Ocean as well as their construction:
The ships called junks (lit. "Zonchi") that navigate these seas carry four masts or more, some of which can be raised or lowered, and have 40 to 60 cabins for the merchants and only one tiller. They can navigate without a compass, because they have an astrologer, who stands on the side and, with an astrolabe in hand, gives orders to the navigator.— Text from the Fra Mauro map, 09-P25, 
Fra Mauro further explains that one of these junks rounded the Cape of Good Hope and travelled far into the Atlantic Ocean, in 1420:
About the year of Our Lord 1420 a ship, what is called an Asian Junk (lit. "Zoncho de India"), on a crossing of the Sea of India towards the "Isle of Men and Women", was diverted beyond the "Cape of Diab" (Shown as the Cape of Good Hope on the map), through the "Green Isles" (lit. "isole uerde", Cabo Verde Islands), out into the "Sea of Darkness" (Atlantic Ocean) on a way west and southwest. Nothing but air and water was seen for 40 days and by their reckoning they ran 2,000 miles and fortune deserted them. When the stress of the weather had subsided they made the return to the said "Cape of Diab" in 70 days and drawing near to the shore to supply their wants the sailors saw the egg of a bird called roc, which egg is as big as an amphora.— Text from Fra Mauro map, 10-A13, 
Chinese junks were used extensively in Asian trade during the 16th and 17th century, especially to Southeast Asia and to Japan, where they competed with Japanese Red Seal Ships, Portuguese carracks and Dutch galleons. Richard Cocks, the head of the English trading factory in Hirado, Japan, recorded that 50 to 60 Chinese junks visited Nagasaki in 1612 alone.
These junks were usually three masted, and averaging between 200 and 800 tons in size, the largest ones having around 130 sailors, 130 traders and sometimes hundreds of passengers.
Large, ocean-going junks played a key role in Asian trade until the 19th century. One of these junks, Keying, sailed from China around the Cape of Good Hope to the United States and England between 1846 and 1848. Many junks were fitted out with carronades and other weapons for naval or piratical uses. These vessels were typically called "war junks" or "armed junks" by Western navies which began entering the region more frequently in the 18th century. The British, Americans and French fought several naval battles with war junks in the 19th century, during the First Opium War, Second Opium War and in between.
At sea, junk sailors co-operated with their Western counterparts. For example, in 1870 survivors of the English barque Humberstone shipwrecked off Formosa, were rescued by a junk and landed safely in Macao.
In 1938, E. Allen Petersen escaped the advancing Japanese armies by sailing a 36-foot (11 m) junk, Hummel Hummel, from Shanghai to California with his wife Tani and two White Russians (Tsar loyalists). In 1939, Richard Halliburton was lost at sea with his crew while sailing a specially constructed junk, Sea Dragon, from Hong Kong to the World Exposition in San Francisco.
In 1955, six young men sailed a Ming dynasty-style junk from Taiwan to San Francisco. The four-month journey aboard the Free China was captured on film and their arrival into San Francisco made international front-page news. The five Chinese-born friends saw an advertisement for an international trans-Atlantic yacht race, and jumped at the opportunity for adventure. They were joined by the then US Vice-Consul to China, who was tasked with capturing the journey on film. Enduring typhoons and mishaps, the crew, having never sailed a century-old junk before, learned along the way. The crew included Reno Chen, Paul Chow, Loo-chi Hu, Benny Hsu, Calvin Mehlert and were led by skipper Marco Chung. After a journey of 6,000 miles (9,700 km), the Free China and her crew arrived in San Francisco Bay in fog on August 8, 1955. Shortly afterward the footage was featured on ABC television's Bold Journey travelogue. Hosted by John Stephenson and narrated by ship's navigator Paul Chow, the program highlighted the adventures and challenges of the junk's sailing across the Pacific, as well as some humorous moments aboard ship.
In 1959 a group of Catalan men, led by Jose Maria Tey, sailed from Hong Kong to Barcelona on a junk named Rubia. After their successful journey this junk was anchored as a tourist attraction at one end of Barcelona harbor, close to where La Rambla meets the sea. Permanently moored along with it was a reproduction of Columbus' caravel Santa Maria during the 1960s and part of the 1970s.
In 1981, Christoph Swoboda had a 65 feet (LoA) Bedar built by the boatyard of Che Ali bin Ngah on Duyong island in the estuary of the Terengganu river on the East coast of Malaysia. The Bedar is one of the two types of Malay junk schooners traditionally built there. He sailed this junk with his family and one friend to the Mediterranean and then continued with changing crew to finally finish a circumnavigation in 1998. He sold this vessel in 2000 and in 2004 he started to build a new junk in Duyong with the same craftsmen: the Pinas (or Pinis) Naga Pelangi, in order to help keep this ancient boat building tradition alive. This boat finished to be fitted out in 2010 and is working as a charter boat in the Andaman and the South China Sea.