Contemporary descriptions The contemporary inscription of Zheng He's ships in the Jinghai temple (靜海寺—
Jìng hǎi sì) inscription in Nanjing gives sizes of 2,000
liao (500
tons) and 1,500
liao (275 tons), which are far too low than would be implied by a ship of 444
chi () given by the
History of Ming. In addition, in the contemporary account of Zheng He's 7th voyage by Gong Zhen, says it took 200 to 300 men to handle one of Zheng He's ships. Ming minister Song Li indicated a ratio of 1 man per 2.5 tons of cargo, which would imply Zheng He's ships were 500 to 750 tons. The inscription on the tomb of Hong Bao, an official in Zheng He's fleet, mentions the construction of a 5,000
liao displacement ship.
5,000 liao ship In June 2010, a new inscription was found in Hong Bao's tomb, confirming the existence of the Ming dynasty's 5,000
liao ship. Xin Yuan'ou, a shipbuilding engineer and professor of the history of science at
Shanghai Jiao Tong University, argues that Zheng He's treasure ships could not have been 450 ft long, and suggests that they were probably closer to 200–250 ft (61–76 m) in length. Hsu Yun-Ts'iao does not agree with Xin Yuan'ou: Estimating the size of a 2,000
liao ship with the
Treatise of the Longjiang shipyard (龙江船厂志—
lóng jiāng chuánchǎng zhì) at Nanjing, the size is as follows: LOA , bottom's hull length , overhanging "tail" length , front depth , front width , mid-hull depth , mid-hull width , tail depth , tail width , and the length to width ratio is 7:1. Arabic Studies and Islamic Material Culture researcher
Dionisius A. Agius estimated a size of and maximum weight of 700 tons for the escort ships based on his observation of Arabic and Asian shipwrights, while for the flag ship, Agius estimates at very most, based on the with information about the ship's weight in literature and possible dimensions of the 15th century technologies. Tang Zhiba, Xin Yuan'ou, and Zheng Ming have calculated the dimensions of the 2,000
liao ship, obtaining a length of , width of , and draught of . Zheng Ming believes that the "Heavenly Princess Classics" depict 2,000
liao ships. André Wegener Sleeswyk extrapolated the size of
liao (料 — material) by deducing the data from mid-16th century Chinese river junks. He suggested that the 2,000
liao ships were
bao chuan (treasure ship), while the 1,500
liao ships were
ma chuan (horse ship). In his calculations, the treasure ships would have had a length of , a width of , and a height of . The horse ships would have a length of , a width of , and a height of . Richard Barker estimated that the treasure ships would have a length of , a width of , and a draught of . He estimated it using an assumed displacement of 3100 tons. Naval engineer and historian Xin Yuan'ou has argued that Zheng He's ships could not have been as large as recorded in the
History of Ming for the following reasons: • Ships of the dimensions given in the Ming shi [
History of Ming] would have been 15,000–20,000 tons according to his calculations, exceeding a natural limit to the size of a wooden ocean-going ship of about 7,000 tons displacement. • With the benefit of modern technology it would be difficult to manufacture a wooden ship of 10,000 tons, let alone one that was 1.5 to 2 times that size. It was only when ships began to be built of iron in the 1860s that they could exceed 10,000 tons. • Watertight compartments characteristic of traditional Chinese ships tended to make the vessels transversely strong but longitudinally weak. • A ship of these dimensions would need masts that were tall. Several timbers would have to be joined vertically. As a single tree trunk would not be large enough in diameter to support such a mast, multiple timbers would need to be combined at the base as well. There is no evidence that China had the type of joining materials necessary to accomplish these tasks. • A ship with 9 masts would be unable to resist the combined strength and force of such huge sails; she would not be able to cope with strong wind and would break. • It took four centuries (from the Renaissance to the modern era) for Western ships to increase in size from 1,500 to 5,000 tons displacement. For Chinese ships to have reached three or four times this size in just two years (from Emperor Yongle's accession in 1403 to the launch of the first expedition in 1405) was unlikely. • The 200 to 300 sailors as mentioned by Gong Zhen could not have managed a 20,000 ton ship. According to Xin, a ship of such size would have had to have a complement of 8,000 men. From the comments of modern scholars on Medieval Chinese accounts and reports, it is apparent that a wooden ship had a natural limit to her size, which going beyond would have made her structurally unsafe as well as causing a considerable loss of maneuverability, something the
Spanish Armada ships famously experienced. Beyond a certain size (about in length) a wooden ship is structurally unsafe. It was not until the mid to late 19th century that the length of the largest western wooden ship began to exceed , even this was done using modern industrial tools and iron parts. One suggestion for the 44
zhang size treasure ships, if they were built, was that they were used only for a display of imperial power by the emperor and imperial bureaucrats on the Yangtze River when on court business, including when reviewing Zheng He's actual expedition fleet. The Yangtze River, with its calmer waters, may have been navigable for such large but unseaworthy ships. Zheng He would not have had the privilege in rank to command the largest of these ships. Some of the largest ships of Zheng He's fleet were the 6 masted 2,000-
liao ships. This would give
burthen of 500 tons and a displacement tonnage of about 800 tons. Because they were built and based in Nanjing, and repeatedly sailed along the
Yangtze river (including in winter, when the water is low), their draught cannot exceed . It is also known that Zheng He's fleet visited
Palembang in Sumatra, where they needed to cross the
Musi river. It is unknown whether Zheng He's ships sailed as far as Palembang, or whether they waited on the shore in the
Bangka Strait while the smaller ships sailed at Musi; but at least the draught of the ship that reached Palembang could not have been more than .
Measurement conversion It is also possible that the measure of
zhang (丈) used in the conversions was mistaken. Seventeenth-century Ming records state that the European
East Indiamen and
galleons were 30, 40, 50, and 60
zhang (90, 120, 150, and 180 meters) in length. The length of a Dutch ship recorded in the
History of Ming was 30
zhang. If the
zhang is taken to be 3.2 meters, the Dutch ship would be long, an enormous increase over the largest Dutch ships of the time. The Dutch
Hongyi cannon was recorded to be more than 2
zhang (6.4 m or 21 ft) long. A comparative study by Hu Xiaowei (2018) concluded that 1
zhang would be equal to between 1.5 meters and 1.6 meters; this means the Dutch ship would be 45–48 m (147–157 ft) long and the cannon would be 3–3.2 m (9.8–10.5 ft) long. Taking the upper limit of 1.6 meters for 1
zhang, Zheng He's 44
zhang treasure ship would be long and wide, or 22
zhang long and 9
zhang wide if the
zhang is taken to be 3.2 m. It is known that the measuring unit during the Ming era was not unified: A measurement of East and West Pagoda in Quanzhou resulted in a
zhang unit of 2.5–2.56 m. According to Chen Cunren, one
zhang in the Ming Dynasty is only half a
zhang in modern times. == Structure ==