Ship models from the Han period show a sternpost-mounted rudder, a major step beyond steering oars. This change mattered because a rudder fixed to the stern gave better control on larger vessels and in stronger currents. It helped set the technical base for later ocean-going Chinese ship types.
By the early medieval period, Chinese sources and later scholarship describe ships being strengthened and divided internally, moving toward compartment-style hulls. The basic idea was structural and safety-related: separating the inside of a hull helps limit flooding and stiffen the ship’s frame. This concept would later become the watertight bulkhead system associated with junks.
During the Song dynasty, seaports and overseas trade grew in scale, pushing builders to create vessels that could carry more cargo and survive longer voyages. This economic pressure made practical innovations valuable—especially features that improved stability and reduced the chance of sinking. Ship design changes in this era are closely tied to the growth of long-distance maritime commerce.
In Pingzhou Ketan, Zhu Yu described ship hulls built with internal bulkheads that created watertight compartments. The key safety benefit was damage control: if one section flooded, the rest of the ship could still provide buoyancy. This is one of the clearest early written accounts linking Chinese junk design to compartmentalized, safer ocean travel.
Archaeological finds from Southern Song shipwrecks show that large merchant vessels were built with multiple internal partitions. These remains support the idea that bulkheaded construction was not only described in texts, but also used in real working ships. Physical evidence matters because it shows how builders turned the concept into durable ocean-going hulls.
A major Southern Song seagoing junk (the “Quanzhou ship”) was discovered in 1973 in Quanzhou Bay and excavated in 1974. The find became a landmark for understanding Chinese ship design because much of the lower hull survived. It provided a rare, measurable example of how ocean-going ships were built for maritime trade.
Study of the Quanzhou ship showed 12 bulkheads dividing the hull into 13 compartments, demonstrating true watertight subdivision in an ocean-going junk. This mattered for both safety and strength: compartments can slow flooding and also stiffen the hull against bending in waves. The ship became a key reference point for Song-era shipbuilding capabilities.
The Southern Song merchant shipwreck known as Nanhai No. 1 was discovered in 1987. It is important to ship design history because the wreck preserves structural features of a large trading vessel, including internal compartment divisions. The site also shows how ship technology supported long-distance maritime commerce through heavy cargo capacity.
Research in the International Journal of Nautical Archaeology analyzed construction details of the Quanzhou ship, including sealing materials used in its planked hull. These technical studies help explain how bulkheads and plank seams could be made water-resistant in practice. Scholarly publication also made the ship’s evidence easier to evaluate and compare internationally.
In 2007, Nanhai No. 1 was raised in an integral recovery and moved for preservation and excavation. Recovering a whole hull section allows closer study of bulkheads, planking, and compartment spacing that cannot be seen from scattered timbers. This kind of conservation work turns an underwater discovery into long-term evidence for shipbuilding history.
On 2010-11-15, UNESCO’s Intergovernmental Committee approved “Watertight Bulkhead Technology of Chinese Junks” for the List of Intangible Cultural Heritage in Urgent Need of Safeguarding. This marked a shift from viewing bulkheads only as an old invention to recognizing the living craft skills needed to build and maintain them. The decision linked historical ship design to modern heritage preservation efforts.
Major conservation and excavation work on Nanhai No. 1 progressed over the 2010s and early 2020s, with reports describing the project concluding in 2023. This closing stage matters because it produced detailed measurements and observations of compartments and hull structure, strengthening what historians can say about Song-era ocean-going junks. The end result is a clearer, evidence-based understanding of how bulkheaded junk design supported Chinese maritime expansion.
Development of Chinese ship design: watertight bulkheads and the ocean-going junk (10th–15th centuries)