Shipbuilding
Shipbuilding
The greatest difficulty in determining history surrounding junks is that the majority of shipbuilders and their families are illiterate, both during the Ming and Qing dynasties and today, and most ancient archivers knew very little about the intricacies of building ships. Most shipbuilders also did not adhere to shipbuilding manuals due to their illiteracy, although the large body of resources that exist are from manuscripts containing shipbuilding manuals.8
Construction
Because there was no spinal keel in ocean-going junks, a flat bottom of planks was used. These were laid upon sandbags so that the increasing weight of the junk as it was being constructed could be adjusted accordingly on the sand. On the flat bottom, athwartships bulkheads were raised. Often these bulkheads were made of close-grained laurel, camphor-wood, nan-mu, or zhu-mu. Deck planks could be made of any wood. By splitting the hull into separate integral units, or using bulkhead construction, junks were able to develop water-tight bulkheads that both provided tolerance of flooding and also transportation of liquid cargo. Some junks also used free-flooding compartments that actually had holes purposely punctured in them. These were used by fishermen to bring in fresh, live fish and were also used by captains to raise and lower the level of the boat. These compartments could be emptied by bilge pumps that make use of the square-pallet chain-pump design. Five rows of split logs were placed longitudinally to provide strength. Depending on whether the vessel was to be a riverine or sea junk, the hull was either caulked with a mixture of tung oil and lime mixed with bamboo tow for riverine junks, or tung oil and fish oil for ocean vessels. According to Woodman, "Tung oil containes alphaelaeostearic acid which polymerises rapidly and provides a drying agent and medium, sealing the hull very effectively. Rot, where it did occur, was overcome by doubling the timbers, so such a hull was virtually indestructible."9
Alternate accounts record masts as traditionally made from one teak log strengthened by immersion in damp ground or as a fir that must have grown straight. If the natural size of the tree was not long enough, two pieces could be bound together by a series of iron bands. The masts were supported by bamboo or hemp ropes, which were resistant to chafe, decay and stretch, and have a high tensile strength. The sails were woven out of small sections of cloth. The sail was laterally stiffened by light bamboo battens, which were made of teak and camphor wood. Because the sails were actually made of bamboo battens with sections of cloth between them, they could be "hauled up and down rather like a set of open Venetian blinds covered with cloth."10 This means that the sails could be used partially open for small gales or fully open for large ones. Also, ships could sail even when there were holes punctured throughout the bamboo sails, whereas European canvas sails would fail to function in that condition. The battens also kept the sails taut and therefore more aerodynamic. Instead of using a square sail, the junk sails were fore-and-aft rig using a lug sail, allowing the junks to sail into the wind. A fore-and-aft rig sail is one which is not set perpendicular lengthwise to the ship, but rather set at an angle alongside the length of the ship. Sails could be set up so that they could be pivoted in order to catch the maximum capacity of the wind. However, this could produce a great amount of leeward drift, which can be corrected by means of a leeboard rudder.