Rafts, skin boats, dug-out canoes and particularly sewn boats were all clearly so widespread over Asia when archaeological and historical records began that they must predate the Austronesians. We might try to list the features of characteristic recent Austronesian boats and decide which ones can be considered as uniquely Austronesian.
The basis of all Austronesian boats, beyond the simple dug-out and the raft, is the lashed-lug construction technique, in which projecting perforated lugs are left in the dug-out base of the hull and on the additional planks which are sewn on to its sides (Figure 1). Thwarts and flexible ribs are lashed down to these lugs, so further compressing the planks added to the hull. The same lashing technique holds down the transverse booms for the outrigger and may well have originated for that purpose. The ends are each closed by a stem and stern piece carved from a fork which runs a little way along the sides of the hull. Early Austronesian boats did not necessarily have outriggers; excellent fishing boats and especially war-canoes with a single hull persist ethnographically in Botel Tobago and as the mon of the Solomons. This lashed-lug technique spread into the Pacific, sometimes with stitches through holes in the planks or through projections from the planks, and sometimes strengthened by bindings between projections on the inside of the planks. The seams could be packed with absorbent fibre that expanded when wet, sometimes the plank edges were polished to a perfect fit by rubbing them together, and sometimes the seams were overlaid by padded laths under the stitches. Until the curved metal chisel or other tools became available for drilling straight dowel holes, the joints were sewn and sealed with resin. This technique is widespread from Hawaii to Madagascar and throughout Micronesia, Polynesia and Indonesia. It was modified in only two ways; (a) by modernization; (b) by a different, probably very ancient, tradition of long thin canoes without outriggers in which men often stand to propel the boat along, e.g. Asian dragon boats, Asmat canoes and the boats incised on the sides of Dong Son drums.
(a) The 5-part canoe; (b) exploded view of the upper hull; (c) (d) and (e) sections of hulls of increasing complexity.
(c) Downward compression; (d) arch compression; (e) combined downward and flexible rib construction. The details and variations on these themes were different for different island groups.
(The drawings are based on modern Indonesian canoes — the use of dowels is not a prehistoric feature, as indicated in the text.)
Figure 2. The rig of a single-outrigger travelling canoe of Satawal, Caroline Islands, from Pâris (1841).
The combination of single outrigger and triangular sail pushed up by a tilting pole (Horridge 1986:86) was unique to the Austronesians. The outrigger boom is connected to the float by vertical and oblique connector rods (Figure 1) that are hammered into the soft timber float. Together with the rig and the way of sailing a single-outrigger canoe with the outrigger float to windward, we observe that the Austronesians had a sailing machine with a combination of features that, once perfected, would always have to be built and sailed in the same way. The two-boom triangular sail (see Figure 2) is also unique to the Austronesians in its Austronesian form. This sail pivots on its point, can be tilted fore and aft to steer the boat (as on a windsurfer), is spread transversely across the boat to go downwind, and when the sheet is pulled in and towards the stern the boat is almost self-steering fairly close to the wind. There was therefore no need to invent the fixed rudder, and the sail can be pushed up with a movable prop so there was no need to invent the pulley or the fixed mast with fixed shrouds and stays. In fact, the rig does not allow shrouds and is therefore totally different in principle from the rigs with fixed mast that might have spread eastwards much later from the Indian Ocean.
When we ask why the outrigger canoe plus tilting sail technology was evolved, there are so many interacting factors that the only quick answer seems to be that there was no other solution to all the simultaneous challenges that had to be met. This answer itself is sufficient to explain the remarkably conservative copying of the successful designs for generation after generation. Some of the numerous technical factors which make the technology appropriate are as follows:
- Available natural materials are wood, which is good in compression, and plaited fibres such as rotan or palm fibre sennit which are good in tension.
- Cellulose-based materials are essentially weak for construction and therefore loads must be distributed, avoiding stress concentrations. This consideration governed the whole design.
- Cellulose-based materials rot and the whole boat has to be dismantled for replacement of parts and sometimes for drying out when temporarily not in use.
- At sea the main engineering problem is to avoid fatigue fractures caused by the working of the waves and wind, especially if the outrigger is in the water. The solution was to use fibrous materials and to make the structure flexible, more like a basket chair than a rigid four-legged table.
- As with an eggshell, the double curvature of the hull gives an unexpected bonus in strength and stiffness.
- Without a pulley (which they did not have) the size of the sail is limited by its weight when wet and by the strength of the pole that pushes it up. To maximize the compression strength of the pole, it was free to pivot on its end so that lateral forces were all transferred to the stay in tension and there were no bending forces on the pole.
- Planks swell in width when wet and the lashing fibre shrinks, so the lashed-lug construction tightened up at sea; compressing the planks together.
The basic principles of sewn and lashed-lug construction are remarkably homogeneous across the whole Austronesian range, except for subsequent influences that have spread eastwards from the Indian Ocean and as a result of the introduction of metal tools and pulleys into Indonesia and the Philippines in historic times. A significant detail is that traditional Pacific canoes had sewn seams with the internal lugs often taking the form of a raised ridge along the whole seam. In the Southeast Asian Archipelago sewing was replaced over the past 2000 years by edge-to-edge planking with internal dowels. Another detail is that Pacific traditional canoes have several short straight sticks hammered into the outrigger float to connect it to the outrigger boom. In contrast, in Indonesia several later designs of connector were adapted to the use of giant bamboo for the floats. In the Southeast Asian Archipelago, except for Madura, the triangular rig gave way to the trapezoid sail on a fixed mast and this meant also the adoption of the fixed quarter rudder. The limit of spread of these technological changes corresponds well to the limit of spread of metal tools and other goods by traders from Asia. The conclusion is that there was little opportunity or reason for technological change in the Pacific after the basic design was taken east of Indonesia.
There are also social factors. Like a house or fish-trap, a boat is a shared structure from which many gain an advantage. In Austronesian communities, typically, every maritime village has its own boat design and they say that the details of construction have been handed down from their ancestors. The apprentices learn the exact way to build every detail and the conservative attitude is reinforced by memorized chants that must be repeated without error, and by universal belief that any deviation from tradition would cause a disaster at sea. Because the use of them is dangerous, boats are particularly conservative structures and all cultures adhere to their own proven designs. Rigs are more easily copied than hull structures (Horridge 1986). When changes in design are introduced they are not admitted. In consequence, boatbuilding techniques may survive unchanged for 1000 years or may be quickly modified in a single generation, as happens when designs are transferred from elsewhere. There is a negative side to this valuable conservation of the best available designs: inventions that are not immediately needed do not get invented, witness the pulley, the fixed rudder, the keel, the jib sail, the fixed mast or the multiple mast in the Pacific.