Sailing Conditions in the Pacific

Many early accounts describe canoes more than 15 m long carrying 30 to 50 people and a few larger ones carrying more than 100 people. Other reports mention the high speeds of lightly loaded canoes, about 10 knots with the wind on the beam. There are also many mentions of voyages of more than 800 km, and flotillas of many canoes. One of the critical details was the sealed hull, others the warm water, the availability of rain and the use of dried provisions for long journeys. Pâris (1841) mentions that breadfruit was fermented to make it sugary and then baked into hard cakes which kept indefinitely at sea. In the tropical Pacific, the flying fish leap into the boat at night, especially if an oil-nut can be lit to make a light, as modern voyagers describe. If we survey the whole of Polynesia, Micronesia and Melanesia, there are only a few areas that would have been out of reach of exploration with such boats as we know of, equipped as we know they could have been. Recently there have been successful reenactments of several of the voyages described in myths (Finney 1985; Irwin 1989). The difficult laps were on either side of Easter Island and to islands around New Zealand, and yet people successfully reached even the Chatham Islands in prehistoric times.

Making use of periods of mixed winds (Finney 1985), a month’s journey of exploration eastwards between 20°N and 20°S in the Pacific Ocean would easily cover about 1000 km. To be on the safe side a drift back downwind might take two months. Carbohydrate for three months for eight people would weigh about 300 kg, which is not an unreasonable load for a 12 m single-outrigger canoe. Double canoes would carry a tonne with ease, but because of the larger investment in construction labour they were more suitable for carrying family, plants, animals and cargo to places already discovered.

Voyaging was always seasonal, even when not forced by the winds, because the stars are seasonal. Charts of the tropical Pacific prepared for the days of sail show the trade winds blowing fairly strongly but not consistently all the year from the north-east to the north of the equator and from the south-east to the south of the equator. However, from October to June over the whole area of Melanesia and Polynesia to the south of the equator, from New Guinea to the Tuamotus, the winds blow from the north-east about as frequently as they do from the south-east. With normal trade winds the prevailing surface currents average 15 to 25 km per day (Figure 3) and can assist sailing downwind, but are not very significant for a boat that covers 50- 150 km per day. As far east as about Tonga, westerly winds accompany the cyclones in December to March. In Micronesia the winds are more consistently from the east or north-east and cyclones are less predictable. In Cook’s account of Tahiti, Tupaia said that his people knew very well how to make use of the westerly winds (Lewis 1972: 297). In Polynesia, westerlies are more likely in December and January. Bearing all this in mind, the obvious time to set out eastwards into the unknown would have been the beginning of December, starting with a westerly wind, and always with the expectation of an easy return home.

Voyages by outrigger canoe would ultimately have been limited by the sea-water surface temperature. Apart from New Zealand, the Austronesian colonization was all within the isotherm of 21°C (70°F) in the warmest season. The Austronesian agricultural crops were mostly limited to this zone, and in New Zealand different storage methods and crops, such as hardy varieties of sweet potato, were used at the limits imposed by cold. The whole culture — plants, housing, dress, boat design and aquatic lifestyle — was adapted to the warm terrestrial climate.

Figure 3. Drift currents in the Pacific with the length of each arrow indicating velocity in nautical miles per day. (1 km approx. = 0.625 nautical mile). Seasonal differences (given by Lewis 1972:102) are small.

Figure 3. Drift currents in the Pacific with the length of each arrow indicating velocity in nautical miles per day. (1 km approx. = 0.625 nautical mile). Seasonal differences (given by Lewis 1972:102) are small.

Boat size was not a problem, as large canoes of 25 m long could carry 30 or 50 people plus cargo. Speed was not a problem either as the small single outrigger canoes (the flying proas of Micronesia) could do up to 20 knots but were limited to a few weeks sailing. The problem was that such speeds would quickly smash up a large canoe in a heavy sea because the construction materials could not stand the repeated stresses. The upper limit was set by the scale effect acting on the limits of the materials, as for wooden aircraft, windmills and all similar structures. The best compromise seems to have been the travelling canoe of medium size, large enough for one or two families.