Maritime Southeast Asian, Micronesian, Melanesian, Taiwanese indigenous peoples, and Polynesian peoples) continue to be the primary users of the outrigger boats. The simplest form of all ancestral Austronesian boats had five parts. The bottom part consists of single piece of hollowed-out log. At the sides were two planks, and two horseshoe-shaped wood pieces formed the prow and stern. These were "sewn" together with dowels and lashings. They had no central rudders but were instead steered using an oar on one side. The ancestral rig was the mastless triangular crab claw sail which had two booms that could be tilted to the wind. These were built in the double-canoe configuration or had a single outrigger on the windward side. In Island Southeast Asia, these developed into double outriggers on each side that provided greater stability. The triangular crab claw sails also later developed into square or rectangular tanja sails, which like crab claw sails, had booms spanning the upper and lower edges. Fixed masts also developed later in both Southeast Asia (usually as bipod or tripod masts) and Oceania. Early researchers like Heine-Geldern (1932) and Hornell (1943) once believed that catamarans evolved from outrigger boats, but modern authors specializing in Austronesian cultures like Doran (1981) and Mahdi (1988) now believe it to be the opposite. Two canoes bound together developed directly from minimal raft technologies of two logs tied together. Over time, the double-hulled canoe form developed into the asymmetric double canoe, where one hull is smaller than the other. Eventually the smaller hull became the prototype outrigger, giving way to the single outrigger canoe, which diverged into the reversible single outrigger canoe in Oceania. Finally, the single outrigger types developed into the double outrigger canoe (or trimarans). This would also explain why older Austronesian populations in Island Southeast Asia tend to favor double outrigger boats, as it keeps the boats stable when tacking. But they still have small regions where catamarans and single-outrigger boats are still used. In contrast, more distant outlying descendant populations in Micronesia, Polynesia, Madagascar, and the Comoros retained the double-hull and the single outrigger boat types, for the technology of double outriggers never reached them (exceptions being western Melanesia). To deal with the problem of the instability of the boat when the outrigger faces leeward when tacking, they instead developed the shunting technique in sailing, in conjunction with reversible single-outriggers. When Magellan's ships first encountered the