Up one level to Eastern Walu-Siwaish (here)
The cognate set for ‘PAN’ *layaR ‘sail’ in Blust’s ACD (here) (includes the MP forms under Dempwolff’s *layaɣ ‘sail’ plus two Formosan items:
Kavalan RayaR sail of a raft or boat; cloth around a threshing machine Paiwan la-laya a flag, banner pu-la-laya to raise a flag, fly a banner excerpt from Blust’s ACD
Elsewhere, in a note under PAn *qabang ‘boat, canoe’ (here), Blust wrote: “Given the independent evidence for PAn *layaR ‘sail’ we can be sure that PAn speakers had boats with sails. However, we cannot be certain that they possessed the outrigger, since *saRman ‘outrigger float’ and other terms connected with the outrigger canoe complex are reconstructible only to PMP. As noted in Blust (1999) the Austronesian settlement of Taiwan may have been accomplished with bamboo sailing rafts, leaving open the possibility that the *qabaŋ was a simple dugout canoe used on interior rivers.”
It is difficult to imagine how sailing rafts with neither outriggers nor a keel—traditional boats with keels are absent in East Asia—would fail to capsize in even moderately strong winds. Evidently Austronesian sailing boats with outriggers did not come into existence through the addition of outriggers to pre-existing saining boats: rather, the outrigger is a prerequisite to the invention of the Austronesian orientable sail. There is in fact evidence that until relatively recently the Formosans used sail-less boats with outriggers. The Atayals had small boats that they used to cross streams (Taintor 1874:34):
“The small boats which the savages use in crossing streams they call mangka. A boat is made by hollowing out a log of wood and fastening a board upon each side of it to prevent its capsizing. They have no oil and chunam for filling the cracks or seams, and hence have to bail constantly. A boat will carry two or three people”
The Basais and Kavalans had ‘huge’ sea-going rowing boats with outriggers fixed with vines which could carry up to 25 people and a large amount of cargo (Chien 2021).
For evidence that Austronesian sails are as old as PAN, Blust essentially relied on his assumption of the correctness of his 10-branch phylogeny: the term being reflected in languages of three of his primary branches, he assumed that *layaR was a PAN word. In my phylogeny, however, *layaR only occurs in Eastern Walu-Siwaish languages, and counts as a Proto-Eeastern Walu-Siwaish innovation. The invention of the sail has the character of a post-PAN technical improvement to the rowing boat with outriggers used by the Basais, Kavalans and Atayals. This makes it likely that the first Austronesians crossed from the mainland to Taiwan on sail-less rowing boats with outriggers, while the out-of-Taiwan event, which brought the MP languages to the Philippines and beyond, was effected with the help of newly-invented sails.
Blust, R. 1999. Subgrouping, circularity and extinction: some issues in Austronesian comparative linguistics. In: Elizabeth Zeitoun and Paul Jen-kuei Li (eds.) Selected Papers from the Eighth International Conference on Austronesian linguistics, 31-94. Taipei: Institute of Linguistics (preparatory office).
Chien Hung-yi (2020) From Bangka Canoe to Shechuan Junk: Commercial Activities along Northeastern Coastal Route (1650s-1750s). Taiwan Historical Research 27, 4:1-34.
Taintor, Edward C. (1874) The Aborigines of Northern Formosa: A Paper Read Before the North China Branch of the Royal Asiatic Society. Shanghai 1874. privately published.