long narrow vessel with two masts
艜 refers to a specific type of long, narrow sailing vessel with two masts.
艜 combines 舟 (boat) with 帶 (belt, sash), likely as a phono-semantic compound where 帶 contributes the sound and the idea of something long and narrow, fitting the vessel's shape.
A boat (舟) that is long and narrow like a belt or sash (帶): a two-masted vessel.
For タイ, imagine tying a long narrow boat to a dock with a thick tie: tie -> タイ, and the boat is secured like a belt.
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