I hailed for room — why didn't the other boat have to give it?
Rule 20 only entitles you to room to tack at a genuine obstruction, when you need to make a substantial course change, and you must hail loud enough to be heard. A bad hail, a non-obstruction, or hailing when you could simply duck the other boat — none of those entitle you to room.
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<p><a href="https://sailing.kiwi.nz/upwind/case-10-calling-room-wrong/">Source: Sailing Kiwi</a></p>