A boat came up from clear astern, established a leeward overlap, then luffed me up — can she really do that?
Yes — to a point. Under Rule 11, the windward boat (you) must keep clear of the leeward boat. Even though she gained the overlap from clear astern within two of your hull lengths, Rule 17 only stops her sailing above her proper course — and a straight line to the finish IS her proper course, so she's entitled to luff up to it. Rule 16.1 only asks her to give you room as she turns, and she did. Hold your course and the foul is yours. (World Sailing Case 46.)
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<p><a href="https://sailing.kiwi.nz/run/case-46-luff-up-to-proper-course/">Source: Sailing Kiwi</a></p>