I hit the starting mark — what exactly do I have to do to clear it?
Touching a mark breaks Rule 31, and a One-Turn Penalty clears it. Under Rule 44.2 that turn must be one full turn including one tack and one gybe, taken promptly after getting well clear of other boats. The rule doesn't measure the shape of your circle — it counts those two manoeuvres. Miss either one and the penalty is not complete and you remain liable.
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<p><a href="https://sailing.kiwi.nz/v/2aP8aiEGIs8/">Source: Sailing Kiwi</a></p>