CASE 81        

Summary of the Facts
Two boats, A and B, close reaching on starboard tack, approached a mark to be rounded to starboard. A entered the two-length zone clear ahead and to leeward of B, and tacked onto a close-hauled port-tack course in order to round the mark. B, still on starboard tack, collided with A, then on port tack, causing no damage. Both boats protested.
The protest committee decided that rule 18.1(b), one of the exceptions of rule 18, applied because just prior to the collision both boats were on opposite tacks and B had to tack to pass the mark on her proper course. Having decided that rule 18 did not apply, the protest committee disqualified A under rule 10.
A appealed on the grounds that rule 18.2(c) applied because the boats were not on a beat as they approached the mark, and that because rule 18.2(c) conflicted with rule 10, applying the preamble to Section C, B was required to keep clear once A had completed her tack.

Decision
Rule 18 applies when two boats on the same tack are about to round a mark, whether or not they are on a beat. Therefore, rule 18.2(c) applied, because A and B were on the same tack and A was clear ahead of B at the time she reached the two-length zone.
Rule 18.2(c) requires a boat clear astern to keep clear of a boat clear ahead until they have passed the mark unless the boat clear ahead passes head to wind. In that case rule 18.2(c) no longer applies and the boat that had been clear ahead becomes subject to rule 13 until she is on a closehauled course. At that moment rule 10 begins to apply. A broke rule 10, and therefore her appeal is denied.