Case 75
Definitions, Proper Course
Rule 10, On Opposite Tacks
Rule 14, Avoiding Contact
Rule 16.1, Changing Course
Rule 18.2(b), Mark-Room: Giving Mark-Room
Rule 18.4, Mark-Room: Gybing
When rule 18 applies, the rules of Sections A and B apply as well. When an inside overlapped right-of-way boat must gybe at a mark, she is entitled to sail her proper course until she gybes. A starboard-tack boat that changes course does not break rule 16.1 if she gives a port-tack boat adequate space to keep clear and the port-tack boat fails to take advantage of it promptly.
Two boats, S and P, were sailing directly downwind towards a leeward mark to be left to port. They had been overlapped for several lengths with S inside and slightly ahead. As S entered the zone, she luffed. As her bow came abreast of the mark she bore away to gybe, and there was contact, but no damage or injury. S protested P under rule 10 while P protested S under rule 18.

The protest committee disqualified P for breaking rule 10. P appealed, asserting that she had given S mark-room and that S had broken rule 18.4.

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At position 1, S reached the zone and P was required by rule 18.2(b) to give S mark-room thereafter. In addition, until S gybed P was required by rule 10 to keep clear of S. As S luffed, she was required by rule 16.1 to give P room to keep clear, and until she gybed S was also required by rule 18.4 to sail no farther from the mark than needed to sail her proper course. The mark-room that P was required to give S was the space S needed in the existing conditions to sail promptly to the mark in a seamanlike way. That space was a direct corridor from S1 to a position close to and alongside the mark on the required side. P gave S that room. However, because S had right of way she was not required to remain within that corridor; she was permitted to sail any course provided that she complied with rules 16.1 and 18.4.

S luffed gradually through approximately 45 degrees while sailing about three lengths forward, and P made no effort to keep clear. Shortly before position 2, S needed to act to avoid P. At that moment P broke rule 10. When S luffed after position 1, if P had acted promptly there was space for her to have manoeuvred in a seamanlike way to keep clear of S. Therefore S did not break rule 16.1.

When S gybed just after position 2, she had not sailed farther from the mark than needed to sail her proper course. Indeed, in the absence of P (the boat "referred to" in the definition Proper Course), S's proper course might well have been to sail even farther from the mark and higher than she did, so as to make a smoother, faster rounding and to avoid interference with her wind by being backwinded or blanketed by other boats ahead. Therefore S did not break rule 18.4.

Concerning rule 14, both boats broke the rule because there was contact and it was "reasonably possible" for each of them to avoid it. P is therefore disqualified under rule 14 as well as rule 10. However, S is exonerated because she was the right-of-way boat when the contact occurred and there was no damage or injury (see rule 14(b)).

P's appeal is dismissed. She was properly disqualified, and S did nothing for which she could be penalized.

USA 1976/195
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