Case 88
Definitions, Keep Clear
Rule 10, On Opposite Tacks
Rule 14, Avoiding Contact
A boat may avoid contact and yet fail to keep clear.
Summary of the Facts
S and P, two keelboats about 24 feet (7 m) in length, approached each other on a windward leg, sailing at approximately the same speed in 12 to 15 knots of wind and "minimal" sea conditions. S was slightly ahead. When approximately three hull lengths away, S hailed "Starboard" and did so again at two hull lengths, but P did not respond or change course. At position 1 in the diagram both boats changed course at the same moment. S, fearing a collision, luffed sharply intending to tack and thereby minimize damage or injury, and P bore away sharply. As soon as she saw P bear away, S immediately bore away also. P, with her tiller turned as far to port as it would go, passed astern of S within two feet (0.6 m) of her. There was no contact. S protested under rule 10.

The protest committee decided that P did not break rule 10. It then considered whether S had broken rule 16.1 or 16.2 by luffing and then immediately bearing away. It concluded that she had not, after finding that her course changes did not affect P, which was already making a severe course change that would have been necessary even in the absence of S's actions. S's protest was dismissed, and she appealed.

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S's appeal is upheld. P is disqualified for breaking rule 10.

Rule 10 required P to "keep clear" of S. "Keep clear" means something more than "avoid contact"; otherwise the rule would contain those or similar words. Therefore, the fact that the boats did not collide does not necessarily establish that P kept clear. The definition Keep Clear in combination with the facts determines whether or not P complied with the rule. In this case, the key question raised by the definition is whether S was able to sail her course "with no need to take avoiding action".

The following considerations lead to the conclusions that P failed to keep clear of S and therefore broke rule 10:
  1. the courses of the boats when the incident began. They were on collision courses, which meant that at least one of them would have to change course.
  2. the distance between the boats at the moment both boats changed their courses. After position 1, if neither boat had changed course, P's bow would have struck the leeward side of S after the boats had sailed approximately two-thirds of a hull length.
  3. the estimated time remaining before contact. When both boats changed course there was very little time remaining before a collision would have occurred. For example, at a speed of five knots one of these boats would travel two-thirds of her length in 1.9 seconds. At six knots it would be 1.5 seconds.
  4. the extent of the course change needed by each boat to avoid a collision. This increased as the boats came closer. At the time P changed course, the change required was such that "with her tiller turned as far to port as it would go" she passed S's stern "within two feet" (0.6 m). At the same moment, the course change S would have needed to avoid P if P did not change course was approximately 90 degrees because S would have had to tack.
  5. the time required by either boat to make the necessary course change. This factor was itself determined by several others: the boat's weight and speed, her underwater hull shape, the size of her rudder, the sail handling required, and wind and sea conditions.

When the boats reached position 1 in the diagram, P was not keeping clear. A collision was imminent, and almost unavoidable, as shown by the fact that with helm hard over P passed less than two feet (0.6 m) from S's stern. At that diagram position, S had no assurance that P had heard her hails, or was preparing to change course, or even that P was aware of the presence of S. Also, P had sailed beyond the point at which she should have borne off, either to minimize the time and distance to reach the windward mark or to sail a course chosen for tactical reasons. For all these reasons, S was clearly unable to sail her course "with no need to take avoiding action" and so P broke rule 10. S was fully justified in expecting a collision and in concluding that only her action would prevent it.

There is no need to address the question of whether or not S broke rule 16.1 or 16.2 because, by the time S changed course, P had already broken rule 10, and S, acting as required by rule 14, changed course to avoid a collision. Even if the facts had indicated that S had broken rule 16.1 or 16.2, she would have been exonerated as provided in rule 64.1(a).

See also Case 50.

USA 1996/305
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