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  3. Rule 18.1

Part 2 — When Boats Meet

Section C — At Marks And Obstructions

Section C rules do not apply between boats when the mark or obstruction referred to in those rules is a starting mark surrounded by navigable water or its anchor line, from the time the boats are approaching it to start until they have left it astern.

18.1

When Rule 18 Applies

(a) Rule 18 applies between boats when they are required to leave a mark on the same side and at least one of them is in the zone. However, it does not apply

  • (1) between boats on opposite tacks on a beat to windward,
  • (2) between boats on opposite tacks when the proper course at the mark for one but not both of them is to tack,
  • (3) between a boat approaching a mark and one leaving it, or
  • (4) if the mark is a continuing obstruction, in which case rule 19 applies.

(b) Rule 18 no longer applies between boats when mark-room has been given.

Definitions in Context

Continuing Obstruction

An obstruction is a continuing obstruction when the boat with the shortest hull referred to in the rule using the term will pass alongside it for at least three of her hull lengths. However, the following are not a continuing obstruction: a vessel under way, a boat racing, or a race committee vessel that is also a mark.

Mark

An object the sailing instructions require a boat to leave on a specified side, a race committee vessel surrounded by navigable water from which the starting or finishing line extends, and an object intentionally attached to the object or vessel. However, an anchor line is not part of the mark.

Mark-Room

Room for a boat

  • (a) to sail to the mark when her proper course is to sail close to it,
  • (b) to round or pass the mark on the required side, and
  • (c) to leave it astern.
Proper Course

A course a boat would choose in order to sail the course as quickly as possible in the absence of the other boats referred to in the rule using the term. A boat has no proper course before her starting signal.

Tack, Starboard or Port

A boat is on the tack, starboard or port, corresponding to her windward side.

Zone

The area around a mark within a distance of three hull lengths of the boat nearer to it. A boat is in the zone when any part of her hull is in the zone.

Related Cases

Case 9

When a starboard-tack boat chooses to sail past a windward mark, a port-tack boat must keep clear. There is no rule that requires a boat to sail a proper course.

Case 12

In determining the right of an inside boat to mark-room under rule 18.2(a)(1), it is irrelevant that boats are on widely differing courses, provided that an overlap exists when the first of them reaches the zone.

Case 15

In tacking to round a mark, a boat clear ahead must comply with rule 13; a boat clear astern is entitled to hold her course and thereby prevent the other from tacking.

Case 25

After an inside overlapped windward boat has been given mark-room, rule 18 no longer applies, but rule 11 continues to apply. The inside windward boat must keep clear of the outside leeward boat, and the leeward boat may luff provided that she gives the windward boat room to keep clear.

Case 26

A right-of-way boat need not act to avoid a collision until it is clear that the other boat is not keeping clear. However, if the right-of-way boat could then have avoided the collision and the collision resulted in damage, she must be penalized for breaking rule 14.

Rule 18.2

(a) When the first of two boats reaches the zone, (1) if the boats are overlapped, the outside boat at that moment shall give the inside boat mark-room ; (2) if...

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