Protest Room logoProtest Room
RulesCasesAsk AI
Auth not available
  • Rules Explorer
  • Case Book
  • AI Judge
New protest
  1. Home/
  2. Rules/
  3. Rule 18

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

MARK-ROOM

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.

18.2: Giving Mark-Room

(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 the boats are not overlapped, the boat that has not reached the zone at that moment shall give the other boat mark-room. When a boat is required to give mark-room by this rule, she shall continue to do so for as long as this rule applies, even if later an overlap is broken or a new overlap begins. (b) Rule 18.2(a) no longer applies if the boat entitled to mark-room passes head to wind or leaves the zone. (c) When rule 18.2(a) does not apply and the boats are overlapped, the outside boat shall give the inside boat mark-room. (d) If a boat obtained an inside overlap from clear astern or by tacking to windward of the other boat and, from the time the overlap began, the outside boat has been unable to give mark-room, rules 18.2(a) and 18.2(c) do not apply between them. (e) If there is reasonable doubt that a boat obtained or broke an overlap in time, it shall be presumed that she did not.

18.3: Tacking in the Zone

If a boat passes head to wind from port to starboard tack in the zone of a mark to be left to port, rule 18.2 does not apply between her and another boat on starboard tack that is fetching the mark. If the other boat has been on starboard tack since entering the zone, the boat that passed head to wind

  • (a) shall not cause the other boat to sail above close-hauled to avoid contact, and
  • (b) shall give mark-room if the other boat becomes overlapped inside her.

18.4: Gybing in the Zone

When an inside overlapped right-of-way boat must gybe at a mark to sail her proper course, until she gybes she shall sail no farther from the mark than needed to sail that course. Rule 18.4 does not apply at a gate mark.

Definitions in Context

Clear Astern and Clear Ahead; Overlap

One boat is clear astern of another when her hull and equipment in normal position are behind a line abeam from the aftermost point of the other boat’s hull and equipment in normal position. The other boat is clear ahead. They overlap when neither is clear astern. However, they also overlap when a boat between them overlaps both. These terms always apply to boats on the same tack. They apply to boats on opposite tacks only when rule 18 applies between them or when both boats are sailing more than ninety degrees from the true wind.

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.

Rule 17

If a boat clear astern becomes overlapped within two of her hull lengths to leeward of a boat on the same tack, she shall not sail above her proper course while...

Rule 19

Rule 19 applies between two boats at an obstruction except when rule 18 applies between them and (a) the obstruction is the mark, or (b) the obstruction is anot...

© 2026 Protest Room. Open source and available under MIT License