Section C – At Marks and Obstructions
Rule 18.1, Mark-Room: When Rule 18 Applies
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(b),
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 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 under rule 14.
CASE 60
When a right-of-way boat changes course in such a way that a keep-clear boat,
despite having taken avoiding action promptly, cannot keep clear in a seamanlike
way, the right-of-way boat breaks rule 16.1.
CASE 76
When a boat changes course she may break rule 16, even if she is sailing her
proper course.
Rule 18.2(a), Mark-Room: Giving Mark-Room
CASE 2
If the first of two boats to reach the zone is clear astern when she reaches
it and if later the boats are overlapped when the other boat reaches the zone,
rule 18.2(a), and not rule 18.2(b), applies. Rule 18.2(a) applies only while
boats are overlapped and at least one of them is in the zone.
CASE 59
When a boat comes abreast of a mark but is outside the zone, and when her change
of course towards the mark results in a boat that is in the zone and that was
previously clear astern becoming overlapped inside her, rule 18.2(a) requires
her to give mark-room to that boat, whether or not her distance from the mark
was caused by giving mark-room to other boats overlapped inside her.
Rule 18.2(b), Mark-Room: Giving Mark-Room
Rule 18.2(c), Mark-Room: Giving Mark-Room
CASE 2
If the first of two boats to reach the zone is clear astern when she reaches
it and if later the boats are overlapped when the other boat reaches the zone,
rule 18.2(a), and not rule 18.2(b), applies. Rule 18.2(a) applies only while
boats are overlapped and at least one of them is in the zone.
CASE 12
In determining the right of an inside boat to mark-room under rule 18.2(b),
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
When an inside overlapped windward boat that is entitled to mark-room sails
below her proper course while at the mark, she must keep clear of the outside
leeward boat, and the outside boat may luff provided that she gives the inside
boat room to keep clear.
CASE 59
When a boat comes abreast of a mark but is outside the zone, and when her change
of course towards the mark results in a boat that is in the zone and that was
previously clear astern becoming overlapped inside her, rule 18.2(a) requires
her to give mark-room to that boat, whether or not her distance from the mark
was caused by giving mark-room to other boats overlapped inside her.
CASE 63
At a mark, when room is made available to a boat that is not entitled to it,
she may, at her own risk, take advantage of the room.
CASE 70
An inside overlapped windward boat that is entitled to and is receiving mark-
room from the outside boat must keep clear of the outside boat.
CASE 75
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.
CASE 81
When a boat entitled to mark-room under rule 18.2(b) passes head to wind, rule
18.2(b) ceases to apply and she must comply with the applicable rule of Section
A.
CASE 95
Rule 18.2(b) ceases to apply when either the boat entitled to mark-room or the
boat required to give it turns past head to wind. When a right-of-way boat is
compelled to touch a mark as a result of the other boat’s failure to keep
clear, she is exonerated from her breach of rule 31.
CASE 114
When a boat is entitled to room, the space she is entitled to includes space
for her to keep clear of or give room to other boats when required to do so
by the rules.
Rule 18.3, Mark-Room: Tacking When Approaching
a Mark
CASE 93
If a boat luffs immediately after she becomes overlapped to leeward of another
boat and there is no seamanlike action that would enable the other boat to keep
clear, the boat that luffed breaks rules 15 and 16.1. The other boat breaks
rule 11, but is exonerated under rule 64.1(c).
CASE 95
Rule 18.2(b) ceases to apply when either the boat entitled to mark-room or the
boat required to give it turns past head to wind. When a right-of-way boat is
compelled to touch a mark as a result of the other boat’s failure to keep
clear, she is exonerated from her breach of rule 31.
Rule 18.4, Mark-Room: Gybing
CASE 75
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.
Rule 18.5, Mark-Room: Exoneration
CASE 12
In determining the right of an inside boat to mark-room under rule 18.2(b),
it is irrelevant that boats are on widely differing courses, provided that an
overlap exists when the first of them reaches the zone.
CASE 63
At a mark, when room is made available to a boat that is not entitled to it,
she may, at her own risk, take advantage of the room.
CASE 70
An inside overlapped windward boat that is entitled to and is receiving mark-
room from the outside boat must keep clear of the outside boat.
CASE 93
If a boat luffs immediately after she becomes overlapped to leeward of another
boat and there is no seamanlike action that would enable the other boat to keep
clear, the boat that luffed breaks rules 15 and 16.1. The other boat breaks
rule 11, but is exonerated under rule 64.1(c).