RULE 18.1
When Rule 18 Applies

Rule 18.1 is a rule that states when rule 18 applies and then list some scenarios where Rule 18 expressly does not applies.

Prior to this, Section C also offers us some information where all of Section C does not apply and should therefore be read in conjunction with Rule 18.1. Here is what Section C says about all rules within it…

Section C rules do not apply at a starting mark surrounded by navigable water or at its anchor line from the time boats are approaching them to start until they have passed them.

Rule 18.1 then gets into specifics. It states:

18.1 When Rule 18 Applies

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

(a) between boats on opposite tacks on a beat to windward,

(b) between boats on opposite tacks when the proper course at the mark for one but not both of them is to tack,

(c) between a boat approaching a mark and one leaving it, or

(d) if the mark is a continuing obstruction, in which case rule 19 applies.

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

Let’s have a look at what that looks like in practice…

Scenario 1

Yellow and blue are moving towards the first mark which they both have to round on port.

At position 2, yellow is in the zone.

Does rule 18 apply?

Take a few seconds to look at the scenario again. Go through the elements about when rule 18 applies and where it does not.

YES, Rule 18 does apply

Assuming that both boats require to round the mark at the same side plus the fact that both boats are on the same tack and one of them is in the zone means that Rule 18 applies.
Scenario 2

Yellow and blue are moving towards the first mark which they both have to round on port.

Does rule 18 apply? Is there a change in your answer if you compare position 3 with position 4?

18.1 - example

Does rule 18 apply?

Take a few seconds to look at the scenario again. Go through the elements about when rule 18 applies and where it does not.

YES, Rule 18 applies

At position 3, both boats are in the zone but on diferent tacks so Rule 18 does not apply.

However, at position 4 and after yellow tacked, both boats are on the same tack and Rule 18 kicks in.

Scenario 3

Green and blue are sailing towards the finish line on a downwind leg. Green is on a starboard tack and blue is on a port tack.

18.1 - example

Does rule 18 apply?

Take a few seconds to look at the scenario again. Go through the elements about when rule 18 applies and where it does not.

YES, Rule 18 does apply

Both boats need to pass the mark on the same side and one of the boats is in the zone.

You may have said "no" because they are on opposite tacks but Rule 18.1(a) between boats on opposite tacks, on a beat to windward, only applies to windword marks. As none of the other exceptions under Rule 18.1 apply, Rule 18 applies...

Scenario 4

Green and blue are sailing towards the bottom mark on a downwind leg. Green is on a starboard tack and blue is on a port tack. The mark must e left to port…

18.1 - example

Does rule 18 apply?

Take a few seconds to look at the scenario again. Go through the elements about when rule 18 applies and where it does not.

NO, Rule 18 does not apply

Although both boats must round the mark on the same side and at least one of the boats in in the zone, Rule 18.1(d) states that if the mark is a continuing obstruction then Rule 19 applies.

Land is a continuing obstruction. Unlike "obstruction, "continuing obstruction" is not defined in the rules, so we must take the ordinary meaning of the word. That is "continuing" as in "permanent".

Scenario 5

Green and blue are sailing towards the start line. Blue is in the zone and yellow is overlapped. Both boats are on the same tack and close hauling towards the mark which they both have to leave on port.

18.1 - example

Does rule 18 apply?

Take a few seconds to look at the scenario again. Go through the elements about when rule 18 applies and where it does not.

NO, Rule 18 does not apply

Although Rule 18.1 seems to be satisfied and none of the exceptions under Rule 18.1 seem to apply, Section C tells us that Section C rules do not apply at a starting mark surrounded by navigable water. Rule 18 is part of Section C...
Scenario 6

Green and blue both need to round the mark leaving it at starboard before heading back up to the windward mark. The two boats are on opposite tacks. Green deployed her spinnaker whereas blue decided not to. 

18.1 - example

Does rule 18 apply?

Take a few seconds to look at the scenario again. Go through the elements about when rule 18 applies and where it does not.

YES, Rule 18 does apply

Blue is in the zone which means that Rule 18 applies because none of the exceptions apply.

The fact that green is a long way away does not matter. It stands to reason that green will approach the mark much faster whilst carrying more sail than blue so it pays for blue to be vigilant because Rule 18 kicked in as soon as blue entered the zone...

Scenario 7

Both boats are sailing as close to the wind as possible, They are on the same tack and blue entered the zone. Both boats need to round the mark in an anticlockwise direction leaving the mark to their port. There is a strong current flowing from right to left…

18.1 - example

Does rule 18 apply?

Take a few seconds to look at the scenario again. Go through the elements about when rule 18 applies and where it does not.

YES, Rule 18 does apply

BUT, Green will not be able to round the mark without tacking which means that she will be on opposite tacks soon at which point Rule 18 will no longer apply.

It is also possible that the blue boat will need to tack because of the strong currents which will have both boats eventually on the same port tack before both boats need to tack back to a starboard tack before rounding the mark.

Scenario 8

Green just rounded the mark and blue hails “MARK-ROOM!” because they feel they are entitled to it.

18.1 - example

Does rule 18 apply?

Take a few seconds to look at the scenario again. Go through the elements about when rule 18 applies and where it does not.

NO, Rule 18 does not apply

Rule 18.1(c) states that Rule 18 doesn't apply between a boat approaching a mark and one leaving it...

Blue didn't realise Rule 18 doesn't apply but in the end, she is on starboard and the green boat is on a port tack. This means green needs to keep clear of blue in any case under Rule 10.

So to sum up Rule 18.1

  • It determines if Rule 18 applies – nothing more.
  • It applies between boats when they are required to leave a mark on the same side, and
  • At least one boat must be in the zone.
  • It does not apply between boats on opposite tacks on a beat to windward, or

  • between boats on opposite tacks when the proper course at the mark for one but not both of them is to tack, or

  • between a boat approaching a mark and one leaving it, or

  • if the mark is a continuing obstruction, in which case rule 19 applies.

  • Also, Section C rules (including Rule 18) do not apply at a starting mark surrounded by navigable water.

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