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12

Sailing Vessels

Two sailing vessels in sight with risk of collision: A receives the wind on port, B on starboard, so A keeps out of B's way. Only projected courses are drawn. The overtaking rule remains an exception.

Rule 12 governs the interaction between two sailing vessels.

a
When two sailing vessels are approaching one another so as to involve risk of collision, one of them shall keep out of the way of the other as follows:
  • 1When each has the wind on a different side, the vessel which has the wind on the port side shall keep out of the way of the other
  • 2When both have the wind on the same side, the vessel which is windward shall keep out of the way of the vessel which is leeward
  • 3If a vessel with the wind on the port side sees a vessel to windward and cannot determine with certainty whether the other vessel has the wind on the port or on the starboard side, she shall keep out of the way of the other.
b
For this rule the windward side is opposite the side on which the mainsail is carried; for a square-rigged vessel it is opposite the side on which the largest fore-and-aft sail is carried.
Two sailing vessels in sight with risk of collision, both receiving wind on the same side: A is windward and keeps out of leeward B's way. The overtaking rule remains an exception; no avoiding turn is drawn.

IMO COLREG 1972Official text

Full wording of the rule, reproduced from the official source below.

(a) When two sailing vessels are approaching one another, so as to involve risk of collision, one of them shall keep out of the way of the other as follows: (i) when each has the wind on a different side, the vessel which has the wind on the port side shall keep out of the way of the other; (ii) when both have the wind on the same side, the vessel which is to windward shall keep out of the way of the vessel which is to leeward; (iii) if a vessel with the wind on the port side sees a vessel to windward and cannot determine with certainty whether the other vessel has the wind on the port or on the starboard side, she shall keep out of the way of the other. (b) For the purposes of this Rule the windward side shall be deemed to be the side opposite to that on which the mainsail is carried or, in the case of a square-rigged vessel, the side opposite to that on which the largest fore-and-aft sail is carried.
Source:

STCW Bridge Watch Lens

Rules 4–10 apply in any visibility.

Rules 11–18 apply to vessels in sight of one another; Rule 19 applies to vessels not in sight when navigating in or near an area of restricted visibility.

Build the traffic picture with sight, hearing, radar/ARPA and chart context.

Do not let AIS or one isolated bearing replace systematic observation.

After manoeuvring, keep monitoring bearing, range, CPA/TCPA and passing distance until the other vessel is finally past and clear.

Exam Focus

Identify the vessel types first, then the relative bearing, then whether one vessel is overtaking.

Misclassifying the encounter is the usual exam failure.

For vessels in sight, every overtaking vessel keeps clear until finally past and clear.

Rule 13 takes precedence over Part B Sections I and II; it does not override the other Parts of COLREG.

Key Takeaways

1

Port tack gives way to starboard tack

2

Windward vessel gives way to leeward when on same tack

3

On port tack, keep clear of a vessel to windward if you cannot determine her tack

4

Only applies between two sailing vessels

Common Mistakes

Applying these rules when one vessel is also being propelled by machinery

Confusing windward/leeward with port/starboard

Test Your Knowledge

Practise this topic and review the explanation for each answer.

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Frequently asked questions about COLREG Rule 12

Which sailing vessel keeps out of the way when two sailing vessels meet?

When each has the wind on a different side, the vessel which has the wind on the port side shall keep out of the way of the other (Rule 12(a)(i)). In short, port tack gives way to starboard tack.

What happens when two sailing vessels have the wind on the same side?

The vessel which is windward shall keep out of the way of the vessel which is leeward (Rule 12(a)(ii)). Windward gives way to leeward whenever both vessels are on the same tack.

What if a sailing vessel cannot tell which tack the other is on?

If a vessel with the wind on the port side sees a vessel to windward and cannot determine with certainty whether that vessel has the wind on the port or on the starboard side, she shall keep out of the way of the other (Rule 12(a)(iii)).