Section II: Conduct of vessels in sight of one another
Two sailing vessels: who gives way? Rule 12
In practice
- Different tacks: the vessel with the wind on the port side gives way.
- Same tack: the windward vessel gives way (the one "higher" into the wind).
- Cannot tell what tack the windward vessel is on? Then you give way (paragraph a.iii).
Top-down view, a schematic sketch. Red = gives way, green = stands on (keeps her course and speed).
Text of Rule 12: 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:
- (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.
Text of the International Regulations as amended, quoted from the consolidated U.S. Coast Guard Navigation Rules (public domain); spelling follows the IMO original. When in doubt, the Convention decides.
The common mistake
Applying Rule 12 to a boat under sail with her engine also running. In COLREG terms she is a power-driven vessel and follows the rules written for one. By day she should show a cone, apex down.
At night you know her by the lights
See in the trainer what a typical sailing vessel looks like at night: sidelights and a sternlight, no masthead light. She may add two all-round lights at the masthead, red over green, per Rule 25.