Rule 11
Application
Rules in this section apply to vessels in sight of one another.
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 purpose 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.
Overtaking
(a) Notwithstanding anything contained in the Rules of part B, sections I and II, any vessel overtaking any other shall keep out of the way of the vessel being overtaken.
(b) A vessel shall be deemed to be overtaking when coming up with another vessel from a direction more than 22.5 degrees abaft her beam, that is, in such a position with reference to the vessel she is overtaking, that at night she would be able to see only the sternlight of that vessel but neither of her sidelights.
(c) When a vessel is in any doubt as to whether she is overtaking another, she shall assume that this is the case and act accordingly.
(d) Any subsequent alteration of the bearing between the two vessels shall not make the overtaking vessel a crossing vessel within the meaning of these Rules or relieve her of the duty of keeping clear of the overtaken vessel until she is finally past and clear.