Rule 17: Proper Course After Overlapping to Leeward
Rule 17 of the Racing Rules of Sailing 2025-2028 limits a leeward boat that got her overlap from clear astern within two of her hull lengths. While the boats stay on the same tack and overlapped within that distance, she may not sail above her proper course. She has rights; she cannot luff you away from the mark.
Proper course is the course a boat would sail to finish as soon as possible if the other boat were not there. Overlap a boat to leeward from clear astern and you get right of way under rule 11, but rule 17 holds you to that course: you can sail for the mark, not head up to carry the windward boat away from it.
The limit lasts only while the boats are on the same tack and overlapped within two hull lengths. Open the gap past two lengths, or have either boat jibe, and it ends. The 2025-2028 rulebook dropped the old exception for an overlap that began while the windward boat was tacking: tack in front of a boat within two lengths and she is held to her proper course from the moment the overlap begins.
If the overlap began any other way, say the windward boat caught up and overlapped you, rule 17 does not bind you. You can luff, as long as you give her room to keep clear (rule 16).
Sail it
On the broad reach, a boat overlaps you to leeward from clear astern. Sail the windward boat and keep clear while rule 17 holds her to her proper course.
Questions
What is proper course in sailing?
The course a boat would sail to finish as soon as possible if the other boat were not there. It depends on the wind, the water and the next mark, so two boats side by side can have different proper courses.
Can a leeward boat sail above her proper course?
Only if rule 17 does not bind her. If she became overlapped to leeward from clear astern within two of her hull lengths, she cannot while that overlap lasts. Otherwise she can luff, giving the windward boat room to keep clear (rule 16.1).
When does rule 17 stop applying?
When the boats are no longer on the same tack, or no longer overlapped within two hull lengths of each other.
Paraphrased from rule 17 of the Racing Rules of Sailing 2025-2028, not quoted. The rule text is World Sailing's, and the rulebook is what a protest hearing reads.