Luffing in Sailing: When Can You Luff Another Boat?
A leeward boat can luff a windward boat because Rule 11 gives her right of way. But that does not mean she can turn whenever or wherever she likes. Rule 15 can apply when she gains right of way, Rule 16.1 limits how she changes course, and Rule 17 can limit how high she sails. Near a mark, Rule 18 may add another restriction.
The key to understanding luffing is working out which of those rules applies to the situation.
What sailors mean by "luffing someone up"
To luff is simply to turn towards the wind. On the water, sailors use the word in two slightly different ways:
- Luffing your sails. Heading up until the sails start to flap. This is boat handling, not a rules matter.
- Luffing another boat up. A leeward boat turns towards the wind and the windward boat has to turn up with her, or fall back, to stay clear.
The second is the one that can end up in the protest room. No rule in the Racing Rules of Sailing uses the word "luff" for it. There is no specific "luffing rule". Instead, several rules work together:
- Rule 11 gives the leeward boat right of way, which is why she can change course towards the wind.
- Rule 15 can apply when she acquires that right of way.
- Rule 16.1 limits how she changes course.
- Rule 17 may restrict how far up she can go.
- Rule 18 can impose additional obligations at a mark.
So when someone asks, "Can I luff him?", there are several questions to answer.
Why you may luff at all: Rule 11
Rule 11 states that when boats are on the same tack and overlapped, a windward boat shall keep clear of a leeward boat.
Nothing in Rule 11 freezes the leeward boat on her current heading. The windward boat's obligation to keep clear continues as the leeward boat changes course. If the leeward boat luffs, the windward boat must respond by turning up, or by falling back, if that is what is needed to keep clear.
Keep clear has a precise meaning in the rules. The windward boat is keeping clear only if the leeward boat can sail her course without taking avoiding action and, because the boats are overlapped, can also change course in either direction without immediately making contact.
A windward boat sitting so close alongside that the leeward boat cannot change course without immediately hitting her may already be failing to keep clear.
Having right of way is not the end of the analysis. Other rules can limit what a right-of-way boat may do. Rules 15, 16.1, 17 and 18 are important examples.
Rule 15: the moment you become the leeward boat
Rule 15 says that when a boat acquires right of way, she shall initially give the other boat room to keep clear, unless she acquires right of way because of the other boat's actions.
That distinction matters in luffing situations.
You created the overlap
If you come up from clear astern and establish an overlap to leeward, you acquire right of way through your own actions. Rule 15 applies, so you must initially give the windward boat room to keep clear before changing course.
The other boat created the overlap
If the other boat comes from clear astern and establishes an overlap to windward of you, your right of way arose because of her actions. Rule 15 therefore does not impose that initial obligation on you.
In both situations, Rule 16.1 still governs any luff that follows. Rule 15 concerns the moment right of way changes hands; Rule 16.1 concerns the course change itself.
Rule 16.1: room to respond
Rule 16.1 says that when a right-of-way boat changes course, she shall give the other boat room to keep clear.
This is often the rule that decides a luffing protest. The leeward boat can keep right of way throughout the manoeuvre, but she cannot simply turn as hard as she wants. If her course change leaves the windward boat without enough room to respond, the leeward boat may break Rule 16.1 even though Rule 11 was never broken.
Room is the space a boat needs in the existing conditions to comply with her obligations while manoeuvring promptly in a seamanlike way.
That means the answer depends on the circumstances. A large keelboat in rough water may need more time and space to respond than a dinghy in flat water.
The windward boat also has to respond properly. She is expected to react promptly and in a seamanlike way; she is not entitled to delay and then claim that the leeward boat luffed too quickly.
A useful practical question is:
Could the windward boat, responding promptly and competently, have kept clear?
If yes, the course change may satisfy Rule 16.1. If no, the leeward boat may have turned too quickly.
Rule 17: sailing above proper course
Rule 17 does not make luffing illegal. It prohibits one specific thing: sailing above your proper course when its conditions are met.
If a boat clear astern becomes overlapped within two of her hull lengths to leeward of a boat on the same tack, she shall not sail above her proper course while they remain on the same tack and overlapped within that distance, unless in doing so she promptly sails astern of the other boat.
Read carefully, that gives Rule 17 four conditions:
- You were clear astern and then became overlapped. If the overlap began any other way, Rule 17 does not apply.
- You became overlapped to leeward of the other boat.
- The overlap began within two of your hull lengths, measured using the hull length of the boat that became overlapped.
- The boats remain on the same tack and overlapped within that distance.
When Rule 17 applies, you may not sail above your proper course. You can still luff up to your proper course, but you cannot go above it simply to attack the other boat.
There is an exception in the rule: you may sail above your proper course if, by doing so, you promptly sail astern of the other boat. In that situation, heading up is part of getting clear rather than an attempt to attack the other boat.
What does "proper course" mean?
Proper course is defined as a course a boat would choose in order to sail the course as quickly as possible in the absence of the other boats referred to in the rule using the term.
That is a hypothetical test, not simply a geometric one. Proper course is not automatically the bearing of the next mark or a particular angle to it. The question is what this boat, in these conditions, would have chosen to do if the other boat were not there.
That has two practical consequences:
- Two boats can have different proper courses. Their boats, conditions or tactical circumstances may lead them to choose different courses.
- You cannot simply read proper course from a compass. In a protest, the committee has to decide what the boat would have chosen to do in the absence of the other boat.
The rules also state that a boat has no proper course before her starting signal. That is why Rule 17 does not impose its proper-course restriction before the start.
When Rule 17 does not apply
This is an important part of the rule.
Rule 17 does not apply when:
- The windward boat created the overlap. If she came from clear astern and established herself to windward, you were not the boat that came from astern.
- The overlap began more than two hull lengths away. Coming up from well below and then closing does not trigger Rule 17.
- The overlap began while you were ahead. If you were clear ahead and the other boat came alongside to windward, Rule 17 does not apply.
- The boats later separate beyond two hull lengths. Rule 17 applies only while they remain overlapped within the specified distance.
How far is too far? Head to wind
For a leeward boat not restricted by Rule 17, head to wind is the practical ceiling.
The moment you pass head to wind, you are tacking. Rule 13 then applies, requiring you to keep clear until you are back on a close-hauled course.
That changes the relationship between the boats. Before passing head to wind, you may have been the right-of-way boat under Rule 11. Once Rule 13 applies, you are the boat that must keep clear.
Luffing before the start
The pre-start is where luffing rights are widest, because the definition of proper course says that a boat has no proper course before her starting signal.
Rule 17 restricts a boat to her proper course when its conditions are met. Before the starting signal there is no proper course for Rule 17 to restrict her to, so Rule 17 does not impose that limitation.
A leeward boat can therefore luff a windward boat up to head to wind before the start, regardless of how the overlap was established.
The other rules still apply:
- Rule 16.1 governs the luff itself. If a boat luffs gradually enough for the windward boat to respond promptly and keep clear, the course change may be legal. If the luff is so sudden that the windward boat has no room to respond, Rule 16.1 can be broken.
- Rule 15 can apply when the overlap is created, subject to its exception.
- Rule 18 does not apply at a starting mark surrounded by navigable water during the approach to the start and until boats have left the mark astern, as specified by the rule.
After the starting signal, the definition of proper course becomes applicable, so Rule 17 can impose its restriction if all its other conditions are met.
See starting line rules for the rest of the pre-start sequence.
Luffing near a mark
At a mark, you have another question to answer: who is entitled to mark-room?
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, which is three hull lengths from the mark. There are exceptions, including certain situations involving boats on opposite tacks and boats approaching or leaving a mark.
Entitlement is determined when the first boat reaches the zone
This is one of the easiest parts of Rule 18 to get wrong. The important moment is when the first of the two boats reaches the zone.
Under Rule 18.2(a):
- If the boats are overlapped at that moment, the outside boat must give the inside boat mark-room.
- If the boats are not overlapped at that moment, the boat that has not reached the zone must give the other boat mark-room.
The boat required to give mark-room must continue to do so for as long as the rule applies, even if the overlap is later broken or a new overlap begins.
So what matters is the situation when the first boat reached the zone, not simply where the boats are later.
Mark-room is the room a boat needs to sail to the mark when her proper course is to sail close to it, and then to round or pass it on the required side and leave it astern.
A boat required to give mark-room can still change course, including luffing, provided she continues to give the other boat the mark-room she is entitled to. If the luff prevents the other boat from taking that mark-room, Rule 18.2 can be broken.
A few important qualifications
- The obligation can end early. Rule 18.2(a) no longer applies if the boat entitled to mark-room passes head to wind or leaves the zone, and Rule 18 as a whole can cease to apply between the boats once mark-room has been given.
- A late inside overlap can be an exception. If an inside overlap is obtained from clear astern or by tacking to windward, and the outside boat has been unable to give mark-room from the moment that overlap began, Rules 18.2(a) and 18.2(c) do not apply between them.
- Doubt about the timing of an overlap matters. Where there is reasonable doubt that an overlap was obtained or broken in time, the rules contain a presumption against the boat claiming that it was.
- Rule 17 can still apply. If the inside boat entitled to mark-room is also subject to Rule 17, she remains restricted from sailing above her proper course.
See room at the mark for a fuller explanation of Rule 18.
Do not forget Rule 14
Rule 14 runs alongside the other rules. A boat must, if reasonably possible, avoid contact with another boat and must not cause contact between boats.
A right-of-way boat has some protection under Rule 14: she does not have to act to avoid contact until it is clear that the other boat is not keeping clear or giving room.
But once it becomes clear that the other boat is not keeping clear, the right-of-way boat must act if it is reasonably possible to avoid contact.
So a leeward boat can comply with Rule 11 and still break Rule 14 if she could reasonably have avoided contact after it became clear that the windward boat was not keeping clear.
Right of way is not permission to cause avoidable contact.
Worked example: the downwind luffing match
Two boats are running towards the leeward mark, well outside the zone. Boat A closes from clear astern and establishes an overlap one hull length to leeward of Boat B.
- Rule 11 applies. B, the windward boat, must keep clear of A.
- Rule 15 applies when the overlap is established because A acquired right of way through her own actions. A must initially give B room to keep clear.
- Rule 17 applies because A came from clear astern and established the overlap within two of her hull lengths to leeward.
- Rule 16.1 applies whenever A changes course.
A may therefore luff up to her proper course, but not above it while Rule 17 continues to apply.
Suppose that, in the absence of B, A would have chosen to sail 15 degrees above dead downwind to sail the course as quickly as possible. That would be evidence of A's proper course, so she may sail that course even though it forces B to head up.
If A instead heads up to 40 degrees simply to push B out, she may break Rule 17 even though B remains obliged under Rule 11 to keep clear.
Change one fact
Suppose B had rolled over A from clear astern and settled to windward.
Rule 17 would not apply to A because A did not establish the overlap from clear astern. Rule 15 would not impose an initial obligation either, because A acquired right of way through B's actions.
A may therefore luff B up to head to wind, subject to Rule 16.1.
Change it again
Suppose both boats reach the zone still overlapped, with B inside when the first of them reaches the zone.
A owes B mark-room from that moment and must continue to give it while Rule 18.2 applies. A can still change course, but not in a way that prevents B from taking the mark-room she is entitled to.
Can I luff? A decision tree
Work through these questions in order.
1. Are the boats on the same tack and overlapped?
No: Rule 11 does not establish the windward/leeward relationship described here.
Yes: continue.
2. Am I the leeward boat?
Yes: Rule 11 gives me right of way and the windward boat must keep clear.
3. Did I just acquire right of way?
Check Rule 15. If I acquired it through my own actions, I must initially give the other boat room to keep clear. If I acquired it because of her actions, that initial obligation does not apply.
4. How did the overlap begin?
If I came from clear astern, became overlapped to leeward within two of my hull lengths, and the boats remain on the same tack and within that distance, Rule 17 restricts me to my proper course.
If the overlap began in another way, Rule 17 does not impose that restriction.
5. Am I giving the other boat enough room to respond?
Rule 16.1 applies whenever I change course. Could the windward boat, responding promptly and in a seamanlike way, keep clear?
6. Is anyone in the zone?
If Rule 18 applies, work out who was entitled to mark-room when the first boat reached the zone. Then ask whether my course change prevents her from taking that mark-room.
7. Am I approaching head to wind?
Head to wind is the limit before Rule 13 takes over. Once I pass head to wind, I must keep clear until I am back on a close-hauled course.
8. Is contact becoming likely?
Rule 14 applies too. Right of way does not give me permission to cause avoidable contact.
The two questions that often cause the most confusion are how the overlap began and whether the course change gave the other boat enough room to respond.
If you think a boat luffed you illegally
If you believe a boat broke a rule, follow the protest requirements in the Racing Rules of Sailing and in your event's notice of race and sailing instructions, including any applicable hail and flag requirements. Those requirements can vary with the rule alleged and the event, so check the applicable procedure rather than assuming the general case.
See how to protest for the procedure, and penalty turns for taking a penalty on the water if the luff was yours and it went too far.
For the underlying right-of-way rule, see the windward and leeward rule.
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Last updated: 2026-09-02