August 2017 - The Luffing vs Mark-Room at a Leeward Mark

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August 2017 - The Luffing vs Mark-Room at a Leeward Mark

This month I will discuss two sets of actions – frequently seen when boats approach a leeward mark – and their consequences. In the diagram, Blue and Red are both sailing downwind on port. The diagram shows them with spinnakers, but the issues are the same in a whitesail race.

Red is sailing directly downwind; Blue is reaching a little more. The boats are overlapped and since Blue is leeward boat, Red must keep clear of Blue to comply with rule 11. We don’t know how the overlap was established, but if it was established by Blue from clear astern within two boatlengths of Red, rule 17 would then have applied. However, it doesn’t apply anymore, since at position 1, the boats are more than two boatlengths apart. Accordingly, since Rule 17 either never applied or no longer applies, Blue is allowed to sail above her proper course. They are not yet in the zone, so mark-room does not apply.


From here, two possibilities play out. Blue has the right to luff Red up, thereby taking her away from the zone. At position 5, the boats get close but Red does not respond, so by position 6, Blue is forced to alter course to leeward to avoid a collision. Red has broken rule 11 and Blue protests.


A second possibility – Red mobilizes one of two possible defences. The simplest is to get to the zone before Blue approaches. As soon as one of the boats touches the zone – which Red does just before position 7 – rule 18.2 starts to apply. Since Red is entitled to mark-room according to rule 18.2(b), Blue must now adjust her course to allow Red “to sail to the mark” (directly).


Many make a mark-room call far too early. If you know your speed, it isn’t too hard. One knot is about 1.7 feet per second. A 35-foot boat travelling at 5 knots takes a bit more than 4 seconds to travel 1 boatlength. So 12.5 seconds should elapse between an accurate call for room and the bow being level with the mark. If, on the other hand, it takes 30 seconds, your call came more than 7 boatlengths out – 4 boatlengths early. In the same 30-second interval, an Optimist travelling at 4 knots would have gone 25 boatlengths – a bit too generous.

Red’s second possible defence is to gybe onto starboard near position 2 – a simple option since she is sailing directly downwind. Once Red is on starboard, Blue – on port, remember – has to keep clear. Either way, Red is in the clear.


The things to remember are, if you are Blue, your luffing rights are powerful, but only if you meet the conditions that grant them. If you are Red, your defences are equally powerful, but only if you remain aware of what nearby boats are doing and act in good time.


Mark-Room Room for a boat to leave a mark on the required side. Also,


room to sail to the mark when her proper course is to sail close to it, and

room to round the mark as necessary to sail the course.


However, mark-room for a boat does not include room to tack unless she is overlapped inside and to windward of the boat required to give mark-room and she would be fetching the mark after her tack.


Room The space a boat needs in the existing conditions, including space to comply with her obligations under the rules of Part 2 and rule 31, while manoeuvring promptly in a seamanlike way.


Zone The area around a mark within a distance of three hull lengths of the boat nearer to it. A boat is in the zone when any part of her hull is in the zone.



When boats are on the same tack and overlapped, a windward boat shall keep clear of a leeward boat.



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. This rule does not apply if the overlap begins while the windward boat is required by rule 13 to keep clear.


18.2    Giving Mark-Room

When boats are overlapped the outside boat shall give the inside boat mark-room, unless rule 18.2(b) applies.

If boats are overlapped when the first of them reaches the zone, the outside boat at that moment shall thereafter give the inside boat mark-room. If a boat is clear ahead when she reaches the zone, the boat clear astern at that moment shall thereafter give her mark-room.

When a boat is required to give mark-room by rule 18.2(b),

she shall continue to do so even if later an overlap is broken or a new overlap begins;

if she becomes overlapped inside the boat entitled to mark-room, she shall also give that boat room to sail her proper course while they remain overlapped.


© Copyright 2017 Andrew Alberti

Posted: 4/29/2019 9:26:04 AM by Andrew Alberti | with 0 comments

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This page provides links to a set of articles original published in Kwasind magazine. The versions here include animated diagrams. The original articles can be found within the original magazines which are available online back to January 2007. 

Articles before December 2016 are based on the Racing Rules of Sailing 2009-12 or 2013-2016 and have not been updated to reflect the changes that apply as of January 2017 with the publication of the Racing Rules of Sailing 2017-20. A copy of the new rules can be found on
Andrew Alberti has been writing these monthly articles in the Kwasind since early 1997.  They explain the Racing Rules of Sailing. Andrew is a National Judge and National Umpire. He is a member of the Sail Canada Rules and Appeals Committees. The interpretation of the rules contained in the articles is Andrew's and not that of the RCYC or any of the committees he sits on. 

Send your questions to Andrew at


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November 2020 - Further down the line at the start
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