November 2015 - Three Port-Tack Boats And One Starboard-Tack Boat

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November 2015 - Three Port-Tack Boats And One Starboard-Tack Boat

This month I am going to answer another question I received by email. This situation happened in two different Optimist regattas this summer. Each time, one of the boats involved was part of the RCYC team. 

In the diagram, three port-tack boats, Red, Yellow and Blue, are approaching one starboard-tack boat. The definitions say that an obstruction is “an object that a boat cannot pass without changing course substantially, if she were sailing directly towards it”. Green is big enough that Red, Yellow and Blue would have to change course substantially if they were sailing directly towards her. The definition also says that another racing boat is not an obstruction unless they are required to keep clear of her. Since Green is on starboard tack and the other three are on port tack, they are all required to keep clear of Green, so Green is an obstruction to Red, Yellow and Blue. 

Red has a choice. She can tack or she can bear away and duck Green. 

First, let’s look at her option to tack. Rule 20.1 says that when approaching an obstruction, a boat may with certain exclusions, hail for room to tack. However, Red would hit Green if she did not make a substantial course change, Red is sailing a close-hauled course and the obstruction is not a mark, so none of exclusions 20.1 a, b or c apply. 

If Red hails Yellow for room to tack, Yellow has to do something. Yellow really has nowhere to go except to tack herself. To do this, she needs to hail Blue for room to tack, and rule 20.3 allows Yellow to pass on the hail this way. Blue then has to do something which gives Yellow and Red room to tack. Blue’s most likely response is to tack; Yellow and Red, since they requested room to tack, must then do so. The important thing here is that Red must request room to tack in plenty of time. This must include time for Yellow to respond by hailing Blue for room to tack and then both Yellow and Blue must have time to tack. If Red hails too late, the others will not have time to respond and Red will be disqualified for not keeping clear of Green.

Red’s other choice is to bear away and duck Green, as shown in the second diagram. In this case we will look at rule 19. According to 19.2 (a), Red has the right to chose which side of Green to pass. If Red chooses to pass to leeward, then she is the outside boat and according to 19.2(b) must give the two inside overlapped boats, Yellow and Blue, room to pass between her and Green. 

It is important to note that just because Red choses to duck, Yellow and Blue are not forced to do so as well. They are allowed to, and if they do, Red has to give them room, but Yellow has the same choices that Red did and may elect either to duck or to hail Blue for room to tack. If she decides to hail for room to tack, she has to do so early enough for Blue to respond. If she decides to duck, then she has to give room for Blue to duck as well if Blue decides to do so.

On paper, all of this plays out quite well. In reality, with a lot of boats on the water, decisions have to be made quite quickly. If the Red boat ducks, she may not think about giving room to Yellow and Blue. Yellow may be more focused on the boat above but may not hail for room to tack in time. Lots of things can go wrong. Sailors who want to become more skilled sailors soon prioritize the ability to “sail ahead” of where they are, anticipating and allowing for situations like this, so they become events instead of problems, or simply never happen.

19.1 When Rule 19 Applies
Rule 19 applies between boats at an obstruction except when it is also a mark the boats are required to leave on the same side. However, at a continuing obstruction, rule 19 always applies and rule 18 does not.

19.2 Giving Room at an Obstruction
(a) A right-of-way boat may choose to pass an obstruction on either side.
(b) When boats are overlapped, the outside boat shall give the inside boat room between her and the obstruction, unless she has been unable to do so from the time the overlap began.
(c) While boats are passing a continuing obstruction, if a boat that was clear astern and required to keep clear becomes overlapped between the other boat and the obstruction and, at the moment the overlap begins, there is not room for her to pass between them, she is not entitled to room under rule 19.2(b). While the boats remain overlapped, she shall keep clear and rules 10 and 11 do not apply.


20.1 Hailing
When approaching an obstruction, a boat may hail for room to tack and avoid a boat on the same tack. However, she shall not hail if 
(a) she can avoid the obstruction safely without making a substantial course change,
(b) she is sailing below close-hauled, or
(c) the obstruction is a mark and a boat that is fetching it would be required to respond and change course.

20.2 Responding
(a) After a boat hails, she shall give the hailed boat time to respond.
(b) The hailed boat shall respond even if the hail breaks rule 20.1.
(c) The hailed boat shall respond either by tacking as soon as possible, or by immediately replying ‘You tack’ and then giving the hailing boat room to tack and avoid her.
(d) When the hailed boat responds, the hailing boat shall tack as soon as possible.
(e) From the time a boat hails until she has tacked and avoided the hailed boat, rule 18.2 does not apply between them.

20.3 Passing On a Hail to an Additional Boat 
When a boat has been hailed for room to tack and she intends to respond by tacking, she may hail another boat on the same tack for room to tack and avoid her. She may hail even if her hail does not meet the conditions of rule 20.1. Rule 20.2 applies between her and the boat she hails.

Obstruction An object that a boat could not pass without changing course substantially, if she were sailing directly towards it and one of her hull lengths from it. An object that can be safely passed on only one side and an area so designated by the sailing instructions are also obstructions. However, a boat racing is not an obstruction to other boats unless they are required to keep clear of her or, if rule 23 applies, avoid her. A vessel under way, including a boat racing, is never a continuing obstruction.

© Copyright 2015 Andrew Alberti
Posted: 11/1/2015 12:44:21 PM by Andrew Alberti

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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 2020 are based on the Racing Rules of Sailing 2009-12 or 2013-2016 or 2017-2020 and have not been updated to reflect the changes that apply as of January 2021 with the publication of the Racing Rules of Sailing 2021-24. 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 an International 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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