Happy New Year. Last summer I mentioned that I answer questions sent to kyrules@alberti.ca. I received two questions last year that wrestled with a similar problem. What happens when two boats sailing downwind have very different proper courses?
In the diagram, Blue is sailing directly downwind with a symmetrical spinnaker. Blue is being overtaken to leeward by Yellow, who is sailing with an asymmetrical spinnaker and as is typical for a boat with an asymmetrical spinnaker, she is sailing a higher downwind course than would be sailed by a boat with a symmetrical spinnaker or white sails. At position 1, Yellow is clear astern of Blue, so Yellow must keep clear of Blue. At position 2, Yellow has established an overlap to leeward from clear astern and within two boat-lengths. While Blue, as windward boat, must keep clear to comply with rule 11, Yellow is limited by rule 17 to sailing no higher than her proper course. Also, according to rule 15, Yellow – who has just acquired right of way – must initially give Blue time to keep clear. At position 3, we can see that Blue has started to keep clear.
I am frequently asked (in particular by the sailors of white sail or symmetric spinnaker boats) is, “Isn’t Yellow breaking rule 17? She doesn’t have 'luffing rights', yet she is luffing Blue. Blue is not being allowed to sail her proper course.” We have to look carefully at rule 17, which does not say that Blue can sail her proper course, nor does any other rule – it says that Yellow cannot sail above her proper course, and that is the course that she would sail to finish as soon as possible if the other boat (Blue) were not there. If we compare Yellow’s course at position 3 to the course sailed by Green, another asymmetric-sail boat, we see that Yellow may in fact be sailing below her proper course. This may be small comfort to Blue, who is not happy to be forced above her proper course, but Yellow is allowed to do this, as long as she doesn’t sail above her own proper course and as long as she gives Blue room to keep clear.
11 ON THE SAME TACK, OVERLAPPED
When boats are on the same tack and overlapped, a windward boat shall keep clear of a leeward boat.
15 ACQUIRING RIGHT OF WAY
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.
17 ON THE SAME TACK; PROPER COURSE
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.
Proper Course A course a boat would sail to finish as soon as possible in the absence of the other boats referred to in the rule using the term. A boat has no proper course before her starting signal.
© Copyright 2016 Andrew Alberti