(pillow)Case of the week (09/12) – 21

(This is an instalment in a series of blogposts about the ISAF Case book 2009-2012 with amendments for 2011. All cases are official interpretations by the ISAF committees on how the Racing Rules of Sailing should be used or interpreted. The cases are copied from the Casebook, only the comments are written by me.)

CASE 21

Definitions, Mark-Room
Definitions, Proper Course
Definitions, Room

The amount of space that a right-of-way boat obligated to give mark-room to an inside overlapped boat must give at the mark depends on the inside boat’s proper course in the existing conditions.

Question

When a right-of-way boat is obligated to give mark-room to an inside boat that overlaps her, what is the maximum amount of space that she must give? What is the minimum amount of space that she must give?

Answer

As the definition Mark-Room states, while the inside boat is at the mark the outside boat must give her room to sail her proper course. If the overlapped boats are on the same tack, mark-room includes room to tack. According to its definition, ‘room’ in this case is the space needed by an inside boat, which in the existing conditions is handled in a seamanlike way, to sail her proper course while at the mark.

The inside boat’s proper course is the course she would sail to finish as soon as possible in the absence of the outside boat. This may entitle the inside boat to more space than she needs for a seamanlike rounding. For example, her proper course may be a track that takes her farther from the mark as she rounds than a seamanlike rounding would so that her speed is not reduced by the tightness of her turn. Note that, according to the definition Mark-Room, an inside overlapped boat that is required to keep clear of the outside boat is not entitled to sail her proper course while sailing to the mark; she is only entitled to sail her proper course after she is at the mark.

The term ‘existing conditions’ deserves some consideration. For example, the inside one of two dinghies approaching a mark on a placid lake in light air will need relatively little space beyond that required for her hull and properly trimmed sails. At the other extreme, when two keel boats, on open water with steep seas, are approaching a mark that is being tossed about widely and unpredictably, the inside boat may need a full hull length of space or even more to ensure safety. The phrase ‘in a seamanlike way’ applies to both boats.

First, it addresses the outside boat, saying that she must provide enough space so that the inside boat need not make extraordinary or abnormal manoeuvres to sail her proper course while at the mark.
It also addresses the inside boat. She is not entitled to complain of insufficient space if she fails to execute with reasonable efficiency the handling of her helm, sheets and sails while sailing her proper course.

ISAF 1969/1

You might also want to read Q&A 2009-022 B005.

And from Rapid Response Match Racing Call 2010/001

Question 2
When does a boat sailing ‘to the mark’ become ‘at the mark’?

Answer 2
A boat that is sailing ‘to the mark’ will be ‘at the mark’ when one or more of the following conditions apply:

• (a) She is no longer able to alter course, in a seamanlike way, towards the mark and pass it on the wrong side.
• (b) Any part of her hull overlaps the mark and she is closer than half of her hull length to the mark.
• (c) She reaches a position where she would usually alter course to round or pass the mark on the required side in order to start sailing the next leg of the course.