Section A - Definitions and Fundamentals
TR CALL A1
Rule 13, While Tacking
Rule 17, On the Same Tack; Proper Course
Question
On a beat to windward, an overlap is established while one boat is tacking or shortly thereafter. Under which of the following conditions is B, the leeward boat, permitted to sail above her proper course?
Answer
Figure 1:
Overlap established from clear astern - B does not acquire luffing rights. Y completes her tack at position 3, when she is clear ahead of B. Shortly thereafter B establishes an overlap from clear astern and will break rule 17 if she sails above her proper course during this overlap, and while the boats remain within two hull lengths of each other, unless in doing so she promptly sails astern of Y.
Figure 2:
Overlap established from clear astern - B acquires luffing rights. The moment Y passes head to wind in position 2 the boats are on the same tack, but not overlapped. The overlap is established before Y reaches a closehauled course - i.e. while Y is subject to rule 13. Therefore rule 17 does not apply and B may sail above her proper course.
Figure 3: Overlap established 'instantaneously'. At position 2, when B passes through head to wind, both boats are on the same tack and overlapped. As neither boat established this overlap from clear astern, the overlap is said to be 'instantaneous'. Rule 17 does not apply and B may sail above her proper course.
A tacking boat changes tack the moment she passes head to wind. However, she is keep-clear boat subject to rule 13 from the moment she passes head to wind until she is on a close-hauled course. If another boat becomes overlapped to leeward of her from clear astern during that period, rule 17 does not apply and the leeward boat may sail above her proper course - i.e. she has 'luffing rights'.