David Norton

Change in Rule 17, the Rule that Limits Luffing Rights
The purpose of Rule 17 is to limit the luffing rights of a boat that establishes a leeward overlap from clear astern while close to the boat ahead. The first sentence of new Rule 17 (which, in the old rules, was numbered 17.1) has been changed by the addition of the words "on the same tack" so that it now reads as follows (the added words are underlined): 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 change in Rule 17 was made necessary by a change in the definition Clear Astern and Clear Ahead; Overlap. In last year's rules, the terms clear astern, clear ahead, and overlap did not apply to boats on opposite tacks unless old Rule 18, Rounding and Passing Marks and Obstructions, applied. This year, as I have explained in recent columns, that old rule has been replaced by two new rules, Rule 18, which applies at virtually all marks and Rule 19, which applies mainly at obstructions that are not marks. Under the new rules, the terms clear astern, clear ahead and overlap now apply to two boats on opposite tacks when either of two conditions is satisfied-when (1) Rule 18 applies or (2) "both boats are sailing more than ninety degrees from the true wind." The second condition was added so that new Rule 19.2 will apply between boats passing an obstruction while they are running on opposite tacks, and so that boats on opposite tacks approaching a leeward mark while broad reaching or running would be overlapped before they reached the zone.

The added words in Rule 17 avoid two "game changes." A situation in which those changes would have occurred is shown in the diagram at right. On a run, Guy overhauls Winnie and establishes an overlap to leeward and within two hull lengths of her. At position 2, Rule 17 prohibits Guy from sailing above his proper course. Between positions 2 and 4, Guy jibes from starboard to port tack and then jibes back onto starboard.

Under old Rule 17.1, if Guy had jibed onto port tack when he did, he would no longer have been subject to Rule 17 because he would no longer have been overlapped with Winnie, and when he jibed back onto starboard, Rule 17.1 would not have applied because the new overlap would not have been established by Guy overtaking from clear astern. Because of the change in the definitions of clear ahead, clear astern, and overlap, without the new underlined words, Rule 17 would continue to apply to Guy after his first and after his second jibe. With the added words, Guy's first jibe switches off Rule 17. This is true because at position 3, he and Winnie, even though they are still overlapped and within two lengths of each other, are no longer on the same tack. Rule 17 is not switched on by Guy's second jibe because the conditions for switching on the rule are not met.

Also, without the new underlined words, Rule 17 would have imposed an illogical requirement on Guy at position 3. At that point the boats are on opposite tacks, but, without the words "on the same tack," Rule 17 would prohibit Guy from luffing above his proper course on port tack, even though such a luff would increase the separation between the boats.