Speed & Smarts: Another limit on Starboard tackers

One more angle on Rule 16 governing changes of course by right-of-way boats, by David Dellenbaugh.

TWO boats on opposite tacks (S and P) are approaching each other on a beat. As they get closer, P starts bearing off to pass astern of S. S also bears off and this turn causes P to bear away even further.

When S changed her course she gave P room to keep clear, and the boats never had contact. Is there any chance that S broke a rule?

The answer is Yes! and the rule is 16.2 (see box). This was added to the rule book about eight years ago in response to complaints that starboard-tack boats had too much power to “hunt” port-tackers. Its purpose was to place a further limit on how much the right-of-way boat can change course when boats converge on opposite tacks.

In recent issues we've discussed Rule 16.1, which says that when the right-of-way boat changes course she must give the other boat room to keep clear. Rule 16.1 applied to S in the situation above, and she did not break it because each time she changed her course she gave P room to keep clear
However, when boats converge on opposite tacks, the starboard-tacker must also comply with Rule 16.2, which is more restrictive. Here are three conditions that must all exist before Rule 16.2 applies:

1) It must be after the starting signal.
Rule 16.2 never goes into effect before the starting gun, so in the pre-start a starboard-tacker (S) can change her course aggressively to “hunt” a port-tacker (P). S must still comply with rules 16.1 and 14, but she doesn't tweak a rule if P has to change course immediately to keep clan This applies whether P is passing in front of or behind S.

2) The boats must be sailing on opposite tacks.
Rule 16.2 applies upwind or downwind when one boat on starboard tack meets a boat on port tack. It never applies to boats that are on the same tack.

3) The port-tacker must be passing astern of the starboard-tacker.
Here's the key point. In order for Rule 16.2 to turn on, the port-tacker (P) must be keeping clear by going behind the starboard-tacker (S). If P is trying to cross in front of S, 16.2 does not apply and S can “hunt” within the constraints of Rule 16. 1.

When all these conditions are met, 16.2 turns on and imposes an additional limitation on course changes by the starboard-tacker. It says that S is not permitted to change her course in a way that would require P to change her course immediately to keep clear.

The key in Rule 16.2 is the word “immediately.” If S changes her course and P is able to keep clear without turning right away, then S does not break Rule 16. But if S makes a turn so close to P that P has to react immediately, then S breaks Rule 16.2.

In the situation described at the beginning of this page, P bore off to pass behind S, S bore off toward P and P had to change her course a second time to keep clear. We know that S did not break Rule 16. 1, but how about 16.2?

Because this incident happened after the start and the boats were on opposite tacks and P was sailing to pass astern of S, 16.2 applied to any course changes by S. If P had to make her second change of course immediately after S bore off, then S broke Rule 16.2. If P did not have to bear away immediately, S did not break 16.2.

The question of whether P has to change her course “immediately” is a judgement call that is pretty much up to P. It depends on factors such as the speed and size of the boats, the degree of course change by the starboard-tacker, and the wind and wave conditions.

Since Rule 16.2 was written to protect the port-tacker, she will usually get the benefit of the doubt here. Therefore, when P is passing astern, any course change by S can be a risky move.

This article is extracted from Speed & Smarts, a newsletter published by David Dellenbaugh filled with how-to information for racing sailors.

Dellenbaugh, tactician aboard the 1992 America's Cup winner and an adviser to the German United Internet team for the 2007 AC, besides being a top sailor is a skilled communicator on tactics, rules and boathandling.

RULE 16 CHANGING COURSE

16.2 In addition, when after the starting signal a port-tack boat is keeping clear by sailing to pass astern of a starboard-tack boat, the starboard-tack boat shall not change course if as a result the port-tack boat would immediately need to change course to continue keeping clear.

However, since the boats are on opposite tacks and P is passing astern of S, Rule 16.2 also applies. It says that S must not change her course in a way that requires P to change her course immediately, to keep clear.

However, Rule 16.2 does not apply here because P is not sailing to pass astern” of S. Therefore, S has more freedom to “hunt” P (e.g. she could luff to prevent P from crossing ahead). As long as S gives P room to keep clear, it doesn't matter if P has to react immediately or not.

1. Rule 16.2 does not apply when …

a) It's before the starting signal; or
b) The boats are on the same tack; or
c) P is passing in front of S.

2.The “slam dunk” and Rule 16.2

One of the most common ways to break Rule 16.2 is by attempting a slam dunk when a port-tacker (P) is ducking behind you (Q. Remember that Rule 16 says when P is passing astern you can't change course in a way that requires P to change her course immediately to keep clear. However, when you luff up into a slam dunk tack, your transom often moves toward P as your bow moves away from her. This may cause P to bear off farther ð if she has to do this immediately, you break Rule 16.2.

3. Rule 16 applies downwind, too
Rule 16.2 applies whenever you have a port tack boat (P) passing astern of a starboard tack boat (S). This means it comes into play on runs as well as beats.

In the situation shown above, P is keeping clear of S by sailing to pass astern of her. Therefore 1) if S changes course she must give P room to keep clear; and 2) in addition, S must not change her course in a way that requires P to change her course immediately to keep clear.

Note that when boats have spinnakers set, “room” may involve a bit more time and space because of extra sail handling.

a) P crosses ahead of S on a run

Rule 16.2 does not apply to S because P is not passing astern of her.

b) P crosses behind S at a leeward mark

Rule 16.2 does not apply to S because she is about to round a mark. Rule 18 applies and 18.2(d) turns off Rule 16.

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