Rule 42 Downwind Sailing Explained

We receive a lot of comments about our videos and Rule 42, specifically on the run. Sailors look at a piece of downwind footage and wonder aloud “Is that even LEGAL??”. Or maybe they’re doing the laser sailing downwind and hear a whistle behind them - they might feel mistreated based on their interpretation or misinterpretation of the rules vs. the jury's. They could be sailing on that fine line between legal and prohibited. Perhaps the jury's angle caused them to make a bad call. Or maybe, intentionally or not, they're just cheating. Look through the Rule 42 penalties at the Worlds this year and you’ll notice 14 downwind rocking related flags issued by jury members to top rated, world class sailors. It's the most common "rule breach" after the start.

So what’s legal and what’s not? Does anything lie in the “grey area”? What about subjectivity or pack behavior and it’s impact on 42 related rocking penalties? Do we need to push the limits of the rules to be competitive? Why do sailors with bad technique get flagged more often? These are all questions we'll try to address in this series on Downwind Rocking and Rule 42. You can view the sources for the Rules, Jury Interpretations and Common Breaches through the links at the bottom of the page. Note class rules could affect/trump Rule 42 but in Laser, none apply.

Let's start by examining Rule 42, its interpretations, and exceptions related to rocking/rolling to determine what's technically legal. The World Sailing interpretations are important because they are the lens juries use to view the rules through.

INTERPRETATIONS OF TERMS USED (shortened for clarity)

Roll - A single cycle where the mast goes to leeward and back to windward or vice versa

Rocking - Repeated rolling of the boat

Repeated - More than once on the same area on a leg


RULE 42.1 Basic Rule

Except when permitted in rule 42.3 or 45, a boat shall compete by using only the wind and water to increase, maintain or decrease her speed. Her crew may adjust the trim of sails and hull, and perform other acts of seamanship, but shall not otherwise move their bodies to propel the boat.


BASIC 2 A kinetic technique not listed in rule 42.2 that propels the boat, and is not one of the permitted actions covered in rule 42.1, is prohibited.

BASIC 4 Except when permitted under rule 42.3, any single action of the body that clearly propels the boat (in any direction) is prohibited.

The "clearly propels" phrase referred to here crucial. If the action in and of itself would propel the boat, then it is not legal. Note that this exception regarding rule 42.3 does not grant all rules under 42.3 (including rolling to facilitate steering) the permission to "use a single action of the body to propel the boat". It only allows for this in the 42.3 rules which specifically address this type of propulsion - clearing from a grounding, sailing instruction overrides, helping another in danger etc.

RULE 42.2 Prohibited Actions

Without limiting the application of rule 42.1, these actions are prohibited:

(b) rocking: repeated rolling of the boat, induced by

       (1) body movement,

       (2) repeated adjustment of the sails or centreboard,

   or (3) steering;

This specific section refers to rocking and it is clearly prohibited if initiated by a body movement, repeated adjustment of sails/blades or steering. Note that rocking is "defined" here as "repeated rolling of the boat". This is important, because it implies that a single roll of the boat induced by these actions is not prohibited in this rule so long as it does not "clearly propel" the boat. The interpretations below explain more.


ROCK 1 A roll of the boat caused by a gust or a lull followed by corrective body movement to restore proper trim is permitted by rule 42.1.

ROCK 2 One roll that does not clearly propel the boat is permitted.

ROCK 3 Background rolling is permitted. A boat is not required to stop this type of rolling.

ROCK 4 Adopting any static crew position or any static setting of the sails or centreboard, even when stability is reduced, is permitted by rule 42.1 and is not prohibited by rule 42.2(b).

ROCK 5 A single body movement that is immediately followed by repeated rolling of the boat is prohibited.

So given all that, we can maximize the natural tendency of the boats rocking if desired with our body position. In the right conditions, being more intentionally "reactive” to gusts and lulls is legal and potentially beneficial. We can also use one roll that is not propulsive in and of itself without issue.

That's the key - the judges will/should only flag if they are sure that the body movement is directly responsible for the speed increase.

If there's a beneficial natural rock happening due to swell/wave action, it's no problem to let it continue. We cover the details of these technical skills in depth in our Laser Sailing Downwind Clinic.

42.3 Exceptions

(a) A boat may be rolled to facilitate steering.

This is the big one as it relates to rocking. The interpretations below back this up but restrict us to a limited cadence if we do not have waves.

ROCK 6 Heeling to windward to facilitate bearing away and heeling to leeward to facilitate heading up are permitted. The heeling of the boat has to be consistent with the boat's turn. 

ROCK 7 Repeated rolling not linked to wave patterns is rocking prohibited by rule 42.2(b), even if the boat changes course with each roll.

This exception turns off the previous restrictions on rolling with the caveat that you must be facilitating steering and your roll must be linked to the wave pattern. You are absolutely PERMITTED to ROLL the boat to facilitate steering. If you need to bear away, you are clearly allowed to heel the boat to windward. If you need to head up, you may facilitate this by heeling the boat to leeward. However, note that ROCK 6 limits us to a heeling consistent with the turn.

 So we cannot initiate huge leeward heel and flatten with only a small course change (down the middle rocking), even with large waves.

Still, this exception is massive because it allows us to use the good technique that is completely natural to the boat and fast, as highlighted in this article on Tillerless Sailing - all while staying within the limits of the rules. This exception gives us more flexibility with rule 42 and provides another tool for the effective laser sailing downwind. Sailors are expressly permitted to roll the boat to facilitate steering, repeatedly, as long as it is linked to the wave pattern and does not clearly propel in and of itself, and so long as the roll is proportionate with the wave size.

This chart summarizes what's legal and what's not regarding Rule 42 and rolling downwind in a laser

This chart summarizes what's legal and what's not regarding Rule 42 and rolling laser sailing downwind.

 In our next article on Downwind Rocking and Rule 42, we'll discuss what juries are looking for, permitted actions that may get you flagged if viewed from certain angles, the grey area, pack mentality, the reality of prohibited actions at the top level, and more.



Rule 42

Rule 42 Interpretations[15083].pdf

Common Rule Breaches, Laser[16804].pdf

Dave Perry, Understanding the Racing Rules of Sailing 2017-2020

Dave Perry, Understanding the Racing Rules of Sailing 2017-2020

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