Monday, 18 June 2012

(pillow)Case of the week (25/12) - 08


(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.)

(pillow)Case picture

Case 8

Rule 42.1, Propulsion: Basic Rule
Rule 42.2(d), Propulsion: Prohibited Actions

While reaching at good speed, a boat does not break rule 42 when her helmsman, anticipating and taking advantage of waves generated by a passing vessel, makes helm movements timed to the passage of each wave. This is not sculling but using the natural action of the water on the hull.

Summary of the Facts

Two small dinghies, A and B, were reaching at about hull speed in an 8- knot wind. A large power cruiser passed by rapidly on a parallel course to leeward, creating several large waves. As each wave reached A’s quarter, her helmsman moved his tiller across the centreline in a series of course changes rhythmically timed to the passage of the waves under his boat.

This was done only during the encounter with the waves generated by the cruiser. B protested A under rule 42.2(d) for sculling. The protest committee disqualified A and she appealed.


A’s appeal is upheld. She is to be reinstated.
The action, while repeated, was not forceful. Any gain in speed did not result directly from the tiller movement, but from positioning the boat to take advantage of wave action, which is consistent with rule 42.1. To do so, a helmsman may move his tiller as he thinks best, provided that his movements do not break rule 42.2(d).

USSA 1962/91


If you have ever been on a Laser or Laser Radial course watching the boats in a beat when there are waves due to some wind, you will see this ‘rhythmic’ tiller movement all the time. It is the fastest way the hull moves trough the waves. Up the front and down the back. The helm moves his tiller to enforce this, but the tiller blade itself does not generate ‘energy’. His or her body moves as well to keep the boat flat, in the same rhythmic wave pattern.

The same movements would be considered illegal when there are no waves.


  1. Hugh Elliot - USA19 June 2012 at 12:25

    It would also be illegal if the wind had been a little stronger and A had pumped (but only once) to initiate surfing or planing on the wave - and had succeeded. Had she been protested for that Rule 42.3(c) would not have applied since she would have been attempting to plane or surf on the WINDWARD face of the wave.

    That is an interesting twist in the rule and, perhaps, ISAF will fix it one day.

    1. Yes, It will fixed in the next rulebook.


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