INTERPRETATIONS OF RULE 42, PROPULSION

INTERPRETATIONS OF TERMS USED IN RULE 42

A term used as stated below is shown in italic type. Other terms that are specific to rule 42 are defined in the rule.
Background rolling is the minimum degree of rolling caused by the waves.
Body pumping is the movement of a sail caused by in and out or up and down body movement.
Fanning is trimming and releasing a sail not in response to changes of wind speed or direction.
A flick is the effect of trimming a sail so abruptly that the normal shape of the sail is changed and almost immediately returned to the original shape.
A pump is a fast and sudden movement when pulling the sail. (However, 'pumping' may be fast or slow.)
Repeated is more than once in the same area on a leg.
A roll is a single-cycle athwartships movement of the mast going to leeward and back to windward.
Torquing is the fore and aft or rotating movement of the body.
A trim (of a sail) is generally a slow pulling of a sail.
Yellow light area is a phrase used when it is not clear that an action is prohibited. It is unlikely that a boat in the yellow light area would be protested, but it is possible. If the action is repeated, the likelihood of a protest will rapidly increase.

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.
INTERPRETATIONS
42­01	An action which is not listed in rule 42.2 may be prohibited under rule 42.1.
42­02	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.
42­03	An action prohibited in rule 42.2 cannot be considered as permitted under rule 42.1.
42­04	Any single action of the body that propels the boat (in any direction) with the effect of one stroke of a paddle is prohibited.
42.2 Prohibited Actions
	Without limiting the application of rule 42.1, these actions are prohibited: (a) pumping: repeated fanning of any sail either by trimming and releasing the sail or by vertical or athwartships body movement;
INTERPRETATIONS
42­05	'Trimming and releasing' connected with wind shifts or gusts is permitted, even if repeated, provided the action does not repeatedly fan the sail.
42­06	Except when permitted under rule 42.3(b), one pump may be prohibited under rule 42.1.
42­07	More than one pump is prohibited under rule 42.2(a).
42­08	A flick of a sail is clear evidence that the sail has been pumped, although a sail can be pumped without a flick.
42­09	A flick of a sail resulting from the sudden stopping of an eased sheet is permitted.
42­10	One flick of a sail due to body pumping or a pump not permitted by rule 42.3(b) is in the yellow light area.
42­11	Repeated flicks of a sail due to body pumping are prohibited.
42.2 Prohibited Actions
	Without limiting the application of rule 42.1, these actions are prohibited: (b) rocking: repeated rolling of the boat, induced either by body movement or adjustment of the sails or centreboard, that does not facilitate steering;
INTERPRETATIONS
42­12	A roll of the boat caused by a gust or a lull followed by corrective body movement to restore proper trim is permitted.
42­13	One roll that does not have the effect of a stroke of a paddle is permitted.
42­14	Background rolling with no body movement or adjustment of a sail is permitted. A boat is not required to stop this type of rolling.
42­15	An unnecessary position of any crew member that could cause or increase repeated rolling is prohibited, except briefly to perform a necessary task.
42­16	Maintaining an unnecessary position that increases repeated rolling is prohibited under rule 42.1.
42­17	A trim of a sail that induces repeated rolling of the boat is prohibited.
42­18	A boat rolling clearly in excess of the background rolling, with no body movement or pulling of the sail, is in the yellow light area.
42.2 Prohibited Actions
	Without limiting the application of rule 42.1, these actions are prohibited: (c) ooching: sudden forward body movement, stopped abruptly;
INTERPRETATIONS
42­19	Torquing to change the fore and aft trim of the boat in phase with the waves is permitted, provided it does not result in pumping the sails, especially flicking the leech.
42­20	Torquing that results in the sudden stop of any part of the body is prohibited.
42­21	Torquing on flat water is prohibited.
42.2 Prohibited Actions
	Without limiting the application of rule 42.1, these actions are prohibited: (d) sculling: repeated movement of the helm not necessary for steering;
INTERPRETATIONS
42­22	Sculling is allowed only when 'necessary for steering'. This means that no other means of steering is available at the time and such steering results in a clear change of direction.
42­23	Any further connected sculling to offset the first sculling action is prohibited.
42­24	Any sculling (two or more similar movements of the rudder, however small) that does not result in a clear change of direction is prohibited.
42­25	Repeated movement of the helm to offset steering of the boat caused by trimming, such as backing a sail, is prohibited.
42­26	Any sculling continuing once the sail can be filled is prohibited.
42.2 Prohibited Actions
	Without limiting the application of rule 42.1, these actions are prohibited: (e) repeated tacks or gybes unrelated to changes in the wind or to tactical considerations.
42.3 Exceptions
	(a) A boat's crew may move their bodies to exaggerate the rolling that facilitates steering the boat through a tack or a gybe, provided that, just after the tack or gybe is completed, the boat's speed is not greater than it would have been in the absence of the tack or gybe.
INTERPRETATIONS
42­27	Exaggerated body movements that cause a boat to sail out of a tack or a gybe at the same speed as she had just before the manoeuvre are permitted.
42­28	Violent movement propelling the boat like a stroke of a paddle is prohibited under rule 42.1.
42­29	When the speed of a boat clearly drops after accelerating out of a tack or a gybe, and there is no obvious change of wind speed or direction, the boat is in the yellow light area.
42­30	It is permitted to move the mast over the vertical at the completion of a tack or a gybe.
42.3 Exceptions
	(b) Except on a beat to windward, when surfing (rapidly accelerating down the leeward side of a wave) or planing is possible, the boat's crew may pull the sheet and the guy controlling any sail in order to initiate surfing or planing, but only once for each wave or gust of wind.
INTERPRETATIONS
42­31	One pump made to attempt to surf or plane when surfing or planing conditions are marginal is permitted even if the attempt is not successful.
42­32	If a boat repeats an unsuccessful attempt to plane or surf while on the same leg, she is in the yellow light area.
42­33	Each sail may be pumped at different times, but only as permitted by rule 42.3(b).
42­34	It is only necessary for surfing or planing conditions to exist at the position of a boat for her to be permitted to make one pump.
42­35	Surfing or planing may be possible for some boats but not for others. This can be caused, for example, by local gusts or by waves from a motor boat.
42.3 Exceptions
	(c) Any means of propulsion may be used to help a person or another vessel in danger. (d) To get clear after grounding or colliding with another boat or object, a boat may use force applied by the crew of either boat and any equipment other than a propulsion engine.

Approved by David Tillett, Chairman, ISAF Racing Rules Committee, in accordance with
ISAF Regulation 31.4.
14 April 2003