La règle 3 du réglement du WSSRC
Publié le lundi 1 septembre 2008
Alors que les riders les plus rapides de la planète s'apprêtent à en découdre à Luderitz très prochainement, après une étude sur l'effet de sol, le WSSRC a revu à la baisse la profondeur d'eau requise pour valider un record en milieu "naturel".
D'après l'étude, on constate que l'effet de sol prend effet dès que la profondeur est inférieure à la moitié de la largeur de la planche de kite, et étant donné que la largeur moyenne d'une planche de vitesse est de 20cm, la profondeur d'eau est ramenée à 10 cms.
Voici le texte en anglais du nouveau réglement :
The WSSR Council announces an amendment to WSSR Rule 3.3rd paragraph is amended as follows:
"For every record attempt on natural courses in every class, there must be a minimum depth of water, which is defined as follows.
At the time of the run in question, the shallowest part of the course must be covered by water with a depth of at least half the static immersed beam of the craft involved, or 10cm, whichever is the greater.
(Guidance note) To define the depth requirement, the craft or board involved should be afloat and the widest part of the hull or hulls touching the water should be measured. In the case of a multihull, the widest hull is measured or hydrofoil if fitted. In the case of an event involving a number of competing craft, the WSSRC Observer can announce at the commencement of the event what the minimum depth requirement will be"
Reason:
The WSSR Council had introduced the "50 cm minimum depth rule" after having commissioned an investigation from Southampton University's Wolfson Unit into the ramifications of "ground effect" on craft sailing in shallow water. This report had concluded that ground effect can indeed have a marked effect in reducing the drag of craft sailing in very shallow water, that it became significant at a depth factor of half the beam of a planing surface and that in general a minimum water depth of 50 cms would be more than deep enough to avoid this shallow water effect. In general, the sport had welcomed this ruling as it posed little or no practical problems.
Kitesurfers and Windsurfers however had a major difficulty in administering this new rule, to such an extent that it threatened to bring their attempts on records to a complete halt. These craft have traditionally used tidal courses, close to the shore since the 1980s, when the Weymouth Inshore course was established, Subsequent venues around the world - all verified by the WSSRC - had adopted this format of which the greatest advantage had been the ability to sail in smooth water. But by the physical nature of these courses and due to geographical and tidal effects, the depth of water varied considerably along the 500 metre length and thus complying with the 50cm rule overall could make it impossible to set courses, without ending up well out to sea, in conditions adverse to high speed.
All accept that "ground effect" exists and are unanimous that it should not be a factor in setting records. There was a danger that artificial courses might be created which could take advantage of this aid to higher speed but this was a separate issue which the WSSRC would address presently. However, in considering the Wolfson Report, the measurement at which ground effect came into effect was at half the beam of the board. As the average width of a board was 20 cms, it seemed reasonable to establish 10 cms as being the absolute minimum depth for natural courses - as opposed to manufactured courses - at the shallowest point.
John Reed
Secretary to the WSSR Council
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