The WSSRC Council announced a few months ago a new rule: the “50 cm minimum depth rule”. The Southampton University’s Wolfson Unit had done an investigation into the ramifications of “ground effect” on craft sailing in shallow waters.  On the final report of this investigation they 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”.

Well, now, the third paragraph of this rule has been amended like this:
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

This is really good news to all windsurfers and kiters. Along the 500 m length of the courses where the sailors did their attempts, sometimes the deph of the water varied considerably, and sometimes it would have been impossible to stick to the 50 cm rule to make their attempts official.  

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.

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