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Question Why is the waterline length not required to be checked at certification control (measurement)?
Question Details

Why is the waterline length not required to be checked at certification control (measurement)?


Prior to the 1994 version of the class rules it was required to determine the waterline endings, measure the length between them and use that figure to determine the rating. The waterline endings were not marked with limit marks and no data was recorded that might determine those points. According to the certificate any alterations to the boat that affected the rating would invalidate the certificate.

However it was commonplace for owners to alter the fittings, mast position, spars, sails, on board rc equipment etc and not repeat the measurement process. Note that even a weight reduction would alter the rating thus rendering the certificate invalid.

In 1994 the requirement to add limit marks was introduced and it became permitted for the first time to alter the boat without the certificate becoming invalid. 

The purposes of this change:

  • to permit owners to freely modify their boats (which they did anyway) but for the first time within the class rules

  • with suitable equipment the measurer (certification measurer or equipment inspector at an event) can easily dry measure between the marks to establish the rated waterline length

  • with a tank, or any piece of calm water, the owner/measurer/sailor can float the boat and establish that the waterline endings are inside the limit marks without the need to precisely determine the waterline ending positions

  • there is the possibility that other sailors can judge whether a boat is floating to its marks or not

The new freedom granted to the owners was balanced by their new responsibility to ensure that their boat complies with the class rules and certificate when competing at an event. It follows that equipment inspection at an event (always difficult when flotation has to be checked) is the only way to monitor correct compliance with the class rules. But there is nothing new about this - it has always been so.

Should a boat be found to float with the waterline endings beyond the limit marks at an event the responsibility lies clearly and solely with the owner for failing to ensure it floats correctly. Altering the boat and failing to take steps to ensure continued compliance with the class rules might be taken as a breach of RRS 69 by a jury.

The 2016 CR have followed the same logic but have introduced some further safeguards. Boat weight is determined at certification control and is recorded on the certificate. At an event the boat may not weigh more than 0.05 kg more than this figure. The waterline limit marks shall be long enough to be visible when afloat.

Classes 10R