Mirror class rules for Nats & Europeans

  • T C Matthews
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06 Jul 2006 15:55 #19267 by T C Matthews
Mirror class rules for Nats & Europeans was created by T C Matthews
We are doing some minor modifications and repairs ahead of the Nationals & Europeans later this month but I do not wish to fall foul of the class rules. I have read them but would welcome some clarification if anyone can help:
a) on our fibreglass boat the deck fittings are often pulling out eg. spinnaker trimming lines. Is it legal to put additional hatches in the side bouyancy tanks so that there is access to the underside of the decks for better fixings?
b) At the last 'worlds'ther was a problem with the thickness of some foils - I gather that the latest suggested method of measuring the thickness of the foils is by using a precise "slot" template. This seems to be at variance with the rules which state a thickness of 14 mm but does not state that the sides of the foil have to be "parallel". The slot method of measuring seems sensible at first sight but actually would not test a foil that was 'bannana shaped' ie. not parallel lengthways. If the interpretation of the rules is that the foil should have sides which are parallel in the width direction, then why not in the length also? - in which case perhaps the "test slot" should perhaps be replaced with a "test envelope" template thereby checking uniformity of thickness in all directions?

This may seem petty but if the measurers are unhappy testing foil thickness with calipers (which can of course only give a 'spot reading') then the new theory for measuring needs to be carefully thought through.

All comments would be gratefully received.

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07 Jul 2006 13:58 #12396 by Martin Egan
Hi Tim,

a) Yes, rule 1.6.9 allows you to fit a hatch of not more than 170mm in diameter to the aft tank panel (already fitted to Trident GRP boats) and both side tank panels.

b) The use of templates for event measurement is in order to speed up the process by providing a go/no go check that is quick and easy to perform. I agree that a warped board (with, for example, a front edge to back edge bow) could be 14mm or less thick and fail to pass through a "slot" template. This being the case I'm intending to check boards that fail the template test with a pair of long reach callipers and if they are found to be 14mm or less thick then they will be passed OK.

It's probably worth pointing out that the chief measurer at the 2005 worlds reported some foils were up to 15mm thick in the centre (so warping wasn't the only reason foils failed) and that warped foils are less than ideal from a performance point of view.

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07 Jul 2006 15:22 #12397 by T C Matthews
Replied by T C Matthews on topic Mirror class rules for Nats & Europeans
Martin, Thats excatly what I needed to know. Many thanks.

Tim Matthews

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