Class Rules in Club Races.

Thanks for the considered reply.  I can understand the approach for the 'wholesome C/R' that IRC likes, in the 33ft and upwards range, but I would have thought that the J24 would suffer an awful hull factor so as to not make even attempting IRC worthwhile, let alone the trouble and expense of individual measurement:  I presume a class boat must be measured and weighted as for an 'endorsed' certificate to get a rating different from the class rating.

But Gordon proves me wrong:  J24 can win on IRC (or is that really a J4?)

Not sure if you are jesting or not but I'll give a serious answer. Once upon a time it was common for OD classes to race class-compliant with a single IRC rating e.g. the Sigma/33 and Sigma/38 fleets. That is now rare. The reason is that a boat can almost invariably get a more favourable rating but measuring individually. There are several reasons for that including:

1. they get more age allowance that way

2. it is normal for boats to weigh more than the designers figure on which the OD rating is based

The now-defunct Prima 38 class in the UK led the way regarding an OD fleet using individual certificates, the briefly successful and near-OD X332 class followed and the markedly differing IRC ratings gained by allegedly OD J/120s has been a subject of controversy in the USA. 

As for what J24s do in IRC, haven't a clue. It's nearly 20 years since I battered myself on those and that was in the now-defunct Solent OD fleet.

Agree, it seems a tricky issue. How do clubs implement the rules without alienating people.  Most rule bending breaking is probably a result of ignorance or economy but some experienced sailors knowingly do it for performance gain........I suppose it's a judgment call when dealing with it.