http://www.schrs.com/rules.php

B.1 Quality of boats

These rules are created mainly for production boats.
Non-productions catamarans, experimental boats and new types with provisional rating may be ranked apart.

B.1.1 Production boats
A production boat belongs to a registered class or to a registered type.
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B.1.2 Non-production or experimental boats
A non-production boat is any boat which does not belong to a registered class or to a registered type. A boat built as a registered boat but which is modified in such way that she contravenes her class rules will be considered as a non-production boat.
B.2 Rating certificate

To be permitted to race, a boat shall provide a rating certificate issued by the ISAF or a National Authority.
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D. MEASUREMENT
All measurements must be undertaken according to the ISAF measurement rules and instructions.

For "Formula" type classes such as Formula 16, Formula 18, Formula 20 and A-Class, the rating is to reflect the limiting values for all relevant measurements permitted by the class rules. Where a measurement is required by SCHRS but not governed by class rules it is necessary to carry out measurement as required for an SCHRS rating.


When I read that I think it is the same F18 rating for F18 Tiger or F18 Phantom. May be I'm wrong.