The major differences are:

In the IRSA 65 Class rules

• The class rules are written in the WS SCR format using terms defined in the ERS.
• The sail measurement system is specified
• Ballast materials denser than lead are prohibited
• A draught limit is introduced
• Sail marks rules are rationalised with those in Appendix E of the RRS
• The rules for racing are specified as the RRS
• Changing the fin/ballast unit after each day’s racing is prohibited
• Measurement and certification of boats is by independent official measurers