We decided last year to fully rely on ERS when measuring mainsails (see on website Proposal – Change of class rules regarding sail measurement procedure).
The point is that, from the very beginning of F18, for simplification purpose, and although we were measuring leech length from aft head point to clew point, we were used to compute basic surface relying only on the triangle made by tack point, head point & clew point, hence neglecting a thin triangle (head point, aft head point & clew point) of maximum 5,80m length x 0,05m height, equivalent to a maximum of 0,149 m² (see picture beside).
In order for measurers task to be consistent with World Sailing Measurement Procedures, and in order to prevent any dispute, we seized the opportunity of Class Rules update to raise maximum jib measured surfaces by 0.15 m², with no incidence on actual surfaces and hence no incidence on past nor future jib production, and to provide measurers with a new spreadsheet tool prepared by our Chief Measurer.
So maximum surface retained for small jibs is now 3.60 m², when maximum surface for large jibs is now 4.30 m².