10R Sail Measurement

[John949]

I am currently designing sails for my new 10R and I've come across (yet another) anomaly in the rules.  It concerns the measurement of the head area A2 and is most noticeable if the head of the sail falls either on, or just below, a cross-width measurement line.  The diagram below illustrates what can happen.

If the head of the sail falls on the measurement line, then A2 is zero and the equivalent measured area is the red area.  If the head of the sail falls just below the measurement line then then A2 is the red area PLUS the green area. Thus we have the ridiculous situation were; if the measurer thinks my sail luff is 1mm SHORTER than I do, then my measured sail area is BIGGER and my boat becomes illegal!

The irony is that this anomaly was introduced when the rules changed in 2016.  Prior to that the A2 was always equal to the red area.  

I can provide a detailed explanation of why and how this occurs if anybody else is interested.