Akite Sail Area

[Alan]

Is there a formula to roughly calculate the sail area of my asymetrical racing spinnaker? The IRC ratings are based on these numbers and I don't know how to compute it. I had been given a formula (SA= I x J x 1.7 x .85) but I have a masthead spinnaker on my fractional rigged boat so I don't think that the I is the standard I and the foot is very much larger than standard (J x 1.8).

 

[Bill Colombo]

IRC A-Spin Rule

SPA = ((SLU+SLE)/2)*((SF+(4*SHW))/5)*.83 Here is the whole rule…Spinnakers are on page 12.http://www.uncl.com/telechargement/IRC%202004%20UK.pdf