Art - some good info in your post. The PHRF - OD sail rule depends on what PHRF body does the rating. Here on Narragansett Bay (PHRF-NB
), the PHRF rating is unchanged by sail cloth material, only by dimension changes in the sail. A few years back we posed the question to the rating body because of 0.5oz spinnakers. The rating body came back with the ruling they did not adjust ratings based on changes in sail materiel. I am aware of other rating bodies that work similarly, and some that will adjust the rating if the material does not meet OD requirements. My Vectron main has no PHRF rating adjustment. If I had a string sail, it would also rate the same.
You should read the minutes from the 5 August 2010 Board of Governors meeting
bullet #6 where Rod Johnstone commented on one reason why J/Boats
have used light weight laminate sails. Rod weighed in on the discussion and thought that the laminates were getting more cost competitive.