Awalkspoiled said..
Duzzi - crazily enough the Dacron isn't heavy. Jeff isn't using the tarpaulin material early Windsurfer sails were made out of, but something lighter and less stretchy. My 10.0 Speedfreak - essentially an all-dacron sail - is FOUR POUNDS lighter than my 9.3 Point7 AC1. Some of that is extra battens and cams but a lot of it is the extremely light material. It's also extremely strong compared with monofilm. My 7.5 7-batten Speedfreak is a pound and a half lighter than a 7.5 Ezzy Zephyr and much more fun to use. I've foiled on both, which I could never do with that Point7.
They're harder to tune than other sails, because it's harder to visualize the twist when on the beach, but it's pretty easy to see on the water. Not everyone likes the spongy feel they offer, but I kinda do.
Comparing a recreational freeride sail, the six battens, single cam speedfreak, with a double luff, 4 cambers, eight battens, PWA level sail? Of course the Point-7 AC1 is heavier. It will also be 10 knots faster, and you can win a world championship with it. Pick the double cam Point-7 ACZ and guess what, it is 4 pounds lighter than the AC-1. Pick the no cams ACX and you drop another pound.
But you are right that the difference in weight btw Dacron, Xply and monofilm are not that much. Performance is a difference story, and of course fabric weight depends on the thickness of the material used by a sailmaker. My Superfreak UL were lighter than regular Superfreaks, they also disintegrated quickly.
Still don't understand what one thinks to achieve by putting dacron on the trailing edge of a sail. To me it makes no sense, but what do I know: I am curious to hear what the theory is!