sail area rule changes

[mutt]

Having recently returned to the class, I was wondering if anyone can tell me how the rules regarding sail area have changed. I have sails dating from 2007 that are a little smaller than those measured in 2009
 
measurements are 1134, 1697,2041 and jib are 2.260m2 on the latter.
 
has the measured area of sail increased in rules since these sails were built?
 
thanks
Matt

[John m]

They are not smaller, but the rules around mainsail cross heights have changed.
 
Designers struggled to make sails to the maximum bottom height but could easily reach the maximum top and half heights.  If they did because the batten length is limited they suffered from the batten poking into the middle of the sail and causing a distortion.  There is a famous photo of N1 which shows just this problem!
 
A rule was put in place which moved some of the "unused" allowance from the bottom of the sale to the top, essentially pivotting around the middle height.
 
The outcome was that sails are a touch bigger overall as the area that was not being used now gets used.

[NTOACertification]

Hi Matt

Good to see you back in a Twelve.  As John has outlined the reasoning for the difference in sail size, the actual changes, which came into force in 2007, were...

the crosswidths calculated under Rule 11.3.6 have been changed such that the amount added in each width calculation has been changed as follows:  

On the 1/4 height the amount added has been reduced from 470mm to 395mm
On the 1/2 height the amount added has been increased from 565mm to 595mm
On the 3/4 height the amount added has been increased from 530mm to 580mm

Consequently the new sails are wider from the 1/2 height upwards, but possibly narrower from the 1.2 height downwards.  Assuming that a sail was measured at the time of manufacturer under the relevant rules it would be legal to use on the boat.  As long as the foot length is correct for both sail calculations, either of the sails could be used.

Will we see you at Burton Week at Pevensey Bay??

Kevan Bloor

[mattb]

Thanks John and Kevan,
that helps. To get an idea of the differences I'll overlay my sail with 3515 if G&A will let me.
I'd love to do Pevensey - I'm even available and have permission but I don't currently have a crew.
Matt
N3496,3486