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Re: partiallyfurlled jib good or bad
All sails cut and assembled from FLAT sail fabric material are 'broadseamed' near and towards the luff portion of the sail. Broadseaming is the 'tapering' or narrowing of the 'width' of the panels by cutting away thin curved strips of panel material so that the sail can take on its accurately curved 3 dimensional shape. Broadseaming only occurs in the forward or first 30-40% of the sails cord length.
The resultant 3-dimensional shape (due to the panels being 'broadseamed') is what gives a sail its 'aerodynamic' ability.
If one rolls-up (furls/reefs) the first 30-40% of a sail's cord length, all the broadseamed section of luff to mid-cord panels are no longer 'available' to generate that 3 dimensional shape in the forward part of the sail.
Rx: rolling up beyond 30% of a sails cord length causes a sail to become the equivalent of bowed flat sheet of plywood.
The maximum one can roll up any sail and expect any reasonable shape is about 25-30%, 'maybe'-40%, maximum. Beyond that value the area where the point of MAXIMUM DRAFT is now inside the rolled up material; and, the sail no longer has exposed 'sail draft' other than a flat steady continuous curve - which can not be a 'decent' aerodynamic shape for other than being a 'parachute'!!!!!!!
Another way to look at this is: a 'Cruiser' who has his/her sails 'rolled up' beyond that 30%, and who cant start his/her engine while attempting to claw away ('point'/closehauled) while being 'blown' towards a lee shore will ultimately risk being called - 'beach debris'.
Last edited by RichH; 09-02-2015 at 11:59 AM.