Sail structure

Abstract

Disclosed is a sail comprising a head, a tack, and a luff extending between the head and the tack; a luff region extending along the luff; wherein the luff region has a significantly higher degree of elasticity compared to the average elasticity of a remainder of the sail. Also disclosed is a method of making a sail comprising laying out material to form the sail; arranging material in a luff region of the sail and in the remainder of the sail such that in the direction of the luff, the luff region has a higher degree of elasticity compared to the remainder of the sail; curing or sewing the sail to form a cohesive structure.

The invention claimed is: 
     
         1 . A sail, being a mainsail or headsail, comprising
 a head,   a tack, and   a luff extending between the head and the tack, the luff comprising   i) a sail retainer to retain the mainsail to the mast, or to retain the headsail to the forestay, and   ii) a luff region, extending further aft in the sail from the sail retainer, and extending along the luff,   wherein the luff region has a higher degree of elasticity compared to a remainder of the sail and comprises a first material that has a lower stiffness in a direction parallel to the luff relative to a second material further aft in the sail than the luff region, and   wherein the luff region is configured to stretch as it is tensioned in a direction parallel to the luff.   
     
     
         2 . The sail of  claim 1 , wherein the sail retainer for the mainsail is selected from a portion of the edge of the sail luff that is adapted to attach to a track on the mast, or a portion of the luff adapted for attachment to mast clips. 
     
     
         3 . The sail of  claim 1 , wherein the headsail retainer is selected from clips or pockets on the luff of the headsail. 
     
     
         4 . The sail of  claim 1 , wherein the second material comprises an increased amount of material along a fringe of the first material and the second material. 
     
     
         5 . The sail of  claim 1 , wherein there is an absence of sail fibres, or sailcloth fibres, that extend in a direction parallel, or at least substantially parallel, to the luff in the luff region of the sail. 
     
     
         6 . The sail of  claim 1 , wherein there are sail fibres, or sailcloth fibres, in the luff region of the sail, the sail fibres, or sailcloth fibres, extending in a line that leaves an angle of greater or equal than about 15 degrees free from fibres relative to a direction parallel to the luff of the sail. 
     
     
         7 . The sail of  claim 1 , wherein the first material extends at least 50% to about 95% of a distance between the head and tack of the sail. 
     
     
         8 . The sail of  claim 1 , wherein the first material extends up to about 10% to about 50% of a width of the sail towards a leech of the sail. 
     
     
         9 . The sail of  claim 1 , wherein the first material extends towards a leech of the sail to a greater extent in a middle of the sail, relative to a height of the sail, compared to towards the head and tack of the sail. 
     
     
         10 . The sail of  claim 1 , wherein the sail further comprises a third region having an elasticity less than other regions of the sail, this third region extending along at least a portion of a margin of the luff region between the luff region and the remainder of the sail. 
     
     
         11 . The sail of  claim 9 , wherein the third region extends from the head to the tack of the sail. 
     
     
         12 . The sail of  claim 9 , wherein the third region comprises carbon. 
     
     
         13 . The sail of  claim 1 , wherein the first material comprises a gradient of reducing elasticity in a direction from the luff to a leech of the sail, as defined by its
 (i) failure strain, or   (ii) average Young's Modulus, or   (iii) both (i) and (ii).   
     
     
         14 . The sail of  claim 1 , wherein the first material comprises polyester. 
     
     
         15 . The sail of  claim 1 , wherein the difference in elasticity is achieved by a lesser material thickness in the luff region compared with the remainder of the sail. 
     
     
         16 . The sail of  claim 1 , wherein an orientation of a material in the luff region is different from an orientation of a material in the remainder of the sail, such that the luff region has a higher degree of elasticity compared to the remainder of the sail. 
     
     
         17 . The sail of  claim 1 , wherein the luff region does not comprise any carbon fibres oriented within 15 degrees of parallel to the luff, and wherein the remainder of the sail does comprise carbon fibres oriented within 15 degrees of parallel to the luff. 
     
     
         18 . The sail of  claim 1 ,
 wherein the sail is a twin skin mainsail having two skins defining the sail,   wherein each skin has a luff region extending along the luff, and   wherein each luff region has a higher degree of elasticity compared to a remainder of the respective skin.   
     
     
         19 . A method of making a sail, being a mainsail or headsail, comprising
 laying out material to form a luff, the luff comprising   i) a sail retainer to retain the mainsail to the mast, or to retain the headsail to the forestay, and   ii) a luff region, extending further aft in the sail from the sail retainer, and extending along the luff,   laying out material to form a remainder of the sail, and   arranging material in the luff region of the sail and in the remainder of the sail such that in a direction along the luff of the sail, the luff region has a higher degree of elasticity than a remainder of the sail and is configured to stretch as it is tensioned in the direction along the luff of the sail.