A proper sail is not a tablecloth, nor even a fitted sheet. The sails we fly are mathematically tuned airfoils that transform energy into movement smoothly and quietly. They’re not truly canvas (cotton is out of date) but thin synthetic fabric of surprising strength, designed and stitched to assume an ideal shape.
But the sun that powers the wind that powers us persistently degrades our sails. Ultraviolet (UV) light unlinks the complex chain molecules of synthetic fibers, weakens their bonds, and frays our stitching. Slowly this wear will lead to failure, but long before the sail fails catastrophically its airfoil shape is compromised.
In the previous “Canvas” feature in WB No. 281, we described some first aid for sail rips and seam failures. And while those are useful, we must be honest: there is a drawback. Whenever you reinforce or repair any part of a tension-structured airfoil, you will always concentrate stress on the “unlike” part you’ve created. An emergency repair meant to get you home must be addressed more deeply; it is a larger failure waiting to happen.
This is the basis for Canvas, Part 2, in which we refer you to the professional sailmakers and invite their expertise on the considerations every sailor must ponder.