Sail shape
It’s not that easy to see when a sail is “Blown out”, and lost its shape, unless you see it side by side with a good sail. I like to look at pictures of racing sails in action, to get an idea of what to look for. Televised America’s cup racing coverage usually has some overhead helicopter shots that really show nice sails in action.I have included two links to pictures that show elements of good sail shape. What you want to see is the deepest curve or point of maximum draft of the sail well forward of the midpoint. Around 35% aft of the luff for a heasdsail, and about 40-45% aft for a mainsail. The last 30% of the sail should be relatively flat.What happens as the sail gets old, is that the draft moves back towards the middle of the sail, 50% or more, and the curve of the sail takes a more rounded shape, like the edge of a circle. The draft gets deeper as well. The damage here is that the sail will have much more drag which causes more heeling combined with less forward drive. In other words, you tip sideways, and slow down. It's not just about speed, there is a comfort factor also.Most people are really surprised at how much better the boat stands up to the wind and moves forward with a fresh set of QUALITY sails. I know I was. I like maximum sized sails with a little flatter cut so they work in light wind and I still don’t have to reef as early.As to whether it’s worth the money, only you can decide. I don’t have any money, or I’d be ordering new sails right now!http://na.northsails.com/Cruising_Sails/SolutionsAddingDraftStripes.htmhttp://dan.pfeiffer.net/p26/150b.jpg