There’s usually a lot that can be done with halyard, sheet, outhaul and kicker to shape up a sad-looking mainsail, but if you find yourself underneath one that looks like a bag of flour after you’ve tried all you know, it’s time to consign it to the bin and brass up for a new one. Any sail with a hard camber and a leech that’s falling away despite the battens and your best efforts is, to put it bluntly, shot. There are a lot of them around…