Dacron is a tough, long-lasting cloth that has only two real enemies—sunlight and chafe. There is not a lot you can do to ward off the effects of ultraviolet light except to make sure the mainsail cover is always in place when you’re not using the boat and to check that the sacrificial strip on the leech and foot of a roller genoa is in good condition.
Chafe is another matter. It likes to nibble at parts of the sail—stitching, reef patches, batten pockets, and the leech tabling. If you’ve had the sails valeted during the off season, the sailmaker should have passed an eagle eye over these vulnerable parts. If not, have a really close look at them yourself. This is best done with the sail spread out on the lawn. If the mainsail is still on the boat, drop it out of its luff groove or track, leaving the foot on the boom. Then you can pull the material over the boom as you inspect it. Look for broken or worn stitching and stretched stitch holes; these mean the seam is weak. You shouldn’t be able to see daylight through any seams.
It’s important to repair damaged stitching quickly, as even a few broken stitches can become a lot of broken stitches—and possibly a luff-to-leech tear—toward the end of a hard season. If your own needlework is of the ham-fisted variety, you could always plead with the local loft to repair the sail, but don’t count on them having time to do so at the start of the season, when most of them are run ragged.
The hardware also needs a close look. Sail slides can come under a lot of strain, especially at the headboard and tack, where loads are highest. Sailmakers recommend doubling up the slides in these areas. The top slide should be free to articulate, or the headboard will tend to jam on its way up the mast. Slides in general need to be checked regularly. UV light degrades the plastic, and this damage can be spotted easily enough—the plastic gets discolored. The webbing attaching the slides to the sail tends to wear and fray, but is easy enough to replace. Some slides are held on with shackles, and these have a tendency to go missing in the dead of night, so a good supply of spares should be kept on board. Many full-batten sails have expensive and complex devices for attaching the batten ends to the luff cars. If they fall apart they’re difficult to replace, so at least one of these should be added to the spares box.
Check the headboard for worn or corroded rivets and eyelets, and take a good look at the luff wire and the clew and tack rings. These are high-stress areas and, although they’re strongly built, they also suffer from general wear and tear.
Mainsails chafe much more than headsails because more parts of them come into contact with the rigging. The knifelike trailing edges of spreaders are prime culprits. These “aerodynamically efficient” spreader shapes were developed for racing boats and have since found their way onto all too many cruising boats, where they’re nothing but a nuisance. They don’t make one iota of difference to performance on a typical cruiser, but they do harm sails. You can offset the damage by putting spreader patches on the sail. On long voyages, where a fair amount of time is spent reaching or running with the main eased against the spreaders, it pays to tape split hosepipe or pipe lagging over the spreader edges.
The mainsail bears on the cap and/or aft lower shrouds much of the time, and while they fret merrily away at the sailcloth in general, they will rub through full-length-batten pockets in short order. Sticky-back Dacron patches will help in the short term, but a more permanent cure is to get a sailmaker to sew nylon webbing along the pockets. It always pays to keep a close eye on batten pockets because they lead pretty hard lives, especially on short-batten sails where there is a lot of flogging while reefing.