What Damages Boat Sails? 4 Main Factors To Know

Understanding why your sailcloth is becoming damaged is very important to keep it clean and healthy.

Polyester sailcloth consists of tightly woven threads, reinforced by resin (also called fill).

You will often hear it referred to as Dacron. Dacron is in fact a trademarked term for a particular kind of polyester thread, but many still use it generically.

4 Factors Damaging Your Polyester sails:

Ultraviolet light deteriorates most things. Chafe caused by the rigging weakens and tears the cloth. Fluttering breaks down the fibers and the resin fill in the cloth. Salt gets into the fibers of the cloth, growing mildew, as well as corroding the metal rings, grommets, and snaps.

Note: we are focusing on polyester here rather than laminates because that is the most common material for those who are not die-hard racers. Most of this advice applies to laminates, though, as well as nylons like your spinnaker.

1. Ultraviolet Radiation on Your Sails

The sun is always there, even on cloudy days.

You cannot stop the UV from hitting your sails. Eventually, your sails will get dyed from their crisp white to a shade of yellowish-gray. This indicates heavy UV exposure, which is almost always the cause of a sail’s destruction.

There are some polyester formulations that are more resistant to UV, but these are expensive, and degradation will still happen, anyway.

Eventually, the fibers will be so weakened by UV that the sails begin ripping easier and easier, either along the direction of the heavier threads (usually along the leech tabling), or where the stitch holes are along the seams.

UV Damage Prevention:

The best way to fight this is to keep your sails out of the sunlight every moment that you are not using them.

This seems obvious, but when I was a sailmaker, I saw customers come in every year with sails damaged by UV because they did not bother to put them away every time.

For instance, a friend with a Hobie Cat would leave his sails on the spars all weekend, and sometimes even for weeks in the summer, to avoid rigging them anew each day. You can tell some catamaran sailors would let them sit out longer, from the faded patches blotting the sails, indicating they had been bunched up and left exposed.

Even some of the distance cruisers would leave their sails uncovered when they reached a port or anchorage; after all, they had been sailing for a week, what harm would two more days of exposure do?

I could always tell this by the yellowish-gray triangles going up their leech, where they had left it folded on the boom uncovered.

All the excess exposure adds up and it cannot be undone. If you leave your sails on the spars, cover them with quality UV material, like Sunbrella. When your covers start to break down and tear (and they will – they are sacrificial in nature), get new ones.

If you are not going to be sailing for a month or so, take your sails (and covers) off.

Limiting the exposure is the only way to fight the inevitability of UV and get the most life out of your sails!

2. Chafe From the Mast and Rigging

Cloth rubbing against metal is not a good thing.

Either the continued chafe adds up and holes are finally worn through your sail, or the cloth snags and is torn.

There are two ways to prevent this, and you should do both:

Utilize Chafe Patches:

The first is to put chafe patches on the sails.

A chafe patch is simply an extra portion of sailcloth applied to areas that come into constant contact with the rigging, such as the spreaders or the stanchions. These patches take the chafe and wear instead of your actual sail.

When they show signs of getting worn out, replace them. We generally used polyester of the same cloth weight as the sail for spreader patches, and lighter adhesive polyester at areas like the foot where it would rub against the stanchions.

Treat Your Rigging:

The second is to treat your rigging.

Put boots on the ends of the spreaders, so the sail is chafing on rubber or leather rather than raw metal. Put covers or tape at the base of the shrouds, so the sail will not snag on rings or pins while tacking.

If you have a baby (or inner) stay, make sure the terminals are similarly wrapped up, as the genoa comes into contact with it on every tack.

Keep an eye out for rough areas on the fittings, such as a spinnaker pole eye, if you have one. Sometimes metal is not filed down as it should be.

One trick we used to do was to blow up a balloon and rub it all over the mast and the fittings, and along the shrouds.

If there was any metal flash that might damage a sail, you would be guaranteed to find it!

3. Flutter Along the Sail’s Edges and General Wear

As you tack or gybe, your sails will flutter. This causes tiny fractures in the fibers over time, and it does add up.

FLutter is much worse on laminates – I remember one guy who’d been supporting an America’s Cup campaign in the 90’s saying the leeches of the genoas began showing wear after a hundred tacks!

This manifested as delamination with tears along the stitch holes.

Maintain & Reduce Flutter:

One thing you can control here is leech flutter, once you are on your desired point of sail.

Tighten up the leech line (the small line running inside the leech fold) until it stops. Even if it hooks the leech to windward; that is more desirable than having to recut the leech because it has broken down from flutter.

I had one customer who brought a new boat back from the Caribbean, and the leech on his new roller-furling main was destroyed. He had been motor-sailing most of the time, as he had seen others do.

He had not been concerned about the constant flutter. A thousand miles later, his new brand sail needed serious surgery.

4. Salt Left on Your Sail

Salt gets in the fibers of the sail, even polyester with a high resin fill content which works on the fibers from within.

This is not as major a concern for the fibers as the other factors listed, but again, it adds up.

Salt in the sail is bad both for the cloth and all the metal, whether the corner rings, or grommets along the luff or foot, or fastenings on the luff of the jib.

It also causes mildew to form and spread. Once this happens, there is no remover that is completely safe for the cloth. You can use bleach, for example, but the fibers get damaged.

There are services that advertise removing mildew and putting resin back in the fibers, but the damage to the fibers has still been done, even if the cloth still feels new and stiffer.

Salt also corrodes the metal. Not the steel rings as much, but the brass and nickel of the grommets, and the bronze of the hanks. Every year we replaced all of these for customers who put their sails away with salt still coating them from the last sail of the season.

Washing Your Sails:

Fortunately, this is something you CAN control.

Wash your sails. From the first day that you use them flush them off with fresh water.

Let them dry, and then put them away. Do this, and you may never have to use any kind of detergent on them.

Make sure the salt is off the metal, too. It is a good idea to treat the metal with a preservative. WD-40 works but often stains your sails, so a marine version is best.

We usually used a spray silicone or dry Teflon lubricant.

I never liked any of the detergents we found, as they always softened up the resin fill in the sails as they cleaned them. This doesn’t necessarily damage the fibers, but it makes the sail softer and so it won’t hold the shape that was cut into it.

If you do need to clean the sail, a product we suggested was Arm & Hammer detergent, without any bleach. Use warm water to soak overnight, then flush it all off.

Final Thoughts

There are other things that might harm your sails – shoddy crew work, boarding actions, etc. – but now you know the worst offenders.

Your sails will eventually deteriorate, and nothing can prevent that, but you can take care of them and extend the life as long as possible. When you know what causes them to break down, you know how to address these factors.

Our cruising customers that took care of their new sails would get about 15 (often more) years out of the mains and genoas; those who did not would get 10 or (often much) less, and they were constantly being repaired.

Considering the investment that you have made in buying them, it makes sense to take the best care possible of your new sails!

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