Appendices -- Useful Supplemental Information

BLACK IS BEST

Most sailors know sunlight kills polyester (Dacron, etc.) sailcloth. Sailors in low latitudes know it most keenly. Sailors in Maine, with a short season, and the sun often dimmed by fog, may not know it at all. Sailmakers know it because they get the sun-ruined sails to repair (or replace).

The effects of UV on synthetic sailcloth (it’s the UV component of sunlight that does the mischief) has been tested. The results are startling. In his 1990 book The Art and Science of Sails, Tom Whidden, then president of North Sails, reported that “Recent tests have shown that after three months in the Florida sun, the four common cloths used in mains and jibs -- Kevlar/Mylar, polyester/Mylar, Spectra/Mylar, and Dacron -- all show the same reduction in strength: About 40 percent.”

So what to do? What’s the best way to protect sails from UV?

Experience has shown that the best UV protection is an acrylic cloth like Sunbrella, in the darkest colors (acrylic fibers are pretty UV resistant, and the dark pigments make the cloth opaque -- light proof). The ubiquitous Pacific blue is pretty good, the navy blues are better. Browns are OK, but fade to pinkish browns. Dark greens are good. Reds fade quickly, and lose their protective qualities. Black is best. While offering the best protection, black covers will also last longer than light-colored ones. The sewing thread will perish in a few years, even in it’s black thread, but the restitched cover will be almost as good as new.

Mainsails need to be totally covered with a light-proof material. If the clew of the main sticks out, it will surely degrade. If sails are routinely left uncovered ready for the next daysail, the sun will degrade them. Tanbark and cream sails will show the effects of sun exposure by fading. Sails in ordinary nylon sailbags will also suffer -- and the bags will dissolve after a season or two.

For furling jibs, a common but imperfect remedy is a suncover of light polyester cloth coated with a white pigment. This suits many racing sailors, since the suncover doesn’t add much weight to the sail. Trouble is, this solution only extends the life of the sail under it by a year or two. Then the so-called “UV cover cloth” will be starting to come apart, and the sail under it will be badly weakened. A walk through any marina will reveal roller-furled jibs with pieces of the white cover drifting away. Standard acrylic cover cloth is pretty heavy (9 oz per sq yd) for roller-furling jibs, especially small ones, but Glen Raven Mills, which makes Sunbrella brand acrylic cover fabric, has introduced a light-weight version, currently available in a couple of useful dark colors.

When you try to convince a client of these facts, the reply is usually “But isn’t white better because it reflects the sun?” The answer is “No.” It reflects a some light, but a lot passes right through. The best practical test of a cloth’s usefulness as a UV shield is to hold samples up to the sun. Try it with a light-colored Sunbrella or sample of “UV coated Dacron,” then a sample of black Sunbrella. Any light you see through the cloth means some UV is getting through also -- visible and ultraviolet radiation are right next to each other in the spectrum. (When was the last time you saw a white automotive seat belt?)

Or a client might ask “Won’t the heat generated under a dark cover damage the sail?” “No” again. I’ve used black sailcovers on three boats, two of which lived in the tropics and semi-tropics, and one which stays in commission all year ’round on the Chesapeake -- with no evidence of damage from heat. The heat, in fact, just about guarantees there won’t be any mildew, because it keeps the sail so dry. If a mains’l arrives in my loft for repair, green with mildew along the boltropes and patches, I can surprise the owner by stating he has a white, or light-colored sailcover.

If your aesthetic sense baulks at black, or any dark color, go for white covers. But be prepared to reach into your pocket much sooner for a new suit of sails.