Out of Whole Cloth: Sailcloth 101
Sails: When upgrading your sail inventory, understanding the basics of cloths, laminates and construction will keep the wool from being pulled over your eyes.
Laminated sails were first introduced in the early 1970s. The Australian 12-Meter Southern Cross tried using Kevlar fibers laminated to film and built as a crosscut sail before the 1974 America’s Cup. These early attempts at laminated sails proved to be unreliable—they were prone to break without notice—and were never used in competition. However, sailmakers realized the potential, and since then, building sails using several versions of laminated fabric has become the default fabrication method for racing and high-performance sails. The goal is a stretch-resistant, shape-holding, lighter sail that’s still affordable.
With laminate sails, there are many more components to the cloth, and sailmakers market their products under different names, which can be confusing. But reduced to the basics, the elements of laminated sailcloth are not unlike the components in the layup of a fiberglass boat; these include fibers, an adhesive, and a core.
Different sailmaking styles and cloths are evident in this trio of racing and cruising boats under way. Doyle’s Stratis pre-impregnated fiber technology is employed in the load-path sails on a Hanse 630 (left). An Oyster 485 (middle) makes tracks upwind under sails from North Sails that are built with the company’s new Radian warp-oriented Dacron sailcloth. Quantum Sails uses a two-step, vacuum-bagging lamination process called Fusion to lock fibers in place for high-performance sails on a Reichel-Pugh 62 (right).
Currently, there are eight different fibers used in sailmaking: carbon fiber, Spectra/Dyneema, Twaron, Technora, Kevlar, Vectran, polyester, and Pentax (which is basically “Dacron on steroids”). Only three of these—Dacron, Vectran, and Spectra—can be readily woven into a viable sail fabric. The remaining fibers are incorporated into a fabric in two basic ways; more on this in a moment.
Mylar film, the sheet form of polyester, is at the core of laminate sails. The film acts as a base to which everything else is glued to form the finished product. In addition, there is a specialized fabric called taffeta that’s used to provide chafe protection to the Mylar, as Mylar alone isn’t particularly durable and doesn’t respond well to chafe or sunlight. Taffeta, a woven polyester fabric consisting of small-diameter fibers, is glued onto the Mylar film—sometimes on one side, sometimes on both, depending on the sail’s intended use.
Finally, there’s a layer called the scrim. This is a combination of fibers—made entirely of Spectra, a Spectra/carbon blend, or consisting of other materials—driven by the sail’s intended use. The fibers in a scrim are assembled in combinations of angles in relation to each other and with different degrees of separations between the fibers. The scrim is designed to support the various secondary loads at work on a sail.
Historically, laminated sails of any construction method were usually replaced when the fibers delaminated from the film or the film itself broke down. Better glues and application methods, and the introduction of taffeta, largely addressed these two problems. Today, it’s virtually unheard of for a sail to fail because the fiber collapsed.
Two fundamental ways exist to make the laminate fabric. In one, the entire fabric is manufactured by a cloth company and arrives at the loft as a roll, known as roll goods. In building sails with roll goods, the laminated cloth is cut into panels that are then sewn together in one of three patterns: triradial, biradial, or crosscut. From the consumer’s perspective, panel configuration, for the most part, is a low priority, although there may be a small price difference among them. Your sailmaker can provide more information.