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.
Reliable, Affordable Dacron
Dacron sails are made from polyester fiber, which exhibits two primary sets of engineering properties: either high or low tenacity. The strengths of these fibers include their initial recovery from stretch; the break load for their size; resistance to chafe, exposure to ultraviolet light, and flex; reasonable cost; and minimal shrinkage when heated. High-tenacity fiber is superior for sails in every category, but it costs more, which is why there’s a wide discrepancy in price between low-tenacity Dacron and its high-quality counterpart.
Obviously, high-tenacity Dacron makes better cruising sails. The cost difference between a “value” cloth and a “premium” one, both from the same supplier, can be significant, close to 100 percent for some 8-ounce Dacron fabric that I’ve seen ($7 per yard versus nearly $15 per yard). Today, however, most sailcloth manufactured for the U.S. market is high-tenacity.
Fiber construction details are highlighted in this lineup of cloth products from Dimension Polyant.
Dacron that’s suitable for use in a crosscut sail is by far the most widely produced. Crosscut construction is easily the simplest way for a sailmaker to build any sail. It essentially involves stitching together horizontal panels of cloth that are stacked from the foot to the head.
Cloth for this style of construction is commonly called fill-oriented. The “fill” is the fiber that runs across the roll of cloth and, in the case of crosscut sails, is the thicker and less crimped direction. (Crimp refers to the S-curves caused by the weaving process.) When producing this cloth, the fill is pre-tensioned in the weaving process, and each strand of yarn is kept relatively short, since the width of a roll of cloth measures, at most, 6 feet. On the other hand, the warp—the thread that’s woven through the fill—might measure a couple of hundred feet in length.
Crosscut construction wastes very little cloth and is the fastest way to fabricate a sail; the seams between panels also offer many opportunities to design shape in the sail. The vast majority of modern boats use Dacron sails.
Recently, Challenge Sailcloth developed a Dacron product for use in radial-panel layout. North Sails also has its own version of Dacron, called Radian. In both materials, the warp, or long yarns, are or should be thicker than the fill.
Radial polyester fabric provides sailmakers with the opportunity to design and build triradial sails in woven material. Why is this important? The simple answer is that Dacron is the most durable fabric in absolute terms and that the radial-construction option can accommodate the higher loads placed upon larger or more performance-oriented sails. Sailmakers orient the sail’s panels to derive the shape of the sail and retain it over time. The radial corners are intended to minimize the so-called bias load—the 45-degree axis diagonally across the roll. The point to remember is that if you’re in the market for a sail, remember that the sailcloth in a triradial sail and the sailcloth in a crosscut sail are woven differently and aren’t interchangeable. Discuss the pros and cons of each with your sailmaker before placing an order.