An Effort to Improve Dacron

Despite the fabric engineers' best intentions, for example, after a while all those fillers and finishes added to woven sailcloth begin to break down, and what starts off as crisp, low-stretch fabric becomes a softer, more easily manipulated sailcloth that begins to stretch and distort the sail shape. Therefore alternative means of creating a tight weave were sought.

In the late '70s and early '80s Hood Sails believed it had solved the problem by producing its fabric in 24-inch-wide panels, rather than the 54-inch panels used by other fabric makers. With less distance upon which to exert pressure, it was reasoned, the beater would be able to create a tighter weave. There was probably some truth to this line of thought, and narrow-panel Hood sails were seen all over the world. In time, however, they were replaced by newer technologies, since among other things the added cost of sewing twice as many seams pushed the price up for very little commensurate gain.

Sailmakers also discovered that if the warp yarns were made much heavier than the fill yarns and then were pulled through the loom with a lot of tension the fill yarns would actually bend, leaving the warp yarns with much less crimp. This was especially helpful in terms of radial-panelled sails, i.e., sails made of panels radiating from the corners of the sail as opposed to the parallel panels in a cross-cut sail. Unfortunately, you could not have a fabric that was completely dominated by the warp to the exclusion of the fill since the result would be a lot of bias stretch. In order to increase the overall strength of the fabric, larger fill yarns had to be introduced, but they did not respond the same way as the light yarns since they were not as bendable, and the result was once again crimp back in the warp. There had to be a better way.

Fabric makers knew that small-denier yarns could be woven tighter than their larger-denier counterparts to create a more stable fabric since the thin fibers were more responsive to the pressure exerted by the beater, as well as the heat setting. But these lighter fabrics were not much use on larger boats, so fabric makers had to come up with a way of increasing the strength of the fabric without losing the positive attributes of small denier weaving. With this in mind they started to weave fabrics with both a light, tightly woven base and additional heavier yarns in the warp and fill direction. The light base provided great bias stability, while the heavier yarns added strength. This new fabric was called Square Weave by one manu-

These days you rarely see Dacron sails on the start line of an important race unless it's class mandated. At Block Island Race Week high-tech sails were the order of the day.

facturer. Fabric makers also discovered that they could introduce different kinds of fibers like Kevlar or Vectran into the weave thereby increasing the overall strength and stretch resistance of the fabric that much more.

Hood Sailmakers, for example, had great success including Vectran fibers in the fill of a number of styles of woven Dacron. Challenge Sailcloth did a similar thing including Kevlar yarns in the warp in a series of products they called Pinstripe. For example, the company made a 5.5-ounce Pinstripe fabric to be used for blade genoas on 30-foot boats, or No. 1 genoas on 40-foot boats. The base fabric was a tightly woven 150-denier Dacron with warp fibers consisting of five stripes per inch of 3,000-denier Kevlar. The base gave the fabric great bias stability while the Kevlar added 15,000 DPI (5 x 3,000) to the warp, making it very strong and low stretch for its weight. And there was another great side benefit. The light base provided high tear resistance. Despite the added work (read expense) of incorporating different threads, the results represented a tremendous leap forward.

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