A Lexicon of Today's Fibers
Neil Pryde proudly uses the best in woven and laminated sailcloth in the world. We purchase from the suppliers listed below and the fabrics of which each excel.
A customer looking to purchase a new sail for racing or cruising these days is met with a staggering number of choices in different sailcloth laminates, woven goods, and recently in fibers as well. To a large extent, the customer must rely upon the advice of his Neil Pryde Agent to select the appropriate materials best suited to our designs and constructions as well as the customers sailing requirements. In racing applications, the ongoing development of new fibers and constructions can make this particularly confusing for the lay person and professional alike. The following lexicon will help identify and clarify some of the different and new fibers in the market today.
Polyester: The most common fiber used for both woven sailcloth and laminates. Its properties include good UV and flex resistance, as well as being inexpensive. A proven fiber for durability, polyester has been replaced by higher modulus (less stretch) fibers for most racing applications.
Kevlar: A gold colored aramid made by DuPont, Kevlar's modulus is five times greater than polyester so it stretches less and sails made from it can be lighter. Of all the high modulus fibers, Kevlar has the most proven track record. It is available in both standard K-29, and high modulus K-49 fibers, with the latter being used more and more for high-end racing applications. Although much stronger than polyester, Kevlar is not as durable in terms of fatigue and UV resistance. It is also more expensive.
Twaron: Made by the German company Akzo, Twaron is aramid product very similar to Kevlar.
Technora: Made by the Japanese company Teijin, Technora is an aramid developed as a reinforcement for drive belt applications. In sailcloth, it is dyed black to help its UV resistance. Technora has a modulus similar to Kevlar, slightly better abrasion resistance and is more expensive than Kevlar.
Spectra: A high molecular weight polyethylene, Spectra is a product of the Allied-Signal Corporation. Spectra has the highest modulus of any fiber, except carbon, used in sailcloth but has seen limited application in racing sails because of its creep property, meaning that the fiber will permanently stretch when placed under high constant load. This stretch makes it difficult for sail designer to lock in the shapes they want. As a result, Spectra is viewed more as a performance cruising fiber where its excellent flex, UV and abrasion properties along with its traditional white color are perfect for large cruising boats where cloth strength and durability as well as weight aloft are considerations. Spectra is more expensive than Kevlar.
Certran: A high modulus polyethylene fiber, similar to Spectra, manufactured by Hoechst Celanese. This fiber share the same resistance to flex fatigue and UV as Spectra so its applications in sailcloth are limited to secondary fibers and areas which can take advantage of its flex, chafe and UV resistance.
Dyneema: Produced by the Dutch company DSM, Dyneema, like Spectra is a highly processed polyethylene which offers good UV resistance, very high theoretical initial modulus and super breaking strength. It also shares Spectra's creep characteristics.
Vectran: The latest new high modulus yarn on the scene, Vectran is a polyester based liquid crystal fiber manufactured by Hoechst Celanese. Vectran has a modulus comparable to Kevlar but due to its molecular composition has better flex and abrasion resistance, although its UV properties are worse. These characteristics make Vectran an interesting candidate as a performance fiber, although it is more expensive than either Kevlar or Spectra.
Carbon: Carbon fibers have extremely high modulus but are not very durable. This problem was addressed with varying degrees of success with the last America's Cup boats. Crews had to be very careful to avoid hard creases in folding. The next Cup will probably see more development, but high cost and inherent fragility may limit this fiber to only the very best funded racing efforts.
Tenacity is the tensile stress at point of rupture expressed in grams force per denier. Tenacity relates to the breaking strength of fibers, and should not be confused with modulus, which relates more directly with a fiber's ability to resist stretch.
Denier is the weight in grams of 9000 meters of a given yarn. A higher denier signifies a heavier fiber.
Flex Strength is the ability of a fiber to retain its strength after being folded back and forth. Flex strength is commonly expressed as loss in breaking strength after flutter testing.
Initial Modulus describes a materials inherent ability to resist stretch. Initial modulus is usually expressed as grams of load per unit of stretch for a certain amount of fiber weight. The higher the initial modulus, the less the fiber will stretch.
UV Resistance measures the effect of sunlight on cloth. UV resistance is usually expressed as the time it would take for a material exposed to sunlight to loose half of its breaking strength.