ASPECT RATIO: The luff length of the sail divided by the foot length
BIAS: The direction diagonally across a piece of fabric at 45 degrees to the warp and fill.
COUNT: The number of fibres per inch in the warp or fill.
CREEP: Permanent, continuous elongation of a fibre under a sustained load.
CRIMP: The ‘waviness’ of the fibre or yarn when it is laid over and under fibres or yarns in a fabric. Crimp can contribute to the elongation of a fabric under load as it is pulled out of the loaded direction and pushed into the less heavily loaded direction.
CROSS CUT: A sail panel layout in which the seams run roughly parallel to one another, typically perpendicular to the leech.
DACRON (Polyester): A manufactured fiber introduced in the early 1950s, polyester has been the most common fiber used in sailcloth. It is most commonly referred to by its DuPont trade name Dacron®, the name given to the Type 52 high modulus fiber made specifically for sailcloth. Recent advancements by Allied Signal have produced a fiber called 1W70 polyester that has a 27% higher tenacity than Type 52. Other polyester trade names include Terylene®, Tetoron®, Trevira® and Diolen®. Polyester’s desirable properties include excellent resiliency, high abrasion resistance, high UV resistance, high flex strength and low cost. Low absorbency allows the fiber to dry quickly. Although polyester has been replaced by higher modulus fibers such as those used in the Doyle Stratis products, its proven durability and price point has seen it remain a popular cruising sailcloth fiber.
DENIER: A measure of the weight of a continuous fibre filament. It is the weight in grams of 9,000 metres of a given fibre. The lower the number the finer the fibre. Higher denier, heavier fabrics are generally more rugged and durable.
DENIER PER INCH: Often referred to as DPI and is a measure of the fabrics relative weight and strength, expressed as the numbers of fibres over inch generally in the primary yarn direction.
DYNEEMA: Equivalent to Spectra®, Dyneema® is produced by the Dutch company DSM. It is often used by European sailcloth manufacturers, is available in a wider variety of yarn sizes than Spectra, and is growing in popularity in North America.
ELONGATION: The difference between the initial length of fabric sample and its length after stretching, expressed in 1/100ths of an inch.
FIBRE: The basic entity that is twisted into yarns and then used in the production of a fabric.
FILAMENT: A single fibril of natural or synthetic textile fibre. Filaments are twisted or bunched to form fibres.
FILL (WEFT): The yarns or fibres that run across the width of the roll of fabric, perpendicular to the warp direction.
FILM: An extruded sheet of plastic. Films desirable properties include low stretch, good bias stability, low porosity and good adhesion. Less desirable properties include low tear strength and relatively high physical shrinkage due to creases and folds in the film.
FLEX STRENGTH: The ability of a fibre to retain its strength after being folded back and forth – commonly expressed as a percent loss in breaking strength after flutter or fold testing.
GSM: Weight expressed in grams per square meter
HAND: A subjective term for the way the fabric feels when touched. Terms like softness, crispness and dryness all describe the hand of the fabric.
INITIAL MODULUS: A measure of a material's ability to resist stretch. Initial modulus is usually expressed as grams of load per unit stretch for a certain fibre denier. The higher the initial modulus, the less the fibre will stretch.
INSERT: A yarn or fibre laid directly into a fabric without first being woven or put into a scrim.
LAMINATE: Fabric constructed from layers of film, scrim and/or taffeta flued together under high pressure and/or heat to form a composite sail material.
NYLON: First produced in 1938, nylon is the first completely synthetic fiber developed. In the sailcloth industry, it is used in full radial and asymmetrical spinnakers because of its light weight, high strength, superior abrasion resistance and flexibility. It does not, however, have good resistance to stretch, which is not a big factor in downwind sails, but makes it unsuitable for mains and headsails. Nylon is more susceptible to UV and chemical degradation than polyester and should never be washed with chlorine bleach. Also, its physical properties can change by as much as 100% due to moisture absorption.
PRIMARY YARN DIRECTION: The direction that is most resistant to stretch, typically due to higher yarn count or a higher modulus fibre.
RADIAL: A panel layout where the seams and panels radiate from the corners of the sail in the direction of the highest load.
SAILMAKERS WEIGHT: Weight in ounces of a piece of fabric measuring 2.5 inches x 36 inches
SCRIM: A base fabric component created by laying out fibres in a grid pattern with the fibres joined at their intersection. A scrim can be constructed by passing fill and warp yarns over and under one another; by knitting, in which the fibres and tied at each intersection, or by laying the fibres straight across one another and connecting them at the intersections with glue.
TECHNORA: Produced in Japan by Teijin, Technora exhibits a similar or somewhat lower initial modulus than Kevlar 29 and slightly higher resistance to flex fatigue. The fiber’s lower UV resistance is enhanced by dying the naturally gold fiber black. Technora is most often used as bias support (X-ply) in laminate sailcloth.
TAFFETA: An unfinished fabric employed as a covering, usually in a laminate sailcloth, often enhancing durability and chafe resistant.
TENACITY: The tensile stress at rupture of a fibre expressed in grams or force per denier. Tenacity relates to the breaking strength of fibres and should not be confused with modulus, which relates more directly with a fibres ability to resist stretch.
TENSILE STRENGTH: A measure of the ability of a fibre, yarn or fabric to withstand pulling stresses.
THREADLINE: The direction of the fibres or yarns in the warp, fill or bias.
UV RESISTANCE: A measure of the effect of sunlight on cloth. UV resistance is usually expressed as the time it would take for a material exposed to sunlight to lose half of its breaking strength.
WARP: The yarns or fibres in a fabric that run the length of a roll or cloth and in a woven fabric are interlaced with the fill (weft) yarns.
WOVEN: Material made by interlacing fibres over and under each other in a regular pattern. Types of weaves include: plain, leno and basket among others.
YARN: A continuous strand of fibres created when a cluster of individual fibres are twisted together. Yarns are used to create fabrics.