Sailmaking Glossary


A diagonal across a piece of fabric at 45 degrees to the warp and fill


The count of a piece of fabric is indicated first by the number of warp threads per inch, then the number of filling picks per inch


The property of fibres to gradually stretch under a constant load


Length or waviness added to a yarn when it is woven over-and-under in a piece of fabric. Crimp can contribute to the elongation of a fabric under load


DuPont’s trade name for polyester fibre


A system for coding filament yarns and fibres, with low numbers representing finer sizes and higher numbers representing heavier yarns


The difference between the length of a stretched sample and its initial length, expressed in 1/100ths of an inch


An individual warp yarn


The weakening or loss of stretch resistance of a fabric due to flutter or impact testing


The yarn or fibre running across the width of the fabric at right angles to the warp

Flutter test

Simulates the wear and tear a fabric will experience in a sail; a sample is spun on a windmill for 30 minutes


Woven fabrics in unfinished state


Softness or firmness of a fabric

Impact test

Similar to the flutter test except that the sample beats for 15 minutes against an obstacle placed at right angles to the windmill


Equally stretch-resistant in all direction, which is one of the advantages of Mylar for sailcloth use


DuPont’s trade name for a family of high-strength aramid fibres


A layered fabric made by bonding a substrate to one or two plies of Mylar film


The number of pounds exerted on a 2” x 16” test sample. A Load-Deformation Curve expresses the relationship between the change in dimension of the sample (in 1/100ths of an inch) as a result of an external load. It is usually expressed as a graph


The measure of stretch or elasticity of a fabric. High modulus = Low stretch

1% elongation

The load required to stretch a fabric sample by 1% of its original length; commonly used to indicate the high-load stretch resistance of Dacrons and Mylar/Dacron laminates


An individual filling yarn


A Polymer of terephthalic acid and ethylene-glycol spun and drawn to produce a strong, tough, abrasion-resistant fibre

Primary yarn direction

The orientation (warp or fill) in which a fabric is the most stretch resistant


The ability of a yarn or fibre to return to its original length after it has been stretched

Sailmakers weight

Weight of a 35” x 28.5” sample

Secondary yarn direction

The orientation (warp or fill) 90 degrees to the primary yarn direction


The edge of a piece of fabric


A highly modified polyethylene fibre developed by the Allied Corp. with a stretch resistance similar to Kevlar


A fabric that is bonded to a Mylar film


The breaking strength of a yarn of fabric stated in force per unit of the cross-sectional area

Tensile strength

The ability of a fibre, yarn or fabric to resist breaking under tension


The yarn or fibre running the length of a fabric