Sailcloth Explained

We only use cloth provided by the four largest and most reputable suppliers globally

The secret to cutting a good sail lies with the choice of the most appropriate cloth. When a sail is designed there are many interacting variables such as size, displacement, righting moment, aspect ratio of the sail (the ratio between the height and foot of the sail), intended use, coastal cruising, ocean passages, inland, extended cruising in areas of high uv, racing, charter, sheltered or open waters, performance in a longevity sense and performance in a speed sense; together with decades of experience with different yarn types and constructions and tens of thousands of sails with millions of miles of cumulative mileage all being taken into account.
The other side of the equation is that various sailcloth designs are better suited to specific applications. It is generally understood that the ultra lightweight high tech laminate fabrics are faster but have a shorter lifespan. What is less well understood is that some material is designed with extreme fill orientation (less stretch across the roll) and is best suited to high aspect ratio sails (tall and narrow), some square constructions are suited to low aspect ratio sails (equal stretch in both directions for example short luff long footed sails) and some warp orientated (less stretch along the roll) specifically designed for radial cuts. Whilst it makes sense to make tall narrow mainsails where 95% of the major load is across the panel a different approach is appropriate for a long footed overlapping genoa.


Cloth 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