Sail Cloth Choices – You Get What You Pay For

Sail cloth material technology has advanced considerably over the years. Once made of hemp, cotton or linen, the sail cloth material of choice these days is almost invariably synthetic. Whereas powerboat owners will find little of relevance in this chapter, sailing enthusiasts should certainly be interested. Sails are expensive. A good quality mainsail for a mid-sized yacht can easily set you back several thousand pounds, which by any terms of reference is a painful hit to your wallet. In short, if you want them to remain serviceable, it pays to look after them.

The term ‘serviceable’ needs qualification. Some years ago, one of Britain’s favourite boating magazines ran a series of articles where experts crewed on a variety of readers’ sailboats and helped them get the best from their sails. In many cases the results were disappointing, not because the experts weren’t expert enough but because the sails had deteriorated beyond the point of redemption. Not all of the participating readers were grateful for the news.

Stretch, chafe and UV attack are the foes. Sails are never better than when they are brand new, and it’s depressing to learn that it’s downhill from there. They start to stretch from the first time they are set, but the rate at which they do so depends on a number of factors. If your sails are built of too light a cloth, or have been carried in wind strengths outside their comfort zone, they can be ruined in a single incident. Then there’s the sunlight. If they are left uncovered when not in use, their lives will inevitably be shortened.

Also much depends on the quality of the sail cloth material. Most sails are white and triangular and it’s difficult to tell the good from the bad at a distance. It was once the case that new boats were delivered without sails, leaving it up to the owner to elect the sailmaker of his choice as he would go (as one did, of course) to his bespoke tailor. Elitist this might seem, but at least the responsibility rested with the owner. These days, sails are usually included as part of the package and it may be that the boatbuilder negotiated hard to obtain as keen a price as possible, with a consequent influence of quality. And herein could lie the problem. To expect long life from a budget product is to indulge in self-delusion. As in most things, you get what you pay for.

But, before we discuss how to take care of our sails, let’s take a look at what’s available

Woven Cloths

The majority of modern sailcloths are woven from polyester fibres – chemically a close relation of resin found in our boats’ mouldings. ‘Dacron’ is a trade name that has become almost generic in the sail cloth context, having effectively displaced the British brand ‘Terylene’. Both are polyester products and identical in composition for all practical purposes. Nowadays, cruising sails for the most demanding applications can also contain higher performance (meaning lower stretch) yarns such as Vektran® and Pentex®.

The weave can be ‘balanced’ or ‘unbalanced’. Balanced weaves have an equal weight of yarns in both the warp and weft (also called ‘fill’) direction while unbalanced weaves have heavier yarns in one direction – usually the weft.

Sailcloths are amongst the most compactly woven cloths in existence, with their quality depending largely on the density of the weave. High quality cloths are woven slowly and very tightly, while cheaper ones are woven on higher speed looms that result in a looser weave. After weaving they are heated to shrink and compact the yarns still further.

woven sailcloth stretch resistance

Nearly all woven sailcloths are post-treated by impregnating them with a plastic resin – typically melamine, sometimes along with other additives. This process helps stabilise the cloth against distortion, particularly in the ‘bias’ – that’s to say diagonal – axis (see Fig right). The cheaper, looser sailcloths, need more melamine filler than the high quality ones. Indeed, the latter are incapable of absorbing as much, due to their denser weave.

The proportion of filler in a sailcloth affects its service life. The flapping and shaking to which sails are naturally subject, gradually breaks down the melamine so the stability of the cloth diminishes over time. Overstretching the sailcloth can have the same effect in an instant.

High performance laminates

The last few decades have seen huge advances in this technology. Instead of the familiar woven cloth, thin sheets of polyester – trade name ‘Mylar’ being representative – form a sandwich containing load-carrying filaments that can be oriented to closely match the stress patterns within a sail. Free from the over-and-under constraints of woven cloths, laminated sails can be precisely engineered.

The Mylar itself has impressive structural properties, with the low-stretch filaments – polyester, carbon fibre, HMPE, aramids amongst them – contributing yet more strength. Where weight is less critical, such as for cruising sails, laminates often have outer skins of woven polyester ‘taffeta’ to protect them against chafe. The artwork left shows a typical construction

The relatively stretchy taffeta adds nothing to the strength and is only there to protect the structural components from wear. Adhesives are used to bond the laminates together. A typical cruising laminate is shown right.

The higher costs of laminated sails have deterred many non-racing skippers from buying them, but they are gradually making inroads into the cruising scene. Being quite stiff to handle, they are ideal for roller reefing systems where you simply wind them in or out.

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And they do come with one big advantage. Whereas the deterioration of a woven sail can be represented by a straight line graph that declines from brand new to totally ruined, laminates degrade much slower in serviceability terms. This means the owner will see little fall-off in performance over the first few years, followed by a rapid plunge as and when the laminate breaks down.

The skipper whose sailing is limited mainly to fairly gentle weekend cruises could see many. many years of perfectly acceptable service from a suit of budget priced sails. However, more ambitious sailors – particularly those who race or who regularly go offshore will usually see better value by spending more on better quality sails.

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Sail Cloth Choices – You Get What You Pay For

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