A Brief History of Sail Design.

For hundreds of years, sails were made by sewing together pieces of woven cloth. For centuries ago, this was a tough cotton canvas. You know one of the descendents of this sailcloth – in fact, you may be wearing it!

The word "jeans," as in "blue jeans," comes from the word "genoa." Long ago, sailors and sailmakers discovered that the tough fabric that powered the cargo haulers of the day could also be sewn into tough work trousers... and thus were born jean pants – though they weren't blue at the time.

However, cotton is prone to stretching out of shape with use – that's why your old jeans fit better and a new pair must be "broken in." And water weakens cotton fibers. The limitations of this fiber for sailcloth are obvious. But this didn't matter so much as long as most sailing was downwind. Perfect shape didn't matter much; sailors just needed something that would get in the way of the wind.

Once sailing technology progressed to the point where ships could tack into the wind, the three-dimensional shape of the sail became crucial. Nowadays, sails are not just flat triangles – two-dimensional – they are also designed to billow out into a specific aerofoil shape when held at the correct angle to the wind. In other words, sails are triangles with depth – a third dimension. And cotton's tendency to stretch and sag with use becomes a much greater impediment to maintaining a sail's shape over time.

With the advent of rayon, Dacron, and other synthetic fibers in the late 20th century, sails could be tougher, lighter-weight, more water-resistant, and hold their shape better over a longer life, compared to older sails made out of natural fibers such as cotton.

But how does one create a three-dimensional shape out of two-dimensional (flat) pieces of woven cloth? This is where the art and science of a top-notch sail loft comes in. It all depends – or did, until the past 15 or 20 years – on how you cut the pieces and sew them together. Top sail designers know the tricks to building in "shape" – the aerofoil shape that gives the sail its power.

About 20 years ago, a revolutionary new sail technology was developed. Sails made with this new technology are known variously as "laminated," "membrane," "load-path," or "string" sails. They are also sometimes known as Mylar or Kevlar sails.

These sails are composed of multiple layers or membranes of high-tech, high-strength materials. The exact technology used varies from loft to loft, but typically starts with a protective layer of transparent Mylar or Kevlar.

Then, load-bearing fibers or "strings" are laid down according to computer analysis of expected load paths. These fibers can be carbon, a high-tech material known as aramid, or, increasingly, a mix of carbon fiber and aramid.

The most effective pattern for the fibers to follow is a hotly debated topic among lofts. Each of the major lofts profiled here has its own proprietary technology for achieving this.

Adhesives are applied, and another layer of Mylar or Kevlar. Finally, the whole thing is subjected to a high-heat process in which the layers are bonded together.

In racing, of course, lighter is better and shape is critical. Racers are keen to embrace every new technological advance that enhances these sail characteristics.

Nowadays, every major racing team worldwide uses laminated sails. They must, in order to remain competitive. Sails made with older technology simply cannot compete in terms of strength and efficiency per ounce of sail material.