The sail fabric (what the sail is made of), used to be made of cloth for most of the history of sailing. They were usually made of materials such as hemp, cotton and flax or the composite canvas, which was often used on square rigged ships.
Modern sails on the other hand are not made from these natural fibre materials, since the improvement in advanced material research has caused an influx in more weather hardy, stronger and time-resistant synthetic materials ranging from low cost polyester or nylon to expensive carbon fibres or aramids.
The physical properties of sails are now of great importance, especially with the advent of the modern racing yacht.
Elasticity (stretch resistance per unit weight - higher is better for upwind sails), tensile strength (breaking strength per unit weight - higher is better for all sails), creep (which is the stretch caused by weight over a time period - materials with creep will lose their shape over time, but have greater elasticity), UV resistant (strength lost by ultra violet rays from the sun - higher is better for sails) and flex loss (strength lost due to bending) are all key factors in evaluating materials for sails as well as the cost of the material.
A good sail would have all of the factors above as well as important things like being a light weight material and having interesting colours for aesthetics (for instance an aramid sail would have a typical golden colour whilst a carbon fibre sail would have a grey complexion).
Once a material is found for the sail it is then 'weaved' into a film of material. The films are then attached together as well as woven cloth to create a laminate. The laminate is then finally woven to create the sail.
As you can see there is a difficult and long process to create sails as well as the use of advanced materials and this is the reason they cost so much (usually £1000 for a new set on a dinghy and ten or twenty times that on a yacht).
Return from Sail Fabric to Sailboat Sails
Return from Sail Fabric to Started Sailing