[color:"blue"]The object for most sailmakers is to come up with the best design, for a given boat, and use materials that will maintain this design over a wide wind range. [/color]
I disagree. There is no "best design" for a wide wind range. The more it is "best" the narrower is the wind range. A good example are Zuccoli sails for the Tornado Class, particularly the jibs. They are numbered and cover VERY LIMITED wind ranges. Zuccoly Dacron tri-radial sails still show some desirable geometric changes as the wind increases but their mylar counterparts are really good for their designed wind range, whis is generally a narrow one.
Sails that can be used in a wide wind range are precisely those that do change their shape, though very slightly and "in the right way" (that is, "self-flattening" in the breeze). Aided by important trim changes at the rig level, these sails can perform reasonably well ove a wider wind range.
[color:"blue"]There are two lifes for a sail,the life of the sail cloth, and the performance life. The performance life, is the length of time that a sail will matain its designed shape. The cloth life, is the time a given materal will last after being subjected to wind loads, flutter, UV exposure, etc.[/color]
I agree, the performance life of a Dacron sail, for instance, is usually 1/10 of its "mechanical" life.
[color:"blue"]In most cases, materals that have low stretch,light weight, and good durability are most prefered.[/color]
The question is "why". It's dangerous to take for granted that only low stretch, light weight materials can make fast sails. In some cases, as for bigger multihulls, other factors become more important. Some self flattening ability, for instance, is highly desirable, since masts on these boats tend to be almost non-flexible.
[color:"blue"] There are always comprimises. The materials that best fit this discription, are also the most expensive.Sails made with low stretch materals, can be designed fuller. This gives more power in light winds, and will not stretch and become too full as the wind builds, compared to their more stretchy counterparts.[/color]
This may be true for jibs but is not true for many mainsails. The Tornado mainsail, for instance, is cut almost totally flat, whatever the cloth used. It's the mast and the battens that give the sail its final shape. Although enormously successful, the Tornado mainsail is a blatant contradiction to the concept of the "preformed" sail.
[color:"blue"] Pentex is a good all around fiber for most beach cat sails. This fiber has twice the modulas as polyester, giving it twice the strength, and about 30% less stretch, as polyester. The price is also good. Using stronger cloth with less stretch, enables the sailmaker to go down in weight, as well. [/color]
This is true, particularly for beach cat mainsails.
[color:"blue"] Jibs are often made with a preminum dacron called square dacron. This is a balenced weave and can be used in a triradial cut. This is a fairly low stretch dacron, and will stand up better to the abuse that jibs experance. The mains have many full battens that reduce flutter, they wear much better because of this. Laminates will last much longer in the full batten mains.[/color]
Battened jibs (of Tornados' , for instance) can be made of Pentex, too. Other laminates, as the Brazilian Prolam, are made in a different way and resist in a better way the abuses that jibs experience.
Arnaldo Andrade
adrianno@openlink.com.br 
