Yes, especially for spinnakers that will be used for broad reaching or running where strength for weight is more important than stretch resistance. For spinnakers that will be used on a close reach, a more stable nylon or a light laminate might be a better choice because the sail needs to retain its shape to perform properly.

Pentex is also a polyester: How is it that Pentex sails perform better than regular Dacron?

Pentex is a modified polyester that combines all the great qualities of Dacron without the one major drawback—stretch.

Pentex is a modified polyester that combines all the great qualities of Dacron without the one major drawback-stretch. Once the fibers have been modified they lose some of their ability to shrink when they are heat-set, so Pentex is not woven, but rather used as a scrim in a laminate. The combination of the fabric being a laminate and used for radial construction results in sails that perform a lot better than those made from regular woven Dacron used in a cross-cut configuration.

What are the attributes and drawbacks of Spectra?

Spectra has very low initial stretch, but over time under a constant load, it starts to creep, or elongate. This is not good for high-performance racing sails, but Spectra's other qualities like good UV resistance and terrific flex make it a perfect fabric for performance cruising sails, especially on large boats. Unfortunately, when there is unrest in the world the price of Spectra goes sky-high because it is also used in great quantities by the defense industry.

Why would you not use Kevlar for cruising sails?

You can use Kevlar for cruising sails, but you have to be very careful how you engineer the fabric. Kevlar loses its strength when flexed by flogging or exposed to sunlight. If you are able to engineer a fabric where the delicate Kevlar yarns are sandwiched between UV-coated taffetas and the yarns run along load lines and not at right angles to the way a sail flaps in the wind, i.e., across the sail, you can build a Kevlar sail that will last a long time. It's more suitable for really large boats where you need a more complex laminate and Kevlar is only one of a number of yarns utilized.

What about Vectran? Where does this fiber fit in?

Vectran is growing in popularity for a number of reasons. It is incredibly strong and does not lose strength when it is flexed. Unfortunately, like Kevlar, it's extremely UV sensitive and so the fabric needs to be carefully engineered to protect the yarns from the harmful rays of the sun. Is there a future for PBO in sailmaking?

Possibly. Weight-for-weight, PBO has better strength and stretch characteristics than any other currently available fiber, but what it gains in strength and stretch resistance, it loses immediately if exposed to any kind of light, not only sunlight. If sailmakers have an application where you need the positive attributes of PBO and can, through clever engineering, minimize the negatives, it might be useful; however for now the fiber is so expensive and there are so many other better choices available that PBO is losing popularity.

And carbon. Does it have a future?

Most certainly. You will be seeing a lot more carbon in sails, especially at the top end. For now it's usually used as part of a blend with other fibers picking up where carbon is weak, namely in flex. Different types of carbon are being developed that have better flex properties, but in order to gain better flex they lose in other areas like stretch resistance. It's a balancing act, but the fiber is so terrific that fabric makers and sailmakers are working on ways to incorporate it into their sails.

Can woven fabrics be laminated?

Certainly. While one of the advantages of laminated fabric is that the load-bearing yarns can be applied as a scrim, i.e., loose grid of fibers, you can still laminate a woven substrate to a film. These fabrics are very good if you are looking for rugged durability like a Spectra for an Around Alone race or for a large offshore cruiser where you need a high yarn count to handle the loads. It's fairly difficult to engineer these fabrics if Spectra is going to be he principal yarn because Spectra is a slippery fiber that does not adhere very well, and it's better if there are gaps between the fibers, as in a scrim, so that the adhesive can bond between the fibers. On the other hand, some fabric engineers have developed adhesives that will bond to Spectra without delaminating.

What are the differences between fill-orientated fabrics, warp-orientated fabrics and balanced fabrics?

Fabric engineers can vary the sizes of the yarns running either along the length of the fabric, i.e., the warp, or across the fabric, i.e., the fill, so that a woven material can have more or less strength in a certain direction. For example, a sailmaker might want a fabric that has a lot of strength in the fill direction so that he can build a blade jib that has the loads running pretty much up the leech of the sail, i.e., in the direction of the fill. For a low-aspect sail like a No. 1 genoa where the loads are fairly evenly distributed throughout the sail, he could ask the fabric maker for a balanced fabric, one that has similar yarns running in both the warp and fill directions.

What does heat setting do to a woven polyester fabric?

Understanding about sailcloth options will help you when it comes time to make your next sail purchase.

The aim with all woven fabrics is to get a tight weave so that the fabric does not stretch, especially on the diagonal, or the "bias." Fabric makers use various techniques to create a tight weave and one of the best ways is to pass the fabric through an oven or over heated rollers. This causes the yarns to shrink by as much as 15 to 20 percent, which dramatically tightens the weave.

What are the drawbacks of fillers in woven polyester fabrics?

Dipping the fabric in a bath of melamine resin coats the fabric, allowing the resin to penetrate the gaps between the fibers and stabilize the fabrics increasing its resistance to bias stretch. The problem is that over time the resin starts to break down, and the crystals that once gave the fabric terrific stability are no longer there. Without the resin, the fabric is more susceptible to stretching. This is why fabric makers rely more on a tight weave than on fillers. Note that a stiff, resinated fabric is easier for the sailmaker to work with, but it's tough on the hands when handling the sail. Like most things in sailing, adding resin needs to be balanced against many other factors.

What does the calender do?

Calenders are giant heated rollers that apply tremendous pressure on the fabric, as much as 150 tons, and some fabrics are passed through the calender a number of times until the fabric takes on a high sheen. At this point the woven Dacron fabric is as nonporous and low-stretch as it's ever going to be.

What are some of the things to look for in a good Dacron?

Yarn quality is important. Ask your sailmaker what type of yarn will be used for the fabric. Remember that Type 52 Dacron is the highest tenacity fabric and offers a premium balance of high strength, low stretch, and maximum shrinkage when compared to other Dacron types. You should also look at the tightness of the weave, note whether the fabric is fill orientated, balanced, or warp orientated, and know how this point relates to the sail you are buying. Other than that, ask your sailmaker about tear resistance, abrasion resistance, and whether the fabric has some UV protection. Remember to compare apples to apples when comparing the price of sails. One of the biggest discrepancies will be fabric choice.

On a laminated fabric, what do the taffetas do?

The taffetas can add abrasion resistance, and if they have been UV treated they can protect the light-sensitive load-bearing yarns in the laminate. For example, if the principal fiber is Vectran, sandwiching the Vectran yarns between two UV-treated taffetas will extend the life of a fabric appreciably. They add weight to a sail, but they also add durability, and for offshore sailors taffetas are well worth considering. How does Cuben Fiber differ from ordinary laminated fabrics?

Cuben Fiber is a much more complex means of creating fabric. For a start, it is made of many layers of untwisted filaments laid in a multitude of directions. Once the fabric has been engineered, it is loaded into an autoclave and baked under high heat and pressure until the individual filaments and film become one, making it extremely strong and stretch resistant for its weight.

Brian Hancock's book offers comprehensive answers to the questions in this article as well as to everything you ever wanted to know about sail trimming.

Can I have Cuben Fiber sails for my boat?

If you are willing to pay the price you certainly can. The process of making the fabric is very labor intensive and therefore the cost of the raw fabric is expensive. Once you get into the heavier weights of fabric and boats with much higher loads, the price difference between numerous layers of, say, Spectra and Cuben Fiber becomes less a factor and Cuben Fiber becomes more of an option.

Can you explain why sailmakers started to ply sails?

Cross-cut sails have the same weight of fabric running across the sail even though the loads vary from one end of the sail to the other. The loads up the leech, for example, are much greater than loads up the luff. Before the advent of radial sails, the only way sailmakers could save weight and engineer more efficient sails was to build a sail with a lighter base fabric and then add a second ply in the high-load areas. For example, they would use a balanced Dacron for the body of a mainsail and add a ply of fill-orientated Dacron up the leech to take the increased loads in that area. They would use a number of different techniques to transition the two-ply area into the single-ply area, such as cutting the second ply in a crescent or a saw-tooth pattern.

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