LADIES AND GENTLEMAN
To help you evaluate all of the different sail materials that are available, and to help you make an educated decision about your sail purchase, Oxo Sailmakers has developed the following Fabric Guide.
For a definition of terms, please refer to the Fabric Glossary.
For a description of the different fibers used in sailcloth, please refer to the Fiber Guide.
On the most basic level, there are three different types of sailcloth:
The earliest sailcloth was constructed of woven flax. In the 1800s, the switch was made to American cotton and later to Egyptian cotton. Currently, most woven sailcloth is constructed out of Dacron, although other fibers such as Kevlar, Spectra and Pentex see limited use.
Magnified view of tightly woven Dacron.
This is a fill-oriented weave, in which the warp fibers (running from the upper left to the lower right) are woven over and under the straight fill yarns. In this construction, all of the crimp is in the warp and stretch in the fill direction is minimized.
Even though it was almost 40 years ago that Dacron replaced cotton as the primary sail material for fore and aft sails, it is a bit difficult to explain all the subtleties of this fabric. Dacron sail fabric has continued to develop since it was introduced in the mid-fifties. Unfortunately, the difference between a top quality Dacron fabric that will perform well for many years and a fabric that will quickly break down and distort is not discernible by casual examination. In order to make a full assessment, the specific fibers employed and the production history of the fabric must be known. Even then, extensive testing is required to ensure that each roll of fabric is of satisfactory quality.
There are four primary factors that affect the quality and cost of Dacron sailcloth:
TIGHTNESS OF THE WEAVEThe tightness of the weave varies for a number of reasons, including:
TYPE OF FINISH The type of finish used on the sail greatly affects the “hand”, or feel, of the material. Also, highly resinated materials often rely on the resin for stability and when, after extended use, the resin begins to break down, the sail begins to change shape. Resin quality and quantity greatly affect the overall quality and cost of the sailcloth.
According to these factors, the price of woven sailcloth can vary a great deal. Woven 8 oz. Dacron fabrics range from $.35 per square foot to $1.10 per square foot depending on the price and quality of the yarn, the manufacturing costs (smaller denier fibers require more shuttle passes and more time to weave than a larger denier fiber), yarn content and type of finish. Thus, when shopping for a Dacron sail, ask your sailmaker:
There are many different styles of Dacron for every application from racing dinghies to large cruising yachts, and your oxo Sailmaker can help you find the right style for your boat.
There are as many, if not more, variations of laminated sailcloth as there are of woven sailcloth, but there are four main construction styles worth noting.
Type I: Woven/Film/Woven or Woven/Film
Woven material on one or both sides of film is used in both very inexpensive cruising fabric as well as some of the high-end fabrics. Lower-end versions of this construction consist of a loosely woven Dacron taffeta laminated to a layer of film. In this application, the film provides most of the stretch resistance and the taffeta is mainly utilized to enhance tear and abrasion resistance. The high-end version of this construction utilizes a woven Spectra or Kevlar taffeta laminated to a film layer. The high-modulus woven fibers provide the threadline stretch resistance and the film controls the off threadline stretch. In some newer styles, off threadline reinforcing yarns, usually Spectra® or Technora®, are laid into the laminate. This is a relatively cost and weight efficient method of producing a laminate. Due to the crimp in the woven yarns, such laminates are inherently more stretchy than those produced with a core of inserted warp yarns or a scrim.
Type II: Film/Scrim/Film or Film/Insert/Film (a.k.a. “Film-on-Film”)
In this construction, the structural fibers (either in scrim or insert form) are sandwiched between two sheets of film. This way, the load-bearing members are laid straight and, unlike wovens, there is no crimp. This takes full advantage of the fiber’s high modulus in resisting stretch. Additionally, laminating film to film creates a very strong and dependable bond that allows a minimum amount of glue to be utilized.
Although Kevlar is the most common structural fiber used in this construction, Pentex is growing in popularity, particularly in classes where aramids and other exotics are prohibited. This is also the laminate type used for most carbon fiber sailcloth, and for the Oxo D4 sails.
Unfortunately, film is not as abrasion or flex resistant as a woven and does not protect the structural fibers from harmful UV rays. Because of this, material of this construction is only suitable for short-lived racing sails in which minimum stretch and weight are the primary goals. In some sails, a UV film is added to protect the core fibers from degradation. In other instances, where additional durability is desired, a taffeta is added to one side to reduce breakdown from flex and increase abrasion resistance. This style is very popular with PHRF sailors who need performance plus the value of durability.
Type III: Woven/Film/Scrim/Film/Woven
Laminating a woven material (taffeta) onto both sides of an oriented scrim takes advantage of the straight yarn principle and the film-to-film bonding. In addition, the taffetas protect the film from both flex fatigue and abrasion and protect the core fibers from UV degradation. The core fibers include polyester, Spectra®, Kevlar®, Pentex® and most recently Vectran®. In many cases one fiber is used in one direction with another at 90 degrees to it and at times even a third is added at an angle to provide off threadline support. The taffeta can either be a lightweight polyester or a woven Spectra® or Kevlar®. One might think that having a high modulus core plus a high modulus woven taffeta would result in the ultimate fabric. However, although there are advantages, the efficiency of the straight yarns in the core is so great that they control and dominate the stretch characteristics of the fabric, and even a high modulus taffeta adds little to the overall stretch resistance. Such fabric is therefore inefficient in terms of cost and weight. In some special applications such as Around Alone races, Kevlar inserted fabrics with Spectra taffetas are used. In these styles, the Kevlar controls the stretch and the Spectra supplies the abrasion resistance so that each fiber is doing what it does best and, though expensive, the fabric meets its design goals.
This is a very attractive construction when utilizing high modulus fibers that have superior yarn qualities in every respect expect for UV resistance. As long as the UV-sensitive fiber is in the interior, it remains protected from UV exposure. For heavier weight styles, extra layers of structural fiber separated by film are often added, creating a multi-ply laminate particularly suited for the high load applications of the megayacht market.
Type IV: Woven/Scrim/Woven
Wovens on both sides of a scrim with no film is an enticing construction method in that it eliminates the film layer. The dilemma with this type of construction has been getting enough high modulus yarn into the sandwich, and still being able to get a satisfactory bond. Bonding two woven fabrics to each other is not easy and adding inserted yarns in the middle makes bonding even more difficult. Controlling the off threadline stretch has also been a problem. However, research and development continues on this front as the drawbacks of film become evident in many of the megayacht sails in which durability and a long working life are key.
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In summary, laminates are gaining popularity in building everything from boats to planes, primarily because it is proving to be the most efficient way to utilize the latest materials. However, multi-layered materials that rely on glue for structural stability constantly battle delamination of the various layers. Also, although all sails mildew, it has proven much trickier to remove mildew between laminate layers than on the surface of Dacron sails. Although new chemicals have been produced that make this possible, there is an added time and monetary investment.
For a more in-depth look at construction methods, fibers and sailcloth samples, please contact OXO loft.