As you can see from this table of yarns characteristics, there is a wide variation in the strength and stretch resistance of the various yarns. Besides the type of yarn, there is also a choice of the size of yarn to be used.
Other factors may be important too. Some yarns are impervious to UV rays (carbon for example) while others degrade rapidly when exposed to sunlight.
The durability of a yarn may be a consideration. Experience has shown that Technora (usually died black to protect it from UV) is the most durable of the aramids while Spectra or Dyneema is the best when it comes to bend and flex strength.
BELOW: An all carbon laminate on a Twaron scrim.
LEFT: A Kevlar laminate with a taffeta on one side. For performance cruising boats, MatriX is available with taffeta on both sides. RIGHT: A laminate made with a blend of Twaron and Carbon yarns on a black polyester scrim.
Yarn Layout and Distribution
Last but not least is the yarn layout and distribution. AccuCut gives the designer complete flexibility to tailor the yarn layout exactly to the predicted load map of a particular sail. In this process, the sail is typically broken into sections. Then depending on the size and intended use of the sail, the designer will determine the DPI (denier* per inch) each section of the sail requires. Armed with a DPI and a yarn type and size selection, he lays out the yarn paths and their spacing (concentration). This is a time consuming and critically important step that results in putting strength where strength is needed while eliminating weight and cost (yarn) where it is not needed.
* Denier is used as a measure of the size of a yarn. Specifically, denier is the weight in grams of 9000 meters of a given yarn.
Each section and each reef (in mainsails) is done separately before the combined layout is fed to the computer.
Once the design and engineering of a MatriX sail is complete, the next step is to fabricate the skin. The film blank is covered with a group of parallel yarns (up to 18 yarns can be laid at one time) by a computer driven machine that follows the designed yarn layout exactly.
In cases where the sailskin is going to be cut apart to allow for a shaping seams, the machine leaves a step so that after the seam is made, the yarn ends meet exactly as if they were continuous (see below). Shaping seams are extra wide and glued together with modern, super strength adhesives. In most cases, the seams are stronger than the laminate itself. In cases where shaping seams are unnecessary, the yarns will in fact be continuous, running uninterrupted from corner to corner or corner to edge.
When the yarn laying process is complete, the selected scrim and top film are laid down. Scrims are loose weaves of individual yarns (like a big fishnet) and are used to pick up off thread line loads and to add more tear strength to the sail.
Now it's time for the lamination process. More than anything else, it's the quality of this process that determines how good your sail will be and how long it will last.
Good lamination results from the application of three elements:
1. Pressure
2. Heat
3. Time
The first part of laminating a MatriX sail is the application of vacuum pressure. We use a vacuum bag technique to make sure that all the parts of the laminate (bottom skin, yarns, scrim & top skin) are pressed into contact with each other.
Once the vacuum has been drawn, we apply heat by exposing the materials to infrared radiation. This assures that the adhesive on all the materials, even those in the bottom of the lay-up, is heated to the proper temperature.
Now a separate combination of heat and pressure is applied by passing a number of heavy heated rollers over the entire surface of the sail. The additional pressure amounts to three times that of the vacuum already in place and it presses everything together for an air free, solid bond. When the process is complete, the sailskin is cooled gradually. Then it is moved to the loft floor where it lies flat for from 24-48 hours allowing the adhesive to cure completely.
Once the design and engineering of a MatriX sail is complete, the next step is to fabricate the skin. The film blank is covered with a group of parallel yarns (up to 18 yarns can be laid at one time) by a computer driven machine that follows the designed yarn layout exactly.