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Racing Headsails: Uni-Titanium
Uni-Titanium sails are the fastest sails UK Sailmakers makes and that claim is backed up by the fact that customers sailing with Uni-Titanium sails have been able to increase their upwind target speeds compared to previous sails. If you’re interested in making your boat sail as fast as possible, it’s important that you understand what makes Uni-Titanium so different.
Before the development of Uni-Titanium, all sails suffered from shape instability: in puffs, the sail gets deeper and the draft moves aft when the wind softens the opposite happens. Even with string sails, shape instability comes from the fact that most of the load-path yarns run parallel to the leech or luff – along the sail’s primary load paths. There is not enough stability in the pure load-path design for the sail to compensate fully for secondary and tertiary loads.
To overcome these performance-robbing shape distortion issues, UK Sailmakers developed Uni-Titanium, which is a membrane sail with sheets of uni-directional carbon added to the continuous carbon fiber yarn layout in a leach to luff orientation. The uni-directional carbon sheets used have the thickness of the magnetic tape and are just as light. The four layers in a Uni-Titanium sail (PET and Lite Skin or PET and grey taffeta, load-path yarns, uni-carbon layer, and second PET and Lite Skin or PET and grey taffeta) are placed in a variable geometry thermo form in which the sail is UV-bonded under vacuum pressure to become a one-piece finished sail. The result is a sail that holds its shape in puffs and lulls. In fact, Uni-Titanium sails hold their shape until a sail trimmer makes an adjustment to change the sail’s shape.
The Titanium Differences
There are several important differences between the Uni-Titanium construction method and other sailmakers’ membrane products. First, all UK Titanium sails are made with continuous yarns that are spread across the sail running continuously between the three corners of the sail without breaks or interruptions. This array of load-bearing, high-strength yarns is laid dry (without glue) by machine on a skin of 3D shaped PET film with a protective outer layer of Lite Skin or grey taffeta. There is no exposed Mylar in these sails. Being laid dry keeps the yarns from becoming brittle and it keeps the finished weight of the sail lighter. Dry yarns reduce the weight of a sail by 15-30%, which makes for happier crews who have lighter sails to lift and happier owners because the sails last longer.
Unlike most high-tech sails in which structural yarns only run the width of an individual panel, a Uni-Titanium sail’s continuous yarns eliminate seam loads, load-induced seam distortion, wrinkles, or worse yet, seam failure. Yes, there are seams in the PET skin, but they are there simply to add a 3D shape.
Extra Durability With Lite Skin or Taffeta
Until recently, Titanium sails’ PET film was unprotected on their exterior surfaces. This made them susceptible to damage caused by tacking plus damage caused in normal sail handling. Today’s Titanium sails can be ordered with PET films that have their outer sides covered with a layer of either Lite Skin® or taffeta. In either case, by adding these protective coverings, a Titanium sail will enjoy an extended peak performance life without a noticeable increase in the sail’s weight.
Lite Skin, is a thin, lightweight sheet of random, non-woven, polyester filaments applied to what will be the outer sides of the sail giving the sail a mat-black or dark grey appearance. Lite Skin is a proprietary product of Dimension-Polyant Sailcloth.
Taffeta applied to Titanium laminates is a lightweight, finely woven polyester cloth. Like Lite Skin, this taffeta layer will better protect your sail and extend its competitive life. Taffeta is slightly heavier than Lite Skin but it is also more rugged. Taffeta gives Uni-Titanium sails a medium grey appearance.
More about the Titanium lamination process
The PET film is key to a Titanium sail’s lamination “sandwich.” At only 1.3 micrometers thick, this material is incredibly tough. PET is most familiar for its use in plastic bottles and in some paper currencies; try tearing either of these apart and you’ll see how tough PET is. Further, sunlight and heat (up to 50°C/120°F) do nothing to PET, not even making it shrink like many similar materials.
The inner sides of the PET skins are tacky from their copolymer coating. As the yarns are applied, this stickiness holds them in place on the skin’s surface until the final lamination has been completed. The skin-yarn-skin “sandwich” is then placed onto a variable geometry thermoform “oven” in which the sail is UV and heat bonded under 1 bar of vacuum pressure to form a one-piece sail. The copolymer melts around the carbon fibers resulting in a new single-layer structure (the sail) that is substantially stronger than the sum of its parts.
Yes, there are seams in a Titanium sail, but they are there simply to shape the film layers and not to provide any structural strength. Unlike most high-tech sails in which structural yarns only run the width of an individual panel, a Titanium sail’s corner-to-corner, continuous yarns eliminate seam loads, load-induced seam distortion, wrinkles, or worse yet, seam failure. Titanium sails come out of the bag smooth and wrinkle-free and stay that way.