Foul-Weather Gear Round-up: Outer Layer Materials - Sail Magazine

Foul-Weather Gear Round-up: Outer Layer Materials

Although breathable fabrics are now pretty much universal, all breathable fabrics are not made by Gore-Tex. Ever since the company’s patent on semi-permeable microporous PTFE expired over a decade ago, a number of other manufacturers have started created similar materials, or “membranes,” that work equally well.
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Although breathable fabrics are now pretty much universal, all breathable fabrics are not made by Gore-Tex. Ever since the company’s patent on semi-permeable microporous PTFE expired over a decade ago, a number of other manufacturers have started created similar materials, or “membranes,” that work equally well.

For our complete foul-weather gear guide, click here.

Musto, for example, includes Gore-Tex throughout much of its gear line. But Helly Hansen is completely Gore-Tex free as is Gill. Instead these companies employ their own, proprietary waterproofing technologies, in the interest of cost and manufacturing efficiencies.

Helly Hansen’s Ulrikson, for example, says that by going with its proprietary Helly Tech line of weatherproofing, his company can forego the often rigid conditions Gore Tex places on those companies that choose to go with its products.

“The challenge is to find the balance between blocking wind and water out and still being breathable enough,” Ulrikson says of Helly’s work on its proprietary Helly Tech fabric.

Gill’s David Pritchard agrees, noting that while his company incorporated Gore-Tex in some of its products in the past, it has since moved on to work with multiple suppliers—all the while submitting its products and the materials to third-party testers, like the Center for Technical Textiles at the UK’s University of Leeds, to ensure top performance.

 Micropores

Micropores

In addition there are two types of breathable technologies to be aware of—Gore-Tex-style “mechanical” membranes containing countless micropores—basically thousands of tiny holes that are large enough to let water vapor out, but small enough that liquid water can’t get in—and hydrophilic coatings that transport water via chemical diffusion and differential pressure (basically, the difference between the humidity of the air inside a garment and the humidity of the outside air). 

Because hydrophillic membranes need to be dried out after a few hours of heavy use to maintain optimal breathability and microporous membranes don’t, the latter are relied on as the primary waterproofing layer in heavy-duty bluewater gear.

Whatever the brand or waterproofing technology, the two things to look for when evaluating a particular fabric’s performance characteristics are waterproof and breathability ratings. Waterproofing can be determined with a fairly high degree of accuracy through static-column testing: basically, you position a length of 1in-diameter vertical tubing over a piece of fabric and then fill it up with water until it starts leaking.

A typical lightweight rainproof, but not necessarily waterproof garment will be comprised of fabric with a rating, or column height, of 5,000mm or 5Kmm. A higher performance inshore jacket or bibs might include a fabric rated to around 10,000mm, while a bluewater piece might include fabric rated between 15,000 and 20,000mm. For truly bulletproof waterproofing—think Southern Ocean graybeards coming over the cabintop (or waders when fishing a trout stream)—look for fabrics with rating as high as 30,000mm. On the down side, when you get to this level, breathability starts to suffer, but waterproofness is such that the garment can even withstand shallow-depth submersion.

Breathability is a bit harder to quantify, in part because it is affected in practice by a variety of environmental factors, including temperature and humidity. However, standards of measurement do exist and are defined by the number of grams of water vapor that will pass through a square meter of fabric over 24 hours in a laboratory. These can range from 12,000 to 25,000 g/m2/24hr, with the higher number denoting better breathability.

Keep in mind that while waterproofness is waterproofness, breathability is only for fabric “in the raw,” as it were, not stitched and taped into any kind of finished product. The addition of things like abrasion patches, pockets and cuffs can dramatically lower breathability in actual practice.

Note that today’s heavy-duty bluewater gear is typically made using a three-layer fabric, in which a breathable microporous middle layer is sandwiched between a tough outer layer, or face fabric—usually nylon and coated with a DWU (durable water repellent) finish—and a smooth inner lining, or scrim.

GoreTex-Three-layer%20diagram

Gill also offers a 5 dot fabric in its top-end offshore gear thatPritchard describes as a “four-layer” construction, or three-layers-plus. Specifically it features a combination microporous membrane bonded to a hydrophilic layer (the “fourth” layer) sandwiched between the face fabric and an interior scrim. According to Pritchard, the result is a construction that channels moisture that much more quickly, “supercharging” its movement away from the body.

Although more expensive to produce, these kinds of laminates offer the advantage of being lighter and much easier to put on and take off than a two-layer fabric, in which a loosely attached inner lining is required to protect the waterproof membrane from abrading against your body. A three-layer (or four-layer) configuration is also more breathable and easier to move around in, compared to the two-layer fabrics that are more commonly found in jackets and bibs for inshore and coastal use.

In either case, the DWU finish keeps the nylon outer layer from absorbing water so that the waterproofing underneath doesn’t have to work so hard to keep you cool and dry. By causing the water to bead on the surface, as opposed to allowing it to be absorbed by the nylon, it also keeps a jacket or pair of trousers from getting much heaver when it becomes wet.

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