SNOWSHOE MAGAZINE FEATURED ARTICLE:

ThinShell Layering

Merino wool baselayer and ripstop nylon outerwear

Breaking trail with snowshoes is hot and sweaty work. Combining a merino wool baseblayer with a ripstop nylon jacket and trousers can work the trick when the three layer system is overkill.

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Baselayer, fleece, and Gore-Tex shell too much? Then a merino baselayer paired with non-insulated nylon jacket and pants might be just right.

One option is a two layer system consisting of a merino baselayer and a nylon outer layer, which Keith Conover calls a “ThinShell” system.1 Such a system combines the breathability of wool and nylon with wool’s capability to insulate while wet and nylon’s wind resistance.

Baselayer – merino wool

Most people seem to imagine that wool has an endless capacity to absorb moisture. In fact a wool swatch absorbs much less water than a cotton swatch of the same size. After absorbing approximately 30% of its weight in water wool begins to pass moisture on to clothing overlaying it.2 In addition, the breathability of wool means that perspiration exiting sweat glands as vapor is apt to pass directly through without being absorbed by the fabric.3 And while merino is not hydrophobic like synthetic fabrics such as polypropylene and thus does not dry as rapidly, it does retain much of its ability to insulate after becoming wet. In addition, when moist it is much less apt to feel “clammy” next to the skin in the way that wet synthetic fabrics so often do.

Outer layer – nylon

Lightweight nylon combines a degree of wind resistance with a degree of breathability as well as the ability to conserve some of the body heat which would otherwise be lost to the environment via radiation without producing the “boil in a bag” effect during high exertion typical of outer layers which incorporate a waterproof/breathable liner such as GORE-TEX or eVent in their construction. Garments manufactured from such nylon generally go by the name of either ‘windshirt’ when marketed to the hiking/trekking and law enforcement/military communities and ‘windbreakers’ when marketed to the cycling community.

There are a number of models of nylon trousers designed for three season hiking use that may be combined with a merino baselayer, but the author’s own winter trousers of choice are RailRiders’ Winter Weatherpants, a two ply version of their single ply three season Weatherpants.

Aftermarket application of Durable Water Repellant (dwr) is an option with any nylon garment, but bear in mind that the inclusion of dwr comes at the cost of breathability. The author’s recommendation is to maintain an undwred upper and trousers for use on clear days rather than to try and create one-size-fits-all dwr nylon garments which in the end only work particularly well in misty weather and during intermittent showers.

Venting and cinching – design features for function

While nylon has good breathability, high exertion activity can at times lead to the formation of condensation on the interior of garments. This can become an issue for snowshoers should temperatures fall and lead to frosting on the interior of the garment. And while nylon has good wind resistance, this fact amounts to little should sharp gusts force frigid air into a garment’s openings. Both of these eventualities can be forestalled by the choice of clothing making use of design features for the venting of heat and perspiration and the cinching of openings against wind and snow.

Venting. A quarter or half zip long sleeve merino top allows for good venting at the chest and is a fine addition to any winter activewear wardrobe. A full zip outer layer naturally allows for more venting than does a pullover. Venting under the arms is a useful feature for an outer layer, and there are a handful of nylon tops on the market incorporating either mesh inserts or zips at the armpit area, or a handy tailor can install zips there after purchase.The most effective means of venting for trousers is the use of suspenders, for which there are three attachment choices: clip-on, button, and to-the-belt. Gaiters with a toggle or tie top allow for good air flow when not wading through deep drifts, and a few models incorporate a zipped side vent.

Cinching. Cinching may be either of a piece with venting capabilities—as with a zippered top—or fixed—as with a turtleneck. Other examples of the same include hook-and-loop sleeve closures vs. elasticated sleeve cuffs and toggled vs. elasticated bottom hems. Thumb loops are a wonderful means of preventing the entry of snow into sleeves and gloves, and a hood is a great option for conserving radiant heat and keeping icy blasts off the ears.4 While a turtleneck can become warm quickly on ascents and when breaking trail, a scarf or neck gaiter provides an easy-to-remove means of both covering the neck and closing the top hem of a top. A belt is the most effective means of cinching trouser tops, and is perfectly acceptable in tandem with suspenders regardless of what fashion mavens may proclaim.

Conclusion

While the combination of a merino baselayer with nylon outer garments will not meet every winter weather challenge it can prove a good system for those snowshoers who spend much of their winter time outdoors in relatively moderate conditions such as those found in southern New England. The various weights of merino baselayers on the market provide for some flexibility in insulation with the system, but do recognize its limitations and bring along a warm hat and jacket and a mylar blanket as well as navigation, first aid, communication, and fire-making essentials in a small day- or lumbar pack. It is winter, after all!




Notes

1. “Clothing materials,” vers. 4.8. Nov. 09, 2013. http://conovers.org/ftp/Clothing-Materials.pdf

2. “Comfort and moisture transport in lightweight wool and synthetic base layers.” BackpackingLight.com. Jul. 07, 2006. http://goo.gl/9KJBI.

3. Things to look for when purchasing a hooded garment include whether the hood is stowable (lest it become a reservoir for snow when not in use) and whether it incorporates a mean of cinching such as elastic or a toggled cord.

4. Things to look for when purchasing a hooded garment include whether the hood is stowable (lest it become a reservoir for snow when not in use) and whether it incorporates a mean of cinching such as elastic or a toggled cord.

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