How fishnet works (base layer fabric structures)

[Ryan Jordan]

Companion forum thread to: How fishnet works (base layer fabric structures)

This article explores how fishnet base layers offer superior moisture management and comfort for cold-weather backpacking by promoting rapid moisture vapor transport and minimizing condensation.

[Jerry Adams]

Good article, makes sense

One strategy is to have less insulation so you don’t sweat so much.  Take stuff off when you start getting warm.  Open front zipper.  If you start sweating slow down…

[Roger Caffin]

One strategy is to have less insulation so you don’t sweat so much
The common wisdom in Oz is to start out cold and to warm up as you go. This is the opposite. It works for us.

Cheers

[David D]

Yup, in summary, wool is a sponge.   Brynje was a game changer for me, getting the sweat off skin.

From the article:

“The larger holes of the fishnet serve another purpose – they allow for cool, dry air (e.g., from the outside environment) to be exchanged with warm, humid air next to the skin (through the bellows effect that occurs during movement). As a result, moisture vapor can be rapidly transported away from the skin surface, lowering humidity underneath and inside the base layer.”

I found an alternative approach more effective for me: layering a relative close fit Lifa polypro over the fishnet.  Water vapour gets transported into the Lifa layer so your skin stays dry, and it evaporates quickly because the Lifa is hydrophobic polypro.  The secondary benefit is that the Lifa keeps the air trapped in the fishnet cells warmer (slowing down the exchange for cold dry air) which helps create a strong vapour pressure difference driving the sweat through and out of the Lifa as well.

Another practical benefit of this that I’ve seen is the ability to use a lighter weight mid layer for the temps and so that hold less maximum moisture, making the over-all system even drier.

I gave this combo a lot of use last year snowshoeing and day hiking down to ~ -15C (it was a warm winter) and this was the best combo.

I really notice the reduced performance if instead I layer a looser fitting mid directly over the Brynje: drafty cold spots, longer time for sweat to come off my skin

 

[Mark Verber]

Thoughts on combining base and mid by using an alpha direct hoodie next to skin?

[Bill Budney]

Thoughts on combining base and mid by using an alpha direct hoodie next to skin?

That works for me, Mark. I wear a Brynje in the Winter for day hiking/snow shoeing/skiing under an Airmesh or AD (for simplicity, I am going to call them both, “AD”). I like it, but the difference between Brynje+AD vs just-AD is subtle.

I suspect, but have not tested, that Brynje’s effect may be more pronounced under a different kind of shirt, such as David’s example with Lifa, above. That makes sense to me. However, AD already has some of the benefit of Brynje built into its loose weave.

When counting grams for UL backpacking, I get most of the advantage of Brynje by wearing AD directly against the skin. Since the Brynje weighs slightly more than AD, it is (slightly) more weight-efficient to just use AD directly. YMMV.

[Terran Terran]

I think alpha tends to close itself off when its compressed under a second layer.

[Thom]

I’m not keen on the advertising on the neck band of the shirt. I’ll pass on it . I’m no one’s billboard.
Thom

[Mark Ferwerda]

Pretty easy to remove the tag…

[Justin H]

I put in ~20 days ski touring in fishnet last winter and I think it is amazing as part of a winter system. Ski touring sees a lot of temperature change and the fishnet combined with an easy to ventilate jacket was able to transition between warm and cold.

[Jon Fong / Flat Cat Gear]

I must be missing something.  The reason that you sweat is that your body senses a heat buildup and evaporation is going to bring your temperature down.  I thought that the whole winter strategy was to manage layers and to remove layers as you get warm (not hot).   The basic concept was to keep slightly cool all of the time which requires active layer management. I thought that there was an article posted about military training and how they managed to not soak their base layers and stay warm.  My 2 cents.

[Haakon R]

I don’t think you’re missing much at all, but everything that works out great in theory falls apart to some extent in real life.
Spending a winter day in the backcountry, heat generation and heat loss will change constantly with varying intensity and weather conditions, so unless one wants to bring a multitude of layers to accommodate any condition, and spend way too much time constantly adjusting layers – finding layers that are comfortable over a wider range and that handles moisture well for the unavoidable occasions when you get too hot, makes a lot of sense in  my experience.

 

[David D]

Haakon put it really well.

The other alternative is to slow waaay down at times as the Inuit do in the arctic.

That’s a non starter on most trips, unless any sweat build up could be dangerous such as deep winter multi-days without a hot tent.

[Haakon R]

I suspect, but have not tested, that Brynje’s effect may be more pronounced under a different kind of shirt, such as David’s example with Lifa, above. That makes sense to me. However, AD already has some of the benefit of Brynje built into its loose weave.

My access to AD garments is very limited, so I haven’t been able to do this kind of comparison. I have one AD full-zip sweater with 3 zip’ed pockets, stretch fleece panels and all that jazz, so it’s not particularly light as far as AD goes, and as such there’s not much to gain from using it as a combination layer.
My intuition have me believe that AD isn’t the best companion mid layer directly on top of a fish net base layer as I imagine the fussy inside of AD and similar fabrics will fill up the holes in the mesh to a larger degree than mid layers with a smoother inner surface, so I usually choose to go with regular fleece, lifa or wool over my Brynje. Basically ending up using my fish nets similar to David D, though more by my own logic and chance than actual trial and error.

With my limited experience with AD I might be wrong about this one, but I also have the impression AD is way more fragile than a Brynje base layer, so unless weight is very crucial I’d probably pick brynje + something else over just a single layer of AD in most cases. I have a couple of Brynje base layers that are coming up on 25 years of use and still going strong, and access is rather good here in Norway so I have no qualms putting wear on my Brynje garments.
I also suspect Terran Terran has a point about the properties of AD being more susceptible to degrade under the weight of other layers, backpacks etc.

I’d love to get my hands on some decent AD hoodies, but price and access being what it is, I’d probably “save” them for regular mid-layer purposes and not wear them out by using them as base layers

[Jon Fong / Flat Cat Gear]

I guess that what I am trying to get across is that layer management is a critical skill set to learn IF one wants to keep dry and comfortable as a trained Army Ranger. As I said, it’s a skill set just like tying knots, learning how to build an efficient fire and fishing. You get out what you put in. I would say that very few of us are super active in super cold climates and spend the time to develop these skills.

New fabrics and techniques may be able to expand the bandwidth of your layering system, but the fundamentals should still apply. If you are warm, you probably have too many layers on. If your clothes get wet, you’re probably not managing your system well. If I remember correctly, the Army Ranger Artic training is considered the most difficult skill to develop, much harder than desert and underwater training. My 2 cents.

[Bill Budney]

You will have to experiment for yourself, Haakon, but I like AD and Airmesh next to skin. As I mentioned in the same post that you clipped, Brynje does add a small benefit — it isn’t so much that AD compromises the mesh as AD is mesh itself, which is why it has some of the benefit of mesh without adding a dedicated mesh layer.

I don’t find durability to be an issue. Both Airmesh and AD will get slightly thinner with use, but that’s actually a good thing IMO. Both remain plenty strong and lofty enough to do the job. I do use two layers in cooler weather.

Regarding temperature control and moisture management, I agree with all of you, and will add that temperature makes a difference.

I can work pretty hard in freezing weather or somewhat below without approaching saturation of any layers. It’s a combination of factors: layers that move moisture outward, including a breathable wind shell, plus adjusting ventilation and layers to remain comfortably cool. I accumulate a little moisture in my layers at some points, but it will quickly cook away when I slow down. Half an hour after stopping I am completely dry.

I frequently use zippers and adjustments around head, neck, and wrists to adjust cooling. Yes, part of it is experience or skill or whatever you want to call it.

It’s more challenging in very cold weather when I am wearing more insulation that doesn’t breathe so well, especially when it is cold and windy enough that all skin must remain covered at all times. In those cases, it can be easier to adjust pace rather than fiddle with layering to maintain comfort and avoid saturating layers with sweat/condensation.

That doesn’t necessarily mean a slow pace — it means keeping the power output more or less consistent, including hills.

[David D]

Winter clothing management (real winter, not California) skills are (extremely) underserved from the experts.

Winter layering advice is also much more personal than 3 season: how much you sweat matters much more at -20C than +20C.

So, field testing is absolutely mandatory.

I came to the fishnet under Lifa as the best base combo (for me) after trying many combos over the years of:

• base: 100% wool of different gsm, smartwool intraknit, Lifa, Brynje net, poly/nylon (OR echo etc)
• mid: poly/nylon (mid weight hiking hoodie, hiking shirt, winter running tops…), octa, fleece (several kinds), nordic ski tops of 3 different weights with and without wind block fronts, 1/4 zip/half zip/full zip….
• Legs are much less an issue but need similar trial and error to dial in

They each of have pros and cons that need to be evaluated in person under real effort.

I arrived at different layering systems for every ~ 10C drop from 0C to -40C for each of head, hands, legs, trunk, arms, feet

This then gets tweaked based on wind and sun exposure and to a lesser extent the how technically difficult the travel will be, the latter because I prefer to just plow through and maintain a similar maximum effort regardless of the conditions.

Getting wet is unavoidable unless deciding to putter.  Managing it is critical.

A nerdy spreadsheet is mandatory to keep track of it all.

The repercussions are severe for getting this too wrong.

 

 

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