A good alternative to WPB gear for ACTIVE backpacking

[Richard Nisley]

Stumpghes,

You asked, “What would be the minimum permeability needed with ventilated/no backpack and two pit zips open?”

In Will R.s part II testing he clearly concluded that the benefit was marginal.

[Richard Nisley]

Daryl & Daryl,

You said, “But this non-waterproof  outer shell will let in rain, right? Haven’t I just traded one problem for another? In either case I’m wet.”

If you wear a moisture wicking base layer like a Cap 4 or R1, under a windshirt that has >300 mm HH, the moisture that gets driven out of the ensemble is larger than the moisture that enters it at high MET rates (7 for backpacking). As a result, you will be drier inside than if you wore an eVent WPB in the same scenario.

Reread Will R.’s report Part II Here and then ask yourself if there is an alternative that would be more comfortable?

[Richard Nisley]

Eric,

You said, “if youre going to do the non WPB shell method … a FUZZY and FLUFFY fleece is best … something like a polartech thermal pro … and yes you will get somewhat wet either way …”

The Natick Labs research came to a different conclusion but who knows, they may be all wet (smile). To refresh you memory on what Natick Labs recommends reference the article Here Specifically look at ” In testing the system, users are encouraged to get wet before starting, in order to see just how quickly water is forced out of the system. After submerging the system, the wearer engages in movement on land, which results in the next-to-skin clothing being dry in about 15 minutes and the entire clothing system being dry within 60 minutes.”

The time to dry the Polartec Power Dry base layer, worst case, is about 15 minutes. Power Dry is engineered to transport water in the liquid form away from your body. It accomplishes this by capillary action between you skin and the bi-component fabric surface. Second, it spreads out the liquid moisture over a wide surface, insulated from the skin, to then transport the water further away in vapor form. Thermal Pro is an insulation layer that is engineered to pass moisture in vapor form. 

Why does Natick want to move liquid water between your skin and the Power Dry base instead of vapor water? Liquid water occupies so much less space than vapor water.  Fully water saturated air, at 68F (20 C), contains less than 1/70,000 of the amount of water than the same volume of liquid water. Therefore, if you want to move water quickly, moving it as a liquid is more efficient than moving it as vapor. In addition, converting it to vapor adjacent to you skin, further cools down your skin temperature.

 

[Dave B]

So, what are you wearing in the rain while backpacking, Richard?

Dave B

[James holden]

richard ..

i can tell you that when i use cap4 (or T2) in the rain under a windshirt … if its still raining i stay wet .. and if its cold i stay cold

when its constantly raining, even with a windshirt …. everything is soaked …

did em army folks do their test under a shower head …. or did they submerge then start moving in dry air? … interestingly enough they issue a nice warm fuzzy thermal pro sweater as well …

how does a totally saturated powerdry, which is still being ssaturated by water ingress, wick … ive never understood that process

either way its and easy test for folks here since we have early season temps at night… next time it rains heavily simply jump in the cold shower and walk around town for an hour or two … try it one night with a cap4 + windshirt …. and another with a fuzzy fleece + windshirt … do this while its still raining heavily (you want to see how it does in the rain, not the dry)

make sure you bring a good warm synthetic poofay in a pack so you dont go hypothermic

;)

[Richard Nisley]

Greg F,,

You said, “From a heat transfer perspective aren’t you better off keeping the cold water on the outside and the warm sweat on the inside? im think the warm water that get pushed out from inside and the cold water being leaked in creates more heat loss than forcing the heat to transfer across the WPB layer.”

You brain wants to keep your skin temperature at an average of about 95F. It generates sweat once it rises to about 97F. The sweat needs to evaporate from your system to keep your skin at approximately 95F. At 7 MET you are generating so much heat, that the small amount of water that leaks through a >300mm HH outer is evaporated before it reaches your skin to uncomfortably cool you.

[Richard Nisley]

Dave B.,

If I am backpacking with bushwhacking, I wear my 2010 ORC PCU L4 over a Cap 4. The DWR never needs to be replenished and after 7 years of use it still tests 3.7 CFM and 492 mm HH.

For rainwear while doing more civilized endeavors, without a pack, I wear one of my many eVent jackets with a regular shirt under it.

[Greg F]

At what external temperature is the 300mm the optimal waterproofness.  Is in entirely dependant on MET and permeability so external temp doesn’t matter?

 

As an aside this does seem to support the umbrella/windshirt model

[Richard Nisley]

Eric,

The system relies on the conjunction of viable DWR AND >300mm HH AND Polartec Power Dry base AND a MET near 7. The US Special Forces have been using this system for 15 years. The relevant question isn’t “Does it work?”, rather, “Is it possible to create an UL Backpacking corollary?”

[James holden]

richard …

last year a fellow BPL member from US SFs actually said he doesnt know anyone who uses the windshirt !!!

https://backpackinglight.com/forums/topic/best-insulation-system-for-cold-rainy-mountains/page/2/#post-3393715

he also gives a great explanation of his usage of said systems earlier in the thread

regardless …  there also the issue that the DWR on most windshirts folks on BPL use is NOT epic or such …. but rather normal flurocarbon or wax based DWR that wears off, more with higher abrasive use …

sure you can refresh it but sooner or later when the fabrics worn enough it wont matter …. nor can we easily refresh it with a dryer when out

;)

 

[Richard Nisley]

Greg F.,

You said, ” At what external temperature is the 300mm the optimal waterproofness.  Is in entirely dependant on MET and permeability so external temp doesn’t matter? As an aside this does seem to support the umbrella/windshirt model?”

300 mm HH is the minimum for this system to work independent of the temperature. It is about what the original Pertex 5 and 6 fabrics provided when Buffalo launched the concept in the UK. Lots of fabrics are available that will achieve >300mm HH but they achieve this at an average of only about 3.5 CFM. This is 7x better breathability than eVent but still not enough for very warm temps. Very warm temps require about 25 CFM. That type of fabric is available but not common.

[Richard Nisley]

Eric,

Kris used his Level 5 instead of his Level 4 for the temperature range that Natick suggests for the Level 4 as well as the normal Level 5 recommended temperature range. Level 5 is still 750% more breathable than the best WPB available. Level 5 has a nicer hood, pockets, stretch, better durability, and is tailored nicer. If I wasn’t worried about a few oz., I would probably do the same (smile).

He also said his favorite garment was his PCU L3A. Natick has not released the specs for this garment but I measured one in my lab. at 35 CFM and 300mm HH. I sent him a personal email with my test results but I didn’t receive a reply.

For your personal test you can get a current model version of the Patagonia Houdini or a Level 5 for about the same price. The HH and CFM ratings are also about the same. The weight difference is dramatic.

[Bradley Danyluk]

I posted about this earlier in the thread but it seems to have disappeared.
It looks like 0.9oz Argon fabric (like Luke’s Ultralight windshirt) to be a near ideal choice for this use.

352mm HH and 40.1 CFM As per your previous testing, Richard: https://backpackinglight.com/forums/topic/100458/

Am I correct?

I also just want to share a bit of a contrary view of Thermal Pro as being an ideal insulation underneath. In my personal testing, I’ve found high-loft Thermal Pro to not behave nearly as well when truly wet as 200 or 300 Polartec Classic fleece. Classic can be completely soaked and will *feel* dry and warm nearly instantly, even against the skin. Thermal Pro, in my experience, tends to turn into a heavy sopping mop, lays down flat when wet and hence sucks the heat out of you until it dries to merely “damp” (which can take a lot longer than with Classic, and doesn’t seem to be achieved by merely wringing it out). Classic seems to maintain its structure/trapped-air even when completely soaked, and thus feels warmer.

[James holden]

thanks richard

im not doubting that the general system “works” … however i will tell you i get cold in a cap4/t2 in the rain should it get wet around freezing …. whether under a windshirt or a rain jacket

fuzzy fleece … not a problem at all … especially if water is still ingressing through the windshirt (not many windshirt have as good cuffs, hems and hoods as a good rain jacket

are we accounting for physiolgical differences here …  a 5′ 100 lb woman would have quite a different heat output than a well trained and big 200 lb navy seal (ork ork ork) hauling a full load

is the new houdini EPIC … or flurocarbon?

i think that anyone who uses their flurocarbon or wax windshirts should not count on their DWR being good in a heavy rain if they wear it all the time …

this is for WPB, but i expect one will see a similar trend for windshirt florocarbon and wax DWRs … especially as this test was done when c8 was still legal ;)

 

[Richard Nisley]

Bradley,

That is a great windshirt choice.

[Richard Nisley]

Eric,

The bottom of the PCU guide has a black outlined summary which says, in part, “Each individual physiology is unique. This user guide is intended as baseline guidance for the PCU system.” A major determination of what I require is my MET rate. When I am trying to keep up with my adventure group I am at my limit of endurance and need about the amount of insulation that Natick Labs specifies. This winter I spent a month bushwhacking with a buddy in temps down to -8F. Our MET rate was lower than my adventure group’s; I required a L3 to stay comfortable starting at about 30F.

Good question regarding the current Houdini.I have one but haven’t tested the DWR to see what they used. I will try and investigate that in the next few days. Your point is well taken that C6 is worse than C8 and C8 wasn’t great to begin with.

[Iago Vazquez]

Thank you all for the discussion. I understand that wet does not necessarily mean cold, as I hear is the case with wetsuits. As you know, people with limited experience outdoors would cringe if told to try the windshirt/fuzzy combo. I have been wet and warm before, and the concept never worried me from the first time it was suggested to me. In my limited experience trekking in the rain, nothing seems to beat a WPnonB poncho over a windshirt. If more warmth is needed, then a classic or fuzzy fleece seems to do. Stick the sleeves off the sides and if they get cold, tuck back in for a few minutes. If I am steaming inside, give it a couple of shakes to get some air going through it, and I recover comfort. With the plus that my pack remains dry, it’s easier to put clothes on and off and map consultations are easier. If the wind is relatively calm, they are my preferred choice. My worst day in a poncho was probably trekking in April through Shenandoah in about 35-40 degrees with 15-20 mph winds or so. And we stayed warm the whole day.

I have dealt with plenty of windy treks, but I admit that I have been lucky and never dealt with serious rain coupled with very strong winds, at which point, the poncho may be acting like a sail and start being problematic. I always wonder how I should handle those scenarios when they occur. That day in Shenandoah, the wind simply wrapped the poncho around our bodies, and was not much of a nuisance. I have heard of people tying off the waist, but in Shenandoah that day I never tied it up, and only when we got hit with some gusts, I simply grabbed the poncho with my hands so it wouldn’t fly up. I seem to remember at one point we had to hold them for a while, but mostly the wind just wrapped it around us. I was afraid that tying would significantly reduce the ventilation effect, and that it would be more of a hassle. Although a bungee cord and a biner may make quick ventilation maneuvers easy… From reading this article, it seems like if I am wearing a windshirt with a good DWR and the right mix of synthetics under for the expected temperatures, that may be a better approach than tying the waist of the poncho if the wind makes it problematic.

[Jerry Adams]

Interesting info here from everyone, thanks

if you want UL, you should have something like Apex rather than fleece, warmer for the same weight

I wonder how that would work in this system.  Like you could just use Argon (or whatever) as the outside shell fabric.  2.5 oz/yd2 Apex for example, or do they make anything lighter…

[Mike M]

Richard- have you put the BD Alpine Start under the microscope by chance?  it boasts an ~ 300mm HH and  ~ 35 cfm; what is more impressive yet is that the “DWR” lasts and lasts- it’s Schoeller Nanosphere- it acts very much like an encapsulated “epic” style fabric, but unsure if that’s the actual case

it’s double the weight of my older Houdini’s, but the fabric is more robust when venturing off the trail

 

Mike

[Daryl and Daryl]

Richard,

Thanks for all the info and your patience with our questions.

“If you wear a moisture wicking base layer like a Cap 4 or R1, over a windshirt”

Am I reading this line correctly?  Are you describing the wearing of a base layer on the outside of a windshirt?  Would a second base layer then be worn on the inside of the windshirt?

 

[Mike M]

I’m 100% certain it’s under the windshirt, not over :)

in regards to Apex- great insulation that is less susceptible to moisture than down or other syns, but will still lose it’s loft nonetheless if it gets wet, I think fleece does a better job and can even be hand wrung out to near dry if need be

I do think a light Apex jacket or vest would be a great layer in addition to the fleece layer for stops (and if raining under your WPB jacket)

[Jerry Adams]

I’ve got Apex totally wet, as in put in tray of water for a while, didn’t lose any measurable loft

If you get it totally wet compared to fleece, Apex will have a lower percentage of it’s weight of added water

Since it’s 4 x warmer for the weight than fleece, it’ll still be better

Yet I agree fleece is better if you don’t care about the weight.  And Apex can be too warm so you’ll sweat.

[Daryl and Daryl]

Jerry,

In my at-home tests, fiberfill (sandwiched between two layers of nylon) will also dry faster than fleece. .

[Ken Larson]

What speed in MPH do you need to travel to generate 7 MET when backpacking?

[Mike M]

I’ve got Apex totally wet, as in put in tray of water for a while, didn’t lose any measurable loft

If you get it totally wet compared to fleece, Apex will have a lower percentage of it’s weight of added water

Since it’s 4 x warmer for the weight than fleece, it’ll still be better

Yet I agree fleece is better if you don’t care about the weight.  And Apex can be too warm so you’ll sweat.

 

Jerry,

In my at-home tests, fiberfill (sandwiched between two layers of nylon) will also dry faster than fleece. .

 

Did not know it was that resistant to moisture (or the ability to dry that quick), even more reason I should like my new jacket from Nunatuk! :)

 

 

 

 

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