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Cuben / PrimaLoft One - Sleeping Bag
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Bill Fornshell
(bfornshell) - MLife

Locale: Southern Texas
Cuben / PrimaLoft One - Sleeping Bag on 01/22/2007 23:18:46 MST Print View

Cuben / PrimaLoft One - Sleeping Bag

Something happened this past week to cause me to re-look at some of the gear I planned to use on my up-coming hike. We had (for San Antonio) some very cold weather (down to 26 degrees) complete with a bad ice storm. On the good side it gave me a chance to try out some of my new MYOG stuff in the coldest weather so far this winter.

I was warm enough, but laying in my Bivy while it was raining ice pellets on my small Cuben tarp, gave me some time to re-think some of my gear.

Also last Saturday I received a VaprThrm NTS Shirt, VaprThrm Pants and a new pair of their VaprThrm Insulated Socks I had ordered this from RBH Designs. Over the last couple of days I have had a chance to wear the VB shirt and pants. I want to see at what "High" temperature they become to warm or cause to much sweat for ME to continue wearing them. Both the pants and shirt have the extra venting options. I have been surprised so far at the results. The temperatures for the 2 test have been 40 degrees and a light rain and 56 degrees and more or less clear. MY results might surprise you. The results of wearing the RBH VB shirt and pants are one of the big reasons I am re-thinking my winter gear list.

Back to the Sleeping Bag. I used Cuben fiber for the liner of a new Down quilt I have made. It uses Pertex Quantum for the outer shell. The combination of these two materials has worked well. Using Cuben for both the outer shell and the inter liner was next.

For my first of several Cuben Sleeping Bags I will use two layers of PrimaLoft One (pre-quilted) 1.8 ounce per sq yard insulation. The clo for PrimaLoft One is 0.84 and using two layer will give me a total clo of about 2.54.

I started by making several sleeping bag prototypes until I had one that I liked. This is my final prototype.

Next I made a full size pattern.

With a full size pattern cutting both the Cuben fiber and the insulation is easy. I expect to start sewing on Tuesday.

This picture shows how I overlapped the quilt seams.

Edited by bfornshell on 03/12/2012 13:46:41 MDT.

David Wills
(willspower3) - F
Cuben Bag on 01/23/2007 09:40:27 MST Print View

Very nice again, Bill. I love VB's in sub freezing weather. I am actually able to take my 1 layer XP quilt down to the high 20's with the use of a VB liner, the clothes I use to stay warm in those conditions and some golden grain. I never seriously considered VB's as permanent linings and/or shells for cold weather bags. I would love to see how the dual VB on the synthetic and down bags/quilts work. Especially concerning packing, unpacking and loft gain, if significant water can get in though the seams somehow, and if it is able to dry at all if that does happen. Eliminating the bivy will save you lots of weight and complexities too. I can't wait to see pics of your other stuff you've been working on.

Bill Fornshell
(bfornshell) - MLife

Locale: Southern Texas
Cuben / PrimaLoft One - Sleeping Bag on 01/23/2007 12:56:40 MST Print View

Hi David,

My Cuben/ Pertex Quantum Bivy only weighs 3 ounces, but 3 ounces is 3 ounces.

I have used VB's in my sleeping bags at low temperatures for a lot of years. Also in my boots and as mitt liners. The key is being able to control your sweat through venting and what you wear. It takes effort to make it work.

I am about to add the first of my comments about my new RBH Designs - Vapr NTS Shirt and Pants to my Winter AT Hike Thread.

I believe the VB idea can be used to a much higher temperature than most have thought in the past. It may not be for everyone but will be for those that are really in-tune with what their body is doing.

Eric Parsons
(EricP) - F

Locale: Alaska
intresting on 01/24/2007 13:08:30 MST Print View

Intresting system for sure. Since you are wearing all VB clothes are you using the cuben as liner material to only save weight then? It does not exactally sound comftorable (lots of crinkly plastic to sleep in...)
Cool idea!

Moe Dog
(moedog56) - F
Re: Cuben / PrimaLoft One - Sleeping Bag on 01/24/2007 14:39:50 MST Print View

Vapor barriers are sadly very under-rated and highly misunderstood. Nice to someone as yourself (who is very respected around here for your skill, creativity, and ingenuity at making gear) begin incorporating vapor barriers. It's such a simple way to add warmth while reducing weight, but such a difficult concept for most to learn/understand/accept and then use correctly.

mark henley
(flash582) - F
Re: Cuben Bag on 01/24/2007 18:55:47 MST Print View

Oh no David .... you're not getting away that easy ...

Details please .... what clothes are you wearing in the VP liner, what type of VP liner are you using .. what is "Golden Grains", beer or liquor? Do you sleep hot or cold? Able to take it into the high 20's, is that comfortably or just able to sleep for 3 hours at a time?

A normal 1 layer XP quilt should only be good down to about 60, mid 50's with heavy clothes. ... getting better than 30 degrees out of a VB liner is pretty significant and could change the direction of several projects I've been considering.

mark henley
(flash582) - F
Bill F. on 01/24/2007 18:56:46 MST Print View

Cutting edge once again Bill ..... good work.

David Wills
(willspower3) - F
Re: Re: Cuben Bag on 01/25/2007 07:12:59 MST Print View

"Oh no David .... you're not getting away that easy ..."

It surprised me too. When it gets below 40* when at camp, I carry a montbell thermawrap parka, thermasilk PJ's, 200 weight fleece pants, and polarguard 3D socks. My ex girlriends say I am like a furnace when I sleep, and my results with sleep gear seem to say the same thing. I made a VB liner from reflective silnylon, according to the gathered rantings on a previous VB discussion, the reflective aspect of it would only do any good in situations with inadequate insulation- 28* with 1 layer of XP. I sleep for 6-7 hours with the help of a few shots of goldengrain- grain alcohol, which thins the blood and gets it to hands, feet and face. It takes from your core temp, but thats only dangerous when it's 'survival' type cold. I wake up a bit chilled, but not to the point of severe discomfort. Always eat and drink plenty before bed, and stay out of the wind. The montbell thermawrap parka is the key item though. Its like a whole nother layer of insulation with a hood that stays put.

Just for reference, I can have a full night of comfy sleep at 45* with it and silk pj's.

Edited by willspower3 on 01/25/2007 08:57:34 MST.

mark henley
(flash582) - F
Re: Re: Re: Cuben Bag on 01/25/2007 08:16:20 MST Print View

Hummmm ...

OK ... I'm going to try this out.

I'm building a Forshell style Tunic quilt but with two layers of 3D. Finished weight I expect to be around 20 oz (I'm a big guy) but use with a VBL could very well take that quilt down (comfortably, although that seems to be a term to use with care here) to 20. My Heatsheets bivy (planning on using as a Vapor Barrier Liner) is 3.25 oz.

Assuming all other items remain constant:

Quilt/Tunic = 20 oz
Vapor Barrier Liner = 3.25 oz
Light insulated Vest to hike in/extra insulation = 6 oz.
Capilene silk weight bottoms = 6 oz
total = 35.25oz

30 degree bag = 24 oz
bivy = 7 oz
Insulated pullover = 14 oz
Total = 45 oz


Vapor Barrier Down Sleeping bag (1.75 inch loft with empty down panel on bottom)(estimated) = 16 oz
Insulated vest to hike in/sleep in/hang out in camp = 6 oz
(use VPSleeping Bag as additional insulation in camp)
Capilene silk weight bottoms = 6 oz

Total = 28 oz.

Having a guy like Bill Forshell, and all the others on BPL, around to spark so many great ideas .... Priceless. (Weightless?)

Eric Parsons
(EricP) - F

Locale: Alaska
bozzin in on 01/26/2007 13:41:19 MST Print View

"I sleep for 6-7 hours with the help of a few shots of goldengrain- grain alcohol, which thins the blood and gets it to hands, feet and face"

Do you wake up cold and Hungover as well??

Bill Fornshell
(bfornshell) - MLife

Locale: Southern Texas
Cuben / PrimaLoft One - Sleeping Bag on 01/27/2007 23:58:21 MST Print View

I think I can say I am finished with my Cuben - PrimaLoft One / Sleeping Bag.

The bag is made out of all Cuben Fiber. The bag in its present size is 19.08 ounces. I say present size since when making it I added some extra length to it. When I made my last prototype I lost some of its length. The non-insulated insert for the bottom is tapered and when I sewed it to the rest of the bag the taper pulled in the sides and made it shorter. I added 10 inches to the length just to make sure it wasn't short. The current length is 89 inches. I will decide how long I want it but I am thinking about 80 inches. When I do this I think the weight will go down to 18 ounces.

The bag uses two layers PrimaLoft One (Clo of 0.84) 1.8 ounce per sq yard pre-quilted insulation in the main bag. This gives me a total Clo of 3.02. I made a small hood for the bag that uses 3 layers of the same insulation. I also made a neck yoke and used 4 layers of insulation in it. I have elastic in both the hood and the opening of the bag. The bag is made to slide into. The circumference of the top part of the bag will open to 64 inches. The foot end (if cut at 80") will be 38 inches. The insulation is stabilized to the inter piece of Cuben so the shell has no seam lines to leak.


Hood and Non-Insulated Bottom

Finished - Sleeping Bag after trying it out. The sleeping bag is made of 2 layers of PrimaLoft One - 1.8 ounce per sq yard pre-quilted insulation. The bag part has a total Clo of 3.02.

"Edited" Rolled up for packing.

Detail of Neck Yoke and Hood. The Neck Yoke is 4 layers (Clo of 6.04) and the Hood is 3 layers (Clo of 4.53) of PrimaLoft One - 1.8 ounce per sq yard pre-quilted.

Edited by bfornshell on 01/28/2007 15:53:38 MST.

David Wills
(willspower3) - F
Re: bozzin in on 01/28/2007 17:03:19 MST Print View

Do you wake up cold and Hungover as well??

I don't get slammed... usually. A little nip of alcohol just helps keep the extremities warm. A large nip makes you forget where you are, but can cause lots of lost core heat. I'm pretty used to a slight chill. It goes away after I get up and moving. Hydration prevents hangovers. Low standards for comfort help too.

That sleeping bag looks awesome. Draft collar and a hood is a great touch. How do you think it will handle stuffing?

Edited by willspower3 on 01/28/2007 17:06:25 MST.

Bill Fornshell
(bfornshell) - MLife

Locale: Southern Texas
Cuben / PrimaLoft One - Sleeping Bag on 01/28/2007 17:16:07 MST Print View


I have rolled it tight 3 times so far. It just puffs back up. I need to get it 13.5" by 6.5" to fit nice in my pack.

I will roll and unroll it each day and see what happens. This stuff is supposed to be beyond compression problems. Time will tell.

Evgeniy Lev
(Jonyk) - F
Some questions... on 01/30/2007 08:35:15 MST Print View

Bill, if it's possible, send me your mail on
I cannot contact with you through PM.

Aaron Sorensen
(awsorensen) - MLife

Locale: South of Forester Pass
Re: Cuben / PrimaLoft One - Sleeping Bag on 02/05/2007 22:54:05 MST Print View

Bill changed it back. I had the same problem when I wanted to send him something.

I have to commit one more time on this bag.
This the first bag I have seen with the Cuben used inside and out.
Although I think it has it's usage, the one I'm mostly thinking of is that it resembles an alien space-craft and you fly around in it.

Just watch out while you're flying around with that kilt on.

Edited by awsorensen on 02/05/2007 22:54:57 MST.