I love sleeping under a quilt inside a bivy bag! I have read that 4 inches of loft is needed for a 0 degree rating. But at some temperature would a quilt reach a point of diminishing return? At what temperature does a quilt no longer make sense? Does the top bag start where the quilt leaves off?

Even though I love Bill Fornshell’s Sleeping Bag designs, I don’t know if I could sleep in something so narrow without a zipper. How much would the design suffer if the sleeping bag were made wider and with a zipper?

I purchased some Momentum90 some Cuben and 8 yards of Climashield XP 5 oz/sq yd. 1.2 inches of loft per layer clo=.82/oz. How many layers for a 0 degree quilt? Do I make it wider to tuck the edges under? Which quilt would you copy?

I know Ray and Jenny Jardine skied to the South Pole last winter using a 2 person quilt with 2 layers of .9" Polarguard 3d. I made a one person RJ bag with the same insulation and it is about a 30 degree bag.... of course they also had lots of insulated clothing, and they are nuts...

My down quilt has 15 oz of 800 fill for about 3 inches of loft (depending on the baffle, thanks to my DIY inaccuracy) and is warm into the teens with a few layers on.

For a colder quilt, you will probably want it wider to tuck in and fit more layers, and your wet shoes, and water,... and have a good insulated hood to use with it.

Hey Robert,
I am in the same process you are making a 0* quilt but with Momentum and down.
Acye says that the XP 5 ounce is good to 20*, although I can't imagine that being that warm of a 20*.

If you were to find the loft difference between a 20* and a 0* bag you can just do the math to see what you need for the 0*.

I am going for a 2 lb quilt to reach 0*.
The Momentum came to 10.8 ounces so I get 21.2 ounces of down that will give me right around 4.5" of loft.

Robert,
I've been trolling the MYOG forum to find loft/ clo information and conversions. Could you point a guy in the right direction?
Matt

Hi Aaron,

I have two pieces of insulation for new sleeping bags. One is 3 yards of 5 ounce XP and the other is 3 yards of 4.7 ounce Combat.

I am going to make sleeping bags (no insulation in the bottom) out of 0.57 ounce per sq yard silk for the shell. By using my insulating garments and patagonia #2 merino wool underwear to sleep in and / or other things I will be carrying, I believe both of these sleeping bags / systems will be good to "0" or lower. They will be used inside my 4 ounce bivy along with my Warmlite Down Air Mattress. My planning weight for the bags is from 16 to 20 ounces each bag.

Using the synthetic insulation I will save the material weight that is necessary for the Down baffles. By using Pertex Quantum as the outer shell on my Bivy I can use the light silk for the sleeping bag shell which saves more weight.

The way I make my "slide into" sleeping bags is with a bit wider opening. This makes getting into and out easy even when I am using my hammock.

Edited by bfornshell on 10/12/2007 11:10:30 MDT.

Hi Aaron,
I bet your 0 degree down quilt will be warmer than my 0 degree Climashield quilt!
It seems that one of the great advantages of a quilt system is the ability to layer without compressing your insulation. I will probably wind up using 3 layers of the 5 oz XP and Momentium. After all, this will be my winter quilt.
Bill, I see that you make your sleeping bags with a wider opening so that you can slide into. Correct me if I'm wrong, but didn't you start with quilts and then gravitate to top bags? Is the bottom of your bags only for draft control? I do want you say that you are the inspiration that has started me on the golden path of making my own gear.

Matt, I can't seem to locate that darn Loft chart. Here are a few links that may help you out.

http://www.backpackinglight.com/cgi-bin/backpackinglight/2006_unconventional_sleep_systems_manifesto.html

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=9637&startat=60

Thank you Sir.

Hi Robert,

Some time ago I was in a discussion with Robert Van Peski about the Down Sleeping Bags they sell. We were talking about Down vs Synthetic insulation. I was playing around with the numbers for the weight of an XP or Combat quilt vs his sleeping bag. That is when I realized his bag was a Top bag type - non insulated bottom. I decide to try that and did some numbers using Pertex Quantum for the shell and Cuben for the non insulated bottom. Then I went to light silk for the shell and Cuben for the non insulated bottom. I ended up making one of Pertex Quantum and one of light silk both using Cuben for the bottom. I sent them both to someone up in New England to play with this winter.

You are correct that the non insulated bottom is almost all for draft control. It also helps control the material if I use it in my hammock which I guess is still draft control.

After making my first Cuben bottom sleeping bag and seeing the really small amount of extra weight the Cuben bottom added, I have not gone back to the Quilt if the temperatures are going down below 40 degrees or so. I have used my one layer Combat quilt down to 42 degrees inside my Bivy and was fine. That quilt clips into the inside of the Bivy for a bit of control.

I don't understand why you need 3 layers of 5 ounce XP to get to "O" degrees F. What are you using for a sleeping pad? If your pad doesn't provide enough insulation the cold ground will suck the heat away from you fast.

Bill,
The only reason for 3 layers of XP: 1.2"X3= 3.6" of loft.
I am a side sleeper. A few years ago I purchased a Golite quilt. I really liked using the quilt. I did, however, get cold every time I turned over. Then I tried it in a large bivy and bingo – I had my system! After reading almost every post in MYOG I started buying the material. Not so much to go sub 2lb, but to use state of the art materials to make the gear ultra-lite and a little larger for my sleep habits.
I love the Cuben. I have done a lot of tests with the Cuben as well as built a simple tarp using the IBM Tape. I took pictures and will post how I used the tape in your Cuben thread at a future date. I have enough Cuben left for the Momentum/Cuben bivy. Later I hope to construct a pyramid style structure with it. Cuben is really the way to go for a lot structural applications.
I suspect silk is a better way to go for the quilt – since your using it. I already have the momentum90, so that’s what I use for this Quilt.
How many layers of XP would you use for a 0 degree quilt?
Robert

Robert,

I go by the rule that the CLO number is to Synthetic insulation as inches of loft is to Down.

Your 3 layers of 5 ounce XP, by my thinking, gives you a total CLO of 12 or so. In my way of thinking that is more or less equal to 12" of loft for Down. Think about sleeping under a Down quilt with 12" of loft on top of you.

My "0" degree XP and Combat sleeping bags will each use 1 layer of 5/4.7 ounce insulation. At "0" or so I would be wearing my Cuben VB pants, shirt, and booties. Over that I would have on my Patagonia #2 wool pants, short neck zip hoodie, a pair of silk-weight glove liners, one pair of my hiking socks and if necessary a set of silk insulated pants, shirt/jacket, and maybe my Combat footies. This is about what I would be carrying and I still have my silk insulated vest and rain gear to put on if necessary. I will be sleeping on my Warmlite Down Air Mattress which goes into my Bivy.

When it is 20 degrees or less the Cuben VB stuff stays on all the time and can be vented as necessary during the day while hiking. The silk insulated items can be worn, vented, or removed if I get to warm. One of these days I am going to make a set of pants and shirt / jacket out of Pertex Shield to wear as my outer garment to cover the Cuben VB stuff. This is a new WPB material from Pertex. I only have a 3 yard sample of it so I need to be sure to use it to it best advantage. I can get more but only in amounts of 550 yards. The Pertex Shield items will also be my rain wear. The Pertex Shield material weights about 1.9 ounces per sq yard so it will be no zippers (snaps) and close fit.

Bill,

I always enjoy reading your thoughts.

I don't have such a well designed system as yours.

Wearing just my hiking shorts, one pair of socks, tee shirt and a patgonia micropuff vest to bed I don't have nearly the same thermal efficiency as your system does .... and a quilt is not nearly as good as your bag design at retaining heat.

For me, and I sleep a bit warm, with the above sleeping setup and a simple 3 yard quilt, I've found the following rough formula relating clo to temperature. Of course ... this would change for everyone depending on their sleeping habits.

Temperature rating = 60 - (clo x 8.2)

So ... for a CLO of 3.4 I get about 32 degrees. To get to Zero, this would suggest that I would need a quilt with a CLO of about 7. Your multiplier would be much higher than 8.2 given your system ... I can't even guess how high.

This should well illustrate the differences in efficency between a simple quilt and an efficent bag design and just how much impact your clothing system can have on the amount of insulation you need to carry.

With a better design, say like your bag design, and a better clothing system, I'm sure I can get that down to 6 or perhaps even 5.

I've just GOT to make myself a pair of those cuben booties!

Thanks Guys!
I finally understand CLO.
Bill, what is “5/4.7 ounce insulation”? From Mark Henley’s post, I see that your sleeping bag design is WAY more effective than a quilt.

Mark, thank you for sharing your formula for Temperature rating. So, if I used 2 layers of 5oz XP the rating for a warm sleeper with a good mat would be approx. -7 degrees F. Now I have enough XP to make 2 bags!

Hi Mark,

Thanks for the nice comments.

I have been a member here almost from day one. About day 10 or close I think.

In the beginning I read everything posted, all the articles on reducing gear weigh, lots of gear lists and what I would call Ryan's "system" theory.

I kept an open mind and tried lots of different things with the gear I owned at that time. My gear back then was sort of light but was nowhere near an effective system. It was just a lot of really good "individual" pieces of gear but when put into my pack, was heavy pack.

I found out fast that if I could build and sew some of my own gear I could drop a lot of weight in a hurry. I tried a lot of different ideas and material. Some things worked and some didn't. What I was trying for was a (SUL) set of gear that all worked together. This came in part from Ryan's idea for his "Cocoon" gear line and my idea to use my insulation for more than one item. The Cocoon System, as I understood it, was laying to the highest degree. The sleeping system worked with the other garments being carried/worn to help keep you warm at night. If you are carrying it why not sleep in it and reduce the weight of the sleeping bag or quilt that you are using. I also would add that "for me" I need a good insulated sleeping pad as the temperature gets below about 20 degrees F or so. My Warmlite Down Air Mattress solves this problem. I went with the Warmlite DAM after trying the Exped.

At the same time I was also playing with being able to use a (light weight) hammock system that would keep me warm down to "0" degrees if I wanted.

This was not a real fast process. We are all different in what it takes to keep us warm and we only find that our by trying a lot of things.

I am not yet where I want to go with all of this.

PS. Contact David Olsen and get some of his scrap Cuben for your booties and other small items. You can't beat the price.

Owareusa

Robert

The 5 is for 5 ounces per sq yard, the weight of 1 layer the XP. The 4.7 is for 4.7 ounces per sq yard the weight of 1 layer of the Combat. These numbers are a "production standard" but can average a little higher or a little lower. That number is what you multiply by the CLO number to give you an idea of how much Down loft it should be equal to. So at 5 oz x 1 layer x 0.82 (the CLO of XP) = 4.1. If you use more than one layer it would be the total weigh per sq yard of all the layers. If you used 3 layers it would be 5 oz x 3 layers x 0.82 = 12.3. For me this is a good planning number to see how much Down it should be about equal to. So a CLO of 4.1 (1 layer of 5 oz XP) is (more or less) = to a Down loft of 4.1 inches.

Having said all of that, other things factor into just how warm this all might be. The Down has to be good stuff and how and what material used and the design used, also play a big part in how warm what ever you have made will be.

Alright,
I thought this post would just die off like it seems all good posts have been lately.

I've finished my 2lb quilt and it is sweet! It has just under 4 3/4" of loft and is very very warm.
Even with it's quilt design for varying temps, it is way to warm to be used unless the temp was under 32.

Bill,
I would like to have someone with your 5oz/yard top bag do a comparison with them and maybe with a store brand 0* bag as well.

I would like to think I could stay warm in the bag down to 5-10*, but I am a really cold sleeper. My 15* TNF Hightail only keeps me warm to about 30*.

I will get some pics posted soon.

Where are those pics, man? I really want to see the loft on this thing! No rush, no rush...

Alright,
I'll be using the quilt over the next few days and get a few pictures of it in use.

I'll probably end up dieing of heat exhaustion in it with low temps being in the low to mid 40's.

The max upper comfort limit of this bag is probably about 35*.

Aaron, I am interested to see how it went with your Momentum Quilt. I plan to make a dual quilt for my wife and I. I want to stay under 2lb, rated 0-10 degF. What dimensions am I looking at? We are both small (5'4"). She is a cold sleeper where as I am warm. Thanks, Shah

Hey Shah,
I just got back from using the quilt and it worked amazing.
I am not sure on your size for a dual.
I use a very generous size because I am a cold sleeper and think sleeping bag ratings are garbage, (because I'm a cold sleeper). I was planning on some in use pictures but the camera got wet and is toast.
I have some others and will get them posted after this weekend.

I would look at what dimensions Jardine has and cut down to your size from there. If you have a 75" wide quilt, you may be able to 3 3/4" of single loft. With the two of you, it should work out fine. You can always wear more clothing inside to stay warm.

> I plan to make a dual quilt for my wife and I. I want to stay under 2lb, rated 0-10 degF.
A bit difficult.

I made our double quilt:
Pertex Microlight, 300 grams (10.58 oz) for the shell. It used most of the width of the Pertex, which is about 54 inches wide as I remember it, but it was tapered down to about 41 inches at the foot.
800 loft down, 600 grams (21.2 oz)
Total weight about 900 grams (31.7 oz).
My wife and I wear thermals in bed in the winter. We used this quilt OVER our summer bags/quilts which have 300 grams of 800 loft down in them, and we were quite warm at some degrees (Centigrade) below freezing. But of course we were snuggled up.

Now, asking a 2lb quilt to get you to 10 F - that is pushing too hard imho unless you are also wearing Cocoons (top and pants) or similar in bed.

Cheers