I am hoping some of you can help me out with a bag layering question.

I have had several people tell me that I should look at using an over bag or a quilt to increase my current bags rating. I was looking at using the following two bags for winter backpacking:

Big Agnes Yampa (10.5 oz. of 850 goose down)
MontBell UL Stretch Down Hugger #3 (11 oz. of 800 goose down).

The Big Agnes website generously states that the Yampa with add 25 degrees to your base bag. I know this is simply a general temperature rating but I wanted to get other peoples options on the matter.

Question #1
How accurate do you think BA claim of adding 25 degrees is? I am a bit skeptical of the claim due to the following;

1. The UL #3 has no draft collar
2. The Yamp has no hood.
3. Will 21.5 oz. of down really keep me warm down to 5 degrees?

I know that one of the best ways to gauge a bags temperature rating is by measuring the weight or thickness of the down in the bag. Unfortunately I cannot seem to find the figures detail the general weight / thickness to temperature ratings.

Question #2
Could someone please point in the right direction for data on thickness / weight of down compared to temperature ratings?

I have no experience with the Big Agnes mentioned.
The JRB website shows these temperature ratings with their respective inches of loft:
Comfort Rating (°F) = Loft (inches)
40 = 1.5
30 = 2.0
20 = 2.5
10 = 3.25
0 = 4.0

How it helps. I use a quilt to augment my 0* bag but haven't gotten scientific about it yet.

Edited by toesnorth on 11/13/2007 08:43:13 MST.

while I can't comment on the gear you mentioned here is my experience with several down bags (800 to 850 fill) and a range of ratings between -7ºC to -10ºC. I find that the bags get too cool and that the ratings would be more accurate as -5ºC to -8ºC.

Keep in mind that everyone is a little different and that women tend to need more warmth in some areas than men. This is just my take on it.

This said I have a synthetic and down combination bag from Marmot I think (I'd have to go look). While it doesn't pack as light or compact - I find the temperature rating on it much more accurate.

My concern when layering is that the overbag is wide enough to reach the ground on both sides and that the inside bag will not be compressed by the overbag.

I have a Big Agnes Cross Mountain and it does compress the inside bag. I wear a 48" regular coat.

The draft collar and hood do not work well for side sleepers. I prefer a balaclava.

Thanks for the information so far.

The Yampa is suppose to be intended as an over bag. It has the standard BA design where you slide the sleeping pad into a sleeve on the bottom of the bag.

The Yampas bags dimensions are pretty big, 73inch; shoulder girth, 69 inch; hip/ foot girth.

The MontBell bag dimensions are shoulder girth of 56-75 inches and knee girth of 47-63 inches.

Edited by chadnsc on 11/13/2007 10:52:08 MST.

Chad,

I'm glad you started this thread. I have been contemplating a similar move but, with a different approach (though not necessarily better).

I have a Western Mountaineering MegaLite 30'F bag and my tentative plan is to buy a Montbell UL SuperStretch 0'F bag and put the WM bag inside the Montbell to make a sub-zero bag. That would give me quite a range of temps using combinations of just 2 bags.

My theory (hope) is that the Montbell will both expand large enough to not compress the WM bag but at the same time, have enought tension to eliminate the air space between the bags.

Anyone tried this approach?

I also am very interested in this two-bag approach. My basic bag has been a Montbell UL SS Down Hugger #3 (32 deg) bag that I've used primarily as a quilt this year so far. I thought that a synthetic quilt would be the ticket for an overbag so ordered the Cocoon Pro 90 quilt. No go (see my review) as it's just way too small to function as an overbag over any reasonable 3-season bag. The new MLD XP Quilt looks like it might be the ideal overbag while still being light enough by itself for summer conditions but I hesitate to spend that much money without confidence that it will work.

As far as doubling two sleeping bags for winter, does anyone know how a lighter bag such as a Montbell UL Alpine Burrow bag #7 will work inside the Super Stretch Down Hugger #3? I am assuming that the stretch system will expand to handle the inner bag but have no experience yet trying this. Unfortunately, this particular combination reverses the desired arrangement of synthetic insulation on the outside to contain evaporated moisture as it cools so that the down stays moisture-free.

Anyone have actual experience nesting one bag inside another or with a quilt that is large enough to serve as an overbag? Specific bag brands/types would be useful information. Thanks.

FWIW, the JRB Large Family of Quilts functions well as an over quilt or bag in combo with the DTEPC (80 inches of girth).... Several in cold climates persued this approach last year.... see the fifth function and photo here... http://www.jacksrbetter.com/index_files/Large%20Quilts.htm.

As a co-owner of JRB I may be biased

Pan

I use to use 2 Slumberjack Saguaro bags for winter and 1 for summer. it is a 45deg bag but it is heavy for winter. both together weighted 56oz. I used it down to 12deg last winter in a tent and was very warm. I have now gone to a Golite feather(20deg 28oz) and I just ordered a JRB Shenandoah(45deg quilt at 15.5oz) to serve as a summer bag and Overquilt when it is really chilly. I feel like this gives me a good range for all times of the year.

Tommy

Ok, I will pimp for Jacks'R'Better.

What I have tried that did not work:

Big Agnes Zirkel inside a Big Agnes Cross Mountain. I am a side sleeper so my knees and butt would compress the insulation and cause cold spots. Thick pads inside the Big Agnes sleeve use up some of the girth. Great design and concept for a back sleeper.

I wear a 48 regular coat so a 48" quilt is wide enough for a quilt, but not an overquilt.

What has worked:

A Nunatak Arc Alpinist with a down parka overquilt on the foot box and a Jacks'R'Better No Sniveller sideways over the torso.

Last spring I got a Jacks'R'Better large quilt - the Biker quilt that has been discontinued. I used it over the Nunatak Arc Alpinist one night that was below my thermometer minimum of 14 degrees and think it has a lot of potential, but not yet enough experience to review it. However the Arc Alpinist is 55" wide and the Jacks'R'Better is 64" wide and there was NO drafts. The combination had a very luxurious feel.

In the past I have used a mountain hardwear bag expander to increase the width (8 inches, 20.32 cm) of the one of my summer bags so that it will fit over and not compress the loft of the inner bag which is a warmer fall/winter bag depending on the temps. The bag expander is not that light but it does work and you don't have to buy a new sleeping bag.
This system has worked very well for me and you may want to check it out.

phdesigns.co.uk have just added a down overbag to their range----site has a description and temperature ratings for single or combinations---regards from uk

Edited by barryspoons on 11/13/2007 14:55:36 MST.

I have spoken with the folks at MontBell about using two of their bags to increase the temperature rating. They don't recommend using any of their bags as over bags (especially the Super Stretch) because the bags are designed to cling to the body and this would seriously constrict loft.

They did say that by using on of their bags as the base bag and using a specifically designed over bag or quilt could work just fine.

If Montbell says don't use another sleeping bag inside their bags, it makes me wonder about even a down jacket. I've heard others say it won't compress the down, but I'm suspicious.

"Anyone have actual experience nesting one bag
inside another or with a quilt that is large
enough to serve as an overbag? Specific bag brands/types would be useful information. Thanks."

I have been using a JRB Mt Rogers quilt over an LLBean 0* down bag and the quilt works well over both our bags, really. It also is nice to have some DWR on top as our bags do not.
I just bought a Mont-bell 0* hugger (800 fill) which I will also use with the quilt.

Edited by toesnorth on 11/13/2007 15:43:57 MST.

Chad,

Thank's for that research.

Much appreciated!

First off, I'm confused about those JRB website figures. My Western Mountaineering MityLite has a loft of 3" with 12 oz. of 800 down, but its rated to only 40F. Now granted I've slept in it on a 35 degree night near water and I was fine (my head was cold since its not a mummy) but I can still tell you that its rating is nowhere near the 10-20 degree range the JRB numbers are quoting, though I'm assuming you can attribute this to a different type/weight of down.

I am a side sleeper as well so I enjoy the 62" shoulder/ 46" foot girth it provides. Also my WM is a 6'6" bag, which makes it large enough to accomadate my 6' synthetic Mountain Hardwear Lamina 20F bag inside of it, though it doesn't save any weight (combined the two are over 3 lbs...). I would think the Western Mountaineering MityLite would be a good outerbag for someone smaller or with a smaller bag.

Michael D.
If you use the Montbell as an outer bag, won't the elastic on the Montbell compress the inner bags' down and reduce its insulative properties? Just wondering, its a great idea and I like the idea of the elastic for extra movement, thats what made me buy my Western Mtn in the first place, the Mtn HW was just too constrictive.

D.H. Are you measuring both the top and bottom of your bag together? Remember, with the quilts, it is just the one thickness, the top.

DH, et al,

Bags loft is typically stated for the bag zipped and laid out and allowed to fully loft.... So... a 3 inch bag is actually a thickness/ loft of 1.5 inches... about 40 degree range.... Quilts are stated as a single side loft.

Pan

Siegmund,
You asked specifically about the UL#3 and lighter MB bags for layering. I own the #3, and a #7 also. They layer very well with minimal compression of the inner bag which results from the inner baffles of the #3. Ideally one bag with the total down weight of both lighter bags would be warmer, but having two bags such as a 3 and a 7 gives me a system that goes down way colder than I'd ever want to go. For example my 7 ALONE is good down to 0C(32F) in my tent. (wearing a thermawrap layer). Im guessing my 3 would be good down to -10C ambient and -15 layered?