View Full Version : Multiple down bags
I was wandering...I have a down bag that is rated at 32 degrees...I've have it out at 34 degrees already and would say it is a 32 degree bag, only one cold spot on the upside hip otherwise I was warm with only a long sleeve cotton shirt and long john pants on. If I were to have two of the same bag how would that change the temp rating? Obviously it should make the temp rating drop lower but how much lower. Is there any decent way of determining that. I love how small this thing packs and two of them would still take up less room than my old 20 degree bag.
Teacher & Snacktime
10-17-2013, 18:04
Someone explained to me that down bags need breathability, and that nothing should cover them. Why not just get a zero degree down?
It's done all the time. Someone gave a specific formula a while back on the temperature gain. It wasn't as efficient as a single warmer bag but if your budget is tight and you have two bags it works. I had a 40 degree synthetic bag and a 20 degree down bag as a kid and used both bags for winter camping in New York.
Teacher & Snacktime
10-17-2013, 18:16
Does the down bag have to go on the outside to prevent moisture retention?
Does the down bag have to go on the outside to prevent moisture retention?
Mine did because the synthetic was smaller. You don't want to constrict the loft of the down bag either.
Teacher & Snacktime
10-17-2013, 18:22
I have a cheapo fleece bag from Dick's (40-50 degree) which I was planning to use as a liner for a 20 degree down bag if weather warranted. Any idea how effective this might be?
I have a cheapo fleece bag from Dick's (40-50 degree) which I was planning to use as a liner for a 20 degree down bag if weather warranted. Any idea how effective this might be?
Maybe 10 degrees which is a complete WAG
Kerosene
10-17-2013, 18:29
Part of the challenge will be to retain the loft of the down bag. Trying to squeeze one bag inside another may very well compress the loft both bags to some extent. You might be better off with opening up one bag and using it more like a quilt atop your mummy; as long as the topmost bag isn't too heavy then that should maximize your overall loft.
I know the bag I'm looking at is very light, a little over a pound and stuffs incredibly small. To have bought it for $69 at Walmart I still can't believe I found something like it at Walmart. They only carry junk products. Granted the inside and outside cover aren't the best material, hence the lightweightness of the bag as a whole. I was thinking if I could put two them together and down around 10-15 degrees it would be far cheaper than going for a regular 20 degree or even 0 degree down bag. I know I can use the 32 degree all summer long. Not sure if I will end up doing anything this winter or not but I'm trying to think ahead of time so I might be able to plan ahead of time as well.
Part of the challenge will be to retain the loft of the down bag. Trying to squeeze one bag inside another may very well compress the loft both bags to some extent. You might be better off with opening up one bag and using it more like a quilt atop your mummy; as long as the topmost bag isn't too heavy then that should maximize your overall loft.
I could easily see doing something like what you say. Actually just lay the second bag, unopen on top of the first bag. That would give you twice the loft with the second bag and provide even more warmth.
Rasputen
10-17-2013, 18:42
Combined bag rating
x -(70 - y)/2 = z
x = first bag (higher rated/lower degree)
y = second bag (lower rated/higher degree)
z = rating of doubled bags
I remember years ago (15+) I had a cat's meow (around 30 degrees) and a mountain hardwear summer bag (approx 45 degrees) both synthetic. Placed the MH inside TNF coupled with beanie/ long tops/ bottoms/ socks, and stayed toasty on winter trips. Now I just prefer a good down winter bag.
Look at the Kelty cosmic 20 degree. Cheaper than two of those bags, decent quality and not a bad weight either.
max patch
10-17-2013, 20:20
I understand what you are trying to do if for some reason you already owned two 32 degree bags for whatever reason. Since you dont - if I understand you correctly - it would be crazy to buy another 32 degree bag. You'd be happier getting a 15 degree bag. Lighter, less bulk, and you'll have a better experience than mating two bags.
Teacher & Snacktime
10-17-2013, 21:06
Look at the Kelty cosmic 20 degree. Cheaper than two of those bags, decent quality and not a bad weight either.
I have the Kelty Cosmic Down 20....it's actually only good in the high 30's, which is why I'm planning on trying a fleece liner with it.
I have the same Fleece bag from Dick's and absolutely love it. Not exactly sure how many more degrees you will get out of it but it is cozy as a liner. I have used it in the 40's and tossed my 40 degree synthetic bag over top like quilt.
Another option is to stretch the temperature rating of a single bag. I have had a 20 degree quilt below zero (on snow) with many layers, a doubled pad and a sleeping bag liner. Today I would use that same quilt with a full VBL suit, insulation, my xtherm sleeping pad and extra insulating layers and I would have a system that I know would be comfortable at zero and below. Good site selection plus proper cold weather eating will also go a long way to stretching a single piece of gears capability. I find it a very satisfying challenge to see how far I can stretch my normal 3 season gear with minor additions or replacements. Just another option.
I've been using a down 40 degree bag plus down socks, down pants and a down jacket to around 25 degrees. I like not having to retreat to my sleeping bag immediately.
Look at the Kelty cosmic 20 degree. Cheaper than two of those bags, decent quality and not a bad weight either.
That depends on the Kelty cosmic 20 that you end up getting. I bought one off ebay for $90+ back in July. I thought I had bought a down bag. Turns out I can hardly fit it in my backpack and it weighs a ton. According to the Kelty website it should have been a down bag that measured(packed) something like 8x15, or something like that. Not much bigger than the Walmart bag I bought. The only problem was when I got the bag it was much bigger than what I was expecting and it wasn't down, it was synthetic. Watch what you buy when you buy anything Kelty. You might be in for a surprise.
88BlueGT
10-18-2013, 10:27
Seems to me it would be much more efficient to just get a liner?
Another option is to stretch the temperature rating of a single bag. I have had a 20 degree quilt below zero (on snow) with many layers, a doubled pad and a sleeping bag liner. Today I would use that same quilt with a full VBL suit, insulation, my xtherm sleeping pad and extra insulating layers and I would have a system that I know would be comfortable at zero and below. Good site selection plus proper cold weather eating will also go a long way to stretching a single piece of gears capability. I find it a very satisfying challenge to see how far I can stretch my normal 3 season gear with minor additions or replacements. Just another option.
Actually I did back in the past with a 0 degree synthetic bag I had. I had bought thing to replace my old North Face Blue Kazoo that had pretty much matted and become useless through constant use. I sleep in a hammock and sleeping bag every night at home to they get constant use. I also sit around house inside the sleeping bag all the time as well. Heavy use. I went outside as the temps kept dropping and hooked up the hammock to the trees and kept going out at lower and lower temps. I managed to hit -8 with a o degree bag. Actually ended up finally hitting the trail for a couple of winter overnighters as well when the weather forecast was looking good and the temps were in the teens overnight. Right now I'm thinking more in the line of possibly of maybe winter bike camping. I'm actually trying to keep myself from doing it but I don't think it's going to work. Packing size is a bit of a factor and I'm trying to keep the cost down as well. Hence why I've thought about using a double 32 since they pack so darn small and I would have the back up for summer use for whenever the first one crapped out on me. Admittedly I'm going to try to see if can't get by this winter at home with the fleece bag I bought earlier this summer for summer bike camping and save the down bag for outside use only.
Combined bag rating
x -(70 - y)/2 = z
x = first bag (higher rated/lower degree)
y = second bag (lower rated/higher degree)
z = rating of doubled bags
Actually to do a little testing right now with what I already have here's a rather bizarre question. I have a fleece non mummy bag(50 degree) and the 32 degree down mummy bag. That says the combined temp rating should be 22. With the temps getting colder again I could easily test that combo right now and see how this formula works. The question is...which bag should be on the outside and which on the inside...or does that even matter? I realize the fleece bag would go much easier on the outside since it isn't mummy shaped. But would the location of the bag, in the case of different temperature rating, matter or not?
greentick
10-18-2013, 23:43
Fleece on the inside. Put whatever is "loftier" on the outside. Additional plus is that you will keep you down bag cleaner as you can easily toss the fleece bag in the washer.
Part of the challenge will be to retain the loft of the down bag. Trying to squeeze one bag inside another may very well compress the loft both bags to some extent. You might be better off with opening up one bag and using it more like a quilt atop your mummy; as long as the topmost bag isn't too heavy then that should maximize your overall loft.
+1
rather than use 2 bags, I use an oversized bag or quilt and sleep in camp clothes including down jacket and pants if its really cold. Very important that the second bag or what you wear does not compress the down loft from the inside.