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klkl
11-20-2010, 13:52
I'm preparing for some winter backpacking and I wanted to get an opinion on winter sleeping bags. I have read that pairing a synthetic bag with a down bag can be just as effective as using a winter weight bag (-20...etc.). Does anyone have any experience with double bagging?

I have a Long EMS velocity +35 (synthetic) and I'm thinking about purchasing a Marmot helium +15 down bag to fit inside the velocity. Barring fit issues does anyone have any thoughts on this setup?

Thanks!

Wolf - 23000
11-20-2010, 14:27
klkl,

A sleeping bag is effective when it is full expanded. That why the warmer sleeping bag are nomally expand higher. When you place one sleeping bag into another, the inter sleepingbag is not able to exand fully making it not as effective.

Wolf

Grinder
11-20-2010, 14:53
Pan, on Hammock Forums, published a formula to estimate the combined temperature rating of two nested bags. I believe it's available there or at Jacks-r-better web site.

http://www.hammockforums.net/forum/showthread.php?t=297&highlight=combined+temperature+rating

Feral Bill
11-20-2010, 15:20
Back when I hiked in serious winter conditions (the Whites and Adirondacks, way below zero) I always used a double bag. You gain versatility for varying conditions for little extra weight.

Luddite
11-20-2010, 15:27
Why not get a sleeping bag liner? They add 10 or 15 degrees of warmth and you wouldn't be taking the loft out of your sleeping bag.

http://www.rei.com/category/4500057/q/Sleeping+Bag+Liners

Luddite
11-20-2010, 15:29
Oh you want it really winterized to -20*...I thought it said +20.

burntoutphilosopher
11-20-2010, 15:56
if it is going to actually be -20F ambient, do be sure you pick up a nice exped downmat ...

... i hiked hecla island in winter (in manitoba) and a good ground mat is essential

Stir Fry
11-20-2010, 16:31
This the system I use and it does work but not as good as it looks at first. I do it becouse I don't go out in that cold enough to warrent getting a bag rated that low. It is an option though when I do go out in the winter. A 35* bag and a !5* bag should be good to about 5*. Acording to the chart I have at home. Wolf is correct you lose some loft from each bag. Be great is you could just ad the two together.

Toolshed
11-20-2010, 17:23
At first glance, it would seem to make sense, but keep in mind that in winter, you want as little additional space in your bag as possible - Less to heat up when you are sleeping. You want the bag to have as much loft as possible as it is this trapped air that resides between the inner and outer walls of the bag that will keep you warm. If you place one bag within another, unless the outer-bag is a true over-bag with a larger cut, you run the risk of compressing the insulation in the bag that is most compressible. This could cause you to sleep colder than what you would expect. Sometimes, even colder than just one bag.
What you really need to do is pick up an over-bag, which is cut larger and will loft, while not compressing the inner bag.
This also happens when someone wears a nice thick parka in their sleeping bag, thinking it will keep them warmer. If the thick cut of the parka compresses your sleeping bag loft, you're in trouble.

If you are having trouble visualizing this, think of wearing a really thick pair of rag wool gloves then you decide to put on a pair of nylon shell insulated ski gloves over them. Your outer glove nylon shell limits the amount of space you have inside the glove and will compress the inner wool glove enough so that your hands will get colder - since there is no trapped air to slow the loss of heat.

I would strongly suggest that if you expect to routinely be doing things in below zero weather, you get a proper winter bag. One with a thicker draft tube, a better collar, a chest drawstring and a thicker hood. I realize the costs may be much higher than the other method, but sleeping in below zero weather in the whites, greens or Daks isn't the time to find out a new concept isn't really operational.

Panzer1
11-20-2010, 20:29
you could get into the Marmot helium +15 down bag. open the 35 degree bag up and lay it over the down bag like a blanket. you will have minimal compression of the down bag.

but the best idea would be to cough up $400 and buy a zero degree bag. it will way weigh less and take up less space in your pack.

Panzer

Lyle
11-20-2010, 22:55
There used to be systems like this made, with the bags sized appropriately. I haven't read all of the posts, so not sure where the suggestions have gone.

One possibility that should work would be to check out the PeaPod, made and sold by Speer Hammock. It is designed to go over a hammock, so would be plenty big enough to encompass another bag without compressing it. No reason it shouldn't work on the ground as well. Just a thought.

Tinker
11-20-2010, 23:02
I use a Golite Feather-lite bag over my basic hammock most of the year. It's rated to 40 degrees but is comfortable (for me) down to 30. In hot weather I use a Montbell liner bag good down to 50 degrees over the hammock, and in the winter I use both together, the Montbell bag as an overbag inside my Golite. With my winter tarp setup and some warm down clothing and a hot water bottle I have slept comfortably down to 5 degrees one windy winter night in New York.
The downside to double bagging is that you're carrying around an extra two layers (the inner and outer fabric of your second sleeping bag). That doesn't add up to too much these days with bag fabrics available weighing less than 1 oz./sq. yd. but it is extra weight. The flexibility in a wide range of temperatures may offset this, however.
Remember to think of your sleeping clothing as a part of your sleep "system" and pack accordingly.

Tinker
11-20-2010, 23:06
Why not get a sleeping bag liner? They add 10 or 15 degrees of warmth and you wouldn't be taking the loft out of your sleeping bag.

http://www.rei.com/category/4500057/q/Sleeping+Bag+Liners
A fair amount of young folks use sleeping bag liners (some older ones, too), but most people who have hiked longer distances would prefer to carry a set of sleeping clothes made of similar materials to those used in liners to carrying a single use liner - ie: you can't walk around the campsite or visit the latrine wearing a liner, and they aren't very practical for around town wear;).

leaftye
11-20-2010, 23:15
There used to be systems like this made, with the bags sized appropriately. I haven't read all of the posts, so not sure where the suggestions have gone.

Like the military ECWCS system or the Wiggy's bags? Those are crazy heavy. Warmlite makes a flexible system too.

Tinker
11-20-2010, 23:22
Like the military ECWCS system or the Wiggy's bags? Those are crazy heavy. Warmlite makes a flexible system too.
I had a Warmlite. They have a built in vapor barrier designed to keep the down isolated from the body's insensible perspiration. It works for the down, not so much for the user. I found that the temperature comfort range of each top was narrower than that of a non vapor barrier down bag. If you wear any clothing inside them you emerge damp to a not so friendly world of cold, causing a rude awakening. For a vapor barrier to be most effective it should be worn against the skin, and vapor barrier clothing, worn under regular clothing is extremely effective in boosting the temperature rating of either insulative clothing or a sleeping bag, but then, again, the negative aspect of having a narrow comfort range, temperature-wise, raises its ugly head. Ventilation is key in vapor barrier systems.

leaftye
11-20-2010, 23:23
I have a vapor barrier quilt.

Tinker
11-20-2010, 23:29
I have a vapor barrier quilt.
I'm sure I'm not the only one who would benefit from any information you'd like to share on your quilt.

We're waiting...................:).

leaftye
11-20-2010, 23:38
Unfortunately my vapor barrier quilt experience may not help with this discussion. It's a 0 degree, 20.8 ounce generously sized cuben fiber down quilt built by Tim Marshall of EnLIGHTened Equipment. I do get sweaty sometimes, but the beauty of a vapor barrier is that the insulation doesn't get compromised or gain weight. Greater experience and better fitness on my part should result in much less moisture. I usually dry off within a few minutes of breaking camp, so it's not a problem other than the smell I get from sleeping in my sweat. But it's totally worth it for the weight savings and having a single quilt that can be comfortable all year long. I would like to try using my quilt within my (zero degree) sleeping bag for subzero nights, but I would have to travel to experience nights cold enough to warrant it.

Tinker
11-20-2010, 23:44
Sounds like a very nice piece of equipment. A quilt does make ventilation very easy, so it might be better having a vapor barrier built in than it was in the Stephenson bags. To allow for ventilation they had miles (exaggeration) of zippers, adding to their weight. They are also rectangular bags, wasting efficiency and adding further to weight. Warm - yes. Light - not so much.

english
11-21-2010, 02:18
http://www.rei.com/product/798715

Just bought the ALPS Razor sleeping bag cover (26oz) for my 20' rated bag, throw that on my Thermorest & I think I should be ok in my Hammock in Jan. Think being the operative word of course!

burntoutphilosopher
11-21-2010, 11:32
^^ i may be mistaken, but i think the OP wants to be good to 20 bellow zero, not 20F.

in that instance air intrusion becomes such a huge issue that you wan things to fit as tightly as possible around your neck etc. thus why the good bags have huge draft tubes etc.

Slo-go'en
11-21-2010, 12:29
When I used to spend more time out in the cold then I do now, I always used a two bag system. It it important to have the outer bag big enough so it does not compress the inner bag. I have a bag specifically made for this, it is a lot roomier inside than what would be usual. Not sure if they still make something like this. I suppose one could use a second bag more like a quilt if you had enough insulation under you. (Two close cell foam pads are recommended).

Speaking of foam pads in the extream cold, be sure to roll them up as soon as you get out of the bags. If not, they might freeze to the ground/snow and any condensation will freeze them together. It is also a good idea to stuff your bags as soon as you get up to push the damp air out of them, or they will freeze up too.

burntoutphilosopher
11-21-2010, 13:49
^^ i had a real problem with my down bag doing what slo-go'en suggested.

the vapour in the bag froze in my stuff sack on a trip up here in central BC, it wasn't that cold was like 18 bellow at night and around 0 during the day.

stuffed the bag into it's sack, and when i went to pull it out it was frozen clumps of down that NEVER relofted, even after coming home and tumbling in the dryer on no heat.

... i spoke to marmot about it and the guy emailed me saying to in the mornings hand compress the bag, then shake it back out and recompress 3 or 4 times before stuffing for the day ... i later did this and the steam coming out of the bag was unreal. the vapour seeks the cold air so osmosis helps you in getting the water vapour out.

back to the original topic, to the OP: what kind of shelter will you be in? i wonder with a good downmat under you, and if yo uare in a good tight bivvy if it's just for a few days if you could use some kind of magnesium warmer. we used magnesium warmers on our trip in manitoba and it was warm in the tent down to unreal temperatures (don't know how cold it was, we packed it in, but that same week it hit 54 bellow zero)

do not underestimate how cold 20 bellow zero is compared to simply 0 degrees. 20 bellow is a temperature in which you reall could die not doing it right... i recommend getting a made for it bag.

Del Q
11-21-2010, 17:33
I recognize that this could be a separate issue, but in really cold temps I find that the GROUND gets me colder than the air, are there cases where one bag with a liner and TWO pads makes sense? A customer of mine gave me some new-breed attic insulation that is light and thin, am going to test this out with Neo Air mattress, 25 degree bag and a liner.

Any thoughts?

Toolshed
11-21-2010, 17:47
I recognize that this could be a separate issue, but in really cold temps I find that the GROUND gets me colder than the air, are there cases where one bag with a liner and TWO pads makes sense? A customer of mine gave me some new-breed attic insulation that is light and thin, am going to test this out with Neo Air mattress, 25 degree bag and a liner.

Any thoughts?
for below zero camping, 2 pads should be De rigueur .

leaftye
11-21-2010, 18:50
... i spoke to marmot about it and the guy emailed me saying to in the mornings hand compress the bag, then shake it back out and recompress 3 or 4 times before stuffing for the day ... i later did this and the steam coming out of the bag was unreal. the vapour seeks the cold air so osmosis helps you in getting the water vapour out.

Great tip. I've heard it for the first time this summer, but haven't had the chance to use it with my sleeping gear yet. I do try to use it with my down jacket before putting it away.


I recognize that this could be a separate issue, but in really cold temps I find that the GROUND gets me colder than the air, are there cases where one bag with a liner and TWO pads makes sense? A customer of mine gave me some new-breed attic insulation that is light and thin, am going to test this out with Neo Air mattress, 25 degree bag and a liner.

Any thoughts?

I'm not sure how you're going to use that attic insulation, but a Neo Air is not suited to subzero temperatures. And you should definitely increase the warmth of the pad beneath you when the temperatures drop. While adding the r-value ratings of pads is usually good enough, I'm not sure that applies with an uninsulated air mattress. For subzero temps, the least I would do is use a closed cell mattress above AND below that neoair.

burntoutphilosopher
11-21-2010, 19:04
delQ, if the attic insulation is the pink kind, it needs to be fluffed between the studs to really insulate well... not sure how you'd lay on it without compressing it too much. that stuff is R6 when rolled out and left uncompressed, some of it is R 8.5.

as far as cold weather pads, the Exped DownMat (made by OR) is an incredible piece of kit. they have the downmat 7 and downmat 9. the downmat 7 i have used far past 20 bellow zero and is a great item though a bit pricey, like 160$. no clue what the downmat 9 costs.
here is the downmat 7 compared to the neoAir:
http://www.youtube.com/watch?v=bV51oFZfTWY

i would want an R value of 6 underneath me at 20 bellow zero.
but honestly it leaves me thinking, where are you camping on the AT that is really likely to be that cold. as i said before you can DIE at 20 bellow zero if you don't have the right gear; i worry this is not a good place o cheap out and throw two 80$ bags inside eachother and say 'huh good enough'. care must be taken.

Toolshed
11-21-2010, 20:19
....but honestly it leaves me thinking, where are you camping on the AT that is really likely to be that cold.
LOL Anywhere N of Massachusetts. :D

burntoutphilosopher
11-21-2010, 20:35
Tollshed,
ambient temperatures 20 bellow zero before the windchill?

when i was in Quebec it never got that cold. even in maine's coldest month (january) the average low is 5 above F.
quick search at weather underground showed only 3 instances of new england hitting 20 bellow actual temp in the last 2 years... not to say 20 bellow doesn't happen, but are you happening to be out there on the one coldest night of the year ? if the weather shows a huge front coming in, delay the trip a few days !

i wasn't trying to argue, but saying prepping for 0deg. F, is NOTHING like prepping for 20bellow F.

Toolshed
11-21-2010, 21:27
I've been in the whites and the Adirondacks where it has been well below zero at least every other winter we seem to hit in the negative teens to 20's. Granted there are plenty of lighter subzero to high teens days/nights, but once you get in the cols (valleys) all bets are off. The temps really drop - Especially in February - We trend to go more then as the days are getting longer, however we are just past the shortest days and therefore still facing the coldest period as we are still cooling (Much like August is just past the longest days, but is very hot as we are still heating up in our hemisphere.)

It might be 5 below in Syracuse, Oswego, Burlington or wherever they are reporting, but it can get much colder in the mountains. We were in Tupper lake one weekend (NY 2000 or 2001 perhaps) and it was between 30 and 40 below. The big thrill was throwing a pot of boiling water up in the air and watching half of it turn to vapor cloud and the other half fall as ice sprinkles.

A winter companion of mine is an engineer and a geek and carries a minimum registering thermometer with him - I can easily count on one hand the trips where it was in the minus 20's.... But I do not think the cold temps we have had in the 80's & 90's have carried over into the 00's with the same frequency.
PS Not saying it is always enjoyable that cold. stuff breaks easily (especially MSR Pumps), gas doesn't light easily and it is hard to do anything but lie in your tent once the sun goes down. :)

Toolshed
11-21-2010, 21:32
NY Adirondacks may also have some colder temps than Maine or Quebec due to Lake Ontario. Here is an excerpt (http://coolweather.net/statetemperature/newyork_temperature.htm)

"The winters are long and cold in the Plateau Divisions of the State. In the majority of winter seasons, a temperature of -25 F or lower can be expected in the northern highlands (Northern Plateau) and -15 or colder in the southwestern and east-central highlands (Southern Plateau). The Adirondack region records from 35 to 45 days with below subzero temperatures in normal to severe winters, with a somewhat fewer number of such days occurring near Lake Champlain and the St. Lawrence River. In the Southern Plateau and in the upper Hudson Valley divisions, subzero minima are observed on about 15 days most winters and on more than 25 days in notably cold ones."

burntoutphilosopher
11-21-2010, 22:03
i don't live east coast... i wasn't trying to say it was impossible...i reread it came out that way...

i just didn't know about what the OP originally intended...
... i certainly wanted to be clear what a huge gear difference 5 and 0 F is required compared to 20 bellow zero F.

maybe he's spending 3 days in Pennsylvania in march for all we know... he could have used 20 bellow figuratively.

if it really is going to be 20 bellow though, take your gear seriously. don't throw 2 35 degree bags together and assume it'll be good enough unless you have a car within safe walking distance.

yall have a good night i'm out

klkl
11-22-2010, 11:01
Thanks for all of the replies everyone. This has been very helpful.

I was aiming to have more flexibility and that's why I was considering a double bag system but my +35 degree bag will certainly not be enough for the outer bag even if if it doesn't restrict the loft of the inner bag.

I am preparing for overnights in the Whites so it's looking like I need to get a 0 degree bag and a liner or a -20 degree bag. I'll probably just rent for now in that case.

Franco
11-22-2010, 16:40
"the Exped DownMat (made by OR) "
Not that it really matters but OR were the agents for Exped not the manufacturers.
Exped has now their own subsidiary for the US and Canada, Expedd LLC.
Franco

Toolshed
11-22-2010, 21:14
Thanks for all of the replies everyone. This has been very helpful.

I was aiming to have more flexibility and that's why I was considering a double bag system but my +35 degree bag will certainly not be enough for the outer bag even if if it doesn't restrict the loft of the inner bag.

I am preparing for overnights in the Whites so it's looking like I need to get a 0 degree bag and a liner or a -20 degree bag. I'll probably just rent for now in that case.
Don't hesitate to join Viewsfromthetop.com - there are a lot of folks that do winter trips on the board. (When I say winter, I mean zero to subzero weather) :D