Simple question with no doubt a complex answer.

If you put a minus 10C sleeping bag inside a minus 10C sleeping bag does that make a minus 20C sleeping bag?

I'm thinking it can't be that simple. Obviously the increased insulation from 2 bags would be better that 1, but would it really keep the heat in with double the cold ?

Has anyone done it? (It's my guess if it didn't work you won't answer )

__________________
Regards Tim

Learning my craft for the big stuff, it won't be long now and it's not that far anyway

I actually don't know as I have never tried. But having camped extensively in the deepest colds of Norwegian winter, I can tell you this: If you want to camp in temps of -20C, you want to get as warm a sleeping bag as you can. The rule of thumb in winter camping is that you can never get a too warm sleeping bag. Get a proper winter-worthy mattress as well.

__________________
HansP
All you wanted to know
about riding in Norway

No

A -10 bag is in reality probably good down to about +5 or 0 depending on how easily you feel the cold. Doubling it up would have little effect as the idea of the sleeping bag (or any insulation) is to keep warm air in contact with your body (hence why you shouldn't sleep with clothes on in a sleeping bag)

I slept outside on a thin mattress down to -20 without a tent and was toasty warm in a -40 bag. My friend in a -15 bag was miserable when it was below about -5 ish.

Buy the best bag you can get.

__________________
EurasiaOverland a memoir of one quarter of a million kilometres by road through all of the Former USSR, Western and Southern Asia.

+2 on the above.

It may even be colder if the bags squash each others insulation.

Get the best bag you can.
Get off the ground with a bed or the best insulation you can.
Strip off or change into clean pyjamas / thermals. Cold fresh clothes seem to get the body ready to stay warm.
Have a hot non alcoholic drink and small snack like biscuits. You want internal heat to get off to sleep.
Get into the sleeping bag and take time to sort the zips and hood. Wear a hat if comfortable.
Realise you need a pee so get out again
Repeat steps 1 to 5.
Have snacks ready for if you wake up cold.

Don't get ****Ed and if you will need to go in the night take a plastic bottle because a Sigg bottle will give you frost nip in the place you really don't want it

Andy

good advices .
a good s-bag has 3 values, confort, limit and else . Forget all but the confort value .
An under 20 is big, expensive and must be a " duvet" ( real duck) ; and also quite expensive .
Get isolated from the ground , really
from the wind , ie good place for the tent/tarp .
It is not something you can improvise ( i know what i am talking about , for trekking and skiig ang army souvenirs )
A warm drink could be useful and a good stove either

I put some thoughts down back in noughties here

https://sites.google.com/site/threew...ie/cold-places

I don't use the army sleeping bag anymore, you can get lighter and just as warm for a hundred quid now, but the rest might give you a giggle.

Andy

A long long time ago whilst "camping" in early spring there was a real cold spell.

I pulled about 18 inches (50 cm in new money) of fresh green bracken shoots and packed it that deep under my tent.
First night although still cold was better than without.
Second night wass was definitely a bit warmer.
After that the underfloor heating really kicked in and inside the tent was quite warm maybe 15C or therabouts. -10C or colder outside.

Reason is fresh green stuff composts and will provide warmth for weeks.

If you intend stopping somewhere for some time eg fishing trip, this might be useful, but the vegetation you use must be fresh and usually green.

You might want to put plastic sheet between you and the compost

Many years later I used this technique when camping on a municipal campsite. I pitched my tent on their composting grass pile The guys I was with just could not believe how warm it was inside my tent.

Back in the days when I was still naive enough to believe marketing hype (rather than the Doubting Thomas cynic I've since become) I actually bought a sleeping bag constructed along those lines. It was two bags - one narrow / one wide) designed to fit one inside the other, with each of the individual bags rated to 5C (so summer use) and the combination rated down to a few degrees below zero.

It sounded like a great one-size-fits-all solution but in practice the two bags together were hardly any better than each one individually and it was massive to pack. In the end I gave up with it and I do remember the smaller bag ending its days stuffed down the back of the airing cupboard at home. Sadly (fortunately) time has erased the manufacturer's name but I think it was some kind of start-up rather than one of the big players.

Not being part of that world I don't know how sleeping bag manufacturers work out the ratings of their bags - whether they have an engineer balancing out heat transfer coefficients against the thermal properties of down / feathers, or whether they just stuff more down in until the marketing dept thinks it looks about right - or even if there's a Euro std for determining cold resistance, a bit like car mpg figures. Either way my own subjective figure is that -20C feels a damn sight more than twice as cold as -10.

I have camped in some really cold weather; -40 for example - and colder (this is no exaggeration). -20c is a good start for winter camping, but to also be respected. I think your two bags in combination will be weak for -20. Get a large sized -20 rated bag, and use the -10 bag inside it.

I used two bags, one larger than the other so there is room for the inner one to loft up. Other items of as much/more importance: Have a winter rated insulate sleeping pad under you. The ground is a major source of cold. Put your jacket under or over your bag at night. Bring your socks in the bag, not on your feet, to dry them out. Moisture is your enemy. Camp where you are protected from the wind, and in some sort of shelter (tent, tarp, snow cave). Most important, eat high calories during the day and before night. Fat calories are long lasting, and butter is a typical source of those calories. Melted butter with your starch is a way to consume lots of butter. Peanut butter is another good fat source. Sugar calories are fast heat but not long lasting.

Don't get in trouble with cold because hypothermia can be fatal. Work your way to colder weather camping, so you learn what works along the way. It's a matter of gear and knowledge and experience. You don't need the most expensive sleeping bag, you need the gear that works for you and your skills.

I bought a -7 'conform' bag and it's anything but under zero.

I think you're correct ... you won't get double but sure gonna be better than a single bag!

Comfort (and survival) will also depend on what is under you. A good insulating pad makes a world of difference. During two Antarctic tours I camped on ICE a few times, in support of Ornithologists doing Bird studies.
Oh Joy! Once for a week. Not a great time ... but it was work, no choice in the matter.

Temps were cold but not outrageous ... 10F (about -12C) We had Down Navy survival bags (best US military had in 1977) and Cots! I still froze my ass off.

I would not recommend Winter camping for any length of time. For me? emergency only. You can't ride in such temps, why would you camp there? Head South! (or North for Southern hemisphere!)

Rather than 2 bags, maybe use a Bag liner. They help a lot. Not sure how much they add to temp range but I'm sure it's noticeably better.

Sidecars work, also studs and outriggers Swedish style. Fresh snow is like sand so silica based knobblies work if you are prepared for a bit of falling off. The grip returns to correctly laid northern roads at minus something silly as there is no liquid water to lubricate sliding.

You have a problem that what works best in the mountains is useless in city sludge and if the weather changes youll have brought the wrong machine, but that's just organisation. Sidecars are the best all round solution as you can also carry the fire box, fishing kit and schnapps.

Andy

Rule of thumb, one dog for each -5C below zero.

Get a couple of catalytic pocket warmers. Cheap, light and amazing.
One at your feet & one under your neck/back
I've been using them for 35yrs & they take up no space.

__________________
My memory is becoming that good, I should be able to organise my own surprise party soon

I used 2 bags together for minus 30 many nights when I was younger and had a younger heating system. The bags were Blacks Icelandic's and they were made as a system, an inner and an outer. You could use the inner in warm weather and the outer was good by itself for say minus 10 C.
They were very high quality bags made from Egyptian cotton and 100% pure goose down, no feathers. I used this system for 20 years before they wore out and I camped and traveled a lot!! I paid 70.00 for this combination in 1969.

Last year I was looking in the local buy and sell for used sleeping bags and lo and behold saw an ad for 2 Blacks sleeping bags, called the seller and they were Blacks Polar( circa 1975) that were as close to brand new as you could get, only used a few times in his camper van. I bough both for 75.00
In today's bag selection they are easily 400.00 bags each!

If you can carry a foam type mattress that will be warmer than any of the newer thinsulite pads.