Overbags, Inners and Double bagging

BogTrotter said:
How does it work then?
Click to expand...
In a typical double walled tent you start to observe a described effect of a dew point inside a bag at about -24c. Under a tarp at -18c or so. And it will take 3+ nights so you start noticing it really, and 5+ to really degrade an insulation efficiency of a down sleeping bag.
Modern sleeping bag down proof outer shells are tuned exactly so this kind of stuff doesn't happen in most conditions
Maybe was a case 40 years ago 🤷‍♂️
 
echo8876 said:
In a typical double walled tent you start to observe a described effect of a dew point inside a bag at about -24c. Under a tarp at -18c or so.
Click to expand...
Few of us would likely find ourselves in those situations, it’s true.

It’s likely that under such circumstances suitable sleeping bags would be a priority and when you’re getting down to the likes of -18c and lower it would be unlikely that you would be combining a 3 season and 1 season sleeping bags, or using some ready made commercial cover of sorts whilst trying to keep weight down.

Some beneficial covers can be as heavy as a prime sleeping bag, so the attraction does have a weight penalty.
 
BogTrotter said:
Few of us would likely find ourselves in those situations, it’s true.

It’s likely that under such circumstances suitable sleeping bags would be a priority and when you’re getting down to the likes of -18c and lower it would be unlikely that you would be combining a 3 season and 1 season sleeping bags, or using some ready made commercial cover of sorts whilst trying to keep weight down.

Some beneficial covers can be as heavy as a prime sleeping bag, so the attraction does have a weight penalty.
Click to expand...
you don't go into -30c alone for days on end. It's a privilege of a few cut of a much tougher material than usual human being. That's the only people who should worry about vbls. Even pro alpinists with their obsessions usually utilize vbl socks like once during their week-long guide certification survival course, and forget that experience like a nightmare to never be repeated again.
And if you are an enjoyer or a typical cross country ski ventures in Urals taiga, you usually have at least 8-10 people with you, a large tipi tent and a stove. So this is not an issue, everything gets dry every night. Only elite of elites that smell of kerosene even in summer, go to places where VBL liner is justified.
And yes for anything below actual -20c i would pack a -35--40 sleeping bag.
 
When I want to boost the rating of my sleeping bag, I normally used a liner (silk or S2S reactorlite). I'm a warm sleeper, high summer I may use the liner on its own. I also use a heavy duty survival blanket - foil with thin fabric coating on one side - 180cm by 110 cm and 190g. This combination with a 10degC 1/2 season bag has kept me warm and happy to below freezing.

Some years ago I came across a chart showing the benefit of combining sleeping bags - I wrote down the figures but did not record where it came from :rolleyes: However to summarise the chart working in Fahrenheit, you add the two limit temperatures together and then subtract 70 degF. Hence two 50degF bags combined equate to 30degF, or 0degF bag with a 30degF one equates to a -40degF bag. The table does not specify values for combinations below -40degF. Working in centigrade the maths is more complicated.
 
I use a silk liner in summer, it's easy to machine wash and if it's very hot or I sleep in a cabin, I use just the liner without the sleeping bag.

In winter, a pair of down pants and a down jacket add a few degrees to my bags rating. The pants weigh about the same as a liner and make camp life more comfortable and I always bring the jacket anyway.
 
You must log in or register to reply here.
Back
Top