🚀 go-pugleaf

In message <7uvfz6ykdjp.fsf@gina.research.nokia.com>, MB <*@*.*> writes
>Chris >
>> True again, but pale clothing can look grubby in a few hours.
>
>Sure, but that's because it has such a wide range of dirt
>indication. It takes quite a while before it's as dark as
>something that's dark to start with. :)

Wade through a Scottish peat bog and it can happen quickly :-)
>
>> I've tried VB liners and I have to say I don't find them
>> comfortable. The longest trip I've done in really cold weather
>> (overnight lows -5 to -12F) lasted 13 days. I used a down bag with a
>> water resistant shell. It had a red outer and a dark purple inner. I
>> didn't use a VB liner. I aired the bag most days (some were too
>> stormy) and it stayed dry. Although there was little heat in the sun
>> (and most days it was cloudy or hazy anyway) there was a breeze and
>> the air was dry, which is why I think any moisture in the bag soon
>> evaporated.
>
>In my experience, keeping a bag dry in mid-winter (northern
>Finland and some NW Russia) without VB in cold-camp on
>several consequtive nights simply doesn't work. 13 nights
>sure is well beyond that. Otoh, in spring winter, even in
>relatively cold weather, keeping the bag dry usually seems
>trivial by comparision... long days, often with sunshine,
>vs polar night with a few hours of twilight.

The trip I described was in spring - April in Spitsbergen. I haven't 
done any midwinter trips of more than a few days and these have mostly 
been in Scotland with wet cold conditions and temperatures around -5 to 
+5 C.

Midwinter camping in the arctic is not a common backcountry activity :-)
>
>Airing out humid warm air of a relatively warm sleeping
>bag before the bag cools and the moisture starts to condense,
>works, of course. But, if the ambient temperature is low, and
>the bag has sufficient insulation, there will be a large
>temperature gradient through the bag insulation, and
>the exterior parts never have a chance to warm. Without
>VBL, evaporative transpiration will then condense and
>accumulate frost within the cold bag insulation.
>
>Note that the tent interior may be significantly warmer
>than ambient, which improves the chanses of drying the
>bag by airing it. Also, more of the evaporative transpiration
>will then get through the bag and condense on the cold
>interior walls of the tent rather than inside the bag
>insulation. Getting the tent warm enough for this
>typically requires some form of heating, a stove or such.
>
>If outer parts of the bag insulation remain cold after
>the night, and there's condense and even frost inside,
>there's no way one can simply air it away. After all,
>there's snow in the surroundings too, and that doesn't
>get aired away either...
>
>Sunshine absorbed in the (preferably) black (interior)
>fabric will of course warm the bag, evaporating some
>moisture, and also result in a vapour pressure pushing
>moisture through the bag and out of it.
>
>In midwinter, at high latitude, the Sun won't rise, so
>waiting for sunshine to dry the bag isn't really practical
>:). Moreover, very cold weather in the Arctic is typically
>associated with windstill, so airing is the least efficient
>when it'd be needed most. And, wind is typically associated
>with low-pressure fronts, and that means it tends to be
>snowing or raining sleet or whatever.
>
>Typically, in midwinter, the relatively few people
>who backpack over here (Fin), seldom use cold shelters
>for more than occasional single nights. By far, most
>nights tend to get spent in the warmth of wilderness
>cabins. Some may use tarps with live fires, fortunately
>the all-night buring traditional log fires are rarely used
>nowadays (lots of impact). In this light, it's perhaps not
>so surprizing that sleeping bag VBL's used to be practically
>unknown over here.
>
>But, imo, VBL is the way to go, if one is to cold-camp in
>midwinter cold conditions on consequtive nights. The slight
>uncomfort of VBL is a low price for retaining the insulative
>loft of one's bag.
>
In those conditions I would use a VBL too.