That could mean heavier sweating = more moisture inside bag.Derr... I don't understand that logicIf the heat's not getting into your bag it's because it's staying close to your body.
What's the deal with sleeping bag comfort ratings?
- Thread starter R3XXY
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True, but you either want it warm or not - regulate by layers as always and wear wicking materials.
If one has enough on (something like polyester fleece) I don't think any reasonable amount of sweating will make one feel cold before being so hot that something has to be taken off. But yes excessive sweating thinly clothed in a thin bag is not a good combination but that does not usually happen in normal conditions (too much ethanol is abnormal (nowadays)).
A lot depends on how old you are, how hydrated and well-fed, too. Booze doesn't help . But mainly, being properly insulated from the ground and having something keeping the wind off is significant.
I always thought ratings indicated only that you won't die at these named temperatures if you have also taken the above into consideration. Not really about comfort.
Of course, you also get too hot using a Winter-rated bag in the Spring. Or, rather, you can end up shrugging out of it whilst asleep and then getting woken up by tthe chill.
I always thought ratings indicated only that you won't die at these named temperatures if you have also taken the above into consideration. Not really about comfort.
Of course, you also get too hot using a Winter-rated bag in the Spring. Or, rather, you can end up shrugging out of it whilst asleep and then getting woken up by tthe chill.
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It really depends on wether the person is shedding enough heat for the bag to work properly. Do you understand that logic? It’s the way the bag works,you see. It traps your heat. No bag is a ‘warm’ bag,it’s the person inside.Derr... I don't understand that logic
Regards
Ray
Still struggling TBH - no coat is a warm coat either. It's a very cold day, I have my merino base layer, a mid layer, and a quilted jacket on - I'm still cold but you're telling me to take my base layer off? Goes against all my own cold climate experience if I'm honest. Trapping air as close to your body as possible (as long as the material wicks away the moisture) is the accepted wisdom of staying warm I thought. If I'm too warm I remove or ventilate the outer layer not the base layer.
That is not how it works. It is not the clothes that keeps your warm but dry trapped air. Air is the best insulator of heat but only when it does not get moist.Derr... I don't understand that logic
A good sleeping bag breaths, but only when it has warm air in it. Wearing clothes will block the heat going to and through the sleeping bag where the air can insulate you and the moisture evaporate. You really should not wear clothing in a sleeping bag. I know it sounds contradictory, but it is pure physics.
If you like wearing something while sleeping, wear a thin merino baseayer. But nothing more than that.
I don't quite agree, water vapor (gas) will tend to go towards lower concentration or lower vapor pressure. While air is the actual insulator it has to be kept in place to work like that or one gets convection losses.
If one is totally wet there is a fair chance that evaporated water will start to condensate inside the bags insulation layer. There just is not much one can do because the dew point mostly is there in cool or cold surroundings. Some of my friends who skied to the north pole said that after a couple of weeks their synthetic sleeping bags were full of ice clumps. Their size apparently slightly varied but they never went away totally.
Anything one wears acts as insulation, better or worse and it adds to the bag's. While it is true that increased temp difference across the bags insulation layer affects the way moisture acts there it also affects the heat loss.
I don't see the physics at all clearcut as different materials act differently but I do find the argument that adding insulation makes one colder slightly strange.
Sorry, but sit down with and do the thermodynamic heat transfer calculations and, in dry conditions (so not trying to evaporate water from clothing), there is no way that it will show that the heat source (your body) will lose heat slower if it has to heat a bigger volume of air further away from the body. Yes. it's the air that insulates you, the clothing just traps it near your body, the less air you heat the warmer you'll be. I had to do heat transfer and dissipation calculations in my work - I can't inverse the physics no matter how I try
The whole myth comes from people getting into bags with damp cloths or poorly wicking clothes IMO.
But, to each their own. Do what you feel comfortable with
Water has a high phase change energy from water to steam(gas), 2415 kJ/kg that tends to be forgotten when people wonder about drying things.I can't inverse the physics no matter how I try
The whole myth comes from people getting into bags with damp cloths or poorly wicking clothes IMO.
You think of your body as a dry stove, but your body loses moist, always. So you trap air AND moist. You need to lose the moist, so you need something breathing. You might get away with wearing clothes in warm weather, but when it freezes, just don't do that. It is potentially dangerous.Sorry, but sit down with and do the thermodynamic heat transfer calculations and, in dry conditions (so not trying to evaporate water from clothing), there is no way that it will show that the heat source (your body) will lose heat slower if it has to heat a bigger volume of air further away from the body. Yes. it's the air that insulates you, the clothing just traps it near your body, the less air you heat the warmer you'll be. I had to do heat transfer and dissipation calculations in my work - I can't inverse the physics no matter how I try
Eat loads,do loads of star jumps,work up a sweat,get into your sleep bag in just a base layer,do it up and lie still.
How warm is it in there now?
Regards
Ray.
How warm is it in there now?
Regards
Ray.
Right but how does one having some clothes on prevent that? You have to show that having a higher temp difference across the bag wall somehow betters the greater heat loss from your body. I think that is a non trivial exercise in thermal and water phase change physics.
Some 50 years of experience disagrees with that, never have been in the polar areas but -35C often enough. So far have all my fingers, toes and ears. Must admit, it was not always warm and fun but easily survivable (with just about all clothes on in the bag).
Isn't this the same reason you don't put your head in your bag when you're sleeping in the cold? It just gets wet in there and when your metabolism slows during sleep everything cools too much and you are enveloped in cold, wet, even freezing air.
One of the fellow jägers tried that, RIP.
Actually he survived after putting his clothes on.Still I would like to have a proper explanation on the heat loss thing ...
Depending on what you mean by "breathing", it is not a well defined term in this context. I also realize that you are not familiar with military sleeping bags 50 years ago!
Hmmm.... not really true, if one has wet clothes, body heat slowly evaporates that into the surrounding airspace, meaning inside the bag. There is just no known process that "breathes" this gas volume out albeit very slowly. Gas concentration irregularities tend to equalize by brownian motion and the bag is actually a hindrance. Besides the evaporation sucks heat out of one's body.
In fact, i was tought to strip down, leave my clothes somewhere dry and sleep in underwear in the army and keep my uzi warm within the sleepingbag. But that was 1995, so i'm old but not that oldDepending on what you mean by "breathing", it is not a well defined term in this context. I also realize that you are not familiar with military sleeping bags 50 years ago!
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