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Main Boards => Gear => Topic started by: Islandplodder on 13:11:48, 21/06/20

Title: Sleeping bag liner
Post by: Islandplodder on 13:11:48, 21/06/20
I have been thinking that I might have to go back to camping given the times we live in, but being small and getting on a bit, I really need to keep the weight down. My current sleeping bag, though good in many ways, is heavier than my new tent.
Someone suggested that if you use a liner, it almost made the difference between say a 2 and a 3 season sleeping bag, and would be a lot lighter. Has anyone any experience of this, or is it a marketing ploy for sleeping bag liners?
Title: Re: Sleeping bag liner
Post by: forgotmyoldpassword on 13:35:20, 21/06/20
Doesn't add more than a few degrees but sometimes that is all you need, but the value is more keeping the oils from your skin off the down in the bag - which makes it last longer and require fewer washes.


I don't tend to bring it for winter use but for summer when it's sticky humid conditions a liner and unzipped bag seems worthwhile.  Make sure you get a decent sleeping pad though as nothing makes you colder on a night than losing heat directly to the ground.
Title: Re: Sleeping bag liner
Post by: SteamyTea on 13:51:27, 21/06/20
I have been thinking that I might have to go back to camping given the times we live in, but being small and getting on a bit, I really need to keep the weight down. My current sleeping bag, though good in many ways, is heavier than my new tent.
I have the same issues.
I have a 300gsm bag that is pretty good, but does not compress too well and is weighty.
I also gave a very cheap 200gsm bag that is light and compressed well, so might try taking two of those as the total mass is probably less.


I also dislike 'hoods' on sleeping bags, can't see the point for the type of weather I would camp out in.
And 'mummy' bags are are just horrible.


Also worth knowing that there are two things that affect the thermal performance. The thermal conductivity, which is how fast and at what power the material looses energy.
Then there is the thermal capacity, or how much energy the material stores.
As a general rule you can have one but not the others. There are exceptions, but no-one likes a damp sleeping bag.
Title: Re: Sleeping bag liner
Post by: ninthace on 15:23:39, 21/06/20
Don't forget the unalloyed pleasure of waking up to find you have turned over a few times in the night and so has the liner but (k)not the sleeping bag.  Then you have to work out how to unwind yourself and the liner before you can emerge to greet the day.  Perhaps these days liners have changed since they were just an old sheet that had had an encounter with a sewing machine?
I seem to recall a time when liners were also de rigeur in youth hostels or is that a figment of old age?
 
Title: Re: Sleeping bag liner
Post by: richardh1905 on 19:56:18, 21/06/20
I used a Buffalo fibre pile bag with a fibre pile liner - this served me well just below the snow line in the Alps, but was a wrestle to get in to and escape from.


I'm thinking of making a 'half liner' from an old jacket or whatever, just to cover my legs and feet, as it is my feet that get cold if I am camping in colder than anticipated conditions. Also - wearing clothes in your bag helps - I have in the past packed a pair of light fibre pile trousers for wearing at night whilst wild camping.
Title: Re: Sleeping bag liner
Post by: ninthace on 20:33:43, 21/06/20
I used a Buffalo fibre pile bag with a fibre pile liner - this served me well just below the snow line in the Alps, but was a wrestle to get in to and escape from.


I'm thinking of making a 'half liner' from an old jacket or whatever, just to cover my legs and feet, as it is my feet that get cold if I am camping in colder than anticipated conditions. Also - wearing clothes in your bag helps - I have in the past packed a pair of light fibre pile trousers for wearing at night whilst wild camping.
Now you have stirred a memory.  When I was 16, camping in snow in Switzerand, I stuffed my liner with straw from a barn to make a palliasse to provide added insulation.
Title: Re: Sleeping bag liner
Post by: gunwharfman on 21:35:54, 21/06/20
I'm not keen on liners, I turn over in my sleep and end up looking like a chrysalis!

I've tried two solutions, the first is to wear lightweight leggings, loose socks and to wear one of my warm jackets as sleeping attire, the other solution is that I've cut and sewn a 3' x 4' rectangle from an old down sleeping bag and it just clips to the inner torso area so I'm covered by two layers of warmth.

I am also hoping that my recent purchase of a Brynge 'string vest' might help as well, I can see me wearing that in the night and wearing one of my warm jackets as well.

I also find it useful sometimes to wear my lightweight gloves and my lightweight beanie as well.

Of course, the other factor to consider is, the mattress you sleep on, how good is it at keeping the ground cold from your body?

I have yet to decide though which system I will stick with. Lockdown has scuppered everything I wanted to test and do this year.
Title: Re: Sleeping bag liner
Post by: SteamyTea on 22:49:28, 21/06/20

Of course, the other factor to consider is, the mattress you sleep on, how good is it at keeping the ground cold from your body?
Other way around.
Heat, of itself, cannot go from the colder to the hotter.
https://youtu.be/VnbiVw_1FNs
Title: Re: Sleeping bag liner
Post by: RMR on 04:04:57, 22/06/20
I use a Rab Silk liner for the cooler months and find that it does make a difference. Also like the feel of it.
Title: Re: Sleeping bag liner
Post by: GoneWest on 07:17:30, 22/06/20
Other way around.
Heat, of itself, cannot go from the colder to the hotter.
https://youtu.be/VnbiVw_1FNs (https://youtu.be/VnbiVw_1FNs)


True but, by way of analogy, even scientists and engineers talk of electric current flowing from positive to negative when they know that the actual electrons go the other way.
Title: Re: Sleeping bag liner
Post by: Bigfoot_Mike on 07:53:59, 22/06/20


True but, by way of analogy, even scientists and engineers talk of electric current flowing from positive to negative when they know that the actual electrons go the other way.
True, but the holes travel in the opposite direction.
Title: Re: Sleeping bag liner
Post by: SteamyTea on 08:57:55, 22/06/20
True, but the holes travel in the opposite direction.
I was once shown a great demo of how electrons move between home.
I quickly copied it by hand, no idea where it is now.  Probably in my loft with my other college notes.
Title: Re: Sleeping bag liner
Post by: GoneWest on 11:22:18, 22/06/20
True, but the holes travel in the opposite direction.
Just like the cold, to complete the analogy and return vaguely in the direction of the topic.  :)
Title: Re: Sleeping bag liner
Post by: gunwharfman on 14:46:26, 22/06/20
What I was trying to suggest is that a mattress like my NeoAir also helps me to keep warm. If I lay directly on a cold floor, even in a sleeping bag I believe I will get cold fairly quickly. An insulating barrier, e.g. newspapers placed between my body and the cold floor will delay how long it will take before I feel cold. If I lie on a camp bed and the sleep-on material is 6" above the ground and the air is cold between the bed and the ground and I am just in my sleeping bag, I believe I will also get cold fairly quickly. However, if lay my mattress (inflated or not) or newspapers on the top on the camp bed material and then lie on it in my sleeping bag, it is my experience that I will not get cold for at least the duration of one 'normal' sleep period.

Am I correct or is my personal experience of being cold and then solving it in the way that I have done due to something else?
Title: Re: Sleeping bag liner
Post by: richardh1905 on 16:10:18, 22/06/20
What I was trying to suggest is that a mattress like my NeoAir also helps me to keep warm. If I lay directly on a cold floor, even in a sleeping bag I believe I will get cold fairly quickly. An insulating barrier, e.g. newspapers placed between my body and the cold floor will delay how long it will take before I feel cold. If I lie on a camp bed and the sleep-on material is 6" above the ground and the air is cold between the bed and the ground and I am just in my sleeping bag, I believe I will also get cold fairly quickly. However, if lay my mattress (inflated or not) or newspapers on the top on the camp bed material and then lie on it in my sleeping bag, it is my experience that I will not get cold for at least the duration of one 'normal' sleep period.

Am I correct or is my personal experience of being cold and then solving it in the way that I have done due to something else?


I've never just slept on the ground; I have always used a mat of some sort, any mat, even a cheapo closed cell mat, will make a huge difference. Normal practice.
Title: Re: Sleeping bag liner
Post by: SteamyTea on 17:21:07, 22/06/20
Thermal losses happen 3 ways, conduction, radiation and convection.
Conduction is reduced by insulation.
Insulation is really a combination of a material with a high thermal resistance and small pockets of air (or other gases, and even no gases in the case of vacuum insulation) trapped between whatever material the insulation is made from.
This reduced the movement of the air, which reduces convection.
Air also has a fairly high thermal resistance.
The SI unit is kelvin meters per watt, R = K.m/W.
It is more usual to use the reciprocal 1/R, which has the SI units watts per metre kelvin, λ = W/m.K.
Air has a typical value of 0.0255 W/m.K, polyester has a value of 0.05 W/m.K.
Polyester and paper conducts at about twice the rate of air, 0.05 W/m.K.
Cotton conducts at about ten times the rate of air, 0.23 W/m.K.
Dry earth is even worse 1.5 W/m.K, 60 times worse, and is, in effect, an infinite heat sink.


As you cannot realistically change the ground temperature, or your body temperature, all you can do is increase the thickness of the insulation.
As clothes and sleeping bags compress when laid on, it is therefore best to use an inflatable mattress as this will drastically reduce the losses.
Title: Re: Sleeping bag liner
Post by: Bigfoot_Mike on 17:59:01, 22/06/20
Still air is a good insulator. It is what makes our clothes feel warm and provides a lot of insulation to animals, trapped in their fur. It is also what makes double glazing work.  A camp bed doesn’t constrain the air and allows the air to circulate, so may not be as effective as the mattress.


Explained in more detail by Steamy Tea above.
Title: Re: Sleeping bag liner
Post by: gunwharfman on 17:59:45, 22/06/20
I once slept directly on the ground, I was a student, it was in Austria and I was drunk. I fell asleep, the drink made it possible but I woke up very soon freezing! I had a dreadful night, never repeated the experience since!

The nearest to it was last Nov 10th when I thought I would sleep in my car, I felt lazy and couldn't be bothered to organise my gear. I thought I would just wrap my quilt around me, recline the seat, and doze. was cold very quickly so I had to make the effort to make my bed properly. I blew my Neo Air up and then slept well.
Title: Re: Sleeping bag liner
Post by: SteamyTea on 18:19:20, 22/06/20
I once slept directly on the ground, I was a student, it was in Austria and I was drunk. I fell asleep, the drink made it possible but I woke up very soon freezing! I had a dreadful night, never repeated the experience since!

The nearest to it was last Nov 10th when I thought I would sleep in my car, I felt lazy and couldn't be bothered to organise my gear. I thought I would just wrap my quilt around me, recline the seat, and doze. was cold very quickly so I had to make the effort to make my bed properly. I blew my Neo Air up and then slept well.
I had my car break down in rural Oxfordshire a few years back.
It was -3°C.
I was so cold I thought I was going to die.
Title: Re: Sleeping bag liner
Post by: Birdman on 11:19:25, 23/06/20
I'm using a silk liner.


It adds some extra warmth, but not much. Main advantage for me is that it keeps my (expensive, down) sleepingbag more clean. I do lots of long-distance walking where you often cannot wash yourself properly for weeks on end, so it is nice to have a liner that is easy to wash/ rinse and dries fast (and you can do so while on the trail).


Another thing that I like is that it makes your sleeping system more flexible. If it is warm, I just sleep in the liner.


An last but not least, I like the feeling of silk on my skin. Really an A+ sleeping experience on the trail!
Title: Re: Sleeping bag liner
Post by: Birdman on 11:27:59, 23/06/20
What I was trying to suggest is that a mattress like my NeoAir also helps me to keep warm.


Indeed! The mattress is so important to keep you warm. So much heat is lost through the ground.


The NeoAir is excellent. I have both the Xlite and the XTherm. Xtherm is my favourite, if I had to buy only one. You'll be nice and warm even when sleeping on solid frozen ground. But I have used the Xlite at -3°C and wasn't cold.