 This might sound like a neive question, but nevertheless it's something I've often wondered. Whenever I see backpackers, be it on tv or out on the hills, they invariably have their sleeping mats strapped to either the top or bottom of their rucksacks. Considering that the majority of sleeping mats aren't waterproof - and the simple foam ones about as absorbent as you can get, what do these people do if it rains?
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| Edited: 23/10/08 20:06 |
 Depends on the type of mat. Open cell foam mats are as good as sponges for soaking up water, but thankfully hardly anyone uses them. Closed cell foam mats won't soak up water, but the surface will need wiping dry if it gets wet. Therm-a-Rest type mats have a fabric surface that will need wiping if it gets wet, but the foam inside can only get wet if you squirt water through the vent. If carrying a Therm-a-Rest outside your pack, you have to be careful not to scuff, tear or puncture it. For my part, I never carry anything outside my pack. It all goes inside, where it's dry and protected. I don't care how much damage the outside of my pack gets, so long as the stuff inside is safe.
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 Foam mats don't absorb water. Edited to say 'closed' cell foam mats. Do you get 'open' cell foam sleeping mats?
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| Edited: 23/10/08 20:18 |
Yeah - you can get the open cell type - though why anyone would want one is beyond me.
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Prior to self-inflating mats coming on the market,We were told on a training course to lie on a mat then mark the length you want it,cut it then stick it your sac let it open out then stick all your kit inside.
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Do you not mean prior to framed rucksacks coming on the market? Using a mat inside a frameless pack, to create a virtual frame, is pretty common. 
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 Yep, then there's the sectional folding type segmented mats too don't forget. Apart from the older type of roll mats, all can go either on, in, or under/to the side of a rucksack as you prefer. Inside the pack though, the argument goes that it is extra padding to your back, and to the pack contents too maybe perhaps!
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Yes Mike, in fact ive still got the old Karrimor in the loft,use it for storage now.It must be nearly 40 yrs old now.
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Do you get 'open' cell foam sleeping mats?
If that question is aimed at me, Mike, then my answer is I have no idea. I was given a self-inflating half mat, but I've no idea if it's foam... open or not 
So how about this? Can I carry this unprotected or not? And how come manufacturers presume that all campers are built like bean poles?
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| Edited: 23/10/08 23:58 |
 Billy, that'll be closed cell and won't soak up water. But that's not the same as not getting wet, of course. The inside of your tent groundsheet won't soak up water either, and do you want that to be wet? To avoid getting it wet either stow inside the pack (not in a tight roll, a very loose one around the outisde edge of the pack with all your gear inside) or just pop a suitably sized binliner over it. Only real downside is it cn rustle in the wind. I've not used a binliner in younger more impressionable times as they don't look Super Cool, but as the Dalek said as it climbed off the dustbin, "we all make mistakes"... Pete.
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 When I take my ancient thermarest, it goes on the inside of my pack for the reasons Paddy mentioned. When I take my closed-cell mat, I usually can't find the space inside my pack! So it tends to go on the outside. It doesn't absorb water and when it has been rained on, it seemed to be pretty easy to dry it off. Pete's idea of a bin liner seems like a good one. Thermarest (at least the original design) used open cell foam inside an airtight fabric skin. That's how it 'self inflates' as the open cell foam expands to its uncompressed thickness. The skin fabric is also watertight so, unless water is getting in through the valve, very unlikely to get seriously wet.
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 If your mat gets so wet that it can't easily be dried, put it under the groundsheet. It'll still do the same job, but it won't wet your sleeping bag. You do have to take a bit more care to 'hit the target', though. And it might get muddy...
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And if you want to move it to sit on then you're a bit snookered too... I think the binliner option is easier, even if it does add Whole Grammes. Pete.
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Billy - that mat is only 1cm thick, surely the 5 season rating (whatever that means) is a bit optimistic. I mean there are 3 season mats thicker than that so don't expect it to be too warm on one of those 5th season nights. It's closed cell so will not wet out but give it a quick shake and put it in your porch for a while and it will dry off quickly. Indeed you could just give it a quick wipe down as the foam should be hydrophobic. At least my foam mats are.
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You could always inflate your bin liner with a bit of helium to compensate...
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I was thinking more along the 'emergency' lines; it's not The End of the World... I'd just take out my multi-purpose flannel and wipe the thing down until it was 'dry enough'...
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Billy - that mat is only 1cm thick, surely the 5 season rating (whatever that means) is a bit optimistic. It looks to me like my old "Expedition Karrimat", which I used throughout the year in Scotland before I picked up a T-rest, but that was mainly for comfort of the hard-ground rather than cold-ground reasons. Not the greatest but they do the job. Pete.
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Thanks, everyone. Some conflicting ideas and opinions there, but all good. I really do need to stop asking questions and get out there instead! I must be the biggest armchair outdoorsman going 
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