Thin closed cell foam worthwhile addition?
Hi again all, Many thanks for the help with TVP sources in Auckland a few months ago for the trip I'm planning. FWIW I ended up going with a mixture of mashed potato flakes, couscous and nuts -- good nutritional profile, cheap, very low weight and volume, makes up with minimal cold water in minutes (I have to carry my water on this trip), and I even like the taste (for a few nights)! Hadn't thought of couscous till I saw it in the thread so thanks to whoever posted that. Originally the trip was planned for April but I had to put it off so will be doing it sometime in May now. I'll be in Central Otago during a selected window of fine weather so it could well be frosty overnight. Historical data over the past 6 years show temps down to -4 but more often around zero or even a bit above. I'll have two (rented -- good quality) self-inflating sleeping mats lashed together so my old hips won't touch the ground (have tested this) and when the trip was planned for April I figured these plus a warm synthetic sleeping bag (also rented) and survival blanket bag inside with clothes on, would be enough. However I'm starting to wonder if that also holds for a May trip since I feel the cold and will need to sleep well. I have a thin closed-cell mat and am wondering about lashing it to the top of the sleeping mats, to further insulate me from the ground. It's only 7 mm thick; I don't know for sure what the mats measure but I'd say 2cm or perhaps 2.5 at a stretch so 4-5cm thick in total. Weight and space are at an absolute premium on this trip -- is it worthwhile taking the foam mat or not? Is something that thin going to make much of a difference?
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errr, sweat pants? as in fleecy cotton track pants? Maybe I have the wrong end of the stick, but just in case you are taking cotton pants .... Cotton is a disaster when wet - not even much good in a cold wind when dry. Even for use just for inside the tent, they aren't worth the weight - wool, polypro/microfleece or similar would be much better. Take two pr microfleece - one for day and one for tent (if one gets wet you have a fallback). Geeves, I disagree re CCF on top being better insulation. From a thermal transmission point of view, the order doesn't matter. However, inflatable mats partly rely on your body heating the air in the mat - if the CCF is between you and the mat, the air doesn't warm up.
I've mentioned this in another forum but I read somewhere that if you put the CCF on top of the inflated mat, you'll stay warmer as the air in the mats gets cold due to the ambient air temperature but the CCF won't get as cold. I've yet to experiment with the idea however...I've always put the CCF against the snow when bivvying out to insulate the inflated mat against cold being transferred from the snow. Food for thought anyway.
OK, I need to explain a few things. Number 1, I'll be choosing my weather window, so rain (and even wind, fingers crossed) is extremely unlikely. Number 2, I'll have waterproof gear with me. Number 3, I'm not tramping, I'm cycle touring. So, no river/stream crossings. Number 4, this is a tour I've done multiple times. The sweatpants will be just fine :-) But thanks for the concern :-) Interesting point about where to put the CCF, though. Need to think a bit more about that...
Bubble wrap. Mitre 10. Seriously. I know people who have tried it. Tho, mylar bubble wrap will probably cost you the same as a top quality neo air (which you could re-sell afterwards ?). https://www.youtube.com/watch?v=ojrR0tdaGUw https://i.ytimg.com/vi/ojrR0tdaGUw/maxresdefault.jpg http://i.imgur.com/YYdoP0A.jpg
yeah. the missus uses kingspan aircell - foil-backed construction bubblewrap. Good moisture barrier with a bit of R (1.5). About the same R as thin foam but much lighter weight and packs smaller.
I was grabbing this stuff from the hospital for free for ages and giving it away! It was used to pad some cardio lab equipment. I didn't realise it had such a good R rating.
Yes, honora, I've read similar comments before too but just the comment and not any attempt to explain why. Perhaps I should qualify my previous comment somewhat as there are two possibilities. If the various mats are basic self-inflating mats (ie construction is basically trapped air and holed foam) then the order doesn’t matter - total R-value is just the sum of each. This is solely thermal conduction. However, I think comfort would dictate not having the CCF on top. If, however, any of the mats are of more recent design and have an internal reflective layer, then the warmest configuration is to have the reflective layer mat on top so that heat is reflected back to your body. This will also maximise warming of the air space above the reflective layer with obvious benefit. This is a combination of thermal radiation and thermal conduction. Either way, the CCF is better not on top.
Klymit Insulated Static V. With a -16 degree DriDown bag. If really cold, thermal liner added. Completely toasty. Given how restless I often sleep, if I lashed even two mats - any mats - together, I'd somehow manage to slide them apart from each other, and I'd end up on the ground. Actually, now that I think about it, this has happened to me. Sleeping on concrete in a shelter in Autumn. It sucked! I would add my voice to the previous suggestion of trying to get a better mat.
Thanks for the analysis bernieq, will bear that in mind. The mats look pretty new so perhaps they do have a reflective layer in them. I'll try with the foam on the bottom -- I can always change and try it on the top!
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