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?
On a recent trip to Annette Plateau at Mt Cook I camped on snow using a small tarp under my tent, then my air mat on top of a foam mat. Worked perfectly fine, didn't feel the cold coming through the floor at all. For a bit of extra insulation you can always spread your raincoat and rain pants out (if they're dry) and put your mats on top. Every extra layer between you and the ground helps.
This is great info for calibrating Yarmoss, thanks so much. And I will have a groundsheet under the tent. And what a good idea to use my coat and overtrou! I love double-use items :-)
At the risk of going over old ground, do you really need two inflating mats? On snow, I've used a closed cell foam (CCF) mat and a self inflating mat on top of that - works for me. What brand/model are the mats? You're renting them so maybe you can improve on the R-rating and have one mat that indulates better than the two together. Eg a neo-air or exped or (quite a few, really) have much beter rating than a prolite or similar. BTW, insulation value of tent floor = groundsheet = rain jacket/pants = only marginally more than zero. They'll help keep you dry (a good thing) but not insulate from the ground. CCF has air trapped throughout the foam matrix, making an effective insulator. That's how the mats work, too.
Thanks bernieq. Yes, I do need two mats :-) I don't know what the model/brand is (didn't bother to write it down when I had them for testing) nor the R-rating, for that matter, and I'm not prepared to buy anything for a 5-day one-off trip. What thickness is your CCF?
Does the shop you are renting from not have newer design mats? My exped is 10+ cm thick when inflated, as are similar mats - and not any more weight. I'm suggesting renting a better mat :) (... or resolve to do more tramping to justify buying a new mat :)) One (better) mat would cut down the bulk, the weight and give better insulation and more comfort. My CCF is 12mm (I also have some 8mm stuff which would still be useful) - I'd advise taking it. BTW - if you carry the CCF on the outside of your pack, put it in a bag - almost every tramp, I pick up bits (of other trampers' mats) ripped out by passing bush. Also BTW, I put my jacket around the end of my sleeping bag (as Yarmoss says 'if it's dry') to keep off any condensation from the tent. Best, though, if it's minus 2deg - everything is dry !
Not sure of the science but I always use one of those silver foil survival sheets as a ground sheet. It packs down super small and light and is as cheap as chips. I have an exped mat with synthetic insulation and always been warm in a tent in winter on the tops. Though I have a very good exped sleeping bag as well. I just wear all merino. Beanie, long sleeve, long johns with wooly socks. Merino gloves can help too. My two cents.
thickness of a mat isnt directly proportionate to its insulation value.. thats why R value helps, it depends on how the mat is constructed inside and what its made of, the more layered compartments and the more insulation material in it, generally the better. closed cell foam is very good for insulation...
Ive always wondered about the close cell foam on top of an inflatable mat. My mat has only a reflective inner as insulation but at 300g for most uses the trade off is worth it. I dont very often get the chance to sleep on snow but everything less than that its been fine. Putting a closed cell mat on top of the inflatable will give better insulation but keeping it on top could be fun. How much worse would it be underneath?
I'll be lashing the inflatables together, so adding the CCF into that will be a piece of cake. I fully expect them to all stay together no worries. The CCF has no compartments, it's 'solid' foam all the way through (feels strange saying solid about something that's soft) so I guess will be a good addition. Think if southerlies are predicted I'll add it to the list -- 300g extra might well be worth it. I'll also add in a merino top (will also have 2 poly layers top and bottom) and microfleece legs (Swazi -- this stuff is so good that when you put it on you'd swear it's a heater). Will have sweatpants, microfleece sweatshirt, microfleece t-shirt, wooly hat, poly gloves, wool sox...should be OK. Thanks everyone :-)
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