/ PRODUCT NEWS: Alpkit Numo Self-Inflating Mat
Read more at http://www.ukclimbing.com/gear/news.php?id=2994
I've read some very good reviews on backpacking sites of a very similar looking product from a US firm (Pacific Gear? Something like that), one chap saying it was better than the new fancy thermarest version - Neoair is it? I'm normally quite good at seeing the basic design logic of camping and climbing gear - but I can quite get my head around why you need insulation inside an air mattress once its full of air.
Anyway - as I get older, comfy looking mattresses look ever more attractive so had been quite tempted by one of these!
>.... I'm normally quite good at seeing the basic design logic of camping and climbing gear - but I can quite get my head around why you need insulation inside an air mattress once its full of air.
> Anyway - as I get older, comfy looking mattresses look ever more attractive so had been quite tempted by one of these!
As I understand it, the insulation in the Exped versions is to prevent the air circulating and the cold air from the bottom of the mat replacing the warm air at the top (which you will have warmed up with body heat).
How effective it is I don't know. I assume it would be more effective than having insulation in just one area - but how much of a difference you would notice, I have no idea!
Hopefully someone with some first hand experience will be able to give some more accurate info.
Is it self-inflating or not? The blurb and title seem a bit contradictory.
Says on the Alpkit website that is't not self inflating.
> I'm normally quite good at seeing the basic design logic of camping and climbing gear - but I can quite get my head around why you need insulation inside an air mattress once its full of air.
For the same reason you wear a down jacket instead of a baggy windproof with tight cuffs... circulating air very effectively transports heat from you to a heat sink (the ground or atmosphere), and consequently air beds are freeeezing....
Please ignore Col's gaff, the Numo is not self inflating.
Lets say the air mattress is 5 cms high, I could well imagine that the air in the upper cm or two could be much warmer than the air in the bottom cm or two if that is against cold ground or snow for instance, but why would there be any more convection or conduction happening inside there than inside my 2 cm thick thermarest?
I'm still thinking about this, but slowly as you can see... :-)
Isn't your example a false analogy. A baggy windproof is an uninflated Numo. The down jacket (available at a very reasonable price from the good folk at Alpkit!) has the down in it basically to give some structural integrity to the jacket, meaning that the air is trapped between the inner and outer layers. Would an inflatable jacket not work just as well?
I presume not otherwise people wouldn't shell out for down and ducks would have large air filled sacks instead of feathers.
I don't know the full science, I guess it is greater chance for convection, but can certainly confirm that the coldest I've ever been when camping was in September on an air bed. (Compare that to thermarest or whatever in Feb in the hills)
You thermarest, or a foam mat (or down jacket, or cavity wall insulation) hold isolated pockets of air between which heat must conduct, meaning that the temperature gradient between inside and outside is very gradual. There will inevitably be air circulation in an air mattress due to factors like your movements and uneven heating of the top surface, and we can probably model the air as being well mixed rather than a stable inversion-style layer. In this case there are only two conducting interfaces compared to the dozens or more in q foam or down: between you and the mat, and between the mat and the ground. Assuming the air inside is mixing, you immediately have a best case scenario of the mat being the average of your temp and the ground, I.e. a very steep temperature gradient. Try it and see - a pool lilo or a cheap ribbed camping mattress are noticeably Baltic...
I have the exped synmat, similar to the Numo, i find it much comfier, just as light, warmer and a lot cheaper than a thermarest prolite.
For example, when you lie on and compress a mattress, the less compressed bits at the end will be slightly uphill from the bit under your body, so warmed air will flow to them, creating a convection current.
Blowing it up is a bit of a pain, but doesn't take long. I've heard someone say it takes only 8 breaths but they must have bigger lungs than me!
I bought an Alpkit wee airic as an upgrade to my old karrimat that I am finding too uncomfortable as I get older but tbh the wee airic is still too thin. The numo looks ideal but I would have prefered insulation under the legs as well. The extra fill would have weighed very little.
I understood "upper portion" to mean "the side of the mat you sleep on"
The Pacific Outdoor Ether Thermo mats have insulation the whole way down, and weigh about 620g whereas the Alpkit mats have about half the insulation and are 470g. Pacific outdoor make mats with even more localised insulation which gets weight down to only 396g.
I too wanted full insulation and the weight wasn't too big a deal, so I got the pacific outdoor thermo mat. They're only £30 as well, instead of £40 for the numo.
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