Mon 14 Jan, 2013 9:01 pm
Rob A wrote:Ent wrote:... that the air is for comfort ...
Not really.
Unless you are rewriting the laws of thermodynamics, emissivity plus reflection = 1, and . Aluminium is about as good as it gets. Unless you are the space program or bugatti.
Air is a good conductive barrier.
That is why in theory one of the best insulators is two layers of aluminium foil separated by a millimeter of air. Radiant> conductive> radiant barrier. Unfortunaltely it is not all that easy to achieve.
In practice the introduction of rigid foams etc is for mechanical stability and fabrication.
Neoirs are essentially providing air separated reflective foils.
Mon 14 Jan, 2013 9:14 pm
Mon 14 Jan, 2013 9:40 pm
tasadam wrote:wayno wrote:crap in the cold
2.5-inch thickness can't be too crap in the cold... I don't have one so cannot comment.
The review rates it as the second warmest out of 17 mats. And it's tapered which may assist the OP.
Mon 14 Jan, 2013 10:00 pm
tasadam wrote:Depends on which measurements you go by, my translation is 4 centimetres overlapping on each mat at the 183 centimetre mark.Onestepmore wrote:So at the 180 cm mark you're going to have 7.5 cm overlapping on each mat?A valid point not related to this topic, but as I walk usually with my wife, it would be great if the two expeds clipped together so as not to allow the creation of a gap between us through the night (that I invariably end up in).Onestepmore wrote:PS Hubby just came in with his 2c worth. He reckons it's more important that the mats stick together, than if they fit.
Mon 14 Jan, 2013 10:15 pm
Onestepmore wrote:tasadam wrote:Depends on which measurements you go by, my translation is 4 centimetres overlapping on each mat at the 183 centimetre mark.Onestepmore wrote:So at the 180 cm mark you're going to have 7.5 cm overlapping on each mat?A valid point not related to this topic, but as I walk usually with my wife, it would be great if the two expeds clipped together so as not to allow the creation of a gap between us through the night (that I invariably end up in).Onestepmore wrote:PS Hubby just came in with his 2c worth. He reckons it's more important that the mats stick together, than if they fit.
This is bugging me. And I'm a Scorpio, so that matters.
Ok - width of tent is 85 cm (at 180 cm down measured from the top/head)
Width of each mat is 50 cm - so x 2 = 100 cm
100 cm - 85 = 15cm overlap
My maths is wrong
So I am wrong in saying it's 7.5 cm overlap, and I can't work out where your 4 cm overlap comes from
Hubby and I have just been playing with pieces of paper, and he was right (of course)
This would be sligthly more at 183 cm down, and exaccerbated if the sleeping mat wasn't up hard to the top of the tent wall
tasadam wrote:The width of the tent at a point 183cm from the front door is about 92 cm wide.
Mon 14 Jan, 2013 10:47 pm
Tue 15 Jan, 2013 12:05 am
Onestepmore wrote:How can it be 92 cm wide 183 cm from the front door, if it's 85 cm at 180 cm? It's tapering, ie getting narrower as you go futher down, not wider!
And overlap doesn't halve the amount...
so, as per the measurements taken in the Macpac shop, the numbers are approximate.Attached is the back-of-the-envelope dimensions my partner took with a tape measure and the tent set up (indoors in our lounge - so not guyed out with tension in the fly but would this affect the floor footprint?). Also because of the 'bathtub' floor it's hard to measure EXACTLY
Tue 15 Jan, 2013 7:42 am
tasadam wrote:wayno wrote:crap in the cold
2.5-inch thickness can't be too crap in the cold... I don't have one so cannot comment.
The review rates it as the second warmest out of 17 mats. And it's tapered which may assist the OP.
Tue 15 Jan, 2013 7:45 am
Onestepmore wrote:How can it be 92 cm wide 183 cm from the front door, if it's 85 cm at 180 cm? It's tapering, ie getting narrower as you go futher down, not wider!
And overlap doesn't halve the amount...
Tue 15 Jan, 2013 8:43 am
Strider wrote:[quote="Onestepmore"
And overlap doesn't halve the amount...
Tue 15 Jan, 2013 10:09 am
Tue 15 Jan, 2013 10:56 am
ryantmalone wrote:they have a layer in the middle that reflects the cold down (slowing snow melt on the ground), and that reflects your body heat upwards, back to your body.
Tue 15 Jan, 2013 10:58 am
Onestepmore wrote:Strider wrote:[quote="Onestepmore"
And overlap doesn't halve the amount...
Starting with 8cm extra width, move each mat 4cm inboard and what are you left with? A decrease in width of 8cm.
The taper thing does not add up though, you're right.
Tue 15 Jan, 2013 10:59 am
Son of a Beach wrote:Technically, cold cannot be reflected.
Tue 15 Jan, 2013 11:09 am
Tue 15 Jan, 2013 11:18 am
Strider wrote:Son of a Beach wrote:ryantmalone wrote:they have a layer in the middle that reflects the cold down (slowing snow melt on the ground), and that reflects your body heat upwards, back to your body.
Technically, cold cannot be reflected. Cold is merely the absence of heat. But the heat reflecting upwards, as you said (and the insulation) is what counts.
But it can be insulated against. Insulation is more so a barrier to cold, than it is a reflector of heat.
honey hale wrote:Thanks everyone for all your thoughts/input and for doing so much math!
We are now leaning towards getting a couple of Expeds, either Synmats or Downmats (if we can scrape together the $$ - annoyingly we JUST missed all the local post-xmas sales!) I'm personally not a fan of sleeping on 'blow up' type beds unless they can be made really firm (I sleep on a futon and hate 'regular' springy mattresses) but anything will be better than my old 15-year-old microthin Thermarest!
Whatever we end up getting, we'll take lots of photos of the setup to post on the forum - we're going on our first camping trip here in Oz in a couple weeks
Cheers,
Sharon
Tue 15 Jan, 2013 12:32 pm
Wed 16 Jan, 2013 8:31 pm
wayno wrote:crap in the cold
Wed 16 Jan, 2013 9:03 pm
Son of a Beach wrote:ryantmalone wrote:they have a layer in the middle that reflects the cold down (slowing snow melt on the ground), and that reflects your body heat upwards, back to your body.
Technically, cold cannot be reflected. Cold is merely the absence of heat. But the heat reflecting upwards, as you said (and the insulation) is what counts.
Thu 17 Jan, 2013 7:50 am
ryantmalone wrote:Son of a Beach wrote:ryantmalone wrote:they have a layer in the middle that reflects the cold down (slowing snow melt on the ground), and that reflects your body heat upwards, back to your body.
Technically, cold cannot be reflected. Cold is merely the absence of heat. But the heat reflecting upwards, as you said (and the insulation) is what counts.
Insulated/reflected, same meaning to me.
There's a reason why I never became a scientist.
Thu 17 Jan, 2013 7:11 pm
Thu 17 Jan, 2013 7:37 pm
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