Bushwalk Australia

OK - I admit that I skipped all the hard science subjects at school so am not great at physics or even general science. But can someone help me with explaining this. I recently did the Larapinta trail and took along my Ex-ped Downmat. As we were getting into camp early I would be inflating my Exped in the hottest part of the day (around 2pm - about 27 degrees in the tent). Every night at around 3am (also getting towards the coldest part of the night- sub 5 degrees) I would wake up to find my Exped mat flat as a pancake - I would re.pump it and it would be fine until morning. I'm nearly 100% sure it doesn't have any leaks.

What's going on?

warm air takes up more room than cold air. blow up a ballon and put it in the fridge

http://www.historyforkids.org/sciencefo ... rrises.htm

Or maybe one of your walking companions is *&%$#! with your head. That's a pretty funny trick to play on someone actually, thanks for the tip!!

Wouldn't be caused by temp diff only.

Air's getting out somehow.

We had something similar with a SynMat recently (exactly the same set up as the DownMat, only synthetic filling). Ended up testing it in broad daylight to see what was ging on. Testing in broad daylight was unable to replicate the problem. Presume "operator error". ... valve not quite sealing? ... pump part of the mat hadn't been fully infated after the last pump action (squeeze the valve at the pump outlet ... refer to manual), maybe somehow that allowed a slow leakage to occur? ... dunno ...

things got a bit silly while lying around on the mat in broad daylight ... other more incriminatign pics have been destroyed ... ...

It's de-laminated! Stick it in the tub, you'll see multiple bubbles on the surface with no defined source. The fabric layers have separated (invisible to naked eye) and air is moving between layers, then out altogether. This is an ongoing & major problem with all Exped mats (last I heard the return rate was over 10%) but one that Exped seem happy to rectify with a replacement mat - take it back to point of purchase.

N

DonQx wrote:Wouldn't be caused by temp diff only.

Air's getting out somehow.

We had something similar with a SynMat recently (exactly the same set up as the DownMat, only synthetic filling). Ended up testing it in broad daylight to see what was ging on. Testing in broad daylight was unable to replicate the problem. Presume "operator error". ... valve not quite sealing? ... pump part of the mat hadn't been fully infated after the last pump action (squeeze the valve at the pump outlet ... refer to manual), maybe somehow that allowed a slow leakage to occur? ... dunno ...

things got a bit silly while lying around on the mat in broad daylight ... other more incriminatign pics have been destroyed ... ...

What are you doing to that mat, eh????

frenchy_84: warm air takes up more room than cold air. blow up a ballon and put it in the fridge

A more entertaining demonstration (though not quite the same thing) is to get an empty tin can with a lid; for example a big milo tin, put an inch or so of water in it and bring it to a boil on a hot plate or your gas stove for a few seconds and then put the lid on tightly and wait. As the can and contents cool, the water vapour will condense and the can will be crushed by atmospheric pressure.

Or do what a friend did, leave a fully inflated DownMat in the sun.

It popped most of the longitudinal baffles.

Still keeps the air beautifully, but looks a very odd shape.

Can't find a pic at the mo.

Drifting wrote:What are you doing to that mat, eh????

side effects of long-term marriage?

Have a look at my post on this topic and this link . I recon most down mats will go this way as mine did and many have.
http://www.youtube.com/watch?v=EDC_DewtAOk

They develop an internal delamination and then the air seeps out and once that happens , it is not repairable ( I think)
Put it in a bath tub to see if there are any specific leaks . Good luck

scockburn wrote:Have a look at my post on this topic and this link . I recon most down mats will go this way as mine did and many have.
http://www.youtube.com/watch?v=EDC_DewtAOk

They develop an internal delamination and then the air seeps out and once that happens , it is not repairable ( I think)
Put it in a bath tub to see if there are any specific leaks . Good luck

I had the same issue with a normal self inflating mat from pacific outdoor equipment. Was replaced under warranty (twice) before I switched to a thermarest.

scockburn wrote: I recon most down mats will go this way as mine did and many have.

Have used my Downmat 7 for a few years and have several hiking buddies who also have them. None of us have had an issue. Go figure ?

Just checked the BPL reader reviews and the Downmat 7 has 15/16 positive feedback. BPL is generally a good barometer for gear as the community are quick to call out issues with gear.

http://www.backpackinglight.com/cgi-bin ... ble&cid=40

I wonder what happened in Oz did we get a cr*p shipment ?