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The Climbing Club • View topic - Locating thermarest hole

The Climbing Club

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 Post subject: Locating thermarest hole
PostPosted: Tue May 05, 2009 10:10 pm 
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Cap'n Wingspan
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So I'm pretty sure there's a hole in my thermarest. I filled it up tonight and put several inches of water in my bathtub and submerged the entire thing bit by bit in the water. I didn't see any bubbles coming out anywhere, so I hung it to dry and went climbing. When I got back about two hours later, it definitely had significantly less air in it than before. After losing that much air in two hours with virtually no pressure on it, I would expect the hole to be big enough to cause bubbles. Any suggestions how I can locate the hole?


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PostPosted: Tue May 05, 2009 10:29 pm 
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Longshanks
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You might try a squeeze bottle with soapy water. Apply pressure to the pad and squirt the detergent wherever you think there might be a leak. Bubbles will form wherever there is one. Obviously this only really works if you have some clue about where the leak might be. e.g. seams, valve, etc. You probably don't want to cover the whole thing in bubble soap!

The other alternative is to just use a closed-cell foam pad. I'm a convert. They're 1/2 the weight, and an 1/8th the cost for similar or greater insulation value.


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PostPosted: Tue May 05, 2009 10:30 pm 
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Cap'n Wingspan
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yeah, I thought about the soap, but as you surmise, I don't especially want to cover the pad in an entire bottle of liquid soap. how do the closed cell foam pads compare in terms of comfort?


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PostPosted: Tue May 05, 2009 10:47 pm 
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Longshanks
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They are definitely a bit less cushy. There is one situation where they can actually be more comfortable, however. Being wider and less slippery than the inflatables, they overlap well. No cold spot between you and your lady! :mrgreen:

I've taken to using two pads: A short 1/2 length section of folding foam (ridgerest), and a full-length blue foam roll-up. The former doubles as a framesheet for my pack and as an emergency pad. I think the two together are warmer than any inflatable Thermarest, almost as cushy, and still weigh less... even if you don't consider that the pack frame I replaced with the pad was heavier than it is.


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PostPosted: Wed May 06, 2009 8:59 am 
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experienced hiker of the climbing club
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The other option is to just bring the leaking thermarest in to Cascade designs. I had a phantom leak that they patched up good as new for about $25.


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PostPosted: Wed May 06, 2009 10:23 am 
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giving spoon
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I would highly recommend a closed cell pad such as the ones pro mountain sports sells. Last summer Jon T. turned me on to these and I have loved mine ever since. Plus if it gets trashed on a trip, I'm not out that much money. The only draw back is they are bulky, but they are immune from springing a leak!

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PostPosted: Thu Apr 22, 2010 12:43 pm 
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Closed cell foam pads are much warmer than self-infalting airpads, as airpads are nylon and open cell foam and air, where none of these is nearly as thermally insulating as closed cell foam. Like Obadiah I use 2 layers of closed cell foam for adequate comfort. One full length pad and one half-length pad.

Inflatable pads with slow leaks make very poor leg splints (learned in Wilderness First Responder class).


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PostPosted: Thu Apr 22, 2010 1:00 pm 
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If you happen to have one around, stethoscopes are really handy for finding leaks-you can hear the hissing from even small leaks once you're nearby. It might take awhile to cover a whole thermarest with a stethoscope, though.


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PostPosted: Thu Apr 22, 2010 1:12 pm 
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The Pub Czar
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PostPosted: Thu Apr 22, 2010 8:34 pm 
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Dr. Crevasse
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PostPosted: Thu Apr 22, 2010 11:48 pm 
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Longshanks
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Yeah. If you can believe the manufacturers numbers, then the newest generation of inflatable pads easily beats foam for the relevant figure of merit: R*cm^2/g



MSR Prolite Plus: ~50 R*cm^2/g

Evazolite Zote Foam Extra: ~30 R*cm^2/g

Not knowing how the R-values are measured (beyond the physical definition Jim mentioned), it could be that there are important devotions from these numbers in practice. For example, the inflatable pads may loose more of their insulation from body pressure (they are softer!) than the foam ones do...


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PostPosted: Thu Apr 22, 2010 11:58 pm 
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Those Z-lite pads sure look slick in the stores. I guess my mind doesn't consider them when I'm talking about closed cell foam pads. I'm either referring to 9mm blue pads or 14.5mm yellow pads. The 9mm foam has a higher R-value than the best self-inflatable. The yellow? It's pure love. The Z-lite has a very very thin thickness of foam so a very low R-value. The thin foam is formed into convexities and concavities which helps provide some extra cushion but those gross air pockets do not increase the R-value of the thin foam. I view the Z-lite as a very light concept for Summer sleeping. But even in Summer I use 2 [normal thickness] foam pads for cushion comfort.

I seem to believe that per unit mass the 9mm and the 14mm foam pads have a higher R-value than self-inflating pads, but that's mostly just my strong hunch.


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PostPosted: Fri Apr 23, 2010 8:10 am 
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Dr. Crevasse
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Where are you getting your numbers? The data from MEC:
(15 mm thick): 29.4 R*cm^2/g
(1 cm thick): 47 R*cm^2/g

If you have different numbers from elsewhere I'd love to see it.

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PostPosted: Fri Apr 23, 2010 9:52 am 
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Most interesting. Jim found on the Therm-a-Rest website [Cascade Designs] a published R value for the Z-rest of 2.2

I just found on the MEC - Mountain Equipment Co-op website a published R value for their 15mm foam [Evazote] pad of 2.06

I suspect there must not be a rigorous standard for measuring R values for sleeping pads. I can plainly say that the extra thick 15mm yellow pad is far far warmer than the Z-rest. I know this from personal experience this winter, both pads used as sit pads for lunch stops while snowshoeing. I also used the 10mm blue pad [R value 1.36 from MEC website]

This reminds me of sunscreens' claims before a single [scientific] standard was erected and enforced by law (rule, act, whatev). Before the "SPF ratings" the consumer really had no way to accurately compare manufacturers' claims. Even within one manufacturer's line of sunscreen products the consumer didn't know what they were using except that "maximum" was likely a better UVB blocker than "strong" and "dark tan" was likely less strong than "moderate." What is needed in this realm is UVA blockers (aside from the opacity of titanium dioxide) as it's UVA energy that causes cancer; UVB energy causes "sun burn" but that's an actue nearly trivial concern when compared with chronic DNA insult to dermal cells resulting in mutations that may become carcinomas or worse yet, melanomas. The "sun burn" is a "canary in a coal mine" but is not directly linked to the DNA mutation caused [primarily] by UVA energy.

My personal experience with "light weight" self-inflating pads begins and stops with the near original technology, the only product [I can remember] was standard width, I think it came in 3/4 length, the shiny nylon fabric was rust colored, this was early 80s. It was heavy, not warm, and terribly slick. I know they were around in the 70's but that was a different beast, those were about 1 1/2-inch thick and the exterior fabric was ridiculously heavy. My dad had one of these and I remember when he asked me to roll it up.


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PostPosted: Fri Apr 23, 2010 3:40 pm 
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Tenacious Lee
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Perhaps the problem is that the R-values for inflatables is measured without any pressure (that is, someone lying) on them? If that is the case then you would certainly feel colder than the published value on the inflatables.


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