Re: [Hammock Camping] Re: "Staying Warm" in Hammock Weekie
- Dave Womble wrote:
>Hey guys,Cool! err... Hot!
>I looked at R-values for closed cell foam pads last January. One of
>the few closed cell foam pads with solid surfaces that I could find
>manufactures specifications on was the Link Rest by Cascade Designs
>and I am assuming that other solid surfaced closed cell foam pads
>that have a density between 1.5 and 2.0 pounds per cubic foot have an
>R-value proportional to the R-value of the Link Rest, which is 1.9
>with a thickness of 7/16 inch. That would mean that a quality 3/8
>inch closed cell foam pad would have an R-value of about 1.6.
>I contacted Cascade Designs and asked them about their R-value
>tests. I was told that they use flat plates to equally weight the
>pad under test over its entire surface area. To me, this means that
>the self inflating pads test higher that they perform because we
>don't load them equally-- we collapse the pads significantly in the
>areas of our greatest weight, our butts for instance. It also means
>that we have to be careful how we use the closed cell pads with large
>open surface cells, i.e. the Ridgerest, Z-rest, convoluted pads,
>etc. These pads are intended to be used against air-tight surfaces
>on both sides; if that condition is not meet I think the R-value will
>be determined by something in between the minimun and maximum
>thickness of the pad. This is a concern to me when one side of the
>pad is placed against the breathable material of a hammock.
>Anyway, I thought I would throw that out there since the subject came
>up... it is what I figured out and hopefully some of it is right. I
>didn't get to test this out in cold weather because I was in and out
>of town pretty much all of last winter. Since then I have decided to
>try out multiple 3/8 inch REI blue pads but haven't had them in
>temperatures much below freezing.
One thing I did learn when I was looking up info on what the value might
be was that 3 1/2 in fiberglass batting has an R value of 11. So to my
little mind, 4 in of down probably has about the same. Empty vertical
spaces from 1/2 to 4 inches have only an R value of 1. Part of that may
be because it is vertical. Horizontal may do better. Nevertheless, it
is important to fill up those empty spaces with micro convection systems.
BTW, my calculation came from taking a value here:
Specifically the foamed in place polyurethane, and multiplying 6.25 x
3/8. The actual answer is 2.3. But I did not take into consideration
weight being applied. If I assume that the 3/8 pad is compressed to 1/4
inch, then the calculation is 1.56 which is what Bear mentions above.
All of this helps explain to me why I have the impression, with my
overlap pad, that it is much warmer than a single pad. In the most
compressed part of the pad, the central 8 or 9 inches, I have an overlap
of two pads.
When you come to a conclusion please let me know. I am curious. Thanks, Marsanne
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Anyway, I thought I would throw that out there since the subject came
up... it is what I figured out and hopefully some of it is right. I
didn't get to test this out in cold weather because I was in and out
of town pretty much all of last winter. Since then I have decided to
try out multiple 3/8 inch REI blue pads but haven't had them in
temperatures much below freezing.
--- In email@example.com, ra1@i... wrote:
> Hi Bill,
> Replies in line...
> Quoting Bill Fornshell:
> > Hi Risk, A lot of people talk about using the Target
> > "Blue Closed Cell Pad." Do you have any idea what the
> > "R" value of this pad is?
> About the same as the RidgeRest, or a bit less... Ridge Rest is
> calculated the Target pad at something like 2.5. I will see if
> says, though I doubt it.
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