Hammock Camping Re: First cold night
- Hi Youngblood -
This was actually the first time I had ever used the Reflectix - I just though it might be touch cold(er) 200 miles north of where I was for the night so I added it when packing. I think the 3/8" foam pad is pretty darn effective as I have used it solely after my initial pad experimentations, but I found that without the Reflectix underneath the foam pad in spots I could really feel the cold taht night. So it would be my guess that the Reflectix added a good degree of "warmth" to the hammock. This is probably similar to any other reflective insulation like a windshield reflector or mylar plus a few degrees, but that is just my guess as I haven't used them (only what I had handy). Keep in mind too that the Relfectix was only 16" width or so, so just the "core" of my body was on that area of insulation. I think the hat and gloves make a big difference just like they do any other time. The Capilene probably has neglible insulative value, but the fleece (only on the bottom - the top was a pillow) probably much more so. The quilt is a good one with probably 2" of Polarguard 3D if I remember right, altough it has been packed about 100 times so I am sure it has lost some of it insulative value from crushing the synthetic. This is the "Ray-Way" type quilt (like the one he described in his book) that GoLite no longer sells.
For me, it seems mostly below about 70F or so I have to have some kind of insulation or pad underneath me, so I have been using the 3/8" foam. Padding helped me moreso than wearing fleece inside the hammock by my guess. This was the first pretty cold night (say below 45 or 50 F) that I was in the hammock all night, and I felt the difference between pad+Reflectix and just pad. Reflectix, though, is fairly bulky stuff. I would estimate it around 1/8" thick at least, but I would have to measure to be sure. The center is like thin bubble wrap or mailing wrap that is sandwiched by aluminum. It is mostly used in HVAC applications from what I understand - I found it at Lowe's.
Anyway, I think your idea is excellent. Ed does something very similar that I saw on his website where he recommends combinations needed at particular temperatures. The problem is that these combos only get you to the "ballpark" and there are a lot of other factors like how much you ate, your metabolism, if you had a hard hiking day, your sleeping bag, etc... I am trying to use items that I really use when I hike and still keep pack weight and bulk down. Here is the link I was thinking of, but I think Ed already mentioned it in another thread.
>>> dpwomble@... 09/03/03 03:53PM >>>Dennis,
Thanks for the info. What would help me is if when we do temperature
testing, if we could put some kind of "degrees of temperature
insulation value" on individual items. For instance you mention
several items that have insulative value, 3/8" foam, Reflectix,
fleece clothing, Capilene top and silkweight bottom. Say at 75
degrees you need nothing and at 35 degrees all of the above kept you
warm, that required at least 40 degrees of insulation. Any idea how
much was due to 3/8" foam, the Reflectix or the clothing?
I think we have all read reports that is summary state something
like "with a 14 ounce Ridgerest they stayed warm in their hammock at
5 degrees"... along with 5 pounds of additional clothing that they
just mention briefly. Sometimes the clothing worn has most of the
insulative value, as well as most of the weight and bulk. It would
be nice if this year we could devise a way to more accurately
represent the insulating value, weight and bulk of the various
components. Any ideas? Or is this not practical or necessary?
I have been using a 20 degree insulative value for the 3/8" REI blue
foam that I am using. That is like you say, just a ballpark number
but is based on being a little chilled using it at 45 degrees on ONE
night. I wasn't cold enough to get out of my HH and get my Frogg
Toggs, but I wished I had them on. You need something to go by and
then make adjustments when you learn more, unless you can
mathematically and scientifically model it. (I'm a retired
electrical engineer and what I remember most about thermodynamics
from my college days is that it was difficult & the mathematics were
complicated.) And you are absolutely right about how your heat
source varies, i.e. your body's metabolism... we just have to learn
our limitations and live with them.
I did try a psuedo-scientific experiment to compare the insulating
capabilies of the 3/8" REI blue foam vs the Reflectix 5/16" double
foil/double bubble wrap when they are both used underneath a warm
object and are delaying conductive heat transfer. In this test there
was no noticable difference. The single sided foil car sunscreen, on
the other hand, had less than half the delaying value for conductive