My experiment with a mylar/space-blanket mummy-bag-shaped liner as a vapor barrier failed. The lousy $5 “emergency sleeping bag” mylar/space-blanket I bought from Amazon, shredded up in the middle of the night. Mylar is tough stuff, but mine ripped around the circumference a few inches down from the top opening, and also blew out at the taped side seam. Was I having a crazy dream and thrashing around? Dunno. Anyway, I was sleeping Friday and Saturday nights this weekend on top of a mountain in 10 degrees with a breeze, under a small tarp. I ended up being comfortable without the VBL and my second night slept toasty warm without it. My setup is to pull my Grand Trunk Nano 7 ultralight hammock through the zippered footbox of my Kelty Lightyear down 20 degree bag. When I get in the hammock, I reach down and pull the bag up over my legs and then zip it up so that I’m cocooned in the hammock with the bag zipped up all around me. Doing this in a hammock means the bottom of the sleeping bag isn’t compressed against the ground or against a sleeping pad, so you stay equally warm all around, top and bottom. The only downside is that the mummy bag’s narrow width does not let the hammock expand quite to its full width capacity, and you are slightly limited in getting the diagonal lay required to lay completely flat in a gathered-end hammock. Instead, you sleep with a slight curve in the hammock rather than flat, but I still find it amazingly comfortable. I slept toasty warm in 10 breezy degrees atop a mountain. I climbed into the hammock at 9 p.m. and didn’t get out until 7 a.m., well rested and refreshed. I wouldn’t have felt good sleeping on the ground in similar conditions, for sure. I can’t imagine ever sleeping on the ground again. Super comfortable. Super ultralight. Super warm. My entire sleep system, consisting of hammock, complete hammock suspension, tarp (MacCat Dexluxe in Spinnul, including ridgeline and guylines), tarp guyline stakes, and sleeping bag weighs 64.1 ounces (including various stuffsacks) and yields perfect, no-pain-in-the-back sleep and toasty warmth down to the 10 degrees I experienced this weekend, and probably lower (I was wearing smartwool longjohns and kept my down jacket on inside the bag, and had on a fleece beanie).
I’m considering a cuben fiber VBL. But since I was comfortable at 10 degrees with no VBL, and since I won’t often be sleeping in 10 degree cold (I hope), maybe it’s not worth it unless I’m out for a week and the bag gets heavier each night with sweat vapor. If I do splurge and buy a cuben VBL, I would wear the smartwool longjohns inside the VBL and drape my down jacket on top of me like a quilt, on top of the VBL but still inside the bag. I suppose that would be a good system.
Thoughts and comments?