For northbounders leaving in late March, the first several weeks on the AT can be brutally cold. You might think that Georgia and North Carolina in spring would be nice, but the trail runs around 2500' above sea level with several peaks well above 5000'. Snow and overnight lows in the low teens and below are common.
We're looking at two sleep systems - One for the "shoulder" seasons of spring and fall on either end of the trail, and another for the dog days of summer. The shoulder system needs greater insulation - both from the air, and from the ground. Sleeping bags, rated for 15 degrees, with insulated sleeping pads are prescribed. We'll dedicate a pair of dry socks to sleep in. On colder nights, we'll wear any clothing required to supplement the bag!
We chose down over synthetic fill for the weight and compressibility of down. Synthetics have the advantage of retaining their insulation properties when wet. We pack our bags in water-proof bags in the bottoms of our packs where they will stay safe and dry till we're ready to roll them out. We'll fill the room we saved in our packs with extra Snickers bars!
Marmot was selling their highly-rated Helium 15 Degree Down Bags on closeout at most of the online vendors. They're filled with 850 fill-power goose down, which compresses very nicely. They have an "EN" (European Norm) rating of 16 degrees, which is the temperature that one should be comfortable if wearing a base layer, and a hat. The shell is treated with a durable water repellent finish to help keep the bags dry. And, they sport a down-filled baffle along the zipper, and a comfortable hood. We picked up a long for me, and a women's regular for Mary. These weigh 29/32 ozs.
That DWR finish will help keep the bags dry from condensation in the tents, rain coming in thru vents, etc., but it's not so good at passing moisture generated from the inside. After several nights, the down can start to loose loft and insulation properties unless you take some time to air them out well. A long lunch, on a sunny bald, with a panoramic view of the Appalachians, is a good time for this.
To add a few degrees of warmth, but really to keep the inside of the bag clean, we're bringing Cocoon Expedition Liners made of ripstop silk. Easy to throw them in the washer in town, and protect the bags from dirt, sweat, body oils and other hiker funkiness. On hot nights, they may be all we need.
We're side sleepers, and wanted thicker inflatable pads to keep our hips off the ground. Big Agnes makes an Insulated Air Core Pad which is 2 1/2" thick when inflated. PrimaLoft insulation gives it an r-value of 4.1, to make it a 3-season pad, weighing 22 oz. We found that to be insufficient on a cold spring night, so we picked up a pair of Gossamer Gear's 1/8th" Thinlight Insulation Pads to put on top of the Big Agnes.
In yet another compromise for comfort, we opted to carry Exped Air Pillows at 3.6 ozs instead of using lumpy stuff sacks full of clothing.
Total shoulder season sleeping system weight is 3.75 lbs
Once we get to Pearisburg, Virginia, we'll swap out our shoulder sleep and clothing systems for summer weight stuff. A process we'll reverse in the fall somewhere before we get into the White Mountains.
Again, we shopped closeouts, and got last year's stuff at deep discounts. Both of us got Mountain Hardwear Phantom bags, rated down to 32 degrees, and weighing 23/24 oz. We got the shorter, lighter, uninsulated Big Agnes Air Core Sleeping Pads weighing in at 16 ozs. We'll keep the ExPed pillows, and go without the Thinsulate pads.
Total summer weight - 2.7 lbs
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