Sleeping in a bag liner only

A silk liner cant be relied on to insulate you when sleeping. If you are going for more than a night a bag can ensure a restful nights sleep, even if it is just draped over you. You can cool yourself off by removing a bag but you cant warm yourself up without one. If you want to try it out though go for it, but consider the possibility of shivering through the night and weather or not it would be worth it.

Alot depends on the trip. Is it just one night? Which campsite are you going to be at in the Smokies? What will the forecast be for that particular night? What clothing items will you have with you in case temps drop? What will your caloric consumption be, and what will your caloric output be during the day of hiking? There are alot of factors.

I would err on the side of caution and take a bag. It can still get chilly at night in the Smokies in June, even at 2800 feet. You'll also be hiking all day, and there's a good chance it will rain. I always feel colder when it's rainy and windy out, even if the ambient temp isn't all that low. And if you head higher, you definitely need a bag and good shell gear. Pretty typical to get SAR calls for hypothermic hikers in the southeast high peaks in late spring; people just underestimate the mountains' potential for extreme weather.

Maybe something like the AMK Thermolite 2 bivy sack would work for you. They advertise it as a bag substitute for above 50 degrees. It costs $35. See a review here. (I have one that I got for extra snow camping to use as a bivy bag, not realizing the foolishness of putting something very non-breathable over your sleeping bag.) Trying it out in my apt at 65 degree room temperature in just regular clothes, you can feel it giving some warmth. I haven’t tried it out in the field yet as a sleeping bag.

Yeah, I'd still take the bag along, you can always experiment without it. The #7 is pretty dam_n light anyway, not a great deal more than just the liner. If you're looking to save weight, come up with a way to keep the bag clean so you can leave the liner at home, rather than the bag.

I'd take the bag and leave the liner. You can always unzip the bag and leave it half off if you get too warm. Without enough insulation, your only choices are to exercise 'till the sun comes up or shiver through the night.

I have a Thermolite Reactor (http://www.rei.com/product/705534) mummy liner (244g – no stuff sack).

For both data points I was sleeping on a 2/3 closed cell blue foam mat and in a bug shelter with good ventilation.

At 71 degrees I woke up cool, but it was tolerable. I am a cold sleeper. I was wearing a poly T-shirt, a long sleeve poly workout jacket, and poly long underwear.

At 60 degrees I was uncomfortably cold. I was wearing a poly T-shirt, a long sleeve poly workout jacket, and cotton/poly khakis. Using my PVC poncho as a blanket helped a bit, but caused condensation to collect.

YMMV.

acronym 6/5/2009 1:05 PM

If you are expecting temperatures of about 65 degrees, maybe you can experiment at home. My apartments ambient temp is usually around 68 degrees, and I can drop that easily by leaving a window open.

I think a common mistake when assessing sleeping comfort level is to assume that because you're comfortable at 65 degrees during the day, 65 degrees at night isn't that cold. This forgets the fact that metabolism slows down at night, making us colder.

If you want to know how you'll feel, open your window and try sleeping in just a cotton sheet. I know I need a comforter at night when sleeping, despite the fact that just hours earlier I'm hanging out in the same apartment, at the same temperature, in t-shirt and shorts, comfortably.

Those Montbell bags have full zips, correct? Just unzip and use as a quilt.

I've slept in just a fleece sleeping bag liner before, and I got cold at 68 degrees. A little wind, and you can be in for an uncomfortable night.

In the summer, I have taken an AMK Thermolite bivy and put the bag liner in it. It's a litte more comfortable with the liner than just sleeping in the Thermolite alone. Nice thing about the Thermolite is that it's reusable whereas most space blanket material items are not.

If you do take your bag, what others have already suggested (fully unzipping the bag and using it as a quilt) really does work. I was in the Rockies relatively recently. It was unusually warm. I had a 15F bag (in other words way too warm). Typically not good, but I unzipped it, laid it loosely over me, and slept quite well.