I like the way a sleeping bag blocks drafts and encloses the body well when it's cold, not just mild. I like a sleeping bag's real hood (for a couple reasons). Of course I also like a quilt's lighter weight and reduced bulk. I don't use a bivy, preferring a larger tarp instead.

What if you removed a large part of a sleeping bag's bottom and replaced it with a thin, light, windproof fabric like Momentum or something? You'd save some weight and bulk but retain a bag's more enclosing coverage.

If you have a bag you're willing to cut on, this might be a way to improve your base weight without buying a quilt.

I don't know anything about sewing. Is this a modification that's reasonable or just too complicated?

Sketch of the bottom of the sleeping bag; red area cut out and replaced with Momentum (or whatever):

Someone (I can't recall who, but perhaps Big Agnes) produced a bag which had top and bottom with different ratings (e.g. +20 on top, +40 on bottom). So you could just flip the appropriate side up depending on the expected temperatures. However, if you have continuous baffles it's not needed since you can just move the down from the bottom of the bag to the top and effectively achieve your design.

This is how big agnes bags are setup, they even go one step further, the lower non insulated segment has a sleeping pad sleeve.

Good thinking! But, I am afraid to say that thermorest has sort of beat you to the punch with that idea. Philip did a review on it here: http://sectionhiker.com/therm-a-rest-haven-sleeping-bag-first-look/. As has Big Agness.

Keep on thinking, that was a good thought!

Big Agnes sleeping bags have a thin nylon sleeve on the underside of the bag that you slide your pad in. It holds it in place and honestly, for my colder weather bag (I have a 15 deg) it is by far the coziest, most comfortable, warmest sleep system I've ever used. It has all the pluses of a quilt (no weight on the bottom) combined with the pluses of a bag when it's cold (hood, draft collar, no drafts on the side). I love it and as much as I love my quilt for warmer temps, I just can't justify swapping out my BA.

Haha, brilliant me, reinventing the wheel! Have to say though, those BA bags don't seem to have saved much weight, though their gear seems to be heavier to begin with.

I've got an older TNF Cat's Meow that I'd like to modify this way but I have no idea who could do the work. Plus if its really involved it may be best to just buy something purpose-made.

Okay, this is a nit, but the sleeve on the Agnes adds an un-necesary layer of fabric that adds a littleweight.

I made my own that has no un-necesary layer so it weighs a tiny bit less. I sleep directly on my mattress, but don't find any problem. An extra layer of fabric may be worse - you may slide around more?

The Thermarest Haven has a funky open bottom so you need a groundcloth - extra weight. But, I think that actually works pretty good. I think it was reviewed at backpackgeartest.org.

I would call it a quilt/bivy hybrid, not quilt/sleeping bag.

I think this alleviates the big problem with a quilt - that air can get in the sides.

On the other hand, there can be an open space on your sides that reduces warmth.

And you need to have a flap at the top, over your shoulders, to prevent air from blowing in/out there. I don't know what the Agnes does. With the Haven, it's like a sleeping bag at your shoulders so there aren;t any drafts.

"I think this alleviates the big problem with a quilt - that air can get in the sides."

Check out the zpacks bags. They are essentially a quilt which has a full zip. Also, they cinch around your neck. Oh, and they are super light - like all zpacks stuff.

Big Agnes, Nunatak, Thermarest still sell the no-down-on-bottom sleeping bags. Others that used to included RAB, Gossamer Gear, Western Mountaineering. I have used a RAB Quantum Top Bag since about 2005.

Edited by jshann on 10/07/2012 12:46:24 MDT.

It's a great idea, and the only two bags I use most of the time are my WM POD 30 and WM POD 15. Perfect for me. But I guess the idea didn't take off very well, as WM discontinued this design :(

With the proper choice of farcical it could function as a vapor barrier. So that would be a vapor barrier bag, quilt and bevy all in one.

Yeah, they are heavier than they need to be, but dollar for ounce I can't justify (yet...give me a minute...). I actually like the extra fabric on top of the sleeping pad - I sleep so snugly that for me it's soooo worth the extra few ounces (again, give me a minute...). The sleeve means two layers of super thin nylon that when a full inflatable sleeping mat (which I already use) is slid in it forms a very stable surface. I actually look forward to hiking in the cold so I can justify carrying this extra weight. It is sooooo comfy........

I has a draft collar around the neck and a full hood (like a regular sleeping bag), as well as draft collars along the edges to fill in any pad gaps... so that's prolly where a lot of the extra ounces come from.

Again, it is in no way UL, but wow is it wonderful to sleep in ;)

Of course, in a few months I'm sure ill fall for one of Tim's amazing EE quilts.....but for now....

A sleeping bag without bottom insulation needs to have a way to secure it to the mat (a sleeve is the easiest fool proof way) because otherwise it would not work for side sleepers and folk that toss and turn.

Franco...etal,

The JRB quilts with an available full length omni tape modification readily attach to the JRB Down To Earth Pad Converter (DTEPC) for the hybrid appoach cited..

Pan

"A sleeping bag without bottom insulation needs to have a way to secure it to the mat (a sleeve is the easiest fool proof way)"

That's all you need. One method not mentioned is using velcro to attach the quilt to the mat.

http://www.nunatakusa.com/site07/other_bags/catabatic_sl.htm

http://www.trailspace.com/gear/gossamer-gear/sleeplight/

Pan,
"The JRB quilts with an available full length omni tape modification readily attach to the JRB Down To Earth Pad Converter (DTEPC) for the hybrid appoach cited.."

Yes I know... I named that combo..

Edited by Franco on 10/08/2012 15:23:10 MDT.

James,

I've used something close to your concept on a couple of bags and it worked well.

Around 1970 I modified an REI bag by pulling/pushing all the down away from a 1 foot X 2.5 foot section of the bag's bottom. I then sewed the perimeter of this section so the down couldn't return. This didn't save any weight but it moved the down to the top of the bag where I wanted it. Here's a photo. I put some white box lids in the bag to show the approximate location of the evacuated down tubes. It is hard to see the stitching. The evacuated area approximates the red area in your image





Fifteen years ago or so I added a single layer zip-in piece to my FF Swallow Bag. The yellow portion goes on the ground and is similar to the red area in your image. This turned the Swallow Bag into a 2 person quilt for my wife and me.



I like your idea and it has worked well for me. A single layer on the bottom of the bag is also handy for cooling down. Just turn the bag over for awile so the uninsulated fabric piece is on top of you.

By the way, for comparison, I've never used bag to pad attachments of any kind. No problem for me.

First thing I did with my WM PODs was to cut off some excess extra fabric and bungy cords (shaving 30g/an ounce), and add velcro tabs to the bags and my mats so that the connection to the pad was stable and draft proof. I suspect the original design of the WM POD's pad attachment was the reason they never took off.

"I've got an older TNF Cat's Meow that I'd like to modify this way but I have no idea who could do the work."

I just talked with Rainy Pass repair shop up here in Seattle a couple days ago about exactly the same thing. They understood completely what I was after and said it would probably cost in the neighborhood of $50 to make the conversion. If you don't live in the area, and can't find someone in your locale, you might give them a call. They do excellent work and have a lot of experience with alterations.

1-888-747-7867