Hey everybody,

I’m interested in making a sleeping bag of my own design: insulation on the top, just a single layer of fabric on the bottom.

As far as insulation goes, I’m thinking either Polarguard 3d or Climashield XP.  How much XP should I use if I want to have either a 20 degree vs. a 30 degree bag?

For the insulated top, is it best to have momentum on the outside and the liner?  Or would it be preferable to have a breathable 1.1 oz nylon on the inside?  What’s the benefits, if any, of having momentum on the inside?

Also, what would be the ideal fabric choice for the single layer bottom?

Thanks for the help!

RE insulation:  do a search in the forums for the keyword “clo” (no quotes) for info on how much you’ll need for a particular temp rating.  For a 20 degree bag of typical construction you’ll need somewhere between 5 and 10osy of XP.  Don’t bother with 3D, it is an outdated insulation seldom used these days.

Momentum is a better overall fabric than 1.1.  Buy 1.1 if you’re unsure if you can pull off your project, or if cash is tight.  Otherwise, momentum is a better choice: it looks, feels, breathes,weighs less and repels water better than 1.1.

Ideal is a loaded word.  There are many options, and without knowing what you want it is not possible to propose anything.  If it were me choosing, I would put momentum on the bottom too.

Thanks AYCE!

I’ve done a bunch of research since I posted my question, and ran into the whole Clo issue.  Boy, is it hotly debated. 

For those of you with the same question about insulation, here’s the summary—nobody knows…but here’s a few guidelines:

From some article online:

The study found that a CLO value of 2.5 was needed to keep a sleeping person comfortable at an air temperature of 59 degrees F, or 15 degrees C. A CLO value of 4 was required for comfort at 48.2 degrees F, or 9 degrees C. Thirty-two degrees F, or 0 degrees C, you’d need a CLO value of 6.

According to AYCE on a previous thread:

In a well sealed bag with good ground insulation

clo 2 @ 40 deg
clo 4 @ 20 deg
clo 6 @ 0 deg

According to Bill Fornshell on the backpackinglight.com forums, he built a bag similar to what I’m looking to do:

Sleeping Bag example

I think for my first time, I will be doing 1.1 nylon all over and a layer of 5 oz climashield xp and see how that works out.  Because it’s my first homemade bag, I’d like to not spend too much, and would like to use the 5 oz as a baseline test for warmth and clo.  I’ll probably follow it up with a momentum bag with adjusted insulation.

One question (AYCE):  If you could use Momentum in one place on the bag (shell, lining, bottom), where would it perform the best (as in breathability)?

Thanks!
Tornado