Sleeping bag + Quilt

I remember a lengthy thread discussing that very scenario. People spoke about using a synthetic bag/quilt over a down bag. The purpose was to not only allow for an cold environment below the bag rating but to have moisture travel through the down bag to the outer layer of the synthetic bag.

The moisture issues would be easier to deal with the synthetic than with the down bag.

http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/89063/index.html?skip_to_post=758650#758650

Edited to include link to that discussion

Wow – that's a very complicated discussion! (I didn't know you were over here, too – thanks for the link!)

OK – so in technical terms, it seems that it may not be a great idea under specific weather conditions and in specific shelters.

I guess what I'd like to hear is practical, field experience…I plan to sleep in one of the Loj lean-tos late next month and I fear my bag won't be warm enough. I do have down pants and sweater, and I may simply ear those inside the bag instead of covering the bag with anything.

Hi Scott, good to see you here.

There is a formula you can use to calculate the effective cold rating of using two bags (or a bag and a quilt) instead of one.

x -(70 – y)/2 = z

x = first bag (higher rated/lower degree)
y = second bag (lower rated/higher degree)
z = rating of doubled bags

In your case:

15 – (70-30)/2 = z

15 – 20 = -5

So you'd end up with a -5F rated set up.

Here are a few discussions about your scenario:

http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/30057/index.html?skip_to_post=253517#253517

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=10415&disable_pagination=1

http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/24225/index.html?skip_to_post=196814#196814

Scott,

A lot of people have done it… works roughly as described by the formula above. I regularly use a 45º quilt over my 20º bag in winter to bring it down to near-zero. This works great with a breathable bivy to keep everything in place.

Thanks…that helps.

Now to find a gently used quilt- or make one of the RayWay kits!

Hi Scott,

Last year, I used a 50d EE Enigma as an overbag on a couple of cold weather trips. It worked very well and took on zero moisture. Given that it is made with Downtech, I was not worried about it taking moisture on anyway. Apparently, I think I read recently that the waterproof down apparently dries more quickly than synthetic as well.

And given that down is more permeable than synthetic, it might be worth a look.

Matt

I have paired a WM Ultralight (20f/-7c) under an EE (20f/-7c)quilt, both 800 natural down, and took them to -25c comfortably inside a MLD cuben/event bivy and mid tent wearing merino 250 base. Based on formula above I should get to -15f, so that works out about right.

Derrick