Mostly because reading lately I have seen climashield estimates all over the place.

Until a couple of days ago I was using the numbers 2.5=45dF, 3.7=35dF, 5oz=25dF but now after reading that seems to be overly optimistic and I dont like to wake up freezing.

So now what I am building is this.

M90 shell with one layer of 3.3oz apex with a drawstring footbox.

I will be able to open the shell and add another layer of insulation inside.
I might add a layer of 5mm silk on the inside on top of the 3.3oz CS but I have not decided yet.

Right now the second layer of insulation will be 5 oz Climashield Apex in a 5mm silk (0.5oz) shell.

I figure the base quilt should be good to 40-45dF or so and with the additional layer maybe 20-25dF with a base layer and socks.

So the total for cold weather will be outside M90, inside one layer of 3.3oz plus one layer of 5oz, 2-3 layers of silk.

Size is exactly 3 yards so the base quilt without the 5mm silk will weigh 17.5-18 oz.

The additional 5mm silk covered/5oz apex will weigh 18oz.

The 5mm silk weighs 1.5 oz per layer.

I already have a very small 2.5CS M90 quilt just for summer that weighs 12.8oz.

Thanks

It also depends on what you're wearing inside

I just spent a couple nights with a 3 ounce vest and a 5 ounce top bag and was warm at 29 F. I think I would have been cold at 20 F.

I ran a clo calc I found here and what I got was this.

3.3 - 38dF
5 - 27dF
8.8 - 4dF

Dont know how close I will get to that but if its within 5 or so degrees I will be happy.

Right now I have the pattern laying on my floor debating on the size.

Last one I made was too small. This one is based more or less on the Long Golite ultra 20 I had and the MLD Spirit XL. Its slightly wider than the ultra 20.

Richard's plot is about the best http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/9378/index.html

It says 3.3 clo = 59 F, 5 clo = 42 f, 8.8 clo = 6 F

Maybe Richard's numbers are a little conservative.

I have slept many nights in a vest and bag with almost 5 clo down to 35F.

Another thing - if you're talking 6 F you probably need something more than a quilt - like a mummy bag - so the 8.8 clo = 6 F isn't good

8.8 looks close to correct.
I am thinking more like 10-15dF in the real world.

The other two numbers IE 3.3 and 5 look too conservative to me, but there are a lot of variables.

I know that totally wrapped up in a Apex 3.3 quilt or bag at 59dF and I would probably be sweating my A$$ off.

The formula I used was this one. Found it here on some thread I cant find now.
Avg temp rating = 60-(clo * total clo * 10)

Not 8.8 its 8.3.
IE both layers 5+3.3=8.3

Sorry.

Yes at 5dF I would want a good mummy bag.

Edited by tammons on 02/02/2012 19:32:34 MST.