A more scientific method to extend sleeping bag temp ratings

It sounds good in theory, but I'd be cold.

Are you sure you can add the clo values for your legs, torso, and head together ? I suspect that you need 10 clo worth of insulation over your torso and about 8 clo over your legs and head to be comfy at 0 degrees.

Reminds me of a guy I knew that put a bunch of performance parts in his car; his estimation of the horsepower went from 200 to 750.

>Are you sure you can add the clo values for your legs, >torso, and head together?

Well, that is definitely what Richard does in all of his calculations. You can add them together as long as you account for the amount of surface area covered by each piece of clothing.

Interesting…
With information like this, someone could potentially invent a really cool gear closet that allows you to just throw all the gear you own in it and it organizes everything. Everytime you want to go on a trip you just punch in where and when you're going, and it just spits out the most suitable pack you own which it automatically filled with all the gear it chose to be best for the trip you specified. This way you don't have to decide which sleep system is best. The super gear closet just does it for you… I can see it now.

-Sid

Following the same reasoning using Richard Nisley's chart:
I have a Feathered Friends sleeping bag rated at 20F, overstuffed with extra down making perhaps 15F (clo about 7.5). It's too narrow for using much clothing inside An overbag made of thru-hiker.com 5oz/sq yard climashield XP will have a clo of 5*0.82=4.1 for a total (bag+overbag) clo of 11.6.

Extrapolating Richard's graph, this should give me a combo that works at 35F or 40F colder, or -20F to -25F.

I really don't believe that -25F or even -20F. If this combo gave me -10F comfortably and -20F survivably, I'd be happy.

So, what do I need for New England and the Adirondacks? Probably I need an honest -20F rating (moderately comfortable) with colder being survivable with clothing placed over the down inner bag. So, I'm thinking that 7.5 oz of climashield XP on top, with perhaps less underneath would give enough of a margin of error.

Caveats: I find it hard to read Richard's graph with the precision that I am implying here. Also it may not extend linearly beyond 0F; I'll have to think about that. Finally , what comfort level is implied by Richard's graph for sleeping?

Sid:
You might be onto something there… then you could program your route into the system, and it would spit out pre-bagged carbs, proteins, fiber "mush" which would give you the most weight-efficient combinations of nutrients based on your needs! Cooooolllllllll. Who wants to collaborate on the patent?

Cheers, James.

Seriously… I made a spreadsheet that did this. I input the comfort level I wanted, the number of days for the trip, and the season and it gave me a list. Yes, you may have your own variables you'd rather have, but it's a simple matter to make it happen when you know your gear. I kept the gear location for each item listed as a part of the data (which pocket, etc.) and basically I could put the items in a pile and start loading the pack.

I don't think you can count the down clothing at its full clo value, since some of the down is being crushed under you. You probably need to discount it by a fifth to almost a half, depending on how you sleep.

Edit: hmm but then again the sleeping mat has you 'covered', so if the mat is as insulative as the rest of your system then maybe it doesn't matter.