Free advice worth what you paid for it. ;-)
Sorry for the slow response, been busy.
Starting with being inside a zero degree synthetic bag and pretty normal winter clothing, here is what was happening with his HHSS additions:
3 things:Night one, -5F: in my Undercover, in addition to standard space blanket, did my typical cold-weather configuration of Exped Multimat on the bottom, and a down jacket under my back in between the OCF and Multimat.
Clothing - Torso: 200 wt Polarfleece pullover as outer layer
Night two, -27F: added my down +30F REI Sahara down bag between Multimat and OCF in the UC.
Bag: added fleece bag liner, and Primaloft parka thrown over legs
Clothing - Torso: 300 wt Polarfleece as outer layer
Clothing - Neck: fleece neck gaiter to pull up over eyes
1: he was zipped up inside a 0*F synthetic bag, which would have added significant back warmth as opposed to a down bag or down or syn used as a quilt. Not to mention way more top warmth than you had, and he wore no cotton.
2: he had an Exped multi mat spread out in the bottom of the UC, a very flexible but pretty thin ( I think ) pad. One thing I think this pad did, in addition to adding some warmth, was cause a little sag in the UC, leaving more room for the down bag to puff up and not be compressed so badly by the UC elastics.
3: the 30F summer bag ( same rating of 30 as your Jarbige) he put in the bottom was, I think, zipped up so that he would be sleeping on both the top and bottom layers, double loft.
Still, he was at 45*F colder than your hang, plus he was quite warm.
When you felt you were at the limits, did you happen to notice if you were about to get cold on top only, or all over, or just your back? Because at 30 or 40F, your top quilt was obviously past or near it's limits.
Here is the way I look at trying to guess "how warm will it be". If your back gets cold at 70F using nothing, and the Jarbige keeps you warm to ~ 30F, that is 40* worth of protection/insulation. So, if you can stay toasty at say 40F in your HHSS, then adding the bag below should by you about another 40F of warmth. Getting an additional 40F of Jabrige protection on top of your HHSS warmth should get you to zero F if all is perfect, which it rarely is. If your good to go to 30F in a HHSS, then adding that Jarbige might take you below zero F.I was maybe over-warm the first hour or two after laying down at 9:00-ish, but not terrible. After that I went to comfortable, then when it got down to the coldest just before it started to get light out I was almost at the tipping point of getting cold. Granted, I didn't have my tarp down to hold in some heat, but it was a rather calm night with the occasional breeze that would come through.
I've been thinking about how much the Jarbidge would add to make the HHSS go past the normal 40*-ish range of comfort since the Jarbidge is supposed to be good to about 30*. Since the night we are currently discussing got down to 18*, I am wondering if this is possibly what should be expected from this setup?
In addition to kwpapke, look at my example. Adding 1 thick fleece jacket and one thick down vest into my HHSS ( which included 1 HH pad/sb + the HH kidney/torso pads ) kept me toasty at 14F with a 6F windchill ( no tarp used ).
But, all of the above is just a theory, because we are all so different. For example, my wife would have froze to death at those temps in that get up of mine!
But the thing
Apparently, signature that I used from 2006 no longer tolerated so now deleted.
One thing that I just remembered to mention is that I suspect the Jarbidge may have been strung a little too tight and that maybe I could have gotten a little more loft if I set it up differently. I'm pretty green when it comes to underquilt setup, only knowing what I've read from the forum or seen on videos and not had any hands-on tutorials from someone who actually knows what they are doing.
Anyway, thanks everyone for the input! This just shows that I need to get out and experiment some more.
PS. One more thing that I just remembered is that I was tossing and turning a lot trying to get comfortable and I remember a couple times my moving drew in a rush of cold air underneath my TQ.... yet another factor.
Last edited by Banjoman; 02-22-2013 at 10:35.
Spent four nights last week at Dolly Sods WV with my new DIY UQ. Temps were down to 10 deg at night. with my synth base layers, fleece pants and top, UQ and new Nunatak Arc TQ, i was sweating my butt off. I had condensation from the netting all the way to the underside of my cc pad. seems like the best bet for the source of your h2o issues. i am a warm sleeper tho.
BTW Dolly Sods in the winter is Burly