Layering Montbell UL SS Down Huggers

Jefferey,
I own three MB bags, and to estimate the temperature rating of the various combintations, I simply add the weights of the down filling, and compare that total weight to the equivalent heavier bag.

For example, two #7 bags each have about 5 oz of down; so that is equivalent to one bag with 10 ounces; which would be a #3.
Or, putting a #7 inside a #3 is equivalent to a #2, and so on..

Of course this is a simplification, but I think the reduction in loft from one bag lightly squeezing the other one is compensated for by the 4, instead of 2, layers of nylon which would trap additional heat. Just an educated guess.

If you want to make these types of estimates, maybe to decide which two bags to buy, here is the info you will need for 2006 bags:

Total the weights from two bags, and re-enter the table at that total weight, then go left to the closest temp rating of your equivalent bag. These ratings are the "low-comfort" (i.e. one thin clothing layer), not the extreme low survival rating.

If you want to do this mathmatically, here's a second order polynomial* curve fit..
'F = 0.0433(oz*oz) – 3.3723(oz) + 63.741
For example, 10 ounces total down gives you a 34'F bag, about a #3.

*interestingly, temp rating is not linear with respect to fill weight. Adding 5 degrees warmth at the colder temperatures requires more down than adding 5 degrees warmth at the warmer temperatures.
Here's a chart in SI units showing this non-linearity

Anyway, long story short, I went with a #3 long and a #7 long. Alone or in combination these give a very wide temperature rating.

Hope this helps

I took a slightly different approach then the pimp, erh, I mean Brett above. Nice outfit, BTW, Brett!

I'm 5'9" and 150 lbs., and I find the MB Thermal Sheet — which is basically a hoodless No. 7 bag with full zip — a great summer bag by itself (comfy to 50F) and also a perfectly sized liner for any of the regular MB bags! The only caveat is that the Thermal Sheet is sized smaller and it's NOT stretchable. I would say that 175-180lbs is about the limit.

I have used my Thermal Sheet and my No. 3 together down to 19F. I worn long underwear, and felt totally comfortable. I was pretty sure the combination would still be good at 15F. Thus, in my experience, the liner gives an honest 15F temp boost.

Brett's analysis above makes sense too. However, I think the resulting 10F boost or so is too conservative. I believe the reason that actual temp boost is higher is because using a bag inside a bag also gives you four additional layers of nylon besides added down fill!

If my hoodless Thermal Sheet is good for a 15F boost, then I think the hooded No. 7 should be at least as good, if not more so. However, for me, I think I would find it tedious dealing with two hoods — which was why I opted for the simpler and lighter Thermal Sheet instead. If it really gets cold, I think I would rather wear a hat then deal with two hoods and more drawcords. YMMV.

Well, if Brett is the MontBell Pimp and Ben the MB Guru, then I wonder what I must be? Just out of curiosity I spent some (oh so productive!) time counting up just how much MontBell gear I have accumulated since 1977 when I bought my first MontBell Poncho… I counted 118 items! (about 20 have been retired) Man, that really shook up my "Live Simply" philosophy!

I've been using a Thermal Sheet since 1997, both as a summer bag and as a winter liner with a No. 3 Downhugger. It's just light and compact enough to not take up huge amounts of space, but protective in moisture with its synthetic fill. Like Ben the non-stretch makes it somewhat confining compared to the stretch bags, especially about the knees, but that's a minor complaint.

As a MontBell Club member I received my new season catalogues the other day and now will have to lock down my wallet so I don't break out the credit card. Funny, though, in the clothing catalogue there is no sign of the Thermawrap jackets, only the UL Down Inner Jacket. That's never happened before. I mean, it still gets quite cold in the summer on the higher peaks in Japan.

Recently I bought the new Inner Thermalwrap Jacket and though it is light, it just isn't as warm as my older version. For summer walking then I will most likely continue to use my old jacket.

Miguel:

I think I only have eight MontBell pieces, and in any case, I didn't even know of their existence until just 3 years ago. Clearly, YOU are the guru! I am just a lowly gear head. :)

Comparing the UL Thermawrap jackets:

2004 – Exceloft insulation 60g/m2 body and 40g/m2 sleeves
Current – same insulation but 50g/m2 throughout

You are correct that overall, the older version(s) were warmer.

Miguel, my callsign 'pimp' is not a badge of honor; I got it for being vocal, like the callers outside nightclubs at Shinjuku, I guess. Also, I'll forward any MB item worldwide for people who cant get it locally. Just sent a down jacket and pants today in fact.

For you, Miguel, I suggest the more honorific title of MB 'Philosopher', given your long experience with MB. Anyone who has read your website and seen your amazing photography could not disagree with that title… But, that being said.. 118 items!? Chotto matte kudasai! You are The Man I quote when I use the phrase "UL mind" (from one of your old posts). Now we discover you have a closet full of MB, and who knows what else.. : ) just joking. Who can blame you.

Speaking of gear volume, my current goal is to rid myself of duplicate items, thus having only 'one of everything'. One windshirt, WP/B jacket, stove, pot, etc.. Recently I have sold a few items to BPL members, and a couple on ebay. I am not profiting, but I'm slowly trimming away the fat until perfection is reached when there is no more to trim without sacrificing performance requirements. BPL member's knowledge has been essential in this journey.

Yes, Miguel, I picked up the new MB catalogs yesterday as well. Most of the contents is a repeat, but there are a few amazing new items (at least I think they are new), a 58 gram windvest, and an amazing full-zip, hooded, pocketed windshirt in ballistic-airlight with DWR, at 89 grams!! That might be a Houdini killer, because its 67 bucks US!
Combine that with the 68 gram windpants and youve got a 157 gram (5.6 oz) SET!

Gawd, don't call me a philosopher! I'd rather be out there wearing nothing at all than to spend all my time contemplating MontBell gear. Most of all that volume of MontBell are little items like money purses and hats and even a tiny solar battery charger. It's just the way things work for me here with outdoor gear. I go to the stores, cast around for anything I might "need", see the astronomical prices for items that I might prefer buying, like for Patagonia and Montane (I saw the Superfly the other day for $600.00!) and Haglofs, and always end up right back at the Mont Bell sections in almost every store I visit. The prices and designs just work out right here in Japan.

Since I just moved and all my stuff is in boxes I've been steadily going through everything and weeding out everything I don't need. There is a pile of stuff all the way up to the front door lintel. With the idea of "live lightly" behind every item I am looking at, I hope to make my living space and all the items I have of everything in the house whittled down to the bare necessities. It's a sad comment on my lifestyle when the room that most approximates the way I want to live is the toilet room (in Japan toilets and baths are in separate rooms)… all the essentials with nothing that is not needed. I must say it's hard to let go of a lot of this stuff. And then I remember that the hold these things have over me is purely emotional. Once I get rid of them and out of sight I most likely will never miss them. That being said, I'm sure that the guru of lightweight, Ray Jardine, probably has a lot more stuff in his house than I ever have. The closest I have ever come to ultralight simplcity in my lifestyle is when I first returned to Japan to live, with only a single suitcase. Ah, those were the spidersilk days!

Now, just imagine the difficulty of packing a minimalist backpack, then imagine doing the same for an entire apartment!

Brett, you shouldn't have shown me that windclothing set. AHHHHHHH! I can feel the grams weighing at the corners of my enlightened mind! Oh, the Horror! The Horror!

Erm… this IS completely hijacking this thread, isn't it? Sorry about that…Let's see… yes… um… a relevant and helpful comment… err… uh… yeah, the Thermal Sheet is GOOD!

Now, I don't think Jeffrey would mind; after all, we did answer his questions, correct?

Brett:

I don't see how you can pare down to just one of everything if you intend to hike in different places and all year round. A bonsai garden (a Chinese art form of course) adds much pleasure to life. But imagine if one should chop down all forests and retain only bonsai gardens!?! Put simply, one needs both.

For me, I gravitate towards two sets of gear — one that is a balance of light weight, features and durability, and a second set that is oriented much more to light weight. For shorter/flatter hikes, I enjoy the more feature-rich gear pieces. But going up Mt. Whitney (or Mt. Fuji in your case), I go for the lightest that will work…

Ben, props* to your ancestors for having a refined culture while mine were still running around what is now England and Scotland, bathing once a week and hitting each other over the head with clubs.

I really do mean one of everything; but a day pack is different from an alpine pack is different from a canyoneering pack, etc.. So I'll end up with more than one jacket, light, and so on. But I want to eliminate two or more items which meet exactly the same set of performance requirements.
Also, insisting on multiple-use, urban-use, and returnability will allow me to reduce my total # of items.

* http://www.urbandictionary.com/define.php?term=props

edit, Ben, I thought you were quoting Monty Python there for a moment… the shop is a little far but I will probably go before the end of the week and bring back photographic evidence.

OK, I see. One item per category.

Now, please go to that shop (can't remember the name) and find me the Japanese equivalent of the BD Firstlight or HiLite — similar weight but add a vestibule, and also wp/b fabrics. Arigato in advance. :)

Ha Ha,
Miguel is like Mel Gibson in the Conspitacy Theory where he has to buy a Montbell item evey time he walks past one so he'll feel normal.

A double bind, that. UL addiction and MB addiction rolled in one. If I go without buying some kind of new MB gear every month I go into convulsions, even if it is just a color change! It's quite embarrassing when I swing open my closet door, scan for what to wear, and end up sporting the MB label on every item I put on, from underwear to hat! (just kidding… but there are times when quite a few items I am wearing are MB…). I swear that when I wear enough MB items I walk about tripping out with hallucinations. Must be the fumes from all those new synthetics. Maybe that's why I love the mountains so much!