MontBell UL Spiral Down Hugger Sleeping Bag Review

Thanks for a great article! Very informative. I had already decided to get a Montbell Super Stretch bag anyway. I am a restless side sleeper who sleeps in a fetal position and tosses and turns a lot through the night, so I came to hate mummy bags. I always felt like the bag was holding me hostage, and gave me nightmares of someone coming upon my rigid body, figuring I'd expired, and stuffing me in the ground – or a pyramid! Mont Bell has developed a sleeping bag I can actually sleep in. I've been looking at their bags on their website and liked what I saw. Nice to have my suspicions confirmed!

Will,

Good job on the review as usual!

Do you use the same sleeping pad to test all of the 30F rated sleeping bags? If so, what is it? What is your primary sleeping position?

Others will experience a significantly different thermal comfort experience if they use a different pad or primary sleep position.

I have been checking these out recently also due to the reasonable price. I was all pumped up to by one after reading the great review, but they don't appear to make a 40F rated version like the UL SS Hugger. Maybe in 2010?

Richard wrote "Others will experience a significantly different thermal comfort experience if they use a different pad or primary sleep position."

Could you elaborate? Do you know something about this bag not mentioned in the article?

It has nothing to do with this particular bag, it is that the pad also plays a large part in keeping you warm and what pad he used can provide additional insight into the warmth of the bag (for example did he use a Thermarest Z-lite with a R value of 2.2 or a Exped Downmat 7 with a R value of 5.9 – big difference) Also sleeping on your side or stomach/back will allow different ratios of body surface contact with the pad (meaning it will have a greater or lesser effect of warmth).

Casey,

I don't know anything about this bag other than what Will discussed. I do know that Will's impression of any sleeping system's lower limit comfort rating will vary significantly based on the sleep position and pad insulation.

If Will slept on his back, then ~35% of the warmth of the MB sleeping bag's sleep system was determined by the pad he used in the test. If the insulation value of the pad was higher than the standard's, then it would bias Will's evaluation towards the bag being warmer than an EN 13537 LLimit comfort rating. If the insulation value of the pad was lower than the standards, then it would bias Will's evaluation towards the MB bag being colder. If Will slept primarily on his side then ~ 18% of the warmth of the sleep system was primarily determined by the pad.

In order for Will's field test LLimit comfort rating to correlate with an accurate EN 13537 LLimit rating of a bag, Will would have to have slept on his side and used a pad with an R Value of 4.85.

Two of the bags, used in Will’s 30F rated bags comparison table, (MH Phantom & Marmot Hydrogen) have been EN 13537 laboratory tested using the standard side sleep position and 4.85 pad insulation value.

Will
I have owned several of the MBSS bags and have also been impressed with their comfort and true temp ratings. I note that you have two pictures of yourself in the bag: one, sans tent and the other inside the tent. WHen you comment on a bag are you commenting from the perspective of being exposed to the elements or not. Convection can rob a bag of a lot of warmth, so I was just wondering how you tested the bag's warmth. I wish all of you who test bags would let us know this kind of info when reviewing. It does make a difference. thanks and a great review as always.

Mitchell,

Great point about the benefit of also defining the shelter(s) used for an evaluation!

In addition to the convection variable there can be a significant IR variable. When sleeping under the stars, on a clear night, the IR exchange will reduce the surface of a sleeping bag significantly below the ambient air temperature. Tree cover is also an important IR related variables.

Thanks Will! That was really great! Your reviews are very informative and thorough and I look forward to each one. Thanks again.

I bought one of these bags this spring. Very nice bag. Warm enough, nice fit.
Thanks for the nice review. I always wondered about the water repellancy of the bag but was too chicken to intentionally get it wet. It was nice of you to test that part out.

Corrected!

No reason to make people read it anymore.

Larry,

You are right, it was a typo that is now corrected. Thank you for diplomatically pointing it out.

Marmot Customer Service measured the loft of their two 30F synthetic bags for me. I added the data for these two 30F marketed synthetic bags to Will's table in my original post to this thread.

Hi Everyone,

I used a Big Agnes Clearview pad for testing the Spiral Down Hugger. Most of my testing was done in the summer and early fall, so the Clearview was warm enough underneath. I'm a side sleeper. I slept in either a solo single wall tent (BSI Mirage 1P) or under the stars.

Best,
Will

I owned both the MB Spiral Down #3 and the WM Summerlite at the same time while trying to find a 3 season Sierra area sleeping bag.

I concur with Will's finding regarding the MB bag, and felt the Summerlite was warmer. I was able to use both bags on consecutive nights in Little Yosemite Valley in 40 degree temps. The 1st night, I used the summerlite under a tarp, inside a Tigoat bivy, on a GG 1/8" thinlite under a short NeoAir. I woke up and had to fully unzip and quilt the summerlite to regulate my temperature.

2nd night I used the MB in a Tarptent Rainbow, on the same pad system, minus the Bivy(I was testing new stuff) I was just comfortable. Not too warm, not too cold.

I also used the MB on Mt Shasta, on snow in June, in temps that touched freezing. I slept both exposed in just a bivy, on the thinlite plus NeoAir, and also in a the TT Rainbow, in the bivy + pads. My feet got cold, and I added my MB UL Down Inner parka, but I believe I was cold mainly due to my inadequate pad combination, only R-value 3 on frozen ground.

While the Summerlite was definitely the warmer of the two, I would have chosen the MB due to the spacious interior. I'm a 3/4 stomach/side sleeper that moves around a bit in my sleep. The Summerlite had just enough room, but the MB was perfect.

I also prefered the feel of the MB fabric, which has a bit of texture, vs the slick microlight WM fabric.

I got a Nunatak Arc Specialist on gear swap, which superceded both those bags.

Also, what about a smaller (women's) size? Is there any plan to have this in 2010?

I bought a MontBell SuperStretch bag this year and used late summer in Mineral King (Sequoia-Kings Canyon). It's the best bag I've ever owned! I've had other bags that kept me just as warm, but I toss and turn a lot in my sleep. Every other bag I've owned felt like I was in a straitjacket. This is the first bag I've owned that allowed be to sleep through the night just as comfortably as if I were in my own bed!

I purchased a Mont-Bell Spiral Down Hugger #3 for myself and a Sierra Designs Nitro 30 for my Son (12 year old boy scout only 3 inches shorter than, he is 5' 4"). The Nitro was on sale at Moontrail for only $189 (should have bought 2!)

I love the stretch of the #3, but I sleep cold so on a night at 38-40 Degrees I was cold even in my old Poly pros. My Son said he was toasty warm in his bag. I tried the Nitro 30 and it was indeed warm, but too tight for me, if I had to wear my Mont-Bell thermawrap I would be squeezed.

I sent the Spiral DH #3 bag and I am getting a UL Super Stretch #2, which weighs 28 oz, but has 14 oz of Down. I am hoping it is much warmer, as I do not want to spend the money on a Nunutak Alpinist just yet> I have invested in Ibex tops and botttoms too. I can live with the heavier bag (9 oz more than a Spiral DH and 3 oz more than the Nitro 30). I wish they made a Spiral DH #2 with 14 oz of Down, it would still only weigh 23 oz! Oh well.

If you sleep warm, the Spiral Down Hugger #3 may be for you. I think I need a #2, if that doesn't work, I will try a Spiral Down Hugger #1, which has 20 oz of Down and weighs 2 lbs., that should be plenty warm.

hi, long time lurker and new poster –

does anyone know how far down the #3 will pack? i'm thinking an outdoor research silnyl 10L bag, but is that too small?

thanks!

Ultra Light Spiral #3 Long in factory stuff sack (using the smaller of the two draw cords) and Montbell inflatable pillow in its sack.

The stuffed size is given in the review. Please RTFM. :-(

Stuffed Size
5.3 x 10 in (13.5 x 25 cm)

Hi Marc,
I did RTFM but what i'm curious about is a conversion of dimensions to liters – i've always been confused about that. i am debating between getting the super stretch #3 and the UL super stretch; i guess the only difference is a few oz of weight and maybe the packing size, that's why I was asking. thanks for your help.

Google is your friend, as always. (Who knew?)

First, you Google "volume of a cylinder" to learn what the formula for a cylinder is, where the first page I see is:

http://www.mathsteacher.com.au/year9/ch14_measurement/18_cylinder/cylinder.htm

and the formula for a cylinder is
Volume = pi * radius * radius * height

Since we may have all slept through high school geometry, we'll Google "radius", and Wikipedia helpfully reminds us that the radius is one half of the diameter (and gives us pictures, even).

http://en.wikipedia.org/wiki/Radius

radius = 13.5cm / 2

And, since we are assuming we all slept through high school geometry, we'll Google "pi" to find out what the value of pi is. We find:

http://math2.org/math/geometry/circles.htm

which tells us that pi is 3.141592

but we'll just use 3.14 to save ourselves some typing. Besides, the measurements in the review aren't all that precise. (For a calculation this crude, we could just use 3 as the value of pi and be plenty close.)

Then you plug in the numbers from the review, using
radius = 13.5cm / 2
height = 25 cm

and

Volume = 3.14 * 13.5cm/2 * 13.5cm/2 * 25cm

We'll use Google to do the calculation for us (no scientific calculator needed), typing in

3.14 * 13.5cm/2 * 13.5cm/2 * 25cm =

and sure enough, Google does the math, figures out that you are using cm for dimensions, and gives you the answer in liters (kinda cool, huh?). Google says:

((((3.14 * (13.5 cm)) / 2) * (13.5 cm)) / 2) * (25 cm) = 3.57665625 liters

No text books, no calculator, no nothing. Just Google all the way.

If you have had your coffee today, you could do the same calculation in inches:

3.14 * 5.3in/2 * 5.3in/2 * 10in

which Google calculates and returns as liters:

((((3.14 * (5.3 in)) / 2) * (5.3 in)) / 2) * (10 in) = 3.61345413 liters

Presto! (Again.)

Since the stuff sack is not a perfect cylinder, but has rounded ends, you can assume that the actual volume of the stuffed MB Spiral is a little less than the full 3.6 liters, probably 3.5 or 3.4 liters.

Now that we have had our daily lesson Google-Fu, it is left to the reader to plug in the approximate dimensions from the picture I posted of my UL Spiral #3 long earlier in this thread to calculate the approximate volume of the long version of the sleeping bag in its stuff sack. :-)