The Spiral Down Hugger #3 introduces MontBell’s new Spiral Stretch System and 12 denier fabric, which together reduce the weight of a sleeping bag by 2 ounces.
Like MontBell’s existing Super Stretch System, their new Super Spiral Stretch System is unique. Basically MontBell found an alternative way to create a stretchy sleeping bag and save some weight to boot. The technology is best described in their own words: “New for 2009, MontBell has incorporated a classic tailor’s technique to address sleeping bag comfort issues. By integrating a woven fabric ‘cut on the bias’ and orienting the fabric’s warp and weft threads at 45 degrees to major seam lines, the sleeping bag becomes more fluid or elastic in nature. Additionally, ‘spring like’ crimped fibers are used in the weave of the fabric to capitalize on their inherent stretch properties.” Rather than the traditional horizontal or vertical orientation of the down tubes, they are oriented on a 45 degree angle and appear to spiral around the sleeping bag.
The new Spiral Down Hugger line also introduces MontBell’s new 12 denier Ballistic Airlight sleeping bag fabric. Switching from 15 to 12 denier fabric plus spiral construction reduces the weight of a sleeping bag by about 2 ounces. Apparently MontBell is very satisfied with the new technologies because they intend to extend the Super Spiral Stretch System across their entire sleeping bag line (available March 2010), replacing the current Super Stretch technology.
The main features of Spiral Down Hugger #3, rated at 30 F, are its spiral construction, 12 denier fabric, 800 fill power down, sculptured hood, and three-quarter-length auto-locking zipper. The manufacturer claimed weight is merely 19 ounces for size Regular and 20 ounces for size Long.
My initial reaction to this bag is: “How did they do that?” Frankly, I don’t know, but they did it, and the design works. The 5.5 inch baffled down tubes do not spiral completely around the sleeping bag as the name implies. Rather, the tubes on the top and bottom panels are oriented at a 45 degree angle but run in opposite directions. It would seem like the construction would get complicated at the hood and foot ends of the bag, but MontBell makes it look simple: the spiral construction terminates to a sculptured hood by adding one rounded chamber, and the foot end is neatly finished as well.
I have always been impressed with MontBell’s Ballistic Airlight nylon shell fabrics and Polkatex DWR finish, but the new 12 denier shell on the Spiral Down Hugger is truly remarkable. It’s the softest sleeping bag fabric I have seen, and it sheds water like a duck’s back.
The Spiral Down Hugger’s hood (left) covers the face very well. It draws easily via a simple braided cord and cordlock. On the inside, the bag has a thinly insulated flap that covers the zipper (right), rather than a puffy down-filled draft tube.
The Spiral Down Hugger has a YKK #5CN two-way auto locking zipper, which is used on most lightweight sleeping bags these days. This zipper has separate pulls on the outside and inside of the bag and automatically locks, so it doesn’t open by pulling the sides of the zipper or expanding the bag during the night. To insure that the zipper stays fully zipped, there is a Velcro tab at the top of the zipper, and the Velcro does not stick to the bag’s fabrics.
I tested the Down Hugger #3 on a number of summer and early fall backpacking trips, with nighttime temperatures ranging from 26 to 41 F. I slept under the stars and in various single wall shelters.
MontBell’s sizing is a bit different from other manufacturers; size Regular fits to 5 feet 10 inches and size Long fits to 6 feet 4 inches. I needed a size Long to fit my 6 feet/170 pound frame, and found the fit much to my liking. There is plenty of room inside to wear extra clothing to extend the bag’s warmth, but it didn’t feel too roomy. With the bag lying flat, I measured the bag’s relaxed shoulder girth at 61 inches and extended girth at 72 inches.
The Spiral Down Hugger is indeed stretchy. The left photo shows me lying flat on my back with my arms at my sides; the right photo shows the bag’s expansion with my arms raised above my chest. The benefit of a stretchy bag is the bag tends to conform to my body, so I don’t have to heat up any more inside volume than necessary.
Another remarkable finding from my testing is the bag’s zipper works almost flawlessly, meaning it doesn’t snag very easily. After recently testing a couple of bags with wretched zipper snagging problems (The North Face Beeline and Mountain Hardwear Phantom 32), it’s a pleasure to sleep in the Spiral Down Hugger. (Have you ever had the problem of having an urgent need to pee in the middle of a pitch black night, and the darn zipper snags on your bag?) As shown in the previous section, MontBell uses a thinly insulated flap over the zipper, rather than a puffy insulated draft tube. Eliminating the draft tube allows the zipper to operate more smoothly, but the zipper is not as insulated as it is in other sleeping bags.
I tested the bag’s water repellency by placing a puddle of water on the bag and checking for leakage after an hour. To my amazement no water soaked through. This was verified in my field tests, where the bag did not absorb any water when I brushed against wet tent walls.
I measured the bag’s double layer loft at 3.75 inches, which gives a single layer loft of 1.9 inches. From our table of estimated temperature ratings based on measured loft (read our Backpacking Light Position Statement on Sleeping Bag Temperature Ratings, 1.8 inches of single layer loft translates to about a 30 °F rating, so the Spiral Down Hugger #3 is on target. Please take the time to read the referenced article and note that sleeping bag warmth depends on a number of factors.
The Spiral Down Hugger #3 is not the loftiest bag around with a 30-32 F temperature rating (see comparison table below). I found its warmth to be average. In my field testing, my methodology was to wear my basic sleepwear (dry wool socks and microfleece top, bottom, and cap) inside the bag initially, then add insulated clothing later in the night if I got cold, noting the time and temperature when I got chilly. On nights when the temperature dropped down to freezing just before sunrise, I started getting chilly around 4:00 a.m. when the temperature was around 35 F. After donning my insulated clothing (or better yet putting it on the evening before), I was able to stay warm in the Spiral Down Hugger down to 26 F, and probably could have handled even colder temperatures.
The stuff sack provided is tapered and has two drawcords to stuff the bag down to bread loaf size. It’s simply too tight. In my opinion, the two drawcord design is overkill, extra weight, and overstuffing may damage the down over time. I prefer a stuff sack that does not overstuff a down bag, although it takes up a little more room in my pack.
The following table compares the MontBell UL Spiral Down Hugger #3 with some popular 30-32 F rated ultralight mummy style down sleeping bags. All of the bags have baffled construction, and the data are manufacturer specifications for a size Regular bag.
|Manufacturer||Model||Temperature Rating (F)||Single Layer Loft (in)||Weight of Down (oz)||Fill Power||Total Weight (oz)||Cost US$|
|MontBell||UL Spiral Down Hugger #3||30||1.9||10||800||19||229|
|Mountain Hardwear||Phantom 32||32||2.0||10||800||22||290|
|The North Face||Beeline||30||2.4||10||850+||22||279|
By the numbers, the MontBell UL Spiral Down Hugger compares favorably with other bags in terms of down quality, weight, and cost. It lags a bit in loft compared to the others, but its loft does meet our minimum expectation of 1.8 inches (single layer) for a 30 F rated sleeping bag. Note that its US$229 cost is a great value compared to the other bags, and its weight matches the Western Mountaineering SummerLite bag.
I really like the Spiral Down Hugger’s soft lightweight shell fabric, fit/roominess, non-snagging zipper, hood, and light weight. It’s very easy to fall in love with this bag, and it’s a great value compared to other ultralight 30 F rated sleeping bags. However, it is not quite as warm as the Mountain Hardwear Phantom 32, and definitely not as warm as the Marmot Hydrogen, which I have also tested. I have not personally tested the Western Mountaineering SummerLite. Bag sizing and the Down Hugger’s lack of a down-filled draft tube probably contribute to the differences. That said, the bottom line for me is to wear my camp clothes (wool socks, insulated jacket and pants, fleece cap) in my sleeping bag anyway, and I typically have no problem staying warm down into the mid 20’s F, so the Spiral Down Hugger #3 will do just fine.
Specifications and Features
|2009 UL Spiral Down Hugger #3|
|Hooded mummy with full length zipper|
|Sleeping bag, stuff sack, cotton storage bag|
|800 fill-power down, 10 oz (283 g) size Regular, 11 oz (312 g) size Long|
|Box, 5.5 in (14 cm) baffles|
|3.75 in (9.5 cm) average double layer loft, manufacturer specification not available|
Claimed Temperature Rating
|30 F (-1 C)|
|5.3 x 10 in (13.5 x 25 cm)|
|Size Long tested|
Measured weight: 1 lb 4.9 oz (593 g)
Manufacturer specification: 1 lb 4 oz (567 g)
|Regular fits to 5 ft 10 in (1.52 m), Long fits to 6 ft 4 in (1.93 m)|
|Shell and lining are 12d Ballistic Airlight nylon 0.86 oz/yd2 (29 g/m2) with Polkatex DWR. Fibers are solid core.|
|Spiral stretch system, three-quarter-length two-way auto-locking zipper with inside and outside pulls, draft flap on inside of zipper, Velcro tab at top of zipper, sculptured hood, braided drawcord and cordlock closure on hood, tapered stuff sack with two drawcords, heat transfer logos|