Why are there so few sleeping bags with centre zips? Short or long?

Our Convert and Conundrum are hoodless bags, not quilts. They have double draft baffles behind the zipper. We do make them to be used with a balaclava instead of a built in hood, but that’s to allow you to spin the zip to any position you want and have head insulation that moves with you instead of forcing you into one position.

-Tim Marshall

Founder; Enlightened Equipment

When first making a bag, it became obvious why the side zips are common and the center zips are not:  Side zips are less complicated, and therefore cheaper to make, whether with baffles or slab construction for synthetics.  Designed a solution to the complexity of patterns for the center zip, and posted it too long ago to go hunting for the link.

Note that most of the images shown above are not true center zip bags, as they are hoodless, too short in the zip, partial length, or as pointed out, are quilts,    The center zip needs to open enough to take the legs and feet out and lay them on top when its gets too warm, also to make getting in and out easy in the night.  Having the center zip makes it much easier to zip up and down when lying on the back or side.  Although a side sleeper, I rotate from side to side, so begin on my back before selecting which side to rest on first.  The amount of weight increase from a 1/2 to 3/4 zip is miniscule.  As for the hood, although a fleece cap is worn, would never buy a bag without a hood because it greatly increases warmth when needed.

The upshot is that warmth for weight, stretch, easy zipping, good DWR and durability are all greater priorities than a center zip, so use a Montbell spiral baffle design, and put up with the slightly lesser convenience of the side zip.  Although haven’t had many down bags, the Montbell has lasted for years and made me a convert to down.

Totally zipless bags are rare in America but still very common in England, look at the UL offerings from PHD for instances; and I grew up here in Oz using wriggle in bags and until I bought the monster bag for Alaska I had never owned a bag with a side zipper. I had however owned and used an UL winter bag with a short centre zip, sold it to fund a warmer bag more suitable for a Scottish winter and my wide shoulders. I have recently purchased a pair of side zipped sleeping bags for car camping and I find them inconvenient although my beloved wife likes hers, but these are S2S bags with zippers on both sides to convert to a double quilt if desired.

Partly an academic question on my part as my walking and ski touring days are almost over but I do find it interesting that world wide the military are reverting [ for the most part] to centre zip sleeping bags

Edward – you’re right – zipless bags are quite common in the UK with hard-core alpinists, and most of PHD’s  most minimal offerings are zipless. A touch lighter, and eliminates the main failure point.

My first modern bag was made for me by Rab Carrington on his kitchen table (it’s now in the RAB company museum).

It was zipless, and I used it for decades in a wide range of conditions. Worked pretty well. When it was hot, I would just pull it down to my waist. Getting in and out wasn’t a significant issue, even when wearing down clothing. Perfectly workable in a lightweight bag.

Speaking of PHD, they offer short center zips on their Superlight, Lightweight and Tech-light custom bags.

I know of these PHD bags. But I am reluctant to deal with a company that refuses to tell me dimensions, fill weights, loft measurements and other details and whose products are not EN tested; even so I was considering buying a Minim overbag [ XLong + XXWide] until the Aussie dollar crashed.

Edward

Yeah – I’ve run into that too – hard to understand the culture there. Though you do get fill weights with the bags.

Also, they still don’t offer hiking quilts or hoodless bags, so they’re a bit behind the times.

On the other hand, you’ll find lots of rave reviews that agree that the bags are well built and conservatively rated. And the customisation options are unmatched.

I am headed away to the snow for some skiing in a few days. I put my old Everest summit bag in to the factory for a full rejuvenation and it won’t be ready for another couple of weeks. So for my first weeks camping I will be using my half bag in combination with my Nunatak overquilt and a LW parka, I’ll be warm enough but not as comfortable as I would be if using a proper sleeping bag with a hood.

So I am also going to take a new purchase and try that out

At 900grams it actually weighs less than my old Goretex bivvy bag although the bivvy bag is bigger but climbers bivvys usually were bigger