Montbell Seamless Down Sleeping Bags

A fleece beanie is one of the reasons I’ve not had to wash the MB spiral stretch bag.  No chin strap appears necessary.  Maybe that is due to the swelled head.

Also, have never noticed any cold spots, even though the fill is just enough to maintain the shape of bag.  Not sure, but the stretch, coupled with absence of friction from the inner fabric, may be involved.

Roger

Who wants to sleep in a straight jacket anyhow?

One thing I’ve learned from this site is that people’s sleep preferences vary widely.

After a few years of experimentation I’ve found that I actually prefer sleeping in a bag than a quilt. And I don’t even need all the width in my current bag – my next iteration will be narrower to save weight.

I guess that’s why there are so many options on the market – we all prefer different things.

Well said Geoff.

I’m a happy narrow mummy user…

Who wants to sleep in a straight jacket anyhow?
Which is a big reason I switched from a bag to a quilt. I could not waggle my legs in a bag – one leg straight and one bent. But With a quilt, dead easy. I just waggle away.

Then I realised that a quilt is what we use at home as well. After all, how many people sleep at home in a bag?

Cheers

@geoffcaplan, the fill weight can be found here by going to the specifications for each bag.

Well, that’s interesting. UltralightMountainGear is a great retailer, and they are offering more complete specs than Montbell themselves.

So there is only 300g/10.6oz of down in the #2 Hugger rated at -6°C / 21°F.

This is the same fill as my old Rab rated at 2°C/36°F with a similar quality of down.

So they are claiming that the spider yarn system is adding a full 8°C of performance.

A comparable mummy with conventional baffles would more typically have 450g of filling, which is 50% more.

A PHD mummy of the same rating is 70g/2.5oz heavier, so it seems that some of the saving in down is lost in the weight of the yarn.

With so little down in the bag, you do wonder what would happen if it got damp, or if it lost some loft between washes.

On the other hand if this system is robust, it’s good news for geese…

Roger

Interesting to hear how you guys do it, but you are mainly talking about a feature that’s pretty unique to your system. I was talking about a conventional mummy hood.

So the only point I’ll challenge is the value of a neck closure and baffle. You claim that only a face closure is required, but most of the good manufacturers disagree. Valandre in particular is known for their wrap-around neck baffle. You’ll find it on cold weather bags from most other respected brands.

With my own mummy, I find that performance improves markedly if I cinch both the neck and hood compared to just the hood alone. The seal around the face of a conventional mummy is too leaky on its own.

The Hugger #2 I’ve just been looking at offers a full neck seal too, as does my modestly rated Rab.

Hi Geoff

You are quite right to point out a big difference in how the hood works between quilts and bags. We do have some serious winter bags and winter quilts as well as those ‘summer-weight’ quilts, and the difference around the neck is as you say.

Looking a bit more deeply into how they work, I think that a big difference is how much ‘quilting’ or material is available around the neck. With a trad bag, there is a considerable restriction on what we can do at the neck level, a restriction which is not there with a quilt. A good neck baffle seems to be very necessary with a bag.

Cheers

@Geoff, I was also surprised to see the down fill weight:temp rating ratio for the Montbell bags.. wonder if the numbers on ultralightmountaingear are accurate, but maybe it confirms my suspicion that Montbell doesn’t publish them because they think fill weight shouldn’t be compared with traditional mummy bags due to the different construction and materials. From my impression of MontBell, they don’t seem like the type of brand to market higher temp ratings than their products can achieve, but we’ll see.

I wasn’t familiar with the neck baffle construction in some mummy bags, sounds like the idea is that the benefit of a more reliable seal (neck > face) outweighs the benefit of sharing an air pocket around head and body? What’s the advantage at this point relative to a neck-seal quilt and garment hood that extends past the neck seal, or a jacket? Maybe better loft can be maintained since the mummy bag’s hood isn’t fitted as tightly around the shoulders/neck/head?

I always like to wear a beanie in my quilt. I hate hoods, even on my cold weather bags (WM Puma for deep winter). I roll all around as I sleep and more often than not wake up with my face buried somewhere in the hood. With a standard buff and my Blackrock Gear original beanie, I am good to about 20*F. YMMV

I always like to wear a beanie in my quilt. … With a standard buff and my Blackrock Gear original beanie, I am good to about 20*F. YMMV

Me too. Buff and a fleece hat.