I need a warmer sleeping bag system Opinions needed

[Edward John M]

My mate has a full roll; or what’s left of it; of the gold foil backed flooring underlay.

4mm thick PE film; PE foam and the reflective foil on top

Similar to what we use up the hills in winter here.

I got my end roll from a skip at a building site, cost me a can of cold coke; there was 11 metres left on it

If I need extra I’ll grab some from his stash and tape it to the floor semi-permanently

If I use a pulk the tent goes on top rolled out flat to put up fast if need be

[JayC]

In my personal experience, at sub -35c temperatures after 3 or so days there starts to be a lot of moisture in the bag, and the warmth drops off.    I haven’t tried layering bags, but I expect it could work well.   I would double

So your trip is 90 days total, and each “leg” or the longest time between resupplies / some place to warm up would be 12 days?   If so I would get a vapor barrier sack.    They are (or can be) very unpleasant to sleep in, but if I was looking at more than say 3 days of nights of sub -35c weather I would be using one.

I would also error on the side of caution – 55c is really, really cold.  The coldest I have experienced is -51c, and at those temps a lot of things no longer function all that well.  Fabrics get stiff, plastic brittle, etc.

If I may ask – where and when are you going?  Spring time?  That can make a big difference – where I live (interior Alaska) we get lots of solar warming during the spring, but still have very cold nights.  In the main part of winter we get cold days and nights with almost no warming during the day :)

Have a great trip!

[Edward John M]

To be honest Jay I have no idea where I’m going

it is a bucket list trip and I’m spending my childrens inheritance to do it, I’m not getting any younger fast and all of my contacts seem to be in the same age and decrepitude bracket

[Chris C]

Did you get your sleeping bag yet?

In customizing my WM Puma -25F/-32C, I opted for the foot box overfill plus the Gore Windstopper. The thinking behind Gore Windstopper is (1) in case a shelter should fail and I would need extra protection, and (2) it may retain heat a bit more than microfiber. The drawback of GWS is that it’s stiffer than microfiber and is more annoying to stuff into a pack. It costs a bit more, too.

The WM rep said that most customers choose microfiber over Gore Windstopper. The WM Ponderosa 15F/-9C is only in microfiber and that fabric feels luxurious. If I got another WM bag, I would easily go with microfiber.

Feathered Friends uses Pertex Shield for their sleeping bag shells. Their goose down insulation is from the same source in Poland as Western Mountaineering but FF uses 900+ fill vs WM’s 850+ fill.

One more thing, my Puma is still too cold in 15F weather unless I use disposable hand warmers because I don’t generate enough heat on my own.

A camping buddy of mine uses an Uco candle within his tent for both minor warmth and to handle any would-be condensation. I haven’t tried it yet.

 

[Edward John M]

Not yet, during this winter here I have tried a few and as a side sleeper I have found most new / modern iterations of the winter sleeping bag have the zipper in the wrong place [ my current winter bag has no zip at all]

I am saving my pennies to have Nunatak sew me an Extra Large Arc Alpinist 20F, where the zipper is in the right place for comfort and ease of use

The combination of the Alpinist plus a down jumper and a half bag plus the overquilt should be all I’d ever need and if not there’s rum

[Chris C]

Where is the right place for a zipper if you are a side sleeper? I sleep on both my right and left sides.

[Edward John M]

Centrally, which is where most zippers were for many years. Most of the winter bags i have owned over the decades have been zipperless but I did own one from Egge that was a central zip and that was magic

 

[Roger Caffin]

Centre, no question. Hood then on top of your head.
And that lets you turn it into a good quilt too.

Cheers

[Jerry Adams]

Center zipper on bag much better.  You can unzip and push bag to each side when it’s warm.

Side zipper – you bush bag to one side and it gets into the dirt, and on the other side the dirt gets blown inside your bag.

I didn’t know that anyone makes bags with center zips

[Edward John M]

Almost all military bags in Europe have gone back to the short centre zipper, GoLites original bags that got such rave reviews were centre zip but in down so far I’ve only found them from Nunatak and TNF

https://www.thenorthface.com/shop/inferno-40f-40c-2

https://www.thenorthface.com/shop/equipment-sleeping-bags-above-25f/superlight-35-2?variationId=AGY

https://nunatakusa.com/sleeping-bags/120-alpinist-20-regular-mummy-bag.html#/liner_fabric-1_0_oz_sq_yd_taffeta_black/shell_fabric-1_0_oz_sq_yd_pertex_quantum_black/sleeping_bag_length-short/alpinist_foot-34_snug/alpinist_zipper-28_short/alpinist_width-30_standard/new_down_type-900_fill_power_goose_down_rds_certified/new_quilt_bag_down_overfill-no_overfill/alpinist_temp-20

 

In synthetic tho there is a better selection from TNF

[Chris C]

I got swept up with WM bags and completely overlooked TNF center zip bags. Nunatak is new to me and look forward to your review.

However, in putting together a hammock setup for my son, I got an Eddie Bauer Flying Squirrel 40F bag (US $299 retail; $122 Amazon; $100 eBay), I thought the center-opening of the wings would be easier to get in and out of a hammock. I liked it so much, I bought a second one for myself. It has

In warmer weather in a tent, I use this as a blanket. My feet never seems to stay in the foot end because I mostly sleep on my side curled in a fetal position and occasionally like DaVinci’s Vitruvian Man. I really enjoy this design and am pondering a MYOG winter version with thicker loft, collar and draft tubes a la WM.

 

[Edward John M]

Interesting design, it also looks like it would make a good liner bag

[Roger Caffin]

I would not use it as a liner BAG, but I can see that it might make a rather good sort off quilt to go under an over-quilt in the winter.

Sue and I favour our 600 g summer (MYOG) quilts, which we can double over the two of us if it suddenly turns cold, but we also have a larger double over-quilt (also MYOG) which has worked very well in the snow over the two of us. Using an over-quilt has not only kept the two of us quite warm in way-sub-freezing conditions, but also means that our summer bags stay very dry. Any condensation which occurs is in the over-quilt, which we manage to dry off fairly easily.

Cheers

[Chris C]

@rcaffin

I’d love to see your MYOG quilts. Could you post pics or a link to pics?

We took the flying squirrels camping in 65F nights with a Hilleberg Jannu with the inner tent’s mesh revealed and it was perfect. I read some reviewers used the flying squirrel within other sleeping bags or under other quilts to add warmth. I haven’t tried the bag-within-a-bag combo yet. Maybe the flying squirrel will make my FF Swallow 20F bearable for me in 15-20F nights.

[Roger Caffin]

Article at https://backpackinglight.com/MYOG_down_quilt_bag/

Cheers

[Edward John M]

I have used double bags and the combination of a large outer bag and half bag with parka for many years.

The new Brooks Range half bag that my beloved bought me is much bigger than my old half bag and I will need to specify a bigger bag for it to fit inside. It looks like Nunatak are going to get my business so now I am wondering how much overfill I should order to go with the design if I am venturing into truly cold conditions using the Nunatak 20F/-7C rating as the starting point. The BR half bag is rated at-6C so combined that’s about -20C and room to wear my clothing inside to boost it to lower temperatures if needed and I do have the synthetic overquilt as part of the system [ add another 5C] but that is mainly to keep my feet warm and to hold the mattress system in place and to protect the down sleeping system from condensation

[Edward John M]

A couple of points have been raised by people who question my sanity.

How accurate is that BPL noted formula for calculating double bags?

And if I have a double bag rated for -40C what would be the survival temperature>??

Somebody just informed me that last winter they recorded -74F in the Brooks Range while they were out in the back country, would using the extreme temperature approximation in the arithmetic give a reasonable answer?

This same individual also told me he used two nested -5C bags and comfortable at -40C

When looking at EN ratings I use the female temperatures to account for my age and using two compatible bags each rated to -5C the dual bag calculation is -21C, but looking at the PHD site they give an estimate of -28C for a similar set-up Is this really much of an issue

[James Marco]

Edward, at extreme low temps, the BPL formula is not all that accurate. It is optimized for around 0F. At around -45FF/-43C, the calculations break down. Wind, ground, tent, sheltered area vs open area, all play a very important part. Anyway, you need about 11″ to 12″ of total loft for a bag. You can use two or three bags to make up what you need.  However, the assumption is you will have enough space inside of one to accommodate the full loft of the other(s). Though loft is only about 1/2 of the meaningful warmth of a bag. Convectional losses due to compression become increasingly important with the amount of loft you have…the number of layers you have compresses the others. Additionally, extra heavy ground insulation to prevent conduction losses make up the other 1/2 of a good system. Generally a good sleep system for -40 or so will weigh several pounds more than an entire UL kit in summer. *Do not* underestimate any of it. -40 can kill quickly. This is not a time to experiment. One night at 40F may be overly warm. The next night at -40 will be extremely cold. Conditions will trump the actual temp…even in a double walled tent.

Where you headed? Antarctica?

[Roger Caffin]

Somebody just informed me that last winter they recorded -74F in the Brooks Range while they were out in the back country,
An interesting claim.
According to Wikipedia, the lowest recorded temperature in the lower 48 States of America is -57 C or -70.6 F, at Rogers Pass, Montana, on 20 January 1954. So I would be a bit cautious about accepting his claim.

Cheers

[Edward John M]

Alaska in winter, but 150mm of insulation isn’t hard to get if I can wear my parka But it is heavy

Outer bag is still under comsideration

My Everest bag has 150mm of loft 75mm of insulation but naturally designed large to wear a down suit inside, trouble is that my parka has more loft than a normal Everest down suit

My assumption all along was that I would need a really good mat, and also that the US army insulation tables were way off under -25 for older folk

[JayC]

Somebody just informed me that last winter they recorded -74F in the Brooks Range while they were out in the back country

I don’t know if it was actually -74F in the Brooks range this winter, but that temperature isn’t all that unlikely – the “official” record is −80 °F / −62 °C January 23, 1971 at Prospect Creek, which is near the Brooks. The area doesn’t have a lot of weather stations, and most of those stations are not calibrated for sub -40f, so the official record keepers ignore their readings. It is hard to find a thermometer that actually works at those temperatures and is anywhere near accurate.

Are you headed to Alaska? If so, what part of the state, and what time of the winter?

[Roger Caffin]

the “official” record is −80 °F / −62 °C January 23, 1971 at Prospect Creek, which is near the Brooks. The area doesn’t have a lot of weather stations, and most of those stations are not calibrated for sub -40f, so the official record keepers ignore their readings.
I would be interested in the source for both parts of this claim (temp and ignore). I cannot find it in a simple web search.

Cheers

[Edward John M]

Open plans Jay, a lot depends on LOTNs timetable for their instruction camps and what my contacts are doing. I will have 90 days of visa time

I need to be ready even if the trip doesn’t go ahead I need to be prepared

It just made sense to me to use a double bag system because I would never need a SnowyOwl here in Oz but -18C/0F is a good basic bag for an Australian snow season

[JayC]

I would be interested in the source for both parts of this claim (temp and ignore). I cannot find it in a simple web search.

See:
https://en.wikipedia.org/wiki/Prospect_Creek,_Alaska

(It is the first hit on google, for prospect creek alaska weather :) )

If you don’t believe me, here is the official climate stats from https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?ak7778


YEAR(S) JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN
1970 ----- z ----- z ----- z ----- z ----- z ----- z ----- z ----- z ----- z -35.00 a -62.00 g -68.00 a ----- z
1971 -80.00 d -64.00 -62.00 u -43.00 b 7.00 a 20.00 i 34.00 x 24.00 a 15.00 c -32.00 a -52.00 b ----- z ----- z
1972 -70.00 b -56.00 -54.00 -34.00 ----- z 29.00 33.00 32.00 v 6.00 b -22.00 b ----- z -54.00 ----- z
1973 ----- z -55.00 ----- z -15.00 18.00 30.00 ----- z 22.00 7.00 c -20.00 -50.00 a -46.00 ----- z
1974 -60.00 -63.00 -56.00 -22.00 7.00 b 28.00 c 32.00 i 19.00 ----- z -8.00 b -48.00 -57.00 ----- z
1975 -58.00 a -37.00 a -29.00 -21.00 ----- z 31.00 31.00 30.00 11.00 -33.00 -33.00 -49.00 b ----- z
1976 -43.00 -55.00 -29.00 -18.00 24.00 32.00 34.00 33.00 21.00 -21.00 -21.00 a -41.00 -55.00 a
1977 -39.00 -41.00 -39.00 ----- z 10.00 34.00 35.00 17.00 11.00 a -21.00 -36.00 -47.00 ----- z
1978 -25.00 -46.00 -23.00 -16.00 20.00 a 34.00 37.00 25.00 7.00 -12.00 -30.00 -45.00 -46.00 a
1979 -37.00 -50.00 -29.00 -19.00 25.00 25.00 37.00 28.00 7.00 -0.00 -15.00 -49.00 -50.00


This isn’t the coldest temperature recorded in north america, I think Snag has that record, and is a bit colder.

About ignoring low temperatures in remote weather stations, there is some discussion of it here: https://wattsupwiththat.com/2012/01/30/bitter-cold-records-broken-in-alaska-all-time-coldest-record-nearly-broken-but-murphys-law-intervenes/

The jist of it is these stations use thermistors that are not really calibrated below -40.

[Roger Caffin]

Ah, I see. Bear in mind that I don’t know where Brooks Range is: can I assume it is in Alaska?
I had assumed (always a mistake) that we were talking about the ‘lower 48’. Yeah – I can imagine parts of Alaska getting a bit cold …

Cheers

[Author]

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