From:  "Ryan Jordan" <bigskyry@b...>

Date:  Sat Oct 13, 2001  6:31 am

Subject:  Owner Review - Nunatak Arc Alpinist

 

 

 

Jerry, make a folder and I'll post this there. - Ryan

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Owner Review: Nunatak Arc Alpinist Down Sleeping Bag

By: Ryan Jordan

 

I had a custom Arc Alpinist down bag made by Tom Halpin at Nunatak Gear in

Seattle (www.nunatakgear.com). Tom was great to work with, receptive to my

design suggestions, and the final product came out exactly as specified. My

specifications deviated from the standard model; deviations were as follows:

 

1. Differential cut to preserve loft in the side baffles. I specified the

extent of the differential and Tom followed this specification exactly.

Differential cut involves making the inner shell narrower in width than the

outer shell so that when the bag is closed, the inner concentric ellipse is

smaller than the outer concentric ellipse and compression of the down at

locations where the radius of curvature is sharp (i.e., the sides) does not

occur. This is the approach used by Western Mountaineering to maintain

excellent side loft in their continuous baffle bags.

 

2. Inside fabric of 0.85 oz nylon, outside fabric of 1.2 oz Pertex

Microlight. Rationale was light weight, next to skin comfort, and partial VB

effect of the very tight 0.85 oz nylon weave, and breathability with some

water resistance of the outer shell.

 

3. Custom length and girth dimensions (I am 5'7" 150 lb).

 

4. Down fill to achieve average 3" loft throughout chest section, increasing

to 5" in footbox. These values are for top-layer loft only. Average loft of

sleeping bag's two layers is 5.5 to 8.5 inches. Since this was a hoodless

bag, I was shooting here for a 30 degree temperature rating wearing only

long underwear and a balaclava when the bag was in a bivy sack and exposed

to high winds and cold and wet conditions. Preliminary tests suggest that

this is reasonably accurate, although YMMV.

 

5. Five inch baffle spacing instead of the standard 10" for better down

control. Also, 3" interior baffle height.

 

This is a hoodless bag with a shockcord drawstring at the neck. There is a

foot pocket region. This is a top bag that can be used as a quilt, or

secured around the underside of a sleeping pad with two straps (standard

version). I had Tom add a third strap near the head end of the bag for

additional security. I plan to use this bag in conjunction with a

Polarguard-insulated balaclava or the down hood of a jacket for my typical

2- and 3-season adventures and with a hooded down jacket and down pants for

winter trips.

 

My bag weighs 21.4 oz.

 

Field Performance to Date:

 

I've worn long underwear in the bag and was comfortably warm with

temperatures into the low to mid 30s (Teton Range, Wyoming) with and without

a tarp (bag in a bivy sack) and with breezy winds. I've worn long underwear,

wind jacket, vapor barrier pants, and hooded rain jacket with a polarguard

jacket hood and was comfortably warm into high teens with the bag in a bivy

sack on windy and/or snowy nights. I plan on testing this bag this winter

with clothing that includes my normal winter clothing ensemble: vapor

barrier shirt (3 oz), pants (3 oz), and socks (1 oz), merino wool long johns

(16 oz for the set), hooded down jacket (16 oz) and down pants (12 oz), and

down booties (4 oz), in a bivy sack (Pertex Endurance, 13 oz). I'm

anticipating the ability to sleep comfortably warm down to zero degrees with

this system. Keep in mind, this is a 21.4 oz sleeping bag. That would be

zero degrees. 21.4 oz. Zero degrees. Yes, I'll report back.

 

The key to sleeping comfortably warm with a bag of this design at cold

temperatures is to:

 

1. Minimize the interior volume of the bag by using a reasonably narrow

(body width) pad and cinching the straps around the pad in order to prevent

drafts. All field tests described above were performed with a 48" long, 20"

wide Mt. Washington pad. Since I'm not a particularly wide person, I plan on

reducing pad width for 2- and maybe 3-season use to 18" or even 16".

Alternatively, one could simply cinch the bag up and sleep on top of a pad.

I've found both methods to work well, with the former possibly being a

little warmer for the sleeper that tosses and turns during the night, since

drafts are effectively locked out via the straps under the pad.

 

2. Prevent neck drafts by (a) cinching the drawcord tightly, and (b) wearing

a hooded jacket. I've had very good success wearing a hooded rain jacket

(with a Powerstretch balaclava or other type of insulated head covering) or

a hooded insulating jacket, like the GoLite Coal or a hooded down jacket.

 

I won't report the cost of this bag due to the extensive customization

involved. However, I thought that the price premium that was charged over

the standard bag was nominal compared to the added performance of my design

modifications.

 

Reminder: This will likely be my mild winter bag. It's 21.4 oz. Did you get

that?

 

Ryan Jordan

Bozeman, Montana

http://ww.BackpackingLight.com