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eric chan
(bearbreeder) - F - M
Re: It's just loft on 08/07/2012 00:26:21 MDT Print View

However, rereading your posting, I realize I must have failed to communicate properly, both northface and lafuma sold their bags but did not list the actual comfort rating, they listed the mid rating, where you are kind of miserable but will survive the night ok. Western Mountaineering lists the actual comfort rating. That's why nf and lafuma are frauds and why the good companies like wm, ff, and a few others, aren't. And that's, again, about loft. And those good companies tell you precisely how much loft you are getting with each bag.

bull ... the summerlite is a 32F rated bag and is en-rated lower limit tested to 34F ... if anything their rating is exaggerated ... richard nisely has shown that actual testing is what matters, the correlation between "loft" and insulation is not as great as people assume

Temperature Rating. EN 13537 tested:
T comf: +6ºC
T lim: +2ºC
T ext: -14ºC

the bottom line is to LOOK AT THE EN-RATING ... a fancy doodah $$$$ bag that test to 30F is not going to be any warmer than an el cheapo bag that also test to 30F when new ... all other things such as fit, etc ... being equal

Edited by bearbreeder on 08/07/2012 00:30:24 MDT.

Jeffs Eleven
(WoodenWizard) - F

Locale: Greater Mt Tabor
Harold on 08/07/2012 00:39:28 MDT Print View

"Getting all caught up in the details gets confusing, needlessly"

Confusing statement from a member on this site.

Needlessly getting caught up in the details is the purpose of BPL

Edit- FWIW I get cold when I sleep in my 40deg in 40deg weather. I write it off as me being a cold sleeper, not the whole EN rating being a farce. -Bring my 30deg bag instead

Edited by WoodenWizard on 08/07/2012 00:42:16 MDT.

Harald Hope

Locale: East Bay
let's check bpl itself on 08/07/2012 10:53:46 MDT Print View

Eric, where did you actually find the wm en ratings? Thanks for the correction. So that makes my body, despite its age, still a reasonable judge of bag temp, since I thought 32F for the summerlite might be pushing it. But it's in the ballpark, maybe within 8 degrees, the bags I'm noting are bad are not in the ballpark, they are maybe 15, 20 degrees off in rated temp, and far less loft. Keep in mind the summerlite has continuous baffles and you can rearrange the down to be more on top if you want. Looks to me then like nf/lafuma are using lower mid ratings, and wm using upper mid, but because you can move the down around in wm, I suspect you can get fairly close with them if you do it right.

Let's see what bpl says re sleeping bag temperature ratings.

Consequently, the best we can do is to measure the loft and key performance features of the bag, comment on our subjective experience near the temperature rating of the bag, and ask you as an informed consumer to compare it to the loft and temperature ratings of bags from other manufacturers in order to make a wise decision. Nevertheless, we recognize that some guidance in correlating a bag's loft to its warmth is useful to consumers. Table 1, below, represents our best effort at such a correlation:

Temp (°F) Loft (in) Temp (°C) Loft (cm)
50 1.2 10 3.1
40 1.5 4.4 3.8
30 1.8 -1.1 4.6
20 2.2 -6.7 5.6
10 2.6 -12 6.6
0.0 3.0 -18 7.6
-10 3.5 -23 8.9
-20 4.0 -29 10

One key thing to understand about sleeping bags is that if they say it has, say, 3.5 inches loft, that counts top and bottom, and it's the top that keeps you warm, and the sides, so that actually means 1.75 inches, which is in the 40 degree range, as you see from the chart. My guess is that good bag companies that use good down and list the loft know that it's about the loft and down/fill quality. Compare similar quality down and loft, and you'll probably be in the same temp ballpark.

Keep in mind, if you aren't aware, that Elijah is 14, and trying to get into backpacking, so when I say, keep it basic to avoid confusion, that's really what we should be doing. And since loft is what bpl offers as a reasonable tool, just like every other authoritative source, like military specs, etc, that's what a beginning backpacker should use, and grown up ones, and I believe it is largely what they use, when you strip away the extra words etc.

We can debate the fine points of heat retention of different fill materials, humidity resistance, and construction methods to our heart's content in some more focused and dedicated threads in the future, and dig up older ones from the past.

By the way, this type of fine grained analysis is what brought me to bpl in the first place, and it was the absurd failure of some new lafuma and nf bags to even remotely approach their alleged ratings that made me start realizing that it was time to learn what's really going on here, coupled with a trip to Northern Norway, where very well intentioned but totally clueless relatives ended up freezing my butt off camping.

Elijah, you can learn a huge amount from these threads, if you read through them, but it's also important to realize that often what appear to be debates or disagreements are actually just people fine tuning and adjusting their understandings. This is how gear, and other, geeks, do things, and it results in amazing information, I have certainly brought my own level of understanding up by a very very large amount by reading these forums now for some time.

Edited by hhope on 08/07/2012 11:04:38 MDT.

eric chan
(bearbreeder) - F - M
BPL on 08/07/2012 11:01:59 MDT Print View

BPL needs to update their bag ratings ...

would you rather have

1. assumption of "warmth" based on loft, and assume there is a strong correlation between em ... look at richard nisely posts for why this is not the best

2. assumption of "warmth" based on the quality and amount of fill ... more accurate

3. actual real measured "warmth" tested in independent laboratories according to an internationally recognized and EU legislated standard which is considered conservative ... most accurate we have so far

everyone on BPL and BPL itself claims to be about scientifically measured results ... here we have a standard that is recognized, adopted, tested, etc ... by real scientists (not some DIYer) with real equipment ... its amazing to me how many here just ignore it when it doesnt suit em , ie the bags aint one of their fancy favorite brands ;)

Brett Peugh
(bpeugh) - F - M

Locale: Midwest
more diverse on 08/07/2012 14:07:53 MDT Print View

I would like a more scientific way so that things like the heatsheets and other option could be mesaured also.

Mary D
(hikinggranny) - MLife

Locale: Gateway to Columbia River Gorge
Sleeping bag temp ratings on 08/07/2012 20:54:45 MDT Print View

I agree with Eric. There have been lots of criticisms of the EN13537 ratings and testing system, but IMHO they are the most objective criteria we currently have. It's discouraging that they are often misused here in the US. I keep seeing the "extreme" number (the temp at which you hopefully won't be dead of hypothermia in the morning) used to rate bags (I don't think that number should be there at all), and seeing the "lower limit" (for men/warm sleepers) number used to rate women-specific bags.

While I love my Western Mountaineering sleeping bag, it's quite discouraging to have to go to UK websites to find their EN13537 ratings! They sell their bags in Europe, so they have to have them tested--why aren't the results on the WM website? What are they trying to hide?

For a good layperson's guide to these ratings, read this blog entry from Philip at SectionHiker:

Edited by hikinggranny on 08/07/2012 21:00:19 MDT.

Erik Basil
(EBasil) - M

Locale: Atzlan
K.I.S.S. but not on the intarwebz! on 08/08/2012 14:44:49 MDT Print View

Hi-larious, how the discussion can turn so needlessly esoteric. (Please, count to ten realize your "points" might be "true" even though they actually "don't matter at all")

SHORT ANSWER, without the BS, is still "Kelty Cosmic Down 20" in the shortest length that fits the hiker. There's a thorough review of the item on this website. It is, simply, not an esoteric product but rather one that fits the OP's criteria with laser-like precision.

Now, let me paste in some statistics from something... :)

Tyler Johnson
(riemannia) - F

Locale: Northeast Georgia
Sew your own! on 08/08/2012 15:37:55 MDT Print View

If you have time (a couple hours) and access to a sewing machine, you could sew a zipperless, hoodless sleeping bag or quilt with synthetic insulation for about $50

3 yds 2.5 oz Climashield APEX from Thru-hiker @ $10/yd
5 yds 1.1 oz nylon ripstop from DIY Gear Supply @ $3.20/yd

Plenty warm to 45 degrees and easy to sew. My first ever sewing project was an APEX quilt; it's really not difficult to sew something this simple; it's just cutting some big rectangles, pinning them down, and then simple straight line stitches.

If you don't have access to a sewing machine, you're out of luck in this direction though.