Sleeping Bags

Thanks for your input guys - very interesting! In answer to your question, Papa Dragon, I have never used a liner and don't intend to. Roll on Winter so I can put the Zpacks bag to the test...........

A higher fill rating makes a big difference in weight. Mature down (from adult birds) is of a much higher quality and fill rating, so you can use less down to achieve the same temperature rating. Also, mature down is more resilient and will last far longer than down of say 650 fill. Lastly, where the down comes from also plays a role in the quality thereof. From what I've read it seems that Poland/Hungary produces the best and warmest down.

Bottom line, the higher the fill rating the lighter the bag will be for the same temperature rating. Same applies to down jackets as well.

Thanks for the link JonWells. I am pretty sure the picture in that link you posted answered my question.

(Sorry the image won't show, but you can view it through the link JonWells posted 3 posts up)

I also did some reading last night and I agree with Riaang. You can buy a "900 fill power" product from China (aliexpress or similar) but I don't think you will survive a Johannesburg winter night. If you look at well known brands like Big Agnes, Klety and Marmot they all have similar specs than the Z-Packs and are filled with the best quality dawn. Thus the high price, for the best specs.

I guess is like comparing a 3 liter GWM pickup with a 3 liter Hilux. Both are "3 liter" but not the same...

High quality down is pricey regardless of brand name or country. Sadly we in SA have to compete in US Dollars in a market that has a shortage of mature and pure goose down, the bulk of which comes from China and not eastern Europe.
In the past First Ascent used only 800 - 900 fill power for sleeping bags. I am not sure if this is still enforced but I suspect for their top bags like the Blue Wolf and Ice Breaker this will still be the case (if it can be sourced at current USD rates).


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kbresler wrote:

In the past First Ascent used only 800 - 900 fill power for sleeping bags. I am not sure if this is still enforced but I suspect for their top bags like the Blue Wolf and Ice Breaker this will still be the case

Thanks. If that is still so, then the fA temperature rating system is a lot more conservative than the EN13537 standard.

I believe there is more to how warmth is achieved than the type of down used - e.g. where it is placed, shape, type of zip, internal baffles etc.

Here's an article on the different design techniques used in sleeping bags:
www.crux.uk.com/en/sleeping-bags.php?info=38

Riaang wrote: I recently picked up a NF Blue Kazoo -10 degrees, weight in the large bag about 1,4kg (the normal size is 1,25kg) with treated down (probably not as good as synthetic when wet but better than non treated down). Was on "special" which made it just slightly more expensive than my IceBreaker (also the long model). So, basically same price but weighing nearly 500g lighter and definitely warmer, with treated down.

Tested it on one of the hottest days Pretoria had in living history and nearly died! Climbed into the Ice Breaker afterwards and it was definitely not as hot - probably due in part to the larger area that needs to be heated up. Think it was about 5cm's wider on either side.

Hi Riaan, sorry for putting you on the spot. But what you said in a previous post kind of links with what ghaznavid just said in the previous post. The design is better in terms of there is less air around your body to heat thus more efficient. As you said the NF bag (-10°C) is 500g lighter than your previous FA (-8°C) but you think it feels warmer even though the NF bag only has 650 fill treated down.

I am also beginning to think it's not all about the down but also about the fabric used, zip, baffles etc.

Ghaz, thanks for the link to the Crux site.

Excepting the sewn-through method of baffles, they list 4 other types of baffle construction, which they state are in order of increasing thermal efficiency. I'm definitely no expert in this field, but wonder if there is that much difference in thermal efficiency of the different construction methods, or if this is marketing spiel.

The diagrams of the cross sections show white areas which are obviously meant to represent cold spots and channels. In reality though, down goes everywhere, even where you don't want it to. For example, the mesh that is used in baffle construction is definitely not down-"proof", and I am sure that in reality inside the baffles, the down meshes into the mesh.

I would have thought that average loft, baffle height and if there are any cold spots along zips, footboxes etc affect the thermal efficiency the most, and that the fill power (weight needed to create that loft) would affect the weight to achieve that thermal efficiency.

Thoughts?

I would think that it isn't only the lack of down that's a problem - at the sewn spots the down will be compressed, so even if it is there, it won't be as effective.

My experience is this - my K-Way Kili 2 bag is 1.8kg, I seem to recall it being 800 fill down, but can't find it online now, and is supposed to be a -8C bag. My 1.4kg MHW Pinole is a -5C synthetic bag and is considerably warmer, despite being lighter.

The MHW Lamina range of sleeping bags, IMHO, are the best synthetic bags on the market right now. My Hyperlamina Torch is a -14C bag at 1.8kg. They use plastic welding to attach the outer and inner fabric to the large sheet of hollow-fibre, thus eliminating the cold spots.

So basically, this makes sense to me, I don't think it's just marketing.