"2005 Fairydown Everest and Scorpion
The 2005 Fairydown Everest and Scorpion models combined the highest quality fabrics and down fill with some exciting new innovations, resulting in the ultimate in cold climate sleeping bags.
Building on the experience of the Superlite project I again utilised a radical differential cut and then took this a step further by maintaining constant thickness over the whole bag. The intention was to reduce heat loss and any excess engineering required to rebuild thickness where it has been taken away. So rather than the bag tapering in profile from full thickness and insulation to no thickness (and therefore no insulation) along the zip and hood edges, maintaining constant thickness allowed the same level of insulation (thickness) at the hood and zip edges as anywhere else in the bag. A fabric wall along the zip and around the hood prevented the inner surface ever contacting the outer surface. This concept allowed the two walls along the zipped edges of the bag to seal against heat loss far more effectively than traditional construction methods."
All from here:
http://www.andymilnedesign.co.nz/wel...sleeping-bags/
Apparently, Fairy Down is what Sir Edmund Hillary used when he summited Everest.
All learned by powerful Googlefoo
Best I can tell, that bag was designed to be a 0* F bag.
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