I have a Montbell Super Spiral Down Hugger #3 which will take me comfortably just below freezing (-1C) but on my/our Everest Base Camp hikes it was likely to get down to maybe -14C ( or worse eg at Gorek Shep) so I needed a little more warmth.
In this post I will be adding approximately 3 ounces of 900 fill power down to the bag. I also have a Montbell Superior Down vest, coat and trousers which I can wear (plus a down balaclava and down socks!) so I would be cosy enough.
See also:
Spot would like to come too, as you can see – but those strange Nepali dogs might have made mince-meat of him.
If you turn the bag inside out you can see the stitching where baffles have been closed. It is a relatively easy task to push all the existing down to the bottoms of the baffle tubes, carefully ‘rip’ the stitching which closes the baffles, then push handfuls of extra down into the tubes until you are satisfied they are full enough, then sew them up again.
You can buy 3 ounces (90 grams) of 900 fill power down for US$39.95 here: from Ripstopbytheroll US$38 for 3 oz of 850 filll power dry down, or 800 fill power dry down here: from Tier Gear in Tasmania for A$30.80.
3 ounces of down should drop the (comfort) temperature rating of your bag by approx 7C degrees and add less than 85 grams weight – well worth the $40 and a couple of hours fiddling!
Cheap Down Insulation at Aliexpress 850 fp US$10 = 50 grams (Jan 2021) here is the Main Page. Best Option: 850 fp: I lb = US$69 (Jan 2021).
US$160/pound here Feb 2024.
All about down here: https://www.down-tek.com/
Amazon 900 Fill Power Down US 59 per pound (450 grams) plus $8 shipping.
NB: The Aliexpress and Amazon down may well not be the fill power quoted.
BTW: These are the lightest downproof fabrics: 0.66 oz Membrane 10 taffeta nylon at $7.95/yd and 0.56 oz MEMBRANE 7 Ripstop Nylon at US 18.96/yd (Jan 2021), .49 oz/yd 2 Argon 49 U$12.50/yd (jan 20221)
On the inside of the bag you will find the seam where all the tubes have been sewn closed. You have to unpick a section at a time of stitching adjacent to the tube you want to fill.
Like this. A stitch unpicker is a good idea. So is a wife with superior manual dexterity.
This has exposed one side of the tube. You will have to unpick the stitching on the baffle material to expose the other side of the tube. You need to make opening large enough to fit your closed fist (full of down)
Opening up the tube.
Here it is all sewn up again. Two lots of restitching are necessary, one to close the baffle, the next to close the tube again.
Hope this is clear enough. Some additional useful instructions here: http://www.doityourself.com/stry/how-to-replace-feathers-in-a-down-sleeping-bag See videos here: https://www.youtube.com/watch?v=ZRMJUZFTnHM & here: https://www.youtube.com/watch?v=sCJp2C4EFjU
PS: If you want to make a down sleeping bag yourself from scratch Ripstopbytheroll have down-proof material that starts from .56 oz/yd2. With this and some 850fp down you should easily make yourself a bag for around $100 which weighs less than a pound.
First Published on: Mar 11, 2017
When you add handfulls of down, how do you end up with the appropriate amount for each baffle? It would be disappointing to end up with not enough or lots of extra. Would it be beneficial to measure baffle dimensions, approximate volume and distribute extra fill proportionally (weigh it)?
Hi Michael, You could do that if you want or you can just shove it in and see when the baffles appear to be full – after all the down expands to fill the space. I admit that when we did this we put more in than we needed to (and maybe even added an additional 50 grams of unnecessary weight to the sleeping bag!) but it is toasty warm now and didn’t cost an arm and a leg, so all good. Cheers, Steve & Della.
Just to alert anyone thinking of doing this…
This procedure is known as overfill. It doesn’t add more loft, but packs the down into the existing baffle more tightly.
Good manufacturers will overfill their baffles anyway by 20-30%, to reduce down movement and keep the bag working better as it ages and the loft begins to degrade.
Adding additional overfill will give a little extra warmth, but is much less efficient than using the extra down in larger baffles optimised for that volume.
Well, I guess my bag must be from a ‘bad’ manufacturer. Also I am not a fool! I could see gaps between the down when I held it up to the light. There was plenty of room for extra down and I was able to very cheaply convert a 0C bag into a -20C bag. Worked well for me on my(EBC) trek. I would do it again even though it is a little bit fiddly. I will probably add about 100 grams to another bag I have to convert it from 0C to approx -7C. I can buy the down from about $10 an ounce so this procedure will cost $30 – a fraction of what a new bag would cost. PS: Beware of becoming a troll, Geoff.
Where do you buy your down?
Fourth paragraph. But many other sources. Cheaper on Aliexpress. Cheers, Steve. Cheap Down Insulation 850 fp US$10 = 50 grams (Jan 2021) here is the Main Page. Best Option: 850 fp: I lb = US$69 (Jan 2021).