Compressing a Down Bag

I think you can guess the answer(s). :-)

Down bags are shipped to the military vacuum packed. That's denser than you are likely to get, but the bags do take days to expand! The least dense you can manage the better.

And remember: the weight of a high-tension compression sack is significantly more than the weight of a low-density silnylon stuff sack. Weight is what matters most.

Far more important in fact is keeping your bag as dry as possible. Take this seriously.

Cheers

I like to use a lightweight dry bags such as these:

http://www.backcountry.com/store/STS0001/Sea-To-Summit-Ultra-Sil-Dry-Sack.html

I use a 13L (1.4oz) for my 15 and 30 deg bags. Might be able to get away with a smaller one. They are fully waterproof, relatively light, and you can get a decent amount of compression with these bags. For me, they've been a good compromise, particularly in good weather where I don't have a full pack liner, but want to keep my sleeping bad dry just in case.

Like Ian, I use a lightweight dry sack. I love it! It keeps my down bag dry and I can compress it as much as I like. Normally I compress it moderately. I use a 10L dry sack for my 30F bag and I typically compress it down to about 50-70% of my 10L (2.5 gal?) dry sack.

As a bonus, these sacks make awesome pillow cases because you can put whatever clothing you have laying around inside and then roll it up so it's the right firmness. If you only have one fleece, then you just roll it up more and you get a smaller but still adequately tall pillow.

"And remember: the weight of a high-tension compression sack is significantly more than the weight of a low-density silnylon stuff sack. Weight is what matters most.

I agree 100%, and that's why I have a Regulator stuff sack by Kifaru. It's a high-tension compression sack, but it weighs very little, since it's both high-compression and low-density silnylon.

Thanks for the posts, all. Keep 'em coming!

The Sea to Summit ultra sil bags are **NOT** waterproof, even when new, and they get worse. I keep meaning to post a review.

The seams leak, the fabric leaks. I've had this experience across two different sizes of the bags, and the bigger pack liner.

My test was to put a paperback at the bottom of the bag, before stuffing my sleeping bag in. Then just wait for it to rain hard for a few hours, or alternatively cross some deep water.

Or, for a quicker and less upsetting test, fill them up with water at the basin, and watch the water pour out the seams and bead on the surface.

They work fine as a regular stuffsack/backup inside a polythene bag though.

I have had no leaks with my Sea to Summit ultra sil bags. maybe it was a bad batch??? Or maybe they just sent the defective ones to Oz!

Unlikely to be a bad batch, I bought all three at different times and at two different stores. Similar experience to mine at http://jwbasecamp.com/Articles/DryGear/index.html#Update%205-22-06

But looking at the user reviews here there are claims that the waterproofness has improved with later models. Still, I'll never go back. They're expensive, I don't trust the circular taped seam at the bottom, and a polythene bag with a cuben bag inside has never failed me.

Oz? Are you thinking of Queensland? :) Actually I was living in Auckland when I bought/used them. After some poor navigating I spent half an hour swimming/crawling through a swamp out in the Waitakeres: leakage!

"Oz? Are you thinking of Queensland?"

Sorry, for some reason I keep getting you and Ashley Brown (in Sydney) confused. Must be the initials "A.B.". Anyway, I have filled my UltraSil bag with water and it didn't leak at all. So it appears to be hit and miss! Maybe take a bottle of water to the sports shop and 'try-before-you-buy'?

supposedly the older runs of the bags had problems, mine work just fine for keeping my down safe and dry in inclement conditions and here’s the review I did several months ago.

Ultra sil Dry bags.

I use the 8L Sea to summit ultra sil dry sacks. It fits my 20 degree Montbell S.S. bag, or it will hold all my insulation layers and my Golite Ultra20 quilt.

Hey, Paul-

Short answer, yes, you can compress a bag too much. Down is much more resilient than the synthetics though, overall. If compression didn't hurt the fibers, we would store them stuffed in their stuff sacks (or compression sacks) instead of fully lofted in a cotton laundry sack or hanging, right? I don't believe that we gain a lot by compressing a bag to its tiniest possible self. Maybe you gain an extra liter of space in your pack… so what? One thing I do that helps improve packing efficiency, and prolongs the life of my bags (by not over-compressing) is use dry sacks. As others have said, keeping the bag dry is of the utmost importance. But the other advantage of the dry sack is that you can use it as a sort of vacuum bag. Roll the top edge over, leave a corner open, and press down on the bag. (Or kneel on it, whatever.) You'll force the air out of the sleeping bag and dry sack; when you've sealed the sack, you're left with a malleable putty-like brick that you can shape however you need to pack. Cheers-

The newer S-to-S ultra sil dry bags do not leak. Older reviews (such as the one here on BPL and Jim Woods' excellent article on "Keeping Your Critical Gear Dry") did show that they leaked, both at the seams and through the fabric. I bought a small one last spring (2008) and tested it by turning it wrong side out and filling it with water. There was no leakage whatsoever. I therefore bought a couple more (one for my insulating clothing and one for my sleeping bag) and tested those the same way. Not a drop of water came through. They also were field tested when I slipped and fell while fording a stream. Even though the bottom of my pack contained a couple inches of water, there was no leakage into the sleeping bag (also in the bottom).

It appears that Sea-to-Summit must have done considerable work on their product after the initial bad reviews. It is great to know that at least some companies do pay attention to such things! That being said, I wouldn't trust my sleeping bag or insulating clothing to any bag without first testing it!