Resurrecting this old thread for a slightly different request of the wise ones.
I've ordered the PHD Combi bag which is a wide version of the Minim 400.
I liked the recommendation before, which was the Pod Airstream Lite Drysack small 7L was a good size for a Minim 300. Would it be fair to think the medium 10L would be a good size for the Combi? I didn't need to squish particularly hard to get the Minim 300 into 7L so would it be good idea to get another 7L for the Combi or go up to 10L because 7L will simply be too difficult? Or, given the Combi is so much larger, would be better to give up on the idea of using other gear to squish the air out via the eVent base and go to a compression sack instead?
FYI this review states if you have opportunity to be walking in warm weather, the eVent fabric does let the down bag dry out. I did ask if that were possible and the general view was it not work due to so much dampness coiled into the bag and so little eVent, but the review suggests its possible. Useful feature?
I use a 13l Sea to Summit eVent compression bag for my Combi simply because I already had it, and find this works well. The Combi goes in pretty easily and can be compressed down a lot, although I don't usually bother with this, simply letting the weight of my gear squish it in the bottom of my pack. I guess it would go in a 10l bag easily enough.
As for letting a damp bag dry out, I've never noticed this happen. I guess in the bottom of a pack there is little chance for moisture to escape even if it does get through the eVent.
Thanks Guy. That's one reason to put it in a just-large-enough eVent bag near the top to capture any sunshine and let it breathe. I've only camped 4 consecutive nights in my last down bag and no damp issues but I've seen the concern from others in this forum. The bigger the drybag the more the down can loft and so I guess "breathe" better. 13L though, seems quite large, but you have the compression version so you can make whatever level of loft you want. I have a 20L S2S event for non-bag clothing, it makes a decent sausage width-wise bottom the pack, used it last week and pleased with it so far. The S2S are thicker material, tougher feeling than the Podsac type which is noticeably thinner material.
Does anyone have both Sea2Summit and Podsac Airstream at hand of similar size to compare how large is the eVent? The larger the eVent section the better for drying?
I'll email both manufacturers asking for the eVent sectoin size, its one argument to go for a larger bag because it can loft up larger on top of backpack, a bigger eVent base (hopefully). I see Podsacs do a slightlier heavier non-Lite version which is a smidging heavier but black which would be perfect.
My backpack is Golite Jam, plenty of opportunity to have drybag in the top breathing in any sunshine.
Got this from Sea2Summit enquiring about a sleeping bag drying out when in sunshine inside their drybag
"an eVac Dry Sack will not allow dampness to 'breathe out' through the eVent fabric. If you put a damp item in an eVac Dry Sack (or eVent Compression Dry Sack), it will remain damp.
To explain - 'breathable' fabrics only allow moisture vapor to pass through them if there is a temperature gradient (ie if the inside of the enclosed space is warmer than the outside). If you wear a jacket made of eVent fabric, your body warmth will drive the moisture vapor through the membrane. A damp sleeping bag does not generate any warmth, so its dampness will not be driven through a 'breathable' membrane. Not at all.
I think this would be easier for consumers to understand if fabrics were not referred to as 'breathable', but as 'moisture-vapor permeable'.
The function of the event panel is to allow air to be forced out from inside the dry sack; this works (extremely well) because the eVent fabric is also gas permeable (ie it will prevent water passing through it, but allows air to pass through). "
Right I knew that but my question back was that if the bag is in sunshine it will encourage water inside to evaporate and leave the bag, whilst not letting water in.
Why not carry your sleeping bag outside the pack in a mesh sack while the sun shines? Will surely be much more effective than putting it in what's basically a plastic bag with a relatively small area of "moisture-vapor permeable" fabric. Just remember to get it in something waterproof as soon as the first black cloud appears.
Guy, well yes obviously I will try to keep damp and obviously if it gets damps take all opportunities to dry first thing, through the day and before sleep. The most drying time being at any peak of daytime temps and in any sun, and obviously if its being aired I'd have to keep an eye on rain. That's all old-tech obvious stuff. I was just wondering if I could rely on a little dampness getting out via the eVent fabric. There are contradictory advice out there.
Podsacs the non-lite type are black, but I think in the 10L type size for a Combi bag the amount of eVent fabric in Seatosummit looks a bit bigger than in the Podsacs.
Got additional from Seatosummit, who have replied to me twice, vs no reply from Podsacs
"the key to 'breathability' is a temperature differential (or temperature gradient) between the inside and the outside of the enclosed space.In other words, it has to be warmer on the inside than on the outside.
If an eVac sack is placed in the sun, it will warm up. But the outside of the sack will be the same temperature as the inside; so moisture vapor will not make its way out through the eVent membrane.
(if it is sunny, and you wanted to dry a sleeping bag, you could transport it on the top of a backpack in a mesh sack - this would allow some airflow which would help to dry the sleeping bag)"
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