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TIP: The online Bushwalk Inventory System can help bushwalkers with a variety of bushwalk planning tasks, including: Manage which items they take bushwalking so that they do not forget anything they might need, plan meals for their walks, and automatically compile food/fuel shopping lists (lists of consumables) required to make and cook the meals for each walk. It is particularly useful for planning for groups who share food or other items, but is also useful for individual walkers.Bivy sack
Fri 25 Nov, 2016 6:55 pm
I am after a bag that you'd use in cold weather or rainy conditions to protect a duvet sleeping bag.
It has to be breathable and a gore-tex like alternative but just as good in order to reduce the cost.
The condensation factor of bivy sacks is going to be the main issue so if gore-tex is the only real alternative, I'd be
willing to spend the extra money.
What would you recommend me?
Cheers!
It has to be breathable and a gore-tex like alternative but just as good in order to reduce the cost.
The condensation factor of bivy sacks is going to be the main issue so if gore-tex is the only real alternative, I'd be
willing to spend the extra money.
What would you recommend me?
Cheers!
Re: Bivy sack
Fri 25 Nov, 2016 7:00 pm
I'd recommend a tent.
A bivy is really only for emergency use, or for short term use in cold but otherwise dry conditions were weight saving is absolutely critical (e.g. high alpine ascents).
In a sort-of-cold or rainy condition for any length of time any WPB fabric bivy is still going to restrict evaporation to the degree you are going to end up pretty wet inside.
A bivy is really only for emergency use, or for short term use in cold but otherwise dry conditions were weight saving is absolutely critical (e.g. high alpine ascents).
In a sort-of-cold or rainy condition for any length of time any WPB fabric bivy is still going to restrict evaporation to the degree you are going to end up pretty wet inside.
Re: Bivy sack
Fri 25 Nov, 2016 7:44 pm
If your sleeping bag insulates you well, the outside of it will be at air temperature, which means that there's not enough temperature differential on the outside of the bag to "drive" any moisture from you through the bivy bag, so the outside of your your sleeping bag will get damp. This is why goretex sleeping bag outers don't work, and why the inside of goretex bivy bags get damp.
If the outside of your sleeping bag is warm ( meaning that your sleeping bag is not insulating you properly) then there might be enough temperature differential to push the vapor through the outer layer.
The balance point is where you are at perfect temperature, and don't produce any sweat/vapor, which means that there is no vapor to go through any outer bag , in which case the outer bag could be waterproof nylon, as could the inner lining - the latter being a vapour barrier.
I suppose the ideal bivy sack might just be a lightweight nylon with a decent DWR finish, which is really the ideal sleeping bag outer fabric.
A
If the outside of your sleeping bag is warm ( meaning that your sleeping bag is not insulating you properly) then there might be enough temperature differential to push the vapor through the outer layer.
The balance point is where you are at perfect temperature, and don't produce any sweat/vapor, which means that there is no vapor to go through any outer bag , in which case the outer bag could be waterproof nylon, as could the inner lining - the latter being a vapour barrier.
I suppose the ideal bivy sack might just be a lightweight nylon with a decent DWR finish, which is really the ideal sleeping bag outer fabric.
A
Re: Bivy sack
Fri 25 Nov, 2016 8:53 pm
Tyvek works reasonably well
Evan at TerraRosa
Evan at TerraRosa
Re: Bivy sack
Sat 26 Nov, 2016 8:44 pm
Mountain Laurel Designs SuperLight Bivy made from 10D 3x nylon - very breathable but only splash proof - you'll need a tarp with it.
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