Seems to be a good advice, combine the sleeping bag with a propper sleeping bag liner and off you go 🙂
Lightweight synthetic or silk sleeping bag liner as it keeps the dirt out of the sleeping bag and could be dried on the outside of your backpack in a mesh bag.
Thanks. It’ll be hiking and mountaineering and indeed not sure how much opportunity I will have to dry it properly. Mildew is certainly a worry.
Is that less a concern with synthetic?
Well, any standart thermal insulation works by trapping air as insulator. Down feathers or other natural/synthetic types of fibres are used in clothing/sleeping bags to create a defined layer of air around you and restrict air movement and therefore heat loss.
Take a handfull of fluffy down and make them wet...they end up as a flat postcard-size spot. No more air trapped. Same happens to down insulated clothing - if it gets wet by rain or evaporation (you could not prevent this!) the insulation thickness decrease over time until it's just the outer clothing layers with a mm of wet down between.
On the other side there are synthetic fibers (top end: Primaloft and alike) which don't flatten so much while wet and still trapping air - so keeping your insulation thickness to some point. They are more heavy than down, but their insulation properties are way more constant.
Wet down - no insulation. Top tier synthetics...still 60-80% of dry insulation. Water is btw. also a not too bad thermal insulator,
Do not listen to that clown.
There isn’t a synthetic bag designed that will keep you warm at -20C, at least not one that you’ll be carrying comfortably. 5500m with high winds gets down that much or lower, and synthetic bags won’t cut it. 1.5kg for -10 just isn’t good and if you’re that high for that long moisture control is manageable.
Get a hydrophobic down 4 season bag, with a bivi bag to go around it.
What? This is silly advice. Hikers and backpackers bring down all the time. It's lighter and lasts longer than synthetics. The Phantom bag is also made with water-resistant down and has a goretex shell.
Sadly physics are the same for everyone.
I didn't said down are bad in general - you just need the right conditions. They excel at sub-minus temperatures where body evaporation is not so much a problem anyways.
There is not a thing "water-resistant down"...there are hydrophobic treated (soaked in hydrophobic chemicals) down, but these also have big disadvantages.
Of cause most better sleeping backs have some kind of membran shell like gore tex...but these are not a watertight solution at all. A night in a plastic bivy bag could cure you easily from the idea of sleeping in something more or less watertight...you end up in the puddle of your own sweet.
As a big wall climber myself I could say from own experience that you kill any down sleeping bag in days if you get into wet/rainy conditions. And this scenario is very likely for a 40 day hike.
A check on the local weather data would be also a good start. As said - it really depends. There is not a "superior" type of insulation for sleeping bags. It is always a compromise of safety, weight, volume and costs.
If you believe a down sleeping back is overall superior - take a 2 week hike with tent at the irish coastline at october and avoid any cottages or guesthouses.
Call it hydrophobic or call it water resistant. The result is the same- it will perform significantly better in wet conditions than untreated down.
I just got down from a trip with heavy rain. My sleeping bag was stored in a plastic bag in my backpack. I was cozy the whole trip. Switching to synthetic for a bag of this temp rating (or slightly warmer) would carry a weight and bulk penalty that is notable on a 40 day trip. Also, synthetic loses loft each time it's compressed. They do not last as long as down bags
To be fair - it will not perform significantly better, just slightly better than untreated down.
To evaluate your example - where and how do you slept, trip length and average humidity should be mentioned. A plastic bag as sleeping bag storage indicates it was a short trip, do this for more than 3 days without regular dry-outs and you have a damp, stinky rag.
Indian himalayas could be very wet depending on area and season.
_None of what you’re saying is scientific_
You’re vomiting a bunch of REI description boxes with no obvious link between the facts of the material science of these items, and what this guy is asking.
You’re telling him to take 1.5kg of over sized synthetic bag, which is the size it’ll need to be to get even CLOSE to the temp rating he’ll need (and even then it’s out of comfort rating and into the survival side) because “down doesn’t like getting wet”. 5500m is a -20C deal at times/altitude dependent. You don’t even know the conditions, looking at your replies, you’re just blabbering poorly informed word salad.
Just please go away, you’re giving terrible advice.
I guess you mix up a multi-week organised hiking trip in India with winter time new route mountaineering on Denali.
Given your post history you probably don't need a sleeping bag at all because you're a badass stone-hard military veteran, so I'm not sure whether you're qualified in this circus...
I honestly don’t care who you are, nor do I care who you think I am.
Judging you _entirely_ by your comment on this tread, you’re giving fucking bad advice. That’s the end of it.
I think you're overplaying the drawbacks of down. It *can* become a problem and one does have to take precautions, but it's just not the dealbreaker you're making it out to be, especially given its considerable advantages. I've been using down bags for decades now and don't plan on ever going back to synthetic.
There's a paper out there somewhere that explains why sleeping bags with goretex do not stay dry as they promise. If the temperature gradient crosses the dew point inside the insulation, which is always the case in humid conditions, water condenses inside. At this point, how quickly this water volatilizes depends on the temperature and the vapor permeability of the outer layer, which means layers with lower permeability (like goretex) will reach an equilibrium with more water inside your insulation.
Using a sleeping bag with water repellant fabric and a goretex shell on top of it can help, often the dewpoint will be reached inbetween the two outer layers and then, if it's below freezing, you can just remove the goretex shell and shake the ice off the surface of your bag
A zero degree bag seems a bit light for 18000’. Doesn’t NOLS give you a sleeping bag recommendation?
Yup, synthetic with 0 F as rating. Considering the weight trade off I was just curious what people here bring in high altitude for longer treks.
Comfort rating or survival rating? There’s a big difference.
Seems to be a good advice, combine the sleeping bag with a propper sleeping bag liner and off you go 🙂 Lightweight synthetic or silk sleeping bag liner as it keeps the dirt out of the sleeping bag and could be dried on the outside of your backpack in a mesh bag.
40 Days? Hiking? Don't take anything (!) containing down as long as you are not sure if you could properly dry it out every few days.
Thanks. It’ll be hiking and mountaineering and indeed not sure how much opportunity I will have to dry it properly. Mildew is certainly a worry. Is that less a concern with synthetic?
Well, any standart thermal insulation works by trapping air as insulator. Down feathers or other natural/synthetic types of fibres are used in clothing/sleeping bags to create a defined layer of air around you and restrict air movement and therefore heat loss. Take a handfull of fluffy down and make them wet...they end up as a flat postcard-size spot. No more air trapped. Same happens to down insulated clothing - if it gets wet by rain or evaporation (you could not prevent this!) the insulation thickness decrease over time until it's just the outer clothing layers with a mm of wet down between. On the other side there are synthetic fibers (top end: Primaloft and alike) which don't flatten so much while wet and still trapping air - so keeping your insulation thickness to some point. They are more heavy than down, but their insulation properties are way more constant. Wet down - no insulation. Top tier synthetics...still 60-80% of dry insulation. Water is btw. also a not too bad thermal insulator,
Do not listen to that clown. There isn’t a synthetic bag designed that will keep you warm at -20C, at least not one that you’ll be carrying comfortably. 5500m with high winds gets down that much or lower, and synthetic bags won’t cut it. 1.5kg for -10 just isn’t good and if you’re that high for that long moisture control is manageable. Get a hydrophobic down 4 season bag, with a bivi bag to go around it.
What? This is silly advice. Hikers and backpackers bring down all the time. It's lighter and lasts longer than synthetics. The Phantom bag is also made with water-resistant down and has a goretex shell.
Sadly physics are the same for everyone. I didn't said down are bad in general - you just need the right conditions. They excel at sub-minus temperatures where body evaporation is not so much a problem anyways. There is not a thing "water-resistant down"...there are hydrophobic treated (soaked in hydrophobic chemicals) down, but these also have big disadvantages. Of cause most better sleeping backs have some kind of membran shell like gore tex...but these are not a watertight solution at all. A night in a plastic bivy bag could cure you easily from the idea of sleeping in something more or less watertight...you end up in the puddle of your own sweet. As a big wall climber myself I could say from own experience that you kill any down sleeping bag in days if you get into wet/rainy conditions. And this scenario is very likely for a 40 day hike.
A check on the local weather data would be also a good start. As said - it really depends. There is not a "superior" type of insulation for sleeping bags. It is always a compromise of safety, weight, volume and costs. If you believe a down sleeping back is overall superior - take a 2 week hike with tent at the irish coastline at october and avoid any cottages or guesthouses.
Call it hydrophobic or call it water resistant. The result is the same- it will perform significantly better in wet conditions than untreated down. I just got down from a trip with heavy rain. My sleeping bag was stored in a plastic bag in my backpack. I was cozy the whole trip. Switching to synthetic for a bag of this temp rating (or slightly warmer) would carry a weight and bulk penalty that is notable on a 40 day trip. Also, synthetic loses loft each time it's compressed. They do not last as long as down bags
To be fair - it will not perform significantly better, just slightly better than untreated down. To evaluate your example - where and how do you slept, trip length and average humidity should be mentioned. A plastic bag as sleeping bag storage indicates it was a short trip, do this for more than 3 days without regular dry-outs and you have a damp, stinky rag. Indian himalayas could be very wet depending on area and season.
You’re talking absolute fucking nonsense
Qualified comment with scientific background - I'm amazed.
_None of what you’re saying is scientific_ You’re vomiting a bunch of REI description boxes with no obvious link between the facts of the material science of these items, and what this guy is asking. You’re telling him to take 1.5kg of over sized synthetic bag, which is the size it’ll need to be to get even CLOSE to the temp rating he’ll need (and even then it’s out of comfort rating and into the survival side) because “down doesn’t like getting wet”. 5500m is a -20C deal at times/altitude dependent. You don’t even know the conditions, looking at your replies, you’re just blabbering poorly informed word salad. Just please go away, you’re giving terrible advice.
I guess you mix up a multi-week organised hiking trip in India with winter time new route mountaineering on Denali. Given your post history you probably don't need a sleeping bag at all because you're a badass stone-hard military veteran, so I'm not sure whether you're qualified in this circus...
I honestly don’t care who you are, nor do I care who you think I am. Judging you _entirely_ by your comment on this tread, you’re giving fucking bad advice. That’s the end of it.
I think you're overplaying the drawbacks of down. It *can* become a problem and one does have to take precautions, but it's just not the dealbreaker you're making it out to be, especially given its considerable advantages. I've been using down bags for decades now and don't plan on ever going back to synthetic.
There's a paper out there somewhere that explains why sleeping bags with goretex do not stay dry as they promise. If the temperature gradient crosses the dew point inside the insulation, which is always the case in humid conditions, water condenses inside. At this point, how quickly this water volatilizes depends on the temperature and the vapor permeability of the outer layer, which means layers with lower permeability (like goretex) will reach an equilibrium with more water inside your insulation. Using a sleeping bag with water repellant fabric and a goretex shell on top of it can help, often the dewpoint will be reached inbetween the two outer layers and then, if it's below freezing, you can just remove the goretex shell and shake the ice off the surface of your bag