Synthetic Quilts and Sleeping Bags

My biggest issue with synthetics is that the insulation begins to degrade immediately. Gradually, but yet immediately providing a relatively short shelf life even if the product isn't used regularly.

david …

if you dont stuff it, it shouldnt degrade if it just sits on a shelf … the trick is to stuff it lightly in yr pack and not use stuff sacks … and hand wash it …

keep in mind that for weekend warrior use, modern synthetics should have a life of a few years anyways … i suspect many BPLers will be changing even their down quilts/bags out within that time frame for the latest shiniest lightest version regardless …

of course, synthetics are cheap enough that you can often buy 2+ bags for the price of a down bag …

if you look at synth bags and the equivalent en-rated down bags, synthetics are roughly 30-40% heavier …

the biggest problem with synth aint the weight IMO … its the bulk …

In my opinion, Synthetic bags are better for warmer weather (40+ degree's) when 90% of people use a sleeping bag/quilt. At these temps, the required fill material is very similar between synthetic and down so there isn't much difference in weight and bulk. My point of this whole discussion, is there are very few companies that even make such a bag and when they do they use heavy shell materials and alot of times seem to add way to much fill or some second rate fill.. With that said, I still think Down is a great fill material, and really shines in cold dry weather.

Since there isn't much difference in fill weight for summer bags, I always thought it would be a good idea to have a synthetic "Under bag/liner bag" that worked to about 50 degree's and could be used all summer long and then a Down "Over bag" that you used in the winter. The down overbag could come in several different temp ratings. Lets say 20 degree's, 0 degree's, -20 degree's and -40 degree's.

Not sure if there would be much demand for the modular type bag but I would like to try the concept.

I agree, I prefer synthetics for warmer temps where small amounts of down can be harder to control. Synth covers better with no cold spots and much simpler construction. I like my 40* revelation but even that is too hot sometimes. My APEX 2.5 is my goto for those times.

I think a modular system would be the bee's knees. It makes total sense and I'm not sure why it hasn't been done before. It's bulkier, but a lot more flexible.

Lawson I agree that synthetic is great for warmer weather. My old BPL 60 quilt is great for warm weather hiking in VA. My brother had a down bag with a similar amount of loft and he seemed to get cold spots so I think you're right about that. Its also small enough I can pack it loosely without it being huge.

I don't know how a down bag would work over a synthetic quilt would work. Condensation is going to be in the cooler, outside part of the quilt. If thats where the down is its more of a problem. So maybe the synthetic would be better on the outside?
On the other hand having the down on the outside allows it to loft better. Also people have used purely down bags for cold weather so I don't think having synthetic under that makes it any worse.

One principal is that the temperature will gradually decrease from body temperature next to your skin to the outside temperature on the outside of your insulation.

There is a place where the temperature gets down to freezing.

Water vapor from your body will go out through your insulation to the point where it reaches freezing and will freeze there and quit flowing out.

If you have down on the outside, water will freeze in it and down doesn't tolerate being wet so good.

If you have synthetic on the outside, water will freeze in it but it's not as bad as down.

I think this is only a factor in very cold temperatures and if you spend several days.

I'm another one who would love to see a synthetic bag that uses light-weight shell materials (maybe a hoodless bag/quilt like Zpacks makes). I have a 2.5 oz climashield quilt that I bought from some one that has silk on the inside and it's great! It's a little on the narrow side but it only weighs 9.5 oz.

But what about a lightweight synthetic jacket? I see a lot of jackets and vests that use 1.5-2.5 oz of down fill with really lightweight shells that weigh around 4-7 oz. Surely a climashield or primaloft jacket/vest could provide the same warmth at almost the same weight? The closest thing I can think of is the Patagonia Nano Puff.

@lawsone – i use a similar system but as people suggested with the synth outside (for all the suggested reasons)
I use a MLD 2.5 XP quilt and overlay it over a 30F bag to go down to approx 15F or so. works pretty well since the MLD has real variable girth not only in torso but also in footbox so easy to adjust. Havent tried to with my 10F bag yet…

Why do you say there is a gap?? i think the big names (TNF etc) dont make it cause there really isnt a market for it that much (IMO most people buying 50F synth sleeping bags look for cheap rect stuff for casual car camping

IMO what MLD, Tim, Arrowhead and others make should fill the need of this specialized niche

you might be interested to take a look at Andy Kirkpatrick's view on this system. he isnt UL but on the other hand has given this system a "rough" ride and likes it

http://www.andy-kirkpatrick.com/articles/view/double_up

M

Could you use a synthetic bag and overlay with a down quilt? Would this have the same effect as a 'vapor barrier' of sorts? The synthetic would absorb the moisture and the down would remain dry….or is it better the other way around? Thanks,

@John. Montane Fireball and OMM Rotor? RAB Xenon has slightly heavier fill, and adds a hood.

david … no … the moisture migrates outwards to the last layer … so in that case to the down … generally you want the synth as the last layer, it also protects the down against any spills/weather/drips

as to the synthetic jackets, i think mainstream manufacturers have that pretty well covered … nanopoofays/xenons/atom lts/ etc …

a very viable option which i use all the time is putting something like an EXL under an atom lt (or my EB downlight vest under my 19$ old navy puffy) … the result is about the same weight as a micropuff, but warmer, and more flexible … and the down is protected against outside weather/condensation

While I understand the concern with the two bag system using a synthetic inner and down outer, the issue could easily be solved with a waterproof shell on the synthetic inner bag. The whole point of the modular system is to create a sleeping bag that could be used in any weather situation. I think it would be extremely useful for extended expeditions/trips where your traveling through a range of weather conditions.

I think I am going to make myself a modular sleep system to see how it works.

If you put a waterproof shell outside the synthetic/inside the down, the inside surface of the waterproof layer will become saturated with droplets of condensed water

Jerry is right on. If you are going to put a waterproof outer on it put an WP inner on too and make it a VB quilt like my epiphany APEX (or just buy the epiphany APEX) otherwise with a breathable inner and WP outer you will get trapped vapor and yes synthetics can manage this better but it will build up over time and wet out the inner layer then the sleeper unless you dry it often. A WPB outer is worth a try but there can be a build up of moisture there too as the B in most WPB is still not that B if you ask me(oh look i rhymed).

-Tim

@lawsone

what everyone said…but why are you adamant on having the synth inside? if its due to compression and all that IMO that is easily solved buy correct sizing of outer (and maybe using quilt with variable girth) and we also know from richard N's stuff that some compression on the down is a non issue. wet down from frozen condensation is less happy

I think it can work. WP outer, breather inner. But you need to wear a VB clothing inside.

Disclaimer: I am actually planning to sell this system. See my post in Gear Deals for the quilts. VB clothing coming soon.

If you have to wear vb inside just scrap the breathable liner for lighter cuben. If you must wear vb the breathability of the liner has no purpose, it is just inviting people to use it wrong and then will leave them cold and wet, but you're the expert.

-Tim

I am not interested in using cuben. I think SevenD and SevenDs is much nicer for quilts and clothing. The purpose of the breathable side is to allow the quilt to loft without a pump. The colors for both sides are different therefore you can't use it wrong.

I am not going to argue past this post but a breathable liner and waterproof shell is not a good idea. If you want to use those fabrics and make a vb quilt use the 7ds inside and the 7d outside. If you must use vb clothes anyway the feel of the fabric doesn't matter you already have cuben, sil or plastic on.

I want it to be heard that I strongly recommend against breathable liner with waterproof shell.

-Tim

I hear you. The quilts I am making have 7Ds inner and 7D outer. But they can be used the "other" way also when combined with VB clothing. Sorry if this caused any confusion. Even with VB clothing you don't need to use "other" ways as the DWR on 7d is pretty good.

When I said shell, I meant both the inner and outer but I should of said shell and liner since it looks like my post confused some of you guys.. With that said, it seems as if a few of you guys are arguing for something that currently doesn't exist. Every down bag I have ever owned or have ever seen has had a breathable inner material which means this moisture you guys are worried about condensing and freezing on the inside of the outer shell is already happening and would be no different if you added a synthetic inner bag to the mix. Its the reason alot of people use vapor barrier liners.. So using a synthetic bag with just a standard DWR material (inner and outer) would be no difference.. The moisture would still get into the down and condense on the inside of the outside shell material. BUT, the synthetic inner bag would be dry, so essentially the system would be warmer then a single bag, because a higher percent of your insulation material is working at peak performance.

Now the idea about using a waterproof shell(inner and outer) on the synthetic inner bag to eliminate all moisture is exactly what TIM does. This would keep your down dry and would essentially make the inner bag an insulated vapor barrier. But as Tim suggested, it either has to be all or nothing proposition since a waterproof shell and a breathable liner on the synthetic inner bag would cause your moisture to get trapped in the synthetic fill with really no way to leave but through the inside… BUT, an inner bag that doesn't breath is only really effective for a winter system since it would be a sweatlodge in the summer.. And since the idea behind the modular bag system is to have a synthetic summer inner bag and not a insulated vapor barrier, I would use DWR materials on the inner and outer shell on the synthetic summer bag..

Now why am I dead set on a Synthetic inner and Down outer? Simple.. Synthetic bags are better for warmer weather (40+ degree's) when 90% of people use a sleeping bag/quilt. At these temps, the required fill material is very similar between synthetic and down so there isn't much difference in weight and bulk. Those people that use a bag in the winter, could buy the down outer bag with less down (expensive part) and use it with their synthetic summer bag to make a very versatile two bag system. Now as far as a down summer/inner bag and a synthetic outer/winter bag goes, this makes no sense at all since the system would be MUCH heavier and bulkier.. You might as well use a 100% synthetic winter bag.. If moisture is a concern, wear a vapor barrier and be done with it.

When I think about it, this idea is really patent-able. Hmm maybe I should license the idea to someone like Tim so he can make us both Billionaires : )

Hmm.

Why do you email me and I'll see if I can wrap my little brain around what you're saying.

-Tim

Seems like 45* prodigy with epiphany over it. Is this what you're saying.

@lawson

it seems like everyone has different needs and opinions – and i am by no means a guru of anything but i didint get your last:

The whole point about condensation in the down is that indeed IT IS HAPPENING RIGHT NOW with your existing 3/4 season down bag. BUT most people (me included) have 3 kinds of trips:
summer – no issue here
few days long 3 season – where there might be condensation but many times you could dry out during the day since temps will be above freezing during daytime
short winter trips
I think in these circumstances the down-freeze-water issue is pretty moot.

however if for some reason you hike in prolonged below freezing and/or very wet (say scotland just about any time of year) the humidity could slowly compromise your down. For this reason its advisable to have the synth outside (if you take the time to read Andy Kirkpatrick's account i posted earlier its interesting to see how delicate sleep systems are when pushed to the limit.

I have an MLD 2.5 quilt that is fine for summer use and since its wide enough and has variable girth can be used as an overbag
I have a 30F down bag for most 3 season use but i can layer them to go down to about 15F which extends my range and protects my down bag.

if sized correctly i assume my quilt could fit around a proper 3 season bag to extend it to light winter use …

YMMV