Synthetic bags, what works, what doesn't, discuss.

[sailfish]

Hi,

After the “maximising your sleeping bag warmth” thread aimed at down bags, I thought I’d start a thread on synthetic bags. I know that down bags are by far the most popular for hiking due to their vastly superior warmth for weight. However I am interested in opinions based on real world experience with synthetic bags, not theory.

Synthetic bags just seem to be, cheaper, easier care and generally less hassle in keeping them working well in damp environments etc. Being into fishing means I camping near streams in cold, damp and often foggy conditions so I have an interest in synthetic bags. The main problem though is the weight. To that end I have a light synthetic bag of about 1 kg, Palm Visa optimistically rated at 0 C and have various means of extending its range. I know it is not a good bag, it has almost no loft but having used it a while, I think it’s true rating is possibly about +5 C with polypropylenes.
I use an 8 C reactor liner for comfort to about 0 C and a Thermolite blanket (wobby) at -8 C. The wobby can be used for other things, adding a zip slit near the middle it can be a warm poncho or even a double layer tabard and replace the very warm clothing used around camp. As a tabard, I can still carry a pack but it seems most unlikely such activity would require that much warmth. All this leaves me with sleeping options that are comfortable in anything down to -8 C and possibly a little below that and not be restricted to a winter bag or nothing and not have to sleep in bulky clothing, just polyprops.
Weight wise it isn’t too bad because the wobby replaces some clothing. So a 1 kg bag and a liner get me to about -8 or -10 which is just enough for what I do.

I have been experimenting with an AMC bivvy which is a very light heat reflecting bag lined with thermolite. The questions are:
1. Can this be used for emergency day walk equipment?
2. Can it be incorporated into an overnight sleeping system to make it even lighter in total?
Probably yes to 1 thought not necessarily very comfortable.
For 2, I have not found a way to overcome the condensation issues associated with this. I have slept in this covered by the wobby to 0 C but it gets pretty wet inside. Surprisingly not much thermal loss as there is no evaporation but darn uncomfortable all the same. A trick to reducing this damp seems to be to minimise time in the bivvy, only using it for the very coldest few hours of the night. Wearing clothing in it can mean starting the next day in damp clothing. So far not an altogether successful experiment.

On to bags though.
The One Planet Sack 1 is just under 1 Kg and has an EU comfort rating +4 C. Weigh for weight, this can be compared directly to my Palm bag. The Sack 1 has way more loft so one would assume it should be a much warmer bag yet it seems to me the Palm rates about +5 C. Perhaps the EU system does not account for any sleepwear like polyprops. Of course the Palm series is very old, I know they were around in the 70s so predate that. It would be surprising if synthetic technology had not advanced considerably since then. So I wonder what value the EU system would attribute to the Palms. I wonder if the EU ratings might be a little conservative, what do others think? Anyway I would be interested in other opinions, perceptions from experience on ratings, synthetic bags, what’s good, what’s bad etc. I am not interested in down only users theoretical opinions that we already all know, so let’s try to keep it real and constructive.


Regards,
Ken

[sthughes]

Hi,
I wonder if the EU ratings might be a little conservative, what do others think?

It all depends on the individual and the variables (what sort of tent, breeze, have you eaten recently, what sort of sleeping mat etc. etc.). EU is really only useful to compare new EU rated bags with each other, not to compare to old bags that are not rated by the same method.
The actual degree rating is really only for simple comparison, but for me personally in my 'usual' circumstances it is pretty accurate. Others will find quite differently.

[Son of a Beach]

The EU standard is certainly more conservative that any marketing figures derived without it, from what I've heard from others.

As you've said, one of the main problems with synthetic bags in the past has been the weight, and this is improving. The other problem is the packed size. Most synthetic bags I've seen take up a huge amount of space in a back pack. But I've only seen one recent synthetic bag, so maybe this has improved also?

[blacksheep]

the EU standard is just that, a standard. The days of cowboys and silly claims aren't behind us, but now many companies go to the effort and expense of submitting product to a uniform measurement..

[Tony]

Hi Sailfish,

For the last few years in the warmer months in the Australian Alps, I have been using a BPL180 Cocoon quilt, I also do flyfishing and camp near rivers and streams. this bag weighs in at around 550 grams. With this quilt I have slept in sub zero temps, last Easter 2010, I was camped near two streams and my tent was frozen in the morning.

In winter, I use the 180 quilt as a liner for my down bag and have been comfortable in well below -10ºC. The BPL quilts are made from Polarguard Delta insulation, the only issue with this insulation is that it can loose some insulation value after many compressions, I have not noticed this with mine but I do not compress my bag too much as room in my pack is usually not an issue.

The Backpacking Light UL 180 Quilt is not made any more but a warmer 240 is, the 240 weighs 680g, BPL are currently out of stock of all quilts, you would have to contact them for information on when they are expecting next shipment.

I can highly recommend the BPL quilts and I would not hesitate in getting another one.

Tony

[sailfish]

The EU standard is certainly more conservative that any marketing figures derived without it, from what I've heard from others.

As you've said, one of the main problems with synthetic bags in the past has been the weight, and this is improving. The other problem is the packed size. Most synthetic bags I've seen take up a huge amount of space in a back pack. But I've only seen one recent synthetic bag, so maybe this has improved also?

I guess it makes sense that the EU standard would be more conservative than manufacturers claims. I know the standard was based on real people testing prior to setting up the standard tests so it should be a reasonable guide. I hope for some comments to get a rough idea of where the Palm might rate on the EU scale. My impression from the Sac1 is that it packs about the same as the Visa, that is same weight packs to about the same size but I was not able to compare directly; so I am not sure about this though it makes sense as both are hollow fibre. However this still means smaller and lighter for warmth assuming the Palm would rate above +5 EU which I strongly suspect.

Regards,
Ken

[SteveJ]

For many years I used synthetic bags; a summer or a winter bag depending on the trip. Most of my activities centered around water, be it packrafting, kayaking, fishing, camping near creeks /river/lakes etc and the risk of getting a wet bag was high, or so I thought. I used to pack my synthetic bag into a compresion sac and then into a dry bag and was careful to erect my shelter carefully to minimise condensation problems etc. So after 30 years of doing this I have never had a problem with a wet sleeping bag. As my knees got older and gut got bigger, I started looking at my pack weight and I decided that if my sleeping bag had not got wet in 30 years of doing some pretty wet trips, it was unlike to ever be a serious problem so I decided to get a down bag. I now do more packraft based fishing and white water stuff than I used to and after a few years have still not suffered the dreaded 'wet slepping bag'. My point is this - If you pack a down bag properly in good quality dry sacs (yes 2 dry sacs), and have a decent shelter properly erected then dampness should never really be a problem, so, why bother with a heavy and bulky synthetic bag? There are some very affordable down bags about that make life a lot easier, I just wish I had learnt that 30 years earlier?

As for comfort, I find both synthetic and down good. Granted the down bags do need to be looked after, but then I look after my synthetic ones also so it is much of a muchness for me.
Steve

[andrewbish]

Can't speak from much experience here but:

The poster-boy for thru-hiking, Andrew Skurka, has apparently relied on a synthetic quilt, from MLD.

World adventurer Ray Jardine seems to have used his 'Ray-way' DIY synthetic quilt in many very cold places.

[ninjapuppet]

Ive had a play with a few bags, and my problem with moisture isn’t when its stored away in my pack. Instead, it’s the moisture that collects from my body while I’m sleeping.
I used my army issue sleeping bag for many many years till I realised what a big load I was carrying. My issue wasn’t the weight, but the space it took up in my pack.
These days below -5C, I would use some combo of down + a synthetic quilt. Any moisture falling from my tent falls onto the quilt. Any moisture evaporated from my body goes thru the down and condenses inside the synthetic layer.

However with the new enlightened Epiphany cuben quilts, maybe the whole down+synthetic layer approach needs a re-think. Its basically got no seam holes to let water in and you use a pump to blow your quilt up according to how thick you want your quilt to be. Ingenious!
http://enlightenedequipment.webs.com/epiphanyk.htm
I’m happy with my setup, but If I was starting out again, I wouldn’t mind giving these cuben quilts a go.

[ninjapuppet]

in regards to your bivy sailfish, I find all bivies from the big manufacturers will end up wet. if its made of a breathable material on top, then it at least there will be some moisture collecting on the bottom half. cant escape that.

[gayet]

From the Epiphany K link

completely eliminating the possibility of body vapor entering the insulation from the inside or precipitation entering from the outside.

Does that mean you just get all damp and sticky if it gets a bit warm inside the bag?

[ninjapuppet]

Probally.
...but its a small price to pay in hostile environments where a soaked down bag spells trouble and you dont have the bulk of a synthetic bag.
You obviously wouldnt use this in warm temperatures.

[durks]

... I decided that if my sleeping bag had not got wet in 30 years of doing some pretty wet trips, it was unlike to ever be a serious problem ...

I use a 500g-fill Rab down bag for all of my walking and climbing trips.

The problem in places like Tassie is that, if you hit several days of cold wet weather, then eventually the down bag will start to get damp (*) and become less effective - even if you're as careful as you can be when pitching and striking camp each day. This just inevitably happens owing to overnight condensation, a wet tent, the subsequent packing away of the sleeping bag each day, etc. etc.

(* I mean: *everything* will start to get damp - but it's the sleeping bag which really matters.)

I had such a cold wet trip last year - about five days of continual rain - and it got me thinking about synthetic bags. So far I haven't come across any that are light enough - and pack up small enough - for my purposes, but I'd be interested to hear any recommendations.

[sailfish]

I didn't want this degenerating into a down vs synthetic discussion or argument. We have probably all heard about all there is say about that anyway. The moisture issue is not really about dunking or getting rained on, I think most of us know how to pack. It is more about what happens over time from moisture from the sleepers body etc especially in high humidity conditions where you can't get things properly dry. It makes sense to use a synthetic quilt over down to keep the outer down warm against condensation but let that all happen in the quilt.

I have been considering the quilt idea for a while and obviously my wobby is along these lines. I think a quilt works better with some kind of bag under it even if that is only a liner to restricts air flow when rolling etc. Weight or bulk or both could be saved by minimizing the area of insulation. Given the bag under you is compressed and therefore not insulating, we rely on the sleeping pad for insulation below, not the bag. So there is no need to have the bag insulated below us. I have experimented with the wobby pegged to the sides of my prolite 4 and this impressively warm and vastly reduces the needed area of insulation. Obviously we need insulation around the sides and connecting to the pad but maybe we can eliminate 40% or so of the area of fill. The question is how can we make this connection sealed and light. Maybe we can have a light shell on the lower side of the bag under the pad and a few inches of insulated baffle to seal over the pad edges. We need a little more width over all to assist movement but I think less area in total. Of course the same can be done with a down system but the weight issue is more important with synthetic fills. I don't think bag hoods achieve anything much, I usually just pull the wobby/quilt over my face and that is warmer than a hood but then I am only thinking to -10C. Does this make any sense?

Regards,
Ken

[andrewbish]

Ken, I am interested to learn a bit more about the wobby pls - brand, price, source - as I may get one.

[cams]

I was actually looking at the enlightened equipment site ninjapuppet posted above the other day. They do synthetic versions of their stuff aswell. I'm considering the lightest fill Prodigy as a summer bag. I sweat alot combined with the humidity. It seems to be comparable in weight to the down version. However, as the amount of fill goes up the differences become greater.

[sailfish]

Ken, I am interested to learn a bit more about the wobby pls - brand, price, source - as I may get one.

Wobby is an army thermolite blanket / poncho liner in an auscam nylon shell. It appears to be intended to line a poncho used as a bivvy. If you want to use it as I suggest you will have to add a 35 cm zipper to stick your head through (not in the centre). If you want to then use it as a tabard, tie the long edges together along the centre, stick your head through and hold it closed around you with a belt. This way it is double thickness over your body, bum and upper legs. Arms are uncovered but I assume by this point you would be wearing sufficient arm cover anyway. Usually I go solo and the possums don't care what I looks like. This is something I have been experimenting with so while I have tried a few patterns and tested it for warmth, I have not put the zipper in the actual wobby yet. It is a multipurpose compromise thing so don't expect it to work like a purpose specific garment. It will not integrate with a rain shell for example. It is intended to be used in camp, not while trekking so I don't see rain as an issue besides it is a clear night that is coldest. My range in NSW central tablelands I am not intending it be used in colder conditions than we get here.

Again, this does not have much loft so I suspect there are warmer quilt options for less weight.
http://www.kitbag.com.au/products/Ponch ... uscam.html

Regards,
Ken

[north-north-west]

sailfish: I like the look of that wobby, but they don't give a weight. Do you have a rough idea?

[sailfish]

sailfish: I like the look of that wobby, but they don't give a weight. Do you have a rough idea?

According to my old kitchen scales, around 770g. So that is 150 g or so more than a mid soft shell or a Mont Zute jacket. It compresses to at least 19 cm in a S2S event dry compression sack size XS. While I could just use a warmer bag, I think this is a more versatile arrangement. The Wobby is quilted so that is not ideal but I don't want to spend too much on experimental gear. I am basically looking for proof of concept first. A better quality fill, construction and minimal size should save considerable weight.

Regard,
Ken