I've read psychovertical's article on using an overbag, and it sounds like a pretty flexible idea. Thing is, I own a largish synthetic bag, and a smallish down bag, and if you put the two inside together, you lose so much loft on the two of them that they aren't working that well at all. I've seen a few dedicated overbags: 1. Phd's overbag weighs 1kg and has a drishell outer, but is expensive at £155 2. Decathlon's Quecha overbag - dirt cheap at £14 , 500g, claims it adds 5 degrees. Not got a hood though. 3. Numerous US brands (MEC, Big Agnes) seem to sell them, but they aren't available here. So has anyone tried the idea? Did it work? Advantages/disadvantages? Andrew
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  I've heard of slightly larger overbags being used by two or more folks to conserve body heat in extreme low temps in a survival situation in high mountain conditions though. Early explorers in America and elsewhere too did this all of the time it appears.
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Also the Buffalo pile pertex sleeping bag systems of old - circa mid nineteen-eighties - employed such an overbag idea in their range, so it is essentially nothing new really. One can still get Buffalo outer and inner bags today too!A Buffalo pertex inner liner for a sleeping bag too adds a few degrees, or up to one old 'season' to a bags warmth rating as well. You can up any bags warmth rating by just basically wearing more clothing within when sleeping of course, similarly, C.
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| Edited: 16/11/08 04:21 |
 Hi Cybergibbons, I have done this and have advocated it on these forums a few times before. If you start from this thread and check those linked, you should get most of my previous comments on the matter: Bag combination comments John
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| Edited: 16/11/08 08:25 |
Thanks there, John, That was a thread I had missed out on here before also somehow or other! Good stuff on there too!
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Thanks John - a good summary of the advantages and disadvantages there. I'm tempted to give it a go with the cheap Decathlon overbag, see how that goes and then maybe upgrade. The PHD one is just too expensive, although having a drishell outer would be useful. I might also have a dig around to see if any of these overbags can be obtained from the US.
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 By a happy coincidence, I'm planning on using a Synth'/Down combo' in a couple of weeks time. I'll report back on how it goes.
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Kev, can I ask what bags you are going to use? Did you get the outer specifically for this?
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Yes please, Kev! A lot of us await the details, and the report with baited ready breath, I do feel there too! 
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| Edited: 16/11/08 12:29 |
 Back when all I owned was a 3 season synthetic bag, when I car camped in winter I used to put a cheap, square woolworths sleeping bag over my mummy bag and I was never cold.
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Kev, can I ask what bags you are going to use? Did you get the outer specifically for this? Trevor D Gamble wrote (see) Yes please, Kev! A lot of us await the details, and the report with baited ready breath, I do feel there too! Sorry guys. Busy, busy I'm just using a combination of what I've already got; Snugpak Merlin on the outside, Rab Quantum (150?) for the inner. There's room inside even with me in there so the down's not overly compressed. It looks promising. If I don't report back, you'll know it's all gone horribly wrong
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lol! Let us not think that and tempt fate any further then!
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 I tried using a macpac escapade 150 down linner inside a snugpac travelpack bag in the spring of this year on Dartmoor. I found it worked ok as I do tend to be a cold sleeper and it was +3 degrees inside the tent when I went to bed so could have got colder during the night but wasn't really cold enough to test it properly plus I was wearing clothes and a primaloft jacket while I slept. The macpac bag is very short and doesn't have a hood so couldn't pull it up passed my shoulders so I did wake up at one point with cold shoulders and at the same time my legs did get a little hot and clamy. I have considered trying the down bag on the outside but not yet tried it that was round.
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I have a rather excellant synthetic / down bag from Marmot. Down on the inner layer and primaloft in the outer layer with a decent pertex fabric to the inside and outside. It is XL too so I don't get cold feet from compressing the foot section to fit my shoulders in like my old bag. It works well as the primaloft layer actual resists water getting to the inner down from condensation in my single skin tent. Even if I get my bag completely wet, say by placing my feet inside a dry bag to prevent the bag getting wet from condensation from the tent (got very wet from even more condensation caused by the dry bag), it is still warm. I think it is the Marmot Fusion and was bought quite cheaply as they no longer produce it. Seemed a good design if you ask me. I have nearly bought a vango ultra light100 (lightish synthetic 1 season) for £30 to use inside for winter but decided against. I reckon I will suffer with a down jacket and all the clothes I can wear inside the sleeping bag, but I reckon a 2 bag system does work. A warmer conditions down bag and an XL synthetic for use as an overbag in winter would be a good idea. The buffalo bags were designed for snow holes and military use I believe. Where you have the centre zip and you just use a combination of bags as the weather gets colder. Ranging from a single summer bag through to and inner plus outer winter one for arctic conditions. The plus was that they offered warth when wet. Never liked the idea as I prefer warm and dry over warm and wet. All I know my fusion is an excelant bag and I have had nights where I got wet from condensation and still had a good nights sleep. This is important in single skin tents as you might not get your gear dry if the weather is consistantly bad.
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Paul, I have seen this bag on the net; and I'm sure there are others out there based on the same idea. It gains a bit over the two-bag system based on weight... but loses several of the major advantages IMO. No opportunity to have a lighter weight option in warmer weather. No ability to air the layers separately to speed drying times No redundancy in case of one getting wet, zip failure etc. So I wasn't sold. But then, I'm not sold on single-skin tents either! So each to their own John
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So I wasn't sold. But then, I'm not sold on single-skin tents either! So each to their own John
I'm not sure I'm completely sold on single skin tents neither. But was stuck on something big enough and light enough. Less than 2kg yet still long enough for me to get in it and lie straight. The single skin was the only thing I could find that didn't cost an arm and a leg (and at least the hand of the second arm). Hilleberg Atko anyone? No wonder were a nation in debt with the number of Atkos I've seen around the place. My tent cost £100 with a few bits and bobs thrown in free. Can't knock that for a decent sized, lightweight shelter.
My fusion was at a very good price (about 40% off UK RRP) for this product. It was either the XL fusion or a standard Rab down bag for well over twice the price (that would have been too small). How quickly does down bags dry compared with synthetic bags?
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How quickly does down bags dry compared with synthetic bags?
Tricky question, Paul! Simple answer .... it depends!
If both bags are totally soaked, then the down bag will take an absolute age to dry and might never fully recover as the down clumps into useless bundles. However, if they are just slightly moist from condensation, it may be possible for a down bag to dry faster than a synthetic of similar weight. Here's what the eccentric down experts at Stephenson's Warmlite have to say : As Down dries from the surface, interior moisture wicks to the surface where it has access to dry air and heat for rapid evaporation. With synthetics the surface lofts and insulates the interior so it takes much longer to get the needed heat in and the water out. BUT, if you saturate a Down bag and let the Down all clump together, drying will take much longer: you have greatly reduced surface area and greatly increased thickness to be dried. Thus the stories of Down being slow to dry! Those stories are correct when you put them in context. Wool is similar to Down in wicking ability and moisture holding, but being available only in dense heavy woven form it doesn’t compress as it gets wet (it’s already compressed). Both Down and wool can absorb many times their weight, within the fibers, with no effect on insulating ability. Add more than about 5 times their dry weight and Down starts to collapse and lose insulating ability, while air spaces in wool fill up and you lose insulating ability. My point was simply this... (explained by illustration!) Imagine you have a winter bag with a 3 inches of loft. Or an inch of synthetic over 2 inches of down. If you are air drying the bags, then we can assume that moisture can evaporate outwards from both inside & outside faces of the bag. In a one-bag solution, that means that the middle of the stuffing is 1.5 inches insulated from the surface in either direction. Consequently, it will take a long time for moisture to wick out & dry off. In the two bag solution, you have a synthetic bag with a maximum insulated depth of 0.5 inches and a down bag with a maximum depth of 1 inch. Both should be able to dry out much faster. Moreover the dew point, where the worst of the damp would have accumulated, might now be entirely in the synthetic bag (or at worst in the outermost layer of the down bag) so there's much less moisture to get out of the down bag anyway... In any case, you can see that it works by comparing the drying times of two 100 weight microfleeces versus one 200 weight fleece by roughtly the same principles.
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