Wednesday, 13 April 2011
Thunder on the Tundra - The Gear - Sleep system
More gear ramblings from our adventure in the far north. In the old days I would have just said "here is the sleeping bag I used" but these days it's 'sleep system'...
So taking my cues firmly from the Jorgen Johansson school of lightweight winter gear last year I purchased a -7C rated Western Mountaineering Ultralite sleeping bag (879g in Long) as a replacement for my Alpkit PipeDream 400 which has always been a little under-gunned for the Scandinavian winter. While I have switched to quilts for 3-season sleeping I still like to have a bag in winter. I find them less draughty, especially when thrashing around at night in a cold tent.
And so to the quilt. This is the key piece in the system. I had read about people combining down and synthetic bags/quilts for winter backpacking over at BPL. Jorgen had been singing the praises of doubling-up for the last year and it formed a large portion of our discussions before and during the trip. Jorgen uses a home-made quilt with a unique mesh inner but more importantly it's filled with synthetic insulation. The key here is the synthetic insulation's ability to keep insulating even when wet, unlike down which turns into a useless lump. As my sewing skills are far from ready for a project like this I went down the route of ordering a Mountain Laurel Designs Spirit 30 quilt. In XL, Pertex Momentum 50 shell and eVent head and foot strips it weighs 556g.
So what's the point of having two sleeping pieces instead of one super fat sleeping bag? The key is trying to obtain the benefits of both insulation materials. Down is very warm for it's weight but fargile. Synthetic insulation is heavier but more resistant to damp. Basically you keep your down sleeping bag nice and dry by slipping the synthetic quilt over the top. This protects the bag in a couple of ways:
From the inside - Moisture from your body passes through your down sleeping bag and condenses in the outer layers which will begin to 'collapse'. If the outer layer is a synthetic quilt then this build up of moisture, that increases ever day, won't affect the loft of the synthetic insulation keeping you warmer.
From the outside - Frost formed by condensed water vapour on the inside of your shelter showers down onto your sleeping bag, your body heat turns this back into a liquid and your bag slowly collapses. Frost also gets picked up when moving around, especially in the foot area. With a synthetic quilt on top any moisture is more easily dealt with and your down bag keeps dry and fluffy next to your body. The eVent foot strip on my MLD quilt coped particularly well with my feet brushing against the tent walls. Jorgen pulled his Paramo jacket over the end of his quilt.
Other benefits from a 2-piece sleep system? I can use both pieces at other times of the year. My MLD Spirit quilt will become my main sleeping piece during the coming peak backpacking months. My WM Ultralite bag is great for 'shoulder season' and lower elevation winter trips. This means that as yet I don't have need for a very expensive winter-only sleeping bag that might only get used for one week each winter. Another benefit we found on this trip was using our synthetic quilts as 'comforters' during lunch breaks and around camp where their increased resistance to moisture means they don't have to be treated with kid gloves and leaves our sleeping bags safely stored in their dry bags until needed for sleeping. Jorgen, especially, was grateful to being able to pull out his quilt at rest stops to re-warm his cold, damp feet.
In addition to the sleeping bag and quilt I also wear insulated jackets and pants. These comprised of a Rab Xenon ultra light synthetic jacket (60g Primaloft), Patagonia Micro Puff Special pants (80g Polarguard) and if I still felt cold I would wear my Montane North Star down jacket (200g+ 800 power fill).
Under us we used similar combinations of Closed Cell Foam and inflatable pads. 14mm thick CCF full-length pads provide plenty of insulation from the cold snow and are idiot proof, unlike insulated inflatable pads, an important consideration when you're a couple of days away from civilisation. For a bit of cushion we used short Thermarest inflatable pads, Jorgen a NeoAir (260g) and I used a ProLite (303g) which offered some nice ultralight plushness to our shoulders and hips after a hard days skiing.
Did it all work? In a word, yes. To be honest we didn't endure anything below about -15C but I slept well and warm most nights. A couple of times it took a while to warm up, possibly due to over-tiredness or not eating or drinking properly but the synthetic over-quilt really made a difference to my comfort on the trip. My down sleeping bag stayed warm and fluffy the entire time apart from a small area around the face where my breath condensed. Towards the end of the trip I got to dry my quilt out on a couple of occasions in the sun and wind and I was really surprised how effective this was. On the last night my quilt and sleeping bag were almost as dry and lofted as the first night. I know some people prefer vapour barrier technologies to combat moisture accumulation in their sleep system but there is something about the idea of stewing in my own juices doesn't appeal to me. I'll stick with this system for the foreseeable future.