One Bag, or Two? Summer Bags
The main problem with a good winter sleeping bag is that for most of the year you will be too hot in it. Many is the summer night we have slept on top of our old heavy sleeping bags. Alternately, if you have a summer weight bag you are going to be a just
The main problem with a good winter sleeping bag is that for most of the year you will be too hot in it. Many is the summer night we have slept on top of our old heavy sleeping bags. Alternately, if you have a summer weight bag you are going to be a just a little cold in mid-winter, especially in the snow or even in a very frosty valley. There's nothing quite like spending the whole night shivering. A secondary problem is the weight: winter bags are much heavier, and in summer you are carting all that weight around for nothing. The only solution we have found is to have two or more sleeping bags: one for winter and a very light one for summer.
If you can afford it, a mummy bag rated for -20C (however that might be measured) should keep you nicely warm under almost any Australian winter conditions. That translates to about 700-800 grams of good down. Actually, that weight is probably a bit of an overkill in all but really cold snow conditions if you use some of the Tricks outlined below. You can get bags with even more fill than that, but I think the extra is marketing overkill: the larger quantities of down just get squashed and are wasted. If you buy a good bag from a good bushwalking shop it should last for 20 or so years, provided you use a liner and keep the bag clean. Storage is important, and is discussed below. Think of it as an investment for 20 years: that way it doesn't work out so expensive.
Good very light Australian sleeping bags have been very hard to find, probably because Marketing wanted to promote the most expensive winter bags (with the biggest profit margins). The secondary problem with the lighter bags is that the shell (made of cheap heavy fabric) sometimes weighs 700-800 grams, but has only 150-250 grams of down. This is ridiculous. Of course, you can find cheap bags which are not very warm, but they aren't very light either. There are a couple of models which are recommended by some walkers: the Nitro and the Hotwire by Mont, and the Snowflake and Firefly by Macpac. The makers tend to call these ""extenders"", meaning you put them inside another bag in winter for extreme conditions, but they can be used by themselves in summer. Unfortunately the Mont ones seem to have been taken off the market in 2004. This is odd, because the comment I had from one gear shop was that they could not keep them in stock: they sold out very quickly. More recently (mid-2006) One Planet have produced their Cocoon series, using light fabrics and 300, 400 or 500 g of down. These look very good indeed.
Some very light bags turn out to be warmer than you might expect. There isn't much down in them: in fact the fabric cover may be the heaviest part, but there is plenty of space for the down to fluff up. With a good quality high-loft down they seem to be far more efficient than the heavier winter bags, weight for weight, for this reason. However, you do have to buy two bags for this luxury.