One of my most memorable nights in the mountains was back in the Eighties, bivvying on the Dente Blanche high in the Alps, with a sunset over snow-capped peaks stretching to the horizon. In those days I had a rubbish sleeping bag, which quickly became saturated with condensation from my bivvy. It was a very cold and soggy night!
At 3000m in the Alps, with temperatures plummeting below zero, you need guaranteed warmth from a lightweight sleeping bag (thinner air at this altitude makes walking harder, so you need to keep the weight down). Down is the obvious fill as it is well proven to be the lightest, most efficient insulator around. However, the major drawback with down is that its insulation is instantly lost once wet, leaving you cold and tired the next day.
Waterproof sleeping bags are not new, but to date they have been heavy, bulky and lacking in breathability.
The big issue with a waterproof sleeping bag is: will the down get wet from water vapour condensing into droplets on the inside of the bag’s waterproof shell? This makes the down wet and less thermally efficient, however it is hard to judge, as it depends on conditions inside and outside the bag – but it only tends to be a major problem at extremely low temperatures.
Nowadays, waterproof fabrics are far more breathable than they used to be, and the latest bonding techniques put an end to bulky seam seals. Making the most of this technology, Crux, a company best-known for its exceptional rucksacks and tents, has created a down sleeping bag with waterproof and breathable eVent fabric. The Torpedo 500 looks set to be the most popular model, with bonded seams eliminating leaks and bulky waterproof taping. I could have done with this bag that night back in the Eighties!
The result of all this technology is that the Torpedo 500 should keep you warm down to -10 deg C, which ought to be enough at 4000m as well as for year-round wild camping in the UK.
I used the Crux Torpedo in a well-ventilated single-skin tent in the Lakes, and it worked well, keeping the down dry from the condensation inside the tent. The feel of this bag was good, with a comfy lining and well-fitting hood. The zip has a large side baffle to prevent draughts and cold spots, while a good shoulder baffle helps trap warm air inside the bag. There is a long side zip that stops about 30cm above the foot, which is ideal for venting the legs without getting cold feet.
This is a great bag, but all that extra performance comes with a hefty price tag of £330. However if you really want to comfortably experience some of the most memorable nights on the mountains in winter, then I think the outlay will be well rewarded.
Size: 220x70cm (plus short and long)
Outer: eVent waterproof and breathable fabric
Lining: 20D soft-touch nylon
Insulation: 500g down, 850 fill power
Comfort temperature rating: -10 deg C
Packed size: 22x43cm (22x22cm fully compressed)
Weight: 1050g bag only (1125g with stuffsack)
Made in: Far East
Also available Torpedo 700 £395, comfort temperature rating -20 deg C; Torpedo 900 £450, comfort temperature rating -28 deg C
Verdict: A waterproof bag that is ideal for Alpinists and winter camping, when keeping down insulation dry is essential for a good night’s sleep
First published in Trail magazine, May 2008