new winter sleeping bag

[pjclinch]

Just remember that it depends on the sleeping system you're using i.e. external coverings tent whether it's three or four season, this will have a dramatic affect on which bag you would need.

Quite so: the thing here is the temperature you're looking for is the one inside your tent, not the one on the weather forecast. And if it's a twin-skin with the fly to the ground and no mesh on a windy, cold night that will make several degrees difference compared to a high-cut fly with loads of mesh on the inner.

And ideally if you have a down bag you need to double bag it securely.
i'll not be a lot of good if the water gets at, if its one of the feather variety.

For a down bag to be "not a lot of good" it needs to be properly soaked. If you put it in a functional dry-bag with a roll seal that's not going to happen unless you crash in to a canal and fail to retrieve the bag for some hours and it gets punctured in the impact. Not that likely. I don't double bag mine even if I'm going by boat, but I make sure the single bag is a good one.

Liners are a bit of a talking subject and a bit controversial, if you like them and like a comfort all very well but I wouldn't rely on them in weighing up the warmth of your sleeping system.

For some values of "liners". If it's e.g. a fleece one of course it'll make the whole setup warmer. The main thing with adding warmth through liners of PJs is it's less effective than adding to warmth by using a bag with more effective primary insulation. However, it's more practical to decide to sleep in your clothes than carry a spare, heavier sleeping for colder nights during a week long tour, and it might make more sense to get a £50 fleece liner for a one-off than a £300+ warmer bag.

Pete.

[horizon]

Quite so: the thing here is the temperature you're looking for is the one inside your tent, not the one on the weather forecast. And if it's a twin-skin with the fly to the ground and no mesh on a windy, cold night that will make several degrees difference compared to a high-cut fly with loads of mesh on the inner.

This I'm afraid takes us back to my long-running point that the temperature inside the tent is significant. This means that the oft-touted fix for condensation (excessive venting) is a non-starter. I was recording up to 8 degC difference in outside/inside temps in the summer/autumn. I'm happy with whatever other people choose to keep themselves warm but for me there is a relationship between tent and sleeping bag (amongst other things) that the manufacturers brush aside in their claims to have dealt with condensation.