Sea to Summit thermolite reactor

Hey guys, was recently looking into buying a new sleeping bag as my current one just doesn't quite take me down to the temperatures required. Only slightly falls short mind, I've been getting cold enough for it to disturb my sleep. But, considering my current one is a decent size and weight I've since stumbled on teh Thermolite reactor made by Sea to Summit. Apparantly it adds around 5 degrees centigrade and as I already use a cotton sleeping bag liner would just replace this. Does anyone have any experience with one of these?

On a venture round the shops this weekend I noticed a silk liner made by Cocoon (www.cocoonusa.com) and on the packaging they too claim to give around 5 degrees extra warmth. Is this indeed true?

If indeed this is true I think the silk liner is smaller than the Thermolite one.

Cheers guys

265g

try www.ultralightoutdoorgear.co.uk  or www.theruckshak.co.uk

Monkey 48,

here's my experience of the pros and cons of liners (I've various used polypropylene, microfleece polyester & cotton ones) :

+ adds some warmth but forget the number '5 degrees'. If they could give you the Tog values, it would provide some means of comparison. I would guess that thermolite and silk offer very similar levels of warmth. Thermolite is hollow-core polyester so is pretty similar to what they use to stuff synthetic bags. However, my belief is that the warmth-to-weight of a sleeping bag liner is a less than for the sleeping bag itself. I.e. it is lighter to carry a warmer sleeping bag than a sleeping bag plus liner to get to the same warmth. Only a (rather heavy, bulky) fleece or brushed polypropylene sleeping bag liner is going to offer significantly more warmth than the cotton liner you already use.

+ adds versatility to the range of temps you can cope with using your existing sleeping bag.

+ keeps your bag clean and is much easier to wash than a sleeping bag

So to me the big minus of sleeping bag liners is that they don't offer particularly good warmth-to-weight, especially for an item that is single-use. If you are already finding it cold and are using a cotton bag liner, the chances are you won't be much warmer with a silk or thermolite bag liner. You will save a bit of weight and will have something that dries faster, but you might still be cold.  

Viewed purely as a means to stay warmer in cold weather, I'd suggest taking a down vest or jacket to place inside your bag (if there's room - failing that draped on top). A synthetic filled jacket would be fine too. The two or three hundred grammes from minimalist down jacket will provide you with more warmth than a sleeping bag liner IMO.

The other option is to use an overbag like one of these :

http://www.phdesigns.co.uk/product_info.php?cPath=30&products_id=60

but that really is beefing up the insulation and will cost you a kilo in your pack.

http://www.ultralightoutdoorgear.co.uk/shop/shop.php?c=viewproduct&pid=329&cat=38&sid=sidfbfbdfe7f451cf26b11c34c0dde4b2d8

claims 278g for a thermolite liner adding 8C. But how to calculate what temperature you add? I know it would cost me more, but with a budget of 278g I'd take one of these and some cosy socks.

"And how big is it when packed up Dash?"

About the size of a big orange maybe. The material is stretchy and it's comfortable to sleep in.

To be honest my core hasn't been getting cold, it's my legs and feet that have felt close to numb even sometimes wiwith long johns and thick wooly socks on. I'm stuck and confuzzeled. Ideally I'd like to upgrade my bag but funds have just been spent on some lovely new Meindl Vakuum boots and can't really justify the sleeping bag just yet and seeing as I already use a bag liner I thought the different liner might be worth a look. The Jagbag Endura silk liner is a possibilty along with the Thermolite thingy

Ok... so 1) what is your bag, 2) what is underneath you,

A lot of people opt for 3/4 length sleeping mats and then get cold/condensation problems around the legs.

And extra clothing (if it isn't too heavy) could be placed over your legs...

There's a few things worth trying before investing in a new bag.

And seeing Mike's comments above, another option might be to use a Blizzard bag outside your sleeping bag. They are light, cheap, useful backup kit and reusable. But they work best when they aren't over stretched, so whether your sleeping bag would go inside is another matter.

My bag is a Snugpack Softie Chrysalis Autumn and I (over the top) carry a normal foam roll mat (a cheap one admittedly) and a wee aeric. I also have a slim Airic that usually comes car camping.

I did think about one of the Alpkit Hunka bivvy bags. Wud this typically give more warmth for the weight and also double up as an emergency bivvy.

One night I was extremely cold (-8 outside according to my friend's thermo) and I had to get out my Adventure Medical survival bivvy which did keep me warm but I woke up in the morning dripping wet from the condensation that had form on the inside of the emergency bag

Monkey48,

so... it looks like you are more than adequately insulated from the ground... and Snugpacks have a pretty good reputation amongst the synthetic fill bags - unless it is old or well used it should be OK. If I am correct, it has a comfort rating of -5 and an extreme rating of -10. These are only a guideline but it seems reasonable that you should have felt uncomfortably cold at -8.

If you are car camping, there's nothing to worry about - just pack blankets and make a nest! But if you want to be able to cope with colder than -5C self-supported, you might want to experiment a bit with different sleep systems. If you got into your AMK bivvy (presumably the lighter foil version rather than this  which confusingly uses the unrelated term thermo-lite ) inside a sleeping bag then much of the additional insulation will have been achieved by upping the relative humidity & slowing/stopping evaporative heat loss. Inside a tent and inside your sleeping bag, the radiant heat loss reduction associated with being in a foil bag would be pretty minimal. Ironically, the best option might have been to take the foil bag inside your sleeping bag and use it as a conventional vapour barrier. Your clothing might have got clammy (and warm) but it should have kept the condensation out of your sleeping bag fibres.

Mikes suggestions of a light, breathable bivvy work on the basis of trapping more warm air (and keeping your existing insulation dry). If you move about in your sleeping bag you will inevitably squeeze out some of the warm insulating air that was trapped in its fibres. Adding a bivvy around you will cut down any effects of drafts inside the tent and also slow the loss of some of this expelled warm air. It's the same reason why putting on a wind shell massively ups the insulation of a microfleece even though the shell isn't intrinsically insulative.

I suggested a Blizzard bag because it also traps air between the layers and (I am told) doesn't suffer too badly from condensation. As I haven't used one, it's not an endorsement, but the theory is sound. And they don't cost too much. But beware the crinkle...!

And there are plenty of ways to help yourself sleep warmer (taking on some high energy food before you go to sleep for example) that don't require extra insulation. But if none of these work, I think you'll just have to start saving for a warmer bag...

John

Monkey, here are some strategies I use for trying to keep lower limbs warm:

1. using a Sigg water bottle or Platy as a hottie.
2. putting down jacket on top of sleeping bag over lower legs and feet to provide an extra layer.
3. buying Seat to Summit down sleeping socks (I got mine from gogogear in Australia)