Topic: Bivvy in minus temps (Read 7342 times)

Scribble · « **on:** December 05, 2010 »

I'm hoping to get a night out soon around the mournes in my bivvy but I'm a wee bit worried I might not wake up due to hypothermia :0( , I have a vango supernova 3000 that they manufacture says it has a comfort of -7 , how do these settings get worked out ? Do you have to sleeping in thermals etc , I am going to use a survival blanket inside bag or would I be better getting a liner

All advice would be nice please as I want to convince myself I will be fine so the wife will believe me when I say I will be ok ,

Cheers Andy

chris · « **Reply #1 on:** December 05, 2010 »

You should be fine in that mate. Thermals or some sort of comfortable clothes to sleep in wouldn't be a bad idea and a liner can only help. The only thing I would say is if your mats rubbish it doesn't matter how good you bag is, your gonna get cold! A decent mat is equally as important as your sleeping bag.

Scribble · « **Reply #2 on:** December 05, 2010 »

Quote from: chris on December 05, 2010

You should be fine in that mate. Thermals or some sort of comfortable clothes to sleep in wouldn't be a bad idea and a liner can only help. The only thing I would say is if your mats rubbish it doesn't matter how good you bag is, your gonna get cold! A decent mat is equally as important as your sleeping bag.

Cheers was a bit nervous about the bag , I'm sitting in work now looking on net at some thermarest mats

So maybe a late night purchase to keep me excited till I get home to bed in morning

twentyclicks · « **Reply #3 on:** December 06, 2010 »

As it happens, I was just joking on another thread so have my reference document open (Mammut Sleep Well - all you ever want to know about ratings, and more).

A quick look reveals your bag was tested to EN13537, where the 'comfort' is typical for average woman user and 'limit' or 'lower comfort' for the average man. The 'limit' value for your bag is -5 so it's a shade over 10 Tog.
These values depict a full night of sleep. The extreme rating means you can survive miserably if healthy, hydrated and fed for about 8 hrs... ie life or death.

As Chris says, a liner and warm base layers will help, but a good mat (cheap foam ones are very good) and clever bivy location matter more.

There is debate about wearing warm clothing or as little as possible in your bag - it can make a critical difference as long as the principles are understood:
You want the loftiest insulation available to loft... this is usually the sleeping bag, (but if you are extending a 3 season bag, it might be your down jacket). To loft fully, these require heat from your body, so jumping into a cold bag fully clothed can result in the bag never achieving full loft as it receives heat too slowly by which time you have lost a lot of heat, so you shut down a bit, expelling even less heat and the situation never improves. You need to establish the environment quickly and then it is easier to maintain a gradient of trickle heat loss.

Doing a few squats or star jumps before jumping in to any bag will temporarily increase your body's heat output and the excess will loft the bag quickly. Base layers or a liner will normally suffice for added comfort. I would have my extra warm layers in the bag with me if I thought I might need them and then pull them over or slide them on if the bag was proving ineffective. I personally feel, wearing clothes is most effective in bags with little insulation of their own, but try anything if you feel in danger.
For any bag rated above or just below freezing, wearing a down jacket inside is wisest; for bags warmer than the jacket, drape it over the top.

suspectmonkey · « **Reply #4 on:** December 06, 2010 »

Will second (or third as the case may be!) the part about having a decent mat under you. In Donard Wood I used my full length self-inflating mat, but then added a 3/4 length off-cut of cheap foam camping mat under my torso. Felt absolutely no heat loss to the ground and the extra padding made for a very comfy nights sleep! For the few grams added by a bit of foam mat I'd highly recommend it.

fatty-arbuckle · « **Reply #5 on:** December 06, 2010 »

My vango viper 500 with thermals, liner and good mat wasn't enough the other night. Had to sleep in my "smoke damaged" down jacket. My upper body was fine though, however my legs were a tad cold.

Temp was around -5

RedLeader · « **Reply #6 on:** December 06, 2010 »

I slept in a single skin tent on Sat night in a Vango Ultralight 300 which is recommended to +2. I had a silk liner and wore top/bottom thermals (from Tesco) and was on an extra thick (non-inflating) foam mat. I was defo a bit cold and through the night threw on a down vest which warmed me up nicely. I reckon if I'd worn the vest from the start I'd have been fine but I could feel the cold (and lumpy ground) through the mat. Your bag is rated to much lower and you'll be in a bivvy bag so I'd say you'll be fine. Only thing of note was I was sorry I had a short sleeved thermal top - think a long sleeved one would have been much comfier.

Scribble · « **Reply #7 on:** December 06, 2010 »

Cheers guys I will let the wife read your replies , she still thinks I'm nuts to be thinking about doing it ,

I will use my full length mat and buy another foam for the extra layer , I'm hopefully heading up Thursday week if anyone fancys it , looking like parking at Donard and heading from there as the roads are still very messy ,

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Author Topic: Bivvy in minus temps (Read 7342 times)

Scribble

Bivvy in minus temps

chris

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twentyclicks

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suspectmonkey

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fatty-arbuckle

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RedLeader

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Scribble

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