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Bivvy-Bag Techniques for Lightweight Campers, Hikers and Trekkers
A bivvy-bag is not just a way of saving money but also of having new, intense outdoor experiences and hopefully some fun; so here some basic tips to avoid too much hardship!
For moisture to pass through the breathable membrane of your bivvy bag efficiently, avoiding a build up of condensation, the conditions need to be:
- warmer on the inside of the bag than the outside
- more humid on the inside than the outside
- have a movement of air across the outside
These conditions normally prevail (unless you have either died or been inundated by rising water.) However there are a few balancing factors to take into account.
Warmth The best sleeping bags for bivvying are probably lightweight, one season and synthetic filled, which dry very quickly if you should experience some condensation. A bivvy bag will usually raise the performance levels of a sleeping bag by 5 -10 degrees, depending on wind factors. It seems to make sense to carry a light sleeping bag (800-950grms) with a contingency of warm clothes such as fleece jacket and trousers that can be worn in the bag if necessary, rather than a 1.5 kilo bag. The clothes can be worn to sit around in and so allow more versatility. However when deciding what to wear in the bag don’t put on more than conditions warrant and get too hot as this will only lead to sweating and a clammy atmosphere. Clear starry nights are the cold ones when you will need more warmth. On hot summer nights especially in warm climates at low altitude you could probably do without the sleeping bag altogether and just wear some warm clothes in the bivvy.
Wind A bivvy bag isn’t going to blow down but if the wind is strong enough to mould it flat against parts of your body then you will lose heat in those places. So, in situations where cold is an issue, choose a site with some shelter from strong wind, such as a bush or rock.
Rain. Close up the foot end drawstring into a small aperture and tuck it under the foot of the bag or pointing downwards. Close the head end drawstrings into a small aperture you are comfortable with and arrange so your mouth is near the opening which is pointing downwards to prevent ingress of rain. Wearing a hat with a substantial brim or peak, such as a baseball cap, will keep the fabric off your face while sleeping and do much to prevent the over enclosed feelings that some people feel when completely inside a bivvy bag.
Midges. Closing up the bag to a small breathing hole over your mouth seems to deter them, or wear a midge proof head bag, or sleep above 600m- 2000ft where they aren’t usually around.
Comfort. Dry, dead grasses and heather are the best for warmth and softness. Flat is good but if your feet are swollen and sore sleeping with them slightly raised can help. Do lay on the ground before committing yourself to sleeping on it as there may be hidden stones. Unless its very windy you will lose more heat into the ground than the sky so a mat of some description is a good idea. The ¾ length, lightweight, inflatable thermarest type are very useful. The closed cell foam rolls are also O.K. and cheaper and lighter (cheaper and lighter still if you cut one in half between two people). I put my mat inside the bivvy as I find it helps to stop me rolling off it in the night
Care of the Bivvy Bag
- don’t use it as a ground sheet over thorns or sharp stones.
- don’t store it wet for longer than a day. It will not take long to dry.
- Roll it up, rather than crunch it, and store in a stuff bag.
- If it gets dirty wash with ordinary soap or one of the special products,
- such as marketed by nikwax, not detergent of any kind.
- Reproof with a spray for breathable fabrics, such as nikwax tx or grangers supapruf
- Finally, for anyone who has never slept outside, in the dark, in remote, high or wild locations, by all means take a friend the first time, but for the full primal thrill of it make sure you do it alone some time.
Tips for Tarps and Lightweight Shelters
Surprisingly, tarps can keep you drier than tents, even through persistently wet weather, due to the superior ventilation. A tent can build up a humid, clammy atmosphere which ultimately penetrates everything in it, whereas a tarp remains fresher and dries out much more quickly. Unlike a tent, if is sage to cook under a tarp because of the impossibility of fumes building up and the ease of exit should there be a mishap. Again good ventilation of a tarp means that cooking moisture does not end up running down the walls.
How to Pitch a Tarp
There are many ways of pitching your tarp depending on the weather conditions and your objective, ie are you just taking a short break from the rain or sun, or setting up camp for the night or longer. Here are some basic suggestions:
- between two trees
- between two trekking poles
- between a tree and a pole
- using an upturned bike as an anchor
- using found sticks as poles – if only thin or short ones are available, try lashing them together
- as a lean-to using two trees or sticks or poles [in wet weather it is worth rem bering that any configuration without a ridge is more likely to hold rain]
- The base of bushes can serve as good anchor points for guys as can tree roots and rocks, particularly flat ones that tend to be more stable under tension.
After pitching the tarp spend a minute under it removing any stones and thorns. leave anything like leaves and pine needles in place to act as insulation and additional mattress. Heather and thick grass make good padding.
Consider the Weather When a storm develops and increase in wind speed has an exponential increase in force and stress on the fixed shape and surfaces of a tent, whereas a tarp can be lowered and flattened to reduce forces on it.
In fine weather, pitch your tarp high off the ground for that feeling of really being ‘out there.’
In wet and windy weather pitch sideways on to the wind and wide and low with the windward side pegged down on the ground. In storms, rocks, logs, earth or sand can be added to the sides if necessary.
Remember a small breeze lowing through is beneficial as it removes the large amount of moisture given off by your body.
Where to Pitch a Tarp Generally the old maxim “climb high then camp low” remains true. The valley bottoms, which often contain the authorised camp sites, will get the coldest during the night because of falling cold air collecting there. The peaks and ridges on the other hand are prone to sudden forceful wind and storms so are best avoided unless that is what you are seeking. Somewhere between the two, possibly with some shelter from rocks or trees makes the best choice.
Avoid dished and compacted ground as rain will pool in depressed area and flood them if it cannot drain off. Again many authorised camp sites are dished and compacted by years of use, by people and their vehicles. Camping under dead trees or any branches which look like they could break off under a weight or rain, or a storm is probably not a good idea.