[pct-l] Bivy sacs

Tue Sep 7 15:51:45 CDT 2010

Ned,

The bivy sack I use isn't one of those hot heavy waterproof ones that you often see mountain climbers use.  I'm using a Mountain Laurel Designs Soul bivy (7.9oz weight).  Unlike some other UL bivies that have just a top opening, this one has a side zipper so its just as easy to get into as a sleeping bag.  This isn't meant to be a shelter against direct weather as the top material is water resistant verses waterproof (the bottom is waterproof though).  Not being truely waterproof, the momentum fabric instead is very breathable so condensation isn't a big problem (solving one of the biggest problems with most bivy sacks).  It works fine against misting or short light rain, but it isn't going to keep you dry in a downpour.  Thats why a small UL Tarp (like my MLD Grace Solo tarp) is carried with it.  The purpose of the tarp is to keep any direct rain/snow off of you, while the bivy sack adds some additional protection against any wind blown rain or misting that makes its way under the tarp (a much bigger tarp would eliminate much of this spray as an issue but would be more unmanageable in strong winds since you have essentially a giant sail).  The bivy sack also adds extra wind protection, additonal warmth, and some bug protection when sleeping ( a net that zipps up over over the face opening).  On my PCT hike, I only used my tarp maybe 9 times for rain and snow, but I slept in my bivy sack at least 70% of the time as I was using it as a wind break or bug protection as I slept.  So having a small tarp/bivy combo was more versatile to me then a large tarp.  Since I don't hang out in camp other then to sleep, the lack of space in a bivy to move around in while protected from the bugs wasn't an issue.  For someone who wants to hang out in camp for a few hours in Northern Yosemite in early season while the Mosquitos are swarming, probably would want something a bit bigger.  Now if bugs aren't an issue and I don't need to remain button up from then, I do like being under my tarp in rain since it feels more roomy and I do have space to sit up and do things. 

To answer your question, in my case, the tarp provides the majority of weather protection while cooking/eating under and provides the space needed for changing clothes. I can pack up all my gear including a ground cloth (though not necessary with the bivy, I still like using one in rain) while staying dry under the tarp and then stuff my tarp in the outside mesh pocket on my backpack at the last minute.  If I'm not camping in an established campsite, I may even do my "business" in a hole under the tarp before leaving the next morning to avoid the rain.  I can often camp in spots that no tent user could dream of fitting in.  And on days where I'm only using the bivy sack and not the tarp, camp setup and take down is easy and fast since I'm just throwing my sack on the ground.  One of my most magical nights on the trail was the night before reaching Kennedy Meadows when I woke up to a moonless sky and saw the Milky Way stretching overhead from one peak to another.  Looking again latter, it was interesting in seeing how it had rotated several degrees.  This is something that I would have missed if I had been in a tent or under my tarp.

In the case of your student, the type of bivy he was using looks to be a more traditional heavy waterproof one where condensation is likely to be an issue, even if it keeps him dry from any rain or snow.  The way you describe how he was using it is completely different from what I would do and seems better suited for ideal weather or at least a snow cave.  I certainly wouldn't recommend camping that way in snow and would want at least a tarp to go with it.  I hope he learned a leasson in what not to do on that trip.

For someone who was going to be using a tarp in snowy conditions beyond the serveral inches normally seen near the shoulder seasons, I'd likely change mine out for one of those pyramid shaped tarp shelters that MLD, Oware and a few others make,  These type of shelters offer protection from all directions and their shape is good for strong winds as well as shedding snow loads.  But for true winter camping, I'd favor a good 4 season tent like most people.

-Miner

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