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When is a bivy sack necessary?
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David Poston
(dgposton) - F

Locale: Texas / Colorado
When is a bivy sack necessary? on 06/14/2013 09:08:38 MDT Print View

What is the conventional wisdom regarding floorless shelters (i.e., no bathtub floor) and down sleeping bags? I'm thinking about shelters along the lines of the SMD Wild Oasis, MLD Solomid, and the like. Is lying directly on your groundsheet (on your inflatable pad) a good idea? My concern would be with water running into the shelter and compromising your insulation. When would a bivy be needed to protect your bag?

Jim W.
(jimqpublic) - MLife

Locale: So-Cal
When you toss and turn right off your pad. on 06/14/2013 09:17:51 MDT Print View

I move around too much at night to stay on my pad. I guess if I strapped the bag to the pad it might stay together.

So I say if your shelter keeps rain off your groundsheet, and you keep the bag on the groundsheet, no need for a bivy.

Bryce F.
(bster13) - MLife

Locale: Norwalk, CT
Works for me on 06/14/2013 09:24:38 MDT Print View

I use polycro groundsheet, sleeping pad and a tarp with my down bag with no troubles. I'd do the same inside any other floorless shelter. Maybe consider a hammock (my new 3 season shelter) if u toss and turn a lot. I've never slept better.

Josh Brock
(needsAbath)

Locale: Outside
Re: When is a bivy sack necessary? on 06/14/2013 09:25:14 MDT Print View

"My concern would be with water running into the shelter and compromising your insulation"

If you have water running into your shelter you picked a bad site to set up. To me if you have a fully enclosed shelter you should not need a bivy... Isn't that the point of haveing one? Using a bivy in a tarp is for the spray that you get from not being fully enclosed.

David Olsen
(oware)

Locale: Steptoe Butte
Re: When is a bivy sack necessary? on 06/14/2013 09:42:46 MDT Print View

I don't always bring a bivy, even tho I make them. Like they said, site selection is a big part of tarp camping.

Where a bivy is necessary with a floorless shelter.
Ledges, cliff bases etc where you have no choice in site selection as to prevent water running under the tarp.
High Desert, alpine, tundra etc. where high winds can suck the heat from your sleeping bag or quilt.
Tundra, Swamps etc where bugs can overwhelm a headnet.

Where it is nice.
Desert, Dunes on river trips, to keep blowing sand out of your sleep system.
Dirty campsites to help protect an expensive down bag.
Using a quilt, to keep the edges out of the dirt and prevent drafts.
Storing extra clothes, safe but handy if the night turns cold.

Tipi Walter
(TipiWalter) - F
Bivy? on 06/14/2013 10:42:25 MDT Print View

To counter some opinions it must be said that on occasion in the Southeast forests we get deluge rainstorms which soak the ground and produce both "ground sheeting" and "lake effect"---you're sitting in a pool of water. I liken it to what happened to Jared Hendren in this BPL link---(though he wasn't in the Southeast)---

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=67460

He said--- "Next it started to rain, really hard, like inches per hour hard. Water started coming under the tarp everywhere, pretty soon all of the ground under the tarp was saturated, and puddles started forming."

Old hands will say "better site selection" but sometimes if the rain is heavy enough no site will stay dry as a deluge produces a half inch of sheeting water moving downhill. Often this water will come over a ground cloth and form pools under a bivy or a sleeping bag and gear. Examples of ground water below---

Pool
I call this "lake effect".

Pooling
This is "sheeting" where I was camped on a never-used site on a slight hill in dead leaves (Big Frog wilderness).

So, some tarps have bathtub floor inserts (with bug netting) and perhaps a good bivy will keep water off your bag if the bivy is sitting in a pool of water---but maybe not.

Billy Ray
(rosyfinch) - M

Locale: the mountains
bivy on 06/14/2013 11:06:24 MDT Print View

There are a ton of campsites in the High Sierra that are shallow lakes when a thunderstorm passes through. Sometimes it seems that most campsites are this way... or that the best ones with the best views. Being so enamored with the beauty of a particular camp, sometimes you don't realize the drainage (or lack thereof) until after you have made camp.

Anyway, a bivy with a waterproof floor and sealed seams gives you some options and some protections in the above.

And, of course, there is always the possibility of your tarp blowing down and flapping in the rain...


bill

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
Winter on 06/14/2013 11:09:57 MDT Print View

A bivy sack is really necessary when sleeping in snow caves, trenches or quinzhees.

It keeps your bag dry. I'd recommend an eVent top for winter and most other bivy bag uses.

Ian B.
(IDBLOOM) - MLife

Locale: PNW
Re: Bivy? on 06/14/2013 11:13:42 MDT Print View

In addition to what Tipi said, there are areas where I'm required to stay at a designated camp site (N. Cascades, Wonderland, etc) and have limited site selection options.

Williswall media (member here as well) has a great video showing a campsite on the Wonderland which had an inch of standing water. Back when I was still backpacking with a traditional tent, I once woke to find myself in a lake. Poor site selection was certainly to blame but I was very grateful that my tent had a waterproof bathtub floor.

This issue is what prompted me to purchase a Zpacks bathtub floor instead of just a polycryo groundsheet for my upcoming Wonderland Trail hike.

The only bivy that I've had any meaningful experience with is the USGI goretex bivy. I've slept through rainstorms without getting wet. I'm sure that some materials breathe better than others but I'm of the belief that venting is just as important as the material. I will still use it for alpine camping but will eventually upgrade to a MLD Event Soul bivy to save myself 1.6 lbs of unnecessary weight.

Edit what Bill and Eric said! Need to type faster.

Edited by IDBLOOM on 06/14/2013 11:15:02 MDT.

Josh Brock
(needsAbath)

Locale: Outside
Re: Re: Bivy? on 06/14/2013 11:34:58 MDT Print View

"Williswall media (member here as well) has a great video showing a campsite on the Wonderland which had an inch of standing water. Back when I was still backpacking with a traditional tent, I once woke to find myself in a lake. Poor site selection was certainly to blame but I was very grateful that my tent had a waterproof bathtub floor."

I've been in a tent with a bath tub floor and poor site selection and have the water come in anyway. Plus I dont think that most Ul bivys are made to protect the user from getting wet while sleeping in an inch of water?

Some times when bad weather hits and your hiking your in for a long night(or three) no way around it. I would not carry a bivy with a fully enclosed shelter just to plan for this. Unless thats your thing, goin backpacking when the weather is just complete garbage.

Hiking Malto
(gg-man) - F
Dirty little secret on 06/14/2013 11:40:57 MDT Print View

On bivies protecting you from ground water. Go use your bivy for a few dozen nights then hold it up to light. After my PCT hike I had dozens of small holes, easy to seal but these would defeat the very reason of using a bivy to combat ground water.

Josh Brock
(needsAbath)

Locale: Outside
bath tub floor on 06/14/2013 11:41:41 MDT Print View

Also if that is all your worried about why not just get or make an individual bathtub floor... it would be much lighter than a full bivy.

Or just carry a piece of poly cro as a ground mat, punch some holes in it with a hole puncher and if the weather gets that bad, use guy line and bring it up around your sleeping bag to keep the river that you set up your tent in out.

There are plenty of solutions to that problem that dont involve lugging around an event bivy with your Ul tent.

Ian B.
(IDBLOOM) - MLife

Locale: PNW
Re: bath tub floor on 06/14/2013 14:36:58 MDT Print View

"Also if that is all your worried about why not just get or make an individual bathtub floor... it would be much lighter than a full bivy."

"re are plenty of solutions to that problem that dont involve lugging around an event bivy with your Ul tent."

I can't tell if you are asking me or the OP. If this is directed at me, I use a bivy as a standalone shelter in the conditions mentioned earlier. If I'm using a tarp, I just use a ground sheet until I receive my bath tub floor later today or early next week.

Fortunately I've only found myself in a lake once (described above) and I wasn't in a bivy then. I've slept through torrential rain storms in my USGI bivy without getting wet with the exception of minor condensation). Didn't use a ground cloth in the military and the USGI issued Thermarest didn't fit inside it all that well so the system from ground up was

1.Pad (1.5lbs)
2. Bivy (2.5 lbs)
3. Sometimes a poncho hooch mission dependent. (1.5 lbs plus bungee cords weight?)

While bomber, this system is way too heavy for BPL purposes.

Josh Brock
(needsAbath)

Locale: Outside
Re: Re: bath tub floor on 06/14/2013 14:54:41 MDT Print View

"I can't tell if you are asking me or the OP"

Sorry its not really directed specifically at anyone. Its more for anyone that feels a full bivy is necessary in a fully enclosed shelter.

Ian B.
(IDBLOOM) - MLife

Locale: PNW
Re: Re: Re: bath tub floor on 06/14/2013 15:06:48 MDT Print View

"not really directed specifically at anyone"

Gotcha! The one issue I'm tring to dial in for my Hexamid Twin Tarp (sans net) is mosquito control. Not sure if I'm going to try a Borah bug bivy or not. Will probably order a S2S Nano Mosquito Net Duo (~4oz) and see if I can make it work before I commit to a bivy.

I figure between the Hexamid Twin, Twin floor, and S2S Mosquito Net, I'll have a great modular system where I can cowboy camp in comfort but still have a tarp to dive under when the weather turns crappy. Just a theory at the moment though.

EDIT fwiw I exchanged emails with Borah and aked them if the bug bivy had a bathtub floor. He indicated that it technically does not but that when you sleep in it, the silnylon floor is pulled up in a way where it acts like one.

Edited by IDBLOOM on 06/14/2013 15:08:11 MDT.

Doug I.
(idester) - MLife

Locale: MidAtlantic
Re: Re: Re: Re: bath tub floor @Ian on 06/14/2013 15:22:13 MDT Print View

"Will probably order a S2S Nano Mosquito Net Duo (~4oz) and see if I can make it work before I commit to a bivy."

Richard Rankin is using one with his new HMG mid and he seems to like it quite a bit. If you PM'd him I'm sure he'd be happy to give you more real world info.

Josh Brock
(needsAbath)

Locale: Outside
Re: Re: Re: Re: Re: bath tub floor @Ian on 06/14/2013 15:25:55 MDT Print View

so off topic-- but now you guys got me buying one of those s2s bug nets for my tarp!2.9 ounces is pretty light!

Dale Wambaugh
(dwambaugh) - MLife

Locale: Pacific Northwest
Re: When is a bivy sack necessary? on 06/14/2013 15:47:37 MDT Print View

IMHO, when you are using a minimalist tarp with poncho-like dimensions, stormy weather expected and bug protection with a tarp, and day hiking CYA. Winter snow shelter camping is a common use too.

Sometimes you don't get to pick a site. Some areas have restricted sites, or the site available has compressed soil that allows water to run through it or collect in puddles, right where you are pitched. Sometimes you run out of time and have to make do.

I agree that a bivy shouldn't be needed with a full shelter. I do like to use a footprint under to help with water issues and protect the tent floor. Tyvek or polycryo film are fine.

David Poston
(dgposton) - F

Locale: Texas / Colorado
"Full shelter"? on 06/16/2013 17:53:59 MDT Print View

When you guys say "full shelter," are you referring to an enclosed tent with bathtub floor or a floorless shelter such as a MLD Solomid?

I would never attempt to use a bivy inside a floored shelter. However, I'm more interested to know whether those who use a Solomid type shelter feel the need for a bivy in addition to a groundsheet to protect their down bag.

Edited by dgposton on 06/16/2013 17:55:49 MDT.

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: "Full shelter"? on 06/16/2013 18:05:51 MDT Print View

8' x 5' tarp or similar size then a bivy.

8' x 10' tarp or similar no bivy.

Hexamid solo or Trailstar no bivy.