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I don't get UL bivy
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Dave -
(FamilyGuy) - F

Locale: Up there
Re: Yes, apples to oranges on 06/19/2012 10:45:16 MDT Print View

"ahhh ... but you cant go HA HA HA HO HO HO at the condensation gods even with a bag with good DWR and more down fill ;)"

Ah come on, synthetic fill gets wet too....! Or does it? Maybe you have a special, one of a kind bag made with unobtanium....

Edited by FamilyGuy on 06/19/2012 10:46:05 MDT.

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
Deja-vu all over again on 06/19/2012 10:53:46 MDT Print View

Here we go again.
Tarp & groundsheet W/ bivy
v.s. tarp W/ floored bug net
v.s. UL single wall tent.

Having tarped for years I find a UL tent like a SMD Skyscape or a TT Moment is faster to set up and strike and is often lighter than a tarp and floored bug net of the EQUIVALENT MATERIAL. No worry about splash, no double setup.

And you can have the bivy&headnet "solution". I want bugs and creepy-crawlies totally out of my sleeping area.

Mary D
(hikinggranny) - MLife
Tarp vs. tent on 06/19/2012 12:23:02 MDT Print View

My ZPacks Hexamid Twin (room for my grandson, my dog and me) weighs 17 oz. including cuben bathtub floor groundsheet, guylines and stakes. Tarp (GG Spinntwinn) plus ground sheet plus bug net (I needed one big enough for both me and my dog) is 6 ounces heavier. Of course there is a bit of a price differential!

I tried a bivy once. It was so slippery that I not only kept sliding off my air pad, but after some tossing and turning the silnylon part of the bivy ended up on top, where it of course caused condensation. It was almost as bad as the silk liner I tried when my sleeping bag was new! About 2 a.m. I tossed the bivy into my pack and never used it again.

My worst experience with wet insulation was with a synthetic sleeping bag. I can tell you from bitter experience that a wet synthetic bag is just as cold as a wet down bag!

Edited by hikinggranny on 06/19/2012 12:26:25 MDT.

Clayton Mauritzen
(GlacierRambler) - F

Locale: NW Montana
Re: Tarp vs. tent on 06/19/2012 15:28:42 MDT Print View

If you're sewing up down quilts, then a bivy is a much easier MYOG project. Check out this thread for some more details.

Hobbes W
(Hobbesatronic) - F

Locale: SoCal
I don't get UL bivy on 06/19/2012 17:46:43 MDT Print View

I don't see the math (weight) nor functionality of a bivy.

First of all, a bivy bottom (used in lieu of a groundcloth), made out of some kind of WPB like silnylon, is almost by definition going to be heavier than window shrink wrap used with a floorless tarp.

By definition, I mean it has to be strong/heavy enough to sew, even @ 1.3oz yrd2. Compare this to really lightweight WP window shrink wrap, which has good puncture resistance, but almost even better, is so cheap ($2-3 for a 7x4) that it can be discarded after a trip.

Secondly, the incremental increase in tarp weight for a full coverage tarp (eg tapered/cat cut 10x8) vs bivy tarp (7x5) is nominal, especially considering you still have to take the same poles, guys, stakes, etc.

Third, coverage is a function of square footage. A 5x7 tarp will cover 35 sf, whereas a tapered/cat cut tarp, starting off @ 10x8 will come in the range of 65-70 sf - nearly 100% greater coverage/protection.

Fourth, if you're using a bag/quilt (either syn/down) built out of a quality DWR, like Teflon coated M50, in combination with a full coverage tarp, then you already have good splash resistance. That is, if any rain was to find its way in.

Fifth, using a quilt/down without an additional layers on top and/or a closed WP bottom (like sil) cuts down on condensation.

Sixth, using high quality insulation (eg 900FP down) will achieve much greater warmth with the addition of 2-4oz vs 4-6 oz of bivy material. If you want extra warmth or want to avoid drafts, simply make the quilt bigger and/or overstuffed. Either option will weigh less than a bivy.

The only advantage I see to using a bivy is the weight saved by using a poncho tarp vs carrying a stand-alone 5x7 bivy tarp. Yet, this 'advantage' also has a drawback - who really wants to hike in a poncho if it's raining? And do you bring along a wind shirt for marginal conditions?

I think many who have experimented with bivy tarp and/or poncho tarp combos have come full circle back to the tent concept, in terms of full coverage, but are simply using over-sized tarps to fill the 'tent' function. That's me.

drowning in spam
(leaftye) - F

Locale: SoCal
Re: I don't get UL bivy on 06/19/2012 18:03:52 MDT Print View

Someone said a quilt with a headnet is sufficient for bugs. I disagree. I'm sure ticks and clown beetles have no problem getting under the edge of a quilt, and ticks would have an especially easy time at the drawstring footbox closure and head area. This spring slept in an area very heavily infested with ticks and I was very happy to have my bivy with me.

Hamish McHamish
(El_Canyon) - M

Locale: USA
_ on 06/19/2012 19:26:02 MDT Print View

I'm mostly with Hobbes.

I have played around with a few setups, as we all have. I don't think any one setup is best for all people all the time in all conditions.

A few observations:

- Many say using a bivy means there's no need for a groundsheet. Perhaps that is true in dry areas. But on damp ground I find that if I don't use a groundsheet, all my stuff gets filthy with moist dirt stuck to it, plus pinesap (cuz I love to sleep amongst the conifers). Just a simple 2mil poly drop cloth under my tarp lets me keep all my stuff clean and dry. Polycryo would be even lighter.

- I don't understand the argument that a bivy "protects from rain spray" and yields weight savings from using a smaller tarp. With the superlight, super-breathable NON-WATERPROOF bivys, if they get wet they leak through, period. The real fix for that is a larger tarp. If the "rain spray" is so mild that Intrepid fabric stops it, then it's not really much of a spray. Early on in tarping when I screwed up, I watched rain spray get on my Ti Goat Raven Omni bivy. The stuff got wet, then soaked through. It is not a magic water barrier.

- I don't buy in to the practice of my shelter setup being a tomb, where all I can do is lay there: no room to cook, change clothes, etc. IMO there is a valid "transition zone" between entering the shelter and actually going to sleep. I prefer to not be in a claustrophobic clusterfark during such times, struggling against an industrial grade faff factor.

For me, my preferred soloist solution is an 8x10 tarp with an inner bug tent (my MLD bug bivy weighs 6 oz) and a thin, disposable groundsheet. In cold weather I skip the bug bivy. I get the fun, openness, and ventilation of tarping. I have good bug and rain protection. I can hang out after a long day (and sleep in after a dreamy night) without feeling entombed. This setup is adaptable, the weight is very reasonable, and the faff factor is low.

eric chan
(bearbreeder) - F
Re: Re: Yes, apples to oranges on 06/19/2012 21:47:21 MDT Print View

"Ah come on, synthetic fill gets wet too....! Or does it? Maybe you have a special, one of a kind bag made with unobtanium...."

condensation on synth ... pfft ...

itll dry out with body heat and a hawt nalgene ...

Dave -
(FamilyGuy) - F

Locale: Up there
Re: Re: Re: Yes, apples to oranges on 06/19/2012 22:34:19 MDT Print View

Nalgene? Blasphemy!!!

Dan Durston
(dandydan) - F

UL Bivys on 06/19/2012 22:53:27 MDT Print View

Bugs aside, I'd take a full coverage tarp (ie. pyramid) + groundsheet, over a partial coverage tarp (ie. A frame) + bivy. Much nicer in high winds, rain splashing, spindrift snow etc.

Come bug season, I'd replace the groundsheet with an inner net tent rather than a bivy for a lot more space and a little more weight. For example, the MLD Bug Bivy is 6oz and the MLD SoloInner or Serenity Shelter (both much larger) are 8.5oz. 2.5oz well spent unless you're hiking right until bedtime.

Edited by dandydan on 06/19/2012 22:56:05 MDT.

Steven Paris
(saparisor) - M

Locale: Pacific Northwest
I don't get UL bivy on 06/20/2012 00:27:12 MDT Print View

"itll dry out with body heat and a hawt nalgene ..."

C'mon, Eric! I understand typing short-cuts for some words, but the word "hot" is shorter than the word "hawt"! At least try! ; )

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: I don't get UL bivy on 06/20/2012 00:50:20 MDT Print View

Hawt must include the Canadian accent?

At least he isn't throwing around a lot of those redundant and heavy "U"s like Caffin :)

Nathan Hays

Locale: San Francisco
Great insights! on 06/20/2012 09:56:38 MDT Print View

This has been an excellent review of the sleeping cover issues. I hadn't been able to piece nearly as clear a picture from other threads. I love this forum! So without proper citations to the many fine contributions, here is what I have distilled:

To this point I have thought a heavier bivy is a replacement for a tent in the rain, perhaps folding the ground cover over my head if needed. As it turns out, I have never been rained on when I've had the bivy as my enclosure, so I've never gained any wisdom on this choice. Now, I don't think the bivy is all that great in direct rain, and adds little in better weather. Waterproof and comfy don't go together in a tube. And once I realized there should always be at least the option of suspending a tarp overhead, the whole notion of a bivy starts losing ground, with the exception of tucking a quilt in tidy.

And we musn't forget the Great Leslie's advice that in winter, one Kwakiutl in a blanket froze while two Kwakiutls were warmer. (Sorry to the kids, you'll have to look that up). The option of cuddling up with your mate, BFF, or an unlucky (lucky?)marmot just doesn't happen with two bivvies.

Starting at the bottom, I think a disposable polycro sheet is a good idea to help keep the 'spensive stuff cleaner. Don't yet know if that will feel good directly under the pad (Klymit Inertia X-Lite + 1/8 evazote) or if I will always want the next layer.

Next is the optional bathtub + net. I think that a tub versus a sheet makes a big difference in a downpour. There always seem to be rivulets running through everything in those conditions. Not much downside to a tub, and just throwing down on top of an unpitched tub/net without a tarp works as well. However, I suspect I will be pitching at least the net w/o tarp on account of the skeeters.

Last comes the rain cover and I agree with those that advocate a larger footprint, at least in capability. I'm also warming to the idea of, as JA put it, "the fun, openness, and ventilation of tarping". That to me is new, like the option of sitting on a veranda in the rain. I've always liked the cosyness of an enclosed tent with a suspended candle during the "transition time", but I've also very much liked sleeping in the open. The versatility of a large tarp makes for some interesting ideas, and adaptability to the chosen campsite's unique attributes.

The downside of a tarp I have mentioned before - is that it can be problematic in high winds. I'm thinking about how the fly on my 3-man standalone is well anchored to the three long poles and I want a design that can achieve the same robustness.

So, having settled on a tarp/tent for two that I will make myself, I'm looking at designs. I've begun sewing the karo baffles on the quilts and I'll be ordering material very shortly for the rest of the sleep system. I also have window polycro on its way along with tyvek coveralls as that looked like a fun project thread.

MYOG thread next.


David Olsen

Locale: Steptoe Butte
bivys, tarps on 06/20/2012 10:43:11 MDT Print View

Winter in Joshua Tree, the Utah Canyonlands, or the Oregon Steens.

Wind blows and is cold.

Stand outside and cook? BRRR. Think of all the extra clothes you would have to carry to
stay warm.

Floor-less shelters let you lounge in your sleeping bag and dine.

But what about the cold air, and the dust or snow blowing under the edges when you sleep?
You know, filling up the hollows of your nobby closed cell foam.

Will a net inner tent help? Some.

A bivy will keep out the drafts and debris at less weight than a full inner tent of
fabric. Keeps you on your pad and misc. gear and clothes close by and out of the weather too.

In dry, windy conditions there is no real condensation issue. Cracked thumbs and sore
nostrils are more likely.

Dave -
(FamilyGuy) - F

Locale: Up there
Re: bivys, tarps on 06/20/2012 10:48:16 MDT Print View

You could use an inner tent with breathable fabric walls to block the wind, dust, etc. Works in all conditions.

David Olsen

Locale: Steptoe Butte
Inner tent on 06/20/2012 11:04:51 MDT Print View

Yes, as I said. Not as light tho. More problematic for dining.

Edited by oware on 06/20/2012 11:09:50 MDT.

Elliott Wolin
(ewolin) - MLife

Locale: Hampton Roads, Virginia
RE: I don't get UL bivy on 06/20/2012 13:17:42 MDT Print View

"Bugs aside, I'd take a full coverage tarp (ie. pyramid) + groundsheet, over a partial coverage tarp (ie. A frame) + bivy. Much nicer in high winds, rain splashing, spindrift snow etc."

An alternative to a full-coverage tarp, aka pyramid, was developed by Ray Jardine (I believe) and is easy to sew (he also sells kits). He calls it a "bat wing," and it's just a small fabric piece that closes the opening at one end of an "A-frame" tarp to block wind and rain. He says he rarely needs to use it as he usually can orient the tarp to avoid wind and rain, but once in a while this is not possible.

It weighs an ounce or two, far less than the extra weight of a pyramid compared to an A-frame tarp. You typically need just one of them to block off the offending end, but one can carry two for extreme conditions. And if there is no wind or rain problem you can leave the tarp ends open and get superior ventilation.

I only had a problem with open-ended tarps once when the wind shifted and it started to drizzle. I had pitched the tarp especially high off some trees, not expecting rain. Since it was our last night I was too lazy to get up and reset the tarp, so my bag got somewhat moist around my shoulders, but I didn't care.

I plan to make a bat-wing for each of my tarps and carry them all the time (I'm terrible about predicting the weather).

Brian Lindahl
(lindahlb) - MLife

Locale: Colorado Rockies
Re: RE: I don't get UL bivy on 06/21/2012 13:12:21 MDT Print View

If you have a large enough tarp, and have an external guyout in the proper location, you can avoid the "bat wing" and just stake the tarp to the ground at the foot end, and guyout the middle of the foot end with a pole, to get some clearance for your feet.

There's a photo of this method on this page somewhere:

Dale Wambaugh
(dwambaugh) - MLife

Locale: Pacific Northwest
Re: I don't get UL bivy on 06/21/2012 13:49:50 MDT Print View

I don't get it either and chose other options.


There are bivvies and there are sleeping bag covers. When I think of a bivy, I think of a tough stand alone shelter that I can simply throw down on the ground (or hang from a rock face) and be protected from wind and precip. Some take a step up and have some poles in the head end, raising the complexity, cost and weight. Even the simple forms are heavier and can be more expensive than a well made tarp or single wall tent. You could juggle apples and oranges all day on bug features. If you want to cook and rest with a bivy open in the rain, then you need to add a small tarp to cover the head end. That doesn't add up for me-- If I have to play with poles, strings and stakes, I might as well have a full shelter. I could make a case for a bivy for something like adventure racing or as part of an SAR kit. Wall climbers have no other options really.

When I think of a sleeping bag cover, I think of a simple bag with a waterproof bottom and a water resistant and breathable top. It performs pretty much like a windshirt for your sleeping bag or quilt, providing another layer to protect from light precip and wind. If you want a very minimal tarp or poncho shelter, they give that extra bit of protection. We can do the bug feature dance on this version too.

I don't think the small tarp/bag cover option adds up well for weight or cost. If you are using a poncho for a tarp, then you get some multiple use "credit" from that combination; otherwise, you can add another 12oz or so for a rain jacket. My alternative is to use an SMD Gatewood Cape that provides good coverage all around, I don't feel the need for a sleeping bag cover and I get that multiple use for rain gear credit in an 11oz package.

I do think that a poncho and something like a space blanket bivy make a good day hiking rain and CYA combination. I'm going to carry rain gear anyway and the space blanket bivy will get me through an unplanned night out. I would be using trekking poles anyway and the only extra weights are the space blanket bivy and a few stakes (or I could cut some).

Dave Heiss

Locale: Pacific Northwest
Bivy vs Tent sleeping on 06/21/2012 17:35:20 MDT Print View

I would bet that many (if not most) bivy users are those lucky people who can simply lay down and fall asleep. Doesn’t really matter where they are - surroundings be damned they lay down and a minute later they are sound asleep. Kinda like those old Hercules movies where he lays down on the ground with a rock for a pillow and is out like a light until morning.

Unfortunately, I am not that kind of sleeper. For me I need some space to move around while I’m unwinding and finding that elusive sweet spot for the transition to sleep, and the tight confines of a bivy are not very helpful to that process. I wonder if the ability to fall asleep quickly might be one of the factors that separates bivy users from tent users…