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Reviews > Shelters > Tarps and Bivys > Big Agnes Three Wire Bivy > Test Report by Chuck Carnes

Three Wire Bivy Sack

Initial Report: March 11, 2008
Field Report: May 20, 2008
Long Term Report: July 20, 2008

Name: Chuck Carnes

Age: 38
Gender: Male
Height: 6 ft. 0 in (1.83 m)
Weight: 175 lb (79 kg)
E-mail address: ctcarnes1(at)yahoo(dot)com
City, State, Country: Greenville, South Carolina USA

I love the outdoors – I’ve spent time camping in the outdoors since I was born, and have been actively hiking and backpacking since then. I consider myself a lightweight hiker, usually carrying 20 – 30 pounds (11-13 kg) for hikes up to a week in length. I hike at an easy pace, averaging 2 mph (3 kph). I am a one-man tent camper for now. I like to carry a single trekking pole when I hike to help relieve stress to my legs and knees. I like to get out on the trail as often as I can.

Big Agnes

Model: Three Wire Bivy
Zipper Location: Right Side
Year of manufacture: 2008

Listed Trail Weight:  28.5 oz (808 g)
(poles and bivy)
Listed Packed Weight:  32.0 oz (907 g)
(everything - poles, stakes, bivy, stuff sacks and instructions)

Actual Trail Weight: 
29.0 oz (822 g)
(poles and bivy)
    Poles: 5.0 oz (142g)
    Bivy: 24.0 oz (680 g)
Actual Packed Weight:  32.5 oz (921 g)
(everything - poles, stakes, bivy, stuff sacks and instructions)  
    Poles: 5.0 oz (142 g)
    Bivy: 24.0 oz (680 g)
    Stakes: 2.5 oz (71 g)
    Stuff Sacks (all 3): 1.0 oz (29 g)

Packed Sack Size: 5 in x 17 in (12 cm x 43 cm) [with poles]
MSRP: $299.95 USD


The Big Agnes Three Wire Bivy is made to get the user out of the elements of the weather but still lighter than a tent. The top portion of the Three Wire Bivy is made of eVent fabric which allows the bivy to breathe and moisture to escape but also waterproof to keep the user dry while inside the bivy. The bottom is a durable Cordura rip-stop fabric to hold up to the harsh elements of the ground to prevent tears and scuffs. The two poles are made of DAC Featherlite NSL aluminum material that gives strength and support to the bivy with a lightweight swivel hub. The bivy has six stake out points; two at the foot, two above the head and one on each side near the entrance. It comes with six aluminum X-peg stakes in their own stuff sack. All seams are taped and can have extra tape or 'seam seal' added to them for extra protection.

eVent waterproof fabric is the top layer of the Big Agnes 3 Wire Bivy sack. This fabric is designed to 'let the sweat out'. According to the eVent hang tag that came with the bivy, 'We all sweat. A lot. Humans simply walking  produce 0.25 to 0.5 litres of sweat per hour, and up to 1.5 liters during strenuous activity. eVent fabrics allow sweat to quickly evaporate to the outside, keeping you dry on the inside.'
(Image, courtesy of eVent)

CorduraCordura fabric is the bottom layer of the Big Agnes 3 Wire Bivy sack. This fabric is designed to withstand tears and abrasions after all of the rough wear that the fabric has in contact with the ground. According to Cordura, this fabric is '10x more durable than cotton duck, 3x more durable than standard polyester and 2x more durable than standard nylon.'
(Image, courtesy of Cordura)

I N I T I A L    R E P O R T
March 11, 2008

The Big Agnes Three Wire Bivy arrived in its own stuff sack with the poles and stakes rolled up inside the bivy. I am new to using a bivy as a shelter and have always been skeptical of their protection from the elements. But, I am trying to cut down on the weight that I carry and the 'shelter' is one area that will help me do that, so I decided to actually try it out. At first I realized that I did not see any instructions so I lay out the bivy on the floor to try and figure it out on my own. I took the poles from their own stuff sack and put them together. I noticed that the two sectional poles were connected by a small plastic swivel in the middle. This allows the poles to stay connected together but to also form a cross. I started looking for pockets, grommets or holes to put the ends of the poles into. The two stake out points on either side of the entrance, has a brass grommet made into the web strap. I noticed that inside, at the head of the bivy, is a small pocket that appears to be the placement of one end of the pole. And then, looking at the 'visor' or 'beak', there is a small pocket sewn underneath the edge for the other end of the pole. See below for an illustration in getting the bivy ready for use.

Remove bivy from stuff sack

Plastic Hub
Connect poles together and swivel at plastic hub to form a cross

Pole Hole
Insert appropriate pole through hole

Pole Pocket
Insert the end into the 'pole pocket' at head of bivy

Insert opposing end of pole into the beak 'pole pocket'

Full Set Up
Insert adjacent pole ends into the respective brass grommets on side.
Stake out the six points and set up is complete!

After getting it together I unzipped the top layer and the netting all the way to be able to get into the bivy. I did not have a sleeping bag in the bivy but wanted to see how much room I had to move around. I am used to sleeping in at least a one man shelter so I wasn't sure how much room I would have in a shelter that is not much bigger than a sleeping bag. After getting in I was surprised at how much room I have at the head of the bivy. Vertically, I was able to sit up on my elbows and barely touch the fabric. Horizontally, with the two stake out points at the head, it gave me a squared off area inside to place small items in the corner or just above my head such as personal items, a light, my watch, a book or other small gear.

Inside bivy at head

After turning over onto my back I see that I have a good bit of room from my face to the fabric and cross poles. The poles in this cross position gives plenty of head room so that it doesn't feel so claustrophobic. A great feature of the bivy is the small 'visor' or 'beak' that sticks out over the body of the bivy. It's only about 13 in (33 cm) long but this gives the user the opportunity to leave open the mesh and/or the top fabric, for extra ventilation during bad weather or for star gazing. The mesh and fabric zippers run across the top and down the right side of the bivy down to about half way. Both the mesh and fabric zippers have long, light reflective zipper pulls which make it easier to find and hold on to. I am curious to see how much room I have inside once I put in a sleeping bag and pad.

As a first time bivy user, I think this is going to be a great shelter. My only concern is that if I am caught in bad weather or just a simple rain storm, how effective can I set up the bivy and keep from the inside of the bivy getting wet? Unlike a tent where the user can take the gear inside and set up sleeping bag and pad and be out of the elements, using a bivy, everything has to be set up outside and then inserted into the bivy. Also, the pack and gear has to stay outside where a pack cover will be needed.

All-in-all I think I am going to enjoy this bivy and testing it. I think I will come across some interesting ways and uses in finding my campsite location and figuring out the best way to keep my gear dry if caught in a storm. I am sure I will find some 'Likes' and 'Dis-Likes' but for now, this is what I have come up with.

That's Cool:
* Very light
* Very small packed size
* Plenty of head room
* eVent Fabric Top

That sucks:
* Bivy stuff sack seems too small
* Inside of bivy could possibly get wet during set up if in a storm or rain shower

F I E L D    R E P O R T
May 20, 2008

The Big Agnes 3 Wire Bivy has gone on a two night trip with me to
Sassafras Mountain where I hiked the Foothills Trail from Table Rock to Sassafras Mountain. This was an 8 mile (14 km) trail over a few hill tops and along some ridges. The weather was fairly nice. The temperatures ranged from 60 F to 70 F (15 C to 21 C) during the day and 35 F to 40 F (1 C to 4 C) at night. We had a few sprinkles of rain here and there but nothing major to have to get out any rain gear.

The bivy packed very easily in my backpack and it was placed so that I could get to it quickly if I had to. Once arriving at camp I retrieved the bivy from the pack and pulled it out of the stuff sack. I set it up as I did the first time except I shaved off about 10 seconds since I knew the process. So, I had it up and staked in just under a minute. Luckily it wasn't raining so I could take my time putting my bag and pad into the bivy. I took the pad from the stuff sack and inflated it and inserted it into my Big Agnes bag. This was a little awkward because normally I am inside a tent when I do this but this time it was done outside of the bivy and I feed the bag and pad into the bivy from the opening. Almost like putting them into another sleeping bag. None the less, they fit fine in the bivy and I had a good area at the head of the bivy for small gear. I zipped up the bivy so that no critters would make their way into my bag and sat around until bedtime.

It was sort of weird for me being used to a tent, to just unzip the bivy and bag and not having a good bit of shelter above me like being in a tent, also the privacy aspect of it is gone; but it will take some getting used to. 
I removed my clothes except for an underlayer and got in. I kept all of my gear outside of the bivy, covered under a pack cover. After getting in and getting settled it was actually pretty neat. I left the beak vent open throughout the night and was able to get some fresh air. I actually slept very well and did not feel claustrophobic at all; which is something I was concerned about. The following morning the outside of the bivy was damp with dew but the inside was perfectly dry. It was very easy to just remove my bag and pad, remove the stakes and shake it a bit to knock off the dew, stuff it in its sack and pack it away. The bivy is still a little tight trying to stuff back into its stuff sack. I think it could have been made just a little bit bigger.

The following night and morning proved to be the same set up and take down as the previous night. I tried something a little different though in the set-up. I placed the bag and pad in the bivy before I place the poles into position. This made it a bit easier to slide the bag and pad in without trying to work around the poles that are in place. After putting the bag and pad in I placed the poles in there position and all was well.

This is still very new to me but so far I really like the bivy. I'm still not comfortable having to leave all of my stuff outside but, I'll get used to it.

That's Cool:
* Different ways to set-up (as mentioned above)
* Easy to Pack-n-Go

That sucks:
* Bivy stuff sack seems even smaller once the bivy has been out and slept in

L O N G   T E R M    R E P O R T
July 20, 2008

Since my Field Report, I have taken the bivy on several 1 night trips. On my over night trips I went to several different locations that are close to my house and easy to get to. The elevation ranged from 1,500 - 3,000 ft (457 - 914 m) and the temperatures ranged from 75 F – 90 F (24 C - 32 C) during the day and 70 F – 80 F (21 C - 26 C) at night. I did not encounter any rain during these trips.

There is not much more that I can say different about the bivy that I haven't already said in the field report. It was easier during the spring and summer to carry the bivy since it was lightweight and very minimal. Also I did not have to worry about dew falling on it during the night but I did have to worry about unexpected thunder showers that typically happen in the southeast during the summer. One of my concerns during the hot and humid season was that the bivy would hold a lot of heat in and would not vent out during the night. My strategy for this was waiting until the sun went down to set up the bivy. This worked well and it kept the fabric from getting hot and heating up the inside of the bivy. My next concern was how much ventilation was I going to get during the night. With my body heat and the temperature of the air only getting to around 70 F (21 C) I was concerned that my body heat would not escape and the bivy would fell like a sauna inside. The results were the lower portion of my body stayed somewhat sticky and sweaty and did not get any circulation but the upper portion of my body got a little bit of air and was bareable through the night.

The mosquitoes are bad during this time of year so to open the bivy fully was not  an option. My sleeping system was a blow up mattress and a 40 F (4 C) sleeping bag. I never slept in the bag, only on top of it. With this thickness of pad and bag, my legs were constantly rubbing the top fabric of the bivy. Had the fabric been away from my skin, the fabric may have had the chance to vent the heat and circulate better. I don't blame the design of the bivy or the fabric. I believe that it would work better and be more efficient in cooler to colder weather as one could take full advantage of it's protection and ventilation. I feel that it is not suitable for hot and /or humid weather unless it is needed in an emergency. 

The Big Agnes 3 Wire Bivy, I feel, has been a great shelter for me during the colder months as it is very minimal and lightweight to carry when most shelters take up a lot of room in a pack. Case in point, it works well for the summer months as well but for me and my area, only as an emergency shelter. The bivy is light and small enough to pack in an overnight pack. The bivy itself has been very durable from getting in and out and all of the zippers and poles are still in working order. 

That's Cool:
* Great emergency shelter for hotter months
* Compacts very small

That sucks:
* For me, it does not vent well enough for hotter months

This concludes this series.
Thank you Big Agnes and for this opportunity.

Read more reviews of Big Agnes gear
Read more gear reviews by Chuck Carnes

Reviews > Shelters > Tarps and Bivys > Big Agnes Three Wire Bivy > Test Report by Chuck Carnes

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