Montbell UL Bivy First Impressions

[Christopher Plesko]

Got the Montbell Bivy RyanF suggested to me this Friday when up at the flagship store with some family. Going to do some modifications to it but I’m hoping it will work as my tarpless shelter. Of course I couldn’t resist giving it a test run against my Adventure medical thermolite bivy sack. $20 vs $110 shouldn’t be a competition but we all know that price does not equal performance. I’ve certainly been happen enough with the emergency bivy to keep it around and use it a few times when I don’t feel like bringing my 4lbs+ tent.

I don’t own any summer bags yet, just a Marmot Sawtooth 15 degree down bag. In the summer it’s HOT and the other night was no exception. I usually sweat in the bag, causing enough condensation to pool and wet the sleeping bag’s shell due to the bivy not breathing. Much to my happiness I woke up dry in the Montbell bivy. Conditions were the same as normal: warm ambient temps, low humidity, face breathing outside the bivy, sleeping bag half unziped, and sleeping pad inside the bivy and outside the bag. Obviously one trial does not equal sucess but it’s a promising start. Sleeping pad was also different than normal, now a cut down (19″ tapering to 14″ and 26″ long) blue pad vs full length. Bag showed no cuts or scratches after the night. Aside from a little dirt it still looked new even with no ground cloth.
What we ULers all care about is weight right? And size matters too. Well I don’t have an actual weight to list yet as I just use the scales at work and haven’t taken it in there. Claimed weight is 6.3oz (178.6g) and I expect it to be close. Regular bag size is small. I’m 5’11” and 155lbs. The bag is *just* big enough for me lengthwise when all tightened up. If you are any bigger than me or want to store any significant gear in the bivy you are going to need the wide and long model. Packed size is tiny. My wife and mom remarked I’d never get the bivy back it’s tiny stuff sack but it went in easily. For day trips I’ll carry the sack stuffed, otherwise I’ll pack my sleeping bag into the bivy for another line of defense. It packs to about half the size of the thermolite bivy.

Overall I’m pleased with the products claims and initial results. It’s very light and breathable while keeping me and my sleeping bag protected. After I finish my modifications I’ll do a more extensive rain/hose test of the waterproofness.

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Breeze Dry-Tec U.L. Sleeping Bag Cover-
• Fully seam taped
• 2-layer Breeze Dry-Tec™ construction
• Air-permeable water-proof breathable material
• 12-denier micro rip-stop nylon shell
• Max Dimension 88.6″ x 33.1″
• Draw cord around the face
[Weight] 6.3 oz.
[Stuffed Size] 3.5″ x 2″ x 7″

[John Chan]

You will be happy with your new investment. I was in Killarney park this April with a friend who used my Montbell UL bivy + Nunatak Arc Alpinist. Some nights were pretty cold and he sweats quite a bit but the bag never saturated at night with him in it (and the bivy over everything). In fact, in the morning we could see where the bivy had vented moisture which subsequently condensed and froze on the wall of my Hex 3 (all along his whole body length).

[Peter Fontana]

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[Christopher Plesko]

We’ll see what Mr.Hose thinks about the waterproofness. I’ll try to get out in rain too but that’s going to be difficult without lightning/thunder this time of year.

[Christopher Plesko]

Bivy as sold: 178.5grams (6.29oz)
Stuff sack as sold: 8.03grams (.28oz)

Love when manufactures are accurate about their weights!

[John Carter]

Curious what types of mods you intend to make. I’m looking closely at modifying this bivy as well, but can’t work out how how to waterproof the new seams. I’m not sure Silicon sealer will adhere.

I suppose I could just lay my wp/b jacket on top of the opening if I had to, tucking it under me so it doesn’t blow away.

[Christopher Plesko]

Planning to sew in some zip up bugnetting over the face opening and perhaps a small silnylon flap over the face opening that could be tied off to my bike or a tree to block wind and rain and also keep it off my face. Probably replace the cord with something lighter also.

If I get really ambitious I will sew a Cuben bottom to it but that depends on if my custom bivy/sleeping bag moves forward instead as well as how WP/B this fabric turns out to be long term.

For the first trips I will just lay my rain jacket over the opening to see how that works before I do my mods. Hoping to try it out in the mountains this weekend!

[JW]

Chris, I’m looking at this bivy now and wondering about three things:

1. How snug around your face does the drawstring close? Can you easily get a nose size hole?

2. What is your experience on breathability since you’ve had it?

3. Is the bottom tough enough for use without a groundcloth?

Thanks, Jhaura

[Christopher Plesko]

The drawstring closes really tight, easily a mouth sized opening. I haven’t tried to go tighter since it was hard enough to find a hole that small in the dark :) I can try tonight if it’s important.

Breathability has been wonderful. With breathing into the open air I have had zero condensation problems at all. With my old bivy (emergency one) I would get a wet footbox and damp bag even on dry nights. When I cocooned totally inside it one cold and wet night my pullover (all I had on) got a tiny bit damp but not very much. No noticable moisture in the bag when I woke up. This is in Colorado at 5k to 11k elevation so far.

So far I have had no punctures, rips or tears and I have never used a ground cloth with it. I assume that doing such will shorten it’s lifespan somewhat over having a groundcloth but I’m willing to accept that. After 4 or 5 nights out now it looks like new on the outside other than maybe a little dirt spot. I turned it inside out after the last trip and didn’t notice any weird problems inside either.

Overall I’m quite pleased with it, especially for the price. It *just* fits me at 5’11” so if you’re any taller I’d get the large version. The bug netting and rain flap have proven unnecessary after I’ve had it in a couple rains. I still wish for a cuben bottom but I may leave this one as is and make that a separate side project with another WP/B material.

Hope that answers your questions and it works well for you.

[EndoftheTrail]

Methinks Christopher is fast turning into a MontBell gear whore… :)

Kidding aside, I too am a big fan of MB gear.

[David Ure]

NM

[Christopher Plesko]

Montbell does make some nice stuff and surprisingly *some* of it is reasonably priced. I like that a lot of it fits trim too as I’m skinny. :)

I can’t say how much it would increase warmth of a summer bag. It’s definitely warmer inside the bivy and even warmer with it closed up tight. I use it more importantly for shelter from rain etc as I do not bring a tarp along at all. It’s my sole shelter.

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