MYOG Bivy

[Spencer A]

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[Spencer A]

This project is my first foray into MYOG.  The plan started out simple enough. I was going to make a basic tarp and envelope-style bivy with cheap materials to hone my sewing skills, then move on to a pack.  Quickly though, my dives into the depths of these forums yielded inspiration for more complex modifications to the bivy design until eventually, this was the result:

 All materials are from RipstopbytheRoll:

– 1.1 oz. (1.3 finished) silpoly XL seconds for the bottom
– 1.0 oz. HyperD for the top
– 0.9 oz. noseeum mesh
– 3/8 in. grosgrain
– 1.5mm drawcord
– Gutermann Mara 70 (used with a size 14 needle I already had)
– #3 zipper with double sided slider
– total cost was $57 which included material for making a tarp

Features:
– 3D half-moon footbox
– 3D triangular headbox for wind shedding
– Long center zip
– 84″ long (~74″ usable due to the triangular head area)
– 70″ wide at the shoulders, tapering to about 50″ in the legs
– footbox circumference is roughly 56″
– grosgrain tieout is attached to HyperD, not mesh
– 5.5 oz.

I based some of the design off of Lance M’s bivy project, particularly the center mesh. Only once I had started sewing did I learn of the new EE Recon bivy which is probably the closest comparison. Construction was very difficult, which is why it took about three weeks. I probably made every newbie sewing error out there, but none of the errors affected its functionality, given that bivies are low-stress items. With the exception of one French seam, all seams were flat felled, though the second stitch sometimes went through three layers of fabric and other times through four depending on where the seam was (I didn’t assemble the bivy in the most logical order so I had to be creative at times to get the fabric into the sewing machine).

Overall, with one major exception, I’m really happy with how it came out. Unfortunately, the excellent weight came at the cost of interior space. Mistakes and large seam allowances shrunk the dimensions. I’m 5’11” 150lbs and with an Exped Airmat Hyperlight (2.5″ inches high, I believe) and a 32 degree mummy bag, the bivy was too tight for me to fit. With a Ridgerest and a 32 degree bag, however, I was able to fit, snugly, but comfortably. I suspect that this bivy would be ideal for someone under 5’10” who uses a CCF pad and a 30+ degree quilt. If anyone is interested, I’ll be posting this on Gear Swap shortly.

Next up is version 2.0 with a 10d top fabric, 0.7 oz. noseeum, and larger dimensions

(I’m also almost finished with a tarp, but it’s pretty boring. Tapered, about 9′ long, 5’8″ wide at head, 4.5′ at foot, no ridgeline because the silpoly is 70″ wide. I might post some pictures tomorrow when it’s finished)

More pictures:

That was my first stitch. Luckily, it’s well hidden within the seam :)

 

[Basalt Gear]

Spencer, this is great! Thank you for posting this. I’m beginning a bit behind you in both sewing skills and development of design, but like you, I recently saw and got interested in the EE Recon bivy. When the time comes please post any materials and pattern info you are willing to share. I’m definitely going to adopting most of your design based on what you have posted here.  Keith

[Andrea C]

I’m not a great fan of Bivy bags, but I’ve some good Silnylon that I can make a use of.
This post was a good inspiration, some good work done up there :-)

[Spencer A]

I finished my second bivy. This one has a similar design to the first but several small changes make it far more functional. I’m very happy with the finished product.

Pictures are here: http://imgur.com/a/u6WHv

Materials are the same as the first, with the exception of using Membrane 10 instead of HyperD and 0.7 oz. mesh instead of 0.9 oz. Unfortunately, I don’t have access to a scale until next week, but I would guess that it weighs 5.5-5.8 oz.

Realizing the inefficiency of a triangular-shaped head box, I went with a curved design on this one as well as a higher cone, about 15″. The effect is that the whole length of the bivy is usable and more spacious. The other major change is that the dimensions are larger. 85″ long, 62″ girth at the narrowest point near the feet, increasing to about 65″ where the large mesh area begins. At its widest point, where the headbox begins, the girth is 79″. The half-moon footbox is about 58″ in girth. I don’t have my gear with me at the moment, but it should fit similarly to a Borah Gear bivy with more space towards the shoulders. Other small changes include small tieout loops, one at the head and two at the feet, to stake out the bivy to stop it from sliding and more substantial zipper stops made out of small patches of fabric.

My sewing skills are by no means professional level, but I think they are functional enough that I’m ready to tackle a backpack.

 

[Jerry Adams]

Nice job

I like how you’re proud of the non functional affecting screw-ups : )

I’m working on a hybrid bivy/quilt.  I think it’s been 6 months so far.  I have to buckle down and finish that some time.  I have a perfectly good one already, the main thing is to increase the loft a little, add more down, to make it a little warmer.  Maybe I’ll finish it by next winter

[Larin M]

Have you posted the first version on gear swap already… I might be interested.

[Spencer A]

Larin, I sent you a PM

[Spencer A]

Here’s the final bivy of the summer :   Pictures

• 0.93 Membrane silpoly bathtub floor, NS50 0.5 oz. mesh top
• Total weight: 4.2 oz.
• 74″ long, 28″ tapering to 21″ wide

The 0.5oz. mesh was a little hard to work with – so fine that chalk marks barely showed up and so stretchy that it was difficult to cut – but I would recommend it nonetheless. The strength to weight is incredible and, for what it’s worth, I love the way it billows in the wind.

[Lester Moore]

Spencer – the simplicity, function and quality of your bivys (and their low weight) are inspiring me to buy a sewing machine! I’ve been itching to build a sub 7 ounce inner net tent for my Deschutes CF tarp out of the same bathtub and netting materials that you’re using. It’s helpful to hear your MYOG experience with the NS50 netting – that’s helpful info for net tent designing purposes.

[Spencer A]

Go for it! A bivy or net tent is a great first project because you have to do long flat felled seams with slippery fabrics. Bivys are also more forgiving than most other projects because there’s little stress on any one component. And I enjoy the simple trig and geometry that goes into making 3d head boxes; besides, its been helpful for planning my prototype shelter that has a lot of funky angles.

Let me know if you have any questions about the materials or design. I’m happy to help

[Adam Kilpatrick]

Hi Spencer. What do you think so far of the 0.93 Membrane silpoly as a floor material?

Cheers

[Spencer A]

Hey,

That was custom bivy I made for someone else, so I don’t have it anymore. I haven’t heard any feedback on durability yet, but I’ll message him and let you know. My only criticism while working with the Membrane Silpoly was that it is extremely slippery, more so than the PU4000 version and 1.1 silpoly. I’ll be making bug bivys out of cuben and 7D silnylon two weeks from now, so I’m excited to see how those fabrics compare.

[Adam Kilpatrick]

Cool, which 7D silnylon are you going to use?

Definitely keen to know how you go :-)

[Spencer A]

I’ll be using Rockywoods 0.7 oz silnylon  (I think that’s the only one available to MYOGers). I can post pics when it’s finished

[Spencer A]

I ended up finishing two bug bivys weighing 3.30 and 3.59 oz. out of the 7d Silnylon. Can’t comment on how it will hold up to backcountry use, but I can say that I love the feel. Once a tear is started, the ripstop makes it more difficult to continue tearing than Membrane silpoly.

Pics of the first (it was a custom order that’s quite a bit narrower which explains the lower weight): https://imgur.com/a/7FAwU
Pics of the second: https://imgur.com/a/1jaOj – this one is for sale on the gear swap if anyone is interested

[Spencer A]

Just finished up the lightest bivy yet – kind of a culmination of my year-long search for the lightest bivy possible. I used 0.51 Cuben and 0.5 Mesh, resulting in a 3.14 oz bug bivy. Pictures here: https://imgur.com/a/563LhWW

72″ long, 27 narrowing to 20″ wide, 2.25″ bathtub walls sealed with 3m transfer tape (big thank you to Ryan Smith for the tape!). Definitely my most frustrating project yet – I recently got a Juki DDL 8700 and it frequently sucked up or twisted and ripped the mesh and cuben, especially in reverse, leading me to switch back to my 1940s Singer halfway through the project. In hindsight I should have taken more time to become accustomed to the Juki before working on this bivy. I was using Gutermann Tera 80 with an 11 needle and experimented with using both regular and zipper feet for reference. If anyone has tips for using industrial machines on SUL fabrics, I would be grateful.

I’ll be making gear all summer (website and Instagram will be up within the next week, name: Skylight Gear), so if anyone is interested in a custom bivy or anything else, hit me up! Also wanted to say that I’m extremely thankful to everyone on the forums. I wouldn’t have been able to get to where I am without the wealth of knowledge posted here.

 

[Jerry Adams]

3.14 ounces – nice

good looking pictures, well done

[Ryan Smith]

Looks great Spencer!

Ryan

[Hoosier T]

I also switched to a DDL-8700 over the winter.  I sewed a new down TQ and it was an adventure getting the machine to play nicely with the light materials. I basically went as small as possible. I used Mara 150 and a 60/8 needle and lowered the thread tension (top and bottom) A LOT and it finally worked better but it did require me to re-time the machine. However, reverse is still a PITA as it will induce some puckering but it at least stopped sucking the fabric into the plate. I would also love to hear if anyone has overcome this with light industrial machines such as ours…

[Hoosier T]

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[Ryan Smith]

Good looking quilt, Hoosier!
<p style=”text-align: left;”>Ryan</p>

[William N]

Looks terrific. I love my REI Minimalist Bivy for its simplicity. You have a few outstanding features that I know are functional and useful. The centerline zipper: bivy’s can get stuffy. This is exactly where I’d want an opening to let in/out some air. I’d want two zippers coming from each direction. The lift off the head–great. Grosgrain stake loops: good. My bivy tends to want to slide downhill, even a slight slope. The long mesh vent…. I’m not so sure about. I don’t get condensation inside my bivy because there’s no space for this to happen. Warm weather? probably a good thing.  I find that I use my bivy even in summer. It’s a handy way to keep my air mattress and sleeping bag together. I run a string from the sides of my air-pillow around my air mattress.  What’s needed next is a way to tie the mattress to the bivy.

You’ve made a terrific bivy avoiding all the excess that makes some bivys weigh as much as tents.

[Author]

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