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First MYOG Bivy...
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Jesse Reeves
(JesseR.) - M

Locale: Reno, NV
First MYOG Bivy... on 01/27/2012 19:51:12 MST Print View

Well I finally made the plunge. I spent the last few weeks kicking around ideas in my head, and browsing on here for some inspiration and . I scored 3 yards of eVent fabric in the Gear Swap section and I knew exactly where I'd put it to use. I'm racing in the Colorado Trail Race this year, and wanted a shelter with a compromise of simplicity, waterproofness, durability, and weight. I wanted to avoid having to set up a tarp/tent, so this meant that the bivy I used needed to be completely waterproof, not just water resistant. I was willing to sacrifice a few ounce of extra weight, even over a ultra-light bivy and tarp combo, as this would make for an easier setup after 14 hours straight on the bike. I also made it a little larger than it needed to be, this gives me room for my Neoair pad, some extra room to store clothing if it gets nasty out, and also just for some wiggle room. What's not shown is the nano-see-umm mesh panel that will velcro into the opening. I'm waiting on the sticky back velcro to finish this part up, and I'll update it when I get that in. I'm hoping to keep that part just under 2 oz, putting the whole setup at 17oz...

Top fabric is eVent, bottom is 1.9oz PU Coated Nylon(again, a sacrifice of weight for strength). It has tie out loops on both the body portion, and hood portion of the zipper, which is a YKK #3 Water Resistant. Also pretty proud of the matching stuff sack I made for it... hahaha

Edited by JesseR. on 01/27/2012 19:54:33 MST.

Nancy Twilley

Locale: STL
awesome! on 01/27/2012 19:59:30 MST Print View

That bivy looks truly awesome! I've got some eVent coming my way from the gear swap, and hope my new bivy turns out as well as yours did. Why did you choose PU coated nylon over 1.9 oz silnylon, if I may ask? Are you doing a very minimal mesh panel, or something larger?

Also, sweet stuff sack.

todd h
(funnymoney) - MLife

Locale: SE
Re: First MYOG Bivy... on 01/27/2012 20:06:08 MST Print View


This is great, and I especially like how you customized it to be what YOU want. And that stuff sack is way cool!!

Can't wait to see the mesh panel.


Rob Hubbard
(robwa10) - F

Locale: England
Closing up on 01/28/2012 02:56:43 MST Print View

Does the top close up to keep water out? If so could you post a pic and a lil blurb about how it works?

Terry Trimble
(socal-nomad) - F

Locale: North San Diego county
First MYOG Bivy on 01/28/2012 10:02:02 MST Print View

Very cool bivy and clean sewing. I love my bivy just throw it on the ground and sleep. I made a ground cloth out of 1.9 0z coated ripstop has 18" pocket to slip my bivy foot end in to and a 18 inches wider on each side of the head end of the bivy to set my equipment on dress or put my shoes in the morning.
It has 3 stake out points one in the center at the foot end one at each corner at the head end,It rolls up in nice tight 1 inch roll it keep my bivy from developing unwanted puncture hole.

Jesse Reeves
(JesseR.) - M

Locale: Reno, NV
Replies... on 01/28/2012 18:14:44 MST Print View

I chose the coated 1.9 after reading about the differences between it and silnylon. It seems the 1.9 is very waterproof, and pretty durable compared to some of the other lightweight materials. The mesh panel will be kind of "eyeball" shaped. 36" wide and 12" wide at the widest point, it too will have a small tie-out loop in the middle.

Rob, the whole thing zips closed with a 36" wide water-resistant zipper. I'll snap some pictures next time I get it all rolled out.

I've thought about making a groundsheet for more casual trips. The extra width for gear and dressing is a great idea, as is the footbox concept.

I'll get it finished and update this thread when I do! Thanks for the feedback guys!

Nancy Twilley

Locale: STL
1.9 oz pu vs. 1.9 oz sil? on 01/29/2012 09:46:08 MST Print View

Hi Jesse: (or anybody else with insight)

But why 1.9 oz pu coated over 1.9 oz sil coated? It's the same weight of material, so they're equally durable I suppose, but I was under the impression that the sil would be more waterproof than the pu coated. I'm going to order floor material for my (hopefully equally awesome) bivy soon.

Conner D
(cdipaolo) - F

Locale: SoCal
Re: 1.9 oz pu vs. 1.9 oz sil? on 01/29/2012 11:46:04 MST Print View

I have heard that the PU coating is way more waterproof. I think it weighs more, too. Also, it will not be as slippery for sure so as a bivy floor, that would be an advantage. That said, the sil-nylon has a higher tensile strength because it can stretch. It is basically a choice between durability and waterproofness. Given that he is trying to do the Colorado Trail (right? I'm not looking at the OP) where the rain is apparently really horrendous at times, the PU coating is probably a safer choice for the bottom (not necessarily safer, just better for the conditions).


EDIT: His setup is still under 20 oz for his whole shelter, so that is still lighter than many other lightweight tents and large tarp+bivy setups. Also keep in mind that he is biking, and not backpacking (right?), so a sub 20 oz shelter would seem even lighter probably.

Edited by cdipaolo on 01/29/2012 11:48:58 MST.

Nancy Twilley

Locale: STL
good to know on 01/29/2012 12:22:48 MST Print View

great -- I did not know the pu coating was more waterproof than the sil would be for a floor-type application. Perhaps I'll use it then for my bivy as well.

Terry Trimble
(socal-nomad) - F

Locale: North San Diego county
The problem with silicone as floor on 01/29/2012 12:36:20 MST Print View

The problem with silnylon as floor it prone to leak under pressure because of unseen pin holes during manufacture. Will leak if you have a 120 to 150 lbs person laying on top of it silnylon and it rains quite a bit you have combination of body weight pressure and water and the unseen pinhole will leak.

That why a heavily coated urethane coating is better because you can see if their are pin holes during manufacture of the fabric.

Todd Bibler of Bibler tents fame who made expedition tents believed and proved that using ripstop nylon for tent floors for prolong use in tents at Everest other raining conditions. That the weight of people and equipment would wear off the urethane coating faster at the uneven surface of the ripstop threads of fabric .
So he used a heavily coated Taffeta or pack cloth in his tents instead because it has a smooth surface instead of uneven surface like ripstop.

In tent or bivy floors urethanes is better choice than silnylon even though it weighs more.

David Olsen

Locale: Steptoe Butte
apples and oranges on 01/29/2012 15:46:55 MST Print View

When comparing coatings, one needs to know the weight of the coating, the kind of coating
and the method used to apply the coating to the fabric.

Water based PU will dissolve and peel off much more quickly than solvent based PU or

coatings of .25 oz per yard squared sil and PU are comparable in waterproofness under pressure but the sil will have a higher tear strength.

1 oz PU coating will be much more waterproof than .25 oz sil, but you will have a
3/4 oz per square yard additional weight penalty, a lower tear strength and likely
have to put it on a 1.9 oz or heavier fabric. Total weight would be 2.9 oz per sq. yard.

In the end you could use two layers of 1.1 ox silnylon and still weigh less than a single
layer of 1.9 oz PU.

Or 1.9 oz with .5 sil would be lighter, stronger and as waterproof.

Or use 1.1 oz sil and add a waterproof plastic ground sheet or a closed cell foam pad.

Jesse Reeves
(JesseR.) - M

Locale: Reno, NV
Coated vs. Silnylon on 01/30/2012 12:58:40 MST Print View

It seems like the guys have chimed in with a ton of good information, and it seems to be pretty consistent with what I found when doing my research on material choice. The fabric is 1.9oz Ripstop, that is then coated with .75oz per square yard, according to Rockywoods. I ordered some 1.1oz Silnylon at the same time(from Quest) and compared the two side by side and decided that the weight penalty was worth it. I weighed them both, and figured out exactly how many square inches would be used in the bivy. The bottom fabric came out to 5.89oz of 1.9Coated, versus 3.28oz of 1.1Silnylon... It would have been easy weight to save, but for this specific application, I was fine with a little heavier. I'm planning on making a lighter Momentum topped bivy with the 1.1 for the floor. Shooting for 7oz or so, which will provide me with a great lightweight summer bivy.

Jesse Reeves
(JesseR.) - M

Locale: Reno, NV
Mesh Window on 02/07/2012 20:49:29 MST Print View

I finally finished her up a few days ago, and just now got all the pictures loaded up and hosted... Here she is. It came out better than I truly was hoping for. I wanted something removable, as I don't often need the bug netting on my trips, but wanted the option. The window insert is simple, and very effective. And the best part, it's only 1oz... It rolls up to about the size of a AA battery, so it's compact and easy to store in the bottom of the stuff sack for use if needed. I put small grossgrain loops at each end to make removal easy from the inside. To crawl in and out it's as simple as undoing one edge of the velcro and wiggling your way out. It puts my total bivy weight with stuff sack, and 3' of elastic tie-out cord at 16.05oz. All in all, I'm very pleased with my first attempt! Can't wait to get out and get it dirty!
Insert laid out:

Laid over the bivy for size refernce:

Close up of the velcro that is sewn just inside the zipper portion of the bivy. This remains on the bivy at all times, and is then mated with the velcro strip that borders the entire mesh window.

Another close up. This one showing how nicely the velcro seals at the edge of the border. It'll definitely keep out the creepy crawlies...

This is just demonstrating the location of the upper tie-out point on the hood portion. Gives me tons of ventilation and great visibility.

And this is the same as the above one, but showing it with the bivy completely water-tight.

Edited by JesseR. on 02/07/2012 20:50:20 MST.

Nancy Twilley

Locale: STL
thanks! on 02/07/2012 20:55:05 MST Print View

sweet, thanks for the extra pics! Looks very professional.

Ken T.
(kthompson) - MLife

Locale: All up in there
Re: First MYOG Bivy... on 02/07/2012 22:20:26 MST Print View

Beautiful job all around. Now get out and use it!

Really nice.

Ken Smith
(KenSmithMT) - F
Breathing room on 02/20/2012 00:19:36 MST Print View

Looks great. I'm about to start my own first bivy project. One thing I noticed about your design is that it appears that when you have it all zipped up for rain, there is no opening left for ventilation....for air to breath. Am I missing something?

Travis Leanna
(T.L.) - MLife

Locale: Wisconsin
Re: Breathing room on 02/20/2012 00:29:22 MST Print View

Ken, I think that's just the nature of the beast when you're dealing with bivys. But, he's got an eVent top which will help more than any other fabric.

Fantastic job on your project!

Bruce Thibeault
(brucetbo) - M

Locale: New England
Re: Mesh Window on 02/20/2012 10:24:32 MST Print View

Do you worry that the velcro being inside the mesh window opening may catch clothing when the mesh window isnt being used?

peter vacco

Locale: no. california
Re: First MYOG Bivy... on 02/20/2012 12:46:00 MST Print View

jesse : i have no idea if you've actually installed the sticky back velcro as yet, but, if possible, it is a good idea to pre-test a bit of that stuff first, as it's sticky glue can sometimes really muck up inside you machine. sometimes yes, sometimes no.. it seems to be a heat issue.
and ... sweet looking bivy.

good luck in the race.
peter v.

Jesse Reeves
(JesseR.) - M

Locale: Reno, NV
Replies: on 02/22/2012 19:40:28 MST Print View

Ken, I built this bivy to be completely waterproof in a downpour, so if I left a vent opening, it would be a point of entry for water. I plan on using the bivy with the zipper opened for most circumstances, but I have the ability to zip it up and stay dry given the breathability of the eVent fabric, as mentioned by Travis.

Bruce, when I put the velcro strip in, I made sure that the portion attached to the bivy was the "loop" side of the velcro, and therefore the "hook" portion is attached to the mesh insert. Neither portion is very abrasive, especially the portion that will be against my bag, clothing, etc...

Peter, Velcro is in. I used the sticky back, which made the testing of it easy. I then went over all of the velcro with a stitch to keep it from going anywhere. No problems with sticky stuff or anything.

Still haven't gotten out to use it yet... Hoping this spring like weather holds up for a week or so longer and we'll give it a test run!