First MYOG Bivy…

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.

Jesse,

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.

Todd

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

Jesse,
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.
Terry

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!

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.

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).

-Conner

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.

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.

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.
Terry

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
Sil.

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.

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.

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.

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

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

Really nice.

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?

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!

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

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.

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!

So, I know this is over a year old, but honestly, Jesse, your bivy is one of the nicest I've seen and I'm really interested in making one like it, specifically with the hood. I'm having a hard time finding designs that have roomy hoods integrated. If you're still poking around, I'd love to know how you went about it. Thanks and cheers.

Looks more like a body bag to me as most breathable/waterproof material is as breathable as a plastic bag. I'd put it up against my face and see if I could blow through it if not I'd vent it some way. But since this is a year old either he made it ok or it was used as his body bag. Be extremely careful of breath-ability claims.

…

Hey there David, Thanks for the compliment. I am indeed still lurking around on here, just not as frequently over the last several months as I've been a busy guy. The hood is essentially designed the same as the foot box, although wider, to allow some internal storage if needed. I don't recall the exact "depth" of the box-end stitching that I used, but I want to say 9" at the head end. Most hood designs factor in a slim mesh hood, so rather than focusing on that aspect, try to replicate the foot end of most of the bivies out there, but slightly larger.

Galen, I'm aware that even the most breathable fabrics are more than restrictive enough to cause suffocation. I obviously don't have any intent on suffocating, nor do I have the intent on getting caught in a downpour long enough to require a complete seal of the bivy for an extended amount of time… but there are always those chances. The bivy is fairly large in size, and when the tie out cord is used(with the bivy sealed up) there is about 6" or space around my face and shoulders, so there is a bit of air "trapped" in the bivy. In a worse case scenario, I could slide open a portion of the zipper for some fresh air, or open it up a bunch and pitch a tarp/rain jacket over the opening. The chances are that if it's raining heavy enough to require you to close up the bivy completely, you most likely won't be getting much sleep anyways…

Jesse, is the perimeter seam sealed? Sorry if you mentioned that already and I just missed it.