I am in the process of making my own bivy sac. I recently ordered 2.4oz/yd epic fabric, and 1.4 oz/yd ripstop nylyon for the floor. I want to know if the 2.4 oz/yd epic fabric is too thick to breath like the thinner epic fabric in the oware bivy sac.

Does the thickness of the fabric change the air permiability? And if it does, does the thicker epic fabric negate the benefits of using epic over gore-tex or anything less berathable fabric?

I hope to take pictures of the process and post them later. I could use all the help I can get.

Tom

Tom,

can't ans. your ques. however, i am very interested in your project. looking fwd to pics & updates as you progress. thanks for sharing. have fun making the bivy.

i'm wondering if the thicker fabric is more water resistant than the thinner fabric? is the thread count/density the same for both wts of fabric? maybe someone knows the ans. to these questions also? Mr. Bell, you copy?

Tom,

I have first hand experience making my own bivy and testing it in the field. Using 2.4oz Epic from Nextec for the top and 1.1oz/fd Sil-nylon for the floor I added no-see-um netting for bug protection and a half zipper. Total weight 10oz. On a recent trip to the sierra’s I had no problem with condensation. The bivy did a great job keeping my down bag dry after a early am rain as well as blocking wind and significantly increasing the temperature rating of my bag. Epic was very easy to work with and I have since made a pullover out of the same 2.4oz Epic. My source for materials was Outdoor Wilderness Fabrics http://www.owfinc.com/ I’d be happy to email you pictures or any info that can help you with your project.


Roger
roger_alsborg@hotmail.com.

I am interested as well in making a bivy sack out of these materials. Any thoughts on pattern cutting? I've sewed various "everyday" fabrics before, using patterns and not, but haven't yet cut my teeth on silnylon or epic or pertex or any of those. I have some thru-hiker.com stuff sack kits that I will make on day, but I like the idea of having a bivy and a small tarp for less than $200/each! To make the pattern, would I just trace the outline of my sleeping bag and add an inch or two? Where do you recommend placing the zipper?
Thanks,
Eliza

Tom,
In reference to your question about thickness and breathability...you could "estimate" that doubling the thickness (assuming no other change) would reduce the breathability of the fabric (not the whole bivy) by a factor of two. That relationship works better for less breathable materials (polyethylene sheet) and even there it doesn't work perfectly, so that's a rough estimate.

BPL had an excellent article about breathability which mentions other secondary effects (e.g., temperature, external conditions). Don't forget that your bivy would also include a mesh opening and seams, which have a disproportionate influence.

How about a bivy sack, built into a framed pack? You could use the sack as the outlayer layer of a back, then unravel it to have your bag and pad rolled up into the whole thing. Then you the frame of the pack provideds the lifted support for the bivy. You save on weight of the packs material by using the sack and set up takes almost no time.

PowerPac 2000 System from Moonbow - close to your suggestion

You might consider a pattern from Seattle Fabrics or Outdoor Wilderness Fabrics. It's inexpensive and they include a list of material suggestions for completing the bag. Or you might even consider one by Equinox at around $60 but then you would get to enjoy making one on your own. Just a thought.

I have a pattern which I have drawn up. I could make it look a little tidier and scan a copy and send it you if you like. Its a combination of a lot of bivies that seen and with plenty of room because I don't like being enclosed too much.

Wow Paul your right that is very cool. I think I will have to make one.

Jules,

once you're done, pics are obligatory 'round here.

good luck. can't wait to see pics of your finished product.

six moon provide a pattern for a bivy (lots of mesh though) for those handy with a needle

http://www.sixmoondesigns.com/ultralight/myo_Meteor.asp

http://www.seattlefabrics.com/bivy_sack.html

This pattern calls for certain materials, but one could replace the 3-ply gore-tex with 1.1 or something...they sell alot of it to. FYI.

Jacob,
I'd be very much interested in seeing your pattern, even if it's not cleaned up. off-list is ecava1 [at] swarthmore [dot] edu.
Thanks!

Here is the very basic plan of the bivy sack. It is neither to scal nor a tidy piece of work but the plan is so simple you can't go wrong. If you have any problems contact me via the email on the scan.

I've mentioned it before but I will make a manual for it when I get som actual photos.

thanks, Jacob! That looks really great. Do you have much field use in yours?

I have no field use in it yet. I've also actually modified those plans and will post the new ones up quite soon. I stuck with the bathtub floor but found a lighter and easier way to resist rain and for bug protection at the head end. The dimension are really quite bug so when I go to make a good quality one I will reduce the dimensions a bit and use cuben/spinn and quantum. I will get some photos and get them up pretty soon. I might also make another plan up for a bivy-tarptent hybrid. just something floating in the back of my head at the moment.

Edited by nihilist37 on 11/17/2005 15:51:58 MST.

Roger,
Did you get your Epic directly from Nextec? OWR's supply dried up.

Vick,

Yeah I just checked out OWR and like you said nada… I wonder what’s up with that? Since I completed the Bivy I recently finished a couple epic jackets, similar to the GOLITE Ether. Epic is an easy material to work with. I purchase some extra so if you have a need for it let me know.

Edited by FastWalker on 11/23/2005 21:43:16 MST.

Roger,
Thanks for the offer. How do you go about negotiating private deals on this site?