Making My Own Bivy Part 1

In an effort to keep my running vestpack as light as possible, I decided to make my own bivy. I ordered two kinds of waterproof, breathable fabric from Z-packs: 1.0 oz/sq yard Dyneema Composite Fabric, which I am using for the bottom and sides, and .34 oz/sq yard Dyneema Composite Fabric, which I am using for the top. While I am anxious that I will be cold after running all day, being sweaty, and perhaps not having enough food to keep me warm, I think the more of the heavier fabric I use, the warmer I will be. I am always cold after my long runs, so I can only imagine I will be cold the night of my fastpack.

This is a quick sketch of my basic idea and shape. The upper right shows a mini version in profile, whereas the main image is looking straight down at it.

I decided to make the bivy out of an old sheet at first, rather than cutting into the costly fabric. You could also use cheap muslin. I spread the sheet out on the floor and then put my sleeping bag on top. I then folded the sheet over it with a little extra on the sides, knowing that my body inside the bag would mean the bivy would need to be a bit bigger than an empty sleeping bag. I wanted the shape of the bivy to taper with the sleeping bag, so at the bottom, the fabric meets, but toward the top, there is a gap of about ten inches. I made marks on the sheet with a Sharpie and fashioned a pattern out of butcher paper using those marks once I unfolded the sheet.

I first folded the bivy fabric over my sleeping bag and then traced the shape onto my butcher paper. I cut the sheet to the size of my piece of 1.0 oz/sqyd Dyneema Composite Fabric, which is 2 yards, and then used my butcher paper pattern (on top of the sheet in this photo) to cut the sheet to the right shape. I made the pattern half the total shape so I could fold the sheet and only have to cut once. The sheet is unfolded here so you can see the overall size. The pattern is folded to show where the fold will be when I sew the edges together.

Here, I've sewn the edges together. The seam only goes 22 inches up. The remainder is open in a triangle. The top of the triangle is 20 inches wide. That's where the lighter weight fabric will be sewn.

I made it about six inches longer than my sleeping bag, and when I get in it, I have just enough room--with my feet against the bottom end, my head is just under cover. The 1.0 oz/sq yd DCF is only just long enough for this, so if I want to make it longer, I can only do so if I happen to have enough scrap from the width--or use of the lighter .34 0z/sq yd DCF. At any rate, if I can't add any length, the bivy will at least be lighter.

I opted for a width that is just a bit wider than my sleeping bag. Essentially, it is a shell for my bag that will hopefully keep me warm and dry. The bivy is 22 inches wide at the bottom and 40 inches wide at the shoulders. The length is 72 inches. I am five foot seven inches tall and 130 lbs with a slender build.

I then sewed the sheet together using large stitches (5.0 for stitch length) along the bottom where the sheet meets, cutting much of the excess fabric off (but not too much in case I needed to make it wider). I used large stitches so that they would be easy to take out if I needed to make the bivy larger. I then cut a piece to represent the lighter fabric in a triangle shape (twice as wide as needed to allow for staking the top above my head) that I sewed into the gap. I also cut a small rectangle to sew onto the bottom to close it up that is five and a quarter inches by 19 and a quarter inches.

The third number on my machine is the stitch width. I used the widest stitch so they would be easy to take out if I made a mistake. Also, in the end, I'll take the whole thing apart to make a final pattern.

I then got inside and used my running pole two-thirds put together to stake the middle while my husband pulled the sides taught. I had him mark where he pulled it tight so that I can attach cords there. I also had him mark where my pole was so I can sew a little pocket on top and bottom to tuck the pole into place. I will also need to attach a cord on the top to keep the pole upright but staking it outward as well.

I held my hands to pull the fabric tight at the bottom and my husband mark those spots. When I make the real bivy, I'll attach cords here. The pole will need a pocket to hold it in place on top and bottom.

This is the top view from the back. Pretty small bivy. With no zippers and minimal fabric, it should be light!

When I make it out of the Dyneema fabrics, I'll make a mesh screen triangle for the front of the bivy. I will sew it to the bivy on one side, and then Velcro it to the bottom and the other side. I think that will be the only way to do it and still be able to get inside.

The next step will be to take the sheet bivy apart so that I can use the fabric to make a new pattern before I cut into the real fabric. My original pattern is a little bit big. I didn't have to resew anything, but I noticed that there was too much fabric before I even began sewing.

Please note that all dimensions are finished dimensions. When cutting out fabric pieces, you'll want to add a 5/8 inch minimum seam allowance to any side of the fabric that will have a seam. That means the triangle will be an inch and a quarter wider, for example, to accommodate the seams.

PLEASE SEE PART 2, when I make the real thing!