using goretex for dry sacks

Feedback for the article published June 4, 2005.

using goretex for dry sacks

Postby frprovis » Sat Jan 21, 2006 2:31 pm

I have been experimenting with homemade goretex dry sacks for a variety of applications, using 3-layer Goretex from SeattleFabrics.com

Among other things, I wanted a neck purse in which I can store my guidebook or map while hiking without a rainjacket. (Those see-through vinyl map holders sound nice, but what happens when you are using a guidebook instead of a map? And what happens when you need to unfold the map? I'm speaking from experience here.) Like you, I used the simple fold over method of constructing a sack. That is, I took a piece of fabric 14" wide by 44" long, then folded to 14" wide by 22" long, then sewed up the side seams with a 1/2" straight seam (not a felled seam), with tieout loops inserted about 12" from the bottom, then added a tunnel for a draw string at the top. In practice, the collar of the bag, above where the tie-out loops are, flops over the bottom part when I wear it around my neck, thus protecting the contents against rain, but still making it very easy for me to get my book or map in and out. Now comes the tricky part. Seam-sealing. First I used sandpaper to roughen the surfaces on the inside of the straight seam, then used isopropyl alcohol to clean these surfaces. This was necessary because this is the outer face of the Goretex and hence has DWR and who knows what else on it that might resist the seam-sealer. Then I wiped down these surfaces with Seam-Grip by McNett and pressed together. Then I wiped down the outer surfaces of the seam with Seam-Grip. These surfaces have the tricot liner and absorb seam-grip very easily and hence are easy to seal. After seam-sealing, I trimmed the side seams to 1/4", to cut the weight down some. Final weight is a little over 2 oz.

One big advantage that I see with Goretex for something like this neck purse, is that if a little water does somehow get into the sack (such as droplets of rain falling on my book or map when I take it out to look at it briefly), then the water can easily evaporate later. Especially if I leave the neck purse in the sun at rest stop, I would imagine the inside will get very warm and quickly dry things out inside, assuming I haven't totally soaked my books or maps.

I also made some other stuff sacks and pack liners using goretex. For these stuff sacks, I use a half-assed version of the umbrella closure. That is, I twist the collar together and then wrap the cord around several times and then just leave it at that, and everything seam to hold together. I'm not too worried about submersion risk.

Have you thought about using Goretex for stuff sacks? The ripstop Goretex from seattlefabrics weighs only about 3.2 oz/yd, which is competitive with 70D PU coated nylon at about 3 oz/yd, or the silcordura at 2.3 oz/yd.

My experience backpacking includes a lot of hot days with steep ascents, during which my back perspires up a storm. Normally I used simple rucksacks, with no lumbar pad and thus my lower back presses right against the bottom of the pack, and thus right against the sleeping bag. When I used silnylon, I found that there was always dampness in my bag after a long day. At first I thought there must be a leak in my stuff sack. Only later did I realize that the pressure of my back against the pack and stuff sack was forcing the perspiration to pass through to the sleeping bag. I haven't yet hiked with the Goretex stuff sacks, so I don't know how they will work.
frprovis
 

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