Nalgene PALS pouch, part 1

This post outlines the design approach for a pouch to hold a Nalgene water bottle.

Requirements

I want this to be compatible with regular PALS. I don’t normally use Speed Clips or anything like that, the pouch should have straps to attach itself. This is fairly normal for this sort of pouch. There should be two straps, spaced to work in consecutive single-wide PALS grid spaces. This is a light-duty pouch so I’ll use Velcro or similar on the straps. Heavy duty 5/8″ snaps are normal but that’s overkill for my application.

The bottle is a Nalgene wide-mouth 32-oz. Tritan. It’s a pretty standard bottle, not the one with the easy-drinking mouth. I don’t use the spill protector and I haven’t made changed to the bottle from the standard factory configuration. The bottle should fit snugly but it should be relatively easy to get it in and out.

I don’t need any PALS grid, pockets or attachments on the outside of the pouch. This design is not for tactical use so none of that is necessary.

The pouch needs to be lined and insulated all around to keep the contents of the Nalgene bottle at temperature for as long as possible. I don’t need padding other than what’s necessary for the insulation.

Materials

The primary fabric I’m going to be using is 500D uncoated Cordura knock-off. This will be the fabric for the outside of the pouch. The lining will be 1/4″ grid lightweight ripstop, which has the same properties as slightly heavier-weight Cordura.

I don’t have a good source for the correct 5038 webbing yet. I do have plenty of nylon webbing though, which is much thicker. It’s been serving me well for the last few pouches I made and I’ve learned to work around its limitations. I have matching non-Velcro hook & loop in 1″ and 2″ widths, although I expect to need only 1″ for this project. I will use matching 7/8″ grosgrain ribbon as seam tape where necessary.

For insulation, I have a few options, each of which will likely be made into a prototype:

  • Fairfield Solarize, a material made specifically for this sort of application. It’s sold by the yard at the fabric store.
  • An ordinary space blanket, cut up. Mine is a leftover from a marathon that I ran a while back. By, “a while back,” I mean close to a decade ago. The stuff is in good condition so I’m confident that it’ll hold up for another decade. If you don’t have leftovers of this sort, you can buy a space blanket in the camping goods section of Wal-Mart or similar.
  • Chocolate wrappers. Kit Kat, most likely, to be specific. Completely recycled. I have several since I don’t know yet how much fabric (if you can call it that) I’ll need. I ran them through a delicate cycle in the wash to clean off the excess chocolate.

Materials Research

With different insulation options, none of which seem perfect, I’ve got a research project on my hands. Specifically, I’m concerned about the workability of each of the options. Here’s how the different options stack up:

  • The Solarize looks like it’s going to be easy to use. The directions recommend fusing it to fabric and using a layer of batting. I have some lightweight cotton batting that should work well. Across the grain, the Solarize doesn’t stretch at all. With the grain, it’s got this strange stretch, you have to pull a little to start it, it stretches, then it returns to normal, but slowly. I haven’t tried to stretch it very far because it looks like it’ll act plastic and the insulating coating may not return to normal if I do. I have doubts as to how well it’s going to insulate, I think it’ll fall near the bottom of the list.
  • The space blanket is thin and doesn’t stretch at all. I don’t know how easy it’s going to be to sew with it and I suspect that I may have to glue it to something. The Intertubez say that it can be glued with contact cement. I’m probably going to have to glue it to the batting. It may need support as well, I’m likely to try precycled Tyvek and ordinary stabilizer. I’ve used this material as a blanket before though and it works ridiculously well. I suspect this will be one of the best options.
  • I think that everything that holds true for the space blanket will hold true for the candy wrappers as well. The major difference, I think, is that they’re even thinner than the space blanket. I may just glue them directly to Tyvek. I estimate that these will work better than the Solarize and not as well as the space blanket.

My standard for insulation is sufficiently low that I’m not going to concern myself with any heat exchange that will happen through the seams. I’m looking for something that’ll keep a Nalgene bottle full of ice cold for about 2 hours on a Texas summer day in direct sunlight. I’m fine if the ice melts — I prefer that, actually — but I want the water to be cold or at least cool. If the ice doesn’t melt in 4 hours, that’s too much insulation. If the ice melts and the water gets warm in under an hour, that’s too little insulation. I’m not using a thermometer so my range is wide. The threshold for, “melted ice,” is anything that involves turning ordinary freezer ice cubes into little floating bits. The threshold for, “cold water,” is something that’s at least cool when I drink it. In terms of thermal mass, my standard is that about 2/3 of the bottle has to be filled with ice and water, because I’m going to have to drink some water to gauge it’s apparent temperature.

I’m looking at Tyvek for backing on the thinner materials because it’s breathable yet waterproof. I have concerns about the pouch getting wet from the bottle sweating, then the wetness causing mold or mildew on the lining of the pouch. I have anti-microbial lining material as well but that seems like it’s outside the design tolerances that I have in my head, both in terms of price and thickness of the finished piece.

The materials research that I’ll get from trying out these options will likely be reusable, so I will cover the specific tests in a separate post. I don’t expect to be able to test the insulative value of each of the options until I’ve completed 3 prototypes and can test this live in the hot summer sun.

Pattern

While I don’t have a published pattern for this — I’ll be developing it as I go — I do have a finished model to work from. This is a Rothco pouch made specifically for Nalgene bottles.

To start with, my pattern will be different in several ways:

  • I will have a smooth, flat external surface. My design will have no PALS grid, no D-rings and no zippered pocket.
  • This pouch is designed for what seems like a different-sized Nalgene bottle than what I’m using. Specifically, it’s about 3″ too tall. Maybe there are different kinds of Nalgene bottles that are taller but this is not a concern for me.
  • The top of this pouch has a zipper. I would prefer a, “hat,” that slips over the bottom section with Velcro around, and a pull tab to open it.
  • The attachment straps on this pouch are a doubled-over design with snaps. The cover of the snaps are on tabs that extend from near the bottom of the pouch. This looks like a good design but I think it’s too complex for my application.
  • You can’t see it in the picture here, but it’s got a Velcro-closed slip-through flap at the top, probably for a straw or hydration tube. I don’t need this in my design and I will not include that.
  • Also not vitible in this picture is a grommet at the bottom of the pouch. I assume this was added for drainage and possibly to assist in air pressure relief when inserting a bottle into the bag. I would rather gain the additional insulation of an interrupted bottom panel. I also plan to make my pouch slightly larger and less padded so I don’t believe air pressure will be an issue.

The starting dimensions of the main space are 13-1/2″ in circumference and 8″ tall. I’ll add 1/2″ to the circumference and subtract 3″ from the height, giving me 14″ in circumference and 5″ tall. The hat portion looks about right at 2″, but I’m going to add 1″ to cover the space I need for my Velcro closure, for 3″. Given a 14″ circumference, a simple calculation yields a diameter of roughly 4-1/2″, to less than my presumed design tolerance of 1/8″.

I’m designing with a 1/2″ seam allowance to make everything easy. Given that, I need the following pieces for the primary chamber:

  • The main body is a rectangle, 15″ x 6″.
  • The hat band is a strip, 15″ x 4″.
  • The top and bottom are circles, 5-1/2″ in diameter.

I’ll cut both the top edge of the main body and the bottom edge of the hat 1/4″ long. Between the seam allowance and that extra 1/4″, I’ll be able to do a double-turn or French seam finish instead of a taped seam so that there isn’t extra bulk.

I’ll cut the insulation padding 1/4″ short on all sides so that it sits inside the seam allowance of the outer fabric and the lining. I expect to attach it to the lining. This should help to prevent bulk in the seams. If the piece is cut and assembled correctly, the extra space will likely get taken up by the seams so there will be no gap in the insulation.

Fully adjusted and laid out, I’ll need the following pieces:

  1. The main body outer fabric, 15″ x 6″ of Cordura.
  2. The hat strip outer fabric, 15″ x 4-1/4″ of Cordura. I added some width to allow for a 1/4″ double-turn finish and length so that there’s a little breathing room for the Velcro. I could probably get away with less width, eating into the seam allowance, but I’d rather over-cut and trim excess later.
  3. The bottom outer fabric, a 5-1/2″ diameter circle of Cordura.
  4. The top outer fabric, a 5-1/2″ diameter circle of Cordura.
  5. The main body lining, 15-1/2″ x 4-1/2″ of ripstop.
  6. The hat strip lining, 15-1/2″ x 4-1/2″ of ripstop.
  7. The bottom lining, a 5-1/2″ circle of ripstop.
  8. The top lining, a 5-1/2″ circle of ripstop.
  9. The main body padding, 15″ x 5″ of insulation material.
  10. The hat padding, 15″ x 4″ of insulation material.
  11. The bottom padding, a 5″ circle of insulation material.
  12. The top padding, a 5″ circle of insulation material.

Given standard PALS grid spacing and with a 5″ main body height, I’ll have only 1/2″ of body to attach the PALS strips with their fasteners if I make the strips 2 spaces tall. I think the best option is to attach the straps to the top, because there’s plenty of space there. The finished piece will sit slightly out of alignment with the PALS host on which it’s attached. Horizontally, there will be 1″ of space between the straps, which will be used at the top to form the joint between the body and the hat.

The main seam, forming a cylinder out of the body and hat, and the seams around the top and bottom, will be finished with 7/8″ ribbon. This is approximately the same as the construction of the model, pictured above, turned inside-out. From that picture, you can deduce the order of construction: the body was attached into a cylinder before the top and bottom were attached. This means we’re going to construct the piece predominantly inside-out then turn it when completed.

In the next post in this series, I’ll cover the order of construction for the piece.

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