Sunday, March 23, 2014

Breaking Down the Boxy Pouch

OK, so I'm going to take a crack at breaking down the boxy pouch for you folks. It's a super-easy bag to make (see my tutorial here) and useful for so many things, but I always took a shot at the size of it without any real science behind it. When I had to make a toiletry bag, the size and where I wanted the zipper placed threw a few geometrical kinks into the process, making me stop and think and puzzle and sketch.

If you've made a simple tote before (I've got tuts for those, too--check the tab above) you'll know that the bottom corners can be boxed to give a flat bottom. It's easy to figure out, for the most part, and doesn't require too much mathy sort of thinking. But with a boxy pouch, the sides are what gets boxed and the method is therefore a little bit different. I wasn't having an easy time figuring things out (remember--the math part of my brain doesn't function well), and just could not visualize the shape I was going to need. My sample had come out OK, but I wanted better than OK. I was suddenly overcome by the need to know just how this thing went together, mostly so I could make any size I wanted without trial-and-error or things coming out not quite right.

So I took my sample apart. It was a piece of ugly fabric and a zipper in such a weird color I don't even know why it existed, so it didn't break my heart to do it. I've tried to recreate it all here through the magic of PowerPoint, but you'll get the basic idea and hopefully be able to make any size you want as well.


Hmmm. That looks interesting. So let's see what's what (and keep in mind this is just a rough graphic).


If you hack off the bits that say 'Side' you'll see it's just a giant rectangle. BTW, those skinny pink strips along the top and bottom are supposed to be the zipper (note: I also have a very low-functioning art part of the brain. Second note: I cut the ends and pulled the pull off the zipper to open it up like this--it normally wouldn't be possible to do that).

So you can clearly see how the front (or back) shows the width and height of the bag, and the bottom is going to make up the depth of the bag, with the pink zipper strips meeting to form the top. The part left to consider is getting those side flaps to meet. It's as simple as one plus two equals three. Pretty much literally. Let's take a look at one of those corners.


As the pouch gets going along the sewing process, edges 1 and 2 will come up and get stitched to side 3. If your bag is going to be six inches high, for example, those two flaps that stick out need to stick out in amounts that will total six inches. And that's where you can adjust the zipper placement. If you want the zipper to fall dead center, then those two flaps would be the same. If you want the zipper to fall higher, then the tab coming off the bottom needs to be longer than that coming off the top near the zipper. If you wanted it lower then the reverse would need to happen.

What I 'drew' for you above is a rough estimation of my starting point. Now I'm going to show you how you can take this and  adjust it as I did to customize the size. Let's say I want to make a bag that is six inches high by ten inches wide, with a depth of three inches. I start off with my 6 by 10 rectangle. I add seam allowances to the sides only. Let's say I'm using quarter inch seams.


Easy enough. Now we need to add the bottom. It's three inches. The length will take some easy math. We know our bag is going to be 6 inches high. For fun, let's place the zipper 1.5 inches up from center (which would be at the 3 inch mark, so our zip will end 4.5 inches up from the bottom). Do I know how to party or what? It'll look like this now:


OK. Now we need to add that top where the zipper is going to fall. The length of this rectangle will be easy (it's similar to the bottom but with different numbers for the length of the flap). It's the width of it as we need to account for the zipper that's a little bit of a thinker. A standard zipper is an inch wide. That top rectangle you see below is where one side of the zipper gets sewn (and we'll end up with two of those in a minute). It needs to be half the bottom piece, so that's 1.5 inches. Considering the seam allowance (which is a quarter inch), once the zipper is sewn in those parts will be 1.25 inches each (totaling 2.5 inches) with a half inch of zipper showing between for a grand total of 3 inches. Perfect. If you're using a zipper larger than an inch wide make sure you account for that in your pattern measurements.


So there's your bottom, your front or back, and the top. You just need to add the back (or front) and another top piece (because that zipper has two sides) to the bottom and there you go. Just like this.


There's one last thing we have to add, and that is the seam allowances where those flaps are going to get sewn into the sides. You might feel tempted to add to the edges of those flaps but don't do it--you'll have too much fabric in there when you go to sew it all together.


And that's that.

So there you have it. The deconstructing of the boxy pouch. Doing it this way keeps your dimensions intact so that no awkward (or unintended) shaping results. It's especially important if you'd like to make a perfectly square pouch, or if you're making a larger bag and don't want the zipper to sit too far down the side.

I've only ever made one size before (the one I show in the tutorial), so this was very eye-opening for me as I was figuring this out--lots of a-ha moments. Hopefully it helps a bit in your bag-making. They work up to make pretty adorable bags that you could fill with goodies and gift, and they don't take very long once you understand the details.

For those of you who are all "Gah! The math! This reads suspiciously like math!" then never fear. This is just a bit of a primer on the process, but we'll make a few together, and I'll walk you through it. M'kay? Stay tuned!

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6 comments:

  1. It isn't math, it is engineering! The motto of engineers is "close enough for all practical purposes". It is amazing how well that works in sewing.

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  2. Ahh, that makes complete sense! Well done. =)

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  3. Really helpful for sizing up for an overnight bag:) All I have to do is work out how big a bag daughter will need!

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  4. Oh my goodness! I just found your sizing tutorial when reading Vicky Myers' blog post and you are a legend. You made it very simple. Thank you!!!!

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  5. This is great! Thank you for this tutorial!!

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  6. Thank you for this clever tutorial. Maths is my worst subject and I can't get my head around figures for zipper placement at top of pouch. I need a bag 12"high x 15"wide (knitting needle pouch for sister). I think 6"depth (?) Can you please tell me how many inches from bottom to make zipper go across top of pouch? Thank you so much. Louise Western Australia

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