In this lengthy, and I mean lengthy Instructable, I am going to show you how I go about designing a bag, from start to finish, or how I like to put it, from Pattern to Product.
This style of waist-pack has come back into vogue and I am very happy that they are. No one can deny the functional superiority of a small pack like this, worn like a sling bag or even in it's true form, as a fannypack.
My background is, and this does not preclude that you require this, is about 10 years of industrial sewing and 15 years of graphic design. This is why I am using Adobe Illustrator to draft my pattern and several industrial sewing machines to help me finish this project.
The concepts are the still the same, so....grab a cuppa joe and come along!
Step 1: Drafting the Pattern - General Form.
This design is no more than a projected box with rounded corners and a lot of strategically placed straps. To start, let's define the final size of the front of the box. This will help inform the rest of the dimensions and parts.
The box is a 9" wide, 5" tall with a 1" radius.
I give a really generous 1/2" seam allowance for the outside, this will give plenty of room for tacking on straps and doing basting stitches.
From there, I split the general form based on some 6" finished zippers I have. The horizontal line represents the zipper line, the vertical lines represent the seam that will finish the zipper. I split those side "wings" and add 1/4" between the center section and the wing. The zipper will add 1/2" to the height of the middle section so there is no need to add seam allowance.
These 4 panels will be used to make the BACK of the pack, kind of like a secure pocket since it's zipper shut and it's closest to the body.
Next up, let's add some dimension to the FRONT of the pack.
Step 2: Drafting the Pattern - Darts and Pillow
From the general form pattern (with the generous 1/2" outside seam allowance), I now offset the pattern 1". The reason is to create some thickness and room in the front part of the pack. Otherwise, it would be flat.
The illustration is of the corner, this is where I have drawn a dart. If I add 1 inch to the over all pattern, I need to take it away somewhere so it can come back to the original dimension. This is kind of a rough math thing but the wide end of the triangle is 1" and after the dart is sewn together (with a small 1/8" seam allowance) this should pucker all four corners and make it like a pillow with a zipper in the middle of it.
Step 3: Pattern Draft - Zipper Panel and Base
I goofed here and measured the wrong circumference, instead of the final dimension circumference, I measured the outside 1/2" seam allowance. Illustrator is great for this, it's Window>Document Info> *drop down* Object.
I have 11" finished zippers so I drew an 11" x 2" + 1/4" on either side (for a final of 11.5"x2") for seam allowance. In hindsight, I should of made this 3" because the 2" was super tight but made for a slim profile. Maybe 1/2" more but no more than a full inch should of been added for the depth of the main compartment. I subtracted 11" from the distance measured and then split that into two rectangles + 1/4" for the a joining seam.
You'll see later how I figured out how I goofed. I also tried to add some relief cuts onto the rectangles where they would start to bend around the corners. I forgot to screen cap the rectangles but you'll see them in the laser cut parts.
Step 4: Materials + Laser Cutting
After drafting the pattern, you can do either print out the pattern and then cut the materials by scissor or rotary cutter OR if you have access to a laser cutter, cut them out with a laser. Advantage of the laser is that you can include center witness marks and have perfect corners. Disadvantage is that laser cutters are pricey.
I chose some Burgundy 1000D Cordura for the exterior and 400D PU coated nylon for the interior. I prepped the pieces and cut them on my Glowforge. You can save time erase the overlapping lines to avoid double cutting. This not only ensures your parts line up (I had made a similar bag with a multicam pattern that I wanted to line up) but it also saves on machine time and overly burned edges.
DO NOT use any PVC backed or PVC based fabrics if you are laser cutting, PVC forms a poisonous gas when burned. Cordura is 100% Nylon which does not release any toxic gas (just smells funny).
I cut 1 front panel assembly (with the darts and zipper relief), 1 rear panel assembly, one interior Cordura panel, 3 interior panels, 3 interior dividers, and zipper panels. I didn't use all of these parts but I had the room on my raw stock.
Step 5: Front Pillow Panel Assembly
I use my walking foot machine with a 3/4" binding attachment to both bind and stitch the zipper to the top and bottom of the front/middle panel. I don't top stitch, at least not on this project. It allows for a little bit of play between the parts. The zipper used here is a 6" #5 finished zipper. There is a very small 1/4" of seam allowance.
In the 3rd photo, the 'wings' are attached to the middle panel with the same 3/4" black binding. In the 4th, I sewn shut one of the darts, after all 4 are sewn, the pillow is formed. In theory, that extra inch that was offset from the pattern should translate into an 1" of depth in this pillow.
Step 6: Front Panel Assemble Con't
Once the pillow is formed, it needs a panel to anchor to so that the front panel assembly can be finished.
It's easy to get overwhelmed with the details of making a bag, but making a small pack like this is the same as making a huge treking backpack. Just have to think in layers and order of operations. You can't add stuff to a layer that is already shut, so think through what needs to go where and work backwards.
Case in point, the blue 1/2 panels are the internal dividers, they get a 3/4" binding to finish the edge. You can hem these but I have the binder set up so its easy to zip them through the walking foot.
After sewing a center divider on the flat panel, it was time to mate the pillow to it. In the 2nd photo, you can see where the integral, center witness makers make it SUPER easy to line up the 3-Dimensional pillow form and the flat 2-Dimensional backing panel. I use 3/4" binder clips, very effective and can be collected by a magnet on the side of the machine. I sew the perimeter with a loose 1/4" seam. This isn't the final seam but it'll do for tacking down the forms. For this I use a standard straight stitch machine. I chose to use a 1000D panel for the backing of the pillow because it moves less than the 400D nylon, with such accurate laser cut alignment, it's not that critical.
In the last photo, you can see the internal organization divider I placed inside.
Step 7: Back Panel Assembly
The back panel is much easier to complete. There are no darts to sew shut, just flat pieces.
Same technique here, 3/4" binding, #69 nylon thread.
I then use the larger blue panel and add some dividers like the front section, but this one will have full length dividers, no center stitch.
A perimeter sew keeps things nice and tidy.
Step 8: Accessory Straps - Front Panel
Once the front and back panel assembles where done, it now time to think of how they will interact with each other. Like I said before, I wish I had made this particular pack with a bit more thickness in the main compartment, these 1" compression straps are a little overkill. In the end, they worked well for carrying small items under the pack but aren't necessary for function.
Regardless, for the purposes of the this exercise, they shall remain.
I really like this design because it provides some really nice datums and alignment edges for features like undercarriage compression straps and top handles. Its very important to remember that this pack is being built INSIDE OUT, which requires the clips and ladder locks to be installed backwards so when the pack is flipped out, they will be in the right orientation. It takes some mental thinking but once you get your head around it, it's not that bad.
I add two ladder locks on the bottom of the front and to the two edges of the short side. On the top, I add a 10" long section of 1" webbing, that will become a nice grab handle.
Step 9: Accessory Straps - Back Panel
For the back panel straps, this is where things could go wrong, but with some careful planning its alright!
The top handle is pretty easy, same as the front. Same goes for the bottom compression straps. The sides is where layers can be mixed up. I used a 1.5" webbing for the main belt and on TOP of that a 1" webbing that will act as a compression strap AND a load lifter which will bring the pack closer to the contour of the hips/waist.
I always use more than I need on those straps and then adjust later. I think I use about 24" of 1.5" webbing and about 15" for the load lifter/compression strap. The bottom compression strap, I used a 12" length.
Step 10: Zipper Panel/Base
This is the part that took me the longest to figure out how to do.
I install the zipper much like I installed the zips for the front and back panel assemblies. I then took the blue panels and tacked them in place with a 1/8" seam. Sandwiching the OUTSIDE burgundy panel and the zipper panel, I give it a final 1/4" seam. This gets pulled down and a nice flat outside is achieved. I do this for both sides of the zipper panel/base and give the base walls a temporary baste on the perimeter so that the two layers don't move.
Hope this makes sense, it's likely one of the most complex moves.
Step 11: Sewing the Zipper Panel to the Front and Back
I take it back, this is the most complex part of the build.
Starting from the top of the pack, and the middle of the zipper panel, I hold down the edges together with binder clips, adjusting as i go to make sure the sides are equal and aligned. It's now that I realized I goofed and have too long of a bottom section. No mater, it's easier to trim than it is to add material.
After checking and checking again...(i actually sewed it backwards so I had to undo my stitch and RE stitch it back in place) I leave the bottom section unsewn so that the point where the bottoms meet can be attached later. I take great care in making sure those curved stitches are smooth and the the transitions are good. Notice the relief cuts along the corners, they are pivotal in the success of those curves being tight and smooth.
I attach the back the same way, facing the INSIDE of the pack out so. Be sure to open the main zipper so that it can be flipped over when the seams are done.
The last 4 images is me marking where the center of the base of the pack is, then trimming the excess, binding the edge and then finishing the perimeter of the bag. The pieces left over are good to keep to measure how much I have to take off my pattern. If that's the only mistake from a never been tested pattern, I am pretty happy with that.
Step 12: First Flip + Load Lifters
This is the most exciting part for any pack build, the first flip out!
I am digging the small form factor of this with the chunking handle and hardware.
Remember the load lifters? I mark about 2" from the edge of the pack and then sew a small box stitch to combine the 1" and 1.5" straps. When the 1" strap is pulled tight, it will take the 1.5" main belt with it and pull it closer to the body.
Ok, this step didn't need to happen now, but its just too cool not to see!
Step 13: Final Binding and Detail Finishing
I now turn to my double needle machine with 1" binder attachment. This machine is a beast with 3/16" spaced needles and a pressure foot the width of my index finger. It quietly and effectively chews through all the layers of material and cleans up the edges of the inside of the pack.
I got back to my single stitch and double roll hem all the exposed webbing ends, checking for length and trimming when necessary.
Step 14: Finale: From Pattern to Product
This kind of project is full of problems to solve, great use of machines and uses some nice lateral thinking to create a very functional object. I used the bottom straps to hold an umbrella in the pic, pretty much any tubular item or even a light shirt/sweater.
This pattern is pretty easy to stretch and expand (or contract). I've made much larger 18" x 9" x 4" sling packs much like this with some heavier straps and different materials.
Hope this helps! Happy sewing.