I once envisioned making a outdoors/active pack out of a road sign, and this took two years to reach fruition.
This is about a 30L pack using about 2/3 of a road sign to make. Stitching was all done by hand, since the material is so thick. It's kinda Like sewing leather.
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Step 1: Cut Your Pieces
You'll have to excuse some of the missing pictures, as I got caught up making this I had too few:( But since I used no pattern and just went by feel, you can too!
Main Piece (front, sides): 16 x 20 squares (~ 18x23"). This consists of the front, intended to be 14x6 squares, and the sides 14x7 each. The top will be folded over at 1/2 a square. Bottom will be similar in a flat felled seam.
Bottom: 9x10 squares (7 square depth +2 edge folded up, 8 squares width +2 edge folded up)
Top: Using a triangle corner piece about 15" in height
Back: I don't know, fitted late in process. Went with an hourglass shape similar to front piece.
Step 2: Sew Bottom to Front Panel
I used a flat felled seam to connect the two pieces, using the grey backside for the bottom exterior. I stitched initially only 4 squares in the middle. This was because I wanted the two sides of the front portion to slope back, rather than the bag being completely square. To do this, I folded up a corner of the bottom to create a diagonal, stiched it, and then attached to the frontal piece. I maintianed the half-square fold from the flat felled seam of the frontal piece along the whole piece. Once the corners have been sewed in, sew the side parts down.
Step 3: Sew the Back
Pretty simple, used a blind seam to connect these two. The edges from the frontal piece are folded over to meet the back panel. Depending on where you want the seam, sew this blind seam down onto the back (recommended for structure) or side. Keep in mind the half square fold over of the frontal piece should be maintained at the top and bottom for structure and smooth edging.
Step 4: Top
Perhaps the hardest bit to shape properly, it took a bit of knocking about to get the right shape. I started by taking parallel line from the front edges and folding them upwards. This crease can then be folded over two units over the create a triangular fold. This will create a round shape for the top to fit over the rectangular-ish bag. the corners will wrap around forming the backside of the top flap, which you can sew in place on the backing. This might be a good place to add a small pocket for keys, cell phone, etc.
Step 5: Straps
I cut out a tri-ring custom out of cedar scraps for the triangular joint of the straps that hold down the top flap. The nylon straps 1" wide are best using seatbelt material. The singular strap is attached via a hook to the top flap for easy securing and access. the bottom two straps make their way around the bag and are secured at the bottom corners on the backside. These then turn right into straps for the pack itself, securing at the top of the bag at the desired location. I recommend wearing the bag high up, since it is relatively large in size.
Step 6: Explore!
This bag is perfect for long days outdoors. The material is durable, waterproof, and look awesome! It'll no doubt turn heads!
Another great use is biking, as it sits nicely close to your back and is highly reflective!