A few months ago, I made a set of panniers for my bike out of some cheap canvas at Hobby Lobby. They were my first major sewing project, so I put a few things together in the wrong order. I left the clips off until the end, the straps were spaced wider than I'd have liked, and a few other things weren't quite right.
Even so, they came out very well. My old panniers barely fit a 10# flour bag, and failed under the load. These are large enough to hold twice that, and would barely notice the weight. They can roll up and clip out of the way, and they look slick (They're unadorned black; my absolute favorite color scheme.)
I decided to make another pair for my girlfriend, and took my additional experience into consideration. The second pair was easier to make and came out incredibly.
Here's a more organized set of directions for making the panniers I made. They're much stronger than those on bit-of-green, but otherwise identical.
- A yard of heavy cloth (duck canvas, curtain fabric, or similar)
- Four yards of nylon strapping (the stuff that backpack straps are made of)
- Eight pairs of parachute buckles (Four if you don't need them to roll up)
- Thread to match the cloth
Although the PDF's directions are simple, they're nearly comprehensive. I'll add my notes to the suggested construction. (Some of this may be obvious if you have more sewing experience than I.)
The entire pattern fits onto a yard of 60" cloth, if you tile carefully. I had to shrink a few dimensions by a few cm to make everything fit.
If you want some added reinforcement, use nylon strapping (adjustable backpack strap stuff). Sew it in after connecting the sides to the bottom (A to C), but before closing the bags. Two straps, five inches apart on center, centered on the bottom, seem to work well. Make sure to stitch all across the base and at least an inch or two along the sides to provide your seams stress relief. Place matching straps on the lid.
Parachute buckles (the waist buckles on backpacks) work well for holding loads. Stitch them into the ends of the nylon strapping, making sure to use plenty of thread - this is a load-bearing joint!
To make the bags roll up, add buckles under the bottom for the lid to mate with. It's hard to explain in words, but picture rolling the bag into a little bundle. Wrap the lid around that bundle, and it'll reach around to the backside of the strapping. A buckle there will hold the bag rolled-up.
Make sure to hem the bag before closing it. The top edge of C (furthest from A) will be the visible lip of the bag, and should be protected somehow.
Once the strapping and buckles are on, the bag is ready for closing. That's simple enough.
Next, sew on the lid, checking for square and centering.
Finally, decide how to attach it to the bike. The exact mechanism depends on the bike rack used, so I can't offer much advice here.