I'd been wanting to make bike panniers for a while. I bought a set of Jandd mountain panniers but they were both small and annoyingly designed (a pain to get on and off the bike), so I returned them. I borrowed some Ortlieb "Backroller Classic" panniers from a friend for a weekend bike camping trip in Napa and liked them, but they're expensive, don't have easy-access pockets for a wallet, and still weren't large enough to hold my tent and fully close (which would be a problem if it rained).

So maybe I'll make my own. This version is just a simple prototype to get a feeling for size, shape, and what hardware I want to use (this one includes a mix of hardware from Ortlieb, Outdoor Wilderness Fabric, and Sailrite). It's a bit ugly and lumpy-- I just started cutting and sewing freehand.

The general bag: a standard rectangular shape with a top that rolls down like an Ortlieb (for waterproofness), and some clips to attach it to a bike rack. Built out of some striped boat upholstery fabric that I got for cheap at a closeout sale.

One question was how the mounting hooks should attach to the fabric. An approach many panniers take is to have a stiff sheet of plastic inside the bag to both hold a shape and provide something for hardware to screw to. I decided to skip that for now (to make it easier to roll up the bag and stow it / carry it when not in use) and just screw the hardware directly through the fabric.

You can see the fabric up close here. And I didn't actually screw directly through the fabric (which might tear over time as the bag bounced up and down on the bolts)-- I installed grommets like this wherever a screw or bolt was going to pass through the fabric.

Here's the inside of the fabric, with a screw and nut passing through a grommet (hidden) -- I hope it's waterproof [edit: I went biking in the pouring rain with this on my bike and confirmed it's waterproof]

The grommet holes are a potential water leakage path... so for now, I'll cover them with duct tape. In the actual bag, I'd have two layers of fabric in the wall of the bag and the grommet and hardware would only pass through the first. I might also have a whole separate, suspended vinyl liner, to avoid water seeping through the sewed seams.

Here's the bag prototype on my bike. I sized it to hold my camping gear: this is a tent, a thermarest air mattress, and a sleeping bag, all in one pannier. The next version should include some extra external pockets (zippered? roll-top?) for easy access to my wallet, camera, and so on.

Another view of it on a bike. After building this I took it out for about a 6-mile ride around the city in the pouring rain, and it stayed dry and held on. But there's still room for improvement.

I should probably add some reflective strips, and a little more internal structure at the bottom to make sure it can't deform and slip into the wheel (especially when the bag is nearly empty and can flutter in the breeze-- when it's full, it's quite stable and holds its shape).