It's a new semester, and I have lots of homework I should be doing, so I decided to spend the afternoon making a set of panniers for my bicycle. I wasn't thrilled with the price of panniers I saw online, so these can be made with a little sturdy fabric and some time.
My bike rack has a spring-loaded clamp on the top of it, so I used that as the primary means of stabilization. If yours doesn't have one, you should be able to make modifications to tie the panniers on firmly without much trouble. I chose to make my panniers 12" long, 11" deep, and 3" wide. It fits nicely one (very full) grocery bag per pannier.
Step 1: Measure & Cut
Like I said last section, the measurements are very important. Since I didn't use a pattern, I had to do some arithmetic to figure out how big to cut things and where to place pieces.
My measurements: 12" long, 11" deep, 3" wide. You also need to know how wide across the top of your rack is (mine is 4" across).
Cut a piece of fabric the same width as your desired bag length (plus seam allowance - I cut mine 13" wide) and with a length equal to 4 times the bag depth + 2 times the bag width + the rack width (4 * 11 + 2 * 3 + 4 = 54" here), plus a couple inches seam allowance. This piece will form the main body of your panniers. Note: If you're lazy (like me) this is handily close to the width of a 60" bolt - you can then just cut the width you want all the way across the bolt. You still need to know the measurements you want, though, for the next section.
Cut two more pieces that are the width you want your bag's width to be (3" in my case) and with length equal to twice the bag depth + the bag length + a little seam allowance (2 * 11 + 12 = 32" here). These pieces will form the sides of each pannier.
If you want to make flaps, put one final piece the width you want your bag's length to be plus seam allowance (12" + allowance here), and with length equal to rack width plus twice bag width plus twice your desired overlap allowance (4 + 2 * 3 + overlap of 2 here = 12"). Actually, in this example I was low on fabric so I made mine a little less wide than the entire piece - oops.
Step 2: Create & Reinforce Bottom
Lay your base piece (the really long one) out flat. From one end, measure the depth of the bag with seam allowance (11" plus seam allowance here). Mark the fabric if you need to. Take one of the shorter pieces and lay it across at that point as pictured, making sure that it is centered. Since the double layer of fabric will be the bottom of your pannier, you should have enough fabric for the full depth of the bag towards the edge. Pin these together so it's nice and secure.
Sew with a zigzag stitch along the edges of the double layer. The zigzag helps control the raw edge here. Reinforce as much as you feel is necessary with whichever stitch you want.
Repeat this step on the other side.
Step 3: Sew the Outer Sides
This is a good time to decide which side of your base is uglier. With the pretty side in, pin and stitch up the shorter, outer edges only. (We will do the inner edges later.) Use a blanket stitch to control the raw edge and prevent raveling. When you are done, you should be able to imagine the entire piece kind of looking like a large open staple.
Hem along the top of the bag, using a zigzag or blanket stitch to control the raw edge (or you can do a rolled hem).
Step 4: Sew the Inner Sides
Flip the piece around right-side-out. We will do the inner sides the wrong way so that the hem across the top of the bike rack is underneath the piece. Pin and stitch up the the inner sides, using a blanket stitch to control the raw edges.
Flip the whole piece over so you are looking at the underside. Pin down the edges that will go across the top of the rack and sew with a zigzag or similar stitch to control the raw edges.
Now your panniers will look kind of like panniers! If you don't want to add flaps along the top, you can skip to the end to see how to add ties which will secure the pannier to the rack frame.
Step 5: Prepare the Flaps
Hem under the raw edges on the entire flap piece you cut out earlier. It's just a square, but you should use a zigzag or similar stitch to control the raw edges and prevent raveling.
I used simple ties to secure my flaps. If you want to do something else like buckles, the same basics on how to anchor the straps will hold, but of course the hardware will be different. Make sure you have enough extra strap to tie, and stitch your strap on along the entire top flap.
Step 6: Attach the Flaps
Lay your base piece out as flat as you can and center the flap piece on top of it. Pin securely as the piece is going to be pretty bulky by now and you don't want it to slip! Since I plan to thread my spring-loaded clamp through a gap between the flap piece and base piece, I only sewed the long way where the pins are in the photo, but if you will be attaching differently you can feel free to change it up. I used a zigzag stitch for extra strength, but since there are no raw edges and this stitch will be visible, you can use whatever you're most comfortable with. Tip: I found it easier to tuck the flaps into the bags so they'd be out of the way while sewing.
Step 7: Attach Flap Ties
To measure where the flap ties should go, make the bag as flat and centered as you can with the top edge snug against the seam we made in the last step. Lay the flap over the top and make that flat too. Mark where the edge of the flap is and where the ties hit the bag fabric, like I did in the close-up shot.
Add your lower tie to the bag with enough extra length to be secure (or to look nice, if you have extra). Use your mark as a guide and only anchor the lower tie up to the point you marked - if you anchor higher, you won't be able to close your bag quite as nicely when it's empty.
Do this for all 4 ties.
Step 8: Try It on and Add Stabilizing Ties
Finally! Try the panniers onto your bike rack, and take a marker or pincushion with you. When it is sitting on your rack the way you want it, mark places you think you need to secure. It is VERY IMPORTANT to secure your pannier properly, especially to the side supports on the rack! You don't want your bag of groceries swinging and getting caught between your rack and your wheel. (Trust me....)
At each place you marked, stitch on a tie with a zigzag or something for strength. This is the last step! Take the panniers back to your bike rack and tie on your newly added ties, making sure it's on there nicely.
Step 9: Enjoy!
These panniers worked great for groceries. I was able to carry heavy beans and peanut butter, fragile tortilla chips, and refrigerated goods like cheese, milk, and beer without items getting squished by bungee cords or exposed to a warm salty bath of backsweat! The size I chose didn't seem very big, but the 3" width really made the bags roomy.