Some time ago I made a post about Big And Cheap: DIY Cargo Bike Bags. On that post I noted on the build sheet this last item:
Therm-a-Rest Classic Foam Pad Amazon 29.95
And then never mentioned another word about it. I still ignored it in the Cheap DIY Cargo Bags: Update follow-on post.
So, that item is actually sort of a big deal for these bags. Why? Because the padding lines the inside of the otherwise floppy ol’ canvas parachute bag and gives it a soft but firm structure. It also of course pads the interior so your carton of eggs stands a better chance of making it home in the same number of pieces it started out in at the grocery store.
Without further ado: Here’s a look at the end result:
And here’s what it looked like before I took a knife to it:
This is a “Therm-a-Rest RidgeRest Classic Foam Camping Sleeping Pad” in its Large size, which is 77″ long by 25″ wide. The important measurement is the width: 25″. Thats only 1″ wider than the measured 24″ width of the Rothco Parachute Bag we are using for this project. In actual practice, stuffing it into the bag, the width is perfectly sized to the bag.
What about length? Well, I found all you have to do is cut one of these sleeping pads in half, widthwise. This will give you two 25″ wide by 38.5″ long pieces. That 38.5″ is pretty much perfect insofar as lining three sides of the bag (rear, bottom and front face).
Having this sturdy but padded liner inside the bag, you can pile stuff on inside and the bag retains its squared off shape. Further, when using the straps to lift up the bag off the lower rack, the liner allows those straps to carry some of the bag’s weight without flopping down onto the rack in its center. Without the pad as a liner, none of that good stuff happens.
Here are a couple of shots of the bags, empty, and folded up. Here again the pad on the inside gives these monstrous panniers shape so they can fold up and stay neat/tidy.
You can see from the pics above how useless those big straps would be without some sort of internal structure (also notice these are still the early 2″ straps). That internal padding is crucial to making these bags work. Now lets look at the bags loaded:
See that grocery cart in the background? Well, it was mostly full and now its loaded up into the Mongoose. Filling both the 25L (each) front panniers and these almost 77L bags in the rear. Those bags are still well-loaded but as you can see by no means full. They are loaded mostly with 2L juice bottles, a case of 500ml coca cola bottles and a slew of soup cans and such. With all that weight, the straps can still hold the bags up and partially off the lower rack and retain their shape (although I did add a third 2″ strap in the center to supplement the two outer 3″ straps… this load was *heavy*).
So… thats why you need the pads.
Finally, what do these bags look like when truly, fully filled out? Recently I took some old XL sleeping bags out of the house. A city park was midway to the drop off point and I pulled over for a quick set of pics.