Same panniers mounted to a fatbike.

Waterproof panniers

Updated May 2022

Here’s a brief video outlining the third pair of waterproof DIY I’ve welded up from nylon TPU. Several thousand kilometres of successful bikepacking on the second pair have been incorporated into some minor design tweaks such as a compression weather cover for the roll-top closure and simplified single-strap attachment system. This pair of relatively high volume panniers (~15 litres each) came in at around 550 grams as I incorporated extra layers of TPU fabric at key wear and stress points, and added welded heavy duty D-rings to allow the straps to be easily replaced in the field without tools . I adopted a 20,000 km mindset in the design and construction of this pair of panniers, hence the slightly higher weight. Version 2 with similar volumes weigh about 375 grams for the pair and do not have a weather cover. It’s worth noting that V2 continue to perform well and have proven extremely tough and durable through some challenging backcountry trips.

The panniers are designed to secure near the rear axle level which lowers the centre of gravity relative to typical panniers. My MSR Hubba NX loads vertically and then sits almost entirely below deck of the DIY rear rack. Width of the entire system is less than 18″ on the fatbike and 17″ on the 29’er.

While this example is welded TPU the same design elements work very well with sewn DIY systems.

February 2020

DIY waterproof panniers pictured on a 29'er hardtail.
DIY waterproof panniers pictured on a 29’er hardtail.
Same panniers mounted to a fatbike.
Same panniers mounted to a fatbike.
The single strap on each pannier both secures and compresses the contents.
The single strap on each pannier both secures and compresses the contents.
Final weigh in of the completed panniers.
Final weigh in of the completed panniers.
Welding the carry handle.
Welding the carry handle.
Attaching the carry handle.
Attaching the carry handle.
Welding the lower stiffeners to the blue double faced TPU saddle and weather/compression flap.
Welding the lower stiffeners to the blue double faced TPU saddle and weather/compression flap.
Back side of compression flap just prior to welding the blue TPU into place. This design incorporates a full width pocket to store the excess strap. I usually tuck it into the front edge of the flap which maintains a narrower back profile for hike a bike.
Back side of compression flap just prior to welding the blue TPU into place. This design incorporates a full width pocket to store the excess strap. I usually tuck it into the front edge of the flap which maintains a narrower back profile for hike a bike.
Completed pannier ready for the attachment of other components.
Back view of a pannier prior to attaching other components.
Attaching the protective back layers with integrated D-ring for the strap.
Attaching the protective back layers with integrated D-ring for the strap.
Inside and outside of a pair of panniers
Inside and outside of the pair of panniers.
Marking prior to welding the box corners.
Marking prior to welding the box corners.
Punching holes for the KAM Snaps that close the roll-top.
Punching holes for the KAM Snaps that close the roll-top.
Cut materials for a pair of panniers.
Cut materials for a pair of panniers.
Final welding of the compression flaps taking care to not fuse the TPU to the adjacent layer.
Final welds on the flap, taking care to not fuse TPU in the wrong places.
The area immediately behind the buckle is open on one side to allow the flap pocket to be self-draining.
Welding the compression flaps together.

February 2020 – This project was a result of a first attempt at learning how to thermally bond different types of TPU coated nylon. These two products were 115 GSM (3.4 oz) Heat-Sealable Ripstop Fabric: Yellow and 190 GSM (5.6 oz) Ripstop Fabric, TPU Both Sides . While they’ve not had the extensive testing of other ideas on this site, the first few hundred kilometres have been very positive. Finished weight is just under 400 grams for the pair with all mounting straps, and they’re likely overbuilt by about 10%. Each bag is 10 cm deep, 20 cm wide and 50 cm tall (open) and 40 cm (closed with 4 folds) for a nominal volume of about 8 litres each. Effective working volume is ~9 litres. The laminated fabric is still easily opened and closed in the -30’s C. This posting is intended to be a DIY thought-starter not a detailed description.

An overnighter with the new bags.
Completed bags mounted with a loop on the left bag for the rear light
Just need to add the other bag and straps
Finishing the top edge of the bag
This shows the 10cm welded overlap at the back panel of the bag
First bag welded to the saddle piece
Deciding where the straps go
Attaching the saddle to the bag
Don’t do this! Always use bakers paper.
Ended up removing this full length strap as it was too hard to close the bag.
Finished open bag. The buckles are reversed on the other bag so that they can be clipped together. For the next version both buckles will be of fixed lengths. Like commercial drybags! 🙂

This was a very time consuming project. Largely due to laminating the two fabrics together. The bags have shown no wear from both singletrack riding and loading into trucks. The only sewing was to attach the Omnitape straps to panels which were then welded to the bags, and sewing the buckle closures on.

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