Apidura Aero Pack System: Packs That Make You Faster

In 2016, Apidura launched the world’s first waterproof bikepacking bags.

 

In 2018, Apidura launched the world’s first ultralight race-focused packs, designed in partnership with Kristof Allegaert.

 

On June 2 2022, we are excited to be able to reveal the world’s first aerodynamically optimized packing system.

 

Packs that make you faster.

Reading time: 6 min
Nol's custom Ridley Kanzo Fast, featuring the Apidura Aero Pack System and Hunt 42 Limitless Gravel Wheels

 

Self-supported bikepacking races require a lot of kit, so carrying capacity and weight are usually put ahead of aerodynamics concerns. Lightweight is in our DNA and we’ve pioneered some of the lightest, most technically advanced packs possible. Our first packs took the Trans Am Bike Race by storm and we’ve since developed fully waterproof and race-specific packs, alongside packs optimised for modern mountain bike geometries.

However, as long-distance single day events, particularly in the gravel world, have grown in popularity and riders have perfected the art of carrying even less for shorter bikepacking events, the balance between carrying capacity and aerodynamics has shifted and we found ourselves wondering if bikepacking packs could be designed to make a bike faster.

Nol van Loon riding in the wind tunnel at Belgian Cycling Factory

The team make changes to the packs in the wind tunnel

Our friends at Ridley agreed. As manufacturers of the world’s fastest gravel bike, they were keen to see if looking outside of the UCI’s rules could help make the Kanzo Fast even faster.

With the project agreed, Ridley delivered an aerodynamics masterclass to our design team to help inform which areas of the bike we should focus on and the considerations we should keep in mind while designing the packs. Aerodynamics are not straightforward or simple and it was an eye-opening experience for the team to understand how even the smallest changes can have a significant impact on how air interacts with an object. Being able to lean on Ridley’s expertise and in-house wind tunnel and CFD (computational fluid dynamics) testing meant our team quickly became well versed in boundary layers and laminar flow and we were able to begin the six-month development process to create the world’s first aerodynamic gravel racing packs.

Baseline tests of typical gravel racing setups showed us that packs that haven’t been aerodynamically optimised could be costing riders up to 17.5 watts at 40km/h – a not insignificant amount. Poor packing could literally cost a rider the advantage of an expensive set of aerodynamic wheels. Even a food pouch could be adding four watts of drag at 40km/h

These baseline tests in the Bike Valley wind tunnel and advice from Ridley’s aerodynamic experts identified a few key locations for likely aerodynamic gains; The top tube, the front of the main triangle, below the down tube and behind the seat tube. These areas would allow us to extend aerodynamic shapes to maintain clean airflow, without the packs hitting ‘clean’ air and incurring an aerodynamic penalty.

With our focus on designing packs that add to the bike’s aerodynamic performance, the only location that was firmly off-limits was the handlebar. Ridley were very clear; it is simply not practical to design a handlebar bag that does not negatively affect aerodynamics… although that’s not to say they don’t have their place beyond this project!

The development of the frame pack

The development of the rear pack

Under Ridley’s guidance, we developed a series of prototype packs for the target areas, pulling in some fresh ideas around direct mounting and openings to streamline the packs and smooth the air flow. A full-day session in the wind tunnel would then tell us which of our designs worked and where there were potential tweaks to be made.

The day started agonisingly slowly. The full setup, with our rider, Nol van Loon of Fat Pigeon, also on the bike, was adding drag at low yaw (head-on wind angles). Something in the way the top tube, frame, seat tube and down tube pack were interacting meant that designs that we expected to be aerodynamic weren’t performing well. Over 16 tests, adding and removing packs, tweaking positions, and even creating a new pack on the fly, the numbers rapidly improved.

Even with a great deal of aerodynamics expertise in the room, it was nearly impossible to predict which changes would work. The only option was to test relentlessly until we found a setup that yielded 16.66 watts of savings at 40km/h. Even at race speed (32.04km/h for Unbound), the packs yielded a 2.4-watt saving and adding our hydration vest to Nol’s setup increased this to 7.67 watts.

 

At such low speeds, these savings are not insignificant and roughly match the savings you would expect from a set of deep-section carbon wheels or a tailored skinsuit. More than that, these savings also add significant storage space to the bike, optimised for easy access on rough terrain.

A view of the wind tunnel computer readout during testing
Wind tunnel results from the 40km/h test showed savings of 16.66 watts

40km/h Aero Test data

Wind tunnel results from the 40km/h test showed savings of 16.66 watts

32km/h Aero Test data

Wind tunnel results from the 32km/h, race speed test showed savings of 2.4 watts for the Aero Pack System, increasing to 7.67 watts with the addition of a Racing Hydration Vest

Wind tunnel results from the 32km/h, race speed test showed savings of 2.4 watts for the Aero Pack System, increasing to 7.67 watts with the addition of a Racing Hydration Vest

Coming away from the wind tunnel session, we had a clear view of what the final packs needed to look like and could work on finessing the designs and improving the functionality. Working closely with Nol, we also knew what he needed to carry and how much space we would need to provide.

As a result of the data-driven design process, the packs are small and complex, creating design and manufacturing challenges we’re not used to. We were able to design out some of the complexity by breaking down challenges and using advanced tools and techniques like 3D printing to smooth transitions and attach packs to shaped tubes. Even so, the Top Tube Pack requires 8 tools to make, which is 5 more than our average pack. We also had to create an entirely new opening that doesn’t rely on a zipper and has a totally flush finish.

-Ross Pugh / Apidura Design Team

Introducing The Apidura Aero Pack System

 

Final development of the Aero Pack System

The Top Tube Pack uses data-driven design cues to hide in the silhouette of the steerer and stem, providing gel storage space with a quick access opening for easy fuelling and refilling at the food stops. The smallest Top Tube Pack we’ve ever made, this pack proves that in the case of aerodynamics, less really is sometimes more.

The Aero Pack System Top Tube Pack

The Frame Pack mounts using a custom 3D printed module that smooths the transition from the frame to the pack, filling the space between the widest parts of the bike frame and the pack. Bolting directly to the frame, the pack is extremely secure and completely hidden from the wind at low yaw. A new opening using TPU and magnets creates a totally flush surface that’s water and dirt proof but extremely easy to access (and closes automatically).

The Aero Pack System Frame Pack

The Rear Pack mounts using a 3D printed module that bolts directly onto the brake bridge mudguard mount and replaces the seat post dust cover for a rock-solid, low-profile mount. As with the other packs in the system, the Rear Pack has an internal bonded structure to help maintain its shape but given it’s unlikely to be accessed on the go, it features a more traditional roll top for flexible storage and to maximise the space available.

The Aero Pack System Rear Pack

Each of the packs features a new fabric design that testing revealed to be 5.7 watts faster than our standard Hexalon at 40km/h.

The design of the packs pushed our technology-driven Precision Crafted approach further than ever before. The complexity of the shapes and the need for smooth transitions and flush mounts pushed welding techniques to their limits and relies on advanced techniques including 3D printing to perfectly match the bags to the frame.

The Apidura Aero Pack System is a one-off concept currently but, as with all Innovation Lab projects, the learnings can be expected to be applied to future products and find their way into existing products where they add significant value over existing processes.