Aerofoils & Audi – The Story Behind the e-tron foil
How a basement idea became the world's first jet-driven eFoil. The story of Aerofoils, its connection to Audi, and what still defines the product today.
Search for the Audi e-tron foil and you'll quickly find the specs: jet drive, whisper-quiet operation, carbon construction, no exposed propeller. What's harder to find is the story behind it. How does a product come into existence that had never existed in that form before – and what connects a Bavarian startup to one of the world's most iconic car manufacturers?
Two Worlds, One Idea: Water Meets Aviation
Franz Hofmann was an electric vehicle developer at Audi. Windsurfing, kitesurfing, paragliding, speedflying – water sports and the air were his counterweight to engineering work, and deeply intertwined with everything he did professionally. When he first stood on a hydrofoil in 2014, the thought was immediate: an Audi for the water. An electric vehicle that delivers the same precision and quality on water as a car on the road – controlled, quiet, efficient. And at the same time, a chance to visibly expand the e-tron family and demonstrate what was technologically possible: lightweight construction, aerodynamics, a new lifestyle on the water.
From that idea, Hofmann reached out to Christian Rößler in 2014 – and laid the foundation for what would eventually become the Audi e-tron foil.
The Man Who Designs Aircraft – and Saw a Hydrofoil as a Plane for the Water
Christian Rößler is no ordinary engineer. He won the German championship in model aviation multiple times, went on to become world champion, and ultimately set a world record. At university, he taught aircraft design and developed his own innovative constructions. He founded AKAModell, a student association that competes in model aviation and has built research aircraft for partners including Airbus – test beds for technologies that push the boundaries of what's possible in aerospace.
When Hofmann, together with Rößler's brother Hansi, approached him with the idea of a carbon fin for kitesurfing, Rößler was initially skeptical. But then it clicked: a hydrofoil is essentially an aircraft for the water – and eFoiling, gliding above the surface, is the natural next step in water sports. Aerodynamics, materials, structural principles – everything he had built over two decades in aviation was directly applicable.
Their first joint project was carbon fins for kitesurfing. They worked. Well enough to keep going.
Two Very Different Schools, One Shared Goal
What defines Aerofoils to this day is the combination of two very different worlds. Hofmann brings water sports experience and a deep grounding in the automotive industry – the knowledge of how series production works, how automotive-grade quality is achieved, how a product needs to be built to hold up in real-world use. Rößler brings aviation: lightweight engineering, aerodynamics, and the relentless pursuit of getting every last bit of performance out of every single component.
'I come from the water, he comes from the air,' as Hofmann puts it. That combination is precisely what makes the difference.
The Idea Everyone Said Couldn't Work
Conventional eFoils use an open propeller – visible, spinning, in direct contact with the water. The principle works, but it comes with an inherent risk: exposed rotating parts in a sport where falls are part of the deal.
Rößler and Hofmann wanted a different solution. A fully enclosed jet drive, integrated into the board's mast – no propeller in open water, no rotating parts outside the housing. The system draws water in, accelerates it internally, and expels it in a controlled stream.
The problem: many considered this too inefficient to be viable. Rößler wasn't deterred. The answer lay in the precise application of aerospace principles to fluid dynamics in water – two decades of expertise, called upon at exactly the right moment.
The result: quiet, efficient, free from the drag of protruding components. And with a safety profile that remains unique in the eFoil market to this day.
From the Basement to the World Stage
Development started in a home basement. Early prototypes, tests on Bavarian lakes, iterations on materials and construction. Carbon components throughout – because aviation engineering knows no other material for these demands. A board built as though it came straight out of an aircraft factory.
The concept was pitched to Audi – and was met with genuine enthusiasm. Design and innovation management teams offered their support, and dedicated workshops were set up for the foil. Together, the product was presented at Kiel Week, CES in Las Vegas, and the LA Auto Show. It was now called the Audi e-tron foil.
Hofmann describes this phase as a momentum unlike anything he had experienced in any previous project. Customer demand was so strong that it quickly became clear: this product wasn't meant to stay on a trade show floor – it needed to be available to everyone.
From Project to Company
In 2017, Hofmann and Rößler founded Aerofoils GmbH as an independent spin-off. More flexible, more agile – with a clear mission: to build the best eFoil in the world and make it genuinely accessible.
What became known as the Audi e-tron foil is today the foundation of an entire product family. Adventure, Performance, Competition, Hyperfly and Airfly cover different volumes, riding styles and entry levels – from the inflatable Hyperfly at 230 litres for a relaxed introduction to the 73-litre Competition for experienced riders. All of them share the engineering principles that went into the very first foil built in that basement.
The Next Chapter
In 2025, Aerofoils became part of the Rosenxt Group – one of the world's leading technology groups. For the company, this means greater industrial reach, improved scalability and a long-term R&D perspective, without compromising the standards that have defined the product from day one.
The Audi e-tron foil is the answer to a question two engineers asked themselves at the water's edge in 2014: what if you built an electric vehicle for the water that combined the efficiency and precision of an Audi with the aerodynamics of an aircraft? That answer – a jet drive many thought impossible, in a product that went from a basement to the world stage – lives on in every board Aerofoils builds.
This is only the beginning.
FAQ
What is the Audi e-tron foil?
The Audi e-tron foil is an electrically powered hydrofoil board, originally developed in collaboration between the Aerofoils founders and Audi, and presented under the e-tron foil name at events including CES in Las Vegas and the LA Auto Show. It was the first eFoil to feature a fully enclosed jet drive rather than an exposed propeller.
Who developed the Audi e-tron foil?
It was developed by Franz Hofmann and Christian Rößler. Hofmann worked as an electric vehicle developer at Audi and brought the water sports and automotive background. Rößler is a model aviation world champion and world record holder who develops his own aircraft designs at university – he contributed the aviation engineering perspective.
What is the connection between Aerofoils and Audi?
The idea was born during Hofmann's time as an Audi developer. The foil was presented jointly with Audi at international trade shows. Given the strong demand, Hofmann and Rößler founded Aerofoils GmbH in 2017 as an independent spin-off, to bring the product to series production and make it available to everyone.
What makes the jet drive of the e-tron foil special?
Instead of an open propeller, the e-tron foil uses a fully enclosed jet drive integrated into the mast. Water is drawn in, accelerated internally, and expelled in a controlled flow. The result: near-silent operation, reduced drag, and a significantly higher level of safety – no exposed rotating parts in the water.
Which Aerofoils models are available today?
The current product family includes five boards: Adventure, Performance, Competition, Hyperfly and Airfly. They cover a range of volumes, riding styles and entry levels – from the inflatable Hyperfly at 230 litres for a relaxed introduction to the 73-litre Competition for experienced riders.
