Since 2005, ETH has consistently taken part in the concrete canoe regattas with great success, and this year ETH won the 1st prize for Design Innovation for the 3rd year in a row. SkelETHon, the 114 Kilogram 3D printed concrete canoe, was a collaboration between DBT – who provided the computational design and digital fabrication expertise – and the PCBM Group – who developed the concrete mixes and processes used in the construction of the boat.
Every other year, the two-day long concrete canoe race takes place in a city in Germany, bringing together a fun sporting competition and the latest advancements in concrete technology. This year, over 1000 participants from universities from all over Europe raced 90 boats made entirely out of concrete on the Rhine river in Cologne. The teams competed for the lightest, fastest, most beautiful, and for the most coveted award – best design innovation.
In the past, the Concrete Canoe Regatta has already served as a prototyping framework for emerging research projects at ETH, such as Mesh Mold and Smart Dynamic Casting, which have become in the meantime successful, mature researches. This year, Free Formwork, a research project developed at DBT was used to build a boat that was highly praised by the jury for the unique design approach.
The four meter-long boat has a stiff steel fiber-reinforced concrete inner skeleton, covered by a two to three millimeter-thick waterproof concrete skin. The skeleton is designed using topology and shape optimization algorithms which reduce the material of traditional canoe design and redistribute it in a skeleton-like structure in order to maximize the stiffness of the boat.
For the fabrication of this skeleton, a submillimetre thin plastic formwork was 3d printed and cast in ultra-high-performance fiber-reinforced concrete. The formwork for the entire boat weighed just over four kilograms and precise, high-resolution surface texture, with details as small as half a millimeter, was transferred to the concrete skeleton to increase the contact area with the outer skin.
The construction process made possible a highly complex concrete skeleton with bones as thin as 15 millimeters in diameter which would be impossible to fabricate with any other digital fabrication technologies. 3D printing, a precious fabrication process, was used minimally but had a significant impact on the overall design.