Concrete canoe racing began in Germany in 1986 when the first competition was held in Limburg an der Lahn. Competitions were held every two years until 2002. Then after a three year lag, the competition was reinstated in 2003 in Heidelberg. When the 11th Deutsche Regatta was held in 2007 in Hanover, the top three finishers in both the men's and women's races automatically qualified to paddle against the world champions at WM 2007.

Fundamentally new concepts of building canoes

By 2011, over 90 teams were registering for the German nationals, with participants coming from a number of other countries including Switzerland and the Netherlands. In 2014, Dresden reciprocated and fielded the lightest entry in the Netherlands.

As in past years, a group of students from ETH Zurich, Switzerland, competed in the German "Concrete Canoe Regatta", this year taking place in Brandenburg/Havel in Germany. The challenge of building a boat and surprising the jury with fundamentally new concepts and innovative ideas every two years pushes students to find new ways to convert cement, water and aggregates into a floating structure.

This year, two groups of three students in civil engineering built two boats using robotic fabrication. Prof. Robert Flatt of the Institute for Building Materials at ETH invited his students to implement two ongoing research projects in this field: Smart Dynamic Casting and Mesh Mold.

Merging of reinforcement and formwork

Mesh Mold is a project of the chair for architecture and digital fabrication in collaboration with Sika Technology AG. The technology aims to merge the two conventionally separate, labor and cost-intensive aspects of concrete construction: reinforcement and formwork. This not only allows a more efficient use of material, but also enhances the fabrication of geometrically complex load-bearing concrete structures by using the high spatial coordination of robots.

The 3D model was downloaded from the internet

The shape of the "Queen ElisamEshTH" is the one of a traditional canoe, an already existing 3D model that was downloaded from the Internet. A 3D printer printed the plastic mesh mold for the boat, which was reinforced with carbon fiber due to the poor strength of the material and filled manually with two different types of concrete: one with lightweight foam glass aggregates and another with aerogel aggregates and a white cementitious binder.

Concrete quality was crucial

Smart Dynamic Casting (SDC) is a project of Gramazio and Kohler Research with similar motivation: finding ways to efficiently build freely shaped concrete elements using a digital means of fabrication. The concept is a sliding formwork with the ability to change its shape during the process. The shape of the canoe was determined first of all, and then a special formwork was designed for it. The building process had to be carefully planned and optimized over the course of many trials.

Concrete quality and rheology were crucial. Pressure and friction changes inside the casting on top of the thin wall challenged the team to the last centimeter of production. A structure over four meters high was achieved in two days, setting a new height record for the young SDC technology. The rear and bow of "S2D2©" were added by using conventional casting.

The teams from ETH Zurich have won several prizes since the competition first took place. Two years ago, they received an award for their on-site canoe that was built the very morning before the race. This year, "Queen ElisamEshTH" won the prize for engineering and "S2D2©" (at almost 300 kg) the award for the heaviest boat in the race.

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