HTWKjak

Segmented concrete canoe

Under the direction of Prof. Dr. A. Stahr and Dipl. Ing. M. Theuer, a student team of HTWK Leipzig has developed a canoe form, on the basis of which two concrete boats were built.

With the „Weiße Elster", the students dared to innovate in order to be among the leaders in the "Best Construction" competition. The boat consists of three segments and can therefore be easily transported in a minibus. The real feature lies in the cutting line of the division. Due to a spatially curved wave cut a displacement resistant joining of the segments is possible. In the longitudinal direction, a zigzag lacing provides the necessary grip to the connection. This ensures a strong and at the same time watertight connection, which could be produced by the students themselves.

The boat "BUGAtti" was traditionally made in one piece to get a sturdy yet light canoe for the athletic competition.

Keywords: lightweight design, fiber-reinforced concrete, double curvature, tech.connection technology, joint, scalloped edge, concrete canoe competition

Connection details

The connection of the canoe segments had to be designed as a rigid connection for the transmission of moments, shear and normal forces in order to ensure the buoyancy of the boat hull. By following the hull geometry an undulating cut automatically formed a toothing of the segments, which simultaneously prevents their vertical as well as horizontal displacement and inducing the resulting lateral forces directly into the opposite boat wall. With the large-area load application, a material-oriented connection was designed that avoids stress peaks and cleverly takes into account the less ductile behavior of the concrete. The executed zigzag lacing generates the advantages of placing the force application points sufficiently far away from the joining edge, allowing compatible curvature radii and avoiding local overstrain. This, due to the double curvature of the hull, spatially acting clamping system allows a bias of the butt joint. This prevents a gaping groove in the tension area the bending-stressed connection.

Implementation

A major advantage of the connection technique described was its compatibility with respect to manufacturing tolerances. In addition, only one doubly curved formwork form had to be produced, since in the second casting section the hardened end segments of the canoe were used as edge shuttering and the middle segment was directly concreted against them. Geometric inaccuracies in the first concreting section were hereby compensated and ensured the greatest possible form fit. To seal against pressurized water, two rubber seals made of commercially available window sealing tape were additionally installed.

Competition

In 2015, the HTWK team participated with both boats in the 15th concrete canoe regatta in Brandenburg on the Havel. With the "BUGatti" the ladies team reached the 4th place. The boat "Weiße Elster" secured second place in the competition category "Design".

Team

processed by:

M. Betsch

C. Bösl

P. Diefenthaler

L. Hertwig

T. Hirsemann

L. Hoffmann

K. Kasprick

J. Teuchert

supervised by:

Dipl.-Ing. Michael Theuer