Concrete canoe

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A concrete canoe is the term for a canoe made of concrete, typically created for an engineering competition.

In spirit, the event is similar to that of a cardboard boat race—make the seemingly unfloatable float! However, since concrete and other poured surfaces are an integral part of a civil engineer's education, concrete canoes typically feature more development than cardboard boats.

Most ships or boats float because the weight of the water they displace is greater than the weight of the boat (Archimedes' principle). Concrete canoes, however, are actually lighter than water, as required by the rules of the competition. They must pass a test in which the canoe is filled with water and pushed below the surface; the canoe must then resurface in order to qualify for racing. This is possible because, unlike normal concrete which uses sand and small rocks, concrete canoes are created with hollow aggregates such as macrolite and microspheres.

In the U.S., around 200 universities participate in the event every year in 18 regional competitions. The winners of these competitions and up to five second place finishers move on to the national competition, which is called the "olympics of civil engineering." Typically, frontrunners include the University of Alabama Huntsville, the University of California Berkeley, Clemson University, and the University of Wisconsin Madison.

Concrete canoe teams must design their canoes from scratch. Typically they create the shape of the hull with a computer design program specifically made for yachts, canoes, and other watercraft. The shape is optimized for racing. This hull shape is then given to a construction team, responsible for making a mold for the canoe to be formed on. A special concrete mix is designed over several months, emphasizing strength and low density. Finally, on pour day, the finalized mix design is placed on the form, usually about half an inch thick. Teams later spend hundreds of hours sanding and staining their canoes for a nice finish. Scoring in the competition is based on the quality of construction, race performance, a design paper, and a business presentation.

In the USA, the American Society of Civil Engineers sanctions yearly competitions. The 2006 National Concrete Canoe Competition will be held in Stillwater, Oklahoma and hosted by Oklahoma State University.

In Canada, the 2006 National Concrete Canoe Competition was held in Sherbrooke, Quebec and hosted by Sherbrooke University who were also the overall winners.