A technological challenge, the canoe made of concrete !

The sector of civil work is not much propitious to real implementation of projects where students actually build a model. The size and the cost are the often obstacles.

For two years, some Civil Engineering Departments of Technology Institute in France have started to build concrete canoes. This may surprises at first sight, but far from being absurd. The biggest barges in the world are in reinforced concrete. This was the case of elements of the artificial port of Arromanches built in the port of London and hauled to Normandy to ease the disembarkment of men and materials after the 6th of June 1944. Another more recent example is the N’Kossa barge at the open sea of Gabon, serving as floating plant for raw oil processing.

But the present project is a reasonable size project consisting to build a concrete canoe capable to carry two passengers on the water in good safety conditions.

Summary of the specification :

• The material used to build the shell of the canoe must be concrete with or without reinforcement. The definition of concrete is a mortar of passive granules, hydraulic biding agent, water and additives. The reinforcement may be steel, glass fibre or vegetable fibre.
• The overall dimensions must not exceed 6mx1m
• The canoe must be unsinkable with added floatation cases.

The origin of such a project comes from Canada where for years inter-university concrete canoe contest takes place on the river of Saint Laurent. The decision to take part in the contest of the city of Bourges - France in 2002 was taken by the Civil Engineering Department of Technology Institute of REIMS. In the teaching programme of second year there are projects of self works of 150 hours framed by teachers. At the end of the learning year, students must during three weeks realise their projects.

Based on constraints imposed by the contest rules, such as dosage of additives, maximum dimensions and the number of passengers, the students tried to realise a boat which can be or not reinforced. Steel is considered but rapidly abandoned because of its weight.

Then hemp and glass fibre are quickly considered as usable in the student’s project. After these decision making, they entered into contact with construction companies in the region which make extensive use of these materials.

The shape of the canoe is determined by discussions with members of canoe kayak clubs considering problems of floatation and stability.

Main points solved by students

• Choice of the reinforcement material for the shell :
  The hemp and glass fibres are not common used materials in the building industry. Nevertheless, The producer of hemp, “La Chanvrière de l’Aube” committed itself to supply the students with hemp fibre and another company, “Partner Engineering” could provide glass fibre and G.R.C technology.
  Due to lack of information and difficulties of implementation, the hemp was abandoned quickly.
  At the opposite, the glass fibre and G.R.C. are commonly used by Partner Engineering to produce flat panels and decoration elements for building. The students have got all technical information such as dosage, additives, mechanical resistance, shape constraint, etc. from the Technical Department of the company.
  
• Shape of the canoe :
  The students had borrowed a glass fibre made canoe from the canoe kayak club of Sillery in order to study the shape of the projected boat.
  The 3D profile was then digitalized using AUTOCAD.
  The volume of the displaced water then was determined by the software to study the stability and floatability of the boat
  
• Mould construction :
  The mould was built reproducing the outside surface of the canoe. The G.R.C. was cast in the mould and floaters were incorporated at the upper side.
  
• Transport and handling :
  Very quickly these constraints were taken into account at the very beginning of the project. The problems to be solved were the road carrier and handles for the launching.
  
• Other aspects of the project :
  The main goal of the project for the students was not only to build a concrete canoe, but to win the contest. So they had also to learn how to use the boat and to improve their skill in canoeing.