Sink or swim for concrete canoes
by Linda Hein
Racing a concrete canoe sounds virtually impossible when we think of concrete in its usual form - weighty, solid and eminently sinkable.
But for third and fourth year civil engineering students at UniSA it’s the execution of a simple engineering principle, as well as a whole lot of fun.
A cheering crowd on the banks of Mawson Lakes saw the students race their concrete creations against a University of Adelaide team to prove that concrete can indeed float on water.
So how does it work?
This year’s team leader, third year civil engineering student David Ewers, says that it’s all about water displacement and relating the weight of the water to the volume of the canoe.
"We use the Archimedes principle, which says that the greater the volume of the boat the more water it displaces, which means it is more likely to float," he said.
In layman’s terms the concept is much like floating an empty ice cream container, as opposed to a full one which would sink straight to the bottom. And what works for ice cream also works for concrete.
The group of eight students worked for almost eight weeks over the summer break to design and build the new canoe, ready for racing in the first week of the uni year. A canoe used in last year’s inaugural race was also freshened up for a second outing.
Ewers said the team used a lightweight materials supplied by industry sponsors Adelaide Brighton Limited, BASF Chemicals, Bianco Precast and Silka, and foam at either end of the canoe for added buoyancy if the canoe fills with water.
"We don’t use normal aggregate (the stones and pebbles in concrete) but instead use lightweight fibres which are as strong as steel," Ewers said.
"We also use a sand replacement, or ‘e-spheres’, which are small balls made of carbon fibre plastic mix to keep the canoe lighter."
For Ewers, the incentive for getting involved in the process is the hands-on practical experience.
"This gives you the chance to learn project management skills and see the teamwork involved in pulling it all together. There are also the industrial contacts you gain when deciding on materials. You form relationships and learn how to relate to industry.
"It’s also great fun."
UniSA won two of the four races, in what was a tight battle for the overall winner’s shield, judged on design and materials, as well as race placings.
While the shield this year went to Adelaide Uni, Ewers said the UniSA teams are ready to take it up another notch for next year, with an even bigger and better event and plans to mentor budding canoe builders.
"It was very close and even though we didn’t win this year, we were very competitive. The response has been fantastic and everyone enjoyed the day, so we’re definitely keen to give it another good try next year."