Out of Concrete and Drudgery Come Canoes That Float

it’s not straightforward creating the unsinkable out from the unthinkable.

But at the National Concrete Canoe Competition, civil engineering students use a material that is normally the stuff of dams and parking garages to build a 20-foot-long craft that will float even if completely swamped.

To do so, they replace the gravel and sand of conventional concrete with exotic materials like glass spheres. The result, to judge by the finals of this year’s competition, where 23 teams of 10 or more students gathered at the University of Illinois here, is a concrete that is exceedingly light and, with added fibers, strong as well.

But as the team from the University of Texas at Tyler found out, it is not always strong enough.

On Saturday, after two days of being judged on their engineering know-how and the quality of their final product, the students took to the waters of a nearby lake for races that would count for 25 percent of their overall score. Amid the excitement and noise — the Mississippi State team had brought along cowbells for the occasion — there was also heartbreak, when the Texas-Tyler canoe suffered what engineers soberly call catastrophic failure. That is to say, it cracked in half.

“We were just paddling along and suddenly I heard a pop” said Marco Weider, a captain of the team, who with his teammate was able to get the canoe to shore before it broke in two. With the help of students from other teams, they spliced it back together with large amounts of duct tape.

The annual competition has been run by the American Society of Civil Engineers for more than two decades, and is sponsored by companies and trade groups like the American Concrete Institute.

At a time when the nation’s approach to science and engineering education has come in for criticism, the contest is a supplement to conventional teaching, giving students a sense of what a civil engineer’s life is like after graduation.

“It’s an experience these students can get that they can’t get in a class,” said Corey L. Haeder, one of five judges for the competition and chief engineer of a concrete firm in Maple Grove, Minn. (The engineering society also runs a competition in which teams each design and build a small steel bridge.)

It also looks good on a student’s résumé. Sarah Smith, a captain of the Mississippi State team, who just graduated, said she was convinced a main reason she was hired by a civil engineering firm in Jackson, Miss., was because of her concrete canoe work. Her employers, she said, “knew what kind of time and dedication goes into this.”

The teams spend most of the academic year designing and building their canoes, treating the task like a real-world project. They start by picking a theme and a name, and then put leaders in charge of areas like structural design and analysis, concrete mix design (kitchen mixers come in handy for making test batches) and construction (the concrete is usually molded in a marathon session that can last the better part of a day). Most teams also put someone in charge of training the engineers to be effective paddlers.

According to Serji Amirkhanian, a judge and a former civil engineering professor atClemson University who is now a consultant, the best teams do not necessarily have better concrete or structural designs. “It’s not a mystery,” he said. “The concrete has to be lighter than water.”

Rather, the winning teams are usually the best organized. “It takes somebody within the team to take charge,” Mr. Amirkhanian said, and persuade others to do the more thankless tasks, especially sanding the surface of the canoe after the concrete has hardened.

“Nobody wants to sand,” said Mr. Amirkhanian, who while judging the canoes on Thursday ran his hand along each one to feel how smooth it was. “But you need somebody telling others you have to sand for hours and hours.”

Even on a team like that of Cal Poly San Luis Obispo, which won the title the previous three years and finished in the top five for four years before that, students will try to avoid that particular job. “You’ll see people taking out the trash, mopping the floor,” said Thomas Wong, a captain. “Anything but sanding.”

Still, San Luis Obispo does a lot of sanding — 350 hours, Mr. Wong estimated, out of a total of 6,000 spent on the project — and it shows. Their canoe, called Sentinel after the famous domed rock at Yosemite National Park, looked like it was made of porcelain rather than Portland cement.

It had plenty of other advanced features as well — including seven post-tensioned cables running the length of the hull, to give the concrete more strength. And in keeping with the canoe’s theme, the team had created bas-reliefs of the Yosemite landscape on the inside, and cast a pine cone and branch on one of the gunwales.

It was all very elegant, but in the end San Luis Obispo finished fourth. The title was taken by the only Canadian participant, École de Technologie Supérieure, an engineering school in Montreal, that produced a beautiful boat, Savannah with silhouettes of African wildlife on the side.

With its broken boat, Texas-Tyler finished well out of the top five. The team had selected a golf theme, and had cast golf-ball-like dimples on the side of the canoe, but Mr. Weider, the captain, did not think they were the cause of the problem. He said the team had displayed the canoe on Thursday atop a single golf-tee-shaped pedestal (made of concrete, of course) and that may have caused extra stress.

In fact, said César A. Constantino, another of the judges, on Thursday they had noticed that cracks were developing in the boat. “We saw it coming,” he said.

But Mr. Weider was almost fatalistic about the damage. “It’s concrete,” he said. “It’s going to crack.”