Rowing Stones"


Boys' Life, September, 1999, pp. 18-19.

Scout Program: Engineering

Building a concrete canoe takes more than simply tossing some mix into a mold.  It takes smarts.  It takes problem-solving.  It takes an engineer.

Engineers can take ideas -- often seemingly impossible ideas like building a canoe out of concrete -- and make them work.  They can make cars that run on electricity, houses that heat and cool themselves and huge jumbo jets that seem lighter than air.  Next month, Scouts whose troops pick the suggested program theme of Engineering can participate in an Engineering Outing.  There they can build or demonstrate all kinds of projects: model rockets, solar-powered generators-maybe even a concrete canoe.  Get complete details in 'Troop Program Features" Volume I (BSA Supply No. 33110; phone 800-323-0732).

College engineers create canoes out of an unlikely material: concrete

Most of the canoes that people use today are made by bending aluminum or other light but strong materials.

Like concrete.

Yes, the stuff that sidewalks and driveways are made of also can float.  All it takes to make a concrete canoe: cement, a mixing agent, carbon fiber and a bunch of college civil engineering students like Brad Putman. Brad and his Clemson University team competed against 24 other schools at the 1999 National Concrete Canoe Competition in June in Melbourne, Fla.

Aye, Captain

The Clemson team worked for 10 months to build The Sequel.  "It's a challenge to design a good canoe," Brad says.  Nate Tarbox from Florida Tech agrees, "A lot of boats either sink or don't survive their swamp test."

That's the part of the competition in which teams must hold their boats under water -- called "swamping" -- and hope the boats rise and float after they are let go.  "One team's boat cracked in half during their swamp test," Nate says.

Putting the Pieces Together

"Instead of using sand or gravel as an aggregate [mixing agent], we use tiny glass bubbles," Brad says.  "Only one tenth the weight of water, the micro-bubbles allow the concrete to float."

The students then spread the concrete mix over a mold.  'Thatís where the design challenge comes in.

"Some boats have a wide, flat hull, and others have more of a V-shape to them," says Dr. John Gilbert, civil engineering professor at the University of Alabama at Huntsville.

After the cement was spread over the mold, a reinforcement material such as carbon fiber mesh or polyester was used to keep the boat's shape.  Then the concrete cures for as long as 28 days in a temperature- and moisture-controlled environment.

The boats ranged in size from 15 to 22 feet long and the shells were 0.25 to 0.75 inches thick.  The canoes weighed between 75 and 180 pounds.

Racing Days

The racing events on the third day of competition included distance races, sprints and, for the first time, a four- person co-ed sprint in which teams of men and women paddled together.

"The co-ed sprint added a new dimension," Nate says.  "Having four people in the boat, rather than two, made us redesign the canoe."

Rather than using a shorter, lighter boat, engineers had to add length and weight while maintaining stability.  "It really made all of the teams take a new look at the way they were designing," Nate says.

The Champs

By the time of the co-ed race, the Clemson boat had been through a lot.  Near the end of the 200-meter sprint, water started to fill the canoe.

"I remember Brad yelling, 'Push harder,' and then realized that I was going underwater," teammate Lissa Henkel says.

"We finished the race second, with the boat completely underneath the water," Brad adds.  Still, soaked to the bone, the Clemson team won the overall competition.

AP Photo by Craig Bailey