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How To Techniques Concrete Canoes
How To Techniques Concrete Canoes
| Concrete Canoes |
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| Written by Jim Moodie |
| Thursday, 01 November 2001 00:53 |
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How To Paddle An Oxymoron When I worked at a YMCA camp in my undergrad days, one of my responsibilities was to inventory and water test each of the camp’s 40 or so canoes. Most were tried and true (if used and abused) wood-canvas beauties, but there were a few curiosities in the fleet, too. The ancient, all-wood cedar strip, for instance, that had to be soaked in the lake before its half-lapped planks formed a seal. The aluminum Springbok that was only slightly more shapely than a pig trough. And one insanely rockered and round-bottomed banana that could do exactly one thing well--flip over. The weirdest canoe of all, though, was the one made of concrete. This implausible beast resided in the deepest recesses of the boathouse, where it had presumably lain for years. It was cracked and stained. One chipped flank bore the faded words, "University of Toronto." I had no idea how it had made the trip from U of T to the camp, but I pictured a flatbed trailer and a crane. Once, experimentally, I tried to hoist an end, and nearly blew a gasket. The canoe must have weighed 500 pounds. Needless to say, I never attempted to water test the behemoth. I just assumed--and who wouldn’t?--that a concrete canoe, particularly one this hefty, could never float. Concrete, after all, was what we used to anchor the wood and styrofoam floating docks at the camp. The concrete blocks sat at the bottom of the lake. A particularly fierce gale might cause them to be dragged a few feet along the lake floor, but they never, to my knowledge, surfaced. A concrete canoe? It was a contradiction in terms, a metaphor for certain disaster, the nautical equivalent of a lead balloon. I figured this particular cement canoe must have originated as either some kind of demented class project, or an elaborate prank--the sort that engineering students were famous for, like the VW Bug that regularly appeared on campus rooftops at the University of British Columbia. What I’ve learned since is that not only can concrete canoes float--provided the mix is right, of course--but that they can even be effectively raced, achieving speeds of as much as eight mph. They can also be maneuvered smartly through 180-degree buoy turns. And, believe it or not, two normally endowed people can generally carry a canoe of this type without requiring extensive medical coverage. Building and racing concrete canoes is, it turns out, a proud tradition among civil engineering students that dates back to at least 1970. The earliest prototypes, built by a handful of schools, were cumbersome brutes requiring foam flotation to keep them from going down like, well, concrete canoes. A lot has changed since then; more colleges have gotten involved each year and the technology has become ever more sophisticated. This past spring, 250 colleges from across North America entered sleek, trim, intrinsically buoyant "conoes" (my own term, just coined) in 21 regional competitions. And, in mid-June, the winners of those regionals made their way to the 14th annual National Concrete Canoe Competition, an event co-sponsored by the American Society of Civil Engineers and Master Builders Inc., a manufacturer of concrete products. This past year’s NCCC was hosted by San Diego University on June 14-16, with the race portion of the event--teams are also judged on the aesthetics and structural soundness of their craft--being staged on Lake Murray, a reservoir near campus. Students traveled from as far away as Laval University in Quebec City (55 hours of driving for those transporting the canoe) and Clemson, South Carolina (a three-day, 2,200-mile drive), to take part in the challenge. For these teams, a trip to the finals wasn’t just an excuse to see California, but the culmination of countless extracurricular hours spent designing and crafting their "conoes," and preparing to race them in daily paddling workouts. While concrete will never be a viable material for recreational (much less true racing) canoes--it’s just too heavy, and brittle--its use as a boat-building substance is not without precedent or merit. Concrete hulls have long been used to buoy up barges and houseboats, and could make sense for other craft as well. "The case can be made that the best sailboat to travel around the world in would be one made of concrete, because you can repair it anywhere you stop," suggests Travis Davidsavor of the Michigan Tech concrete canoe team. "Only developed countries have [a ready supply of] Kevlar or even fiberglass." Still, many people, myself included, have a hard time getting their minds around the concept of a concrete vessel being supernatant for even a moment, let alone port-hopping around the globe. Archimedes, he of the famous bath tub epiphany, can help us out a bit here. If you paid attention during high school physics class, you might recall Archimedes’ maxim that a submerged body will be buoyed up by a force equal to the weight of the fluid it displaces. In other words, a concrete canoe will float as long as it weighs less than the water it shoves aside. Or, as Benjamin Loveday of the Virginia Tech team succinctly puts it: "Water weighs 62.4 pounds per cubic foot. The concrete has to weigh less." The compound that goes into a concrete canoe is not the quotidian stuff of sidewalks and patio stones. "It’s all about the aggregates you use," explains Alabama-Huntsville’s Stuart Johnson. Whereas construction-grade concrete consists of coarse aggregate, "we use tiny glass bubbles, or micro-balloons, which entrain air into the concrete mix." (Read: make it fluffy enough to float. I personally picture an Aero Bar.) Davidsavor says that the concrete mix his Michigan Tech team came up with is "60 percent the weight of water, so it’s inherently buoyant. We could crush our canoe into a fine powder and it would still float." Not that any of these engineers really want to test that theory. To keep their canoes from being crushed or otherwise mangled, students add lightweight reinforcement materials such as graphite and carbon fiber mesh to the concrete. The concrete is generally applied by hand over a form similar to the type used in wooden canoe construction--a solid mold consisting of plywood cross-sectional pieces, overlaid with strips of wood. "The concrete is the consistency of peanut butter when it goes on," says Joel Sheets of Clemson University, "and we use trowels to smooth it out." Layers of concrete are alternated with layers of the reinforcing material, and "the whole thing is placed wet, so the concrete bonds with itself through the layers of mesh." Once the concrete cures, the team goes to work with sandpaper, smoothing the hull down to a final thickness of a mere half-inch or less. Most of the canoes in the 2001 finals--at an average length of 20-22 feet--weighed just over 100 pounds, which is a far cry from the 400-pound bruisers featured in early 1970s competitions, and not much heavier than some fiberglass canoes of that same era. Still, when it comes to race performance, weight doesn’t seem to be the biggest factor. The top two canoes at San Diego were at opposite ends of the scales: Alabama-Huntsville’s ultralight 76-pounder took first place overall in the competition, but was actually bested in the races by a canoe weighing more than twice as much--Clemson’s massive 180-pound missile. A concrete canoe can actually be "too light," according to Alabama-Huntsville’s Johnson. "In 1998 we integrated balsa wood and had a canoe weighing 49 pounds. We won the national title that year but, to be honest, it wasn’t ideal for racing. The optimum range is 75 to 80 pounds." More important than the weight of the "conoe" is its shape. These future builders of bridges and skyscrapers spend hours studying boat design and are well versed in its arcane language, with terms like tumblehome, rocker, secondary stability, and chine (an angular intersection of the sides and bottom of a vessel, don’t you know) rolling readily off their tongues. Most teams utilize a computer program that is the choice of professional boatbuilders to design their hulls, with some even engaging the services of naval architects. John Winters, a naval architect who designs canoes as well as yachts, has helped a variety of teams over the years. "The University of Virginia was the first team, in 1994, that came to me for a design--which was kind of fun, because I was born in Virginia and they rejected my application when I tried to get into the university." The Virginia squad won the national title that year with the Winters-designed canoe. The challenge in designing a "conoe" isn’t so much the limitations of the material, says Winters, but the "parameters of the race." Conventional racing canoes, he notes, "are relatively easy to design, because they just go straight." Concrete canoes, however, have to negotiate slalom courses, as well as perform well in linear sprints. Says Clemson’s Joel Sheets: "You have to balance straight line speed with the buoy turns. You can’t just have a long straight boat." Most "conoes" are fairly flat (or slightly V) bottomed for stability and tracking, but rockered towards the bow for turning ability. "Conoes" are also unique in that they have to carry four paddlers as well as two. There are three types of races at the NCCC: men’s and women’s two-person sprints, on a 200-meter course with one buoy turn; men’s and women’s two-person endurance races, on a 600-metre slalom course; and a four-person co-ed race. "When you put four people in a two-person boat, it’s a bit of a crapshoot," says Davidsavor of Michigan Tech. "We just take our four smallest, fastest paddlers and hope for the best. In the end, it comes down to communication." Communication is what was apparently lacking for the Virginia Tech co-ed team, which got into a bit of trouble on the home stretch. "We sunk our boat," bluntly states Benjamin Loveday. "Actually, we didn’t sink," he corrects, noting that canoes must pass a submersion test before competing, to prove that they’ll float even when swamped. "We just basically capsized." Rather than have a dreaded "DNF" (did not finish) next to their name in the race results, the Virginia Tech team gamely swam their swamped canoe to the finish line. Paddler coordination and conditioning is, in fact, the biggest key to success in the races. "If the paddlers train a lot, they have a chance of winning even with a slower, poorly designed boat," says Winters. "Speaking as a designer--I always encourage students to train, train, train." This is easier done for some teams than others. As Davidsavor points out, "the water here in upper Michigan gets a bit hard in the winter." His team has been known to take their canoe out on Lake Superior, weather permitting, and they’ve also been known to practice in the university’s pool. "But there’s just space to turn around, really. You can’t do a sprint." The Clemson squad, which has dominated the races for the past few years, trains daily throughout the school year on nearby Lake Hartwell. Videotapes of their paddling sessions are sent to a paddling coach in Minnesota for analysis. Particularly dominant this past year was the Clemson women’s team. "They pretty much outpaddled everyone, including our guys," says Sheets (one of Clemson’s guys). In the endurance race, Clemson’s women had a 20-second lead on their nearest competitor, and clocked a faster time than all but one of the 24 male teams. Jessica Cummings, one-half of this amazing female duo (Mary-Halis Alkis was her bowsperson), credits her team’s success to practice and determination. Her only paddling experience prior to joining the concrete canoe team "was a random canoe trip when I was 10-years-old," but she and Alkis worked hard, getting out on the lake every day at 6 a.m. as well as most evenings. "If we weren’t paddling two times a day, we’d paddle and then run hills, or lift weights in the gym," she says. The races are always the highlight of the NCCC, featuring thrills--like the photo finish in this year’s men’s sprint, with the top five teams finishing a couple seconds apart--as well as the inevitable spills. But the races only make up 30 percent of the final score. The remaining 70 percent is based on the canoes’ appearance and structural integrity (a category known as "finished product"), a display, and written and oral presentations. Alabama-Huntsville, a powerhouse in the mid-1990s, won the 2001 NCCC by a small margin over Clemson--titleholder for the previous two years--with Oklahoma State’s cowboys-cum-canoeists placing a convincing third. As part of the concrete canoe exercise, teams conduct a financial analysis of their project, taking into account materials and hours of labor at typical rates, just as any engineering firm would do in the "real" world. "The price tag on our boat was $140,000," says Michigan Tech’s Davidsavor, with an audible gulp. The value of Laval University’s canoe was only slightly less, at $125,000. Obviously none of these canoes is going to find a market any day soon, nor are the students paid to work on them, but such dollar values do indicate the level of effort put into the projects. Sadly enough, after the competition ends, the canoes are effectively retired--perhaps showcased for a while on campus, or used (briefly) as a practice boat. For all their outward toughness, concrete canoes are not built to last. "These things are a magnet for neglect," says Davidsavor. "Sunlight will deteriorate the finish, water will get in and add weight." During a race, it’s not uncommon for one to gain 10 pounds, he says. A bit of water absorption actually makes a concrete canoe stronger, but too much makes them sluggish and unwieldy. "And if they freeze, they’re dead," he ads. Davidsavor and his colleagues at Michigan Tech have come up with a novel way to send their canoes off to the great construction site in the sky. "We take ours out to the ski hill and everyone gets a chance to take it down the slope--until it loses structural competency," he notes, in perfect engineerspeak. "Last year we had our canoe break into two pieces when it hit a jump." (Believe it or not, there is now a concrete toboggan competition held in Canada for students of civil engineering--Michigan Tech might want to look into that.) Some teams, like finished product winner Laval, are justifiably reluctant to give their canoes such an abrupt and undignified send-off. "We’re going to proudly exhibit the canoe in the faculty main hall entrance," says Francois Paradis, who still cherishes his canoe’s "perfect gunwales and complex forms," not to mention its "beautiful nose cone." And some, no doubt, may end up buried in the deep recesses of a YMCA camp boathouse. Originally Published, Paddler November-December 2001 |
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