By Northeastern University’s Concrete Canoe Team
Each year, the American Society of Civil Engineers releases a request for proposals, inviting student chapters across the country to participate in a competition to create the best concrete canoe. Northeastern University has participated in the challenge for decades, and has a robust team that spends Monday and Wednesday nights designing mixes, running structural analyses, creating an engaging presentation and display, cutting a mold, and all the other wonderful things that go into the creation of the final product.
Beginning in September, the team conducts research into different design alternatives, examining different nose shapes, overall shapes, and different dimensional combinations. Using guidance from professors and other technical advisors, as well as its own research, the team selects a final design shape, and begins the difficult task of analyzing the different load cases the canoe undergoes at and on the way to competition.
At the competition, the canoe is raced in five different races, and subjected to a swamp test to confirm it can float. The races are: men’s sprint, women’s sprint, women’s slalom, men’s slalom, and co-ed sprint. In all races, the canoe is loaded with two paddlers, except for the co-ed sprint which loads the canoe with four paddlers. The team performs both elementary shear and moment analysis coupled with finite element analysis to determine the critical loading case, and passes that information off to the mix design team who begin the work of developing a suitable mix.
Unlike typical concrete mix design, the concrete used in this canoe must be below or very close to the density of water, 62.4 lbs/ft3, while retaining a high enough strength to resist the stresses exerted by the paddlers. Using a variety of different materials and aggregates, from standard materials like cement and slag to more uncommon materials like Porover and Stalite, multiple different test mixes are created, cured, and tested at 14 day strength in the department materials lab to determine which design most successfully toes the line between density and strength.
Along with the final mix, referred to as the team’s structural mix, the mix team also creates a patch mix, used for patching potential errors in the final canoe. This mix doesn’t need to meet the same strict requirements, and is more of a slurry used to smooth over imperfections. Both mixes are retested, this time at 28 day strength, and final capacity ratios are calculated.
In tandem with the mix design process, the construction team begins the arduous process of creating the team’s foam mold. In the past, the team had used a hand-cut male mold (the concrete is poured over the mold, which is the shape of the inside of the canoe), which took a lot of time, and led to a rough exterior finish. This rough exterior meant that the canoe was far less aerodynamic, and made the canoe more challenging to paddle at race caliber speeds. To alleviate these issues, the team made the switch to a female mold, removing the rough exterior issues. Additionally, rather than hand-cutting the foam pieces by hand, the team transitioned to using a CNC machine.
For the CNC machine, the entire canoe model was sliced into 90 pieces, each of dimension two feet by four feet to fit into the bed of the machine. Then, the pieces were cut in the machine one by one, at a rate of roughly one piece every 15 minutes, for a total of almost 23 hours. The pieces were organized into 10 stacks, each 9 pieces high, and gathered for assembly. The pieces were glued together sequentially, and then the interior was covered with duct tape to smooth out the mold interior. The glued and taped stacks were connected together, and the entire mold was ratchet-strapped around the outside to hold it together.
The last step of the design process before the canoe is poured is to create and prepare a reinforcement scheme. The team uses a combination of fiberglass meshes together to strengthen the canoe, working to increase the overall tensile strength. The mesh scheme is attached to the canoe between layers of concrete, and is tensioned by wires running through the mold and tying into the mesh. This further adds to the mesh’s efficacy, further raising the tensile strength.
Once the entire design is complete, the canoe is poured in one marathon 6 hour process. The entire team works swiftly to place all three concrete layers and two reinforcement layers, and create additional design components. The canoe is roughly ⅝” thick once complete, with three ⅛” layers of concrete and 2 ⅛” layers of reinforcing mesh. Aside from the canoe itself, the team also adds in interior gunwales to increase stability and give paddlers something to hold on to, three longitudinal ribs to add additional strength below the paddlers knees, two noses roughly 6” deep, completely filled solid concrete, and two bulkheads, each 36” deep, filled with additional foam to assist with flotation.
Once all components are complete, the canoe is prepared for its 28 day cure. Wet sheets are draped over the interior, covering the entire surface, and trash bags are placed on top of those, sealed with duct tape to prevent moisture from escaping. The sealed canoe is left alone in the lab, and then, once cured, is demolded. The exterior and interior are meticulously sanded, removing any bumps, and the patch mix is applied as needed. The sealing materials are replaced to cure the patches. Once the patches are cured, the canoe is stained in accordance with the theme, badged with “Northeastern University”, and sealed to protect against water intrusion.
For competition, taking place at the Region 1 ASCE Student Symposium, April 16-18, 2025 at the University of Massachusetts Amherst, the canoe is loaded into a UHaul and driven the 90+ mile journey out to western Massachusetts. The team drives over with it, and gets ready for the competition and symposium festivities.
This entire process, from design conception to competition requires both incredible time investment and financial investments. From a time side, the team as a whole has poured over 900 hours over the course of the season into the final project thus far, with two weeks still to go. Financially, the team has spent almost $5000 this season, and is forever grateful for the support it receives from the Northeastern University Department of Civil and Environmental Engineering, alumni donations, team member donations, assorted fundraisers, and of course, the grant funds received from the Boston Society of Civil Engineers Section. The team could not purchase mix materials, mold construction tools, and even come close to affording competition travel, lodging, and registration fees, which can reach upwards of $200 per person.
Overall though, this competition is an incredible opportunity for civil engineering students, both at Northeastern University and at other schools throughout the state and nation, providing a hands-on challenge, and using an incredibly common engineering material in a somewhat unorthodox manner. This challenge is a ton of fun, growing the collaboration, communication, organizational, and problem-solving skills of participation team members, setting them up for successful careers in whatever field of civil engineering they should choose to pursue.