Engineering a Concrete Canoe

BY CHAVEZ & DESOUSA

To the layman, a concrete canoe has one end: to sink. To the inspired mind, however, that same concrete construction comes as a challenge — such is the case for a collection of students hailing from colleges across the U.S. to compete in the American Society of Civil Engineers (ASCE) National Concrete Canoe Competition. At this competition, knowledge and practicality combine through the construction of a concrete canoe that is — hopefully! — capable of surviving even the most grueling obstacles and ultimately winning the competition. The main concern when designing the canoe is to ensure that it is as lightweight as possible, yet sturdy enough to support the weight of the passengers for each race. There are several races comprising the competition: two female, two male, four coed and one full-team race. To qualify, teams must compete in their respective ASCE Student Conference. The conference for the southeast division (to which UM belongs) will be held at the University of Tennessee in Chattanooga on March 19-21. The ASCE judges publish specific and strict rules to which teams must adhere — such as material restrictions and dimension minimums — which only introduces more hurdles for the team to overcome. If these rules are not observed by any individual team, its canoe runs the risk of being disqualified.

The team representing the University of Miami has been working on the blueprints for the canoe since the summer of 2014 and has slowly but surely seen their design come to life. The model was first drafted using AutoCAD, an engineering software application in which users can shape their 2-D and 3-D designs into formal blueprints. The engineers decided to construct their canoe with lightweight concrete reinforced with a carbon fiber mesh. The concrete contains slag and fly ash, both of which are environmentally friendly substitutes to cement. The canoe’s lightweight build allows the team to move the canoe without the use of a crane. Concrete naturally performs very poorly under tension; by employing a carbon mesh reinforcement, they were able to combine the compressive strength of the concrete and the tensile strength of the mesh into one system. After the design was approved and reviewed by the team, the hunt for materials began. Rather, the hunt for sponsors began, as all of the engineers’ materials had to be supplied via donations. Luckily, they had several sponsors, namely Supermix and Titan — responsible for donating most of the materials for the concrete mix — as well as the University of Miami Department of Civil, Architectural and Environmental Engineering, which donated the mesh that would serve as a reinforcement for the canoe.

During winter break, the team built the wooden mold. This female mold — meaning an indented mold, as opposed to a protruding one — was lined with a metal flashing to form the curvature needed for the design of the canoe. After a second collection of materials, and with the mold finally built, the team was ready to pour out the concrete for the base of the canoe. It took a total of six batches of concrete mix to create their three-layered design. These layers were constructed accordingly in order to provide proper support. They were constantly checked for consistency: A layer that was too thin was sure to crack, while a layer that was too thick would yield a sunken canoe. To accomplish this, the team used a marked toothpick to indicate each layer of thickness throughout the canoe.

Team co-captains Hector Castaneda, senior, and Michael Herrera, junior, are both in the architectural engineering program. They both competed in the 2014 ASCE Southeast Student Conference, helping the team race into 9th place out of 25 teams that competed in the southeastern region of the country. When asked about his experience, Michael expressed that the race against time was definitely the hardest part of building the canoe: “Honestly, the hardest thing about this canoe isn’t building, it is the amount of time that it takes to do everything. Between the design, construction of the mold, getting materials and writing the paper, as well as getting support from faculty and staff, it can be really time consuming.” Time was definitely a factor in building the canoe — not just because material application is time-sensitive, but also because juggling a full engineering course load along with a social life does not leave much time to volunteer to canoe-building. “The hardest part for me was definitely getting people to help,” Hector said. “It’s difficult to get students to come in on a Saturday to work on a canoe for a competition. Schools like ones in Puerto Rico have a class that is dedicated to building concrete canoes. So, they have no problem showing up because they are rewarded with a grade. We found it difficult to get fellow engineers and even people from our club to be interested and motivated to help out. But those that did are doing it because they are passionate in engineering, and those are the people we want on our team. Both Michael and I decided to participate in this competition because we were passionate about engineering, and it is an opportunity to apply what we’re learning in class to a canoe we build all on our own, with little to no help from faculty.”

The team is currently in the curing phase of construction, which is the process in which the concrete is protected from loss of moisture and kept within a reasonable temperature range. Curing is an essential part of construction because it helps increase the strength of the structure while decreasing the likelihood of permeability, ultimately increasing the durability of the canoe. When fully cured, the canoe is at its strongest; this point is usually reached 28 days after being mixed. After the canoe is completely cured, the team will demold the canoe (hoping that it will not crack), sand it and paint it. In addition to the canoe itself, the team must also submit a visual display and paper in order to justify the design and explain all of the materials used.

On March 19, UM’s ASCE team will be traveling to Tennessee to test out their design and compete against the 25 other southeastern division teams. On behalf of all of us here at Scientifica, we wish them the best of luck and plenty of smooth sailing ahead.

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