In preparation for the 2019 Medford Canoe Races, our new Freshmen crew were tasked with building a cardboard canoe to compete. We had 6 freshmen spread across 2 class periods, and spent about 1 month designing and building the canoe, which, due to class schedules was about 28 class periods spread between the 2 classes. Depending on how much CAD work you expect from the Freshmen, you may want to add more time.
Additionally, you need to allow plenty of time for cutting materials – using the laser cutter, and make sure you have secured a good amount of usable cardboard beforehand. Precutting cardboard into 24″ x 18″ pieces (the bed size of our Epilog lasercutter) is also very helpful and a task that should be included in the building timeline.
We began with getting some basic dimensions for the length of the canoe – basically, how wide and how long a space would be required to allow two students to fit into the canoe. Our design would utilize ribs connected by spars with a skin of cardboard laid over it. The width of our ribs was constrained by the bed size of the laser cutter, and we opted for a shape that could fit into a 23″ x 17″ rectangle. This fit with our measurements, which were between 16″-18″ for a student on their knees.
We worked as a group to create a CAD model using Autodesk Fusion. The model utilized the same ribs for the majority of the hull, connected via spars on the bottom and sides. The front and back of the boat were the most difficult to model, but allowed us to get a pointed nose front and back with laser cutter precision. This is highly recommended, as it makes construction much easier. You can download our model here, and there are some photos below. (Note – we recognize this is not the ‘cleanest’ model, we were in a hurry putting it together. Next year we hope to have a more organized model to distribute). If you decided to use our model, please give us credit and and mention us in your design (@mvthsengineering on Instagram).
With our model set we began construction. We divided up the tasks into laser cutting material and gluing pieces together. Below are photos of the construction process, which took several days.
Once the entire boat was constructed and skinned, it was time to add some waterproofing. We covered all joints with a brown Uline paper tape and covered the entire boat in several, four or five, coats of Miniwax Polycrylic for waterproofing.
We finished the boat with some white primer, in this case we had a bucket of Killz in our shop, so we applied 3 or 4 coats of Killz. Next, the students used some color spray paints to decorate the boat. Because the Killz has a matte finish, we ended up adding a final coat of the Polycrylic, which added a nice glossy shine to the boat. We had two groups of students working on the boat, and each was given one side of the canoe to decorate.
So, we were pretty excited for race day. Our canoe looked great, and felt sturdy. The team would go up against a team of seniors from Medford HS, so our Freshmen were excited to show off their superior building skills. Check out the video below to see how the performed in it’s first race.
Well, that did not go according to plan. While our boat was strong and waterproof, it proved to be too bouyant, which made it tipsy and difficult to control. Once it took on some water and our paddlers got more coordinated, it moved through water very well. Unfortunately, we had already lost the race by that point.
In the melee of the boat tipping and our students frantically trying to get back into the boat, some damage was done to the interior, which allowed for quite a bit of water to get into the hull. After coming ashore it was agreed upon by the team that the boat was no longer usable, and instead of continuing with it until it’s inevitable demise in the water, we decided to salvage the boat and bring it back to the shop to keep as a reminder and learning lesson for next year.
While we did not win any races, the team did unanimously win the ‘Best Style’ contest and were awarded 2 plaques and 2 gift certificates to Boating in Boston. It was a great learning experience for the team, and we are looking forward to competing next year.