This year, The National Concrete Canoe Competition Rules have defined the outer hull for the canoe:
“In general, the 2009 canoe is a 20-foot long asymmetrical hull with a maximum beam width of 31.1875 inches. The length is defined as the end-to-end measurement of the canoe taking into account the outermost dimensions of the hull as measured at the gunwale. The measurement of the maximum beam width is defined as the outermost dimension of the hull skin as measured at a distance of 10.2 from the bow. The canoe features an elliptical cross-sectional shape with 4 inch radial chines and flared sidewalls and 4 inches of rocker at the extreme ends of the bow and stern sections. The depth of the canoe varies from 16 inches at the bow tapering down to 14 inches near the center and stern.”
In order to strictly adhere to these outer hull dimensions, our plans have changed from building a male mold to building a female mold. We have rendered a model on AutoCAD from the provided design restrictions, and from this will create cutaway sections to facilitate mold construction. In the first step of construction we will create an exact model of the canoe with Styrofoam blocks. We will then use this Styrofoam model as a mold to make a fiberglass female mold for the actual concrete canoe. Several layers of fiberglass will make a sufficiently strong mold for use in the concrete pour, and the exact dimensions provided by the national committee will be mirrored more accurately with this process.
The design of a concrete mix for use in a concrete canoe can be a tricky process. The concrete that we need to design needs to both have a high strength and low weight. These two concepts in concrete are generally considered to be inversely proportional to each other, higher strength concretes tend to be on the heavier side whereas lighter concrete mixes tend to be weaker. Because of this, a happy medium between strength and weight will need to be found. This can be accomplished by analyzing one of many variables. This year, the team has plans on doing research and development and topics such as lightweight reinforcements, environmentally friendly aggregates, and improved concrete workability via use of admixtures.
Actually pouring the canoe requires a large group of dedicated individuals to work for several hours straight in order to achieve the desired result. The canoe isn’t so much poured as it is placed, handful by handful of concrete inside of the female mold that will be constructed. We will have one group of people measuring and mixing the dry ingredients for the concrete, a second group mixing in the wet ingredients until the homogenization of the mixture is complete, and a third group placing the concrete into the mold. We will alternate between thin layers of concrete and reinforcement, with an average thickness of 1” throughout the canoe. The canoe will then be sealed off and kept damp with an humidifier for the first week after the pour, and then will finish the 28 day curing period in open air.
Finishing the Canoe:
Before taking the canoe out of the mold, the inside will be sanded down to a smooth finish. After releasing the canoe from the mold, the outside will also have to be sanded. A concrete stain will then be applied, our school name and the canoe name will be stenciled onto both sides of the canoe and finally we will finish with 2 layers of concrete sealant.
As this year’s regional competition is being held in Hawaii, our team has the added task of shipping the canoe across the Pacific. In order to do this, we must design and build a crate that is capable of protecting our canoe in route. Preliminary calculations have given us an estimated crate size of 22’ by 4’ by 4’. This crate will be entirely student designed and made.
Find a complete set of this year's concrete canoe rules Click Here.
Changes to Rules!!!