Will it Float? – Cardboard Boats

My group designed our cardboard boat with high sides that keep the boat from sinking too low and filling with water. However, they were short enough so that the boat wasn’t top heavy and still comfortable to row. We also put a forty-five degree angle on the front of the boat so that as we paddled the boat forward, the water would help keep the boat up and also make it easier to cut through the water. Another effective design element we incorporated into our boat is for it to be wide enough so that we could comfortably sit in it and also keep from tipping over. One of the main parts of our design that weren’t very effective was that we rushed to put the tape on and forgot to tape certain weak places where the water easily started to soak the cardboard. We also were very messy when putting on the tape, which left areas where the tape came undone and water took over. I would change our design by taking more time putting the tape on by making sure every vulnerable area was well taped. I would also probably change it by making it longer so that it could fit more people and make it a little more comfortable to sit in.

Even though our design was pretty good, many groups had great design elements that if we put all of them together we could build a boat that could probably hold a lot of people and not flood and collapse. One of the big things that I thought was the most effective that even the winning group’s boat had incorporated into their design was the use of a tightly sealed area that was full of air. This seemed like it greatly influenced their buoyancy, helping them stay afloat with five people inside. Another effective design element I saw was that a couple groups used cardboard that had been printed on, which most likely helped resist water and kept them afloat longer. Some of the other groups even incorporated pontoons onto their boat, or raft, which helped them stay buoyant.

Archimedes’ principle of buoyancy states, “The buoyant force on a body immersed in a fluid is equal to the weight of the fluid displaced by that object.” So for our boat to float we needed to displace weight of water equal or greater to its own weight. For our boat to float along with two other people we had to make sure that our boat displaced enough of the water’s weight to stay afloat. If each person weighed approximately 150 pounds each and the boat weighed about 25 pounds, for the two people in the boat to float it would have to displace at least 325 pounds and preferably more. If our boat didn’t displace enough water to cancel out the weight of itself and its passengers it would sink.


4 Responses so far »

  1. 1

    Sharlotte Wells said,

    I’m actually about to do this activity as a school project because we are learning about buoyancy so this really helped me!! Thx!!

  2. 2

    Mike Hunt said,

    word press yellow text is the best!
    I had to change the color of the text to read this.

  3. 4

    Katie said,

    Thx you so much for this information! I’ve used this for a project in math that is a big test grade. Part of it is the research, you don’t find many websites like this. Great information!

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