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Milk Carton Boat Race, by Ciara, Brittney, and Maria

We recently had a very "mooo-ving" experience: we built a boat entirely out of milk cartons to enter in a hometown race! Using 150 milk cartons, we had to design a boat that would carry all three of us in a race. Our DFTV question: What boat shape or design is most effective?

What did we do?
We each thought a certain design would work best. Brittney voted for a boat with a pointed bow and a V-shaped hull for easy turning. Maria thought a catamaran/pontoon boat would be fastest. Ciara said a flat-bottomed raft would offer the most stability. The only way to determine the best shape was to build and test miniature versions of each design. We used half-pint cartons for our test boats, and tested each model three different ways. First, we tested how well each boat glided through water by giving it a push and measuring how far it drifted. Second, we judged the boat's maneuverability by creating an "obstacle course" with bobbers. Finally, we checked for stability by loading each boat with sand and testing for "tippiness."

What did we find out?
We know that there are a lot of boats with V-shaped hulls, but our V-shaped test boat didn't do well; it was tippy and didn't glide far at all. The catamaran gave us the most glide by far, with 8.5 feet. Finally, the raft and the catamaran offered good stability. We ended up choosing to build a combination catamaran-raft for the race. We entered the local competition, and took 2nd in our age group!

What can you do?
  • Design your own milk carton boat. Figure out how many cartons you need to keep yourself afloat. [Hint: a half-gallon carton can float about 4 lbs.] Then, with an adult close by for safety, try floating your boat at the lake.
  • How does the shape of a sail affect how well a sailboat zips along? Build a simple milk carton boat and make some different sail shapes to find out. Take it to a lake or pool when there's a nice breeze and see how well each sail catches the wind.
  • If you know someone with a sailboat, ask to go sailing. Take a stick with a streamer attached. While you are sailing, hold up the streamer near different parts of the sail. What does the streamer show you about how the air is flowing near the sail?
  • Use this engineering investigation as a science fair project idea for your elementary or middle school science fair! Then tell us about it!
more resources
More on buoyancy.

Go to the DFTV Boards, and tell us about your science investigation.
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