We chose a shape to be the sail of our boats. Then we had boat races to see which shape was the fastest. The bottom of the boat is an egg carton covered with tin foil to make it water proof. We put play dough in the bottom to stabilize it in the water and hold the straw. Each boat needed 1/3 of a straw.
We learned that:
If there is too much "wind" they fall over.
If you add too much play dough they sink.
If you don't add enough play dough they might tip over.
Here are a couple really good grade level appropriate
Columbus Day books:
