The Unsinkable Boat

A Grade 4 Investigation With Mass, Gravity, And Buoyancy!

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The Plan

Build a boat out of aluminum foil and see how many pennies your boat can hold. Then reshape your boat to see if you can get it to hold more pennies than your first try! Remember to be gentle with your foil and dry it off between trials.

Materials Needed

Metric/ Customary ruler


2 pieces of aluminum foil (6in x 6in.)

Big bowl of water

30 to 40 pennies

Paper Towel

Data Collection Sheet for Aluminum Foil Boats



1. Shape the aluminum foil into a shape that floats

2. Test your design in the bowl of water to make sure it floats. Does it lean to one side or not float well? If the answer of either of these questions is YES- reshape you foil into another shape that will float.

3. Draw a picture of your boat in the data collection sheet.

4. Once you have a shape that is floating, place pennies in it one at a time until it sinks.

5. Record the number of pennies your boat held before it sank. For example if your boat sank when the 12th penny was added, then your boat can hold 11 pennies.

6. Now try to beat your own record by reshaping your boat. Flatten the aluminum foil and dry it. Reshape your boat. What change are you going to make to the shape of your boat?

Note your changes in the Data Collection Sheet.

7. Repeat steps 2 through 4.

8. Now try the entire procedure again with a new piece of foil. Take the second piece of aluminum foil and repeat steps 1-7! It might take three or four different shaped boats to beat your first record or you might see the amount of pennies go up each time!


1. Which of your boats held the most pennies?

2. Why do you think this boat held the most pennies?

3. Did your boat building skills improve as you continued to build boats? When we did this experiment on the show, only two of the four boat builders saw their re-shaped boats hold more pennies. We did not have time to do a second boat with a new piece of foil but I am sure they would have surpassed their own records with a few more tries.

4. If your pieces of foil were slightly different sizes, would this make a difference? Test this idea by using a piece of foil that is 6in x 8in and by making a boat that looks just like one of your other boats. Could this boat hold more pennies?

5. The foil was re-shaped to make another boat in Step #6. What if you forgot to dry your foil off with the towel? Would the extra water weight make a difference as to the number of pennies your boat could hold? Again test this idea by taking your last boat out of the water, flatten it but don’t dry it. Try once again to make a similar looking boat.

Science behind the experiment

There are two primary forces acting on this science experiment. The first force is gravity. Gravity is trying to pull the tin foil and pennies downward. The force of buoyancy is pushing the boat toward the surface.

The gravitational force is determined by the weight of the tin foil and the weight of the pennies in the boat. The force of buoyancy is the weight of the water displaced by the boat.

Your boat will continue to float as long as the force of buoyancy is greater than the force of gravity and you do not overload the boat so it will tip over or leak.