Build Your Own Boat

Updated: Dec 22, 2020

An exploration into engineering & design practices

Grade Level:

K-8

Subjects:

Physical Science:

Density

Buoyancy

Forces & Interactions

Engineering & Design

Tools & Materials

1. Question: Can aluminum be formed to float? Can it carry a load?

2. Make a Claim:

What do you think would happen if you put a ball of aluminum foil into a bucket of water? Would it sink or would it float? Can you change the shape of aluminum to make it float? Can it carry a load (pennies)? How many pennies can your aluminum design carry?

3. Test Ideas:

Fill a bowl or container with water.
Crumple one sheet (1ftx1ft) of aluminium foil into a ball.
Place the ball of aluminum foil into the water. Does it float or sink?
Think of a design or shape that you could form out of aluminum foil that will float. Sketch your design in your science notebook.
Build a model of your design out of another sheet (1ftx1ft) of aluminum foil
Test your model by placing it gently on the surface of the water. Does the aluminum foil float? If it does, do you think it can carry a load?
Start by adding one penny onto your model. Does it still float with the weight of one penny?
Keep adding more pennies to your model and keep track how many pennies you have added in your scientific notebook.
When the model starts to sink or begins taking on water stop adding pennies. Record your final load in your science notebook.
Use what you have learned to change the design of your model to carry a greater load.

4. Collect Data:

Sketch each design you test in your science notebook. Record the greatest load for each design.

5. Analyse & Interpret Data:

Which of your designs was able to carry the most pennies? How does shape influence the ability to carry a load? Think of the typical boat designs that are used in the real world, do any of those shapes look similar to the ones you created?

6. Communicate Findings:

Post photos of your aluminum foil boat models and number of pennies that it could carry on social media and tag us @sweptahoe on Instagram and/or to @swep4 on Facebook. Be sure to hashtag and follow #SWEPsnippets. If you cannot post directly yourself, send your photos or video to SWEP (Jenna@4swep.org).

Why do things float in water?

Density & Buoyancy help explain why some objects sink and why some objects float.
Density: Objects are made up of very tiny molecules. Molecules can be packed in close together like in a rock or more spread out like in bubble wrap. The positioning of molecules affects the density of an object. Objects with tightly packed molecules are more dense than those where the molecules are spread out. Density plays a part in why some things float and some sink. Objects that are more dense than water sink and those less dense float. In this experiment, when you put the empty foil boat on the water, it should have floated because its total density (or mass per unit of volume) was less than the density of water. As you added pennies to the hull, its density increased and the hull floated lower. Eventually, when enough pennies were added, the hull's density roughly equaled the density of water. This happens right before the penny is added that sinks the hull. The hull sinks because its density has finally become greater than the density of water.
Buoyancy is a force that pushes up on objects immersed in water. The more surface area the object has for the force to push up on, the greater chance it will float and the more weight it will hold. In this experiment when your foil was more spread out it had a greater surface area and therefore more buoyant force holding it up.

More engineering and design activities:

Make some music with your own rain stick
See how tall you can create a toothpick tower using only marshmallows and toothpicks

Thanks to the Excellence in Education Foundation for supporting student's science learning activities.

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