Boat building challenge

Use aluminum foil to make boats and then test designs by seeing how many pennies or paperclips they can hold.

Please find a printable PDF of this activity here.



  • When an object is in the water, gravity pulls the object down and displaces some of the water, which means some of the water is pushed aside.
  • Gravity pulls the displaced water down, and causes an upward force on the object, called buoyancy.
  • The amount of water displaced depends upon the volume of the object. A higher volume causes more fluid to be displaced, which means more buoyancy.
  • Boat designers have to consider buoyancy as well as friction when deciding on the shape of a boat’s hull. A boat designed for speed must have enough displacement to stay afloat, but surface area has to be minimized to decrease the effects of friction.
  • On the other hand, an object designed to carry a heavy weight, such as a cargo ship, must be designed with greater displacement.



  • Sheets of aluminum foil (30 x 30 cm)
  • Tub of water
  • Pennies or paper clips



  • Design and build a boat with one sheet of foil.
  • Float boat in the tub of water.
  • Add pennies or paper clips one at a time into the boat.
  • Design a new boat to hold more weight!



  • Calculate the boat hull’s surface area and compare/graph to the number of pennies held.
  • Design and build sail boats and use a fan for wind.
  • Participate in the Sea Perch Challengeoffsite link.


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