Fruit skin boats
Sail away on a fruity adventure! Your STEAM challenge is to use leftover fruit skins to make a cargo boat. A perfect way to make use of fruit skins left over from preparing a fruit salad. This activity can be carried out by individuals or small teams.
You will need (per team of 4):
- Deep Gratnells tray half filled with water
- Shallow Gratnells tray with office insert for organising all the other equipment
- Shallow Gratnells tray or Gratnells art tray
- Wooden BBQ skewers, one per boat. For smaller boats skewers can be cut in half or thirds
- A selection of scrap paper or card for the flags/sails
- Coloured pens or pencils for decoration
- Tape or paperclips for attaching the flags to the masts
- Glue, glitter or any other craft materials you have available for decoration
- A selection of appropriate fruit e.g. melon, watermelon, limes, lemons
- A sharp knife (adult supervision required)
- Spoons, scoops or lemon squeezers for removing the fruit flesh
- 2 x Scissors
- Two pounds worth of one penny pieces, or any other suitable small weights/beads
- Cloths or towels for mopping up any spills
This activity also works as an individual challenge, just reduce the amount of equipment accordingly. Most of the equipment required (apart from the fruit) can be reused for future or alternate activities.
- Gather and organise all the equipment, apart from the fruit, into the office insert in the shallow tray.
What to do:
- Place the fruit into the empty shallow or art tray (used as a chopping board and to contain all flesh, drips and mess).
- Cut the fruit in half using the knife.
- Carefully cut, scoop or squeeze out the fleshy insides. Use a spoon to scrape the inside of the skin to make sure all the flesh is removed. Pop the flesh into an airtight container and keep to one side to make a yummy fruit salad later. Retain your newly created boat hull for the next steps.
- Make and decorate a flag using the craft materials.
- Attach your flag to an appropriately sized wooden skewer, covering one of the ends.
- Carefully push the pointy end of your skewer into the centre of your boat hull, make sure not to go all the way through the fruit skin or your boat will spring a leak!
- Lift your boat into the water tray, allowing it to float on the water.
- Make a prediction, how many one penny pieces will your boat hold before it sinks? Note this down.
- Steadily add one penny at a time to your fruit skin boat, counting how many you can add before it becomes too heavy and sinks. Top Tip: It helps to distribute the pennies evenly across the boat.
- Record the number of pennies your boat was able to hold and compare this to your prediction.
- Repeat this test for the other pieces of fruit, each time making a prediction as to how many pennies the fruit skin boat will hold.
- If you need some inspiration, watch our short YouTube video. Younger participants may also benefit from seeing one you made earlier.
Tidy up time:
At the end of the activity, make and eat a yummy fruit salad. Used fruit skins should be composted or, if you keep any, fed to livestock if appropriate for their diet. The wooden skewers can be retained for future STEM activities. Paper and card can be recycled.
What is happening?
Keywords: Buoyancy, Water Displacement, Gravity, Force, Archimedes’ Principle.
Water pushes upwards with a force called ‘upthrust’. You can feel upthrust if you try to push a light object such as a balloon under water. If the weight of an object placed on the water is equal to or less than the force of the upthrust then it floats. When something floats we say it is buoyant. The shape, design and construction of a boat determines its buoyancy and therefore the weight of cargo it can hold. If the weight of the boat is greater than the force of the upthrust then it sinks.
If the force of gravity on the boat is stronger than the force of the upthrust then the boat will sink.
Archimedes’ Principle tells us if the mass of the water displaced is equal or more than the mass of the boat, the boat will float. Therefore, the more water that the boat displaces the better it will float and the more weight it can carry. Once the boat’s mass is heavier than that of the displaced water then it will sink.
Other things to try:
- Make a sailor or pirate for your fruit skin boat using the leftover craft materials, try to make him/her as light as possible. Why is the weight of the pirate important?
- Which fruit makes the best fruit skin boat? Why?
- Are there any other fruits or vegetables you could try? A cucumber kayak or carrot canoe perhaps? What size and shape of boat makes for the best cargo boat? Please only use leftover fruits or vegetables and do not waste food. If you wash your hands and use clean water, you can cook and eat the vegetable boats after you have tested them.
- If you like this activity, try our STEM Sailboat Challenge or STEM Build a Cargo Boat
Health & Safety
As with all Gratnells Learning Rooms What’s In My Tray activities, you should carry out your own risk assessment prior to undertaking any of the activities or demonstrations. In particular, be sure to wipe up any drips or spills immediately to reduce the risk of slips and take care when handling pointy wooden skewers.