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Make Things Float, Like Yowie Did!

Make Things Float, Like Yowie Did!
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Build small boats from recycled materials, test how much weight they carry, and learn about buoyancy, balance, and simple design through hands-on experiments.

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Step-by-step guide to Make Things Float, Like Yowie Did!

What you need
Recycled containers like small plastic cups bottle caps or yogurt cups, tape or waterproof glue, modelling clay or playdough, small coins or metal washers for weights, a straw or wooden skewer, scissors, colouring materials for decorating optional, large tub or basin of water, adult supervision required

Step 1

Gather all your materials and set them on a clear table or the floor.

Step 2

Pick one recycled container to be the hull of your first boat.

Step 3

With adult help cut or trim cardboard or the container to shape the hull if needed.

Step 4

Seal any holes or join pieces with tape or waterproof glue so the hull won't leak.

Step 5

Press a small lump of modelling clay under the hull to act as ballast and keep the boat upright.

Step 6

Push a straw or wooden skewer into the hull to make a tiny mast if you want sails.

Step 7

Decorate your boat with colouring materials to make it fun and unique.

Step 8

Fill the tub or basin with water until it is deep enough for your boat to float.

Step 9

Gently place your boat in the water so it can settle and float by itself.

Step 10

Add one coin or washer at a time to the center of the boat until the boat tips or sinks.

Step 11

Count how many coins the boat held before it sank and write or say the number out loud.

Step 12

Change one design thing like moving the ballast widening the hull or using a different container and build a second boat.

Step 13

Test the second boat the same way and compare how many coins each boat held to see which design worked best.

Step 14

Share photos or notes about your finished boats and what you learned on DIY.org

Help!?

What can I use instead of modelling clay or waterproof glue if I can't find them?

If you can't find modelling clay use a small pebble or crumpled aluminium foil as ballast under the hull and if waterproof glue isn't available wrap seams tightly with clear packing tape to seal the hull (Step 4).

My boat keeps tipping or sinking right away—what should I check or fix?

If the boat tips or sinks, recheck Step 4 for leaks and add extra tape or glue, ensure the lump of modelling clay is pressed under the hull as ballast (Step 5), and place coins one at a time at the center to avoid uneven weight distribution (Step 10).

How can I adapt this activity for different ages?

For younger children have an adult pre-cut a recycled container and use large plastic washers or toy blocks instead of coins, while older kids can build multiple hull shapes, add a straw or wooden skewer mast, and record coin counts to compare designs (Steps 2, 5, 11, 12).

How can we make the boat project more creative or challenging?

To enhance the activity, decorate boats with colouring materials and sails, experiment with moving the modelling clay ballast or widening the hull to see how the coin count changes, and take photos to share your results on DIY.org (Steps 6, 5, 11, 13).

Watch videos on how to Make Things Float, Like Yowie Did!

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Facts about buoyancy and simple engineering

🛁 Archimedes supposedly discovered buoyancy when he noticed how water rose as he climbed into a bath and shouted “Eureka!”

⚖ A ship made of heavy steel can float because its overall shape traps air so the average density is less than water.

♻ Builders and artists often make rafts and floats from recycled plastic bottles, foam, and scrap—perfect for boat experiments!

🧭 Balance is everything: moving weight to one side shifts the center of mass and can make small boats tip quickly.

đŸ§© Small design changes—wider hulls, sealed compartments, or flatter bottoms—can hugely increase how much weight a model boat carries.

How to do the Make Things Float, Like Yowie Did! activity

Start by challenging kids to design a small boat from recycled items like bottle caps, milk cartons, or plastic bottles. Cut and assemble parts with tape or waterproof glue, add a flat deck, and place a small marker for balance. Test boats in a tub, pond, or sink, then gradually add coins or washers to measure how much weight they carry. Observe when they tip or sink, adjust shape or ballast, and repeat to learn buoyancy and balance.

What materials do I need to build small boats from recycled materials?

You e need recycled containers like plastic bottles, yogurt cups, milk cartons, or bottle caps; waterproof tape or glue; scissors or a craft knife (adult use); straws, skewers, or popsicle sticks for masts; modeling clay or putty for ballast; coins or washers for testing weight; a shallow tub of water; and a towel. Optional: markers, stickers, and a ruler for recording measurements.

What ages is the Make Things Float activity suitable for?

This activity suits ages about 412 with adult guidance. Preschoolers (45) can assemble simple boats and watch float tests with help using larger, safe materials. Elementary kids (68) can cut, tape, and experiment with ballast to compare designs. Older children (912) can measure load capacity, record results, and refine hull shapes. Always supervise cutting, small parts, and water play, adjusting complexity to the child's skill.

What safety tips should I know for boat-building and water testing?

Keep safety in mind: supervise all water play and cutting; only allow scissors or craft knives to be used by adults or older children. Avoid very small parts for kids under three to prevent choking. Use non-toxic materials and dry work surfaces to prevent slips. If testing outside, choose calm water and keep life jackets near ponds. Teach cleanup and recycling afterward to reinforce responsible habits.

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