Make Things Float, Like Yowie Did!
Build small boats from recycled materials, test how much weight they carry, and learn about buoyancy, balance, and simple design through hands-on experiments.
Step-by-step guide to Make Things Float, Like Yowie Did!
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
Final steps
You're almost there! Complete all the steps, bring your creation to life, post it, and conquer the challenge!
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).
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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.
🧩 Small design changes—wider hulls, sealed compartments, or flatter bottoms—can hugely increase how much weight a model boat carries.
