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Make a boat

Make a boat
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Build a simple floating boat from recycled materials like cardboard, tape, and plastic, then test stability and buoyancy in water safely.

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Step-by-step guide to make a boat

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Self-Paddle Boat | STEM Project

What you need
Adult supervision required, cardboard, colouring materials (optional), marker, plastic bottle or small sealed plastic container, scissors, small weights (coins or buttons), tape

Step 1

Gather all materials onto a clean flat workspace.

Step 2

Choose one plastic bottle or small container to be the boat hull.

Step 3

Place the chosen bottle on the cardboard and trace its outline with the marker.

Step 4

Cut out a cardboard piece sized to cover the top of the bottle.

Step 5

Fold up small edges on the cardboard piece to make shallow sides for the deck.

Step 6

Tape the cardboard deck securely to the bottle so it sits centered and stable.

Step 7

Reinforce all seams and joints with extra tape to help keep water out.

Step 8

Decorate the deck with markers or colouring materials if you want.

Step 9

Fill a sink or bathtub with a few inches of calm water for testing.

Step 10

Gently place your boat in the water and watch whether it floats.

Step 11

Add small weights one at a time to the center of the deck to test stability and buoyancy.

Step 12

If the boat tips or takes on water add more tape or attach a second small sealed bottle for extra flotation.

Step 13

Put the boat back in the water to see if your adjustments improved float and stability.

Step 14

Share a photo and what you learned about buoyancy and stability on DIY.org.

Final steps

You're almost there! Complete all the steps, bring your creation to life, post it, and conquer the challenge!

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Help!?

What can I use instead of a plastic bottle if I can't find one?

If you don't have a plastic bottle you can use a sealed juice carton, empty yogurt tub with a tight lid, or any small sealed food container as the hull and follow the same 'trace on cardboard' and taping steps.

My boat keeps tipping or taking on water — what should I try next?

If the boat tips or takes on water, reinforce seams and joints with extra tape, make sure the cardboard deck is centered and has folded edges, or attach a second small sealed bottle for extra flotation as the instructions suggest.

How can I adapt this activity for different age groups?

For younger children have an adult do the cutting and handle the tape while they pick a bottle, trace and decorate the deck and test it in the water, while older kids can design different hull shapes, add a second sealed bottle for flotation, measure how many weights the boat holds, and record results.

What are simple ways to extend or personalize the boat project?

To extend the activity, personalize the deck with markers or paint, add a sail from a straw and paper, attach a small rudder or extra sealed bottle for stability, and then share a photo plus your buoyancy observations on DIY.org.

Watch videos on how to make a boat

Here at SafeTube, we're on a mission to create a safer and more delightful internet. 😊

How To Make A Paper Boat For School Project | Origami Boat | Easy Origami Tutorial

4 Videos

Facts about buoyancy and boat building

♻️ Upcycling win: turning old cardboard and plastic into projects reduces waste—recycling one ton of corrugated cardboard can save about 17 trees.

⚓️ Big metal ships float because their overall density (including trapped air) is less than water—shape and volume matter, not just material.

🧠 Archimedes' principle: an object floats when it displaces a weight of water equal to its own weight—try measuring water rise to see it in action!

📦 Cardboard can float surprisingly well if kept dry and sealed—many schools host cardboard boat races where kids paddle their creations.

🌊 Stability tip: a wider, lower hull and placing weight near the center and low down helps prevent tipping and keeps your boat steady.

How do you make a simple floating boat for kids?

To build a simple floating boat, trace a hull shape on sturdy recycled cardboard and cut it out (adult help for box cutter). Fold and tape edges to form a shallow boat, sealing seams with waterproof tape or duct tape. Reinforce the bottom with glued-on plastic bottles or foam for extra buoyancy. Add a small deck or mast from a straw and paper sail. Test in a shallow tub with an adult, adjust weight and seals until stable.

What materials do I need to make a recycled cardboard boat?

You'll need recycled cardboard or a small cardboard box, waterproof tape or duct tape, scissors and craft knife (adult use only), glue or hot glue, empty plastic bottles or foam pieces for buoyancy, waterproof marker or paint, scrap paper or a straw for a sail, and a shallow tub or basin for testing. Optional: cling film or waterproof sealant to cover cardboard, and small weights (coins) to fine-tune balance. Supervise children around sharp tools and water.

What ages is making a cardboard boat suitable for?

This activity suits ages about 4–12 with adult guidance. Ages 4–6 enjoy assembling, taping, and decorating with close supervision; avoid sharp tools. Ages 7–9 can cut simple shapes with supervision and test buoyancy experiments. Ages 10–12 can design more complex hulls, add sails, and iterate engineering changes independently while still being supervised near water. Always supervise young children during cutting and any water play, and adapt difficulty to each child's fine-motor skills.

What are safety tips and fun variations for building and testing homemade boats?

Safety first: always supervise water tests, use a shallow tub, keep towels nearby, and handle knives and hot glue only by adults. Waterproof seams with duct tape to prevent soggy cardboard. For variations, try using sealed plastic bottles for a pontoon-style boat, covering hulls with cling film or waxed paper, or making a sailboat with a straw mast and paper sail. Turn the activity into a mini STEM lesson by measuring how much weight each design holds and noting why some shapes float better.
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