How to Make a Candle Powered Boat

A candle powered boat is a toy originating from France in 1891^[1]. Other names for a candle powered boat include Can-Can-boot, Knatterboot, toc-toc, Puf-Puf boat, Poof Poof craft, Phut-Phut, or Pouet-Pouet (because of the sound they make). A candle powered boat runs using a very simple heat engine. This small boiler, is connected to an exhaust tube (in this case straws). When heat is applied to the boiler (by the candle), water in the boiler flashes into steam. The expanding steam^[2] pushes some of the water in the exhaust tube, moving the boat forward. The steam bubble then condenses, creating a vacuum which draws water back in through the exhaust tube. The cooled water that is brought back into the boiler is then heated and flashed into steam, and the cycle repeats. This constant flashing and cooling cycle of the engine creates the distinctive "pop pop" noise for which the boat is sometimes called.^[3]

EditSteps

EditMaking the Boiler

1. Take your soda can. Take off the cap and wash it. Cut the bottom, and along the sides. This will create a flat sheet. It is okay if the sides are somewhat jagged, as you will trim it later. Once you have the flat sheet, roll it backwards along the table to undo the curve the can naturally has.
   
2. Cut a straight line along one edge, and mark a 6cm x 18cm rectangle. Cut that rectangle out and trim any jagged edges still there. Be very careful not to cut yourself. Recycle the other pieces.
   
3. Gently fold the aluminum sheet in half, being careful not to tear it by pressing too hard. If it helps, fold it along a ruler. Unfold after you've done this.
   
4. On one half of the aluminum sheet, mark out three lines 1 cm from the edges. Cut along these lines and trim the pieces that hand off. You should have one half being 6cm x 9cm and the other being 4cm x 8cm.
   
5. Take the Blu-Tac, warm it up in your hands and roll it into a long snake about 0.5cm in diameter. Line two edges of the smaller edge with this Blu-Tac, then flatten it out slightly.
   
6. Fold it in half again, remembering not to press too hard. Press the Blu-Tac under the metal. Next, line the top of the piece you just folded over with more Blu-Tac, directly over the other bead of Blu-Tac.
   
7. Fold the edges over where the Blu-Tac you just applied and crimp the metal with pliers. Be gentle, making sure to not tear the metal. If possible, use small pliers.
   
8. Remove the excess metal to leave one long tab along the bottom. It is not very important for the edge to be perfectly straight, but it helps a lot if it is. It should now be approximately 9cm long and 4cm wide.
   
9. Take the Blu-Tac and flatten it out into a strip about 1cm wide. If necessary, fold it in half then flatten it.
   
10. Take the Blu-Tac and wrap it around the first straw, followed by the second. Wrap the first one so it is completely covered twice, then add the second straw, continuing to wrap the Blu-Tac around both straws until the Blu-Tac is used up. Make sure to add enough Blu-Tac so that the straws are well-secured by a good plug of Blu-Tac.
    
11. Open up the pocket of the boiler and carefully insert the straw plug. Add some more Blu-Tac until it forms a good seal. Remember the Goldilocks principle: not too much, not too little.
    
12. Cut along the tab at the end near the straws. Fold the two outer pieces up, and squeeze them with the pliers. Add any needed Blu-Tac.
    
13. The boiler is now complete.
    
    • Test that it is airtight by putting it underwater and blowing. If you see any bubbles, give that area a gentle squeeze with the pliers and try again.

EditMaking the Boat

1. Cut an empty carton in half from top to bottom. Leave the top closed when you do this. If it opens using the carton itself, use the end that is not open. If it uses a bottle top, use the side without the bottle top.
   
2. Take the other half of the carton and cut off the spout/top off of it. Cut out any Windows, and decorate it as you see fit. Put aside the cabin to attach later with glue, tape or Blu-Tac, attach the 'cabin' to the boat.
   
3. Cut a small hole big enough to hold the two straws, but no bigger. It may be easier to cut this part with a knife. If desired, twist the knife around in the hole to scrape the edges so they are smooth.
   
4. The boat is now finished.
   

EditConnecting the Boiler and Boat

1. Stick the straws through the hole and tape the long part to the bottom. Snip off any extra that extends past the end of the boat.
   
2. Plug up the hole with Blu-Tac. Once you have successfully taped the straws to the bottom, cover the hole on both sides with Blu-Tac. Quickly test the boat to see if it's watertight. If not, add more Blu-Tac.
   
3. Stick on the cabin. Attach it with glue, tape or Blu-Tac. Your boat and cabin are now complete.
   

EditUsing the Boat

1. Prep the boat by taking one straw and, with water in your mouth, blowing hard until water comes out of the other straw. You can also do it by sucking water into your mouth. Once prepped, tape the straw back to the boat.
   
2. Place the candle in the boat. After a few moments, the boat will being to move forward in the water and make its signature popping sound.
   
3. Finished.
   

EditThings You'll Need

• Soda can
• Blu-Tac (or other flexible, clay-like adhesive)
• 2 straws
• Empty juice or milk carton
• Candle
• Matches or lighter

EditSources and Citations

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