Often toys can be found that employ simple physics principles in ingenious ways. Such ones are favorites for demonstration lectures: they get attention as well as teaching the physics. But toys for that purpose get hard to find as more and more of them operate with hidden solid-state chips. For the one for this column, I'm safe from chips, because it's a hundred years old. The toy is a jet-propelled boat. Heat from a small candle inside it makes it eject pulses of water from tubes at the rear just under the water level, at five or more per second. That propels the boat at 10 cm/s or more, and it will go for as long as the candle burns.

This project was made by:

-Alexandre(1);

-Matheus Felizola (29);

-Matheus Martins(31);

Step 1: Gather Resources!

A piece of styrofoam;
An empty soda can;
Two straws (the ones you can fold);
Candles;
Hot glue;
Epoxy glue;
Masking tape;
2 elastics;

Step 2: Download the PDF's!

Engine Pattern

Foam Pattern

Step 3: BUILD!

To begin, cut the top and bottom parts of the can. You should have a paper sheet format now. Fold it so one of the sides is slightly longer and use the tape to hold it together.

Cut the aluminium foil in a half and, with a model, fold it so it has the shape of a rectangle with a space in the middle.

Put the straws inside that space and use the epoxy glue to seal the sides that are loose.

Afterwards, glue the folding point of the straws using the epoxy glue and put them inside the capsule. Seal the side with the rest of the glue real good. Cut the straw 10cm from the folding point.

Using the second model, fold the straw and put glue on the folding so it turns rigid. Using the last model, make the boat's base using the styrofoam.

To do the support for the candle, take another piece of what's left from tge aluminium of the can and fold it in the opposite way of its original curvature, so it's straight. Cut a bit of the two sides of the points, fold them and you'll have your support.

Make a hole in the already molded piece of styrofoam, pass the straws' ends through the hole and keep them together with elastics. Put water in the straws, transfer it to the capsule made previously and fit the candle's support in one of the elastics.

Put the boat on the water and light the candle. The steam should push it forward.