Instructions to Build the Jet Boat

Introduction

When I mentioned to a friend that I was going to write a page devoted to mechanical toys, he immediately told me about the jet boat. The jet comes from steam produced in a simple boiler. The boat is nothing more than a used sardine tin and the boiler is an old aluminium cigar tube. This is simple to build and takes less than an hour. The boat moves along reasonably well but given that the sardine tin is not the most ideal boat hull it moves around rather aimlessly. The jet boat goes better than the camphor boat but is slower and less fun than the putt-putt boat. The open flame and hot cigar tube make the jet boat unsuitable for small kids.

What You Will Need

An old sardine tin. The tin should have high sides, approximately 20 mm high.
An old aluminum cigar tube with its cap. If you don't have an old one (and not many people would) then buy a new one. See Mal's hot tip number 1 for something to do with the cigar. Han van Gelderen wrote to say that an egg can be used instead of the cigar tube. Here is what he says:
I've learned to make this boat using an egg instead of a cigar tube.
Make two holes at the tips of an egg, blow the contents out of it, glue one hole airtight, fill the egg with water. That's it. Oh, make an omelet from the egg's contents and watch your jetboat go while enjoying your omelet.
Some wire.
A food-warmer type of candle in which the wax sits in a small aluminium cup.

To build this you will need a medium-sized nail and a hammer, to punch holes in the sardine tin, and some pliers to twist the wire.

How To Build It

Using a nail and hammer (or a bradawl if you have one) poke four holes in the sardine tin - two on each side as shown in the figure on the right. The holes need be big enough only to put the wire through.
Pass a piece of wire through the two front holes (you decide which is the front).
Lay the cigar tube centrally over the sardine tin. The top of the cigar tube faces the back of the boat. Bend the wire over the top of the cigar tube and then all the way around it so that the two ends of the wire come towards each other as shown in the figure on the left.
Using the pliers, twist the ends of the wire together to tighten the wire loop. As you tighten, twist the cigar tube so that it lies longitudinally in the middle of the sardine tin.
Wrap wire around the cigar tube at the back of the boat and tighten it in the same way as at the front.
When the cigar tube is firmly secured use the pliers to cut excess wire away.
Screw the cap onto the cigar tube tightly and make a mark on its end 2 mm from the top. Remove the cap from the end of the cigar tube and, with the thinnest pin you can find, make as small a hole as you can in the end of the cap where you made the mark.
Lay the candle in the middle of the boat. Use a candle that comes in an aluminum cup. Otherwise the melting wax will run inside the boat, upsetting its balance and causing it to capsize.

The candle-powered jet boat is complete! Fill the cigar tube about one quarter with water and screw the cap on. Light the candle beneath the cigar tube and place the jet boat into a bath tub with water. After a while the water in the cigar tube will boil and cause a jet of steam from the small hole in the cap. The steam jet will give the boat some forward momentum. If water leaks from the cigar tube wrap some tape around the cap to seal it tight. If the boat doesn't gain any speed, try using two candles under the cigar tube. Alternatively, you can remove the candle from its aluminium holder, and put a cotton ball and some methylated spirits into it.

BE CAREFUL: the cigar tube and the steam jet are very hot, even after the candle is blown out.

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Last Modified: 5-Oct-1998