DIY Pop-Pop Boat

A pop-pop boat is a model boat that is powered by a steam engine process. The rapid conversion of water into steam ejects the remaining water in the water lines, resulting in a rearward thrust and corresponding forward motion. The steam conversion process is instantaneous, resulting in a loud popping sound -- hence the name. Pop-pop boats use an open flame beneath the steam engine, but they can be duplicated in a DIY version with a simple copper coil connected to a pair of copper tubes.

Things You'll Need

  • Metal boat assembly or sheet metal to construct one
  • Tape measure
  • Straightedge of t-square
  • Power hacksaw or tin snips
  • Pliers
  • Soldering iron and solder
  • 1/4-inch copper tubing
  • Hammer
  • Common sand
  • 1 1/2-inch diameter wooden dowel or shovel handle
  • Power drill or metal punch
  • Disposable metal soup spoons
  • Insecticide-grade candle wicks
  • Metal wick clips
  • Beeswax
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Instructions

    • 1

      Select or build a metal-bottom boat less than 18-inches in length. If one is not available, you can make one out of sheet metal. Measure, mark and cut an 18-inch length of 6-inch wide sheet metal with a power hacksaw. Bend the corners of one end of the sheet metal inward and together, forming a triangular shape in its end. Bend up the first 4 inches of the triangular end of the assembly to form a bow.

    • 2

      Measure and cut a 40-inch strip of sheet metal four inches wide. Bend the sheet metal strip twice at its midpoint so as to form a 6-inch, U-shaped stern for the boat. Place the stern end of the bent strip of sheet metal over the square end of the sheet metal keel of the boat. Lay the ends of the strip of sheet metal against the lifted bow of the boat. Use a marker to mark the angled cuts needed to mold the edges of the ends to fit the angle of the bow. Cut the ends to remove the marked off metal.

    • 3

      Use a soldering iron to solder the two pieces of sheet metal together, forming the connected hull and keel of the boat. Note: if the sheet metal is galvanized, do the soldering outdoors.

    • 4

      Build the coil steam line by wrapping a copper tubing into a coil. The coil should have six wraps (a wrap is a rotation around an imaginary coil center). The diameter of the coil core should be 1 1/2 inches. Pound one end of a 2-foot length of 1/4-inch copper tubing flat. Stand it on that end and fill the tubing with common sand, to prevent the tubing from kinking when it is wrapped. Pound the other end flat. Wrap the tubing around a shovel handle or a piece of 1 1/2-inch diameter wooden dowel. Wrap it six times.

    • 5

      Drill two 1/4-inch holes, 1 1/2-inches apart in the stern of the metal boat, where the stern meets the keel. These holes can also be punched and enlarged, but be sure to pound the stern flat after punching them.

    • 6

      Bend the copper tube assembly so that the coil rests in the center of the boat interior, with the coil 2-inches above the bottom of the keel, and the long ends of the copper tubing extending to lay flat along the bottom of the keel. Cut the ends of the copper tubing and drain the sand. Extend the ends of the tubing out of the two holes in the stern.

    • 7

      Use a soldering iron to connect the straight, bottom lengths of the copper tubing to the bottom of the boat. Lay on a heavy layer of solder, ensuring that the copper tubing will be cooled by the water below the keel. Also solder around the copper tubing extending out of the two holes in the stern.

    • 8

      Fabricate the spoon candles by melting beeswax and pouring it into large, metallic soup spoons and inserting wick clips and wicks into the wax as it cools. One spoon candle will be used each time the boat is launched, to heat the water in the coil and turn it to steam.