Hot Air Balloons Project Instructions

In the Hot Air Balloon Project the students make balloons and then fly them.   This project has three significant features:
  • This project provides the opportunity to explain the physics of why balloons fly and how different shapes (i.e. different surface to volume ratios) and different centers of gravity affect how the kites fly.
  • A group of students can make and fly several balloons in is less than an hour.
  • For safety reasons, this project does not use any open flames.   Rather, it uses a heat gun and a wood burning soldering iron.

To do this project one will need the materials and tools shown below:

  • 45- 50 gallon Commercial Can Liners (i.e. 3’ 4” x 4’ x 0.55 mil).
  • Painter’s Plastic (i.e. 0.31 mil thick plastic sheet).
  • Balloon Patterns (i.e. make from hardboard or flat thin plywood per the attached drawing).
  • Surface to make the kites on, (i.e. make from a piece of hardboard or flat thin plywood that is 40 “ x 48”)
  • Scissors
  • Heat Gun (i.e. I have been using a Wagner Heat Gun # HT3500)
  • Electrical extension cord
  • Wood burning soldering iron
  • Masking tape
  • Paper clips
  • Hole punch
  • Stop watch, optional to time the flights
  • Magic Markers, optional for the decorating the balloon.   Permanent markers are needed to be able to decorate the plastic sheet

Building the Hot Air Balloons:
  1. Preparing the plastic sheet for making the balloon
    • a. If the balloon is being made from a Can Liner (i.e. a plastic bag), cut the sealed bottom off of the garbage bag.
    • b. Spread the plastic sheet (i.e. the can liner or the “Painter’s Plastic”) on top of the 40” x 48”board
    • c. Work out the wrinkles in the top and bottom layers of the plastic.  
If needed, use masking tape to hold the plastic sheet to the board.
 
  1. Making the Hot Air Balloon With a Soldering Iron
    • a. Place the Balloon Pattern on top of the plastic sheet.   Except for the very bottom of the balloon pattern, make sure that there is plastic outboard of the Balloon Pattern and that the Balloon Pattern in inboard of the edge of the board that is your working surface.
    • b. If you are going to use a Heat Gun to seal the edges, then skip this step.   After the Wood Burning Soldering Iron has warmed up, the edge of the balloon can be sealed by slowly pulling the soldering iron along the edge of the balloon pattern.   When using the soldering iron, make sure to not stop in one spot, as you can burn your working surface.   Dispose of the excess plastic and remove the Balloon Pattern.
      Note: With the Wood Burning Soldering Iron it is possible to make balloons by drawing the desired shape on the plastic sheet and trace along the line with the soldering iron.
      Also, with the Wood Burning Soldering Iron, it is possible to make balloons by drawing the desired shape on the plastic sheet and trace along the line with the soldering iron.
    • Your balloon is now ready fly.




OR ..
  1. Making the Hot Air Balloon With a Heat Gun
    • a. Trim off the plastic sheet that extends ¼ - ½ inch beyond the edge of the Balloon Template.
    • b. Turn the Heat Gun on its highest temperature and fan speed.
    • c. As shown in the picture, point the Heat Gun at the excess plastic sheet.   As you are doing this, use your other hand to hold the Balloon Pattern against the working surface (i.e. to keep the plastic underneath the Balloon Pattern from melting) and keep this hand away from the heat of the Heat Gun.
    • d. As the edge of the plastic sheets melts together, continue to move the Heat Gun along to the portion that hasn’t melted yet.
    • e. Once you have sealed the edge all the way around the Balloon Pattern, the balloon is ready to fly.




  1. Flying the Hot Air Balloon
    • a. If the bottom of the Hot Air Balloon has been sealed, use a scissors to remove the portion that is sealed.
    • b. To initially fill the Hot Air Balloon with air, insert the Heat Gun into the bottom of the balloon.   When you turn the Heat Gun on, make sure it is set to its lowest temperature and fan speed.   The metal tip of the Heat Gun musto be kept away from the plastic sheet.   Remember, the Heat Gun will melt the plastic.




    • c. When the balloon starts to raise, transition to having the Heat Gun pointed upward and the balloon above it.   In performing this transition keep the metal tip of the Heat Gun away from the plastic sheet.
    • d. Change the settings on the Heat Gun to its highest temperature and fan speed.   Continue to keep the tip of the Heat Gun away from the plastic sheet.
    • e. Continue heating the air in the balloon until the outside of the balloon feels warm.   While heating the air in the balloon, you will need to allow some of the air to exhaust out of the bottom of the bottom.
    • f. Once the balloon feels warm enough, release the balloon.
      Note: Overheating the balloon will cause the top of the balloon to distort or melt.
    Once you have flown your balloon, consider evaluating the following:
    • What effect would a longer heating time have?
    • What effect would vent holes on the top of the balloon have?
    • Would paper clip as weights on the bottom of balloon make it fly better?
    • What effect would taping the bottom of the balloon closed have?
    • What effect would a different thickness of plastic sheet have?
    • How would different shapes fly?