A hovercraft may look like some high-tech alien vehicle, but the concepts behind its inner workings are really quite simple. Building a hovercraft is an excellent way to investigate the principles of air pressure, friction, lift, thrust, and drag and serves as an excellent motivator for hands-on discovery — for even the most reluctant of learners.
A hovercraft is an ACV (air cushion vehicle) that rides on a pillow of slightly pressurized air. The hovercraft sports a skirt around its perimeter designed to contain air generated by a fan, or in the case of our craft, a repurposed leaf blower.
The air contained by the skirt in turn creates a cushion that lifts the hovercraft a small distance off the ground. Note: The weight a hovercraft can lift is easily calculated by multiplying the cushion pressure by the area of the craft.
Once lift is achieved, the craft uses directed air to create a forward thrust, allowing the vehicle to be forwardly mobile. A typical hovercraft creates this forward thrust using a propeller or propellers that push air toward the back of the vehicle. Using the principles of lift and thrust, as explained above, the hovercraft operates much like an airplane.
Now that the craft has forward momentum, it must be steered. Steering is achieved in various ways, depending on vehicle design. A system of rudders placed behind the fan may be used to direct air in different directions, allowing the vehicle the freedom to turn. This configuration is similar to the mechanism used to steer some boats. Other hovercrafts use subtle shifts in the operator’s body weight to steer, a skill that takes practice to master.
The Museum’s simplified hovercraft was constructed by our own Carolyn Leap using a collection of ideas with a few modifications:
• Rounded off corners on a square of plywood in order to reduce the weight of the vehicle – a circle of plywood is an even better option for reducing weight.
• We sought help from the Exhibits Department to cut a hole to accommodate an unusually shaped leaf-blower outlet.
• We used a plastic tablecloth completely reinforced with duct tape because the plastic seemed inadequate on its own.
• Reinforced the skirt’s attachment by stapling AND taping around the edges.
• Added pool noodles (split along one side) instead of pipe insulation as a bumper
• Added duct tape flaps (sticky sides together) and attached them around the perimeter of the nozzle to create a more effective seal to improve lift.
This hovercraft is used in the Museum’s Xplorations Summer Camp Programs to illustrate various physics concepts. Our hovercraft does not create its own forward thrust and has no steering mechanism, so the craft and rider are guided by the instructor. Take a look at the fun pictures of one of our campers, Noah, as he rides on a pillow of pressurized air!
For instructions on how to build your own hovercraft, click here.
Sciencebuddies.org and Wired.com have some great additional info. See you same time, same place next month!