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This activity introduces students to pneumatic principles that defy gravity and allow a hovercraft to work. Students will operate a simple hovercraft model and build their own hovercraft designed to produce and control forward motion over land or water.

Figure 1: Student project examples of hovercrafts

A hovercraft travels over land and water on a cushion or bubble of low-pressure air.  A hovercraft has one or more blowers that blow air underneath the craft, which is contained by a skirt.  The skirt that is around the perimeter of the hovercraft performs an extremely important function in containing the air cushion.  By using a skirt, the amount of engine power required to lift the craft is considerably reduced and as an added benefit, extra hull surface clearance is obtained.  The skirt is a long strip of material that is mounted onto the underside of the craft.  When the skirt is inflated, it lifts the hovercraft.  The escaping air coming from where the skirt touches the ground is what creates a friction-less cushion of air.  Because the hovercraft has practically no friction, it takes little force to move the craft. 

The diagram below shows the basic principle of a hovercraft.  Air is directed underneath the craft by a blower, and the air that escapes out of the flexible skirt creates a near frictionless environment which enables the craft to hover.  The craft can move forward and turn by using propellers to propel the craft.