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Designing Electric Model Hovercraft

General Guidelines

Many people are put off the idea of building a working model Hovercraft by the supposition that a degree of sophistication is required, using high technology components, the Hovercraft itself being a recent invention. Those that do try often try the simplistic approach, using a fan from a vacuum cleaner and a skirt made from dustbin liner.

An effective electric powered model Hovercraft can be made from readily available components and materials for around £40, " batteries not included".

A simple source of power, for either lift or thrust, is the "540" type buggy motor. A model aircraft propeller, of between 5 and 7 inches diameter, with a pitch of 3 to 5 inches, is mounted on the motor shaft. This is done using an adaptor, available from most model shops. The adaptor looks like an aluminium nut and bolt, drilled to suit the motor shaft and with a grub screw to hold it in place. The motor is driven by a 6 to 8 cell nicad pack.

Vacuum cleaner and hairdryer fans are impractical for direct drive from one of these motors, as the motor needs to run at around 10,000 rpm, whereas the fans are designed to run at much lower speeds. Gearboxes could be used, but these add to the weight and complexity of the model.

The lift motor can be arranged to discharge air directly under the Hovercraft, or into the flexible skirt. A simple structure may be made in one of two ways. The first method is to build a central box running the full length of the Hovercraft. Light side decking, supported by outriggers, will give the craft the necessary cushion area. The second method is to make a raft covering the whole area of the craft, with air being discharged around the edges. The structure may be made from 1/16 inch thick plywood, or thinner plywood, or balsa wood.

The skirt can be made from ripstop nylon of the sort used for kites. This is generally available and is lighter and more flexible than synthetic sailcloths. The skirt shape can be a bag section, shaped around a suitable tube. For the more adventurous, simple geometry and trigonometry can be used to draw the developed flat skirt panels.

A more effective, but also more complicated, skirt can be made by attaching skirt fingers to the lower edge of the bag section. The fingers are made from triangular pieces of material. Their tips are sewn or glued to the bag, and the remaining two corners are glued or tied back to the underside of the Hovercraft.

The " Finger Trouble " model is a simple radio controlled craft, using one such motor for lift and another for thrust. The model was about 30" by 15", giving a cushion area of 3 square feet. The craft weighed 4lb. This gave a cushion pressure of 1.33lb/sq ft. It is recommended that you keep the weight of the craft low, and have a cushion pressure no greater than 2lb/sq ft.

Providing that you keep to these guidelines, you should be able to build a cheap and practical model Hovercraft.