Adventures in Science and Technology

[Engineering]

This project idea comes to you from Discover E in Edmonton, Alberta.

To construct and test a hovercraft, thus gaining a good insight into how engineers use science and technology to create vehicles that can travel over various types of terrain in an innovative way.

Hovercraft act on the principles of pressure. A common misconception about hovercraft is that they float several feet off the ground. So why do we call them hovercraft? Well they do float, but only a fraction of a millimeter. If they only hover a millimeter in the air, then how can they travel over various terrain? Hovercraft have a large cushion of air that they are continuously riding on. When they hit an object the air pocket deforms to adapt to the new terrain.

Hovercraft have powerful motors that suck air down and push it out through the bottom of the vehicle. This process creates a very thin layer of air between the hovercraft and the ground, resulting in very little resistance. This is how an air hockey puck moves; it has air blowing up from below.

The hovercraft that you will construct in this project works on the same concept of pressure. Instead of having a powerful vacuum, dry ice and water are used to levitate the hovercraft. The pressure that results from the reaction between the dry ice and the water builds up in the cabin area and is forced out through the straws to the bottom of the hovercraft. This process creates lift in the hovercraft allowing it to float off the ground.

[Engineering Boy following the procedure]

4" x 6" styrofoam body
2 styrofoam cups
1 straw
silicon (from a large tube, dispensed with a caulking gun)
dry ice
water

Drill two straw-sized holes in the centre of the styrofoam body about 2 cm apart.
Cut a straw in half and place each half through one of the holes in the styrofoam body, but not so far down that it comes out of the bottom of the body. The straws should stick out from the top of the craft about 7 cm. Silicon the straws into the holes so that there is an airtight seal formed, with the only air flow going through the straws.
The first styrofoam cup will be the cabin of the hovercraft. It will contain the dry ice and water. Cut the bottom of the cabin cup off so that when turned upside down on top of the hovercraft body it is the same height as the straws.
The second cup will serve as a hatch. Cut the top of the hatch cup off so that when turned upside down it is about 5 cm in height, and it fits snugly over the cabin cup forming a lid.
Silicon the cabin cup to the top of the styrofoam body. It should sit upside down. Be sure to use enough silicon to ensure that there are no air leaks underneath the cabin cup. Allow 20 minutes to dry.
Fill the cabin with warm water and a few small pieces of dry ice. Fit the hatch snugly on top of the cabin so that the only air flow is the high pressure stream through the straws blasting underneath the craft.
Make sure that the surface that the hovercraft is gliding over is smooth and free of debris.
Give the hovercraft a small push and watch it glide.

Hovercraft can have many applications. They are unique as transportation vehicles because they are amphibious: they can move over land and water. In England, the Association of Search & Rescue Hovercraft uses this fact to provide special rescue services. This association uses a network of hovercraft to support existing emergency services in difficult search and rescue situations. The Canadian Coast Guard purchased two new hovercraft in April 1998 to help with search and rescue in Canada. These hovercraft will also be used for icebreaking for flood control, assisting with fisheries patrol, and many other tasks. The United States Postal Service (USPS) is trying out new uses for hovercraft too. The USPS is trying out delivering mail by hovercraft to the three tundra villages Atmautluak, Kasigluk, and Nunapitchuk in Alaska. Many people enjoy using hovercraft for fun as well. The world's first hovercraft race took place on Lake Burley Griffin in Canberra, Australia in 1964. Only 14 hovercraft participated in the first race, but hovercraft racing now is becoming a very popular and fast-growing sport.

Produced by Galactics.
Comments: galactics@spacesim.org.
Last updated on 14 August 1998.