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Rocket Science at HomeMake a Hovercraft You Can Ride

Safety is the MOST IMPORTANT thing to pay attention to!

This activity should be performed with an adult, following all instructions here, as well as all the instructions for the tools used and those provided by the adult present and the work place you are in.

Image: hovercraft
Completed project

Your objective is to build a hovercraft you can ride.

Just like NASA engineers do when they start a spacecraft, airplane, or other design, you'll need to start with basic requirements. We've provided basic requirements for you here:

Requirements
  • Your design must be safe.
  • You must use an electrically-powered leaf blower or vacuum cleaner motor and fan housing to power your hovercraft.
  • A power cut-off switch must be provided to enable the rider to stop the hovercraft at any time.
    The extension cord you choose to use with your hovercraft must be rated for the motor of the vacuum cleaner or leaf blower you choose.
  • Any sharp edges must be filed down and wood surfaces should be sanded to avoid splinters. Any exposed sharp points or edges that cannot be easily cut off, filed or sanded should be covered. For example, any wood screw points that happen to be exposed after assembly should be covered prior to use. Silicone caulk can be dabbed over screw ends to provide a rubbery safety cover.
  • The bottom surface of the hovercraft must be smooth. It cannot have any protruding screws or other objects that would scratch the floor (with the exception of the lid and screw heads that go in the center).
  • Your hovercraft must lift itself and one human off the ground. The amount of weight your hovercraft can carry will vary depending on the design you come up with, but we recommend that initially you don't expect your hovercraft to carry anyone more than about 50 kilograms (110 pounds). It may actually carry more or less, and there are ways to make your hovercraft carry heavier individuals. Only one rider is to ride the hovercraft at any time.
  • A chair for the rider must be securely attached to the hovercraft.
  • The rider must always sit in the chair (NEVER stand) while the hovercraft is operating.
  • You must test and operate your hovercraft on a flat, dry surface.
  • The hovercraft should have one adult operator present at all times to operate the hovercraft safely and to give the slight push and pull that will be needed to move the hovercraft around on the floor. The hovercraft should be operated at slow speeds across the floor.
  • Depending on the noise of the motor, the rider and operator may need earplugs or other hearing protection. Follow all instructions for the safe operation of the vacuum cleaner or leaf blower you choose.
Materials/Equipment
  • Eye protection, hearing protecting, dust mask, gloves and any other safety gear required or recommended for the tools you are working with and environment you are working in.
  • A shop-type vacuum cleaner or leaf blower. You don't need the hoses or attachments, just the part that has the motor and the air inlet and outlet. You need something that has one simple air outlet. You'll be using it not as a vacuum, but as a blower to push air under your hovercraft. No matter what you use, we'll call this "blower" for the rest of the instructions.
  • A heavy extension cord rated for the vacuum cleaner or leaf blower you choose.
Caution! Inspect the entire length of your extension cord and the cord on your blower to make sure it is not cut or frayed. Be sure to use an extension cord with the correct rating. Also inspect the blower housing to ensure the housing isn't cracked and there are no exposed circuits or conductors.
  • 1- to 1-1/4-centimeter (3/8th- to 1/2-inch) thick plywood. You'll nee enough to make a flat circle or disc at least 102 centimeters (40 inches) in diameter (1-centimeter or 3/8th-inch plywood may need some additional wood pieces to act as stiffeners).
  • A chair that is less than or equal to 53 centimeters (21 inches) from the floor to the seat and does not recline, swivel or roll. It will be securely anchored to the plywood base. Since it is likely to be a chair that you use in your home, be careful to not damage it when you attach it to the base.
  • Polyethylene plastic sheet, at least 6 mil (1 mil = 1/1000 of an inch) thick. Enough to cover the entire disc of plywood with at least 6 inches overlap all the way around the perimeter. It may be wise to get extra plastic. Color is not important.
  • An electrical switch. A power strip with a built-in switch is acceptable and easy to use for these purposes. You should tape over any outlets not used.
  • Saw (a saber saw should be all that you need, but other saws will work as well). You MUST follow all the instructions for your saw(s).
  • Sandpaper or foam sanding block
  • Plastic lid from a coffee can or whipped topping -- or other similar thin plastic disc.
  • Flathead wood screws (size will depend on how you design your hovercraft)
  • Duct tape
  • Staple gun
  • Electrical tape
  • Scissors or a utility knife suitable for cutting the polyethylene.
  • A rope or webbing, about 2.5 to 4 meters (8 to 12 feet) in length.
  • Tie-wraps (optional)
  • Permanent marker (optional)
  • A single-hole office hole punch to punch holes in the polyethylene (optional) (a utility knife or hole punch for leather and a hammer will work as well).
  • Foam pipe insulation (optional) for the circumference of the hovercraft disc.
Instructions

Safety is the Number 1 priority!

Be sure to read and follow the safety requirements and recommendations for the tools you are using and those stated by the adult you are working with. Always wear eye protection when building your hovercraft. Always wear ear protection when operating loud items such as saws. Always wear dust masks when you are working with tools that generate dust. Gloves should be worn when working with rough wood to help avoid splinters.

1
 CAUTION! READ and FOLLOW the manual for your saber saw, including all safety notices. NEVER place your hand or fingers under the board you are cutting. The saw blade will be exposed on the underside of the plywood.
Mark and cut out the plywood disc. A disc of at least 102 centimeters (40 inches) in diameter is recommended. You want a large surface area disc to lift the weight, and you also want your hovercraft to have a wide base so it is stable. Sand the edges to get rid of and roughness and splinters. Pick one side to be the top and one to be the bottom.
2
Image: hole for blower
Picture 2
Mark a hole on the plywood large enough for the blower exhaust. This should not be in the center of the disc as you are going to cover the center later with the coffee can lid. It should be offset to one side. Also consider how your blower and chair will sit on the disc later and make sure the blower and chair will work without interference. Cut the hole. (Picture 2)
3
 CAUTION! When using a utility knife, always be sure the sharp edge is pointed away from anyone nearby, including the person doing the cutting.
Measure and cut a circle from the plastic sheet. You need enough to cover the underside of the disc -- with some slack -- and then enough extra to wrap around over edge to the top of the disc where you will staple it near the perimeter. We recommend you make the plastic circle at least 15 centimeters (6 inches) in radius (30 centimeters, or 12 inches in diameter) larger than the plywood disc. You can always cut off extra later. You will be forming a bag out of the plastic and the plywood disc and so you will not be pulling the plastic taut over the plywood. The bag will fill up with air that will travel out a number of small holes you will cut in a later step. It is this air that will lift the hovercraft off the ground.
4
 Turn the disc over so the bottom is facing up. Place the circular plastic sheet over the plywood disc lining up the centers. Place the lid -- a coffee can or whipped topping lid -- over the center of both. With a permanent marker, trace a circle around the lid onto the plastic sheet. Draw a second concentric circle on the plastic sheet about 7.5 centimeters (3 inches) smaller in radius than the outer edge of the plywood disc. These circles can be quickly hand-drawn. They are only to show you approximately where to punch the small holes in the plastic.

Remove the plastic lid.

5
 Using a single-hole office paper hole punch, a utility knife, or hole punch for leather, punch or cut a number of small holes relatively evenly spaced over the surface of the plastic sheet in the area between the two circles. You are creating the exit holes for the air to leave the hovercraft to lift you off the ground. If you use an office hole punch, you can do this by creating small folds in the plastic just where you want to punch, pushing the fold ½ way or less into the punch, and then punching the hole. If the office hole punch method doesn't work, a utility knife or a leather punch and hammer can be used.

This may require some trial and error. In our unit, we used about 100 holes about the size of those in a looseleaf piece of paper. The number and size you need may vary. If you don't cut enough holes, you can add some even after you've attached the plastic sheet to the plywood disc. You may also find that you need some additional holes closer to the edge of the plywood than the circle you drew in step 4. You can add more at any time. When someone is riding the hovercraft you don't want to see these small holes around the perimeter. If you can see them, then they are just wasting air by blowing it out to the side instead of using that air pressure to lift the hovercraft.

If you use a utility knife, you should be careful not to scratch the table or floor you are working on. It is best to put a protective surface underneath. One suggestion is to cut the holes directly on the plywood disc. While the plywood needs to be smooth in general, you don't need to worry about light scratches in the surface of the plywood from the knife.

6
Image: duct tape around blower
Picture 6
CAUTION! Most leaf blowers have a long nozzle that you may need to remove to fit the blower onto your hovercraft. When working with the blower with the nozzle removed, MAKE SURE the blower is UNPLUGGED from the power source. If you do remove the nozzle from the blower, be sure the blower mount or other part of your design fully covers any exposed portion of the fan or impeller.
Design and build a mount for your blower. Attach the mount to the top of the plywood disc. You can also do this step at other times, but this order allows you to use flat head screws from the bottom side of the disc to attach the blower mount (before you attach the plastic sheet).

Depending on your design, you can either attach the blower to the mount and plywood disc now, or do that later. Use duct tape to seal any gap between the blower outlet and the plywood disk or blower mount. If you can design a mount that lets you attach the mount now, and the blower later, it will make some of the remaining steps easier.

7
Image: staple plastic and duct tape perimeter
Picture 7
CAUTION! READ and FOLLOW the manual for your staple gun, including all safety notices. NEVER point the stable gun at anyone. Only use it when it is placed firmly up against the surface you are applying staples to.
Place the plastic sheet on the floor or table, and place the plywood disc on top with the top of the plywood facing up and the centers aligned. Wrap the plastic around the plywood disc and staple to the top of the plywood at the perimeter. Leave some slack. We recommend 1.2 to 2.5 centimeters (1/2 to 1 inch) of extra plastic sheet along the radius all the way around the plywood disc as the plastic lays flat under the plywood. This too may require some trial and error. Place duct tape over the staples and edges of the plastic to seal this edge.
8
Image: cover screws and anchor rope
Picture 8
CAUTION! If the tips of your screws come through the top side of the plywood disc, cover the point with something to avoid injury. Silicone caulk or silicone glue can be used to make a rubbery protective cap.
Attach the coffee can lid to the center bottom of the disc with flathead wood screws. Use at least 10 screws evenly spaced near the perimeter of the lid. This keeps the hovercraft more evenly balanced by making the plastic bag into the shape of a donut when it inflates. We recommend you consider using a thin washer with each flathead screw to reinforce the attachment. The screw heads will stick out a bit further, but should still not interfere with the operation of your hovercraft.
9
Image: anchor rope
Picture 9a
Image: cover screws and anchor rope
Picture 9b
Attach a rope to a point on the top of the disc or the blower mount. This will be used by the operator to pull the rider along on the floor.
10
Image: anchor rope
Picture 10a
Image: closeup of mount for chair and tapes
Picture 10b
Attach the chair so that the rider's weight will be approximately located over the center of the disc. Remember that the rider and chair are probably going to be heavier than the blower, and you are trying to place the center of all the mass over the center of the hovercraft disc.
11
Image: mount for emergency shutoff
Picture 11a
Image: emergency shutoff switch installed
Picture 11b
Image: leaf blower top
Picture 11c
Image: emergency shutoff switch
Picture 11d
CAUTION! Be sure the emergency stop switch and the power switch on the blower are both in the "OFF" position prior to connecting either to the power source.
Attach the emergency stop switch to the chair where the rider will easily reach the switch. This will let the rider stop the hovercraft any time. Connect the extension cord and blower to the emergency stop switch. If you are using a power outlet strip as shown in the photos, connect the blower motor cord to one of the outlets in the strip, and the plug from the power strip to the extension cord. Use electrical tape to cover unused outlets in the power strip and tape, clips or tie-wraps to secure the cords to the hovercraft.
12
Image: tie down electrical cable
Picture 12
Anchor the extension cord to the hovercraft near the attachment point for the rope, using clips or tie wraps.
13
Image: slack in cable
Picture 13
Lay the rope and the cord out on the ground along side each other. Pull the rope taut, and tape the extension cord to the rope every 45 centimeters (2 feet), leaving some slack in the extension cord. This will allow you to move the hovercraft by pulling on the rope and not straining the extension cord. The operator will stand about 1.2 to 3 meters (4 to 10 feet) away from the hovercraft and pull on the rope to move the hovercraft.
14 Clear an open, dry, flat space. A garage floor works well.
15
Image: bag inflated
Picture 15
Test your hovercraft with no one riding it. See that it lifts off the floor and floats about as the operator pushes on it or pulls on the rope. Test the emergency stop switch to turn the hovercraft off.
16 

CAUTION! Never suddenly stop, start or redirect the motion of the hovercraft as it glides across the floor. Always move the hovercraft slowly across the floor and gently stop, start or redirect it.

Never ride or test the hovercraft in a wet or damp area. Be sure the entire length of the electrical power cord, from the hovercraft to the power outlet, is also in a completely dry area as well.

Always have an adult present when operating the hovercraft.

The rider should ALWAYS be sitting in the chair during the hovercraft operations.

If it looks like it's working fine, turn the hovercraft off and have the first rider get onboard. Only one rider should ride the hovercraft at once. The adult operator should turn on the blower and the give the hovercraft a slight push. The rider should see if the craft is balanced -- or which way the chair should be moved to balance it.
17 If the hovercraft seems unbalanced, stop the power and get off the hovercraft. Move and re-attach the chair, and try again.
More Images
Image: overview from front
Overview from front
Image: overview from rear
Overview from rear
Image: overview from side
Overview from side
Image: overview from side
Overview from side

Congratulations. You've just designed and built your very own hovercraft!

Write to us and tell us how it worked!

Optional:

You may wish to put some padding around the outer edge of the hovercraft disc. Foam pipe insulation works well for this. Just staple is around the perimeter, over the top of the plastic.

You may want to tie a second rope to the hovercraft so that a second operator can pull from the opposite side of the first operator.

Caution! Again, only move the hovercraft across the floor at low speed. Do NOT stop, start, or redirect the hovercraft suddenly. The rider should ALWAYS be sitting in the chair during the hovercraft operations.
 
 
Feedback/questions: brainbites@nasa.gov

Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 12/07/2004
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