Introduction: Hovercraft

About: I enjoy building things more than actually using the things I build

This is a full size(4ftx8ft) one person hovercraft built over one summer for less than $200. It was built with no prior experience or knowledge of hovercrafts but with sheer determination to build something different. So check this project out, hope you like it.

Disclaimer (March 2013): I have not made any changes to this Instructable since the early days of this website, 2006.  Take this Instructable as an example of how not to build a Hovercraft.  The homemade thrust fan and unshielded rotating parts make this homemade craft pretty dangerous.  If your building a hovercraft of your own please consider the safety aspects large rotating parts and apply this understanding in your design.  For a great example of how to build a working and safe hovercraft see this Instrucable10-HP-Hovercraft

Step 1: The Skirt and Base

Lets start out with a little history, I built the hover craft during the summer between my sophomore and junior years of high school. It was built by a good friend, Brain, and myself Doug. Like I said I built the entire craft for less $200 including the engines and the fans. I will explain how I did it soon but lets start out some of the main things you will need to get started.

3hp Horizontal Shaft Engine $50 at a local lawnmower repair shop
4hp Vertical Shaft engine took it off one of my lawnmowers
5.2 moisture resistant Lauan Plywood 4ftx8ft
Styrofoam 4ftx8ft
1/2in Plywood 2ftx4ft
A couple 2x4 8ft
A couple 1x2 8ft
1/4in bolts and nuts 1in- 3in
Wood Screws 1/2in - 1in
Plastic sheeting Painters Sheet (this is the skirt material)
Brass Grommets with punch You can get this as a kit

This is about what I started out with but in no way is this everything youll need. Also keep in mind that this is how I did it, if you plan on taking on a project like this do it how you want to and with what is available to you. Use this as a guide so that you do not make the same mistakes I did.

Lets start out from the ground up. On a hovercraft the only thing that touches the ground is the skirt. The skirt is the part of the hovercraft that holds air to lift the craft. Like in the second picture my hovercraft has two engines, one for lift and one for thrust. The lift engine pushes air under the craft and the skirt holds the air in. As more air is pushed under the craft pressure builds up and lifts the hovercraft off the ground. This is how a hovercraft hovers, the only thing in between the base of the craft and the ground is air.

But before I designed the skirt I designed the base of the craft. It has to be light(this is the most important) and it has to be strong enough to hold the weight of a person and the engines and everything else. Keep in mind though that when hovering the craft is actually more stable than when its not. The air pressure helps to hold the weight evenly over the entire craft.

This said here is how I made the base. I got two sheets of 4ftx8ft lauan and a piece of 2in thick Styrofoam. The lauan was the cheapest and the lightest sheet of plywood I could find at home depot. One note, I got almost everything for this hovercraft at home depot. Lows or any hardware store will probably have the same items I got.

The base is just the two sheets of plywood with the Styrofoam sandwiched in between. Holes are drilled all the way through this sandwich and bolts are used to hold all of the components on the base.

Back to the skirt which is one of the more trickier parts of a hovercraft. It has to hold its shape under pressure and it has to be the right size. To big and it will drag on the ground which will slow the craft down or not let it move at all and to small and it will not hold enough air to sustain lift.

To overcome this I designed my skirt to have 8 different pieces that I sewed all together with nylon string. For each of the four sides of the craft there are two skirt pieces. A upper half and a lower half, which are same shape. The picture shows what each part looked like. Basically the same design for all four sides just different lengths. The skirt is actually smaller than 4ftx8ft by 2in on all sides. This is done so that the skirt can sandwich between the Styrofoam and the top piece of plywood. So you will need four longer skirt pieces and four shorter ones.
Each piece first needs its flap folded over and sewn. To sew the skirt I used a standard sewing machine and sewed along the seam lines which are 1/2in from the edge. Now take two pieces one short and one long and sew them together at the angled end. Now do this again for all the other pieces to form a two rectangles. Now put one rectangle on top of the other and sew along the outside perimeter. This forms the whole skirt but its not done yet.

Now duck tape along the seam for added strength then flip the skirt inside out so the seams are in the inside. Punch holes on the inside of the skirt in the middle of the flap on the top and the bottom of the skirt with the grommet kit. Put holes on all corners and every foot along the length of each side. Drill holes through the base that line up with the grommets. Sandwich the top of the skirt between the Styrofoam and the top piece of plywood and then use 1/4in bolts to hold it all together.

This completes the skirt and the base. This is the most general part of the build. The rest of the craft is built specific to the engines, fans and components I used, you will have to adapt these plans to fit your components.

Sorry about the pictures I could not get them to show up very well. I included the DWG file though. The last picture is the overall skirt put together showing the flap folded over with the dashed line and where holes should be put with the circles.

Step 2: The Lift Engine

The lift engine and fan were added next. Here is what I used, a 4hp lawnmower, a 20in dia. fan that I think came off a air conditioner, angle steel, a piece of sheet metal, some nuts and bolts.

I cut a big hole in the base with a jig saw and then added the engine. The angle steel as seen in the picture is in a u-shape that lifts the engine so the fan is not below the bottom level of the base. I welded these pieces together but they could be bolted together with a bunch of L-brackets. They are bolted to the base and connected with a piece of sheet metal. The sheet metal has a large hole cut in it with smaller holes around it for the bolts that hold on the engine. The larger hole is so the engine sits flat on the sheet metal. The fan is just bolted onto the engine shaft just like blade was when it was on the lawnmower. Then some 1x2s and more L-brackets were used hold on some aluminum flashing to make a fan shroud. You can get aluminum flashing at any hardware store, its used for roofing but all it is, is aluminum sheet metal. A bike brake and cable of an old bike was used to control the motor.

Step 3: The Thrust Engine

The thrust engine was a little bit harder than the lift. It has a larger fan, a pulley reduction and a large fan duct. I started off with the fan. It was hand made with a welder and some steel. This is not a good idea, the fan has to be perfectly balanced and the pitch of the blades has to match the power of the engine. I you are going to build a hovercraft do not build you own fan. I was lucky that my fan did not fly apart and kill me. Do not do what I did here and get a good fan to use.

So once you have a fan you need to build a duct. I used more lauan plywood to cut out the shape and screwed in a bunch of 1x2s to hold the two pieces together. Then I wrapped more aluminum flashing around the whole thing to make the duct.

The fan was mounted to a 1/2in shaft that ran through two brass bushings with a pulley on the other side. This was all mounted on a 2x4 and plywood frame. Then a smaller frame was made to hold the engine up so that the belt would fit. No type of clutch was used on the engine which is typical for most hovercraft. This finished the thrust engine and fan.

Step 4: Steering and Controls

The steering for a hovercraft is done through air deflectors placed behind the thrust duct. For these I just used the circle I had already cut out for the duct itself. I cut one of them in half and screwed a 1x2 on the rounded edge of each half. L-brackets were attached to the duct hold them on and allow them to turn. Then rope was attached to the deflectors and run through eye-bolts. The rope was criss-crossed under the duct so that moving the control stick left would turn the hovercraft left and right turns right. The control stick was just a piece of PVC pipe with a hole drilled through the bottom so that it could pivot.

The Thrust engine is controlled by a lawnmower throttle cable and the lift engine was locked into full throttle. I could have mounted the bike brake on the control stick but it would have been just one more thing to worry about so I just left it wide open.

Step 5: It Hovers!!!

So here is a picture of it finally hovering. Looks pretty good, but really the project did not go as well as planed. It hovered and I could ride it but that was while I was testing and it did not have the thrust engine or fan on it. Once I added the thrust stuff it would not hold all of the weight. All is not lost though, the build went well and I learned a lot.

So I you are planning a project like this here are a few tips so you do not make the same mistakes I make:
1. Use more powerful motors or motor if you build a single engine craft
2. Get already made fans do not try to build you own
3. Use light components, this is the most important it has to be a light as possible
4. If you do not know what you are doing, get some plans off the internet, try Universal Hovercraft they have got some good stuff

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