Radio Controlled Hovercraft

Hi ! This tutorial is a summary of a more detailed guide that I previously published here. This model is a good compromise between cost, ease of construction and performance - plus, if you make a good choice of colors, it will look amazing :-)

I will be looking forward to your successful completion of this model, and if you could show me a picture of your finished model, it will be a great reward for my work. Do not hesitate to ask questions if you have some.

Please note that this tutorial is under the Creative Commons 4.0 BY-NC-ND licence.

Please visit this page to see the detailed components list. To summarize, you need :

- a 3 mm thick polypropylene plate (or two plates if you want two different colors like me), 30 screws, piano wire, cable ties, synthetic thread

- a piece of wire mesh, a piece of cardboard, a garbage bag, a few packing bubbles

- a Mabuchi 7520 electric motor, a 30 amps ESC, a mini servo, a 5.5" diameter propeller and its adaptor, a 7,4V LIPO battery, a radio set (transmittor + receptor) with two channels

Cut a polypropylene plate 50 cm long by 25 cm large. The polypropylene channels must be lengthwise. Each time you cut a polypropylene piece, you can deburr the edges to get a smoother finish.

Draw four dots, each one being at 7,5 cm from both edges of the hull. Draw two lines to connect the dots as shown. These two lines measure 35 cm long and are separated by 10 cm. With a screw, drill three holes on each line, one at the center and the others at 2,5 cm from both ends of the line.

Cut two polypropylene strips 35 cm long by 2,5 cm large - again the channels must be lengthwise. Put them aside, we will use them later to set the skirt under the hovercraft.

The side on which you draw the two lines is the underside of the hovercraft. Turn the hull over to work on the top.

In the center of the hull, at 1,5 cm from one of the edges, draw a 92 mm long by 65 mm large rectangle. Cut three sides of the rectangle as shown on the picture. Using a non-sharp tool, strongly mark the last uncut side of this rectangle to break the polypropylene channels, then fold this piece. You obtain the flap that will deflect part of the air towards the skirt.

Cut a 22 cm long by 8 cm large polypropylene plate, with the channels lengthwise. This is the motor support.
At 6,4 cm from the edges of the motor support, draw two straight lines and strongly mark them with a non-sharp tool. Then fold this piece.

Screw the motor support from below the hull, above the air deflector flap. Note that no screw should overlap on the two 35 cm lines you have drawn previously. Let a space of 1 cm between the rear of the hovercraft and the rear of the motor support.

Fold the air deflector flap to bring it as close as possible to the motor support. Then screw the flap to the motor support with a screw on each side. Finally, add duct tape on the top, right and left of the air deflector flap to get an airproof compartment.

Connect 50 cm of wire (16 awg is recommended) to each polarity of the motor. Put the propeller adaptor and the propeller on the motor axis. To prevent injuries and damage, double check if the propeller is firmly attached on the motor shaft.

Cut two pieces of piano wire, 25 cm long. Make three turns with the piano wire around the two motor mounting screws - you must get a 50° angle, a kind of a V-shape. You should get a length of around 8 cm under the motor, and around 15 cm on the sides. Work the wires until everything is folded correctly and as straight as possible.

Pre-perforate the motor support in the four spots indicated with a straight rod of piano wire, then slowly insert the four "motor legs" into the motor support.

At the back of the motor support, on the sides, there should be a few extra centimeters of piano wire. Leave 1 cm and cut the rest. Bend the two rods inside the motor support.

Drill two holes in the motor support at the rear of the motor to pass a thick cable tie : it will bring the rear of the motor closer to the motor support. We continue with super-gluing the servo behind the motor and placing the radio receiver just behind the air distributor flap. Close the compartment with a polypropylene plate.

Finally, add electrical tape or heat shrink tubes to insulate the solders between the motor and the wires.

The flaps are inserted into the motor support using a long rod of piano wire, bent into a U-shape. Then we connect them to the servo with synthetic wire. Connect the two flaps with another rod of piano wire, also bent into a U-shape, to synchronize them.

Take the two polypropylene strips you cut earlier (35 cm long by 2.5 cm large) and screw them under the hovercraft through the six holes previously drilled, using 2,5 cm long screws. The strips must be screwed exactly on the lines you have drawn at the beginning.

Cut a rectangle of wire mesh 38 cm long by 18 cm wide, then fold it to get the shape shown of the picture : 16 cm height at the back, a width of 5 cm, and 17 cm at the front : fold this extra centimeter as shown on the picture.

Make the necessary cutouts at the back of the wire mesh to allow the motor support and motor to pass through. Round the top of the wire mesh by cutting a few meshes (from 9 cm height, cut 1 cm towards the center every 2 cm of height).

Using a polypropylene reinforcement, screw the front of the wire mesh into the two polypropylene strips below the hovercraft. These two screws should be located around 14,5 cm from the rear of the hovercraft.

The rear of the wire mesh can be joined with the "motor legs" using small cable ties. Also use a few duct tape tabs to stick the bottom of the wire mesh to the bottom of the motor support - that was not done yet when I took the picture, but it is absolutely necessary.

Complete the propeller protection with a polypropylene strip of 6,2 cm width and 48 cm length (channels lengthwise for better aesthetics). To give it the shape of the wire mesh, make a first fold at 11,5 cm from one edge, make another one 5,5 cm further, then 13 cm further and again 5,5 cm further. Screw this protection from below the hull with two screws on each side.

Pass the servo extension cable through a mesh, as far as possible from the propeller (you can see it on the left) and secure it with a bit of tape.

The center of gravity of this model must be located not exactly in the middle of the hovercraft, but rather between 22 and 22,5 cm from the rear. You need to define where your battery should be located for the hovercraft to be correctly balanced.

When you have defined the place where your battery must be located, drill two holes to take out the electric wires previously inserted in the hull channels. Mines are at 15 cm from the front because I will use a heavy NIMH battery (which I do not recommend at all). These holes will be drilled elsewhere if you use a lighter LIPO battery.

Once you have made all the solders and secured them, you need a box that will contain the battery, the wires and the ESC. Mine is not pretty nor clever, you can do things differently and add a power switch to disconnect the battery without removing the cover, for example.

The type of skirt we will use is a "vented bag skirt" made with trash bag. Soldered together with a soldering gun, these weird parts will give the hovercraft skirt that characteristic cylindrical shape. The corners template is available here.

You will now tape the skirt under the hull. It is imperative to take your time to do this correctly (up to an hour) to make sure everything is airproof and waterproof. This is the most difficult part of the build.

Tape the "outer rectangle" of the skirt to the hull, edge to edge. Then, use double-sided tape to stick packing bubbles to the hull on the right and left sides of the hovercraft. Finally, close the skirt by taping the right and left sides on the two polypropylene strips, edge to edge again, as shown on the third picture.

Cut a 10 cm piece of duct tape. In its middle, stick another 5 cm piece of duct tape, so you get only two sticky parts of 2,5 cm at the extremities. This piece of tape will keep the back of the skirt from vibrating and tearing. It must keep the skirt in place without hindering its inflation. It is not useful to do the same at the front.

It is possible that some water gets inside the rear of the skirt when you operate it on water. Drill three holes at the rear of the skirt, so that the water that would have entered can flow out.

Turn everything on and set the throttle to the maximum to check if the skirt inflates well everywhere and if the back of the skirt does not vibrate. If it does, cut the piece of tape and place another in a different way. Also check if the hovercraft seems well balanced - if not, your battery may be positioned a little too far to the right or to the left.

Before operating your hovercraft on a waterhole, I recommend that you give it a first try in a bathtub.

Again, as this is just a summary of this build, you can check my website to get all the details. I will be happy to answer your questions if you have some. Good luck :-)