Let's begin with the hovercraft hull. Cut a corrugated plastic sheet measuring 50 cm long and 25 cm wide. Make sure the internal channels run lengthwise.

Whenever you cut a piece of corrugated plastic, it's a good idea to deburr the edges for a cleaner finish.

Mark four dots, each positioned 7.5 cm from both the side and end edges of the hull. Then draw two lines connecting the dots as shown. These lines should be 35 cm long and spaced 10 cm apart.

Drill three holes along each line: one in the center, and the other two 2.5 cm from each end.

Cut two corrugated plastic strips measuring 35 cm long and 2.5 cm wide — again, make sure the channels run lengthwise. Set them aside; we'll use them later to attach the skirt beneath the hovercraft.

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

In the center of the hull, 1.5 cm from one of the edges, draw a rectangle measuring 92 mm by 65 mm. Cut along three sides of the rectangle, as shown in the picture.

Using a non-sharp tool, press firmly along the remaining uncut side to break the corrugated plastic channels, then fold the piece inward. This creates the flap mentioned earlier — it will redirect part of the airflow toward the skirt.

Cut a corrugated plastic sheet measuring 22 cm long and 8 cm wide, with the channels running lengthwise. This will be the motor support.

At 6.4 cm from each end of the motor support, draw two straight lines and score them firmly using a non-sharp tool. Then fold the piece along those lines.

Screw the motor support to the underside of the hull, positioned above the air deflector flap. Make sure that no screw overlaps the two 35 cm lines you drew earlier.

For all steps of this build, use your longest screws by default (3.5 to 4 cm), unless stated otherwise.

Leave a 1 cm gap between the rear of the hovercraft and the back of the motor support (see next picture).

Fold the air deflector flap so that it sits as close as possible to the motor support.

Then secure the flap to the motor support with one screw on each side.

Apply duct tape to the top, right, and left sides of the air deflector flap to create an airtight compartment.

Solder two electrical wires to the motor (about 50 cm each to ensure you have enough — you can trim the excess later).

I made the mistake of buying single-stranded wires, which are much less flexible and made soldering unnecessarily difficult.

Attach the propeller adapter and the propeller to the motor shaft. The Master Airscrew propeller I'm using here originally had a very narrow bore, which I carefully widened to 5 mm by drilling it. Since this propeller is top of the line, the extra effort is worth it.

The propeller must fit tightly onto its adapter. If necessary, widen the propeller's bore, or add a shim to reduce its inner diameter. To avoid injuries or damage, double-check that the propeller is securely fastened to the motor shaft.

Cut two pieces of piano wire, each 25 cm in length. Wrap the piano wire around the two motor mounting screws, making three turns.

Ultimately, the piano wire should form a V-shape, creating a 50° angle (as better illustrated in the next picture). You should have a total length of approximately 8 cm of piano wire under the motor and around 15 cm on the sides.

Bend the piano wire at a 90° angle so that it runs parallel to the motor axis. For the wires under the motor, make the bend 2 cm from the screw. For the sides, bend at 3.5 cm from the screw. Work the wires until everything is properly folded and as straight as possible—note that in the picture, this step is not yet completed.

This is a challenging step. Take your time and don't hesitate to start over if the result doesn't seem good to you.

Finally, pay attention to the length of the two mounting screws: they should be long enough to secure the piano wire to the motor. However, if you cannot turn the propeller manually without encountering resistance, they are too long and need to be shortened or replaced.

Pre-drill the motor support at the four indicated spots using a straight piece of piano wire. Then, carefully insert the four "legs" of the motor into the motor support.

Ensure that the entire length of the motor lies flat on the motor support, with the shaft positioned precisely in the center. If the result differs, the piano wire may be incorrectly bent, and you will need to adjust it for a better fit.

There should be a 5 mm gap between the hull and the propeller when the propeller is oriented vertically.

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

Drill two holes in the motor support at the rear of the motor to thread the thickest of your cable ties through. Secure it around the motor, then cut off any excess. Be careful not to overtighten, as this may deform the motor support over time.

Ideally, the attachment of the cable tie should be inside the motor support, not outside as shown on the left, to avoid creating additional drag.

If you have not done so already, add electrical tape or heat shrink tubing to insulate the solder joints between the motor and the wires.

Next, proceed by super-gluing the servo behind the motor. Ensure that the servo arm is aligned, or nearly aligned, with the motor axis. Fine-tuning can be done later using the radio trim.

Note that the servo arm will actually point in the opposite direction, towards the rear, as shown in the following pictures.

Connect the servo extension cable and the servo to the appropriate channels on your receiver. With my 4-way radio set, the servo connects to the "aileron channel," and the extension cable connects to the "elevator channel." For specific instructions, refer to your radio manual. Wrap the receiver in bubble wrap and secure it to the air deflector flap with tape, while the antenna can be taped to the hull, next to the motor support.

Route the two electric wires inside the corrugated plastic plate, as shown in the picture, ensuring they are not too close to the motor support.

Close the back of the motor support with a small corrugated plastic plate, ensuring the channels run lengthwise for a smoother finish. It is important to place the screws at the top of the plate, as shown in the picture, rather than on the sides.

Additionally, insert two screws from the underside of the hull into this small plate. This will correct the deformation that typically occurs at the rear of the hull after folding the air deflector flap.

If you have made the correct connections for the servo and the ESC cable, there should be no need to access the receiver again during the assembly.

Cut two corrugated plastic pieces, each 10 cm in length by 7 cm in height, with the channels running vertically. These will serve as the steering flaps.

Take the lollipop stick and cut two pieces, each 1 cm in length; these will be used to set the flaps to the correct height.

Cut two pieces of piano wire, measuring 38 cm and 14 cm in length respectively, and fold them into a U shape so that the top rod measures 9.5 cm. The longer piece will hold the two flaps spindles, and the shorter piece will serve as the flaps synchronizer.

Work on these U shapes until the rods are as straight as possible.

Add some duct tape to the front edge of the flaps to make them a bit more aerodynamic.

Using a piece of piano wire, pierce a hole on each side of the motor mount, in the last corrugated plastic channel (this step will be clearer in one of the next photos).

Insert the spindles into the 10th channels from the front of the flaps, add a small piece of lollipop stick, and push everything into the motor mount. Then, install the flap synchronizer into the last channel of both flaps.

To ensure the flaps synchronizer stays in place, thread a piece of synthetic string through the last channel of one flap and tie a knot around the synchronizer, positioning it 2 cm from the flap.

Secure the knot with super glue, and once the glue has dried, trim any excess string. It is not necessary to repeat this step on the other side.

Connect the flaps to the servo using two pieces of synthetic thread, each 25 cm in length.

To achieve a good balance between the angle of rotation and torque, thread the strings through the 4th hole from the center of the servo arm. However, other configurations might be more effective—refer to this video for insights on "control link geometry."

Drill two holes in each flap, just behind the spindles, at the height of the servo arm. Thread the strings through these holes and tie two very tight knots. Secure the knots with a bit of super glue and allow them to dry for a few hours, then trim any excess string.

The flaps are now complete. This is a side view of the left one.

You can see the spindle inserted in the last corrugated plastic channel of the motor support and the two holes where the threads are passed before being knotted.

Take the two corrugated plastic strips you cut earlier (35 cm long by 2.5 cm wide) and screw them under the hovercraft through the six previously drilled holes, using 2.5 cm long screws.

Ensure the strips are screwed precisely along the lines you drew at the beginning.

Cut a rectangle of wire mesh 38 cm in length by 18 cm in width, then fold it to achieve the shape shown in the picture: 16 cm in height at the back, a width of 5 cm, and 17 cm at the front. Fold this extra centimeter as illustrated in 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 (starting from 9 cm in height, cut 1 cm towards the center every 2 cm of height).

Using a corrugated plastic reinforcement, screw the front of the wire mesh into the two corrugated plastic strips below the hovercraft.

These two screws should be positioned approximately 14.5 cm from the rear of the hovercraft.

Use your smaller screws (2.5 cm in length) for this step.

The rear of the wire mesh can be attached to the "motor legs" using small cable ties.

Use a few pieces of duct tape to secure the bottom of the wire mesh to the bottom of the motor support—this step was not completed when the picture was taken, but it is absolutely necessary.

Then, verify that the wire mesh is firmly held in place.

Route the servo extension cable through the wire mesh, keeping it as far as possible from the propeller (visible on the left). Secure it with a bit of tape.

Complete the propeller protection with a corrugated plastic strip measuring 6.2 cm in width and 48 cm in length (with channels running lengthwise for better aesthetics). To shape it to the wire mesh, make the first fold 11.5 cm from one edge, another fold 5.5 cm further, then 13 cm further, and finally another 5.5 cm further. Secure this protection from below the hull with two screws on each side.

The center of gravity should be located not exactly in the middle of the hovercraft, but rather between 22 and 22.5 cm from the rear. Determine the optimal location for your battery to ensure the hovercraft is correctly balanced.

Once you have determined the battery's location, drill two holes to route the electric wires previously inserted in the hull channels. Mine are located 15 cm from the front.

It's time to handle the electronics. Here is a fast-made scheme. As you proceed with this step, ensure to use electrical tape or heat shrink tubes to insulate the soldered connections.

Build a small "box" to contain the battery, wires, and ESC, and screw it in place from underneath the hull. A cover will then be screwed on top of the box to protect the electronics from water.

This box — along with the battery inside — should be positioned so that the hovercraft's center of gravity is between 22 and 22.5 cm from the rear. My NiMH battery is positioned 11 cm from the front, but this may vary depending on the weight of your battery.

The result I achieved here is neither elegant nor practical — I can't connect or disconnect the battery without unscrewing the cover first. You can improve on this design by doing things differently, for example by adding a power switch.

Print this PDF file on A4 paper. Be sure to select "100% scaling", so the two opposite lines are spaced by 18.5cm. You can then transfer this shape onto a piece of cardboard.

Take a trash bag and cut it open so it lays completely flat. Use the cardboard template to cut out two skirt parts from the trash bag, following the measurements shown (25.1 cm at the top and 10.1 cm at the bottom). These parts will form the front and rear sections of the skirt.

The sides of the skirt have exactly the same corner shapes, but are longer: 50.1 cm at the top and 35.1 cm at the bottom.

Here are the four skirt panels. Now, you need to weld them together using a soldering iron.

Use a wooden workbench for this step. Take one short piece and one long piece of skirt. Place them on top of each other so that the corners align.

Position the cardboard template 1 mm before the corner. With your soldering iron, slowly follow the shape of the cardboard. The two skirt pieces will melt and fuse together.

Let it cool for about 20 seconds, then gently remove the skirt pieces, which will likely be stuck to both the workbench and the cardboard.

It's possible that your first attempt won't produce a perfect weld. If you notice any holes in the corner, make a second pass with your soldering iron. If that's still not enough, it's best to start over with new pieces of trash bag. You may also need to use a fresh soldering tip to ensure maximum heat.

In the same way, solder the four corners together to complete the skirt. Then turn it inside out, like a sock, so that the soldered seams are on the inside — for both strength and aesthetics.

The inner rectangle at the center of the skirt should measure 35 cm in length and 10 cm in width, while the outer rectangle should be 50 cm long and 25 cm wide.

You will now tape the skirt underneath the hull. It is crucial to take your time with this step — it may take up to an hour — to ensure everything is airtight and waterproof.

Remove the battery from its compartment and place the hovercraft upside down. If you followed the suggested dimensions for the wire mesh and the corrugated plastic protection, your hovercraft can also rest on either of its sides without damage. Choose the position that feels most comfortable for you.

In the picture, you are looking at the rear of the hovercraft, with the air deflector flap in the upper right corner. At the center, you can see two of the four screws that secure the corrugated plastic protection around the wire mesh.

Tape the outer rectangle of the skirt to the hull, edge to edge. Begin by taping two corners to stretch and secure one side of the skirt, then tape along the full length. Repeat the process for the remaining sides, always starting with the corners. This is arguably the most challenging part of the build — you'll be working in increasingly tighter spaces as more tape is added.

It is also possible to tape the skirt to the upper side of the hull, but since the tape will be visible from above, the overall finish will be less aesthetically pleasing.

Use double-sided tape to attach packing bubbles to the hull on both the right and left sides of the hovercraft.

You can skip this step if the hovercraft is intended to be used exclusively on dry land.

For this step, the ideal choice would be long, cylinder-shaped packing bubbles like the ones shown in the center of the picture.

You can then "close the skirt" by taping the right and left sides to the two corrugated plastic strips, edge to edge. Start by taping the ends to tighten the skirt, then add tape along the entire length of the strips.

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's possible that some water may enter the rear section of the skirt while operating on water. Drill three holes at the back of the skirt to allow any water that gets in to drain out.

You can skip this step if the hovercraft is intended for use on dry land only.

Turn everything on and set the throttle to maximum to check whether the skirt inflates evenly and whether the rear section of the skirt vibrates. If it does, remove the piece of tape and reposition a new one differently.

Also make sure the hovercraft appears well balanced — if it doesn't, your battery may be positioned slightly too far to the right or left.

Your Formula 3 is now complete — congratulations on your work building this RC hovercraft! Before operating it on open water, I recommend testing it first in a bathtub.

When not in use, store your Formula 3 with a small wedge placed under the motor mount to prevent long-term deformation of the hull.

The skirt is well suited for smooth surfaces like tiles or concrete. Be cautious with rougher surfaces such as asphalt, which can cause damage. Fortunately, the skirt can be replaced if needed.