You know how, during touch-down, planes hover a few feet above the ground for a while before their wheels actually hit the runway?

This is not only to give the passengers a smooth landing but it is also the natural result of ground effect, in which there is increased lift on the wings in proximity to the ground, caused mainly by the compression of air under them as it is squished to the ground.

Anyways, the actual science behind this awesome phenomenon does not need to be known to make a incredibly fast, efficient vehicle. The Russians understood this when they created the Ekranoplan a while back in the hopes of utilizing it as a quick way to transport troops. However, the project never became widespread due several problems, the main one being it only worked on large, flat areas of land.

Thankfully though, RC vehicles are small, and so any court / field will do. Still, it should be noted that bigger is better, as these things are fast, and without an airbrake, they can go flying into walls slightest lost of control.

With that in mind. Lets get right into the build.

Supplies

Materials:

foam board (between 4mm and 10mm)
reinforced tape (duct tape)
velcro strips
toothpicks (x20)
hot glue sticks
bolts / nuts (between M3 and M5)
wire (clothes hanger)
plastic sheet

Electronics:
motor (2300 KV)
ESC (10 A)
battery (3s 2200 mAh)
servo (9g)
propeller (5 in)

Tools:

hot glue gun
pliers
drill
3D printer

Step 1: Building

The design does not have to be exact, as it should vary between the electronics you use. However, the dimensions of mine are:

base - 10.5 in * 14 in
wings - 4 in * 6 in
tail - 5 in * 7 in

Note that:

the tail should be big, as you do not want it to skid out at high speeds
skids go all the way from the front the base to the back and should be taller at the front

Throughout the testing and rebuilding of many prototypes, I found several useful techniques listed here:

using toothpicks to stabilize the joints - stab them in once the hot glue has set and cut off the excess
supporting the corners - put lots of glue so that if the craft crashes there will be less damage

Step 2: Protecting

This step should only be done if you want to use your ground effect vehicle more than once. That said, to protect my ground effect vehicle I did several things:

putting plastic on the skids - keep them from getting ripped up on the pavement and prevent friction
putting plastic / tape on the corner + tips of the wings - prevent major damage and allows for some pretty cool looking wing slides as it turns

It should also be noted that I used an old 3D printing mat as the "plastic". It held up against the friction and heat really well, and it has a sticky back as well as a slippery front.

Step 3: Detailing

This is the last step before the electronics, so we should probably add a motor mount if we want this thing to work. I started off first by cutting up several wooden 1/2 in by 1/2 in wooden sticks, and glueing them together in a form that would support the motor. However, this design was quite weak, and so, I adopted a completely 3D printed form (linked below). This, in combination with two bolts passing through the foam board, allowed for some much stability and crash-resistance.

If you want to make the motor mount yourself, it should be:

low, the higher up the propeller is the more likely it is to tip forward and face-plant
more than just glued on, perhaps add toothpicks again, or like I did, add bolts

Another thing to be added, is the control horn on the tail of the vehicle. I 3D printed mine, but most servos come with their own. Also, the closer you put it to the hinge, the more rotational range you will get.

Finally, a very stable way to hold the battery is to cut a series of slits in the foam. Through these, you can pass velcro strips and securely hold the battery in place. I cut many of them so that I could shift the battery around, and thus change the center of gravity. Also, I added packing tape on top the foam where the slits are to that it will not rip with a large impact.

Ground Effect Mount.stl
Download View in 3D

Step 4: Electronics

For those of you that do not know, RC (remote control) electronics are really simple, especially for this build. Just by attaching the parts following the diagram above, you are already basically done. A few tips I have are:

put the throttle (motor) to channel 3 and steering (servo) to channel 1, that way you can use both sticks
center the servo before glueing it down to the foam board, so that you will not have to do massive trimming in the transmitter settings
trim/offset the rudder to be slightly pushing against the direction of the motor, as the torque from the motor tends to make the vehicle turn a bit
make the control rod out of an old, metal clothes hanger, it is quite strong and will not offer much play in the system

Step 5: Finishing

That is it. You are done. Congratulations. I hope your ground effect vehicle works as good as mine did, and I push you to beat my time of 50 meters in 6.5 seconds. Thank you very much for reading. Goodbye.