Thrust Vectoring Ground Effect Vehicle - Project!

In this project, James takes on the challenge of building an RC ground effect vehicle - here’s how that went.

By the way, if you don’t know much about ground effect, you can read this article on how ground effect vehicles work. You’re welcome!

Conceptualizing the Concept

Before jumping in head-first to a project all themed around ground effect vehicles, I thought it might be a sensible idea to actually think about what the project should actually be. For this, I wrote some rules before diving into sketching a design.

The ground effect vehicle must:

Be able to hover across a flat surface under its own propulsion
Have lifting wings or surfaces that create the ground effect
Include some interesting features worthy of a juicy article

Choosing a configuration

Like with airplanes, ground effect vehicles come in different shapes, sizes and flavours. There isn’t really a standard configuration, more so three standard configurations. Without making you reference the ‘How Ground Effect Vehicles Work” article again, here’s a summary of these:

Ekranoplan

This configuration was used by the famous ‘Caspian Sea Monster’ that terrorised the Caspian Sea back in the later 20th century. The Soviet Union build some behemoth ground effect vehicles which were the largest ever.

Lippisch

Alexander Lippisch, a man responsible for all sorts of pioneering aviation designs, came up with this configuration for a ground effect vehicle. It traps air under its wing and uses a large tail out of ground effect for stability.

Double Wing

The double wing uses airfoil-shaped wings on the top and bottom to skim across the ground or a surface of water on a cushion of air. It usually has wing skirts to trap the air and prevent it from spilling outwards.

After some sketching, I decided that the configuration which would most likely give me some success would be the Ekranoplan ground effect vehicle. It would also be relatively easy to manufacturer and could end up looking a little like that beast, the Sea Monster.

Materials and Electronics

If you want to build your own ground effect vehicle, here’s what this one used:

4-5 sheets of Flite Test Foam
Plywood
1x Aluminum spar
Lots of hot glue
2x Power Pack F motors and speed controllers
1x FMS 70mm EDF unit
1x 60A speed controller with built in UBEC
4x Flite Test 9g Servos
A Spektrum 6 channel receiver
2x 4s batteries (between 1000mAh and 3000mAh)

Building It

As planned, the build was fairly straightforward. No CAD software needed to be use and everything was taken from sketches and enlarged to paper templates to cut out each component. You can learn how to design planes like this here.

I started with the fuselage as it was just a simple box.

The front end was shaped into an aerodynamic wedge with a broad steep underside. This was to get more lift from the body itself whilst ensuring that later it could rise up out of water.

The tail was a little more complex as it had to be designed to lift and support the huge rear wing. I decided to go with a twin tail type design which essentially created a hollow box.

The rear wing was made with an airfoil to create lift. This meant that the center of gravity could, theoretically, be rear of the main wing as both working together moves the center of lift somewhere in-between the two surfaces.

Atop the rear wing was mounted an FMS 70mm EDF unit. This was the main motor. Static thrust from electric ducted fans, however, isn’t great so some extra motors were needed.

At the front, I added a pivoting thrust vectoring mechanism equipped with two quad motors and props. This tilts up when needed to provide a downward thrust angle when needed. Later I found that this really helps to control the pitch whilst offering plenty of static thrust to get the vehicle moving.

The main wing is comprised of two sheets of foam, has an aluminum spar and is about 100cm wide. This is far shorter than the overall length of the aircraft but still provides ample surface thanks to its expansive wing chord.

The to work the control surfaces, I used standard Flite Test 9g servos. The tilt mechanism used a far larger metal gear servo mounted to a 3D printed base.

With a few finishing touches, it was go time!

Testing It

One clear calm afternoon on a wintry December day, I decided to take advantage of the lack of rain and test the newly completed Ekranoplan for the first time.

The two batteries I was using were a 2200 4s for the front props and a 1000 4s for the EDF. I was a little concerned about wight so decided to try and go quite minimalist for the initial tests.

The first run showed the aircraft had enough power to get going, but it wasn’t clear whether it would fly.

Time for more power. Wait for it...

Nothing. Something was wrong.

It turned out that one of the front motors was refusing to rotate. Well, that’s a little annoying.

Modifications

Over the course of around four to five hours that evening, I stripped the 3D printed tilt mechanism to its component parts and tried to diagnose the issue with the motor.

It turned out the motor had burned out. Tell tail black coils on the inside made it clear. Changing them wasn’t too easy as I decided to also replace the aluminum spar that held them; in a previous life, the mechanism had been attached to a plane that was involved in a crash which bent the arm. Over time, it simply wouldn’t hold up, so best be on the safe side and replace it.

The wiring was pulled out and re-soldered.

Testing It Again

Once again, I trekked into the cold to see whether the Ekranoplan could get itself into ground effect. The first go proved that it could at least power forward and leap into the air, hooray!

The second showed that a cushion of air was being formed under the main wing. Some wing fences should help to trap the air even more.

Generally, it was lots of fun piloting the thing about the ground. Imagine how fun this would be in the snow! I’ll have to wait a while for that.

Going Forward

There are several mods needed to get this thing flying optimally. Let’s go through the problems and solutions

1) CG

As mentioned earlier in this article, I theorised that the centre of gravity could be placed further aft than on a conventional aircraft due to it having two wings, one in ground effect and one also acting as a stabiliser at the rear. However, what I didn’t realise is that the ground effect on the main wing would provide far more lift than the tail. For this reason, the CG actually needs to be over this surface as it is the centre of lift. Next time, larger batteries will be placed in the nose.

2) Wing Fences

To capture more of the air, wing fences will be added to the ends of the main wing. These will also act as floats and, therefore, be large foam blocks with streamlined undersides. Hopefully, the power setup should have no problems raising them out the water/snow.

3) Waterproofing

All of the electronics will be fully waterproofed to survive an onslaught of spray and general wetness. Check out this video to learn how to waterproof your own electronics.