Coandă Effect Makes A Better Hovercraft Than A Quadcopter

Leaving no stone unturned in his quest for alternative and improbable ways to generate lift, [Tom Stanton] has come up with some interesting aircraft over the years. But this time he isn’t exactly flying, with this unusual Coandă effect hovercraft.

If you’re not familiar with the Coandă effect, neither were we until [Tom] tried to harness it for a quadcopter. The idea is that air moving at high speed across a curved surface will tend to follow it, meaning that lift can be generated. [Tom]’s original Coandă-copter was a bit of a bust – yes, there was lift, but it wasn’t much and wasn’t easy to control. He did notice that there was a strong ground effect, though, and that led him to design the hovercraft. Traditional hovercraft use fans to pressurize a plenum under the craft, lifting it on a low-friction cushion of air. The Coandă hovercraft uses the airflow over the curved hull to generate lift, which it does surprisingly well. The hovercraft proved to be pretty peppy once [Tom] got the hang of controlling it, although it seemed prone to lifting off as it maneuvered over bumps in his backyard. We wonder if a control algorithm could be devised to reduce the throttle if an accelerometer detects lift-off; that might make keeping the craft on the ground a bit easier.

As always, we appreciate [Tom]’s builds as well as his high-quality presentation. But if oddball quadcopters or hovercraft aren’t quite your thing, you can always put the Coandă effect to use levitating screwdrivers and the like.

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A Garbage Bag Skirt Is Fit For A Hovercraft

The hovercraft is an entertaining but much maligned form of transport. While they have military applications and at times have even run as ferries across the English Channel, fundamental issues with steering and braking have prevented us all driving them to work on a regular basis. They do make great toys however, and [HowToMechatronics] has built an excellent example.

The build is primarily a 3D printed affair, with the hull, ducting, and even the propellers being made in this way. The craft is sized to be readily printable on a 30cm square build platform, making it accessible to most printer owners. Drive is via brushless motors, and control is achieved using their previously-featured self-built NRF24L01 radio control transmitter.

What stands out among most other hovercraft builds we see here is the functioning skirt. It’s constructed from a garbage bag, and held on to the hull with a 3D printed clamping ring. Most quick builds omit a skirt and make up for it with light weight and high power, so its nice to see one implemented here. We’d love to see how well the craft works on the water, though it holds up well on the concrete.

Finished in a camouflage paint scheme, the craft looks the part, and handles well too. We’d consider a small correction to the center of gravity, but it’s nothing a little ballast wouldn’t fix. Video after the break. Continue reading “A Garbage Bag Skirt Is Fit For A Hovercraft”

Single Motor, Single Piece 3D Printed Hovercraft

RC hovercrafts offer all sorts of design options which make them interesting projects to explore. There are dual-motor ones where one motor provides lift while the other does the thrust. For steering, the thrust motor can swivel or you can place a rudder behind it. And there are single-motor ones where one motor does all the work. In that case, the airflow from the motor blades has to be redirected to under the hovercraft somehow, while also being vectored out the back and steered.

[Tom Stanton] decided to make a single-motor hovercraft using only a single 3D printed piece for the main structure. His goals were to keep it as simple as possible, lightweight, and inexpensive. Some of the air from the blades is directed via ducting printed into the structure to the underside while the remainder flows backward past a steering rudder. He even managed to share a bolt between the rudder’s servo and the motor mount. Another goal was to need no support structure for the printing, though he did get some stringing which he cleaned up easily by blasting them with a heat gun.

From initial testing, he found that it didn’t steer well. He suspected the rudder wasn’t redirecting the air to enough of a sideways angle. The solution he came up with was pretty ingenious, switching to a wedge-shaped rudder. In the video below he gives a the side-by-side comparison of the two rudders which shows a huge difference in the angle at which the air should be redirected, and further testing proved that it now steered great.

Another issue he attacks in the video below was a tendency for the hovercraft to dip to one side. He solves this with some iterative changes to the skirt, but we’ll leave it to you to watch the video for the details. The ease of assembly and the figure-eight drift course he demonstrates at the end shows that he succeeded wonderfully with his design goals.

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Hovercraft Of The Future

We think of hovercraft as a modern conveyance. After all, any vision of the future usually includes hovercraft or flying cars along with all the other things we imagine in the future. So when do you think the hovercraft first appeared? The 1960s? The 1950s? Maybe it was a World War II development from the 1940s? Turns out, a human-powered hovercraft was dreamed up (but not built) in 1716 by [Emanuel Swedenborg]. You can see a sketch from his notebook below. OK, that’s not fair, though. Imagining it and building one are two different things.

[Swedenborg] realized a human couldn’t keep up the work to put his craft on an air cushion for any length of time. Throughout the 1800s, though, engineers kept thinking about the problem. Around 1870, [Sir John Thornycroft] built several test models of ship’s hulls that could trap air to reduce drag — an idea called air lubrication, that had been kicked around since 1865. However, with no practical internal combustion engine to power it, [Thornycroft’s] patents didn’t come to much. In America, around 1876 [John Ward] proposed a lightweight platform using rotary fans for lift but used wheels to get forward motion. Others built on the idea, but they still lacked the engines to make it completely practical.

But even 1940 is way too late for a working hovercraft. [Dagobert Müller] managed that in 1915. With five engines, the craft was like a wing that generated lift in motion. It was a warship with weapons and a top speed of around 32 knots, although it never saw actual combat. Because of its physical limitations it could only operate over water, unlike more modern craft.

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3D Printed Hovercraft Takes Flight

Last time we checked in on [Ivan Miranda] he was putting a drill press on the Internet. Lately, he has been trying to 3D print a hovercraft with some success. He made four attempts before arriving at one that works fairly well, as you can see in the video below. We will warn you, though, the screwdriver cam is a bit disconcerting and we suggest waiting at least an hour after you eat to watch.

The starboard impeller broke midway through the test, although with a single impeller it was working pretty well. [Ivan] thinks he can print the impeller frames more strongly to prevent future failures. The design is in Fusion360 and there is enough detail that you can probably duplicate his work if you have the urge. There’s a mount for a headlight and an action camera on the bow.

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3D Printed Hovercraft Takes To The Air

Instructables user [John_Hagy] and some classmates built an RC hovercraft as their final project in the Robotics Education Lab at NC State University. It’s a foam slab with a Hovership H2204X 2300Kv brushless motor inflating a skirt made out of ripstop nylon. Nylon is great here because it has a low friction coefficient and is nonporous to keep the air in. A second motor propels the craft, with a servo turning the whole motor assembly to steer. The team designed and 3D-printed fan holders which also help channel the air to where it’s supposed to go. Control is via a typical radio-control transmitter and receiver combo.

The project writeup includes a lot of fun detail like previous versions of the hovercraft as well as the research they undertook to learn how to configure the craft — clearly it’s their final paper put on the internet, and well done guys.

Needless to say, we at Hackaday can’t get enough of this sort of thing, as evidenced by this cool-looking hovercraft, this hovercraft made on a budget and this solar-powered ‘craft.

Retrotechtacular: Fantastic Backyard Inventions Of Yore

News corporation [British Pathé] created many newsreels and documentaries throughout their 60-year history. Recently, the company released scores of films from their archives and put them on the internet. Here is a delightful collection of short films they created that highlight strange and wonderful inventions in various fields, including transportation and communication.

One of the standout inventions is the Dynasphere, a mono-wheeled vehicle that probably deserves its own week in the Retrotechtacular spotlight. There are a couple of pedal-powered planes that may have inspired the Gossamer Condor, and a hover scooter that resembles an air hockey striker and doubles as a leaf blower. In another film, a man drives a Vespa to the banks of the Thames and parks it. He pulls a fin down from each side of the scooter, turning it into a seafaring craft. When he snaps his fingers, a cute girl appears from somewhere just outside the frame. She climbs on the back, and they take off across the water.

The average running time of these films is about two minutes. Some of them are much shorter, prompting many questions. Fortunately, most of the video descriptions have links with more information about these marvelous inventions. Almost all of the inventors in these films show a complete disregard for safety, but nearly everyone involved seems to be having the time of their lives.

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