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Old Dec 21, 2008, 05:59 AM
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NHC01 DIY depron hovercraft (build thread/CAD drawings)

Not sure how I missed the creation of the hovercraft forum, but I'm glad to see it's here. A while back I designed and built a hovercraft out of depron sheet (had some laying around), and never got around to posting it here on the forums, though the folks in the >>> Live Chat <<< have seen all this before.

From the start I wanted something that anyone could print out (patterns fit a standard 8.5"x11" print format), cut, and glue together in an evening or two. The choice of materials and equipment was based heavily on things I had lying around. The craft itself is sheets of 3mm and 6mm depron, but other materials can be substituted at/around the final part thicknesses.

The electronics/power system as built here consists of:
- 2x IPS sized motors with 3x2(lift) and 3x3(thrust) props
- 2x Castle Creations Pixie-7 ESCs
- 1x 2s1p 1300mAh lithium battery.
- 1x Berg 5ch (only 3 channels are used)
- 1x HS55 sized servo (don't know what this one is, label is long gone)
- 1x CSM HLG-200 gyroscope (optional)

Here's how it looks on the outside:


And some shots of the inside:



The CAD drawings are free for you to download, use, and modify. If you wish to redistribute drawings (in original or modified versions), I ask that you include a link back to this thread along with them. There are 4 primary parts to it, the bottom deck, the decks with holes, hollowed out upper deck spacers, and the bottom deck spacers. You will use multiple parts of each, except for the bottom deck. Here are the drawings with quantity and thickness used:

Bottom deck, 1x, 3mm:
http://nihil.rchomepage.com/hovercra...bottomdeck.dxf

Deck with hole, 2x, 3mm:
http://nihil.rchomepage.com/hovercra...1-deckhole.dxf

Upper deck spacers, 2x, 6mm (or 4x, 3mm):
http://nihil.rchomepage.com/hovercra...hollowdeck.dxf

Bottom deck spacers, 3x, 6mm (or 6x, 3mm):
http://nihil.rchomepage.com/hovercra...01-spacers.dxf

I used GraphiteOne CAD to create them, but they should open in pretty much any CAD program or drawing converter. There were some cross-CAD software issues when I initially had all the parts in one DXF file, but with them split up as they are above, there have been no complaints so far.

The next several posts will be the build process. You will see some parts used that aren't included in the CAD drawings (rudder, skirt retainer), and that holes have been re-sized, etc.. This is due to the fact that I was making it up as I went along. I hope you enjoy the thread.
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Old Dec 21, 2008, 06:25 AM
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First things first, print out the plans, trace them to your choice of material (depron used here), and start cutting out the parts. I didn't take the greatest of pictures as I went along, but it should be easy enough to follow.

Pile of parts in the process of being cut out:


Starting a dry fit with temporary bottom deck spacers:


Middle deck added:


Hollow upper deck spacers:


And the upper deck to top it off (notice the depron dust from sanding the inner circumference of the hole smooth):
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Old Dec 21, 2008, 06:42 AM
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Now we start gluing things together and introduce a new part, the duct lining, which may or may not be necessary depending on which side of the line you cut the hole on, how much you sanded, and the diameter of the chosen lift prop. I used a strip of 3mm depron 20mm wide, and long enough to make it all the way around the hole (cut it longer then trim to fit). Plain Elmers white glue is used throughout the construction.

Middle deck and upper deck spacers with duct lining:


The process I used to install the lift fan isn't covered very well in the pictures, so I'll try to explain. The mount is a simple strip of wood from a cigar box, about 2-3mm thick, 10mm wide, and 150mm long or so. There are two small CF rods glued to it in the middle to cradle the IPS motor, with two holes drilled on the outside of that to accommodate the zip tie holding the motor in place. It is best to build this as a whole assembly, with motor and prop attached -before- cutting the notches it fits into. That way you can use the prop to center the motor in the hole, trace around the mount ends, and cut the notch there. After you have your notch, slide the mount in place and give the prop a spin or two to make sure it clears all the edges and is relatively centered. If all is good, pull the mount, cover the ends in glue, then slide it back in place and wait for it to dry.

Here are some shots of the lift fan installed:

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Old Dec 21, 2008, 06:51 AM
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Next up we have the bottom deck with spacers. These are slightly different than the ones in the CAD drawings, and here is the placement:


Adding the middle deck assembly to the bottom deck and bottom deck spacers:


Upper deck for fit (DO NOT GLUE THIS PART):


Add some weight over the surface and allow to dry:
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Old Dec 21, 2008, 07:04 AM
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Now it's time to figure out the skirt. First up is a series of test skirts I used to get a feel for how well the little IPS drive was going to provide lift. First thing I did was attach a long'ish tube of garbage bag material:

http://nihil.rchomepage.com/hovercra...2/dscn1493.mov

Then I trimmed it to about this size:


And had another run:

http://nihil.rchomepage.com/hovercra...2/dscn1497.mov

Not horrible for a first go, so lets tuck the ends in and attach them to some more depron (retainer not in CAD plans).

Lots of marking:




Attach it to a depron ring with lots of clear tape:


That one worked OK, but I wanted to experiment a bit further, and cut up some pool noodle to use as a rigid skirt:



A quick test hover:
http://nihil.rchomepage.com/hovercra...3/dscn1518.mov

That was great for very flat and smooth surfaces, but I wanted to play outside.
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Old Dec 21, 2008, 07:24 AM
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Here we come to the skirt that is currently on it. It's great on flatter surfaces, and it also works fine on the very rough road out front with lots of small pebbles and twigs. Dirt and water are also fine, but grass is not going to happen, it just too small a footprint. There are better skirts done in a "finger" type fashion, but I haven't mastered those yet.

Using the rigid pool noodle skirt as a template I cut out some more garbage bag pieces:




Before we assemble those pieces, a little bit about the "welding" process I used. I found that if you heat up a curved length of metal wire, you can use it to both cut and seal two pieces of plastic sheet in one motion.

A pair of pliers holding the metal wire, rubber band used to hold the pliers shut:


One swipe down the right hand side:


The pieces split at the center of the weld:


And seal to each other:


Adding some tension to test the strength:


Cups full of change wouldn't hold it, so I taped it to the bench:


It finally starts to tear:


I found that the gauge of the wire you use to cut with should be matched to the material you are cutting, as the sides of the wire do the sealing while the center (part that makes contact) does the cutting. 3mm bicycle spoke works great for garbage bag thickness material.

Happy with the results, let's build the skirt:




After attaching it to the craft in the same manner as before, I did another test hover:
http://nihil.rchomepage.com/hovercra...4/dscn1536.mov
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Old Dec 21, 2008, 07:56 AM
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I got rather lazy towards the end with the picture taking, so here it is with the thrust fan installed, the rudder, and radio gear:


The thrust fan tower is made of a stack of 6mm depron, glued together then shaved and sanded into a pleasing shape. There are two glue coated CF rods that run the full height of the tower, and protrude below the bottom deck where they were further secured with a blob of glue and scrap of CF sheet. The motor was then strapped to the top of the tower with packing tape.

The rudder is just a bit of 3mm depron sheet with a CF rod attached to one side. That CF rod sits in a bushing made of CF tube that is pushed and glued into the body of the craft. There is a servo horn at the bottom of the rudder that is secured to both the CF rod and the rudder surface with CA and tape.

The upper deck is secured by way of velcro strips positioned around the edges of the craft. holes were poked and notches cut to run the various wires where they needed to go, the battery mounts in the center between the lift fan and the thrust fan tower.

The first controlled scoots around the house:
http://nihil.rchomepage.com/hovercra...5/dscn1540.mov
http://nihil.rchomepage.com/hovercra...5/dscn1541.mov


Some things to note:
- The large hole towards the rear of the bottom deck needs to be enlarged from the size in the CAD drawings. I found that extending the hole all the way forward to the edge of the lift fan duct was the sweet spot for this setup.

- Addition of a gyro on the rudder makes it so much easier to drive, particularly when lining up to ramps in cramped indoor conditions.

- Minivans have low ground clearance, so keep that in mind when you jump the lip into the neighbors driveway.

- Activity over water should be limited. While it handles calm water just fine, if it gets stuck without lift I'm sure it would start falling apart given the tape and water soluble glue construction.

- Sharp turning at high speed in gusty conditions can result in the craft flipping over (it's faster than I thought it would be).

- Garbage bag skirts need to be patched/replaced periodically when used on coarse surfaces (gravel, old rock and asphalt roads, sticks, etc..). I have some ripstop nylon I had planned to use, but it's being saved for the next hovercraft (much larger, two Axi 2212/26, 10" lift fan, variable pitch thrust fan courtesy of an Eco8 tail, horizontal trim surface with its own gyro).


Well that's about it. Hope you enjoyed it. Feel free to chime in with any questions/comments.
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Old Dec 21, 2008, 08:47 AM
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wow! well done nihil! it looks to drive very well and i like the construction method
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Old Jan 09, 2009, 08:08 PM
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Wow, I should have checked this sight out before I made my hovercraft... could have save a lot of time and money. Great design BTW, I have a friend that wants to make one this should be a good start.
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Old Jan 09, 2009, 11:43 PM
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Thanks guys, I'm glad you like it. I hope to see more of these scooting around. Given how easy and cheap they are to build, hovercraft are the best bang for the buck in R/C if you ask me.


Xmod: Tell your friend I'll be more than happy to answer any questions if he wants to build one of these. That goes for anyone else too. The thread wasn't as thorough as it could have been, but it's not rocket science. The only hard part is making the first skirt, after that it's not bad.

For example, here is a single fan hovercraft I built out of micro heli parts and the postal box they came in. I wrecked the heli before they showed up and had a pile of parts sitting there doing nothing, and this is what came of it (apologies for the poor quality pictures, circa before I joined RCG):







The fan is an EDF40(or was it a 50?) that was going to be the tail on a Piccolo. The body, rudder, and fan shroud/strap are all made of the cardboard postal box the parts came in, the skirt is the bubble wrap (popped) they were wrapped in. Probably the same rudder servo as the depron HC above, 2s1p 1200mAh lipo, one of the same Pixie-7 ESCs as the depron craft above, and some random small rx that was laying around.
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Old Dec 10, 2009, 02:19 PM
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My First Hovercraft !

Hello, I came across this thread while googling information on DIY rc hovercrafts. First of I'd like to say your hovercraft looks really good !

I've decided to build my own RC hovercraft for a physics end of year project. I'm of course not allowed to just build a kit, I have to design and build it myself, finding out which materials work best and so on.

However I've never built a RC craft before and I was hoping that someone here could maybe give me an idea as what's the best place to start.

My main problem would be the electrical parts needed how their used. I can figure out the basics for example I need a lift and thrust motor with props, a radio controller with receiver, but what else ? Is there maybe a site where I can find information on such things ?

Any help would really be appreciated.
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Old Dec 10, 2009, 10:13 PM
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First off, welcome to RCGroups. You should be able to find all the information you need here.

In addition to the transmitter, receiver, lift motor, thrust motor, and props for each, you will need two speed controllers, commonly referred to as ESCs (Electronic Speed Controllers). These sit between the receiver and the motors, and as the name implies, control the speed at which the motors turn. You will also need a servo to control the rudder. Servos, like ESCs, take signals from the receiver and convert them into electromechanical motion. Where the speed controller tells a motor how fast to spin, the servo adds a set of gears, an arm, and internal feedback to provide linear motion.

Optional equipment would include a gyroscope, which can be used on the rudder channel/servo to make driving in a straight line much easier and more precise.

If you have any other questions feel free to ask.
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Old Dec 11, 2009, 11:47 AM
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Thank you for your quick response, very much appreciated.

Well I still have loads of questions about RC gear and hovercrafts, but first things first.

I made a hoover powered test thing at home. The design was very primitive basically just a square wooden plank with a hole in the middle. I made the skirt out of a plastic sail, which I then attached to the sides of the plank and attached the middle of sail to the plank using a jam pot lid. After that I cut four small holes in the middle to let the air through.

The design worked oke, but I was wondering how you made your skirt ? Could you maybe post a picture of the bottom of your hovercraft ?
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Old Dec 12, 2009, 04:11 AM
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I made my skirt the same way described in posts 5 and 6 in this thread. Making the first one is difficult, but after you get your head around it cranking out new skirts is easy enough. The key is that when the skirt is inflated, all the edges make contact with the ground evenly (like the rigid skirt made from pool noodle above). That way the air that escapes from the bottom does so evenly around the edges of the craft, giving you a nice solid footprint.

Here is a picture of the bottom:


And here is one of the top with the wiring color coded and the servo/rudder mechanism explained:


The transmitter signal comes in on the blue wire (antenna) into the receiver, where the receiver decodes it and send out signals on different channels (green wires). Two of those channels go to the ESCs and feed power to the lift and thrust fans via the purple wires. The other green wire/channel is used for steering, and in this case it goes through a gyro (black blob to the right of the thrust fan tower), then on to the servo. The servo and rudder movements are highlighted in orange. The large silver and black rectangle in the middle is the battery, and connects to the ESCs directly, which then feed power to the receiver and servo over two of the wires in the green bundles (three (green) wires for each ESC and servo/gyro, ground, +5V, and signal).
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Old Dec 13, 2009, 03:32 PM
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Well once again thank you very much for what you've done !

I've made a model using cardboard, just get the hang of the body and making the skirt, which is proving to be a challenge. Melting the black bag pieces together isn't going all too smooth yet, but I'm starting to get the hang of it

I'm planning to buy the electrical parts from hobby king. If made a part list, would maybe if had the time be able to just look it over to see that I'm getting the right parts that go together ?
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