NHC01 DIY depron hovercraft (build thread/CAD drawings)

[nihil]

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 RCGroups Chat (http://www.rcgroups.com/forums/chat.php) 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:
http://nihil.rchomepage.com/hovercraft/nhc01/build05/itruns1539.jpg

And some shots of the inside:
http://nihil.rchomepage.com/hovercraft/nhc01/cad/hcbottom-sm.png
http://nihil.rchomepage.com/hovercraft/nhc01/cad/hcupperdeck-sm.png

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/hovercraft/nhc01/cad/nhc01-bottomdeck.dxf

Deck with hole, 2x, 3mm:
http://nihil.rchomepage.com/hovercraft/nhc01/cad/nhc01-deckhole.dxf

Upper deck spacers, 2x, 6mm (or 4x, 3mm):
http://nihil.rchomepage.com/hovercraft/nhc01/cad/nhc01-hollowdeck.dxf

Bottom deck spacers, 3x, 6mm (or 6x, 3mm):
http://nihil.rchomepage.com/hovercraft/nhc01/cad/nhc01-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.

[nihil]

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:
http://nihil.rchomepage.com/hovercraft/nhc01/build00/hovercraft1460.jpg

Starting a dry fit with temporary bottom deck spacers:
http://nihil.rchomepage.com/hovercraft/nhc01/build00/hovercraft1461.jpg

Middle deck added:
http://nihil.rchomepage.com/hovercraft/nhc01/build00/hovercraft1462.jpg

Hollow upper deck spacers:
http://nihil.rchomepage.com/hovercraft/nhc01/build00/hovercraft1463.jpg

And the upper deck to top it off (notice the depron dust from sanding the inner circumference of the hole smooth):
http://nihil.rchomepage.com/hovercraft/nhc01/build00/hovercraft1464.jpg

[nihil]

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:
http://nihil.rchomepage.com/hovercraft/nhc01/build01/hovercraft1482.jpg

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:
http://nihil.rchomepage.com/hovercraft/nhc01/build01/hovercraft1483.jpg
http://nihil.rchomepage.com/hovercraft/nhc01/build01/hovercraft1484.jpg

[nihil]

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:
http://nihil.rchomepage.com/hovercraft/nhc01/build01/hovercraft1486.jpg

Adding the middle deck assembly to the bottom deck and bottom deck spacers:
http://nihil.rchomepage.com/hovercraft/nhc01/build01/hovercraft1487.jpg

Upper deck for fit (DO NOT GLUE THIS PART):
http://nihil.rchomepage.com/hovercraft/nhc01/build01/hovercraft1488.jpg

Add some weight over the surface and allow to dry:
http://nihil.rchomepage.com/hovercraft/nhc01/build01/hovercraft1490.jpg

[nihil]

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/hovercraft/nhc01/build02/dscn1493.mov

Then I trimmed it to about this size:
http://nihil.rchomepage.com/hovercraft/nhc01/build02/newskirt1501.jpg

And had another run:

http://nihil.rchomepage.com/hovercraft/nhc01/build02/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:
http://nihil.rchomepage.com/hovercraft/nhc01/build02/newskirt1504.jpg
http://nihil.rchomepage.com/hovercraft/nhc01/build02/newskirt1505.jpg
http://nihil.rchomepage.com/hovercraft/nhc01/build02/newskirt1506.jpg

Attach it to a depron ring with lots of clear tape:
http://nihil.rchomepage.com/hovercraft/nhc01/build02/newskirt1510.jpg

That one worked OK, but I wanted to experiment a bit further, and cut up some pool noodle to use as a rigid skirt:
http://nihil.rchomepage.com/hovercraft/nhc01/build03/rigidskirt1517.jpg
http://nihil.rchomepage.com/hovercraft/nhc01/build03/rigidskirt1516.jpg

A quick test hover:
http://nihil.rchomepage.com/hovercraft/nhc01/build03/dscn1518.mov

That was great for very flat and smooth surfaces, but I wanted to play outside.

[nihil]

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:
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1520.jpg
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1521.jpg
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1522.jpg

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:
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1523.jpg

One swipe down the right hand side:
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1524.jpg

The pieces split at the center of the weld:
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1525.jpg

And seal to each other:
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1526.jpg

Adding some tension to test the strength:
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1527.jpg

Cups full of change wouldn't hold it, so I taped it to the bench:
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1528.jpg

It finally starts to tear:
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1529.jpg

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:
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1530.jpg
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1532.jpg
http://nihil.rchomepage.com/hovercraft/nhc01/build04/plasticskirt1534.jpg

After attaching it to the craft in the same manner as before, I did another test hover:
http://nihil.rchomepage.com/hovercraft/nhc01/build04/dscn1536.mov

[nihil]

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:
http://nihil.rchomepage.com/hovercraft/nhc01/build05/itruns1538.jpg

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/hovercraft/nhc01/build05/dscn1540.mov
http://nihil.rchomepage.com/hovercraft/nhc01/build05/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.

[bigbadbob2003]

wow! well done nihil! it looks to drive very well and i like the construction method

[Xmodgeek]

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.

[nihil]

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):

http://nihil.rchomepage.com/hovercraft/postboxhc/eelcart.jpg
http://nihil.rchomepage.com/hovercraft/postboxhc/hc-backleft.jpg
http://nihil.rchomepage.com/hovercraft/postboxhc/hc-backright.jpg
http://nihil.rchomepage.com/hovercraft/postboxhc/hc-bottom.jpg
http://nihil.rchomepage.com/hovercraft/postboxhc/hc-zoom.jpg

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.