1/3RD SCALE HOVERCRAFT
RADIO CONTROLLED / GASOLENE POWERED / SCRATCH BUILT
Here is my build log on how I built my hovercraft. This project has been a life long childhood dream to build a hovercraft. It came out a little bigger than I imagined, but hey, this is BBMP after all. What sparked the whole project to go ahead was finding a free engine at a small engine repair shop. I got it running and thought what I could build for it. Also another reason for building it was that the fact I was a job that gave me 3 day weekends. So I figured I had the time to do such a project. Of coarse, the job eventually turned into a 1 day off a week routine and eventualy a 24 day on and 4 day off routine at the end, so hence why it took me a full year exactly to finish the beast.
Initial gathering of parts.
I needed a 2nd engine, and Princess Auto had a sale on these Weed Eater engines.
This is what sparked the whole idea of building a hovercraft, thie engine. I got it for free from a small engine repair shop here in Edmonton. Was bored one day and decided to see if these shops had blown engines that I could rebuild, turns out all this needed was a spark plug and fuel line plugged back in!
This if the skirt fabric. I got it from a fabric store near by the small engine repair shop (ironicaly). Its a nylon waterproof fabric, at about 8oz/sqin. I also picked up nylon thread.
Here are both engines taken apart and "lightened" as best as I can. I was originally going to use the leaf blower impeller, but decided not to use it. Will explain it in the next few photos.
The Ryobi 31cc taken apart. Before I machined the flywheel down.
The Ryobi 31cc engine on a test stand. Hard to build a hovercaft around a engine that "might" work.
The begining of the hull. Glueing some spruce around the edge. this is orientated (upsidedown)
I used pvc cutouts as clamps, got this idea from the kayak/canoe boat shop where I got my fiberglass supplies from.
Both engines back together with backplate brackets attached. The Leafblower engine on the left has a 1999 VW Golf fan blade attached. It bolted onto the shaft with very little mods, and spins true. The Ryobi engine on the right has a regular puller prop on from running it on the test stand as it seemed to be overheating.
The bottom of the haul gets ribs and more bracing
And another angle.
Engines placed onto the haul to figure out where to mount them exactly
And another angle, the hole for the lift engine will obviously be reamed out a bit more.
More glueing and bracing. I built this thing to stand on, and take a beating. Which at the end was a little overkill.
More glueing and bracing.
How I made the mould for the cowling.
And how I got them all perfectly smooth together, by spinning it with the drill and holding up my sanding bar to it.
Finished the mold, and placed on the haul to show its size.
Upper engine pod being constructed.
Under the haul, you can see I used blind nuts to keep the engine pod in place.
Some outside shots.
Another outside shot. I had to trim the 16" pusher blade back a bit to fit into the cowl better.
This is vernier from Home Depot, to be used as my foundation for the cowling, just clamped together and staged to see if there will be any problems.
Another angle, and more panels glued to the engine pod.
The cowl is done, used the foam cut off's as support, I hate throwing away cut off's and this time it payed off.
Lift engine, just staged in place with wood screws, bolts w/ washers will be used later.
Thrust engine. You can see the markings inside where I plan on installing the vertical braces that will hold onto the rudders.
Everything is modular. For cleaning and storage purposes.
Added foam everywhere for bouyancy.
When I had the craft finished and took it out for initial testing, I did a bouyance test where I simply held it under water (up to the shaft of the lift engine) and it popped right back out, I even started the lift engine and the entire haul drained in about 20 seconds!
Paneling the under haul, and fiberglassing with 4oz matting.
A closer look, you can see the pin holes I made where I plan on drilling holes for the air to escape.
Pre paint staging of everything. Its ready to go except the skirt.
Rudders are made of balsa and covered with aircraft covering (Ultracote).
The radio box is a sandwich container to keep things dry.
I used a metal gear 1/4 scale digital servo for the rudder, and regular servo's for the throttle on both the thrust and lift engines.
Front of the engine pod, this will get a little hatch when done.
The thrust engine mount. I used the carb that came with the engine, but later upgraded to a stock HPI Baja carb.
The cowl is attached with 4 screws, it seems to hold ok, only had one problem of it loosening off, but fixed it with longer screws.
Everything is coated in epoxy for water proofing.
The opening for the lift engine, after hours of sanding and checking, I got the right size without rubbing from the blade.
Lots of holes drilled for both lightening and better airflow.
Haul is sanded and waiting for paint.
And here it is painted, finally!
I decided to only drill the upper row of holes first. Figured it'd be easier to drill more holes, instead of patching them.
Another good angle to show how the holes were placed.
First test with both engines running. Thats just a blanket under it, not a skirt.
First attempt at making a skirt, I rushed a little bit and just sewn the whole thing together without considering the edge pieces, so I had to stitch rip it, but before taking it all off thought this was a great way to show how the airflow works.
First skirt attached, with badly puckered edges.
Back to the drawing board with the skirt, and I came up with this idea to make a template. Learnt this idea from pipefitting school by using ordinates. Altho this "pipe" wasn't round, the idea was the same.
This is how I got the shapes under the cardboard, and how I got these shapes was from a simple cross section skirt layout I found on the internet.
And here's the resulting template that I used to make the edge pieces.
And the final product.
UPDATE: These pictures were taken a few years after the picture above. (Feburary 4th, 2012)
Had some fun out in the snow. Here's what the bottom looks like. From finishing the hovercaft, this is all I changed, I drilled these 3 big holes to allow more air to pass under the skirt. I figured since the engine was moving a lot of air with that VW blade, I might as well give it a chance. It didn't affect the skirt firmness at all after this mod.
Another under shot. The reason I have so many is because NOBODY takes pictures of the bottom of their hovercraft. I really had to imagine how its done, how the skirt attaches, and what you use to "land" on. The black pipe I have on the bottom is some piping I found at homedepot thats pretty lightweight. I can't remember what it was originally intended for.
Another shot, with a gopro camera on the top.
Hard to tell, but it gets pretty oily and dirty under the thrust engine.
Yeah, you can see the mess here. But in the long run, and even in leu of the advances in electronics, I still love the sound of a engine roaring.
I got some great video from the gopro. Check it out below, or in my video section.