One day I decided to build a hovercraft...

I did a little web surfing and came up with this baby...

The 12T4 from Universal Hovercraft

Hovercrafts are amazing vehicles that levitate above the ground using air pressure. Since they don't touch the ground you can pretty much drive over anything. Our model, the 12T4, hovers 8" over the ground and can carry 2 people at a top speed of 40mph. The frame of the craft or "skeleton" is composed of 7 width-wise "ribs" numbered starting from the front, and numerous 3/4" "stringers" that run length-wise to hold it all together. The frame is covered in a "skin" of 1/8" plywood (expensive and very hard to find). The "skirt" is a heavyweight coated nylon that surrounds the bottom of the craft and holds in the air. It is powered by two lawn mower style engines.

So, I ordered the plans for $29.95, and scouted out some help; Ruppert my German roommate, and Blaine my next door neighbor and thatís where it all started.

The total cost of building this thing was $2000 and we built it over a period of about 9 months. Here are some Photos From the project in progress. We had a great time doing it and learned a lot about ruining clothes. We even got an article in the Santa Barbara News Press about it, and a spot on a local Spanish television broadcast.

Santa Barbara News Press Article

Step 1 - Building The Propellers

The first step we took in the project was to build the required 2-blade thrust propeller, and the 4-blade lift fan. This is the point at which most people exclaim 'Build them?!?! Are you crazy? Aren't they hard to make? Why not just buy them?' The answer is 'yes', as a matter of fact they are, and if you find yourself saying something like this, you are probably not someone who would take on a project like this anyway, and will never really understand why we did. Each propeller took approximately 40 hours to create, and was an excellent learning experience.

In building a wooden propeller, the first step is to take the appropriate number of plies of wood (we used Douglas Fir) and laminate them together using a very strong and expensive 2-part marine grade epoxy to form a propeller 'blank'. Next this 'blank' is carefully marked with rough-cut dimensions corresponding to the desired blade pitch and radius. The rough-cut is then performed using a band-saw. After the rough-cut is complete, a belt-sander is used to profile the exact airfoil of the blades. The resulting 'wing' is then coated with fiberglass and epoxy to seal the wood from the elements and to provide strength, since the blades rotate at 3500 RPM, which means they could hit an object 100-200 times per second! Finally the propeller is statically balanced, using a balancing rod and a levelled rail set and the mounting hub is centered and attached using Grade 5 hardened bolts.

Here, I am rough cutting the Thrust Prop with a band saw.

The Lift Fan after being laminated, dimensioned, and rough-cut

A precise airfoil profile is important for high performance.

The finished Thrust Prop mounted to a 10hp Tecumseh (piece of shit) lawn mower engine.

The finished Lift Fan waiting to be mounted to a 6hp Briggs And Stratton lawn mower engine.

Both finished propellers...

Who needs to dust out the garage if you have one of these. Although other things that accidentally get sucked up are generally destroyed.

Step 2 - Building The Craft And Trailer

The next step we took in this project was to build the craft itself. Here Blaine and I are lining up the ribs of the skeleton to be secured with the stringers. Every joint has been epoxied and reinforced with wooden strips. Blueprints are on the wall.

The frame is starting to take shape. Here we are laying out plywood to get an idea as to the shape of the bottom of the craft.

Putting 1/8" plywood on the bottom of the craft with epoxy. Two part epoxy is a good way to permanently ruin your clothes.

Here, the bottom skin has been attached and the seams have been fiberglassed. The bottom is (hopefully) waterproof by now.

Here I am, sanding the inside of the craft.

Looking forward at Ribs 1, 2, 3, and 4.

Rib 4 which will eventually become our seat.

Looking back at Ribs 5, 6, and 7.

Skeleton complete and waiting for the Lift Duct to be installed.

The Lift Duct being formed using the sides of an old table cut into two discs.

The Lift Duct installed! The milk jugs are for emergency floatation.

The steering rudders are made from foam and fiberglass, just like a surf board. Here they are waiting to be painted.

The aerodynamic profile was cut with a hot (warm) wire.

Here the steering hardware waits to be installed.

We picked up a trailer for $80 and spent a week modifying it.

On it's way to National Autobody And Paint to get painted. (Thanks Joe!)

The paint job was a success!

The three blind mice take a moment to admire their work.

Craft near completion with lift and thrust engines mounted on 'new' trailer.

Step 3 - Testing And The Maiden Voyage

We thought we were done after it was built. Little did we know that was only the beginning...

Daryl:'Now what?'

Blaine:'Looks scarey, should we try it?'

Ruppert:'I am standing over here!'


Successful maiden voyage at Lake Nacimiento. I only hit 1 tree!

Some Things We Learned

  • Know what you are getting into. The project will take much longer than expected.
  • Quality is worth the extra expense. Better tools and higher grade materials will make your live easier.
  • Take the time to set up your work space before starting the project. Make sure powerstrips and tools are convenient to use.
  • Buy jump suits, surgical gloves, and 'The Epoxy Book' by Systems Three. Two part epoxy makes crazy glue looks like solvent. As time goes on you will get intimately involved with fiberglass and epoxy and the shit never comes off.
  • Never drink while working. Instead test out the propellers at 2 AM and try to blow your friends down - neighbors love this one.
  • Measure twice and cut once. Correcting mistakes is a pain the ass and they will happen. Precision pays off when the next step goes smoothly.
  • Do not be afraid to deviate from the blueprints, they are not the best method for everyone.
  • Communicate with everyone else that is in on the project. Custom modifications are a good way to screw yourself over if they are not known by everyone.
  • Look for help on the net when needed. Pictures on the net are a good source for help. There were many times when the blueprints did not provide enough details.
  • Know your chemicals and materials. We mistakenly put resin over epoxy to save money. The resin did not hold so we had to remove it with a blow driver and chisel over two weeks.
  • Drive with caution at first. There are no breaks however I think hitting a tree is just a right of passage here.

  • Directions on driving the hovercraft

  • Throttle for the thrust is on the stick.
  • Throttle for the lift is the silver lever in the dash. Turn it up for more lift.
  • The engine cut off switch for thrust is the red button on the left.
  • The engine cut off switch for lift is the red button on the right.
  • An engine cut off switch takes 5-10 seconds to stop an engine. Hold down the button. Because the cutoff switch does not work immediately it is _very_ important to use this well in advance.
  • Drainage plugs are located in the back, behind the skirt.
  • Step on the grey stripes only while walking around the craft.
  • Starting for the first time:
  • Maneuvering

  • Some Adventures We've Had

    Dan's Mexican Adventure

    Hovercraft Log
    Date Location Description
    San Marcos High School
    Very first trial and the thing worked. We were running out of daylight and needed someplace to test out both engines simulataneously so we set up in the parking lot of the high school across the street. We did not have a throttle for the thrust yet so one person steered while the other pulled the bicycle cable that controlled the thrust engine. We were all shocked to see it hover and accelerate for the first time. It moved over speed bumps and those cement blocks in front of parking spaces like they were not even there. We also decided that braking is definetly a very significant issue so engine cutoff switches will be needed. We kicked up a lot of gravel and dirt. Dirt gets everywhere, inside the craft your hair, ears, everywhere. The key here is to find surfaces that do not have as much gravel.
    Storke Field
    The Santa Barbara Newspress came out to do an article. UCSB was on spring break so we decided to try out Stork Field by Harder Stadium. The craft moved slugishly on grass. On grass air may be leaking through the blades of grass. We all took turns, including Rupert, Daryl, the reporter, cameraman, and myself. The article can be found here, Santa Barbara News Press Article
    Storke Field
    Telemundo Channel 47 contacted us on doing an article for their news channel. We went out to Storke Field again. The guy on the tractor cutting the field was nice enough to stand by for a few minutes. The hovercraft moves at maybe 25mph on this grass. The news segment appeared on TV in spanish, I need to digitize it or get a translator. The camera man didn't speak english very well but that was cool because driving the hovercraft is pretty simple when there's nothing to run into.
    Lake Cachuma, Storke Field and Goleta Beach
    We arrived at Lake Cachuma on April Fools day of all days and were not let in the park. That day we were told that the craft "had to be certified by the Coast Guard to enter the park." So the parks people cried about Lake Cachuma being safe by not letting people touch the water and bla bla. But the craft does have a CF number and HIN(kinda like a VIN for your car) from the DMV. I went through the laws put up by the Coast Guard and confirmed over many phone calls that our hovercraft does meet all boating regulations. What could be safer for a lake then something that does not touch the water? So Lake Cachuma would not let us on the resevoir because the bass fisherman were jelous that they didn't have such a cool boat. Acutally County Parks rule 2687c states something like to operate on a lake the craft must be determined to be of standard design as determined by the director or a deputy for canoes, cayaks, rafts, and/or inflatables. In a nut shell anybody dressed up in a funny hat can do whatever they want. We all disagree with this and encourage y'all to flame the director by writing to:
    Attn: Jeff Stone
    Cachuma Lake
    HC 58
    Santa Barbara, Ca 93105
    So we took off to Storke Field again. Jeremy, Daryl and I set up up a slalom course - no problem at low speeds. Then we decided to try it for the first time at the beach. We lauched at Goleta Beach and everything looked great. But as we got close the salt water, the engines cut out. Salt water is more conductive than fresh water and we now know that the salt water shorted out the electrical system in both engines.
    Goleta Beach
    We tested the engine by dousing it with water then spraying the engines with salt water. So we went off to the beach with high hopes. We encountered the same problems with salt water as the day before. However the problems were less severe as we encapsulated the spark plugs in thicker rubber boots. It was a bit embarassing to draw a crowd then get it stuck in water and take 10 minutes yanking cords to restart the engines.
    04/07/00 Goleta Beach The craft now works fine over salt water. We insulated all electrical contacts with silicon gel. It was a bit nerve racking to see it hover for the first time over the ocean but it never cut out. I learned how not to maneuver the craft by trying to drive through an inlet and running into the cliff. A hole was punctured into the bottom of the craft. It is now reparied to where that part of the hull is a bit stronger. We let some random UCSB engeineering student try it out then Daryl took out a guy with his 9-year old son. He then emailed Daryl to say that his 9-year old son has been putting lego hovercrafts together ever since that day.
    Goleta Beach
    Had a nice day at the beach for a few hours. We gave rides to a lot of friends in the Henchmyn band. Unfortunately some student drivers got a little too close to the beach goers and a county parks guy was there to tell us to take the hovercraft home. That and Daryl scaring several hundred birds in the air ruined our welcome. It is pretty amazing every time the hovercraft goes from land to water - almost like watching someone walk on water.
    Goleta Beach
    KEYT Channel 3 came out to film us at the beach. We got it running on a foggy day with low tide. It runs very fast on wet sand. Daryl was driving pretty fast along the wet sand and thought he could make it between the columns of the Goleta Pier. Well it was great for the camera up to the point where Daryl decided that wasn't a good idea and turned around. But the the craft was moving too fast and did not slow down in time before bumping into the pier. And once again the County Parks guy was there to advise us to get insurance before returning. The incident with the pier scratched up the lift prop and the lift engine mount. The lesson here is to be more careful when on smooth surfaces.
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