Hovercraft Project

[EmptyNester]

I needed a big project once the last of the kids moved out of the house. I've always done woodworking, but wanted something different and fun.

I have always been fascinated by hovercraft and remembered seeing "personal" hovercraft on the opening of a James Bond file (one w/ Pearce Brosnan).

After looking into it, then looking more and looking even more - I decided I could do it.

It's been going on for about a year at a casual pace. I'm nearing completion.

It's been quite a project. I've learned a lot about fiberglassing and some about vacuum lamination. My overall approach is that I'm not trying to do a professional looking job - I want it to be fun to build and will be happy with half decent appearance and good performance. (It also provided an excuse to learn to weld, a lifelong goal.)

The drawing of what it should look like is attached.

Final weight is supposed to be 500 lbs (though I think that is actually heaver than it is). It's capacity is 850 lbs and the speed is 50 to 57 mph.

I got the plans from Universal Hovercraft (www.universalhovercraft.com). If you're interested, they have decent plans and they offer great technical support.

As I have time, I'll post pictures of the progress up to where I am now. (I'll try to do an update every day or so.)

[EmptyNester]

The main body is 2" foam insulation board used in homes. I ended up using "green" from Lowes instead of the normal Corning pink. So, it started as a bunch of foam sheets.

The first step was to epoxy two layers of foam together in the rough shape of the hull. It is vacuum laminated using a big sheet of plastic folded over and duct taped together and a shop vac. Since my shop vac is crappy, I bought a refurbed vacuum pump to laminate. The second picture is of the hull while laminating (left under vacuum for about 30 hours).

(You have to put blankets over and under the vacuum hose to allow even air flow through the vacuum bag.)

[Jason]

This is a thread I will be following. Do you have a estimated budget or any budge figured out yet? What are you using for a motor to lift it?

[redbeard]

(You have to put blankets over and under the vacuum hose to allow even air flow through the vacuum bag.)

I think I get what you're saying, is that inside the bag top and bottom and going to the nozzle so it provides air passages to the far end of the bag?

Did you just duct tape the vac hose into the bag at a seam?

Very cool project, looking forward to seeing how the powerplant and drivetrain is done.

[EmptyNester]

Ed -

The detailed answer is, you have the following layers.

Bottom to top you have:
1) heavy gauge plastic big enough to fold over on top of foam
2) light gauge plastic to catch excess epoxy (and protect heavy gauge)
3) foam being laminated
4) light gauge plastic to catch excess epoxy
5) blanket to allow air flow underneatch vacuum line
6) vacuum line (hose/pipe with holes)
7) blanket to allow air flow
8) folded over plastic from bottom

You then seal the entire thing with duct tape. It's easy to find leaks as you can hear them and some leaking is okay. I've been told shop vac's use air flow for cooling, so they have to have some leakage to prevent overheating.

[EmptyNester]

Jason,

On the Universal Hovercraft site, they say you can buy the entire kit for about $3000.

I'm just learning to fiberglass, so I've used more epoxy (suprisingly expensive) and fiberglass than expected. Mistakes also cost some. But, the biggest cost has been using the hovercraft as an excuse for tools. But, I'd have to say between $3k and $4k is ballpark. (I buy stuff as I go so that there is no big cash outlay.)

The plans call for an 18 to 24 hp riding mower engine. Since the "American Way" is "bigger is always better" - I got a 26 hp engine. They actually said that is a real sweet spot for performance. You can go for two separate motors (lift/thrust) or one. I'm going with one and the fan and prop are belt driven.

[MigPlazArc]

The plans call for an 18 to 24 hp riding mower engine. Since the "American Way" is "bigger is always better" - I got a 26 hp engine.

http://cumminsengines.com/every/appl...st_tier3.page?

Or if the American way is truly better... http://cumminsengines.com/every/appl...st_tier4.page?

[EmptyNester]

MigPlazArc,

That looks great. LOL But, does it come with a snorkel? I'm guess I'd be driving a very fast submarine with that.

[MigPlazArc]

MigPlazArc,

That looks great. LOL But, does it come with a snorkel? I'm guess I'd be driving a very fast submarine with that.

Haha no, but they are turbo charged! If you have a plasma cutter and a welder you could put a snorkel on

[EmptyNester]

After vacuum laminating the two layers of 2" foam, I used a hot wire cutter to get the rough shape of the hull. I cleaning it up with a "sure foam".

After the shape was complete, a wood strip was attached to the sides. It will be the attachment point for the outer side of the skirt.

After that was done, the top of the deck is shaped with a downward slope. In the second picture you can see a dent down the middle of the foam. I used PVC with holes drilled in it for distributing the vacuum. The vacuum was a little too high and it ended up compressing the PVC into the foam.

That was a pain to fill. I used epoxy and glass microspheres.

[EmptyNester]

After the hull is shaped, 1/8" marine plywood is attached with epoxy and vacuum laminated onto the foam hull. That's the layout in the first picture.

After the top of the hull is done, the bottom of the hull gets a foam "runner" around the edges. It's toped with plywood and will have a wood strip glued on for the inner skirt attachment.

The LP tank is to put weight on plywood expoyed into the hull. It is used for reinforcing the bottom of the hull to bolt the engine on.

[sportbike]

Haha no, but they are turbo charged! If you have a plasma cutter and a welder you could put a snorkel on

turbocharged....now you are talking :-) Lets put my bike engine in that thing.

Project is looking good empty nester. Any idea on payload on something like that or how fast they will move?

[I_Love_Plasma]

http://cumminsengines.com/every/appl...st_tier3.page?

Or if the American way is truly better... http://cumminsengines.com/every/appl...st_tier4.page?

turbocharged....now you are talking :-) Lets put my bike engine in that thing.

Project is looking good empty nester. Any idea on payload on something like that or how fast they will move?

You both are a little off...... I'm going to "steel" an AT-802, take the turbine out and put it my oversized, 3x size of plans, hovercraft. Like the bike engine idea And the cummin's turbo-ed. But turbine's are pretty light for the power.

[MigPlazArc]

turbocharged....now you are talking :-) Lets put my bike engine in that thing.

Yeah a 500 hp bike engine would work pretty good...But a turbocharged 15 liter with 400-600 hp stock!... Lets "chip" it and make it 750+

And I'd have to agree...That hovercraft is coming along great it looks like.

P.S. you may need more than bolts to hold that 15l Cummins in


Btw If you turn your hovercraft into a submarine I want to see a video of everybody's reaction to the strange turbulence under the water, thick black smoke bubbles coming to the surface, and the beautiful stainless steel "snorkel" air intake sticking out of the water!

[EmptyNester]

Sportbike,

It has an 850 lb capacity and is supposed to have a top speed of about 50 to 55 MPH (cruise at 45).

The thing that makes me wonder how fast I'd really want to go is that they say not to run it if there any wind until you have experience.

I've read a number of funny stories about minor crashes because the test flight is the first time they ever flew a hovercraft. (One was a guy in the UK who was going to test it in a field. He said he hadn't really thought about the fact that he had to go up hill to get to the field. He said his first reaction when he started sliding sideways down the hill was to cut the power. With no power you lose all steering control, but it takes a couple seconds for the skirt to deflate. He said the second test flight was two weeks later after repairing all the damage from sliding sideways into a fence.)

Rege

[zoama]

If you loose power over water will this hovercraft float and will you be using it mainly on land or water ?

[sportbike]

Sportbike,

It has an 850 lb capacity and is supposed to have a top speed of about 50 to 55 MPH (cruise at 45).

The thing that makes me wonder how fast I'd really want to go is that they say not to run it if there any wind until you have experience.

I've read a number of funny stories about minor crashes because the test flight is the first time they ever flew a hovercraft. (One was a guy in the UK who was going to test it in a field. He said he hadn't really thought about the fact that he had to go up hill to get to the field. He said his first reaction when he started sliding sideways down the hill was to cut the power. With no power you lose all steering control, but it takes a couple seconds for the skirt to deflate. He said the second test flight was two weeks later after repairing all the damage from sliding sideways into a fence.)

Rege

Hmmm...kind of like some jetski's (needing to be under power to steer). Some jetski's even have sensors to open the throttle if you try to steer and cut gas at the same time.

Seems if may be easier to control with two separate engines, one for lift, and one for propulsion, although I am sure you can run a prop shaft or similar to use a singe power source.

When you get this thing done and tested, hit me up, I just might have to take a ride out a see it if you don't mind, Pittsburgh's not too much of a trip.

John

[EmptyNester]

It does float. One of the strengths of the design is the bounancy of the foam. They say it can still float even if you cut it in half.

Some designs do have two engines. One drawback of two engines is that if you accidently cut the life engine instead of the thrust engine - you "plow in" (front starts diving underwater).

[DaveO]

if you accidently cut the life engine instead of the thrust engine - you "plow in" (front starts diving underwater).

In a two-engine configuration, the lift throttle and the thrust throttle could be mounted side by side with a horizontal tab on the lift throttle that overlaps the path of the thrust throttle, so that the act of reducing the lift simultaneously reduces thrust. You could reduce thrust without reducing lift, but you couldn't reduce lift without reducing thrust. There's got to be a name for that.

[zoama]

In a two-engine configuration, the lift throttle and the thrust throttle could be mounted side by side with a horizontal tab on the lift throttle that overlaps the path of the thrust throttle, so that the act of reducing the lift simultaneously reduces thrust. You could reduce thrust without reducing lift, but you couldn't reduce lift without reducing thrust. There's got to be a name for that.

At 45 to 50mph momentum would still be a problem.