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?

[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.

[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]

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 ?

[EmptyNester]

You use two part marine foam to fill the void between the cockpit walls and the lift duct. The foam is as strong as a glue and it gives some structural integrity to the lift duct.



The foam expansion rate is based on the temperature. At 70 degrees it doesn't do much. They recommend 80 degrees. I did this in March, so it was pretty cold. I ran the torpedo heater pointed at the void I was filling. I poured the foam when it was about 105 degrees. It grew like crazy.

The last picture it after trimming the foam and glassing a piece of 1" foam insulation on top.

[MigPlazArc]

So how long is this boat and how big are the air motor blades gonna be?

[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]

The first picture shows the bottom after it's been finished and painted. The skirt attaches on the unpainted wood on the edge of the hull and the inside attached on the wood strip at the top. You can see a hole between the inner skirt attach strip and the outer edge of the lift duct. That is how the skirt is inflated.

The next picture shows the mounting strips for the cockpit wall and the center seat. The center seat also covers the steering mechanism and the lift fan drive belt.

[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?

[d.fisher]

Jason,

But, the biggest cost has been using the hovercraft as an excuse for tools.

I do the same. Oh darn! I must buy this welder*, if not for this welder*, I would never complete this project properly!

On a more technical note, do you need to use a special epoxy that does not melt the foam. I know some epoxies and glues can be pretty aggressive against plastics and foams and such.

by the way, it looks like a great project, and I'll be following your progress

[EmptyNester]

On a more technical note, do you need to use a special epoxy that does not melt the foam. I know some epoxies and glues can be pretty aggressive against plastics and foams and such.

You can't use polyethylene based epoxy, it will melt the foam. I made a mistake and tried to use bondo fiberglass repair to fill a couple small holes. All it did was make a couple very bigs holes.

I used a "standard" epoxy resin.

[d.fisher]

Thanks for the info. on the resin. I haven't experimented much with it, but it's good to know, the only time I ever tried to bond foam together resulted in disaster.

Once again, really nice work! Can't wait to see some video of the craft in action. I'm sure it's been asked in the past, but how much does the craft weigh?

d.

[EmptyNester]

I'm sure it's been asked in the past, but how much does the craft weigh?

The specs say 500 lbs. But, I think that may be on the heavy side.

The primary components are:
engine - 100 lbs.

hull:
- 7 sheets of 2" extruded styrofoam insulation (got mine at Lowes)
- 7 sheets of 1/4" marine grade plywood
- 1/2 sheet 1" extruded foam (on top of the front)
- 2 part marine foam (fills around the lift fan)

(3) 1"x4"x16" for cockpit stringers and skirt attach strip
(1) 4' x 8' x 1/4" for seats
(1) 4' x 8' x 1/2" extruded foam for rudders and trim wing

Epoxy and fiberglass

Drive train components:
- rear drive pulley with bushings
- rear idlers pulleys (2) for 90 degree bend to prop
- front idler pulleys (2) for slight bend to lift fan
- lift fan drive pulley with bushings

Skirt material (this was much heavier than I would have though - I would guess aroudn 30 pounds).

[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