Hover craft how do I get it to work?

[MohammadK]

I am planning on building a hover craft. I figured out most of the physics behind the hover craft except for.
1. What to use to hover the craft.
2. How to accelarate the craft.
3. Figure out a way for the craft to support me while hovering.
The first one may sound easy but I was thinking something as really stupid as giant fans that if build up enough energy could lift the craft. But don't think it could lift me. The second I don't know except maybe have triggers to recude how much the fan output energy is, and the third no clue. Please help me.

 

[eNathan]

Hover crafts have already been developed by an organization, where they are planning to release it next year for $1000000 per craft. They are legal and travel at very high altitudes and velocities. All I know is that the main design of the craft was red, and it was somewhat of a mixture of a jet and a hover craft. You may want to do some research on how they built their prototypes.

What to use to hover the craft.

Anything that is capable of leveling out the gravitational force of the earth, rendering your force to equal zero (at least, so that you don't fall down towed earth). I fan would be too weak.

How to accelarate the craft.

probally the way airforce #1 does it. Once the Z cords of the craft are leveled out, put thrust on the opposite direction of where you want to craft to accelerate to.

Figure out a way for the craft to support me while hovering.

It has to lift the hover craft to, which I would assume weights more than you on earth. You said you already figured out the physics of it, so I won't have to throw a bunch of numbers at you to show you just how hard it is to keep a craft in a constant state of hovering (on the Z axis atleast).

hope this helps. When your actually building the craft, (if you do) make sure to update me on it hehe.

 

[MohammadK]

Well what you said some what helps.( no offence ) [ What to use to hover the craft ] Something to render the force to equal to zero I see the most difficult. How many options do I have for this. My ignorant mind can think of only engined propelled objects. I also don't see why the craft has to weigh more then me. Please help.

 

[eNathan]

Are you attempting to say that a hover craft will not weight more than you? :rofl: You cannot make it out of plastic you know. And you do have to take into consideration the weight of the craft. What is the matirial with which you are going to build this craft?

btw, the only way to make the force = 0 constantly is to have some sort of a "force" detector. And to figure this out takes a lot of math, you definately need a computer to do this math for you. I am a software programmer so I could whip you up a code, but I am not 100% sure on how to calculate this. I know that to figure out how much force you need on the Z cords (to keep the craft not going up or down), you have to take into consideration your acceleration, the force which gravity on Earth procudes, and the weight of your airplane. A simple code could calculate this once every milli-second, and send commands to the engine to put thrust here or there. But this all seems complicated, are you sure you can swing this? You said you had all the physics figured out...

 

[MohammadK]

Yes I am most certain I can "swing" this hehe. Time is factor though. I realized saying why the aircraft should weigh more then me is pretty stupid but I was taking into consideration that the lighter the faster. I am not sure what the material will be but I don't think I should take that into consideration just yet I was thinking aluminum( really cheap good enough) or carbon fiber( highly expensive but good quality).Why do I need a force detector to keep force a constant 0? It will only detect or will it tell engine to modify calculations so thrust is in position? Also I was thinking of making my main source of lift a cylinder. This is highly effective and the math if less complex because I was reading it is dealing with 2-dimensions only.

 

[brewnog]

I am planning on building a hover craft. I figured out most of the physics behind the hover craft except for.
1. What to use to hover the craft.
2. How to accelarate the craft.
3. Figure out a way for the craft to support me while hovering.
The first one may sound easy but I was thinking something as really stupid as giant fans that if build up enough energy could lift the craft. But don't think it could lift me. The second I don't know except maybe have triggers to recude how much the fan output energy is, and the third no clue. Please help me.

1. - A fan blowing air down into a chamber surrounded by a skirt. Look at an existing hovercraft to get an idea.

2. - A fan blowing air towards the rear of the craft. This can itself be moved to provide thrust vectoring, or you can have a rudder behind the fan to control attitude.

3. - How about a seat?

 

[MohammadK]

Sounds genius.

 

[eNathan]

1. - A fan blowing air down into a chamber surrounded by a skirt. Look at an existing hovercraft to get an idea.

2. - A fan blowing air towards the rear of the craft. This can itself be moved to provide thrust vectoring, or you can have a rudder behind the fan to control attitude.

3. - How about a seat?

1. How many RPM should this fan be, and how big should the blades be. Hence, how much force will it generate on each axis?

2.

It will only detect or will it tell engine to modify calculations so thrust is in position?

The software program will give directions to the engine, to increase or decrease the thrust accordingly. Trust me, this is a MUST. Like I said the most I can do is make the code to send the string data to to engine, I am not an enegeneer.

:)

 

[MohammadK]

Uh huh well I am taking your word and your saying that this is called a Force detector? Or is there some other name? Also tell me what you think of the cylinder idea. I know that the longer the cylinder the greater the lift and I know the equation for Lift, strength of the vortex and rotational speed but problem is what type of engine are we looking at to function it?

 

[eNathan]

Uh huh well I am taking your word and your saying that this is called a Force detector? Or is there some other name? Also tell me what you think of the cylinder idea. I know that the longer the cylinder the greater the lift and I know the equation for Lift, strength of the vortex and rotational speed but problem is what type of engine are we looking at to function it?

I am in no way an expert at this. I don't think the proper term is "Force detector" because it does not really detect it, it calculates it. And this is a must have, because the amount of force you need is NOT constant, a computer needs to constantly calculate how much force you need. Meh just hook up a little lap top :rofl:

I think that the cylinder idea is great, it sounds like the most effiencent method for an engine. I am not sure that the fan idea will work, for that you would have to calculate how many RPM, and how large, the fan would have to be to counter-act on the force on earth. Gravity is a weak force, but I highly doubt that any fan that is high off the ground can gain any type of altitude.

 

[MohammadK]

Ok I see what program would I use to detect the forces? also how do I keep the force constant? and the cylinder idea is used to generate lift would I need an engine or something to rotate and stop the cylinder? What would I use to move forward? I already know how to turn left and right just don't know forward please help.

 

[eNathan]

Ok I see what program would I use to detect the forces? also how do I keep the force constant? and the cylinder idea is used to generate lift would I need an engine or something to rotate and stop the cylinder? What would I use to move forward? I already know how to turn left and right just don't know forward please help.

You simply generate thrust in the oppisite direction of where you want the craft to move, like this

/================|
<<< Direction / the |0 >>>>>>>>>>>Thrust...
<<< Of Movme \ Craft |0 >>>>>>>>>>>thrust...
\================|

Ok I see what program would I use to detect the forces? also how do I keep the force constant?

First of all, are you good with computers? I mean, very good? Are you a programmer? Like I said I could make the software to send the do the calculations, but I have no idea how to work with the hardware. The software talk to the engine, telling it "force = 50" "force = 30". Things on Earth accelerate at 32 ft/sec so your craft will have to allelerate up at 35 ft/sec, but when your craft begins to turn and move forward, that 32 ft/sec begins to change, you will need more or less force accordingly.

 

[MohammadK]

Ok I see no I am not good with computers I think I can use the program but here is the problem I understand that to move forward thrust needs to be in the oppoisite direction but what could I possible use to make it go forward the cylinder or lifts it in the air also the prototypes i have seen are defintly not going 35ft a second more like a few feet. What exactly does the engine do? How is it physical making it go forward? when youru burn the gas?

 

[eNathan]

Ok I see no I am not good with computers I think I can use the program but here is the problem I understand that to move forward thrust needs to be in the oppoisite direction but what could I possible use to make it go forward the cylinder or lifts it in the air also the prototypes i have seen are defintly not going 35ft a second more like a few feet. What exactly does the engine do? How is it physical making it go forward? when youru burn the gas?

If a hover craft is hovering in the air, they have 0 velocity and 32 ft / sec^2 acceleration. $$v = 0; a = 32 ft / sec^2$$ The 32 ft/sec^2 is just so that the craft does not plumit towerd the Earth at 32 ft/sec. Its like this

Gravity pushes things down at 32 ft/sec^2

The hover craft pushes up at 32 ft/sec^2

32-32 = 0. The craft stays still in the air. If the craft ware accelerating at 33 ft / sec, then it would have a velocity of 1 ft/sec because 33-32=1. however, if you wanted your craft to slowly land, you would have the craft accelerate at 31 ft/sec^2 which means it would be going down towed the Earth at a velocity of 1 ft/sec because 31-32 = -1. It does not have negative velocity lol, it just means that the craft would be going "down" as comapred to "up". :tongue:

 

[eNathan]

Sorry my units of acceleration were a little off. 32 ft / sec / sec = 32 ft / sec^2

Not 32 ft/sec

 

[MohammadK]

Ok I see I see I understand its the whole aeronautics getting me nuts. Let's look at what physically makes the hover craft move forward? A proprellar would work nice but if would have to be specific ( degree,rpm,length ) but my major problem is an engine where would I get one? or do I need an engine? If it is proprelled then I have have a series of triggers move the propeller but I can have some sort of "thing" to slow and fasten the triggers or completely stop them.

 

[eNathan]

you most certiantly need an engine. Although, I am not an engineer, all I can do is present the physics of it.

Are there any engineers here?

 

[MohammadK]

i dought it no body is reading this thread well i got a lot of help from you thank you.

 

[FredGarvin]

Hovercraft have been a popular college and high school project for many years. There have been more than a couple of threads on the topic on this site alone. Please acquaint yourself with the search feature and Google. There is a ton of information on this if you choose to look.

 

[brewnog]

eNathan. I'm not trying to be rude, but it seems your knowledge is a bit off.

You don't need anything to control the vertical thrust at all. You just have the 'lift' engine running at a constant speed, at a constant throttle position. If this is in excess of what is required, the hovercraft rises, air escapes from under the skirt, and the hovercraft lowers again. This cycle repeats itself, and maintains a constant clearance between the hovercraft and the ground.

MohammadK, you definitely need some kind of engine in order to propel the hovercraft. Some hovercraft use a single engine to provide both lift and forward propulsion, some have separate engines for each function, - the latter is generally favoured, especially for self-build projects.

Do your calculations, you'll probably find that motorbike engines are more than adequate for a craft capable of carrying a person.

I have no idea what you're on about when talking about triggers and cylinders. However, as Fred already mentioned this is a pretty common topic.

Good luck!

 

[MR. P]

MohammadK another way to effect hovering is by managing your 'specific gravity'. Understanding atmospheric specific gravity will ultimately lead you to a more energy efficient means of 'translating' in three dimension...


frank

 

[pervect]

Watching some of the old Junkyard wars episodes where they build hovercraft would be very instructive, though I'm not sure how one could get a hold of the relevant episodes unless one is lucky and catches them while they are on. Anwyay

What holds hovercraft up is a bubble of pressure. The pressure is created by a fan, and trapped by a "skirt". This means that hovercraft will not fly at high altititude, they are ground effect vehicles. You'll sometimes see them called by that name (GEV, ground effect vehicle).

Hovercraft are usually propelled forwards by a fan sitting on the rear of the craft. The most usual design is to have two fans for the craft, but on Junkyard Wars you can see one craft design that used one fan for propulsion and lift, a "diverter box" diverted some of the output of the propulsion fan to generate the "lift" (which is not created by a wing, but by a high pressure region under the craft as I said before).

 

[Danger]

What holds hovercraft up is a bubble of pressure. The pressure is created by a fan, and trapped by a "skirt". This means that hovercraft will not fly at high altititude, they are ground effect vehicles. You'll sometimes see them called by that name (GEV, ground effect vehicle).

You're correct about the bubble part, but a hovercraft is not a ground effect vehicle. It's an air cushion vehicle that operates on a totally different principle. GEV's require significant forward motion to achieve flight, because their little wings create the effect.
As Brewnog said, a hovercraft is self-regulating for altitude, but the biggest jet-powered ones don't get more than a couple of feet off the ground. Ideally, the skirt just brushes the surface, although the stability isn't quite that good in reality.
Ducted fans or ducted propellers are the lift/propulsion mechanisms of choice. and thrust air can be deflected to inflate the skirt if you want to just use one. For the little one-seat racing or sports types, snowmobile engines seem to be the powerplant of choice. Mine is going to be using a much bigger engine, but it's 6 metres long and I'm looking for over 160kph speeds.

edit: If you intend to take this thing over water, by US law it has to be outfitted as a boat, with life jackets, paddles, bailing bucket, ropes, etc.. You should also make sure that it'll float if the motor conks out.

 

[MohammadK]

Its not those hover craft boats its the let's see UFO looking ones except ill be in it. I wanted to know if you really need a skirt and where does it go?

 

[Danger]

Its not those hover craft boats its the let's see UFO looking ones except ill be in it. I wanted to know if you really need a skirt and where does it go?

If you're referring to what I think you are, then you're in for more headaches than any mortal should have to face. You won't have a skirt at all, because what you're talking about isn't a hovercraft. It's a flying platform or aircraft, depending upon your propulsion system. Stability control in one of those things is a nightmare, you'd have to be licensed as a recreational pilot to operate it, and the power requirements are probably more than you're prepared to deal with. You'd be a lot better off getting a helicopter license and renting one.

 

[brewnog]

If you're referring to what I think you are, then you're in for more headaches than any mortal should have to face. You won't have a skirt at all, because what you're talking about isn't a hovercraft. It's a flying platform or aircraft, depending upon your propulsion system. Stability control in one of those things is a nightmare, you'd have to be licensed as a recreational pilot to operate it, and the power requirements are probably more than you're prepared to deal with. You'd be a lot better off getting a helicopter license and renting one.

Don't put him off, I want to see this!

 

[Danger]

Don't put him off, I want to see this!

You are truly a sadistic bastard. That's a large part of why I like you so much.

 

[MohammadK]

I have a PHD in Everything related to anything in the Universe. I don't know where to put the skirt tell me where please........LOL

 

[Danger]

I don't know where to put the skirt tell me where please........LOL

Back in Smurf's closet where it belongs.

 

[brewnog]

I have a PHD in Everything related to anything in the Universe. I don't know where to put the skirt tell me where please........LOL

Mohammad, with respect I think you're in over your head.

As Danger explained, a skirt is used in the kind of hovercraft which you called the boat type. The kind you wish to make would not employ a skirt, - Danger explained what the skirt was for, and with your universal PHD then you'll be able to understand why a skirt would not be of use in your design.

 

[MohammadK]

INDEED i was only kidding though it is my fault I didn't make it obvious...( universal PHD...) but if you go to this website http://www.mahopac.k12.ny.us/mhs/teachers/finnertyk/Hover%20Craft/The%20Theory/The%20Theory.htm then you will see that they built a skirt for the hovercraft.

 

[Danger]

INDEED i was only kidding though it is my fault I didn't make it obvious...( universal PHD...) but if you go to this website http://www.mahopac.k12.ny.us/mhs/teachers/finnertyk/Hover%20Craft/The%20Theory/The%20Theory.htm then you will see that they built a skirt for the hovercraft.

We got the joke about the PhD. Brewnog doesn't let on when he's kidding either.
I misunderstood what you were talking about until you provided that link. I took the liberty of sketching up what I think is the answer you're looking for. The skirt is a flexible bag surrounding the plenum area. If you're making a really small circular jobbie, you could glue a bunch of bike tire tubes together in a stack and partially inflate them. Just tilt it to let more air out of one side when you want to move. I'll pop back in here once in a while to see how you're doing. Good luck.
http://img143.echo.cx/my.php?image=simplehover2vp.jpg

 

[MR. P]

hovercraft

mo...


A quick and dirty HC can be built in minutes by Using a gas powered yard blower mounted atop an over inflated innertube. By taking a little more time and to add rigidity, you can fiberglass the 'ducted' part, center,by laying the glass directly onto the innertube and adding struts top support engine..
My friend built one like this for Gallager the comedian. Gallager used this mini HC as a hockey puc for an electric horse that Brian built as well.

frank

 

[Danger]

A quick and dirty HC can be built in minutes by Using a gas powered yard blower mounted atop an over inflated innertube.

The main problem with that is that the plenum area is extremely small, resulting in very little lift. Keep in mind that the lift is pressure times plenum area.
I wouldn't mind learning more about that electric horse. It sounds intriguing.

 

[dhanyaprakash]

hi! can someone send me some detailed information(some 20-30 pages) about thrust vectoring. iam student in aeronautical engg. i need it for my seminar purpose.
my mail id is: [deleted]