# Hover craft how do I get it to work?

1. Apr 26, 2005

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 dont think it could lift me. The second I dont know except maybe have triggers to recude how much the fan output energy is, and the third no clue. Please help me.

2. Apr 26, 2005

### 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.

Anything that is capable of leveling out the gravitational force of the earth, rendering your force to equal zero (at least, so that you dont fall down towed earth). I fan would be too weak.

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.

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 wont 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.

3. Apr 26, 2005

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 dont see why the craft has to weigh more then me. Please help.

4. Apr 26, 2005

### 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 definitly 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...

Last edited: Apr 26, 2005
5. Apr 26, 2005

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 dont 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.

6. Apr 26, 2005

### brewnog

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?

7. Apr 26, 2005

Sounds genius.

8. Apr 26, 2005

### eNathan

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.
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.

:)

9. Apr 26, 2005

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?

10. Apr 26, 2005

### eNathan

I am in no way an expert at this. I dont 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.

11. Apr 26, 2005

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 dont know forward please help.

12. Apr 26, 2005

### eNathan

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....
\================|

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.

13. Apr 26, 2005

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?

14. Apr 26, 2005

### eNathan

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:

Last edited: Apr 26, 2005
15. Apr 26, 2005

### eNathan

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

Not 32 ft/sec

16. Apr 26, 2005

Ok I see I see I understand its the whole aeronautics getting me nuts. Lets 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 completly stop them.

17. Apr 26, 2005

### 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?

18. Apr 26, 2005

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

19. Apr 26, 2005

### 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.

20. Apr 26, 2005

### 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!