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Author Topic: Can a Hovercraft really fly ?  (Read 27886 times)

Offline neilep

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Can a Hovercraft really fly ?
« on: 24/12/2007 21:29:21 »
Hi Hoverologists !

See my Hovercraft here ?



Nice eh ?...there's nothing like a hover drive upon the lake in my garden after a good meal !

But, say I wanted to increase the down force and add some wings....would my hovercraft fly ?


..well...would it ?

I just don't know.....!

Hugs

Neil
xxxx



 

lyner

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Can a Hovercraft really fly ?
« Reply #1 on: 27/12/2007 19:49:29 »
If you gave a steamroller big enough wings it would fly!
(Sorry, Neilep.)
There are three modes of ' flying' over the ground.
The Hovercraft produces a higher pressure than atmospheric under its skirt, giving it lift- until air spills out, then it doesn't get any higher.
A conventional plane goes fast enough through the air to produce a low pressure on top of its wing to provide lift. (Helicopters do this too, effectively.

There is a half way between the two which involves flying very low. When you do this, you get what is called the ground effect. Some air is 'squeezed' in between the plane and the ground, producing extra pressure underneath as well as the normal lift above the wing. This gives a very efficient (I believe) system but, of course, it needs a  smooth ground to fly over. The effect influences the  landing characteristics  of conventional planes.
 

another_someone

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Can a Hovercraft really fly ?
« Reply #2 on: 28/12/2007 10:55:20 »
Firstly, technically, hovercraft do fly - albeit only 6 inches off the ground - and when we used to use the SRN4s across the channels, the people flying them were referred to as pilots.

Clearly, as sophiecenteur suggests, you add big enough wings, and a big enough power unit, to anything (including me), and you can get it to fly.

Simply adding downforce would not help because conventional hovercraft are not designed to maintain stability after they lift more than a few inches off the ground.

Ground effect not only effects (and can be a nuisance) for conventional fixed wing aircraft, but is also an effect felt by helicopters, and there it can be very useful (which is why you will have the at first sight paradoxical concept that helicopters can fly higher in ground effect than they can when out of ground effect).
 

Offline rosalind dna

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Can a Hovercraft really fly ?
« Reply #3 on: 28/12/2007 13:43:15 »
Hi Hoverologists !

See my Hovercraft here ?



Nice eh ?...there's nothing like a hover drive upon the lake in my garden after a good meal !

But, say I wanted to increase the down force and add some wings....would my hovercraft fly ?


..well...would it ?

I just don't know.....!

Hugs

Neil
xxxx



Neil I hope that these links help and the hovercraft are not in use anymore now.
They went out of service in public services and usage from the last decade.
http://en.wikipedia.org/wiki/Hovercraft
http://inventors.about.com/library/inventors/blhovercraft.htm
http://www.northernhovercraft.com/faq.html
 

Offline neilep

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Can a Hovercraft really fly ?
« Reply #4 on: 28/12/2007 14:03:16 »
If you gave a steamroller big enough wings it would fly!
(Sorry, Neilep.)
There are three modes of ' flying' over the ground.
The Hovercraft produces a higher pressure than atmospheric under its skirt, giving it lift- until air spills out, then it doesn't get any higher.
A conventional plane goes fast enough through the air to produce a low pressure on top of its wing to provide lift. (Helicopters do this too, effectively.

There is a half way between the two which involves flying very low. When you do this, you get what is called the ground effect. Some air is 'squeezed' in between the plane and the ground, producing extra pressure underneath as well as the normal lift above the wing. This gives a very efficient (I believe) system but, of course, it needs a  smooth ground to fly over. The effect influences the  landing characteristics  of conventional planes.

This is most kind of ewe sophiecentaur. I thank ewe for your defining the three modes of mechanical flight. Hmmmm....now that would be a sight to behold.....flying steam rollers indeed !! ;D

So, this halfway house system of flying over a smooth surface...would this work well over a calm sea for instance ?....or does it need something more stable like land ?
 

Offline neilep

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Can a Hovercraft really fly ?
« Reply #5 on: 28/12/2007 14:08:42 »
Firstly, technically, hovercraft do fly - albeit only 6 inches off the ground - and when we used to use the SRN4s across the channels, the people flying them were referred to as pilots.

Clearly, as sophiecenteur suggests, you add big enough wings, and a big enough power unit, to anything (including me), and you can get it to fly.

Simply adding downforce would not help because conventional hovercraft are not designed to maintain stability after they lift more than a few inches off the ground.

Ground effect not only effects (and can be a nuisance) for conventional fixed wing aircraft, but is also an effect felt by helicopters, and there it can be very useful (which is why you will have the at first sight paradoxical concept that helicopters can fly higher in ground effect than they can when out of ground effect).

Thank ewe very much George. When ewe say ' fixed wing ' ....do ewe mean planes that their wings do not move at all...ie: do not retract and change angle etc...?.........Is ' fixed wing ' the preferred method ?...or if possible would a plane with non-fixed wings be best ?..i'm thinking of compensation for inclement weather like shock absorption.....or do most planes have some kind of shock absorption built into the wings?
 

Offline neilep

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Can a Hovercraft really fly ?
« Reply #6 on: 28/12/2007 14:11:28 »
Hi Hoverologists !

See my Hovercraft here ?



Nice eh ?...there's nothing like a hover drive upon the lake in my garden after a good meal !

But, say I wanted to increase the down force and add some wings....would my hovercraft fly ?


..well...would it ?

I just don't know.....!

Hugs

Neil
xxxx



Neil I hope that these links help and the hovercraft are not in use anymore now.
They went out of service in public services and usage from the last decade.
http://en.wikipedia.org/wiki/Hovercraft
http://inventors.about.com/library/inventors/blhovercraft.htm
http://www.northernhovercraft.com/faq.html

Thank ewe so much Rosalind DNA.....those are excellent links and much appreciated. Aren't there any hovercraft in commercial use nowadays ?..I know they are used in the military......oh poo !!..I hope they are still making replacement parts for my one. ;)

Thank ewe again.
 

another_someone

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Can a Hovercraft really fly ?
« Reply #7 on: 28/12/2007 14:43:08 »
When ewe say ' fixed wing ' ....do ewe mean planes that their wings do not move at all...ie: do not retract and change angle etc...?

Most heavier than air aircraft (i.e. not balloons or airships) use wings (the exception being rockets and vectored jets), and those wings have to move through the air in order to fly.

Winged machines have two common ways of moving wings through the air - either the wings are fixed to the rest of the aircraft, and the whole aircraft moves through the air (these are 'fixed wing' aircraft).  The other common type of aircraft are 'rotary wing' aircraft - commonly known as helicopters - where the wings move through the air by spinning above the body of the aircraft, while the main body can remained fixed in the air.
 

Offline lex anderson

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Can a Hovercraft really fly ?
« Reply #8 on: 23/02/2008 17:46:39 »
Technically, you "could" make you hover craft fly. However, you would probably want either more downward power, or wings - not both. They both operate on different processes to generate lift.

The the wing only creates lift when in motion. That is why airplanes need a runway. If that were not true, and airplanes could go straight up and have the hover ability of a helicopter. (In fact, a helicopter CAN hover because the wings are the rotors spinning at the top. If the rotors were not spinning, the helicopter could not fly)

On the other hand, a hovercraft creates lift by creating a cushion of air underneath in the "skirt" (that is what it is actually called, I did not make that up). There is a higher air pressure underneath the hovercraft than ambient air. That pressure needs to go somewhere, so it lifts the hovercraft up.

If you were able to create enough pressure underneath, you could create more lift, and if you had enough power, you could actually lift off the ground surface, whether it is water or earth.

However, as soon as the hovercraft skirt leaves the ground, it looses its trapped air pressure, and you would fall down. If you had a strong enough downward force, you would probably lift the skirt off the ground, but you would loose the air pressure, and fall back to the ground surface until you generate enough pressure to lift off again. That cycle would repeat over and over (unless your craft is dashed to pieces by the force and impact). So, with that method, you would have more of a bounce effect than flying, unless you had some kind of a power source that would be able to provide continuous lift.

But, if we had that kind of power source, your hovercraft would probably be flying already.


Here are some links to how a wing works:

newbielink:http://www.mansfieldct.org/schools/MMS/staff/hand/Flightcalclift.htm [nonactive]
newbielink:http://www.howstuffworks.com/airplane.htm [nonactive]

Here are a couple links on how a hovercraft works:

newbielink:http://news.softpedia.com/news/How-Does-the-Hovercraft-Work-53627.shtml [nonactive]
newbielink:http://www.sciencebuddies.org/science-fair-projects/project_ideas/Aero_p033.shtml [nonactive]
 

another_someone

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Can a Hovercraft really fly ?
« Reply #9 on: 23/02/2008 17:55:55 »
I may be wrong, but I'm pretty sure the earliest experimental hovercraft did not have skirts - but they never got being lab tests, they could not carry much payload, and certainly could not lift high enough to clear large waves.

In theory, if you built a hovercraft with a wade enough base area, you could dispense with the skirt and still be left with enough lift (although it would always be better with a skirt - the effect of the skirt is to make the flight height equivalent of the gap between the skirt and the surface you are travelling over, while lifting the main body of the vehicle to a greater height), but you would need to have a base dimension that was significantly larger than the height you wish to fly at.
 

Offline DoctorBeaver

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Can a Hovercraft really fly ?
« Reply #10 on: 23/02/2008 20:15:29 »
Firstly, technically, hovercraft do fly - albeit only 6 inches off the ground - and when we used to use the SRN4s across the channels, the people flying them were referred to as pilots.


Airline pilots are called Captain, but that doesn't mean that planes float like ships!  :P
« Last Edit: 23/02/2008 20:32:18 by DoctorBeaver »
 

Offline DoctorBeaver

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Can a Hovercraft really fly ?
« Reply #11 on: 23/02/2008 20:24:27 »
When I was but a kit, I had a toy SRN1 - 1 of the first, if not the first, hovercraft. My toy did not have a skirt. It had 4 tiny wheels underneath.

Here are a couple of photos of the actual SRN1. If you look at the first, there is plainly no skirt and 1 small wheel is visible.



(image from jameshovercraft.co.uk)

The large white cylinder is the motor & rotor housing, and the air is blown downwards from it.

In this next photo you can see even more clearly that there is no skirt...



(image from hovercraftmodels.com)



For those of you who may be interested, SRN stands for Saunders Roe Nautical.
« Last Edit: 23/02/2008 20:33:54 by DoctorBeaver »
 

another_someone

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Can a Hovercraft really fly ?
« Reply #12 on: 23/02/2008 22:01:51 »
Firstly, technically, hovercraft do fly - albeit only 6 inches off the ground - and when we used to use the SRN4s across the channels, the people flying them were referred to as pilots.


Airline pilots are called Captain, but that doesn't mean that planes float like ships!  :P

You may notice that the term 'captain' also refers to a military rank.

http://en.wikipedia.org/wiki/Captain
Quote
Captain is a rank or title with various meanings. The word came to English via French from the Latin capitaneus ("chief") which is itself derived from the Latin word caput ("head").
 

Offline DoctorBeaver

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Can a Hovercraft really fly ?
« Reply #13 on: 23/02/2008 22:14:38 »
Firstly, technically, hovercraft do fly - albeit only 6 inches off the ground - and when we used to use the SRN4s across the channels, the people flying them were referred to as pilots.


Airline pilots are called Captain, but that doesn't mean that planes float like ships!  :P

You may notice that the term 'captain' also refers to a military rank.

http://en.wikipedia.org/wiki/Captain
Quote
Captain is a rank or title with various meanings. The word came to English via French from the Latin capitaneus ("chief") which is itself derived from the Latin word caput ("head").

And, of course, to Captain Sensible  :D
Anyway, army captains only have 3 pips whereas a certain Castor who shall remain nameless had a crown  :P
 

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Can a Hovercraft really fly ?
« Reply #13 on: 23/02/2008 22:14:38 »

 

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