RE: GEVs

I understood what you meant (even if I did a poor job of describing it).

It is the same principal of design used in making ships. In designing a
ship, you need to make sure that the hull will generate enough pressure
on
the water to equal or exceed the mass of the ship (and in doing so, it
will
displace a mass of water equal to the mass of the ship).

I do not know how much mass a given surface of water can support. But it
wold be the same for ships as GEV's (except that all ships are partially
sunken). 

Take a ship of 10 tons. Mark the waterline on the hull of the ship while
it
is at rest. Compute the suface area of the marked area of hull. This is
the
minimum area that a GEV, of 10 tons (minus the mass of the air in the
skirt)
would need to cover to float on the air trapped in the skirt alone. Now
as
you add pressure within the skirt and start to move air through the
skit,
the craft will begin to hover (the air escaping out the bottom of the
skirt
effectivly also adds to the surface area being used by the GEV to stay
afloat/hover. You can now reduce the size of the skirt as long as you
maintain the same volume of air passing through the skirts. Although it
may
be a good idea to keep a larger surface area incase your engines are
hit. 

To take your example and add the output of a Saturn V rocket engine
through
the skirts, you can now hover your 80 ton block (but you better have
good
gyros to keep it from tilting).

-----
Brian Bell
bkb@beol.net
http://members.xoom.com/rlyehable/ds2/	     
-----

> -----Original Message-----
> From: Roger Books [SMTP:books@mail.state.fl.us]
> Sent: Friday, 1999.12.03 12:26
> To:	gzg-l@CSUA.Berkeley.EDU
> Subject:	Re: GEVs
> 
> On  3-Dec-99 at 12:00, Bell, Brian K (Brian_Bell@dscc.dla.mil) wrote:
> > An interesting question.
> > A GEV must displace an amount of air equal to or exceeding its mass
in
> > order to hover. 
> > 
> 
> Not quite, it must put enough pressure in the plenum that there is
> as much pressure on the ground as the mass of the GEV.
> 
> > Perhaps I misunderstood the question, but it seems like you are
asking
> what
> > if you took a battleship that you know will float in Lake Erie and
put
> it
> > in a pond. It would sink because there is not enough water to
support
> it.
> > But then a battleship is not designed to work on both land and water
> like a
> > GEV. 
> 
> Let's get extreme so I can make my point.
> 
> I have an 80 ton block of iron sitting on a 1 cm x 1 cm skirt.  This
skirt
> has air in it equal to 80 tons/cm^2.	I put it over the a 300 foot
deep
> lake.  It's pretty obvious it will bubble wonderfully as it sinks to
the
> bottom.  We have to pay attention to wether our tanks will do this
also.
> If the pressure required to lift them is greater than what the water
will
> support they will sink.
> 
> If our Slammer Tank sinks in water that means it is going to sink in
> swamp.  As a matter of fact, much as I would like it to be, I can't
> see a situation where a GEV that sinks would be more useful than a
> tracked tank.  I guess with proper equipment it could jump short
> puddles, but it won't do an amphibious assault.  So, anyone have any
> idea what the max is we could use on the cushion?  Sounds like 
> a little empiricle testing with an air compressor, a tub of water and
> some bricks is necessary.
> 
> Roger (who currently has no compressor)