RE: [DSII] Sinking hover tanks

The Ekranoplane uses a slightly different ground-effect technique to
generate lift.	The downflow of air from the wings rebounds from the
ground and back up to provide additional lift to the craft.  This effect
is limited to a height roughly 1/2 the wingspan.  In addition, the lift
effect only kicks in at speed, so at low speeds (i.e. taking off) the
Ekranoplane is just a fast boat and sits in the water.	It has no
capability to hover or move slowly over terrain.

As for a heavy GEV craft being able to get across water - think skipping
stones.  Obviously rocks are denser than water, but it is possible to
skip them right across a pond.	Don't know if you can do that with an
air-cushion (not enough substance to redirect all that momentum quickly
upward) but in theory a fast moving object with constant propulsion
should be able to skip indefinitely across water.

Perhaps tanks could be equipped with a small set of retractable
hydroplanes to provide additional lift?

--Binhan

-----Original Message-----
From: owner-gzg-l@lists.CSUA.Berkeley.EDU
[mailto:owner-gzg-l@lists.CSUA.Berkeley.EDU] On Behalf Of Roger Burton
West
Sent: Wednesday, May 25, 2005 9:58 AM
To: gzg-l@csua.berkeley.edu
Subject: Re: [DSII] Sinking hover tanks

On Wed, May 25, 2005 at 11:53:07AM -0400, Roger Books wrote:
>Some time ago we had a discussion about heavy hover tanks over water.
The 
>conclusion was 
>that if the tank massed enough that the pressure/area (PSI in US terms)
was 
>too great the tank
>would sink while furiously blowing bubbles from under its' skirt.
Basicly a 
>Hammer's Slammer 
>hover-tank would probably sink.

ISTR that this does indeed happen in one of the stories.

>The thing we didn't discuss was how movement would affect this. If the
tank 
>were moving at
>100KPH would this affectively give it a greater area under the skirts?
>
>Any ideas?

Depends on the design, but generally the skirts are designed to keep
outside air away from the cushion as much as possible. I very much doubt
that compression under the leading edge will be significant compared
with compression from the main lift fan.

On the other hand, a vehicle could be _designed_ for this mode of
motion; googling for "ekranoplan" will show a lot of vehicles that were
quite specifically intended to operate over water.

R