Paul,
Air bubbles under the hull?  Wouldn't that cause more  turbulence unless
vented in a low pressure location?
This is an idea  that I had thought of for a boat.
(patent applied for as you occasionally  say!!)  :D Dan F

It has been proven to work. Air has less friction  than water.

Paul Lamar

This was the original idea that lead to  the hovercraft.

Peter Whitehead.

I loved a ride in the channel  hover craft.

I recently rode a smaller one back and fourth from  Portsmouth
(South Sea Hoverport) to the Isle of Wight.


Paul  Lamar


It was also the focus of a bunch of tests done by the navy on  high speed
torpedo's..
I think they had a fish that normally did ~30knt  up to over 100 using some
form of a gas release deal on the nose of it..  [not sure of the finer
details, and it's possibly an old wives tale.. I've  never looking into it
too  deeply..]

Fwiw

Jarrett


Also the screen of bubbles  reduces the sonic signature of surface vessels,
from both active and  passive detection.
Flank III was a classified speed, but we actually had a  rooster tail, and
could outrun torpedos. Musta been the bubbles. ;-D  Westpac '81,'82, USS
Cushing DD-985.
C. Smith

Paul,

Yes  this would be a good idea for amphibians.   Even the dead weight of  a
scuba tank would be worth the extra 50 hp you need to break  suction.
Question is where on the hull do you put the nozzles.  Near  the bow on the
Vee cuff?

Doug in Japan.


I don't know  Doug. Getting on the step seems to be the big problem.
If you taxi just shy  of getting on the step and take a movie you might be
able to make a better  guess.

Ken Welter used Nitrous Oxide for years and then he redesigned  the hull
with
two steps which helped greatly as I recall.

His advice  should be very valuable.

Perhaps a valve with three compressor outlets.  One for displacement mode,
one for step mode and one for altitude  mode.

Paul Lamar

Our destroyer had outlets from just behind the  dome, and spaced at
intervals
all along the hull.
572' and 105' beam, I  could swear we were planning.
C. Smith


(http://www.fas.org/man/dod-101/sys/ship/weaps/prairie.htm)

The Prairie/Masker systems are many years old. Used for muffling machinery
noise signatures of the ships involved. The Prairie part is two belts of
pressurized air with bleed holes. One in front of the machinery space and one
after. Blankets of compressed air bubbles do the trick of insulating the
ship  from the water. The Masker  part is compressed air piped through the
propeller shaft and inside the leading edges of the prop. The same idea is in
play. To mask the sound of the propellers. The ships may stop the props
and  coast for some time while sonar people listen to a stainless wire dragged
behind  the ship. This wire can pick up the sounds of enemy submarines. It
has been  known to fall off and become entangled in submarine propellers at
every  opportunity. And we did not drop grenades in the water to screw with
the Russian  subs sonar, ever. That's a lie.

Our fighting ships have libraries of equipment sounds of all of the worlds
ships. So do the bad guys. When war is on the torpedoes are armed with that
signature as well and will hunt down a specific ship. Or, lay on the
bottom and  wait for a specific ship.

Thus the interest in not sounding like a ship at all.  The Russian
torpedoes use rocket motors, and bleed nozzle gas out the nose of the torpedo to
mask its sound and reduce drag. The Russian sub the Kursk Oscar II class was
lost to explosion while launching such a torpedo. They must be wire guided,
as  the masking works both ways. It cannot hear anything with the motor
running.

Our torpedo's are wire guided, have passive sonar (when the wire breaks)
and may have active sonar.

Lynn E. Hanover
AO-3 USS Forrestal CVA-59