Re: [PSUBS-MAILIST] Re: Variable Ballast Calculations, Bill

[Carsten Standfuss <Merlinsub@t-online.de>]

Carsten, I have a few questions I wanted to ask your advice on, about
this hybrid ambient/1atm sub idea I have.
 
You wrote..."If you drive dynamicly such a partley ambient boat close to
the surface
the hatch will pop up.. Or you have to design an expensive double acting
bajonet hatch. "
 
(1). If you filled your hybrid ambient/1atm sub's ballast tanks as much
as they could be filled at the surface,
 
and the sub was under with just the tower unsubmerged, (like in the
Hunley) and then you CLOSED the water inlet
 
valves going to the ballast tanks, so no more water or pressure for the
moment could come in, and next completely submerged 
 
using only forward motion and the dive planes, wouldn't that put enough
pressure against the hatch, from the outside water pressure, to keep
 
it from popping up, especially since you CLOSED the ballast tank's inlet
valves so no more pressure could come into the hull and
 
then when you were submerged a few meters the outside water pressure
would keep the hatch shut and THEN you could
 
reopen the water inlet valves to further fill the tanks. Would this work
Carsten? Before you answer though, go to this link....
 
http://home.att.net/~JVNautilus/Hunley/reconstruction.html  now move
your cursor over the sub and when the ballast tanks
 
appear and highlight, click on them and then in the popup window scroll
down and read " Displacements and Capacities", and also
 
"Analysis" where it explains the sub went under always slightly buoyant
(like the Holland) because they could not fill their tanks FULLY at the
surface
 
(they could only fill about half full)   until under a short distance,
and it says the sub was pushed under using her dive planes only until 
 
superior water pressure allowed water to fill the tanks more when
submerged deeper. So when she initally dove, with her ballast tank water
 
inlet valves open, she was acting as an ambient sub but her hatches did
not pop off. 




Yes will work.. but.. you have big and only partly filled tank - not
very stable sub.. to much free water surfaces. 
And than you make maybe a dynamic dive error and drive the sub dynamicly
on the surface - with a inside presure higher than the outside. 


 
 
You wrote..."If you install a overpressure vale - you will lost the air
you later
need to pump the tank out.. "
 
 
(2). Carsten.  I assumed the only time there would be an interior
overpressure problem would be in accending, so I ask your advice on 
 
how these situations would work.
 
a. You shut off your water ballast tank inlet valves at 2 atm. You
continued to dive forcing the sub under with only her dive planes to 4
atm
 
because the sub did not want to go past 2 atm in depth because it was
equalized and neutrally buoyant at 2 atm, so now you decide to 
 
surface from 4 atm with a 2 atm hull interior. If you didn't force the
sub up with your dive planes wouldn't she accend on her own and once she
reached
 
2 atm wouldn't she become equalized to the now 2atm outside water
pressure and become neutrally buoyant and hang there at 2 atm without
surfacing?
 
b. You have done everything in (a.) and now you want to accend to the
surface from 2 atm. with a hull that is also 2 atm.
 
You have two choices to accend. You either pump the tanks out and accend
and have no overpressure problems because your atmosphere expanded 
 
to 1 atm again, or you use the dive planes only and accend and while
doing so forget to pump your air down and are just powering up using the
planes. 
 
If I installed overpressure valves that would sense when the inside air
pressure was greater than the outside water pressure so they would
automatically 
 
open my ballast tank's inlet valves to allow the water to be pushed back
out and the atmosphere to expand again without me losing any air, would
that work?  
 
I never intended to exhaust the air out of the sub by using an
overpressure valve, but for that safety overpressure valve to
automatically open the ballast tank valves 
 
(in case I forgot to) and let the expanding air pressure from accending
push the water out of the tanks. 
 
Would this work Carsten?

Yes - a overpressure vale witch open to the softballastwater tanks is a
great idear. 
 
 
You wrote....."Small note : According to the class rules for manned
submarines you
should able to blow the soft tanks at the surface 4 times and the hard
tanks at the maximum operation deep 3 times...  Hmm.. 4 times .. maybe
the pilot should wear a Astronauts-suit ?
 
(3).  I am unaware of class rules for non tourist subs here in Florida. 
When I called the
 
authorities here about registering a submarine they told me it would be
registered as a normal boat as long as it
 
had some kind of motor. That appears to be all I have to do here is
register it as a boat.
 
But if I DID have to blow tanks 3 and 4 times at the surface I could
carry air tanks to do so, but would not ordinarily 
 
have to use them because I was regenerating my ballasting as Paul put
it, that way I would have the air tanks 
 
if I needed them but would not ordinarily have to use them and therefore
be less 
 
dependent on ever running out of ballasting air. Would that work?



Yes would work. The class rules a written to make a minium saftey
standards to commercial used vessels.. 

 
 
You wrote...."and at 2 bars (20m or 60ft) a diver has a "zero" bottom
without decompression of about 40 minutes.  At 3 bars (30m or 90ft)
of 15 minutes. At 4 bars of 5 minutes."
 
 
According to my P.A.D.I. dive tables, there is a slight technical
difference between an ata (also known as atm)
 
and a bar, but it's so minor that for diving applications it is
disregarded because they are almost the same.
 
Basically BAR = ATA or ATM.
 
According to P.A.D.I.  dive tables 1 bar/atm is at the surface, 2 bars
is 10m or 33ft, NOT (20m or 60ft).
 
and 3 bars/atm is 20m or 66ft NOT (30m or 90ft).
 

Yes that is technical corret - 2 bars at 10 meters. I give only the bars
for Atü (pressure on top of the groundload of 1 atm)

 
My P.A.D.I.  dive tables read that I can dive to 2 bars (33ft) for a
maximum of 205 minutes without having to do
 
any kind of decompression. It reads that I can dive to 3 bars (66ft) for
a maximum of 40 minutes without having to
 
do any decompression. It reads that I can dive to 4 bars (99ft)  for a
maximum of 20 minutes without having to do any
 
decompression.
 
So you can see that if I pressurized the hybrid sub's interior to 2
atm/33ft, and then closed the ballast water inlet valve 
 
and then further dove her to 4 atm forcing her under with my dive
planes, I could stay at a depth of 4 atm/99ft, for 205 
 
minutes in my hybrid sub as compared to only 20 minutes in a typical
ambient sub because my interior is pressurized 
 
to 2 atm/33ft while outside it is 4 atm/99ft. This is not me saying
this, this is the official P.A.D.I. diving tables saying this. 
 
Could you please check your figures for accuracy that you posted on
those depths and times again Carsten?


The simple question is : Why ? The hole concept of a dry ambient is
crazy.. I mean add some thickness to the shell and forget the ambient
concept for a dry boat. A dry ambient has the same displacement than a 1
atm boat of the same size - right ?
 
Finally, I am asking your opinion Carsten, if I did all the above things
I wrote in 
 
this post.....(automatic overpressure valves to open the ballast inlet
valves, air tanks available even if not normally necessary,
 
hull built to withstand at least 2 bar/ata/atm water pressure with only
1 atm inside it),..... wouldn't this
 
make a safe and workable ambient/1atm hybrid design that would enable
you to obviously dive to 4 atm
 
for 205 minutes instead of 20 minutes without having to decompress at
all?
 
Sorry this post is so long. There was just no short way to explain and
ask these things Carsten.
 
Your answers and advice would be greatly appreciated. I highly value
your advice Carsten.
 
Thanks,
 
Bill.

Bill your boat needs more attention to pressure inside and outside the
boat in and outside the tanks. etc. 
Is simillar to a scuba diver with open air supply system and a
rebreather diver. The Open air diver has the easier to handle system -
the rebreather is much more complex  and not so easy to handle. So why I
use since years a rebreather system were you have to check your flow,
your overpressure vale, your scrubber, your O2, your gas, your valves
etc etc..  ? The answer is I can stay with a rebreahter longer and
deeper as with the open system. So the need of more attention is worth
each cent. 
You dry ambient concept needs more attention as an simple 1 atm boat but
can not stay so long as a 1 atm boat - so why ?

regrads Carsten




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