[PSUBS-MAILIST] Euronauts Ballast and Trim System.

[MerlinSub@t-online.de (Carsten Standfuss)]

Hi Charles - 

Bigger tanks partlly filled with water, soft or hard, ambient or not, 
pressure compansate ambient or not.. will not work on a submarine.. 

The reason is what we call the "free surface". In simple words: 
If the boat move under an angle for example to the bow - the water 
in the tanks follow this angle the and the longitudinal trim and
stability get very quick out of control. Even a big Car-ferry can quick
capzied if the fire-sprinkler system flooded the car deck with some inch
of water.(but in this case to the side).   

For this reason submarine have two types of tanks : 
Big Softanks for the freeboard on the surface - allways 
completly filled underwater !
Small hard tanks partlly filled for the zero bouancy. 
If the hard tanks located near bow and stern we called them trim tanks. 

Euronaut has a surface displacemnet of 57,5 ts. 
One Soft tank in the bow and one in the stern. 
Each soft tank has = 4,5 ts = 9 ts together. 
One hard tank in the bow and one in the stern. 
Each hard tank has 0,7 ts = 1,4 ts 

The boat dives with the soft tank completly filled and the hardtanks 
to 50% = So dive displacement  in this theoretical disscussion is 
57,5 + 9 + 0,7 = 67,2 ts. 

Note : The hard tanks in Euronaut are inside the soft tanks. 

Diving : Open the vales on top of the soft tanks. 
This tanks are open at the bottom - the air escapes -water floods the
tank completly. The hard tanks are still emtpty - than I open the bottom
vale of the hard tank - water gets in a litle - but than stops because
of the sliglty compressed airbubble inside this tanks. Than open the
top-vale of this tanks until the water level is in a amount I want -
near 50% depents on the boats load and water density - close than top-
and bottom vales of this tanks. 

Surfacing : Close the top-vales of the soft tanks - open the top vale of
the hardtank and let compressed air into this tanks until the
airpressure inside is higher than the outside waterpressure. Than open
the bottom valve of the hardtanks and the water gets out - until all
water is out - than the air gets out of this bottom valve - and will be
catch by the softtank (..the hard tank is inside this tank..) The boat
surface and it depents of the deep it was and the pressure and amount of
air I blow to the hard tank if the soft tanks are completly empty or
not. If not I blow more air to the hardtank with open bottom vale until
the boat is completly in surface trim. Than I close the top- and the
bottom  vale of the hard tank. Go on deck with two metal blindflanges
with treads and close the softtank-topvales with this additional saftey
feature tight. It doesnt matter if now somebody plays with the controls
- the Euronaut is now  a surface boat until somebody remove this plate. 
Another function of this blindflanges is that we can test the functon of
the outside and remote controlled softtank-topvales without to flood the
tank. 

The reason for the size of the softtank is the amount of freeboard and
seaworthness I want. The reason for the sizes of the hard tanks is given
by the differnet density of the saltwater of the north sea (1,025) and
the baltic sea (1,0= freshwater) and the need to compensate the diffence
in the load of the boat mostly if the diesel tanks are up to 90% filled
or down to 10% empty. 

The diesel tanks are inside the pressure hull - one forward and one aft
- so I can trim the longitudinal trim with this tanks also. 

The freshwater (drinkwater) tank for the toilet, pantry and shower has
the same size than the wastewater tank - and is locate close together. 
If the freshwatertank is filled - the wastewater tank is empty - and
opposite. 

I have two ways to blow the tanks with compessed air - one is inside the
pressure hull - and the other one is outside. I have two compressors -
and two highpressure pipes systems. In emergency I can also blow the
tanks with the helium normaly use for the diver chamber. 

The air storage capacity is 30 units x each 50 Liters x 220 bars =
330000 liters so I can blow the soft and hardtanks = 9000 + 1400= 10400
liters ->  330000/10400 = 32 times ! The is no real reason to blow the
tanks so many times but most of the storage bottles are used to blow the
diver lockout lock in chamber. To blow the soft and hardtanks I need
about one bottle each dive. 

But the diver chamber has 7000 liters volume in a deep of 150 meter
this requires : 7000 x 15 bar = 105000 liters of gas before the chamber
is equal to the seapressure and the bottom hatch can be open. I double
the storage capacity for saftey reasons. 

There is another pipe so I can blow with the gas inside the diverchamber
also direct the soft- and hardtanks. To do this the boat has to to
surfac dynamicly a little so that the pressure in the diverchamber is
higher than the seapressure - then the decompression vale of the chamber
will be wired to the softtanks - and the gas can be use for twice
functions. 

There are two high pressure seawater pumps in the boat - but this are
emergency pumps to drain the bilge. 
They are not connected to the Ballast- and trim system. 

I have 3 additional drop weights - each 1 ts heavy which can be release
mechanical by turn a key 60 degrees. The reason is that this is the
fastest way to create lift in case of a leak. 

There are no seawater pipes or any outside pressure pipes inside the
sub. In fact that all dive valves are remote controlled there are no
outside pressure pipes anywere in the boat ! Only small high pressure
air pipes. If this pipes breaks inside and outside the sub (!) than only
a very little amount of water can get inside the sub. 

Hope this help..  a scetch of the tanksystem is ate WWW.Euronaut.org at
the page "Technische Daten"

regards Carsten 

Charles Perkins schrieb:
> 
> Carsten,
> 
> Do you mind telling us a little about the ballast system on the
> Euronaut?
> 
> I am wondering:
> 
> How big are your VBT (Variable Buoyancy Tanks) compared to the overall
> volume of the Euronaut (minus the Main Ballast Tanks, which I assume
> you will flood when you dive?)
> 
> How big are the MBT compared to the rest of the boat?
> 
> How do you intend to "blow" the MBT when you surface... will you use
> high pressure air, pumps, or both?
> 
> How much air for ballast purposes do you have stored in the cylinders
> in (or on) the boat? How many cylinders (of what size) does that take?
> 
> I ask about the Euronaut because that is the size of submarine that
> particularly interests me.  I do my day-dreaming about submarines
> ranging from the size of Peter Madsen's Kraka (what a cool looking
> boat!) to something the size of your vessel... I like the idea of being
> able to cruise for a couple of days surfaced or submerged before
> returning to port.
> 
> I would like to know more about Peter's new UC 3 project... It is too
> bad I can't read Danish.
> 
> Thanks all you Psubbers for putting together an excellent community.
> I've been lurking for a while now. (Isn't that what submariners are
> best at?)
> 
> With enthusiasm,
> 
> Chuck
> 
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