Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Don, Maciek.
I am just back from 3- days travelling with limited access to the net, sorry for not answering and thanks to Maciek for the correct answers. A few reflections on the external ballast /fueltanks. We did not use the mbts 2 and 4 as well as the regulating/fuel tanks as bunkertanks a lot . The reason was that we used the VIICs more as a coastal submarine ( a long Norwegian coast up to the Barents sea, having easy access to fuelingstations contrary to the German long warpatrols which even force them to use milkcows. We used the external fuel/ballast tanks occasionally for training only.
Watercompensating. Having watercompensated fuel tanks is giving an extra benefit by eliminating the free surface effect as well.
Tore

[VIC20]

Just in case that someone wants to know more details about the effect of hull fouling - this old 1952 document shows a lot: https://darchive.mblwhoilibrary.org/bitstream/handle/1912/191/chapter%202.pdf?sequence=9

[VIC20]

Next version of my engine simulation which prints acceleration over time now - I think it is almost OK (except that it is a little bit too fast at max) - seems acceleration fits to what Tore said.


http://www.hessburg.com/downloads/Engine2/Engine2.html

[tore]

Mark.
Amazing! One question, as you are using the parameters primarily in the SI system why do you have a bmep in psi? I cant get the bmep figures to match the bmep.
Tore

[VIC20]

I'm sometimes using formulas with non SI inputs. But I've used psi when I wanted to compare the results (while using the Type IX engine settings) with the one on page 10 of this document:http://www.uboatarchive.net/DesignStudiesTypeIXC.htm

[tore]

Mark.
I am modifying my post
Come to think of it. The figures recorded ( bmep of 6,8 psi ) could match to average  bmep in the SI system (bar sq.cm) of the GW engines without Roots blower connected, I don`t have the figure at very low revs, however the MAN engine at 1/10 load  and 218 rpm has a bmep of 24 psi.
Tore.

[VIC20]

Sorry for late reply, I was offline because the router died.
I've used the MEP to compare it to the data of the Type IX. The printed MEP is based on the calculated torque and the cylinder data. It was extremely close to the IX engine when I've tested it with the IX data. I don't know if it currently prints out the correct values maybe I mixed up units during recent changes but I think it should be correct. Will take a closer look at it when I'm not tired ;-)

[Don Prince]

Hello Mr. Tore,


Again some basic questions on soundings, venting, and test piping ....


Q1.  What is soundings?  Do they take a stethoscope and listen for a tank to hisses or hear drips in the compartments?


Q2.  Fuel oil tanks generally are full of fuel to start, then water gets pumped into the bottom which forces fuel oil out the top.  On plate 8 and 8a, there are vent lines at the top of each tank that feeds into a measuring bucket.  What are they measuring?


Q3.  On Plate 8 and 8a, there are lines at the bottom of the tanks that feeds up to a collection funnel and it looks like it's dumped into the ocean.  Why are they doing this?


Q4.  I can't figure out how the 3 way flooding cock with lateral inlets works on Plate 8a.  photo ttached...


Regards,
Don_

[tore]

Mark.
 I have slept on your bmep in psi and guess related to the 48,5...SHP the low figure is OK. I have never reflected over or noticed it takes only 48,5....SHP for each engine, thus  a total of only 97,...SHP to push a VIIC through the water at 6,2 knots, slightly more than 1/3 of the max speed.
The US figure on a  9 cyl transferred to a 6 cyl and with Roots blower at max load, I assume would be approximately:
Max cont. 1346 SHP,460 rpm,115 psi bmep, 3/4 load 1086 SHP, 126 rpm, 95 psi bmep, 1/2 load  720 SHP 383 rpm, 72 bmep  psi, 1/4 load 361 SHP, 295 rpm, 45 psi bmep, 1/10 load  (being the lowest output they registered ) 144,5 SHP, 218 rpm, 24 psi bmp.
I do not know where they got the figures. You can not transfer the load figures based on a IXC directly to a VIIC as the hull size and lines are different, but may be it could give an indication.
Tore

[VIC20]

No, you are right something is wrong. 

[tore]

Don.
 Q1 Sounding is measuring quantities of liquid in a containers or tank. It is done in several ways like oilchecking on you car using a dipstic. Some tanks the VIIC engineroom are equipped with a kind of dipstick. Q2. The fuel/ ballasttanks have a different system based on smaller pipes,cocks, funnels and a graded container inside the pressurehull , see discussion page 46-47 on this thread .Q3  When you are fuelling, the fuel force the seawater out of the tanks and you monitor the waterlevel by the pipe going almost to the bottom of the tank by the valves ( cocks) on the top of the tanks outside the pressurehull. As soon as fuel is flowing out of the valve (cock) you stop fuelling and prevent fuel spills and as the checkpipe stop some 10 cm above the end of the compensating pipe some compensatingwater residue is left in the fuel/ballasttanks.. I have discussed the whole system on page 47 and 46 on this thread.
Tore

[SnakeDoc]

Hi Don,

some time ago, Tore described this system here:
http://models.rokket.biz/index.php?topic=921.msg12479#msg12479

Q1.  What is soundings?  Do they take a stethoscope and listen for a tank to hisses or hear drips in the compartments?

The term "Sounding" is quite misleading in this context. The German, original term is "Peil-" - that means gauging, indicating, or probing.
Simply - Peilleitung - installation for measuring the amount of fuel in the fuel oil tanks (internal as well as external).

Q2.  Fuel oil tanks generally are full of fuel to start, then water gets pumped into the bottom which forces fuel oil out the top.  On plate 8 and 8a, there are vent lines at the top of each tank that feeds into a measuring bucket.  What are they measuring?

See Tore's explanation.

Q3.  On Plate 8 and 8a, there are lines at the bottom of the tanks that feeds up to a collection funnel and it looks like it's dumped into the ocean.  Why are they doing this?

These lines are used while filling the tanks with fuel oil. Initially, the tanks are filled with water. Then, trough the fuel oil transfer lines the oil is pumped. These fuel oil transfer lines have their outlets at the top of the tanks, so the fuel is gathered in the upper part of tanks, while the water is forced out through the lines, you are asking for. The crew member is watching the funnel at the upper deck - if from the lines outlet start leaking fuel instead the water, it means, that the tank is filled with fuel and the pump is turned off.

Q4.  I can't figure out how the 3 way flooding cock with lateral inlets works on Plate 8a.  photo ttached...

Based on Tore's description, some time ago I have prepared some drawings, which can illustrate the process of fuel oil amount measuring.

fot 1.jpg - forward bulkhead of the U-570 control room with visible fuel oil probing lines.
fot 2.jpg - forward bulkhead of the U-995 control room with visible fuel oil probing lines and collecting bucket.
fot 3.jpg - control valve of the probing and venting installation in the control room of U-995
rys 7.png - probing of the internal fuel tank - equalising the pressure
rys 8.png - probing of the internal fuel tank - measuring the amount of fuel


--
Regards
Maciek

[VIC20]

The term "Sounding" is quite misleading in this context. The German, original term is "Peil-" - that means gauging, indicating, or probing.
Simply - Peilleitung - installation for measuring the amount of fuel in the fuel oil tanks (internal as well as external).

Peilen is a pretty unusual word for that esp. "Peilleitung" which I've never heard before - but the german word for the oil-level dip stick is "Peilstab" or more common "Ölmeßstab" hence it makes sense that they might have used it during that time.
From the logic of the word it should be used like you said to read the amount of fuel from a nonlinear scale.
But the word Peilung and peilen is mostly used for bearing and targeting and for understanding something - "I don't peil it" means "I don't understand it" - "I have no Peilung" is "I have no idea"

[SnakeDoc]

Mark,

The term "Sounding" is quite misleading in this context. The German, original term is "Peil-" - that means gauging, indicating, or probing.
Simply - Peilleitung - installation for measuring the amount of fuel in the fuel oil tanks (internal as well as external).

Peilen is a pretty unusual word for that esp. "Peilleitung" which I've never heard before - but the german word for the oil-level dip stick is "Peilstab" or more common "Ölmeßstab" hence it makes sense that they might have used it during that time.
From the logic of the word it should be used like you said to read the amount of fuel from a nonlinear scale.

Term "Peilen" is commonly used in the  Tauchvorschrift.

But the word Peilung and peilen is mostly used for bearing and targeting and for understanding something - "I don't peil it" means "I don't understand it" - "I have no Peilung" is "I have no idea"

You are right. The most common (today) usage is as bearing.

--
Regards
Maciek

[VIC20]

Term "Peilen" is commonly used in the  Tauchvorschrift.

I guess the usage was dropped quickly within the last decades. Actually I can't remember someone saying that. But a quick search shows that some people still use it today. (but much more people use prüfen, messen or kontrollieren). The word Peilleitung is even more rare, just 28 results with google and I think of those only one was a real hit (about a Peilleitung in an oil tank)
I really never heard that word before today. It's funny to learn something about my own language on an english speaking forum.

[tore]

Maciek-Mark.
You are much better with organising the paperwork Maciek, thanks. We use the word Peilung  Norwegian peiling just in the same way as the Germans. When it comes to larger amount like KM3 and oceandepth we use the word, sounding, like echolot sounding.
Some time ago I got a board, I guess from Maciek, showing the relation between rpm and speed for a VIIC together with the previous figures it might be of some help for checking the output, rpm, bmep and speed relations graph.
Tore

[VIC20]

I think the HP is possibly too low - But I've used the data from Maciek's picture:


http://models.rokket.biz/index.php?action=dlattach;topic=921.0;attach=5034;image


and when the line get's interpolated it just has so little HP at 180 RPM - the lowest data I've used from Maciek's picture is 158 HP at 256 RPM







Anyway the RPM of the propeller is what's used to calculate the trust so it does not affect the speed of the boat in my simulation.
The only effect it has is (if the resulting HP is wrong) is the time how long it takes to spin up to those RPMs.


I've just found out that the torque on his document does not fit to the other data of the RPM and HP:


3456 Nm at 180 RPM should be 118.44 HP which makes much more sense
6810 Nm at 256 RPM should be 244.84 HP instead of 158


at 390 and 470 RPM both curves give pretty similar results


So my guess is the RPM/HP data on the document is not correct.

[tore]

Mark.
I see, however when you are running the engine at very low outputs I guess the graph would be unreliable as the heatlosses of the engine becomes an increasingly and very large  proportion of the  bhp so I guess you can`t just interpollate the graph  down to 0 output. ( at 0 bhp you would would require a certain indicated hp just overcome the mechanical and thermodynamical losses to get the engine idling).
Tore

[VIC20]

Low RPM are not that important for me anyway.
But for the 180 RPM (which I need for KF) the HP or the MEP must be wrong on Maciek's data.


When looking at the data of the Type IX from this page 10 of this website: http://www.uboatarchive.net/DesignStudiesTypeIXC.htm


490 RPM - 2470 HP
480 RPM - 2320 HP
470 RPM - 2170 HP
426 RPM - 1630 HP
383 RPM - 1080 HP
295 RPM - 542 HP
218 RPM - 217 HP


Recalculation this with propeller law is pretty close:



490 RPM - 2458 HP
480 RPM - 2311 HP
470 RPM - 2170 HP
426 RPM - 1593 HP
383 RPM - 1174 HP
295 RPM - 536 HP
218 RPM - 216 HP


So when I do the same with the Type VII engine based on (uncharged) roughly 341 RPM (511 HP) from Maciek's data I will get


KF 180 RPM = 75 HP
LF 275 RPM = 268 HP
HF 340 RPM = 506 HP


now based on 470 RPM and 1400 HP:
GF 435 RPM = 1109 HP
AK 470 RPM = 1400 HP
480 RPM =1491 HP
490 RPM =1586 HP


So the calculation based on the propeller law for KF 180 RPM 75 HP is somewhere in the low middle of what the RPM-HP and MEP-HP data shows (50 HP and 118 HP).
The lowest data I've used is already wrong (158 HP at 256 RPM - it should be more like 216 HP for 158 RPM)
I guess the best is to "fix" the low RPM data with data calculated with propeller law and to stop thinking about it ;-)
 

[tore]

Mark.
This sounds like a better solution and bmep would be adjusted to more familiar values.
Tore

[VIC20]

Tore, I need a way to convert diesel fuel (in kg) to liters. But I have no idea about the diesel fuel used by the Type VII during war. Do you have a rough estimate?

[SnakeDoc]

Hi Mark,

Tore, I need a way to convert diesel fuel (in kg) to liters. But I have no idea about the diesel fuel used by the Type VII during war. Do you have a rough estimate?

Have you seen this: http://www.fischer-tropsch.org/primary_documents/gvt_reports/USNAVY/usn_187_45.htm


--
Regards
Maciek

[tore]

Mark
I believe the German WW2 Navy had a special specification for the  submarine fuel. During WW2 most of the fuel in Germany would be synthetic fuel made from brown coal. There are several processes which are used. My guess would be for the navy a so called hydrogeneration process was used I, believe a common process is called Bergius process (Kohleflussigung.) I still remember the smell as it had a high degree of aromatic content.  A typical specific gravity of such fuel would be in the range 0.85-0.885. This is an assumption from my side.
Tore

[VIC20]

Thanks.


Do you know if there were different types of compass repeaters on the bridge? One source says the destroyed one on the picture would be a pressure proof U-Boat compass, but I never saw one like this one on pictures.

[SnakeDoc]

Do you know if there were different types of compass repeaters on the bridge? One source says the destroyed one on the picture would be a pressure proof U-Boat compass, but I never saw one like this one on pictures.

Check out this thread:
http://models.rokket.biz/index.php?topic=1088.0
I'm not sure if these repeaters are for helmsman or they are repeaters for bearing (navigational) purposes.


--
Regards
Maciek

[Don Prince]

hello Mr.Tore and All,


I believe I have a basic understand of how the Header/Buffer tank works... 


1.  Heated water is pumped from the diesel engines and through the pressure hull to cool the exhaust mufflers.  Then the heated water is directed to the buffer tank and is channeled to the RFO tanks, the overflow pipe (which looks to dumped into the sea).  I believe the goose neck pipe is to provide air equalization in the tank.


2.  I had a problem with the lack of a closed pressurized tank.  The amount of water pressure provided to the RFO tanks is the result of the height of the water column form the deck of the Winter Garden to the level of water in the tanks.  I guess it's really ingenious; as the tank's water level rises the water pressure becomes less (self regulating).


3.  When the U-Boat submerges, the external tanks are open to the sea through the buffer tank pipe and as professor Maciek point out to me awhile back; the internal and external pressure is the same with an open tank.  The internal tanks are protected by a closed hull valve and should not see the external pressure.


I do have a question about the buffer tank.  the 4th pipe to the right looks like an arrow pointing down.  What is this?


I will post a drawing...


as always any comments are highly appreciated...


Regards,
Don_

[Don Prince]

If the U-Boat is configured to use the RFO tanks and fully loaded with fuel, is there a sequence of which tanks are used first?  From Plate 9 it looks like fuel oil can be taken from any external or internal RFO tank.


Regards,
Don_

[tore]

Don.
Compensating water headertank.
I Guess you got it OK. The headertank in the towercasing is always topped up by the attached colingwater pumps when the main engines are running and the head never exceeds the head corresponding to the watercolumn from the bottom of the tanks to the top of the waterlevel in the headertank even being submerged as the footvalves in the saddle tanks are valves which can only be placed in two positions, either to the bottom of the tanks or to the sea. We discussed this detail some times ago and Simon made one of his marvellous drawings of the system see drawing below. As you see the downpointing arrow is a drain. The fuel can indeed be taken from any fueltank and I don`t remember we followed any strict sequence, but as usual there was a communication between the engineers and the officier responsible (in our navy No 1, in the German navy chief engineer) for the trimcalculation as to which tank would be most convenient.
Tore

[tore]

Mark.
Compass repeaters on the bridge.
Sorry I was not very much involved in the compasses and I cannot remember which type of compassrepeaters which were on the bridge. I guess Macieks link can give a clue if not, I am sure there are a lot of clever guys out there having done some research on the matter.
Tore

[VIC20]

Some changes. RPM now closer to what I wanted to set them. Added faked cavitation (was too complicated to do it right) - overall the acceleration is slower now. Please tell me how the acceleration (and final speed per RPM) looks for you now. 


http://www.hessburg.com/downloads/Engine3/Engine3.html

[tore]

Mark.
It is much better, however I cannot figure out the specific fuelconsumption. At these revs and the Roots blower disengaged, I should assume it would be more like max. 200 g/bhp hour rather than 415 g. The acceleration time 0 to 6.8 knots in  9 minutes astonish me based on my feeling, but I guess it is probably OK. so I should n`t worry.
Tore

[Don Prince]

Gentlemen,


I have been looking at Plate 13 and the cooling water flow.  It looks like plate 13 does not agree with Plate 13a and 13b.  Was plate 13 drawn wrong?


See the attached drawing...


Regards,
Don_

[tore]

Don.
Your observation is correct. It is a mistake in this particular drawing and the stb enginepump , the reserve coolingwaterpump and the coolingwater handpump shall all have a connection to the crossover seacoolingwater suctionpipe. Plate 13 has a mistake.
Tore

[NZSnowman]

Hi Tore

I was just checking our cooling piping of U-1308, and I noted I have missed two things:

The Pressure Gage between the Aux CW Pump and the manifold,
And the Compressed air chambers between the CW pump and manifold.

Where would the Pressure Gage be located?
What do the Compressed air chambers look like and size?

Thanks, Simon.

[tore]

Simon.
I guess plate 13 is a bit misleading. I don`t think it is a compressed airchamber in the line it is rather the airvessel on attached pistonpump driven from the engine, see drawing below. The pistonpump has such airvessel as a buffer to ease the pressure pulses from a reciprocating pump, not needed for a centrifugalpump. The manometer could be the one up on the instrument panel front top of the engines, showing the cooling waterpressure to the engine.
Tore

[VIC20]

Mark.It is much better, however I cannot figure out the specific fuelconsumption. At these revs and the Roots blower disengaged, I should assume it would be more like max. 200 g/bhp hour rather than 415 g.

It's both for for both engines but only written on the first one. I've just multiplied it by 2 for the display

The acceleration time 0 to 6.8 knots in  9 minutes astonish me based on my feeling, but I guess it is probably OK. so I should n`t worry.
Tore

If you think it's too slow then I need to change it. But thrust is pretty low at these RPM.
When I get rid of one of my new faked stuff then the acceleration curves for KF, LF, HF, GF & AK look like this, are they better?

[tore]

Mark.
I am afraid you cannot multiply the specific fuelconsumption for two engines, as it is specific per bhp per hour thus has nothing to do with the total bhp as the fuelconsumption.
As to the acceleration, you are right, the thrust is pretty low for a fixed propeller at low revs and as my remark is based on feelings I don`t think you shall change it.
Tore

[VIC20]

I guess you misunderstood me?

The fuel consumption is based on the data of the curve "fuel consumption per hp" - it's calculated for one engine and this result of a single engine is then multiplied by 2 because two (almost identical) engines are running.


It's not like bhp = 100, 100*2 = 200, 200*fuel consumption@200
It's like bhp = 100, fuel consumption=100*fuel consumption@100, fuel consumption*2

[Don Prince]

Hello Mr. Tore and All,


I have a question about Regelbunker RFO tank 1 in the saddle tank...  Since this tank does not have a pipe from the header/buffer tank to provide a water replacement for fuel taken from the tank.  Is this tank only a storage/transfer tank and not capable of being a direct fuel source for the diesel engines?


Regards,
Don_

[tore]

Mark.
Sorry I misunderstood.
Tore

[tore]

Don.
Yes and no. It is a non watercompensated tank, but can be used as a direct source as the other tanks. However normally it is no bunkertank in direct contact with the engines as the fuel supply pipes end in the "day tank" a double settlingtank above the engines. You top up the daytank from the fuel tanks, let the fuel settle for a while so possible impurities and water can be drain while running the engines from the other tank where the fuel has already settled.
Tore

[Don Prince]

Hello Mr. Tore and All,


Now on to the Diesel fuel system...  I believe I'm close to understanding some of the functionality.  I will attach a fuel flow from Plate 9.  However, as usual I have a few questions:


Q1.  There seems to be no fuel level control in the Gravity Tank that's mounted above the walk-way between the engines.  How do they know when the tank is full, and which valve would they normally use to shut off the flow of fuel?  The same with the Collection tank except fpr the goose neck over flow spout.


Q2.  The 4 pipes coming from the gravity tank go to a collector and then to the Collection tank (I believe this tank us below the metal walking deck).  Should all 4 pipes go to the collection tank.  I would think that 2 of the pipes would be for settlement and water draining?


Q3.  I'm not exactly sure about valve "e" the change over cock with central passage.  I know it allows fuel to enter the what looks to be a separated gravity tank.  When it's feeding the other side with the drain and tank for the Junkers compressor, I'm not sure about the 2 lines going to the gravity tank.


Q4  The small bypass line on the fuel pump...  this line has a safety valve to open if the pressure gets too high.  How will this ever work because there is a huge bypass line on the outside of the pump?


Q5.  It was stated in one of the manuals that if one of the fuel pumps failed, then the Aux. Pump could be used in it's place.  If this happened, was there the possibility to fix or replace the fuel pump?  With the Aux pump providing fuel for one of the engines, would not the gravity tank stop getting fuel?


I guess that's my quota of questions for today...


Regards,
Don_

[tore]

Don.
Q 1 There are two sight glasses each for port and stb up front of the settlingtanks. Q 3 Cock "e" shut the fuelsupply to the settlingtanks and is shown in shut position on plate 9.
Q 2 Fuelcollecting tank has nothing to do with the fuelsupply to the engines it is merely a collectingtank for the fuel drain and overflow pipes from the settlingtanks, filters,pumps etc . Fuel supply from the bunkertanks to the distribution box is drawn OK, from this box the supplyline goes to the distribution selector cock "e" which has 4 positions: A. shut to the settlingtanks and engines as shown on plate 9. B ,the unusual, daytank shut and fuel goes straight to the fuel supplypump on the engines,C topping up port settling tank and supply to the engine supplypumps from stb. settling tank and D, topping up stb settlingtank and supply to the engine supplypumps from port settling tank. See drawing below.  Q4 The plate 9 shows more a MAN arrangement than  a GW engine. On the GW engine the engine driven fuelsupply pump is up front of the engine. The "huge" pump bypass as you express it is normally shut and is only used when something is wrong with the pump. The relief valve has a normal dimension don`t get confused, look at the photos on the front of the engines.
Q.5 I am not sure if I understand your question right. If you mean the HP fuelpumps on the engines, the engine had to stop and a spare pump fitted, routine.
Tore

[SnakeDoc]

Hi Gentlemen,

Q.5 I am not sure if I understand your question right. If you mean the HP fuelpumps on the engines, the engine had to stop and a spare pump fitted, routine.

I believe, that Don is asking about auxiliary lubricating oil pump - but it is only used while taking fuel oil on board.

--
Regards
Maciek

[tore]

Don.
If you assume the aux. luboil pump should be used as Maciek says, I am afraid you got the fuel transfer system screwed up. All the fueltanks are as you know seawatercompensated except the F.O. regulating tanks. This means the F.O. bunkertanks are always under the head of the watercompensating tank high up in the towercasing ( not the wintergarden as you have mentioned) assuring the settlingtanks are having a supply pressure at the tank of 2- 3 m.W.C. This means that no fuelpump to transfer the fuel is necessary. The waterpressure derive from the attached cooling waterpump on the engines and the outlet to the headertank is at the exhaustmufflers in the casing. The headertank is always topped up in this way when the engines are running and normally you top up the engineroom settlingtanks when the engines are running. If you for some reason would like to transfer fuel from the FO tanks when the main engines are not running, you use the electric driven reserve coolingwater pump or even the handpump to keep the watercompensating headertank topped up giving sufficient head to the fueltransfer. As to the reserve fueloil regulating tank, you normally use air under low pressure for fueltransfer.
Tore

[SnakeDoc]

Tore,

I have rather general question about operation of diesel engines. From the basic experience with car engines I know, that
color of the fumes may indicate some problems with the diesel. For example white smoke can mean leak from the cooling
system and blue smoke - that engine burns the lubricating oil. The black fumes can indicate, that there is inadequate amount
of air to fuel combustion - or to much fuel - for example due to injectors failure.
Do the marine diesel engines behave in the same way? How about GW engines? What kind of problems influence the
color of the fumes? Did you experience some of them? Were there some repairs/adjustments possible while at sea?
I know, that this was not so important while snorkeling,  but when U-Boats cruised most the time on the surface, the machine
crews paid attention to the color of the fumes.

--
Thanks, regards
Maciek

[Don Prince]

Hello Mr. Tore,


In addition to Maciek's question about the diesel exhaust; did they purposely run a rich mixture while blowing the ballast tanks to provide a layer of un-burned diesel fuel as a means to protect the tank's lining from corrosion?


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Now I'm interested....


"Tore"
A.   shut to the settlingtanks and engines as shown on plate 9.
B.   the unusual, daytank shut and fuel goes straight to the fuel supplypump on the engines,
C.   topping up port settling tank and supply to the engine supplypumps from stb. settling tank and
D.   topping up stb settlingtank and supply to the engine supplypumps from port settling tank

The drawn position of e valve is shut (closed).  If it were rotated 90 degrees where the valve line/separator was not parallel with the tank, then we would have condition B; fuel going straight to the engines?

Now here is where I have a problem; does e valve have more than one activating lever/wheel, etc.? Something has to cause the diverting of the direction fuel can flow.  In the drawing where you are topping up the port side and drawing fuel from the stb side, how do you stop the fuel flow into the port side when the tank is full without affection the stb side fuel supply to the engines?

The one possibility I see is using the valve f ahead of the filter to the incoming fuel line. That way the one settling tank supply can be stopped without affecting the other settling tank that is providing fuel to the running engines...

Confused as usual...

Regards,
Don_

[tore]

Maciek and Don
 Running of the GW diesels. As both a car- and GW diesel generally are fourstroke engines, the combustion is pretty much the same. So the colours of the exhaust would be following the same rules. On a submarine however you have a wet sparkarrestor after the silencer which created some white watervapour pretty much like cooling waterleakage in a car engine. A bad atomizing of a fuelinjector or an overload,( lack of oxygen in relation to fuel) created a black exhaust. The exchange of fuel nozzles or HP fuelpumps is relatively simple on a large diesel and was a quick routine job at sea, spare fuelinjectors and pumps were always on board. Contrary to the car engine we checked the combustion in another way. Each cylinder has an indicatorcock e.g. a cock having a direct connection to the combustion chamber, every morning I personally checked the cylinders combustion by looking at the colour of the combustionjet on each and every cylinder. In this way an experienced eye could pick a cylinder not having an optimal combustion. If a further check would be required you could attach an manometer to the cock and check the combustionpressure before carrying out repair. This is a much more accurate check than looking at the exhaust. Black exhaust could be a problem when schnorcheling. Particularly when starting the engine as it was some residue water in the exhaustpipe. This water created a  backpressure in the exhaust pipe which could open the reliefvalve on the exhaustmanifold filling the engineroom with black exhaust, rather unpleasant.
Blowing the ballasttanks by exhaust. I know somewhere in the literature it is mentioned that an advantage of the exhaustblowing was rustprevention of the ballasttanks. We never paid attention to that, in fact the ballastanks were nice and clean painted with a yellow zinc chromate and very little corrosion.  Certainly we would not like to foul up the engine by running the engine with an incomplete combustion.
Tore

[tore]

Don.
I understand your confusion as the description of the selector cock is incomplete. The supply cock "f" is indeed used for topping up the system. The supply from the bunker fuel tank is much faster that the consumption of the engines so it goes relatively fast to top up the settlingtank and cock "f"cock is commonly the shut off cock for that operation.
A word on "closed" and "shut". In the RN submarine english the word closed is not used, in order to prevent misunderstandings for an important word, shut is generally used.
Tore

[tore]

Maciek.
Combustion check.
Perhaps I should mention that in addition to the checks I mention, the GW engines were equipped with individual exhaust thermometer for each cylinder which would register any unormal combustion as well. Proper monitoring of the combustion was important for many reasons and hence the surveillance was good.
Tore

[SnakeDoc]

Tore,

thank you for your answers.
When you started diesel engines after submerged cruise (that is when engines were cold) - did you run them for a some time with low load to get them warm gradually (except emergency of course)? I have met following figures: after start about 10 minutes KF, then 5 minutes LF, then 5 minutes HF and so on.

--
Thanks, regards
Maciek

[tore]

Maciek.
From an ideal point of view it would have been nice to run the engines as indicated by you. However when you surface you normally would like to obtain full buoyancy as quick as possible, particularly at heavy weather and swell. This because the metacentric height change from negative to positive when you break the surface and you are in an unstable situation. Hence you start the engine and run same at the load required for blowing the ballasttanks with a somewhat higher exhaust backpressure rather than an ideal warming up load. Otherwise normal surface cruising, starting with cold engines, we did not use the engine telegraph with strict speed commands, but communicated with the bridge verbally leaving the gradual increase in output to the desire of the engineer on watch, only to be overruled by the engine telegraph if the bridge had to.
Tore

[Don Prince]

Hello Mr. Tore and all,


My observations on Plate 8a (venting, sounding, test piping) are as follows:


1.  Maciek provided an excellent drawings on how to measure the remaining fuel in internal FO tank 1 and 2.  No questions...


2.  I don't see any means to measure the contents of fuel oil in any of the saddle tanks (D2, Regulating and RFO tank 1, and D4) in the Type VIIC.  I believe I seen a drawing from a Type XXIII that had a means to measure the external fuel tank contents.  Am I correct?


3.  D4 has the ability to drain fuel (from the top) into a collector bucket.  Why?


4.  D2 has the ability to drain fuel (from the top) into the FO Collecting tank. Why?


I have a question about the FO Collecting tank.  It looks like there is some type of a collecting valve that permits the input lines to feed the tank.  I assume it is manually or some how opened; it can't just be an open collector?  Otherwise, the measuring gage feeding the collector from D2 would be worthless because the collecting tank has a goose neck vent.


One question specifically for Mr. Tore -  When times were difficult and the captain needed to stretch his fuel oil supply, was the fuel oil in the FO Collecting tank re-cycled and used to power the engines?


Regards,
Don_

[tore]

Don.
Your no 2. question. measuring fuel from saddletanks. I think you have seen some drawings either from the IXC type or XXI. The system works as follows: a relatively small diam. pipe goes almost from the tankbottom to the top. A few cm. from the top is a 3 way selector cock which i believe can be operated from inside which either connect the pipe to the upper part of the tank or to the inside of the pressurehull via a hullvalve to a graded draincontainer. When measuring, you first put the selector cock to a equalizing position e.g. connected to the fluid on top of the tank and let the level stabilize in the small measuringpipe. Then the oil level in the pipe is at the same level as the tank. Then the cock is turned to a measuring position, the connection to the top of the tank is shut and the hullconnection is open. The inside cock is opened and the compensatingwater force the oil contents in the pipe into the measuring container.The hullcock is shut as soon as the compensating water starts to come. The the container has now an accurate oil level measurement of the saddletank which by tables can be transferred into oil volume. I have tried to make a sketch below.
3 and 4. You never squeeze the last drop of fuel into your fuelsystem, f.i when when you want to drain the external fuel/ballasttanks to convert same into just plain ballasttanks all the fuel on the top must be drained. You avoid letting the last drop go overboard and create an oilslick danger, thus you drain the last drops into contaminated oil collectingtanks and containers, not into the bilge.
The VIICs did not have a fuel separator or clarifier only gravity settlings and filters thus we did not use any contaminated fuel from the collecting tank.  We did not worry about environment in those days but the danger of being traced by an oilslick was allways in our heads and great care was taken to prevent fueloil contaminating the compensating watersystem and bilges.
Tore

[Don Prince]

Hello Mr. Tore,


Thank you for your response...


Q2.  I know how it works on the Type IX and XXI, but this is not available in the Type VIIC?


Question about the FO Collecting tank -  How is the collection valve controlled?  It looks like it has to have a shut state, otherwise the pressure measuring gage could not measure the fuel pressure?


Regards,
Don_

[tore]

Q 2. I cannot remember we had this system on the VIICs.
Fuel drain collecting tank pressuregauge. I am not sure I understand the question, I believe the the "valve" is a connection point on the top of the tank receiving the fuel drains by gravity and otherwise having no pressure. Could you explain which fuelpressure gauge you are referring to?
Tore 

[Don Prince]

Hello Mr. Tore,


On Plate 10 left side, there are two sampling pipes from D2 port and stb that connect to a collector (one above and one below).  There is also a measuring device going to the same collector with a valve.  All of this goes into the FO Collecting tank. 


In the other drawings of the FO Collecting from the top on Plate 9, there looks to be a circle with 4 inputs.  If that circle were just an open collection point in the FO Collecting tank, then the measuring device would never be functional because the FO Collecting tank has a goose neck to equalize the tank pressure with the internal hull pressure.


Is that some type of a valve in the FO Collecting tank with the 4 inputs?


Regards,
Don_

[tore]

Don
If I have understood you correct this time, I believe plate 10 shows the compensating water (green) entering the pressurehull via the normal hullvalve a, drains e and d as well as reliefvalve f. then to the inner fueltanks 1 and 2. Before entering the tanks each have a overpressure and underpressure reliefvalve which for tank no 1 has a drain via a funnel to the  (yellow pipe) fuel collecting tank in the engineroom. Se my sketch below.Tank 2 has a similar drain in the control room. Would that be it? I don`t believe it is a valve (or four) on the FO collectingtank.
Tore

[Don Prince]

Hello Mr. Tore,


I have marked 2 pipes as the A side and the B side on the drawing as follows:


1.  The B side looks to contain the pressure water from the Header Tank. 
2.  The A side has a collection funnel and drains directly into the FO Collecting tank. 
3.  The FO Collection tank has a goose neck vent to equalize the air pressure in the tank.


If this is the configuration, then I don't understand how the Measuring Container can ever collect anything.


If there is an over pressure event on the B side of the pipe and the over pressure relief valve opens, then the contents goes directly into the FO Collecting tank and nothing would get measured. 


Perhaps, I do not understand the function of the measuring device...


Can you enlighten this poor sole?  Do you have a photo of it?


Kind regards,
Don_

[tore]

Don.
I see you, have mixed up the compensatingsystem with the fuelsounding. There are three ways of measuring the fuelcontent in the bunkertanks. One for the inboardtanks 1i and 2i which Maciek has explained with his drawings. The pipings,containers,valves and cocks can be seen for 1i at the aft bulkhead in the control room and for 2i at the forward bulkhead, pretty much dominating selector cocks (valves). The samples are drained into  rather large containers which used to be removable, today they look like tackwelded into the support and shut by a lid. These containers, which were not marked, and contained fuel, should not be emptied into the bilge but carried and emptied into the measuring container in the engineroom shown on the sketch for the compensating system. After the measuring, the container is drained into the funnel and to the fueloil collector tank. It is hard to see the system on the available photos but I guess you can see the funnels behind some connectionboxes on port and starboard forward engineroom bulkhead.
The saddle fuel/ ballast tanks having checkpipes going almost to the top of the tanks were only checked for compensatingwater at the top and were drained for the F.O.BTKs 2 in the fuel collectingtank in the engineroom and F.O. BTKs 4 in a container in the controlroom.
The third way is that for the F.O. bunker/ regulatingtanks which have sigthglasses next to the sightglasses for the regulatingtanks in the aft end of the controlroom.
Tore

[Don Prince]

Hello Mr. Tore,


I apologize for asking so many dumb questions...  All I had to do was take a pause and think about the plumbing in my home to understand a little more about water pressure in pipes.  This is a different medium for me where I spent 46 years tracing electrical wires to components on a circuit board or schematic.


Now, I don't have a problem with venting, or sounding (measuring).  Thank you for your patients...


One question...  When a mission was completed, how was the fuel oil collecting tank emptied and cleaned out in preparation for the next mission?


Regards,
Don_

[tore]

Don.
Some times it is easy to get confused when different systems are interfearing, I remember ( some 60 odd years back) when I crawled all over the pipes of the VIICs to figure out how the piping worked with limited access to drawings. To know how at that time was a matter of life and death of 46 men. The VIICs have so many alternatives in the piping systems which some times was a challenge to use to its full extent. Emptying the fueloil collecting tank is one of them. It is a suctionpipe from the collectingtank to a system having hoseconnecting to a pump on shore as well as a valve connection to the suction of the handcooling waterpump which at the discharge side has a hoseconnection to wherever you want, see sketch below. As the discharge side of the handpump could end up in the galley or engine coolingwater system required a certain knowledge by the engineroom crew to prevent disaster or a furious cock on you neck.
Tore
 

[Don Prince]

Hello Mr. Tore,


I was wondering why contaminated oil was going to the galley...  Perhaps a chef's salad with a special oil and vinegar dressing???


Regards,
Don_

[tore]

Don.
The coolingwater handpump had many tasks, apart from a possible supply of dirty fueloil to the galley, a more serious task was to pump anticorrosive oil into the sea coolingwater system. As you can see it was a hose connection to the suctionside of the pump were you could connect a hose to a barrel of anticorrosive oil and a discharge via valve D1 to the cooling watersystem (Druckwasser). I am afraid the chef salad was non existent on a VIICs, in that case it would had to be made of seaweed and may be dirty fuel oil did not had to be mixed with vinegar to get the proper dressing for seaweed.
Tore

[VIC20]

Tore or Maciek do you have any data about knots at RPM when driving astern?

[VIC20]

Maciek, I guess this was yours? http://sourceforge.net/apps/trac/derleitendeing/wiki


What have you tried to achieve?

[tore]

Mark.
As far as I remember the GW and I presume MAN were converted into non reversible engines as from 1943. Thus the power for going astern was limited to E-motors. The direct reversible diesels I guess could give the same power astern as forward. The propellers would not give the same thrust astern though. I am sorry I have no figures, may be Maciek have some. Generally submarines were maneuvered by E-motors.
Tore 

[VIC20]

Thanks, I just want to add reversed diesels because it was possible (till 43)… (and subsim players are used to it)

[SnakeDoc]

Hi Mark,

Tore or Maciek do you have any data about knots at RPM when driving astern?

Unfortunately, I do not have any data about astern drive.

Maciek, I guess this was yours? http://sourceforge.net/apps/trac/derleitendeing/wiki


What have you tried to achieve?

Well, yes, I have started this project. In the first iteration I have tried to model U-Boat and its dynamics - especially when submerged. I have created (or rather implemented) algorithms for calculating centres of mass and centroids of the tanks (with any amount of water in them), then I have calculated the centroid and centre of mass of the whole vessel, which resulted in the moment of forces. I have also taken into account the rate of flooding and blowing of the tanks. This is was I have achieved. Finally, I wanted to give the operator the control of the whole vital installations of the boat, allowing him blowing particular tanks, shifting water between trim tanks, controlling compensating tanks and so on. All this would result in the position of the vessel in the water and her movements.
The project has been stalled, as I contacted with Captain Jerry Mason and have involved in the translation work. Now I'm doing wide research in the torpedo fire control systems - when I finish it, maybe I will go back to the derleitendeing - now my knowledge is far greater.

--
Regards
Maciek

[tore]

Maciek and Mark.
You certainly are going into quite a task Maciek and Mark if you are going to incorporate Macieks studies into the game it would be a very demanding play almost like the programmes which are used for training COs and EOs final course before being commissioned. The fruitmachines and similar firecontrol "computers" were very much the first stage of our to days computers without the semiconductor technique. We used rheostats, resistors and capacitors  requiring unbelievable space for a relative simple calculation.
Final question Mark I am just curious, what would you use the astern speed figures for?
Tore

[VIC20]

I need them to make the astern speed in the game more correct. Actually any known astern speed at a given RPM would help me to figure it out for all RPMs. Reversed propellers are totally different (hull in the way, propeller efficiency itself, drag when going backwards etc.) - even a rough guess would help me.


Interesting stuff Maciek, details like this won't make it into the first version of my game but I will try to implement it into the later main version which should be much more complex.

[tore]

Mark.
I believe we only used the astern thrust very shortly in following cases: 1. maneuvering alongside, 2.turning on the spot one propeller ahead, the other astern and for 3.emergency braking, in all cases the speed would be of less importance. In cases of diesel reversing, the timedelay, the time to shift camshaft etc., would probably be a more important factor than acceleration or retardation characteristics. A longer operation of going astern I would assume would not be likely and moreover the thrust bearing is only designed for running continuously ahead. Just a few thoughts on the subject as I can`t fully understand the need for the asternspeed.
Tore 

[Don Prince]

Hello Mr. Tore,


Things seem to be awfully quiet on the site, perhaps we need some more basic (dumb) questions to liven things up...


To start:


When I read about blowing the ballast most times the documentation only refers to Ballast tanks 1 through 5 and the negative buoyancy tanks.  However, there are two tanks that are not mentioned; the stern and bow buoyancy tanks.  I believe these tanks are open at the bottom with slits, and have a vent valve, and a low pressure air line. They are fully equipped do do the job quite well...


It would seem if there were an emergency dive situation that these tanks would get blown besides running all the un-needed crewmen to the bow of the U-Boat???


Please let me know when these tanks are used for something other than Longitudinal stability...


Regards,
Don_

[Don Prince]

Hello again Mr. Tore,


There are 2 lubricating oil tanks with a total capacity of 6.5 m3, and a dirty oil tank with a capacity of 0.79 m3.  Where does all that dirty lubricating oil go, certainly not in the much smaller tank?


Regards,
Don_

[tore]

Don.
The bow and stern buoyancytanks are not considered as ballasttanks, if you use the German words for the tanks it literally says watertight fo`csle and watertight stern. They are situated mainly above the normal surface line and the main purpose for the tanks are to dampen the longitudinal pitching of the vessel. They have as you say vents opened locally at the forward and aft torpedorooms. They are normally not taking part in the surfacing of the submarine.
Tore

[tore]

Don.
In addition to the tanks you are mentioning there are two  luboil system tanks, port and starboard. May be a short description of how the system works can be useful. Each engine has normally a closed luboilsystem where the system luboiltank (f.i. stb for stb engine) is intergrated. The no 1 and 2  luboiltanks are merely storagetanks. The dirtyluboil tank is pretty much like the fueloil collecting tank taking luboildrains and at the time oil purifier was installed, receiving the oil sludged from same. The tank can be emptied by a handpump on the port aft bulkhead in the engine room as well by a suction hose connection to a shore pump. The system oil tanks port and starboard can be emptied by the electrically driven reserve lub oil pump port fwd  in the engine room or by the a hose connection to pump ashore as well as by the luboil hand pump at stb. fwd. bulkhead in the engine room. Filling the systemtanks  from the luboilstorage tanks can be done by the same pump
Tore

[Don Prince]

Hello Mr. Tore,


I was reviewing information on a web site about starting marine diesel engines...


http://www.marinediesels.info/Basics/air_start_simple.htm


Did the GW and MAN engines have the basic components discussed here built onto the engines for air starting?


Regards,
Don_

[tore]

Don.
The airstarting of the GW engines and almost the same on the MAN was a bit different. Referring to plate 29 below : Each engine had a starting air flask topped up from the HP system. Each cylindercover had a starting air valve which in the starting sequence was engaged with starting cams on the camshaft by a pushrod. The valve had two airconnections, one at the top for pneumatically pushing the starting valve pushrod in contact with the camshafts starting cams. The other air connection is the startingair supply to the cylinder. The starting procedure is done by the starting handle on the maneuveringstand and the mainstarting supply valve having a handwheel ( painted red on U 995). The main starting supplyvalve is opened, starting handle is put in start position , air is admitted to the top of the cylinder startingvalve, pushing the valve rod against a springpressure down to the startingcam on the camshaft. One of the cams is always in a startingair lift(open) position thus admitting startingair to the cylinder and the engine starts to run on air, by the starting valves. As soon as the engine achieve satisfactorily revs you move the fuel handle and fuelrack of the fuelpumps,   admitting fuel to the cylinders and the engine starts to run on fuel. Then you put the starting handle to "neutral" the air on the top of the startingvalve is vented and the spring pushes the valverod up and disengage the connection to the camshaft. As plate 29 shows the system of the direct reversible engine, the real execution of the modified nonreversible execution is slightly different, but the idea is the same.

[VIC20]

Interesting stuff Maciek, details like this won't make it into the first version of my game but I will try to implement it into the later main version which should be much more complex.

Nonsense    It's much easier to do a lot of this now, at least the basic stuff.


Where can I find info how quickly the different tanks can be filled and how quickly they can be blown?

[tore]

Mark.
I cannot remember seen any such figures, may be Maciek have an idea. We were more concerned about f.i. diving time rather than surfacing time. Crash diving required a very well trained crew.   With normal preparation and a trained crew you could manage 30 seconds which is pretty fast compared to other similar submarines at that time. I Guess it could be contributed to the relatively large flowarea of the Kingstons plus the permanently submerged hydroplanes.
Tore

[VIC20]

OK, I might find a solution to calculate that the diameter of the vents is written on Uboatarchive,net…


Do you remember how much compressed air could be stored?

[VIC20]

Found it in the manual 

[tore]

Mark.
3.900 liters at 205 bar/cm2. You didn`t blow the tanks by HP air at depths greater than 14 meters normally only for emergency you are blowing tanks at greater depths. Hydroplanes and speed is a better way of changing the depth, better control and saving of air.
Tore

[VIC20]

But during an emergency situation you can only blow the main ballast tank below the command room right? The other MBTs would be destroyed at higher depths if they would be blown right?

[VIC20]

We were more concerned about f.i. diving time rather than surfacing time. Crash diving required a very well trained crew.   With normal preparation and a trained crew you could manage 30 seconds which is pretty fast compared to other similar submarines at that time.

My (hopefully not totally idiotic) calculation for the required time to flood the MBT below the command room (when no other tanks are flooded and the boat can still float on the surface) is something like 11.64 seconds
Do you think that could be OK?

[tore]

Mark.
Air blowing.
Emergency blowing is usually done by all the MBTks as it is the differential pressure which counts. As long as the tanks have free access to the sea and you are blowing keeping the differential pressure well below I believe o,6 bar, MBT 3 bar it is OK. As soon as the boat stop sinking and the boat start slowly to ascend, you stop blowing and the air start to expand in the tanks forcing out the remaining water out creating a fairly uncontrolled acceleration ascent which is not desirable except for emergencies.
The total air capacity of 205 bar is sufficient to to blow all the main ballast tanks and reserve fuel oiltanks totalling 155m3 at 40 meters and for the main ballasttanks only totalling 105 m3 at 65 meters. If you end up at 100 meters only 71 m3 can be blown, just to mention a few examples I found in the U boat info (1939) translated by Maciek.
Tore

[tore]

Mark.
Flooding MBT 3.
47,7 m3 including venting duct to be flooded in 11-12 seconds seems awfully fast, but with the large Kingstons I guess it could be possible. I never have been experiencing such a test. Both normal diving and particularly crashdiving was done in a more dynamic way using hydroplanes and speed in addition to ballasttanks.
Tore

[VIC20]

When I use the standard leak formula the result is that the 47 cubic metres of this tank could be theoretically flooded within 2.29 seconds (if the tank would be completely open on top instead of having 2 valves for the air to leave) when the "leak" of a comparable size is at a depth of 4 meters.


My calculation takes the leaving air through the 2 vents into account that's why it's much slower. But 10 seconds fits with some numbers I have read yesterday about flooding a MBT on a "Tauchboot" compared to real modern submarines which flood slightly slower.
Shouldn't the MBTs already have completely filled when you've reached pericope depth? I think the positive buoyancy would be too strong to go that deep that fast otherwise. But that's just my guess… 

[tore]

Mark.
I believe it is OK. Don`t forget it is not only the MBT 3 vent restrictions, but the fairly long airducts through the saddletanks as well. You would like to have the ballasttanks filled as quick as possible and certainly at periscope depth.
Tore

[Don Prince]

Hello Mr. Tore,


I have a question about grinding (burnishing) the exhaust flapper valve seat.  I have attached a photo from the uhistora web site.


Q1.  I assume this was dome to both exhaust valve seats?
Q2.  They state this was done every 4 to 6 hours?
Q3.  Item 4 in the photo - is this a lever/actuator to start the gringing process?
Q4.  Was there some type of electric motor connected to the shaft to rotate the flapper valve, or was it a motor connected by a machinist?
Q5.  The valve seat that was being burnished (remove carbon build-up) was it a type an lining similar to auto brake lining, metal to metal would not make a good water seal?


Regards,
Don_

[tore]

Don.
The group exhaustsystem consist of two flap valves, the inner which casing is shown on you photo and the outer being in a casing outside the pressure hull just before the silencer. Between these valves is a valve with the branch off to the exhaust blowsystem. The flapvalves have a valvedisc which can be rotated by means of a gearim on the disc which is connected to a wormgear. The inner flapvalve is operated by hand moving the rod seen on your photo, the outer is operated by a pneumatic motor which via rods and bevelgears rotates the wormgear on the outer flapvalve. The valve discs are rotated (in open state)once a watch to prevent carbon deposits on the rotating mechanism. When diving the valves are shut and rotated, thereby grinding the seatings which is conventional. If the valves were leaking we just waited till the water backpressure on the outer flapvalve was some 3-4 m wc giving a better pressure for the grinding. At depth greater the 5-6 m wc the resistance was too big for moving the disc. Between the two valves it is an ample drainage possibility to the bilge. I have tried to make some sketches of the system below.

[tore]

Don.
I believe something did go wrong with the first sketch so here is another try.
Tore

[Don Prince]

Hello Mr. Tore,


Since this was a manual job...  Was there a crank or a hand-wheel put on the shaft to grind the inner housing flap valve seat?


In your response...  What does "wc" stand for?


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


a second question...  The photo from the Spanish site; can you identify items 6, 7, and 8.  Unless my Spanish-English translation really failed me.  I don't believe these items have anything to do with turbocharged gases or the control room.  I believe these lines and valves are on Plate 13 in the engine room...


I posted a part of Plate 13 where these line and valves look to be...


Regards,
Don_

[tore]

Hello Mr. Tore,


Since this was a manual job...  Was there a crank or a hand-wheel put on the shaft to grind the inner housing flap valve seat?


In your response...  What does "wc" stand for?


Regards,
Don_

Don.
WC stands for watercolumn in this case the pressure on the valvedisc caused by the seawater by the distance to the surface. I cannot remember excactly how the wheel / handle was I guess more like a bar.
Tore

[tore]

Hello Mr. Tore,


a second question...  The photo from the Spanish site; can you identify items 6, 7, and 8.  Unless my Spanish-English translation really failed me.  I don't believe these items have anything to do with turbocharged gases or the control room.  I believe these lines and valves are on Plate 13 in the engine room...


I posted a part of Plate 13 where these line and valves look to be...


Regards,
Don_

Don.
 I guess a part of your post has disappeared.
Tore

[tore]

Don.
Referring to your Spanish photo it is not a simple answer because I believe the Spanish explanation is a bit confusing and incomplete. The group exhaust boardcasing consist of several cast steel parts all having watercooled jackets. As these parts are flanged together the coolingwater has to bypass these flanges. This is done by coolingwater bends which you see on the photo. However the coolingwater has to flow for each flanged part: in at the lowest point and out at the highest, which make the piping a bit complicated. In addition to the cooling waterflow you have the main drain from the exhaustspace between the outer and inner group exhaustvalves, further ventingpipes and greasepipe for the valves. I think you have to study the coolingwater plate 13 to follow the flow. I have previously made a sketch trying to explain the system which is posted below. The group exhaust valve watercooled casing is in fact the main engine coolingwater overboard "pipe" as well and as such designed for full max divingpressure.
Tore

[VIC20]

Tore,


In the german original version of the manual I've found the sentence:



"Die Regelzellen sind angeschlossen an die Fluteinrichtung in der Zentrale…"


which means:


"The regulating tanks are connected to the flood installation in the command room"


But the english translation says:
"The regulating tanks are connected to the drainage installation in control room"


…in the description of the Torpedo compensating tanks Maciek used "drainage installation" for the word "Lenzleitung" which is correct (and the opposite of a "Fluteinrichtung")


Now when looking further into all the info about the different tanks I can't find out any info about how some of the tanks will be flooded (I mean where is the flood vent, where do they take the water from) - is it possible that there is such a flood installation with a common flood vent for the incoming water for these tanks?

- regulating tanks
- regulating reserve fuel oil tanks (when used as regulating tanks)
- Trim tanks (or do the trim tanks use a kind of closed system with a fixed amount of water to pump it around?)


Another question:
The torpedo compensating tanks… in the german version of the manual they write "Die Torpedozellen nehmen das Wasser für den Gewichtsausgleich der Torpedos und Minen sowie das Umhüllungswasser auf" - Maciek forgot to translate the word "Umhüllungswasser" in the english version: "The torpedo compensating tanks are flooded to compensate for the weight of a launched torpedo or mine." - this word is pretty tricky to translate it's like "surrounding water", I guess they mean the water used when flooding the torpedo tubes?


And one more question, how much time does it takes to blow the tanks with the diesel?
Rössler wrote in "U-Boottyp XXI" that it takes 2 minutes to blow the torpedo tubes with air (0.6 atm) - then blowing tanks with the diesel should take a lot of time right?

[tore]

Mark. I am not very conversant with the torpedosystem, I never interfered with the torpedo people. We have the same word "Umhullung" in Norwegian and I guess your assumption is correct, you flood the torpedotube, launch the torpedo, the surrounding water is ejected and you compensate for the totalweight torpedo plus surrounding water.
Exhaustblowing of the ballast tanks always seemed to me to take a long time. I Guess I never recorded the time and it varied depending upon trim, exhaustpressure adjusted by the outer flapvalve,weather and how much the ballasttank were blown by air etc.
Tore

[tore]

Mark.
Take a look at plate6 and you shall have a good understanding of the compensating, trim and regulating system. As you say most of the control of this system is situated in the controlroom. It is a very flexible system having its own seawaterconnection with volumecounter in the CR aft stb. Via a number of pipeconnection chests you can flood the tanks directly, or by connection to the bilge (Lenz) pumps. The regulating tanks (and Q tanks) have an inboard venting ending in a muffler down at the bilge, you can see the system with sightglasses clearly on the photos showing the aft part of the attack periscope casing in the aft controlroom. The use of drain in connection with the system is a bit confusing at least for the Europeans. In naval english we use more bilge and bilgepump (Lenzing) rather than drain, as we use drain in the meaning "tapfen".
The trimsystem is a bit different from the regulatingsystem as this is more like a pitching compensating rather than buoyancy compensating as done by the regulating tanks. thus you move the same water from fwd to aft or opposite. Although you have connections so you can adjust the amount of water you can play with.
Tore

[tore]

Mark.
Regulating tank flooding/filling. draining/ empytying.
Below is a a drawing of the floodinginstallation with connection to the various systems.
Tore

[VIC20]

Thank you! Could you give an estimation in minutes how long it took to blow the tanks with the diesel?

[tore]

Mark.
Exhaust gasblowing.
As I said the time could vary depending upon how much the tanks were emptied by air, the weather (sea), trim etc. Lets assume the exhaust pressure at the control panel in the controlroom is O,5 bar and the airblown tanks have placed the boat having casingdeck slightly above the sealevel, calm sea and a good trimlevel, thus ideal condition. My guess would be some 10-15 minutes. I never recorded the time so this is pure guesstimate from my side. In a difficult situation or very bad weather you always could sacrifice some HP air to shorten the time subject to the COs judgement.
Tore

[VIC20]

great, that helps a lot 

[VIC20]

Tore, do you know what diameter the lines of the compressed air blowing installation to the tanks had (or the inlet openings for that in the tanks itself? Or was that somehow connected to the air vents of the tank?)… I need that information to calculate the time necessary for blowing tanks at a given depth.


The pressure of the air in the air flasks was 200-205 atm - how long could you keep the pressure at 25 atm in the blowing installation? The flasks were at different positions how were they depleted, one by one or all together?


It took about 4 1/2 hours to completely refuel the compressed air flasks, is that correct?

[tore]

Mark.
Ref. plate 17. The Hp air system consist of 12 HP flasks each two flasks connected into a bank thus 6 banks. Bank 1 outside pressurehull, both sides of aft ext. torpedocontainer. Bank 2 .outside pressure hull appr. above the main engines. Bank 3 inside pressurehull both side of PO mess. Bank 4 inside pressure hull port side fwd. torp. room. Bank 5 inside pressurehull stb. side forwd torp room. Bank 6 outside pressurehull one flask inside bow buoyancy tank the other stb. side torp container.
The banks are connected to a distribution panel in the controlroom and then to the various blowing distr. panels as can be seen on plate 17.
The blowing pipes to the ballasttanks are going from the blowingpanels to a NR valve and a hullvalve directly into the tank, not via ventingpipes, see photo below. I don`t have the diameter of the blow line but if you look at the photo I should make a guesstimate of 20-25 mm.
I believe each HP flask has a volume of 325 liters and the E- compressor has a capacity of 6.1 liter/min at 205 kg/cm2, the Junker compressor has a capacity of 8.5 liter/ min at 205 kg/cm2, which should make it possible for you to calculate the time for recharging the air. You could keep the pressure at 25 kg/cm2 as long as your HP flasks had a pressure exceeding that.
Tore

[VIC20]

Thanks, maybe one day when I visit U 995 I'll measure it 

[tore]

Mark.
Give her love and kisses from me.
Tore

[SnakeDoc]

Hi Gentlemen,

I have not been here for a some time, so I'll try to answer for some questions in one post.

Interesting stuff Maciek, details like this won't make it into the first version of my game but I will try to implement it into the later main version which should be much more complex.

Nonsense    It's much easier to do a lot of this now, at least the basic stuff.


Where can I find info how quickly the different tanks can be filled and how quickly they can be blown?

We were more concerned about f.i. diving time rather than surfacing time. Crash diving required a very well trained crew.   With normal preparation and a trained crew you could manage 30 seconds which is pretty fast compared to other similar submarines at that time.

My (hopefully not totally idiotic) calculation for the required time to flood the MBT below the command room (when no other tanks are flooded and the boat can still float on the surface) is something like 11.64 seconds
Do you think that could be OK?

When I use the standard leak formula the result is that the 47 cubic metres of this tank could be theoretically flooded within 2.29 seconds (if the tank would be completely open on top instead of having 2 valves for the air to leave) when the "leak" of a comparable size is at a depth of 4 meters.


My calculation takes the leaving air through the 2 vents into account that's why it's much slower. But 10 seconds fits with some numbers I have read yesterday about flooding a MBT on a "Tauchboot" compared to real modern submarines which flood slightly slower.
Shouldn't the MBTs already have completely filled when you've reached pericope depth? I think the positive buoyancy would be too strong to go that deep that fast otherwise. But that's just my guess… 

I have also used some standard formulas for a leak into the tank with opened top. As a result I had about 10 seconds for flooding all three main ballast tanks. Taking into the consideration the diameter of the vent ducts, I think it fits into the practical times of achieving periscope depth.

In the german original version of the manual I've found the sentence:


"Die Regelzellen sind angeschlossen an die Fluteinrichtung in der Zentrale…"


which means:


"The regulating tanks are connected to the flood installation in the command room"


But the english translation says:
"The regulating tanks are connected to the drainage installation in control room"

…in the description of the Torpedo compensating tanks Maciek used "drainage installation" for the word "Lenzleitung" which is correct (and the opposite of a "Fluteinrichtung")

Literally translation of the word Fluteinrichtung is flood installation as you said. I have translated it as drainage installation, because in other parts of manual, this system is called either Flut- und Lenzeinrichtung or (more common) Lenzeinrichtung and I tried to keep consistency. This Flut- und Lenzeinrichtung was used to drain bilges and tanks or to flooding regulating tanks, as Tore explained.

As Tore said, the British English term is rather bilge system or bilge pump rather than (as in American) drain/drainage system. You can easily see this difference while reading British report  and ONI report on HMS Graph (or American reports on type IXC and XXI U-Boats). I used rather American naval terms.

The torpedo compensating tanks… in the german version of the manual they write "Die Torpedozellen nehmen das Wasser für den Gewichtsausgleich der Torpedos und Minen sowie das Umhüllungswasser auf" - Maciek forgot to translate the word "Umhüllungswasser" in the english version: "The torpedo compensating tanks are flooded to compensate for the weight of a launched torpedo or mine." - this word is pretty tricky to translate it's like "surrounding water", I guess they mean the water used when flooding the torpedo tubes?

Right you are, my mistake.

Have you seen my document on torpedo tubes?
http://www.ubootwaffe.pl/en/u-boats/equipment/torpedo-tubes-of-german-u-boats

Tore, do you know what diameter the lines of the compressed air blowing installation to the tanks had (or the inlet openings for that in the tanks itself? Or was that somehow connected to the air vents of the tank?)… I need that information to calculate the time necessary for blowing tanks at a given depth

The inner and outer diameter of blowing lines are 17 and 20 mm respectively.


--
Regards
Maciek

[VIC20]

Have you seen my document on torpedo tubes?
http://www.ubootwaffe.pl/en/u-boats/equipment/torpedo-tubes-of-german-u-boats

…

The inner and outer diameter of blowing lines are 17 and 20 mm respectively.

Yes I stumbled upon it yesterday.


Wow, where do you found this information about the diameter?


I'm trying a new calculation for the tanks now based on a paper from 2011 about computer controlled ballast tanks for non dynamic diving (from reading this paper it seems that they haven't introduced this at least till 2011 on submarines).

[VIC20]

At 25 atm (and 20°C) the mass flow of air into one tank should be 1.41145831051 kg per second 

[Don Prince]

Hello Mr. Tore,


I have a book "Type VII U-Boat" and it stated the electric air compressor was primarily used while submerged.  That statement looks to be uninformed to me!  First it is noisy and would help the enemy to locate the U-Boat, and would drain the battery.  Just where is the electric air compressor going to get its air supply to compress - from the pressure hull?  And who lives in the pressure hull - People who can be affected by no air and high negative pressure.


What do you think?


Regards,
Don_

[SnakeDoc]

Don,

I have a book "Type VII U-Boat" and it stated the electric air compressor was primarily used while submerged.  That statement looks to be uninformed to me!  First it is noisy and would help the enemy to locate the U-Boat, and would drain the battery.  Just where is the electric air compressor going to get its air supply to compress - from the pressure hull?  And who lives in the pressure hull - People who can be affected by no air and high negative pressure.

In some cases E-compressor was used while submerged:

Excess pressure of more than 40 mb is to be pumped off with the electric
compressor, if possible, to prevent carrying away acid when opening the
conning tower hatch.

Tauchvorschrift, paragraph 202

--
Regards
Maciek

[VIC20]

Hello Mr. Tore,


I have a book "Type VII U-Boat" and it stated the electric air compressor was primarily used while submerged.  That statement looks to be uninformed to me!  First it is noisy and would help the enemy to locate the U-Boat, and would drain the battery.  Just where is the electric air compressor going to get its air supply to compress - from the pressure hull?  And who lives in the pressure hull - People who can be affected by no air and high negative pressure.


What do you think?


Regards,
Don_

no idea but my thoughts are:


1. I think the air of the quick diving tank is always released into the pressure hull, so they could compress at least 6.51 cubic meter without reducing the pressure inside the boat below standard atmospheric pressure. Not much but this would be worth 6.5 tons of weight close to the surface.


2. At an altitude of 2000 meters (which is still OK for humans) the atmospheric pressure is 77% of sea level (783.8 hPa) so for the crew itself it would be safe to reduce the pressure to that amount.
The air inside the boat is 391 cubic meter hence 89.93 cubic meters could be compressed which is 449 liters at 200 atm (the total amount of compressed air in the flasks is about 3900 liters at 200 atm)


3. at greater depths the pressure in the boat should increase due to the slightly pressed hull another light amount of air would be available to compress.


I could only imagine that they would do it in case of emergency when laying on the bottom at a great depth with damage to all saddle tanks and in case that the pumps can not overcome the water pressure (no idea how they perform at lets say 200m) - but maybe they could somehow attach the electric compressor directly to the 25 atm blowing system to speed things up?? This device should have more than enough power to do that.


But I guess the stress on the hull would increase with less air in the boat…


…and you would need to put all that air into the boat again before you could open the conning tower hatch


And of course I have no idea and talking nonsense   

[Don Prince]

But I would not think this was the primary electric air compressor mode for operation; submerged?  This mode of operation would never replenish the air in all those tanks.  This had to be done while surfaced (I think)!!!


Regards,
Don_


PS


Does anybody have a photo of both Toggle Switch Switchboards (Port and Starboard) of the older style U-Boats?  I'm having some issues determining how the circuitry works with only half the picture (Port side only in the manual).  There seems to be a difference in switches according to the circuitry in the manual, but I want to be sure and not guess. 

[VIC20]

Maciek there is another mistake in the manual (possibly at a lot of places):


On page 40 you've translated it to "The highest pressure in the installation is 25 atm"
Correct would be "The highest pressure in the installation is 26 atm" (and for the diesel 1.5 atm)
They've wrote 25 atü - atü is "Atmosphere Überdruck" which means "atmosphere overpressure" and is:


X atü = X atm + 1 atm (or more correct at instead of atm)


You will instantly understand why when you look at the 0.5 atü (1.5 at) pressure used to blow out tanks with the diesel. The 0.5 atm from the english manual would be below the atmospheric pressure and it would not be possible to blow out a tank with that, actually it would do the opposite and work like a drinking straw.
The water pressure at a depth of 5 meters is about 0.5 atm but 1 atm of the atmosphere has to be added which is 1.5 atm hence you can blow out the tanks with the diesel up to 5 meters (depth of the bottom of the tank) which perfectly fits to MBT3 which bottom is approx. 80 cm above the keel at a draft of the boat of 4.74m so it is about 4m below the water surface. So when the tank is empty you still have an overpressure in the tank of approx. 0.1 bar.

[VIC20]

But I would not think this was the primary electric air compressor mode for operation; submerged?  This mode of operation would never replenish the air in all those tanks.  This had to be done while surfaced (I think)!!!

Yes sure. But it seems they could use it at least to compress some air while being submerged (if that makes any sense at all is a different thing)

[tore]

 Don and everybody.
The E- compressor was used when submerged and not schnorchling mainly to get rid of the overpressure in the boat which always built up. The overpressure started to build up as soon as the tower hatch was shut as the pneumatic motors for the grinding of the group exhaustvalves in the engine room were operated. Depending upon the leakages you could use a awful lot of air and you could get a substantial overpressure. Inboard venting and small leakages contributed as well. If we had time we were running the E-compressor prior to surfacing to to prevent a rapid pressure fall when the tower hatch was opened. Many gauges were influenced by the higher ( and lower) airpressure  f.i. some of the depthgauges and at last but not least the cooks preparation for the meals were highly influenced as higher pressure increased the boiling temperatures. Yes people on board a submarine got to learn the practise of the thermodynamics and particularly the Boyle-Mariottes Law. 
Tore

[VIC20]

I've read in "the death of the uboats" that at least one commander died when opening the hatch after (I think emergency) surfacing, he was blown out of the boat like a rocket.

[tore]

Mark.
True, we always had a man with a firm grip on the COs legs in those cases we had to surface without pressure equalizing. And Mark, running the E compressor at 200m would be a bit risky. The E-compressor was depending upon a seacooling system consisting of inter stagecoolers, water jackets, pumps and valves. we never operated or opened the seavalves at great depths as blowing a gasket or getting a crack at depths like 100 m would be troublesome.
Tore

[VIC20]

But what if you would lay on the ground at 200m and the boat has negative buoyancy (or dead engines) for some reason? Is the situation then die or blow and die?

[tore]

Don.
In desperate situations you try anything, and improvise. When I studied submarine technique a class ahead of me disappeared with the loss of HMS Affray. I remember the old Commander E`s wise words as the tabloid press screamed about building a multimillion submarine escape tank: why don`t use the money to improve the crews skill to run a submarine rather than how to escape or handle impossible situations.
Tore

[SnakeDoc]

Hi Gentlemen,

But I would not think this was the primary electric air compressor mode for operation; submerged?  This mode of operation would never replenish the air in all those tanks.  This had to be done while surfaced (I think)!!!

Well, generally you are right. First of all, in the book "Type VII U-Boat" are some errors. The sentence saying about usage the compressor while submerged has sense only in the context explained above, or can be treated as another author's mistake.

Maciek there is another mistake in the manual (possibly at a lot of places):


On page 40 you've translated it to "The highest pressure in the installation is 25 atm"
Correct would be "The highest pressure in the installation is 26 atm" (and for the diesel 1.5 atm)
They've wrote 25 atü - atü is "Atmosphere Überdruck" which means "atmosphere overpressure" and is:

Mark, you are right. I had seen the difference while translating the text, and even had a discussion with Jerry, how
to handle designation of units (in English there is no simple corresponding term for atü unit). And finally, this matter
was forgotten.
I will correct errors you have spotted.

I've read in "the death of the uboats" that at least one commander died when opening the hatch after (I think emergency) surfacing, he was blown out of the boat like a rocket.

Here is interesting discussion on this topic:
http://uboat.net/forums/read.php?20,62642,62699#msg-62699

The E-compressor was depending upon a seacooling system consisting of inter stagecoolers, water jackets, pumps and valves. we never operated or opened the seavalves at great depths as blowing a gasket or getting a crack at depths like 100 m would be troublesome.

That's interesting notice indeed, Tore. I have checked, that cooling system of E-Verdichter was tested up to 15 atü.

--
Regards
Maciek

[tore]

Maciek.
Testpressures and deep diving.
It was common, anyhow in my peacetime, not to go deep ,say down to 100m, without shutting off for deepdiving (and depthcharging), meaning boardvalves and branchvalves to systems not absolutely necessary. Air compressor was not considered being absolutely nessesary at these depths when we are talking about routine dives. In emergency situations you always evaluate all options to be taken, balancing risks against benefits. Laying stuck at 200m I guess is one of the situations where "the devil eats flies"you try everything.
Tore

[VIC20]

Maciek,


I think something is wrong with your translation of the main drain pump:


"The drain performance by // and -- mode are similar up to depth of 57 meters.  At greater depth the performance by // mode decreases strongly.  It is practical to switch to the - - mode at a depth of 50 meters.  During trials, by connecting the auxiliary trim and drain pump (358 liters/minute) in parallel, drain performance at depths greater than 50 meters is increased by 40%."


Correct would be something like this:


"The performance of // and -- mode will cross on the graph at a depth of 57 meters. At greater depth the performance decreases strongly when operating in // mode. In practice you should switch to the -- mode at a depth of 50 meters. By the hook-up of the auxiliary trim and drain pump (358 liters/minute) in serial to the suction and pressure lines of the main drain pump, the drain performance at depths greater than 50 meters was increased during trials by 40%"


But it's possible that I just don't understand it all all 
Anyway "Praktisch ist ab … überzugehen" is clearly a directive.

[SnakeDoc]

Hi Mark,

"The drain performance by // and -- mode are similar up to depth of 57 meters.  At greater depth the performance by // mode decreases strongly.  It is practical to switch to the - - mode at a depth of 50 meters.  During trials, by connecting the auxiliary trim and drain pump (358 liters/minute) in parallel, drain performance at depths greater than 50 meters is increased by 40%."


Correct would be something like this:


"The performance of // and -- mode will cross on the graph at a depth of 57 meters. At greater depth the performance decreases strongly when operating in // mode. In practice you should switch to the -- mode at a depth of 50 meters. By the hook-up of the auxiliary trim and drain pump (358 liters/minute) in serial to the suction and pressure lines of the main drain pump, the drain performance at depths greater than 50 meters was increased during trials by 40%"


But it's possible that I just don't understand it all all 
Anyway "Praktisch ist ab … überzugehen" is clearly a directive.

Right you are, these pumps should be connected in serial.

--
Thanks, regards
Maciek

[VIC20]

great - helping to find mistakes is fun

[VIC20]

Tore, this simple formula is from scientific paper about submarines - you can estimate the reduction of buoyancy caused by the outside pressure compressing the hull:


B0 = buoyancy due to vehicle displacement at zero depth
B = current buoyancy due to vehicle displacement at a given depth
Z = depth


B = B0*(1 - ((0.015 / 300) * Z))     (I always use more brackets than necessary  )


So at a depth of 200 meters the buoyancy is reduced by approximately 1% (8.65 tons)


What have you done to compensate that? That's almost 18.5% of the volume of MBT3. Was the lift force of dynamic diving still enough? (I haven't calculated the dynamic forces yet)

[SnakeDoc]

Tore, this simple formula is from scientific paper about submarines - you can estimate the reduction of buoyancy caused by the outside pressure compressing the hull:


B0 = buoyancy due to vehicle displacement at zero depth
B = current buoyancy due to vehicle displacement at a given depth
Z = depth


B = B0*(1 - ((0.015 / 300) * Z))     (I always use more brackets than necessary  )


So at a depth of 200 meters the buoyancy is reduced by approximately 1% (8.65 tons)


What have you done to compensate that? That's almost 18.5% of the volume of MBT3. Was the lift force of dynamic diving still enough? (I haven't calculated the dynamic forces yet)

Mark, in Tauchvorschrift is the following paragraph (no 181):

Because the boat loses volume at greater depth, it must be made lighter by timely pumping (for type VII boats approximately 1 ton per 100 meters).  It is appropriate to pump out a greater amount, because the boat will be heavier by the accumulating leak water anyway.

http://uboatarchive.net/DivingRegulations.htm

Compensating buoyancy reduced by 2 tons (at 200 meters) could be easily done by means of regulating tanks (of total capacity 24,6 ton).

--
Regards
Maciek

[Don Prince]

Hello Mr. Tore,


Is there a master switch for the battery compartments in the Galley and the Officers sleep area?  Do you have any photos?


Did the battery compartments have any type of warning system about pressure or chlorine gas sensors? Was there any means of exhausting the chlorine gas while submerged?


Regards,
Don_

[tore]

Don.
I don`t have any photos of the automatic batteryswitches they were placed in special small rooms as indicated on the below sketch. The batteries and battery compartments were checked twice a day taking acidgravety and water topping. Looking at plate 18 you should be able to figure out the battery ventilation system which did not have any possibility to get rid of the chlorinegases while submerged except rising the schnorchel. However we had a lime installation as can be seen on plate 26. As to automatic chlorine warningsystem I can`t remember we had anything like that.
Tore

[Don Prince]

Thank you Mr. Tore for the information regarding my question about the batteries...


Today, I am just about finished working on the circuit schematic for the Rotary Switchboard.  However, I'm just not completely sure about  the Field 1 and 2 hand-wheel in the center.  I believe these wheels are independent and move separately and the normal Low speed for the outer speed hand-wheel is to the left (see attached photo LOW/Niedrig is to the left).  The photos I have from U-995 shows the wheels in the center and to the right.  I guess museum traffic and people turning the Hand=wheels makes for my confusion because I don't believe they are in the shutdown position.


Does anyone have information about the smaller hand-wheel that is used to select Field 1 or Field 2 on the speed controller?  Where is the normal shutdown, not active position?


Regards,
Don_

[tore]

Mark.
Submarine displacement at great depth.
When you use formulas like you found involving displacement figures, depth and hullcompression you have to be aware of that the submerged displacements figures is a bit different to a surface ship. At great depth the compression of the pressure hull (displacement) is the only component which is influenced by the submergepressure. The steel, wood and other solid meterial like the superstructure,  is not significantly influenced by the waterpressure at 200 meter. Thus the diminishing of the displacement is only that of the internal volume of the submarine which you could estimated to 450-500 m3. Your 865 tonnes (1 % 8.65) is based on the totalt weight of the submarine.
Tore

[VIC20]

Thanks Tore, calculating it with 450 tons is still more than twice as much as the historical documents says (2.25 tons per 100m instead of 1 ton). In this case I trust the older data.

[VIC20]

Tore and Maciek, I'm still not certain how large (effective) the air & water openings really where - I wonder if the numbers on uboatarchive take grille into account.


Could you open the kingstons or the air outlet venting valves partially? Or were they all like flaps only?


(still have no idea how a kingston really works)


BTW:
I've made a miniature "MBT" of a water bottle and recalculated openings so that the volume and openings fit to MBT3 - did that just to get a totally rough idea how fast this thing could really fill. …sure pressure difference is different and several other effects so it's worthless but it gives at least some really rough idea. This thing filled up pretty fast - 12-13 seconds (and the lowest depth is just the depth of the bottle) - If someone wants to have some fun with water: necessary holes are (I think) like 7.6 * 7.6 mm and 2.2 * 2.2 mm for a 1 liter bottle 

[SnakeDoc]

Hi Mark,

Tore and Maciek, I'm still not certain how large (effective) the air & water openings really where - I wonder if the numbers on uboatarchive take grille into account.

I have no other numbers than these on the uboatarchive.net. The MBT 3 as well as RFO&MBT 2 and 4 have no grille. MBT 1 and 5 have rather flood slots than grille.

Could you open the kingstons or the air outlet venting valves partially? Or were they all like flaps only?

The flood valves were normally opened while at sea, so you don't need consider them partially open.
The vents construction is visible on this plate:
http://uboatarchive.net/U-570Plate28.htm
I think, that only vents of MBT 1 and MBT 5 could be consider partially opened.

--
Regards
Maciek

[tore]

Mark.
Further to Macieks remarks. The Kingstons working is based on the travelling nut principle. For MBT 3 the threaded valve spindles are supported in two location- and turningbearings, the spindle ending through a pressure stuffingbox in a square end in the CR where a removable crank turned the valvespindle. On the spindle is a travelling nut fixed to a yoke moving the Kingston outwards as indicated on my sketch below. You could in fact open it in any position but as Maciek says it was normally not done. The saddletank Kingstons are operated in the same way as can be seen on plate 28 but open inwards. The MBT 3, 2 and 4 vents were directly operated by handle and rod movements and are either shut or fully open as can be seen on plate 28. All the moving parts inside and outside the pressurehull have grease connections.

[VIC20]

tanks err thanks 

[VIC20]

Tore, I think you mentioned the "jet effect" somewhere in this thread. How does that work?
When the tank if full of air and the boat raises the water pressure sinks so air will leave the tank through the flood port, is it just the power of the leaving air that makes such a huge difference when surfacing?

[tore]

Mark.
I should probably mention that it is only the forward double Kingstons on MBT3 which is operated by a yoke as seen on my photo below.
Tore

[tore]

Mark.
It is a combination of air forcing the water out of the ballasttanks at an increased speed as the air expands due to falling ambient pressure rather than anything else. However an increasing jet of water out of the Kingstons (and floodgates) is created as well. I emphasize this is absolutely not the way of surfacing, It is a waste of air and partly an uncontrolled surfacing but of course it could be a show off.
Tore

[VIC20]

Thanks, I've added the jet effect. 

[tore]

Mark.
Watergauge regulating tanks, f.o. reg. tanks.
Below is an image of same ,stb. aft controlroom, same on port side.
Tore

[tore]

Mark.
Regulating tanks reduction of volume.
Below is a red mark off showing the MBT3 airduct  passing the regulating tanks.
Tore

[VIC20]

Tore,


The 4 main ballast and reserve fuel tanks 2 & 4 stb & bb… could those operated together only? In other words: were they like a single tank split into 4 tanks sharing a single vent?
And if so, what about their kingstons? http://www.uboatarchive.net/U-570Plate28.htm shows a cross section area of flow of 3.167 m2, this is much larger than for all other tank so I guess it's for all 4 tanks together and the kingstons were opened together only?



Edit: 2 & 4 shared a vent via a duct on each side between Spant 41 & 42 - hence the pressure of air in both tanks was always equal…

[VIC20]

…when looking at your model of the Kaura I see 6 Kingstons for MBT3 and 4 on each of MBT 2 & 4. The Kingstons look almost identical from their size. I think the 3.167 m2 cross section area of flow are for each of the pairs 2 & 4 (6.334 total for MBT 2 & 4 stb & bb together)

[VIC20]

The Type VII manual shows the distance to the center of mass for all of the tanks. But the center of mass is not static, it can move - what position (horizontally) should I use for placing the tanks based on the information of the manual? (I've tried to estimate geometrical position of the center of mass (of the tanks itself) for each tank before, but this is extremely intuitive and just a rough guess)

[tore]

Mark.
The venting of the MBT 3, 2 and 4 port and stb is arranged as seen on the sketch below. 2 and 4 port and stb are opened simultaneously. MBT3 port and stb likewise.Thus you may say they are operated as one tank, however each tank venting can be shut off by a valve next to the tank in case of a possible damage to the venting duct.  I believe the flood area indicated on plate 28 is the total. If you calculate the tank volumes in relation to the floodareas you get for the MBT 3 total volume 47,7 m3/ floodarea apr. 2,76 m2 = 17,28. For the saddle ballasttanks 2 and 4 total volume 49,6 m3/ floodarea 3,167m2= 15,66. Be aware the MBT 2 port and stb has a venting in the aft end for residual venting. When diving or surfacing at an angle you shall have difference in pressure in the ballasttanks as they are at different depth.
Tore

[VIC20]

OK, then I'll keep them as 4 different tanks because of the pressure calculation and because each tank venting to the duct could be shut off.

[tore]

Mark.
The tanks distances from the mass center.
I am not sure I understand your question properly. Do you want to have a pitch calculation based on each tank onboard, not only ballast tanks, like a calculation for the total trim at a given situation as a leakagecalculation for compensating in the event of a leakage (damage) flooding of a compartment? In that case I am afraid it would require a lot of calculations with many variables.
Tore

[VIC20]

My ballast tank calculation already has about 1500 lines of code.    When I feed it with the correct data then I get the current trim & pitch of the boat "automatically", it recalculates the waterline, remaining air and the evolution of pressure in each tank 50 times per second based on the depth of each tank and the areas of the flood openings and air vents. (and a lot of more necessary things) My calculation script is based on a scientific paper about computer controlled ballast tanks for submarines. The resulting forces act on the boat in a similar way like the calculated buoyant forces due to displacement of water do (the boat is split into parts and I calculate buoyancy for each of those parts separately) - these forces (and thrust of the propellers, the lift of rudders and diving planes at their positions and also all forces due to different drag in all directions and rotations) act on the center of gravity of the boat causing a torque and acceleration.
What I need is the correct position of the tanks itself. (the position of their own center of mass on the horizontal axis when completely filled - during the calculation I only move the tanks center of mass on the vertical axis, I don't take the actual shape of the tanks into account because that's almost impossible)


I could add any tank if I want to but currently I want to use only those:
MBT 1-5
watertight stern and bow
regulating tank 1 & 2
regulating cell 1 & 2
trim cell 1 & 2
negative buoyancy 1 & 2
torpedo compensating tanks fore and aft


For example the manual says the MBT3 is located 2,10 meters in front of the center of mass of the boat - for me that sounds like they are talking about the center (of mass) of MBT3 - what I need to know is the position of the center of mass of the boat used for calculating those positions of the tanks in the manual (it's not clear because the boat could be trimmed etc.) - once I have the "correct" positions then the amount of errors should be as small as possible and I could start creating a virtual "lt. commander Tore"    and train him to trim the boat (when the positions of the tanks are too different then it will be harder for my virtual Tore to do his job or in worst case the volume of the trim tanks could be too low to compensate the wrong positions of the tanks). Sure this all won't be 100% correct but it is closer to the real thing than any other submarine simulation game and it works "automagically" without fakes.

[tore]

Mark.
Impressive! Belonging to a generation which was depending upon smell,noise,feeling and experience rather than anything else such computercalculations is really an Utopia. I am afraid we had a far less sophisticated way of doing things and I see your need for inputs. Sitting with my late Saturday drink I guess I shall wait till tommorrow before I shall see if can be of any help at all. Computergames are definitely not my speciality. 
Tore

[VIC20]

I think it's still utopia or experimental because the paper is from 2011 and they wrote that today when dynamic diving in shallow waters is not possibly (for example in missions to bring in divers close to a target or whatever it could be) they still need the person who does the job based on his experience and mostly on an intuitive feeling only.
But maybe some rough computer control for the tanks is common today? I have no idea but I can't imagine it's not.

[tore]

Mark
Reading the manual, it seems to me the figures given are for a standard of contents of all  tanks (stated in the manual) and two MBTconditions A all MBT empty  giving the submarine a reserve buoyancy of 155 m3. and B MBT 1,3, and 5 empty and MBT/FO tanks 2 and 4 port and stb full with dieseloil giving the submarine a reserve buoyancy of 155-49,6= appr. 105 m3. The pitch calculations are based on these two conditions using the pitch moments based on the various MBTs calculated mass centers distance from the submarines calculated mass center without giving the specific location of the center. I don`t believe you shall find any accurate calculated location of the submarine masscenter`in the manual as this book is meant as a manual for the people on board using a fairly rough calculation as usual for the 1940- 1945 technology. Sorry for not being able to give a better help.
Tore

[VIC20]

Well, then I use the geometric center (on the horizontal axis) - at least on the surface it seems that this also is the center of gravity (otherwise the boat would not lay in the water like it does) - submerged the position of the conning tower might change that.


Do you have a detailed picture of a kingston? Or of the venting valves? I want to know how open these things really are when opened. (if I can use the whole area in the calculation).


My boat still dives extremely fast. But maybe that's correct and I just have to add the human factor? I know there is a description on the diving procedure on uboatarchive, but could you please tell me an estimation how much time the necessary tasks took? (open vents and kingstons for example - in my simulation they they can be just open or shut, maybe I should add the necessary times for opening to the calculation (even if it's just 0.5 seconds) with a growing flooding and venting area while opening. Any information with estimated times is useful - like estimations how long from the order to dive till the first vent is open (based on a perfect crew at their best performance), how much time till the next one will be opened (really at the same time?)
The "diving procedure" on uboatarchive http://www.uboatarchive.net/KTBNotesDiving.htm says the tanks were flooded while the crew was still preparing the bridge for diving but my calculated uboat sinks that fast that the hatch of the conning tower reaches the water surface after 11 seconds (after vents opened).


Also the "diving procedure" does not mention MBT1 at all, what about MBT1 when was it flooded?

[tore]

Mark.
The best Pictures of the Kingstons and vent to my mind are those on plate 28. As can seen they give a good opening with a fairly low restriction. Thus I think you can use the full floodarea may be - 5 to 6%. As you know there are normally two ways of diving. The conventional way and the wartime crashdiving the latter require a well trained crew. Conventional dive is the most common. The boat is in a E-motor mode and presumed MBT 2 and 4 port and stb in ballast mode. Upon the command dive,dive,dive! the vents for MBT 5, 3, 4,2 and residue venting 2 are opened. 2,4 and 3 vents are very quickly fully opened by a swift pull down of the ventlevers in the control room.  5 and residueventing 2 take a bit longer time may be 4-5 seconds as they have to be turned open. After some 5-6 Seconds the vent for MBT 1 is opened taking again some 4-5 Seconds. The boat should now have a bow down angle about 5-8 degrees, ideal: tower windeflector should pass the watersurface simultaneously with the stern. This manoeuvre is carried out in order to prevent the propellers and rudder to brake the surface. However at an angle exceeding 8 degrees you get a substantial difference in pressure between forward and aft MBTs. and it gives a crazy feeling to see from the controlroom the large engines  hanging "high" up in the aft end.
The crash diving is an emergency maneuvering and can be risky, thus requires a fairly high degree of training. You have several crash dive procedures, while surface cruising on diesels,  having gunnery people at the bowgun, surfacing, charging batteries, exhaustblowing of tanks to mention some, they all had to be exercised.
You reading about people preparing the bridge after the diving command could be a misunderstanding. The CO. shut the top hatch soonest possible after the dive command. A possible situation could be the early war situation while carry out sinking by gunnery and a sudden air attack. I don`t know the procedure for that situation, we never had a casing gun.
Hopefully this might give you an impression and a possible time estimation of the diving time bearing in mind that a use of Q and increase of speed would improve the matter.
Tore

[SnakeDoc]

Hi Gentlemen,

The Type VII manual shows the distance to the center of mass for all of the tanks. But the center of mass is not static, it can move - what position (horizontally) should I use for placing the tanks based on the information of the manual? (I've tried to estimate geometrical position of the center of mass (of the tanks itself) for each tank before, but this is extremely intuitive and just a rough guess)

Mark, when I was working on Der Leitende Ingenieur project, I developed the algorithm to calculate the geometrical center of the tank (of any shape, described as set of polygons). I could assume any level of water in this tank and calculate the center of mass. Then I planed to create a 3d model of the U-Boat, which would consist of all tanks, whose shape, volume and localization would be restored as closely to the real as possible. Then I would be able to calculate moments of force for each tank (for any water level in the tank) and then for the whole boat.

Do you have a detailed picture of a kingston? Or of the venting valves? I want to know how open these things really are when opened. (if I can use the whole area in the calculation).

Try to look for the U99 photos in the dry dock.

Also the "diving procedure" does not mention MBT1 at all, what about MBT1 when was it flooded?

The MBT1 is mentioned in the paragraph 9 of the diving procedure.

You will find more details here: http://uboatarchive.net/DivingRegulations.htm
(section VII and XII)

--
Regards
Maciek

[VIC20]

Thanks Tore & Maciek, I finally found time to read the http://uboatarchive.net/DivingRegulations.htm (slowly) again yesterday. The other page on uboatarchive is misleading, Jerry should take a look on that.


Simulating the real shape of the tanks would require too much calculations per second which is bad for the overall performance and will heat up the devices and drain the battery. I could add this to the later desktop versions. But I think it might be pretty hard to find the correct shape from the available drawings.





I don't understood how the regulating tanks and cells are operated since I've read that:

As soon as it is possible, [i.e. when the regulating and reserve fuel oil tanks have been converted for use as regulating tanks] two regulating tanks are to be cross connected ready to flood and two regulating tanks ready to pump, namely one about half-full under 3 to 4 at as a shallow pumping regulating tank, the other approximately 2/3 full under 10 to 12 at as a deep pumping regulating tank.  Boats with only two regulating tanks operate one as a flooding regulating tank, the other as a deep pumping regulating tank.

When they are filled differently (only 2 in use) they would create a torque. This makes no sense for me.

[SnakeDoc]

Hi,

Simulating the real shape of the tanks would require too much calculations per second which is bad for the overall performance and will heat up the devices and drain the battery. I could add this to the later desktop versions. But I think it might be pretty hard to find the correct shape from the available drawings.

Well, you are right - the overall performance is important factor when developing on mobile devices.
I'm optimistic about modeling the shape of the tanks from the drawings - with help of the guys from this forum it should be doable

I don't understood how the regulating tanks and cells are operated since I've read that:

As soon as it is possible, [i.e. when the regulating and reserve fuel oil tanks have been converted for use as regulating tanks] two regulating tanks are to be cross connected ready to flood and two regulating tanks ready to pump, namely one about half-full under 3 to 4 at as a shallow pumping regulating tank, the other approximately 2/3 full under 10 to 12 at as a deep pumping regulating tank.  Boats with only two regulating tanks operate one as a flooding regulating tank, the other as a deep pumping regulating tank.

When they are filled differently (only 2 in use) they would create a torque. This makes no sense for me.

The regulating tanks are located near the boat center of gravity not without the reason - the moment of force is small due to short arm (0,1 m for regulating tank 2 and 3 meters for regulating tank 1) and small weight (up to 8 tons for regulating tank 2 and 5 tons for regulating tank 1) - consider the torpedo tube - distance from center of mass ~25 meters and weight ~1,5 ton.

--
Regards
Maciek

[VIC20]

I thought more of the problem on the roll-axis when only 2 reglers can be used.

[Don Prince]

Hello Mr. Tore,


I really like your Presentation Plaque and the model of the Kaura (ex - U995).  That is a unique lifetime achievement.  I ran the name KAURA through several web based translators and all I get is KAURA = KAURA.  Is KAURA a woman's name. like the passenger liner Queen Elizabeth II?


For about 6 months, I have been working on a book for my own personal use on the Type VIIC U-Boat based on the Skizzenbuck plates from Captain Jerry Mason's web site (uboatarchive.net), and addition expert information and advice from Maciek and Mr. Tore.


I'm about 3/4 done with about 272 pages (mostly drawings and explanation of systems).  At this point, I am having problems with the on-board Port Welding circuits in relation to the general Rotary Switchboard circuits presented in a Preliminary training manual.  The circuits and components don't match up in the drawings. 


Do you know of any source for the Blade or Rotary Switchboard schematic?  If I had access to either one, then I would have an excellent chance of understanding the electrical circuits of the other?


Regards,
Don_

[VIC20]

I'm confused:The watertight stern & bow are located pretty high, it looks like they are just slightly touching the surface with their bottoms under normal conditions so they should take water only in rough seas but the vents are shut then. The only difference it makes in good weather to keep them open is that they are always ready for diving.
Now I think I use the wrong draught. Could someone please make a drawing of the height of the waterline (at different trim conditions)?

[tore]

Don.
The name Kaura is a lighthouse on the rugged long coast of Norway. Our 3 VIICs were called the K class after the WW2 and named:KNM  Kaura, KNM Kya and KNM Kinn all named after lighthouses at the Norwegian coast.
You electric question, about a year ago I found amongst a bunch of old paper a complete electric scheme from I guess KNM Kaura or Kya. these schemes I posted on this thread as from page 100 and 101. Have a look back and see if they are of any use.
Tore

[tore]

Mark.
The watertight bow and stern are indeed above the waterline and are not a part of the submerged system, they are used to reduce the pitching in rough surface weather by improving the buoyancy when the stern and bow "take a dip" in into the waves thereby improving the life for the poor buggars at the bridge. We normally kept the vents shut at the surface and it was a routine to check same open at divingpreparations. I cannot remember the draughts at various trims, there are draught marks on the hull, may be Maciek can help.
Tore

[Don Prince]

Hello Mr. Tore,


This looks to be a general wiring schematic of U-101 a Type VIIB U-Boat.  I have never seen a general wiring schematic for a U-Boat, and most likely never again (very unique)!  This will not fill in all the blanks, but it does provide a good base to piece each system into place when ever I can find them.  The schematic list U-101 and Blohm & Voss, but U-101 was built by Fried. Krupp - Germaniawerft, Kiel...  Interesting?


Do you have any idea as to the cost to copy your schematic?  If it were not overly expensive, then I would be willing to reimburse you for your cost, time, and mailing expenses for a copy.  They usually put blue prints in a mailing tube for shipment...


Regards,
Don_

[VIC20]

Do you have any idea as to the cost to copy your schematic?  If it were not overly expensive, then I would be willing to reimburse you for your cost, time, and mailing expenses for a copy.  They usually put blue prints in a mailing tube for shipment...

I would say a good high resolution scan in a copy shop would be the best solution for this - I guess that's cheaper than mailing and you could share it with dropbox or other free cloud providers.

[tore]

Don.
The drawing is pretty shot and is about 5 feet long in a roll, but I shall consult one of my grandsons who are more conversant in the present days possibilities of restoring. I believe Mark`s suggestion could be an alternative. I don`t believe it is a VIIB schematic, if you look at the title of the drawing it is stamped U 101 and a black square covering the last figure. Blohm & Voss had a contract for building a series of VIIC/41 which were listed as 1010 up to 1019 of which U 1013 up to U 1015 and U 1017-U 1018 were suspended U 1011 and U 1012 were damaged at the yard beyond repair by an airraid July 1943, U 1016 was scuttled somewhere in the Baltic I believe, but U 1019 surrendered in Trondheim Norway may 9Th.1945. I am inclined to believe the drawings were "borrowed" by the Norwegian prior to handing over U 1019 for the deadligth operation.
As I obviously has taken the drawings home for studying, some of my scribblings are on it,  while being EO on the Kaura ex U 995 I would assume they are from the B&V VIIC/41 series used at that time by me for our only VIIC/41 KNM Kaura.
Tore

[Don Prince]

Hello Mr. Tore,


I figured it was a fairly large schematic....  In 1966, I went to the NCR Company Technical Training Center in Dayton, Ohio, to get trained on the Class 450 proof machine.  The 450 was a 20 total mechanical Accounting machine with an OCR printer for encoding the amount on the bottom of a check  It also had a 20 pocket check sorter and a 20 receipt printer module unit.  This was a electro-mechanical monster that failed many of the older mechanical service engineers.  I was previously trained on the Class 390 computer system in 1963, so this was a piece of cake for me.  It had cam switches timed to enabled wired relay logic to enable other cam switches to energize solenoids to engage mechanical functions.  The schematic was 5 x 10 feet and I remember taping it to the wall at night to study the circuits.  The next day we had to demonstrate the schematic circuits section to the instructor's satisfaction!


In January 1963, I was an apprentice new hire with 9 months field experience.  When I was trained on the computer system, every Friday morning there was a "You Bet Your Job Test."  If you scored less than 90%, then you were fired that afternoon!  Our class size was 22 students and 12 months later when I completed the class our number was 11 souls.  Those were the good old days...


Regards,
Don_

[VIC20]

Tore, from the manual:

For blowing regulating tanks, regulating and reserve fuel oil tanks, and negative buoyancy tanks a blowing manifold is provided in the control room.  The safety valves for regulating tanks and regulating and reserve fuel oil tanks are set at 13 at and for negative buoyancy tanks at 10 at.  Each regulating tank has a pressure differential gauge installed.

That means you can't blow the regulating tanks & cells at depths deeper than 130m right? Only pumping should work then.
Which pressure differential are the gauges showing?

[tore]

Mark.
Not everything is mentioned in manuals, when you are in trouble  the system is open for alternatives, if f.i. you have a lot of water in the bilges I would pump this in a non pressurized regulating tank using the mainbilge pump in parallel, filling the regulating tank. Then pressurize the regulatingtank at fi. 12 ata, put the main bilge pump in series for suctions from the regulating tank, having a suctionpressure say 110 mwc, boost that up with the pump if needed to say another 105 mwc having a capacity of 500 l/min (diff pressure  105 mwc) against total 215 mwc. overboard, hoping the pump, pipe, valve and valve stuffingbox can take it. Same goes of course if you like to pump out water already in the regulating tank. May be a VIIC/41 can survive such depth, possibly not a VIIC, anyhow this is just to give you some fantasies which may be could be built into a game ( and real life) giving the innovative players a chance to survive.
Tore

[VIC20]

Ah… nice! You assist the pump with pressure from the tank. Where exactly is the exit to outboard for the pump located?

[tore]

Mark.
I was carried away a bit , I guess the official rules are: the static pressure (difference between inlet and outlet) of the main bilge pump  should not exceed 8 atu appr. 80mwc. you could pressurize the regulatingtanks up to 14 ata (app.130mwc.) you can exceed that if you pressurize the adjacent tanks ( Q ,reg-and f.o.bunkertks1) somewhat to reduce the bulkheadstresses, say 3-4 ata.That should give you a better pumpcapacity at 210 m.
Tore

[tore]

Mark.
The connections to the sea are shown on the sketch below. Note it is an outlet to Mbt 3. as well.
Tore

[VIC20]

So you could pump to MBT3 instead and try to blow it out with hp air?

[tore]

Mark.
Remember when you are submerged the Kingstons are open and MBT 3 has the ambient sea pressure. So why MBT 3 at all? Well let assume you are pumping the oily bilges and do not want to pump it overboard because you are laying deep hiding and an oilslick is betraying you . You pump it in MBT3 and let it sit there till you blow the MBT3 for surfacing in safer water later.
Tore

[Don Prince]

Hello Mr. Tore,


I have been reviewing back post and I learned that the steam heating system is only used when in port.  That fact makes me feel a lot better because I could not find a heating source on the steam heating Plate...  However, that brings some questions to mind.


1.  When the U-Boat is running on the surface in the North Atlantic at winter time, Is the heat source the diesel engines and using the ventilation system to distribute the heat?


2.  When the U-Boat is running off the coast of Spain, or even worse yet in the Mediterranean, at late summer, doesn't it get kind a HOT!  What do you do to get cool?  I believe the water if pretty warm as well; will diving help at all?


#.  If the U-Boat is sitting on the bottom, say at 150 meters Off the coast of Norway, Isn't it really cold down there?  You can't just throw another log on the fire...?  What do you do to keep warm?


Regards,
Don_

[tore]

Don.
The diesel engines did not take part in the compartment heating and most of the heat dissipation went overboard, in fact sometimes it could be a bit chilly at the maneuveringstand as a huge amount of cold air was drawn in via the dieselair duct. The heating was primarily electric. I cannot remember it was excessively hot in the summertime, this was the time before airconditioning was common and allthough I remember on board surfaceships it could be hot in the Mediterranean most of the submarine was submerged all the time and the sea temperature was some 20-22 degrees C. However people 46 men, electric motors, galley, battery charging etc gives heat dissipation and the only way we could get rid of that was by running the ventilation system taking air from outside, if the air was warm it would not help a lot. 
The sea temperatures along the Norwegian coast varies a lot and particularly in the deep fjords. Offshore the Golfstream keep an average almost constant temperature and the water never excessively cold, in the fjords it varies with the seasons. Particularly in the spring when you have melting of snow and ice creating layers of coldwater with less salinity and making it difficult to keep and good trim. However the layers gave an excellent active sonar protection as the layer were acting like a reflection mirror. Today the have transmitters at different levels screening the layers horizontally. I had most of my service on board patrolling in the Barents sea but I cannot remember it was very cold.
Tore

[SnakeDoc]

Don,
as Tore said, the heating was primarily electric. The steam heating installation was fitted (I believe) in the early-war U-Boats and abandoned in the end of war. U995 was not equipped with such system.
The steam heaters are visible on these two photos from U570 (below the hatch):


The electric heaters were portable devices, which were plugged to the U-Boat electric net.
One of them you can see on this photo from U570 torpedo room:

I have attached also two more photos of electric and steam heaters.
As far as I know, type IX U-Boats had the same heating installations as type VII.
But type XB mine-layers were fitted with steam heating system, which consisted of steam generators, whose utilized the heat from the exhaust gases.
--
Regards
Maciek

[SnakeDoc]

Ah… nice! You assist the pump with pressure from the tank. Where exactly is the exit to outboard for the pump located?

I have attached two photos of the port and starboard side of the boat.
On port there is visible only one hole for inlet/outlet, on the starboard - two.
I have also attached sketch made by Tore, where I marked with blue line one more opening (water inlet).
I suppose, that the "blue one" is the inlet on the starboard side, while the other inlet and outlet - on the port side.


--
Regards
Maciek

[tore]

Maciek.
Right you are Maciek, I forgot that one.
Tore

[VIC20]

great, thanks Tore and Maciek

[VIC20]

Tore, at Trim A (no oil in MBTs)…


how much water was usually the trim cells when surfaced and when submerging?
Currently in my simulation it looks like there should be at least water in the aft trim cell to trim the boat when submerged.



…and how much water was in the regulating cells for the torpedoes at the beginning? (if no torpedo was used) does it carry water for the flooding of the tubes? or where the tubes already flooded?

[Don Prince]

Thanks Mr, Tore and Maciek...


Hi Maciek,


Since they were using electric space heaters to keep warm in cold weather, does that mean at least one e-motor was running as a generator to keep the batteries topped?


Regards,
Don_

[tore]

Don.
Charging batteries was normally not depending upon the electric consumption, the condition of the batteries was the ruling factor. Twice a day the battery cells were checked for voltage, acid specific weight and temperatures. Normally we started charging when the values dropped below a limit. If however if circumstances were such that  fully charged batteries would be required, this was overruling the ideal charging.
A constant top charging would increase the risk for "gassing" eg. producing explosive hydrogengasses as well as batteries becoming "tardy". In order to keep the batteries in top shape we "drained" the batteries to the bottom once a month by running the E-motors alongside and starting charging immediately when the batteries were drained.
Tore

[tore]

Mark.
Trimming tanks.
I don`t remember we had any specific rules how much and sorry I can`t remember the forward and aft draugth. The procedure was to take a rough calculation then  balancing dive to check the calculation and sometimes it could be wrong. Then by the regulating tanks ( we never used same as f.oil bunkertanks) find an optimal trim and by adjusting the trimtanks say half full or less. The exact amount of regulatingwater would vary almost all the time depending upon consumptions as fuel, provision, freshwater etc. As the moment arm for the pitch was very long you needed only to move small amount of water to compensate for the trim f.i, as I have mentioned before, when diving station was ordered the movement of people from the 3 watch system to divingstation would require 400 liters to be pumped (yes we pumped) from aft to forward.
I leave your torpedo questions to Maciek he is more conversant with this topic than me.
Tore

[Don Prince]

Hello Mr. Tore,


I have a question about a blower vent...  I have drawn a rendition of the vent that might work.  However, the way they have drawn it on Plate 19, it looks like one blower will feed the other one and very little air would go out the vents???


Am I all wrong headed again?


Regards,
Don_

[tore]

Don.
I believe you have misunderstood the selectorsymbol. As you know on the VIICs , not equipped with schnorchel, you have two ventilation airducts one for intake the other exhaust, both operated from the controlroom and having airducts outside the pressurehull to the engineroom where they enter the pressurehull via a hullvalve with drain. I have made a sketch below showing the system green is intake and yellow exhaust. The ventilation situation you are referring to is both ventilatorfans operating in parallel which mean they have common inlet suction ( green) and exhaust (yellow). The fan selectorvalve select the suction from a number of alternatives and consist of two valves a circular selector slidevalve and a hull inletvalve.Likewise the exhaust selector slidevalve has a number of alternative positions as well as a hull exhaustvalve in one unit. If you study the sketches and photo I guess you shall have a better understanding. Remember there are many other valves in the ventilatingsystem which should be operated to get the alternative required not just the slide selectorvalve.
tore

[SnakeDoc]

Hi Gentlemen,

…and how much water was in the regulating cells for the torpedoes at the beginning? (if no torpedo was used) does it carry water for the flooding of the tubes? or where the tubes already flooded?

Well, from my studies of this topic (as no descriptions or manuals are available) I think, that torpedo compensating tanks (Torpedozelle) initially contained amount of water sufficient to flood tubes with torpedoes within them (that is about 370 litres per tube, that means that Torpedozelle 1 - aft - contained 370 litres of total 2350 litres volume and Torpedozelle 2 and 3 contained 740 litres of total 5750 litres each).
I think, that tubes were flooded from compensating tanks because in such case, the weight of boat did not change, and the trim changed only slightly.
When the torpedo was launched, the tube was fully flooded with overboard water (through the muzzle door). After closing the muzzle door, the tube was drained to the torpedo compensating tank (1680 litres of water).

Torpedozellen were also used as the aid to trim the boat, when some of the torpedoes were disposed.

And small interesting fact - aft torpedo compensating tank and one of forward compensating tanks could be used as storage tanks for wash water - they were fitted with piping to the wash water installation.
In middle period of war, forward tank was also used as fuel oil storage tank - to extend the operational range of the boat.
The U458 KTB says, that when the boat stayed in Saint Nazaire between first and second patrol (that means between 27 August - 1 October 1942), one forward torpedo compensating tank was modified to storage fuel. The additional 5,75 m³ of fuel extended patrol by two days (at 10 knots, both diesels 275 RPM).

--
Regards
Maciek

[tore]

Mark
Re Maciek post on torpedoinstallation.
It is astonishing to see how the germans used all opportunities to extend the patrols only by a few days. I made a calculation on having both fuel oil bunker and regulating tanks 1  filled with fuel, both tanks together would extend the running of the two diesels at max continuous load by some 20 hours. Otherwise thanks to Maciek I learned something new about the alternative use of the torpedo installation. I have mentioned previously our contribution to alternative use, ejecting garbage through the torpedo tubes on very long submerged schnorchling patrols. This happened to much dismay from the torpedopeople.
Tore

[VIC20]

Thanks again… btw Tore it would be interesting to see an example how you calculated things aboard. I guess you had rules of thumb to speed things up?

[tore]

Mark.
Contrary to the Germans, our EO. task was not involving trim calculations, that was No.1`s job, so I don`t remember exactly. We used as you say rule of the thumb in addition to tables and graphs I would believe, not much calculation. A testdive was the most important thing, that would reveal any mistakes and could be corrected by experience. But in order to prevent too much excitement you should be somewhat close to the correct figures. I must confess however we sometimes had excitement.
Tore

[VIC20]

Thanks Tore, I still have some question about the flooding & drainage installation:
- The water inlet, I guess it worked with the natural water pressure and you don't need the pump at all to flood the regulating tanks right?
- Is the diameter of the (water) pipes of the flooding & drainage installation identical to the ones used to blow out the tanks with compressed air?

[Don Prince]

Hello Mr. Tore,


On Plate 18 - There are 3 Air Conditioning Units on the intake / suction lines...  Were those just evaporation units? They simply ran water across a filter and interior air was then drawn through the filter.  The water evaporation and chilled the air and it was then distributed throughout the U-Boat....  Although, that would increase the humidity, so I'm not sure about the evap unit???


I seen the evap units used in many locations in the High Desert State of Arizona where my brother lives.  It is very dry and arid, so evap units work.  However, if the humidity gets above 35 percent, then evap units don't work so well...

A/C back in the 40's and 50's were quite large and required Freon gas....


Also, My DVD/CD of U-995 does not seem to have good photos of the hand-wheel with the Slide Selector lever above it.  Do you have some good photos?  There are 2 units, one for the Port blower and one for the Starboard blower correct?


Regards.
Don_

[SnakeDoc]

Don,

On Plate 18 - There are 3 Air Conditioning Units on the intake / suction lines...  Were those just evaporation units? They simply ran water across a filter and interior air was then drawn through the filter.  The water evaporation and chilled the air and it was then distributed throughout the U-Boat....  Although, that would increase the humidity, so I'm not sure about the evap unit???

The translation is quite misleading - these three units are the carbon dioxide absorbents. The units in the control room and forward torpedo room are visible on these photos:




--
Regards
Maciek

[Don Prince]

Thanks Maciek,


A/C didn't sound right, but it was spelled out on Plate 18: Air Conditioning Unit... So, these would come into use when the U-Boat is submerged and they are re-circulating the air inside the pressure hull???


Regards,
Don_

[SnakeDoc]

That's right, Don.


--
Regards
Maciek

[tore]

Thanks Tore, I still have some question about the flooding & drainage installation:
- The water inlet, I guess it worked with the natural water pressure and you don't need the pump at all to flood the regulating tanks right?
- Is the diameter of the (water) pipes of the flooding & drainage installation identical to the ones used to blow out the tanks with compressed air?

Mark.
Surfaced, the filling of the regulatingtanks could be done by natural seawater pressure only up to the draugthline of the submarine, submerged of course all the way. I Guess the fine floodline to the distribution chest has a smaller diameter than the other pipes and as you use the latter lines for moving the water being pumped or blown I migth have misunderstood the last part of your question.
Tore

[tore]

Thanks Maciek,


A/C didn't sound right, but it was spelled out on Plate 18: Air Conditioning Unit... So, these would come into use when the U-Boat is submerged and they are recirculating the air inside the pressure hull???


Regards,
Don_

Don.
In addition to Macieks answer. The CO2 absorbent canisters fitted in ventilation system were a kind of old fashioned scrubbers filled with soda lime granules as reactors. They produced heat and had a non reversible chemical reaction thus a limited lifetime and was only used at a prolonged submersible situations. The procedure at long dives without schnorchling was every man not absolutely needed goes to bed using as little air as possible. The after say some 24-30 hours it became uncomfortable as the CO2 became excessively high and you connected the "scrubbers". The excessive CO2 created a heavy panting and when the "scrubbers" worked the situation became better, then after a while you got problem with the  reduced oxygen and had to connect the oxygen flasks to the ventilation system.
Anyhow contrarily to today, the system was in use only very seldom, I believe in my time we used it once or twice a year. We did not use any sophisticated systems for monitoring the air quality, only experience.
Tore

[tore]

Don.
Ventilation shaft hullvalve and selector slide.
Below is the best photo I have, showing the ventilation hullvalve and selector slide in one housing.
Tore