Tores mailbox VIIC and VIIC/41 operation and technical details

[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