Tores mailbox VIIC and VIIC/41 operation and technical details

[Don Prince]

Hello Mr. Tore,

I went through a major upgrade to Skizzenbuch as suggested:
1.  I removed all references to the D designation for the Ballast tanks on both text and photos.
2.  The word Dive Tank was replaced with Ballast Tank
3.  The word Dive Plane/s was replaced with Hydroplane/s
4.  The word ventilation valve was replaced with vent valve
5.  The word flood valve for MBT 2, 3, and 4 was replaced with Kingston/s

I corrected page 199, 261, and 262 = Attack and not attach
I added periscope info on page 260
I added warm wash and shower water info on page 247
I added fuel consumption info on page 401

Mr Tore, I am very grateful for your suggestions about cleaning up all the inconsistencies...  If you see any other problems, them please adivse.

Regards,
Don_

[tore]

Don.
Checked your correction OK. A few remarks on page 401. The accurate outputs of the engine are measured on the testbed by having a waterbrake attached, the braking is done according to the propellerlaw. The output measured is the brake horse power BHP, not break.
I do not fully under stand the figures stated in you column: Mid war diesel engine reversing gear was removed. It is of course correct that the reversing gear was removed, but that does not influence the ahead output/rpm range of the engine which is the same as on the testbed graph. It might look as if you possibly show the outputs of the engines without a superharger, but the supercharger was not removed with the reversing system.
 On the direct reversible engines it was not possible to run astern with supercharger clutched in, it could be that you are showing these diesel astern figures.
In that case I suggest you call the column Astern figures for direct reversible dieselengines to prevent confusion, otherwise use the figures in the VIIC manual page 14, A ship info. I General.
Tore

[tore]

Don.
Skizzenbuch. Page 402 contains a short description of the thrustbearing, 403 a more elaborate description of same do you want both? Page 404 shaft break......- shaft brake.....Page 405 charging mode, you can run both engines in charging mode simultaneously as well. Page 406 ...the large red handwheel and the black starboard handwheel...... I believe on the museums U-995 they took fun in painting levers, handles and wheels, red for port equipment and green, not black, for starboard. Looks sometimes almost black on the photos though. Not very important in my time we did`t use these fancy colours. The propeller clutches are named differently, like Main clutch,E-motor clutch , Propeller clutch. The RN expression is Tail clutch, I personally like Propeller clutch. Anyhow as mentioned before, only one name for the thing would be preferable. Skizzenbuch checked OK up to page 410.
Tore 

[Don Prince]

Hello Mr. Tore,


If running on the surface and charging with both diesel engines, would that be considered a lighter charging mode?  If one diesel engine is dedicated to charging the batteries, then would that be considered a full charging mode?


If charging with both diesel engines while schnorcheling, they still have the 6 knots speed restriction; correct?


Regards,
Don_

[tore]

Don.
Charging with both diesels could be anything, low speed, high charge or high speed, low charge depending upon the requirement. The advantage is to have the same propellerload  on both propellers which mean you do not have to compensate an uneven load on the propellers by the rudders. Whether or not you have a full charging mode depend on the state of the batteries, what charge you can put into the batteries, you have to reduced the charging at the last part of the charge to prevent gassing and not to shorten the lifetime of your batteries.
6 knots restriction has nothing to do with the mode of charging it is merely a restriction due to the bending forces created on the schnorchelmast.
Tore

[Don Prince]

Hello Mr. Tore and Maciek,

I made all the suggested corrections and the one in the Naxos section.  After thinking about Mr. Tore's comments about running both diesels engines and their e-motors as generators...  I was thinking and changed page 405.  I know me thinking is dangerous, but an I correct, or all messed up again? 

I uploaded the latest version of Skizzenbuch to dropbox for your review.  It looks like we are getting to the 400's pages and almost done...

Then I have to re-configure Skizzenbuch's pages for Schiffer, and I'm going to re-configure Skizzenbuch for my leather covered post binder.  I going to change the page layout so I don't need to worry about the binder spacing.

Regards,
Don_

[tore]

Don.
Skizzenbuch page 405. I believe it is OK and I don`t think you should elaborate this further as it could be a bit complicated. Instead of  making a long list of various configurations may be a general description is easier. As previously mentioned the engine performance graph is registered on the testbed waterbrake according to the propeller law. That is an ideal theoretical condition for an optimal propeller, which is useful for estimating vital engine figures. If you put a charge on top of the propeller load you upset the ideal load ( propeller load) and the engine performance both with regards to fuelconsumption and the max. load. I have made a new graph in our testbed scheme showing the max output and an assumed charging load graph (blue) showing how it would upset the performances. Kindly note these are not readings just an illustrating of my explanation. The engineers know how to avoid an overload and adjusting the fuelinjection according to the revs and exhausttemperatures, not by reading tables, as there are so many other variables like hull resistance,(draft and fouling) it is literally impossible to put everything in a list. With to days computers I presume it would be possible to make a programme, but I am that old that I trust human experience and know how before a machine .
Tore

[tore]

Don.
Page 404 ...shaftbreak....   Page407   Manual Clutch Drive ..... is to be engaor...... Page 411 ...... Air flow blower: Supercharger..... Mounted on the back side of the engine. Normally we refer to the back side of the engine  as towards the boardside ..We would say the supercharger is fitted on the aft end of the engine...
Checked OK up to page 412.
Tore

[tore]

Skizzenbuch.
 Page 375. I just stumbled over your remark on running the E compressor submerged due to excessive air pressure quoting Tauchvorschriften. It is a lot more problems than acid problem at the opening of the towerhatch. Overpressure have a negative influence on the human body, all the gauges including the depth gauges showing the wrong depth, the galley cooking the meal at higher temperatures  etc. and  is not desireable in the compartment of a submarine. As mentioned before when diving, leakages occur particularly on the diesel main exhaustvalves which always needed to be ground by the pneumatic motors which are expelling a substantial amount of air into the engineroom, moreover the inside venting of Q and other tanks all contributes to an overpressure as well and so are leakages and drains. All told, there was always an overpressure when diving, which should be taken care of. Hence if at all possible the E-compressor was started. Opening the towerhatch when the compartment had overpressure could come up with suprises, from the CO being shot overboard to the coocks pots and pan starting to boil like crazy. I have mentioned these events before, including a crewman always having a firm grip around the CO`s  ankles in case he had no time to release the overpressure prior to opening of the towerhatch.
Tore
 

[Don Prince]

Hello Mr. Tore,


I corrected pages 404, 407 and 411.  I also added a paragraph with the info you provided about Over Pressure on page 375.  I uploaded the latest version of Skizzenbuch to dropbox...


Regards,
Don_

[tore]

Don.
Page 411 the supercharger is fitted on the aft side of the engines.  Page 375 the overpressure ....you don`t have to cook at higher temperatures, it is simply that the laws of the thermodynamics makes the water starting boil at  higher temperatures. F.inst. if you put on the coffeepot it boils at 100 degrees C at normal atmospheric pressure, at higher pressures the coffee get hotter before it boils. This can have a substantial effect on the cocks pot and pans, if he has every kettle nicely simmering at an overpressure submerged and all of a sudden you are surfacing and the towerhatch is opened, releasing the overpressure, the pots and pans starts to boil vigorously spilling the food all over the galley .

Tore

[tore]

Don.
Skizzenbuch page  413 first generation schnorchel system. On the system sketch the airinlet pipe is coloured blue, however at the engineroom inlet valves on your sketch it is marked as if it enters the ventilation system as well as the diesel air inlet valve. As the text is saying the air enters only via the dieselair intake valve. See revised sketch below.
Tore

[tore]

Don.
Page 416. Schnorchelmast head  ....... inletcap and the masy..... 3rd. paragraph.......dieselebgine.....   ..... secon dieselengine.... the commander had to surfase.....
Page 418. On the schnorchel raising lowering ram assembly you  see two rods one on each side of the pistonrod. These are the guide rods for the guide shoe taking up the sideforces when raising/lowering the schnorchel mast, see image below.
Skizzenbuch checked up to page 419.
Tore

[Don Prince]

Hello Mr. Tore,

I believe I got all the corrections done and I changed out the schnorchel drawing and added the photo of the hydraulic ram.

I uploaded the latest version of Skizzenbuch to dropbox...

Regards,
Don_

[tore]

Don.
Your corrections seems to be OK.
Tore