Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Don.
Skizzenbuch page 419. I see you refer to the CO of U 995 as the holder of the Knight Cross (Ritterkreutz) which is correct, but yet a bit on the borderline. Hans Georg Hess being the youngest CO ever of a U- boat was on one of his last missions with U-995 February 1945 and sighted a Norwegian freighter S/S Iddefjord of 6300 DWT in the harbour of the Norwegian town Kirkenes, unloading supplies to the inhabitants. At that time the town was recaptured from the Germans by Soviet troops. Allthough his orders were to go after the Murmansk convoys he called in his officers and said: Gentlemen how about an attack a la Prien, suggesting the should sneak into the harbour of Kirkenes and sink the Iddefjord. So they did and they launched 3 torpedoes registered 3 explosions which they recorded as hits. However non of the torpedoes were hits they exploded in the nearby rocks and Iddefjord sailed unharmed a few days later. The sinking of Iddefjord was recorded by the high command and CO Hess got his Ritterkreutz. He was confronted with this some 50- 60 years later at a meeting with some Norwegian merchant naval gunners in Kiel and answered he had been convinced he had sunk the Iddefjord.
It is correct that 8th of May 1945 U-995 was at the yard in Trondheim installing Schnorchel that save her from operation Deadlight as she was unfit for passage to Scotland.
Page 421. U 480 2ND. warpatrol. The report is very interesting and correspond to my experience during a 28 days test schnorchelling with KNM Kaura ex. U 995. The underpressure could be a bit unpleasant possibly more that an overpressure. We expelled the garbage in the same way by the torpedo tube without a piston, however we did not use cans, but bags which sometime bursted and fouled up the torpedotube much to the torpedopeoples dismay.
I have put up a table in order to visualize the effect of the pressure fluctuations by showing the changes of water boiling temperatures. The yellow parts are the normal underpressure and the green part the normal overpressure. Red are the figures at normal atmospheric pressure.
Skizzenbuch checked up page 423.
Tore
 

[tore]

Don.
Pages 425 to 441 not checked, pages 441 up to 444 checked OK.
Tore

[Don Prince]

Hello Mr. tore,

I had to change the write-up on page 376; the gas law would not actually work for the boiling point of water with changing pressure.  I found a formula on the internet:

Boiling Point = a constant (K = 49.161)  x Ln  [pressure(in Hg)] + 44.932

This seems to be very close to the chart that you posted.  I used the chart and changed the text because I didn't want the reader to attempt the formula (which I did not include), and use the Windows scientific calculator to check the results.  In addition, I found some very interesting info on under pressure when running with the schnorchel.

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

Regards,
Don_

[tore]

Don.
I agree, the use of water in the demonstration of the ideal gas law is not very wise, as you see I deleted yesteday the formula.
Tore

[tore]

Don.
I checked your page 376 and think it is better. On a RN submarine the schnorchel float valve would shut and not close .
When mentioning the the battery electrolyte, this was of course one of the vital elements in staying submerged. Every morning and evening the chief electrician measured the specific gravity of the battery electrolyte and wrote the figures on a blackboard in the wardroom. We all kept an eye on that blackboard.
Tore

[tore]

Don.
Pages 442, 443,and 456 checked OK and that completes my checking of your Skizzenbuch. As to the Pillenwerfer I can briefly mention that this device was used to launch signal rockets as well, for instance during exercises and in case of emergencies .
I guess a book like yours never shall be flawless being packed with details from many sources of different qualities. Nevertheless it shall be an important source of information for people interested in submarines generally and the VIICs particularly.
Tore

[Don Prince]

Hello Mr. Tore,

Thank you for all the effort you have put into guiding me with Skizzenbuch in the current form.  I have to create a version for Schiffer Publishing with all the special characters, and one for my Leather post binder which is just a 1.75 inch binding side offset.  This is just a conversion process now that I have a final version in hand.

Kind regards,
Don_

[tore]

Don.
Wishing you good luck with your next step.
Tore

[falo]

Hi Tore,


just another question: Did you use the Enigma-Machine for coded radio transmitting on "Kaura"?


In a a tv documentation I saw a few years ago it was reported that the Royal Navy gave the Enigma Machines to there allies (for example India) with the evidence that they never cracked the code (as an quality attribute). From then on the Royal Navy was again able to read along the radio transmission. Unless I'am mistaken this secret was uncovered in the nineteens by the RN themselves.


Thanks and regards
falo

[tore]

Falo.
This is a bit off my line, but I don't think we ever used the German Enigma Machines. As in my time we were member of the NATO having its own standard of Crypto- and Cipher systems of which I don`t know very much. I guess the bases for the German crypto-/cipher machines was developed at the end of WW1 and commercially available in the thirties. I presume the Enigma has been refined many times since then. I should assume the value of revealing the German WW2 Enigma system was not the system as such, but rather to keep the news about the revealing secret so the Germans continued to used the same system unchanged. But as I said this was definitely not my field.
Tore

[falo]

Hi tore,


thanks for the information. Certainly you are right with the NATO standard. Funny to mention that during my army days in the mid eighties as a combat engineer I was also in touch with radio transmission and field telephone but I forgot all that NATO stuff until your answer. Maybe embarrassing to say but I thought always Norway was neutral as Sweden during the cold war. Sorry for that wrong conclusion   


Thanks again and regards
falo

[Don Prince]

Hello Falo,

If you are interested in the Enigma, then this youtube video may be of interest.  It tells the story of the Bombe development by the National Cash Register Company (now the NCR Corporation) after the German Kriegsmarine went from the 3 rotor to the 4 rotor Enigma machine.

https://www.youtube.com/watch?v=v33IPQwKFKY

I started working for NCR back in February 25, 1963 and retired on April 1, 2009, after a little over 46 years of service.

Regards,
Don_

[falo]

Hi Don,


thanks for the interesting youtube link.


Regards
falo

[tore]

Don.
I had a quick glance on your latest Skizzenbuch page 341 dealing with the venting of the MBT 2 & 4 port and stb. The residue venting valve for MBT2 port and stb. is named on your drawing as aux valve. I suggest you use residue venting valve. Likewise the emergency shut off valves for MBT 2&4 port and stb are named as ventilation valve , I suggest you name same emergency shut off valves to prevent confusion. The same goes for the emergency shut off vent valves for MBT 3.
The venting system is one of the prime systems on a submarine and the VIICs have one of the most extensive mechanical operation systems for ballast tank venting. For a quick operation of the MBT 3, 2&4 the venting of these tanks are done by large pull- push levers in the control room. The mechanical rods and links for these vents might be a bit complicated and I believe some of the drawings shown are not 100% correct. At the order Dive,Dive, Dive the levers are pulled down opening the ventvalves and as soon as the air has escaped, the vents are shut  by pushing the levers up in a more or less horizontal position. On plate 28 and the U historia drawing for some reason the shut position is shown with the levers down. In that case the levers would be an obstruction for the crew under normal circumstances. Normally they are up shut as on the museums U-995.
Down below I have tried to explain the open/shut position of these very important vents.
Tore

[Don Prince]

Hello Mr. Tore,


I have had an issue with the Vent levers ever since I seen both the u-historia.com drawings and the original German Plate 28!  Below I have redrawn both Ventilation levers...  What do you think?


Regards,
Don_