Author Topic: Tores mailbox VIIC and VIIC/41 operation and technical details  (Read 595642 times)

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Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2535 on: 11 Mar , 2015, 01:17 »
Don.
I don`t have any figures, but if you compare the tower and wintergarten on the late WW2 VII Cs with the latest modernisation of KNM Kya I think it is obvious that the drag is much less on the latter. To days sail or dorsal fin is highly streamlined as the rest of a modern submarine, but much of the functions of the VII Cs tower are removed into the controlroom and the fin is more like a bridge and a dorsal stabiliser rather than  tower . In my time we started in rebuilding the conventional wintergarten and removing the scepters, not only to reduce the drag but lower the noise submerged as well. However as you know the submerged speed of the VII Cs was not very high in any case.
Tore
« Last Edit: 11 Mar , 2015, 01:19 by tore »

Offline NZSnowman

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2536 on: 13 Mar , 2015, 13:39 »
Hello Mr. Tore and Maciek,


The type VII U-Boats that had the modern bridge/sail in the 50's; did that make any improvement in the maximum submerged speed?  I would think the modern sail would present less forward resistance?


Regards,
Don_

I remember reading somewhere that someone run some Fluid dynamics software test on the Type VIIC’s. He said that most of the drag was causes by the open bridge of the Type VIIC’s and that the wintergarten had little effect on the drag.

Offline Don Prince

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2537 on: 13 Mar , 2015, 21:03 »
Hello Mr. Tore and Simon,


I found 3 drawings and 1 photo...  #1 - English, #2 - Italian (Work on the bridge of the KYA (U926). This aerodynamic conversion was suggested by von Haggstadt in 1959. #3 - Norwegian (K-class or conversion).


Regards,
Don_
« Last Edit: 14 Mar , 2015, 13:22 by Don Prince »
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Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2538 on: 14 Mar , 2015, 01:20 »
Dorsal fin.
Simon I think it is correct that one of the main drags submerged is caused by the open bridge on the VIIC. Don has shared a few interesting images showing the design of the tower conversion by the Norwegian naval architect and engineer in chief of our submarine designs Kåre Hegstad ( not von Hegstadt) I knew him very well and he developed a new tower design including a telescopic schnorchel mast for our U (V) class UK built submarines in my time ( image below). Later he started to do the same with our VIICs only to finish KNM Kya before he involved himshelf in the development of a total new submarinedesign in cooperation with German designers ending up with our brand new Kobbenclass in the 60 ties which relieved our VIICs and U class.
Tore

Offline Don Prince

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2539 on: 15 Mar , 2015, 23:58 »
Hello Mr. Tore,


Do you know if Kya (U-926) ever has the updated sail/bridge modernized?  I found a photo of Kya, and it looks like someone doctored this photo to created Kya with a updated sail...


Regards,
Don_
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Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2540 on: 16 Mar , 2015, 00:37 »
Don.
I don`t know where you got your Kya 2 image but it is a fake. Somebody manipulated an old photo of KNM Kinn ex. U 1202 and put a dorsal fin on her, changed the pennant no. from S 308 to S 307 pretending she was the Kya, see my images below. The real fin of the modernised Kya was slightly different as she kept the hinged schnorchel in a recess in the fin.
Tore

Offline Don Prince

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2541 on: 16 Mar , 2015, 21:32 »
Hello Mr. Tore,


It's hard to understand why someone would fake information on the net like that.  I guess it takes all kinds of idiots!  I'm glad I caught it because I don't want false information in Skizzenbuch.  I updated Skizzenbuch and page 432 is about Kya and it's modified dorsal fin/sail..


Regards,
Don_
A man's got to know his limitations...
Harry Callahan, SFPD

Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2542 on: 17 Mar , 2015, 01:15 »
Don.
I have read your last amendment to your Skizzenbuch and have a few remarks. I know there are information referring to different sources that U 926 surrendered in UK and later transferred to Norway. This is not true. Correct story is given by Aircommodore Derek Waller in his paper U boat in Norway post 8th . May 1945. U-926 surrendered in Bergen May 8th. 1945. All the 96 Uboats surrendering in Norway was soonest possible transferred to Scotland apart from 7 Uboats which were declared unfit for sea. Among these were U-995, U-1202 and U-926. The reason that U-926 was not seaworthy was they had overstressed her MBT 3 creating structural damage to the pressurehull. This damaged was caused by a mistake when blowing the tank by her own crew at the end of WW2. I have personally inspected the tank and the repair carried out. She was commissioned as our first VIIC and was an operational submarine (not training or research) 10. January 1949. She was my 2ND and last VIIC in 1954.
Tore
« Last Edit: 17 Mar , 2015, 01:46 by tore »

Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2543 on: 17 Mar , 2015, 05:53 »
Don.
Further to my previous remarks on KNM Kya, your drawing showing Kya with dorsal fin is strange as it shows a port casingside of a 1942 execution on starboard side omitting the anchorbay and the correct floodgatepattern as well as the submerged exhaustoutlet. A common mistake made on several sideview drawings of the VIICs,  including the one you show is the Kingston arrangement for MBT 3. MBT 3 has three Kingstons on each side two in pairs forward and one aft. Somehow people like to make double pairs on both sides. See my image below.
Tore

Offline Don Prince

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2544 on: 17 Mar , 2015, 11:04 »
Hello Mr. Tore,


Submerged exhaust outlet?  Was that something new?  I don't recall a exhaust outlet of that type on a type VIIC...


Regards,
Don_
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Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2545 on: 17 Mar , 2015, 13:03 »
Don.
There are several types of exhaust outlets, I believe Simon has made a list telling which Uboat has the various outlets. As far as I remember all our VIICs had the submerged type.The image below shows the damaged U-510 having the submerged type and the KNM Kaura having same. However the museum U 995 was rebuild with the air exhaustoutlet which can be seen on the image below as well.
Tore

Offline Don Prince

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2546 on: 17 Mar , 2015, 18:14 »
Hello Mr. Tore,


Thank you for the info about Kya and the exhaust outlet below the water line.   I updated page 432 in Skizzenbuch and uploaded it to dropbox...
Regards,
Don_
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Harry Callahan, SFPD

Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2547 on: 18 Mar , 2015, 01:17 »
Don.
I have checked your last issue of the Skizzenbuch. I guess your assumption that the crew of U 926 deliberately damaged the U boat is not according to fact. In order to understand the cicumstances I shall give you a breafing. Following Hitlers suicide in April 1945 Grossadmiral Karl Dønitz, admiral of the submarines became the new Fuehrer. The situation in Germany was hopeless,but in Norway he had a full war equipped army of 300.000 men plus 87 fully equipped uboats being a considerable threat to the allies. Therefore as late as 4. May 1945 the orders from Befehlshaber der Unterseeboote (BdU )was issued:  Norway  is the headquarter of the Uboats operational control, the war goes on. It looked as if Dønitz had desperate plans to continue fighting out from Norway. On the continent scuttlings of uboats took place. (Operation rainbow), but not in Norway were everything was in control.
 The overstressing of U-926s pressurehull took place early April 1945 and at that time it would be a treason to deliberately destroy an Uboat. A fully functional Naval high command would prosecute the responsible person for such an action with deathpenalty as a consequence for the guilty people involved.  No such penalty took place so I guess the high command concluded it was an accident caused by inexeperienced crew and possibly a faulty reliefvalve causing the dammage.
Kindly note U 926 was not a sister uboat to U-995 as U-926 was a VIIC and 995 a VIIC/41.
Tore
« Last Edit: 18 Mar , 2015, 01:29 by tore »

Offline Don Prince

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2548 on: 18 Mar , 2015, 11:56 »
Hello Mr. Tore,


Perhaps a Step-Sister Ship - Once Removed?  I'm just joking of course...  Thank you for the correct information on U-926 Kya.  One question - after the repairs to the pressure hull, were there any diving depth restrictions imposed on Kya?


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


Regards,
Don_
A man's got to know his limitations...
Harry Callahan, SFPD

Offline tore

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Re: Tores mailbox VIIC and VIIC/41 operation and technical details
« Reply #2549 on: 19 Mar , 2015, 00:23 »
Don.
Last update of the Skizzenbuch OK. Kya did not get any restriction as to max. diving depth officially. However we imposed unofficially testdiving to 100m nevertheless we accidentally touched the 115m mark without any problems.
Tore