Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Don.

It is difficult to make a general rule for changing depth, it all depends on circumstances and the COs skill and experience. Generally being submerged you change your position dynamically eg. using hydroplanes and speed which means moderate bow up going up and bow down going down. To compensate for changes in water density and hull compression you use the regulating tanks and for crew movement you use the trimtanks. If the CO want to go to periscope depth you usually go dynamically to see if you are able to hold the boat there, depending on the surface condition like waves etc. I have experienced swell down to 50 meter. Surfacing you take the boat up dynamically and carry out a periscope sweep before blowing the main ballast tanks having the bow slightly up towards the wind and waves. When breaking the surface the boat has a low stability and you want to avoid the weather hitting you atwartship. But every COs has his liking based on his experience. The image below shows not how you should do it.
Tore

[Don Prince]

Hello Mr. Tore,

It's amazing how your brain recovers after a few good nights sleep... Now it's quite obvious to me that the additional hydroplane motor current for the aft/stern hydroplane is common for both the Type VII and the Type IX U-Boats. In order for the stern/aft hydroplane motor to overcome the prop wash pressure, the motor drive circuit for the stern/aft hydroplane requires the additional motor drive current.

What do you think?

Regards,
Don_

[tore]

Don.
Sounds reasonable to me. But as mentioned before I am a bit rusty on this topic. In the meantime I have been looking at some old drawings previously mentioned and I found some VIIC el schemes which I am trying to restore, not very successful though. I am posting a couple showing part of the scheme for the rudder, aft and fore-hydroplanes. As all the drawings are in a mess and the blueprints of bad quality I am not sure it is of any help to you. I might be able to restore some more ( take some time) if you think they would be helpful.
Tore

[Don Prince]

Hello Mr. Tore,

Your original Schematic shows a little more of the wiring, but not all and the circuit items remain a empty box like the Type VII schematics which I have... See attachment.

Regards,
Don_

[tore]

Don.
 Just what I expected, the schemes are from Blohm and Voss a german shipyard building VIICs .
Tore 

[Don Prince]

Hello Mr. Tore and All,


It looks like the link to download Skizzenbuch on the SubCommittee.com forum/The U-Boat Pen website has just exceeded 300...


Regards,
Don_

[Katuna]

Its been far too quiet around here lately so I have a question for Mr. Tore.


I came across this photo on another site and found it quite interesting, to say the least. My question, however is, what is the round hatch that's open just aft of the engine room? Of course I have no idea if this is a Type VII or IX boat. I looked at Simon's plan view of his boat and I didn't see any hatch between the exhaust. It's too far forward and too high to be the aft torpedo loading hatch or am I mistaken?

[tore]

Katuna.
The engine hanging in the air seems to be a 6 cyl. direct reversible Krupp Germaniawerft engine as installed in the VIIc`s up to 1942. The Roots supercharger is removed and you see the outboards side of the engine with the combustionair manifold. There are not too many detailed images of the outboard side of this engine. I don`t fully understand your question on the circular hatch aft of the engine room, but the the large circular pipe in front of the engineroom is the flange of the large dieselair shaft coming from the dieselair intake valve operated from the controlroom. This shaft enters the engineroom just above the maneuvring places in the front of the engineroom where it is split in two ducts ending above the bilge at the outboard shipside port and starboard away from the combustion airinlet of the airmanifold to prevent seawater intrusion in the airmanifold..
Tore

[Katuna]

The round hatch I have circled in red. It is indeed rare to see any photo of the outboard side of the engines.

Could you possibly post that drawing by Simon by itself? I've never seen that one before and it would be most helpful at the stage I'm at with my model. I tried enlarging the pic you posted but it comes out much too blurry.

As always, thank you for your wisdom.

[Don Prince]

Hello Katuna,

Perhaps these drawing by Simon J. Morris will answer your question. The upper pressure hull rivets were removed from the upper pressure hull plates above the diesel engine room to provide the huge opening as seen in the photo.  I was discussing this with Simon back in January...


The hatch circled in red is the aft torpedo loading hatch (Last Drawing)....

Regards,
Don_

[tore]

The round hatch I have circled in red. It is indeed rare to see any photo of the outboard side of the engines.

Could you possibly post that drawing by Simon by itself? I've never seen that one before and it would be most helpful at the stage I'm at with my model. I tried enlarging the pic you posted but it comes out much too blurry.

As always, thank you for your wisdom.

Katuna

Don got your question right and Simons images shows clearly the aft torpedo loading design. I might add that the angle of the loadingtrunk makes locally a considable weaking of the pressure hull as frames 15,16 and 17 are cut making the oval opening in the pressure hull. As can be seen from my image below if you disregard the modern lights and wiring, this is compensated by putting removable strengthening beams across the oval hull opening. The beams have a clearance of appr 20 mm at the contact points and being submerged the compression of the pressurehull elimitate this clearance. The solution is common to most submarines from the VIIC vintage.
Tore

[Don Prince]

Hello Mr. Tore,

We had discussed the frames in Skizzenbuch with reference to the torpedo Tube loading hatch. However, we never touched on the subject of replacing a diesel engine and the disposition of the diesel room frames. The attached photo shows the upper frame missing while workers are in the diesel engine room. From this vantage point, it looks like these frames were cut into sections, but we never discussed the joining method for these frames.

Update: I found a photo on my U995 DVD that shows where the frames upper section in the diesel room overlap and are riveted together. See second image below...

Regards,
Don_

PS - I noticed that the ModelShipWorld.com (Where Katuna's photo was posted) used Skizzenbuch's colorized Plate 13 of the G. W. Diesel Engine drawing...

[tore]

Don.

The large engineroom opening for mounting the mainengines was as you know shut by a large riveted plate strengthened by riveted frames as can be seen from Falos photo below. The frames above the engine have supports for removable round bars above each cylinder. These bars were used as fixing point for winches for maintenance work like lifting cylindercover, cylinderliner, piston and pistonrod etc. You would need every inch above the cramped place to lift the parts from the engine. The riveted  plate was only removed in case of a major dammage to the cylinder block, crankshaft or bedplate.
Tore

[Don Prince]

Hello Mr. Tore,


Thanks for the info, I will add that to the Addendum Booklet. Is that person's name Falo or Falos as in your response...


Regards,
Don_

[tore]

Don.
Falo is a member of this group, you`ll find him in the members list, he has kindly allowed me to use his photos taken during his visit to U 995 at Laboe.
Tore