Tores mailbox VIIC and VIIC/41 operation and technical details

[Don Prince]

Hi Steve,


In my humble opinion - I think the skeg keel has a heavy metal lower base where the metal vertical rudder protection structure is attached besides the hydroplane drive shaft and the dual prop support.  The skeg keel only has internal vertical frames and flooding holes on each side.  There are no stringers internal to the skeg keel...  It looks to me that Stringer #1 is only internal to MBT 1 and attached to the aft pressure hull.


The 1st image Stringers 1 shows stringer #1 and it looks to be at an angle (possibly several stringer #1's).  The 2nd image MBT 1 shows a vertical slice of the U-Boat at frame +2 and the stringers are all internal to MBT 1, and at frame -6 there are no stringers visible.


I hope this helps,


Kind regards,
Don_

[tore]

Maciek.
The buoyancy tanks did not participate in the surfacing procedure as they are primarily used to improve surface buoyancy to prevent ( bow tank) undercutting. To a certain extent there are selfdraining (more timeconsuming than blowing) as the tank is situated above the surface.   When pitching I guess the waterlevel in the tanks pulsated thus compressing the air in the tank.
Tore

[maillemaker]

In my humble opinion - I think the skeg keel has a heavy metal lower base where the metal vertical rudder protection structure is attached besides the hydroplane drive shaft and the dual prop support.  The skeg keel only has internal vertical frames and flooding holes on each side.  There are no stringers internal to the skeg keel...  It looks to me that Stringer #1 is only internal to MBT 1 and attached to the aft pressure hull.


The 1st image Stringers 1 shows stringer #1 and it looks to be at an angle (possibly several stringer #1's).  The 2nd image MBT 1 shows a vertical slice of the U-Boat at frame +2 and the stringers are all internal to MBT 1, and at frame -6 there are no stringers visible.

Hi Don,

Yes, the images you have posted are quite helpful.

Stringer #1 is what I was after.

From the images you have posted, I believe that Stringer #1 does not lie on the centerline of the boat.  It probably radiates away from the pressure hull to the outer hull at angles, probably roughly in-line with the prop shaft supports, as I had previously guessed and illustrated here:



I think thiis is corroborated by your image:



So the stringer #1 that I thought I was seeing in vertical section as lying on the section plane is actually placed radially out from the pressure hull.

This means that the skeg is hollow and there seems to be nothing in between the floods on one side of the boat to the other.

The modeler I was following on the U552 blogspot site was incorrect.

I think I understand now. 

Steve

[maillemaker]

From another thread:

Hydroplanes.
The forward hydroplanes have no connection to the outer part of the hydroplaneguards. On many drawings it looks indeed as if there is a throughgoing shaft ending up in the hydroplane guard, however the hydroplane shaft end up in a fixing point about half way into the hydroplane, I guess you`ll find a bolted accesshatch at the fixingpoint.
The aft hydroplanes are slightly different although the shaft and fixingpoint are the same there is a small connection to the guard at the outerpoint. As far as I remember it is not a support shaft and bearing at the point rather a small bar shutting the gap to prevent ropes or other objects to enter the propellerarea.
The jumping wire on the fwd hydroplane guard was removed sometimes I guess at the time when the netcutters were removed. This reminds me of an event we had near Scapa Flow when we anchored waiting for orders over the night. In the morning raising the anchor we experienced the anchorcable was stuck between the forward hydroplaneguard and the hydroplane. We had to free dive  in the cold November sea (wearing longjohns) to release the cable.

So, I gather that the guard on the front hydroplanes should not physically attach to the hydroplane itself?

Also, the guy wire running from the hydroplane guard to the hull was ommitted about the time the net cutters were removed?

I have a question about the radar.  Did it emit harmful radiation to the watch crew?

Steve

[tore]

Steve.
Below are the images of the fore hydroplane as you see no connection with the guard, contrary to the aft having a nut. Yes I guess they did away with the wires around end 1942.
Tore

[tore]

We did not use the radar very much as it wasn`t any good. To my knowledge nobody was hurt by radiation.
Tore

[maillemaker]

We did not use the radar very much as it wasn`t any good. To my knowledge nobody was hurt by radiation.

But the watch crews had uncanny eyesight after their third eyes grew in! 

Steve

[Don Prince]

Hi Steve,


I believe you've got it... The one thing I had a hard time understanding at first was MBT 1 (AFT) and MBT 5 (fwd) were designed very similar to the saddle tanks (MBT 2 and MBT 4) and all being exterior to the pressure hull.  Where the U-Boat's outer sheet metal casing is the ballast tank's exterior. In the lower drawing, the frame that makes a full loop is inside the interior of MBT 1, and the U-Boat's sheet metal outer skin/casing is the exterior of MBT 1. When I first started studying the Type VII C U-Boat, I had in mind that MBT 1 and MBT 5 were ballast tanks inside the exterior hull casing. The only tank that is different is MBT 3 where this tank is inside the pressure hull under the control room floor. However, the lower portion of MBT 3 is the pressure hull which is the under belly of the U-Boat's exterior mid-section.


If I have made any incorrect statements, then I sure hope Mr. Tore or Maciek will jump in and correct me on this subject because I'm still learning from these gentlemen!


Kind regards,
Don_

[tore]

Don.
No need to jump in. The lower aft part of the skeg has space for the the pull/push rod, crank and fulcrum shaft bearings for the aft hydroplanes operation being able to move 30 degrees up and down.
Tore

[tore]

Studying the many photos of the aft part of the skeg I guess it is possible that this is cast steel riveted to the outer hull by a double row of rivets. The casting incorporate the support for the aft hydroplanes fulcrum shaft as can be seen on the image below.
Tore

[Don Prince]

Hello Mr. Tore,


When you surface a U-Boat one diesel is used to power the U-boat on the surface...  I guess the 2nd diesel is used 1st to exhaust blow the ballast tanks, and then charge the batteries. Is it possible to do both at the same time with the 2nd diesel?


Regards.
Don_

[tore]

Don.
The possibility exsist, adjusting the charging load, I would probably prefer to put the charging on the propulsion engine shaft. When blowing the ballastanks by diesel exhaust the ruling factors are the bmep ( break mean effective pressure)and exhaust backpressure as one diesel is producing ample volum for blowing the tanks. The total exhaust backpressure is constantly monitored by an engineer in the engineroom keeping an eye on the exhaustmanometer and adjusting the pressure by the outer group exhaustvave  designed for the purpose. The bmep is monitored by an engineer at the engine maneuvring stand. The distribution and pressures for the induvidual tanks are monitored by the controlroom engineer at the exhaust control panel. If for some reason the pressure becomes too high there is a reliefvalve on the engine exhaustmanifold which release the exhaust into the engineroom. I have experienced that a few times and it is very unpleasant.
Tore

[karel]

Tore


Do you if there is any source online where i could locate the lighting of the boat? I am looking trough museum panoramic  pictures and am able to see lightbulbs but they seem to be too few in numbers. They have been probably removed. I would like to keep my lightbulbs more or less at the same places where they were originally.

[tore]

Karel.
Unfortunately I have no cabling plan or images of all the original accommodation lamps/bulbs of the U-995. My best advice would be to look at the various images particularly the kubische panorama.de of the U 995 at Laboe. The museum boat has of course different lights and modern cabling racks as can be seen on my image below. The orgininal fittings are shown as well. Note the lightbulbs had a thick glassprotection as shown.
Tore

[tore]

Karel.
Following up your VIIC lampquestions. A few lamps had lampshades, like in the wardroom, CPTO mess and PO mess.The Bavarian Filmstudioes made a good research on the lamps, shades and colours for the execellent movie das Boot. Below is an image showing the various lamps.
Tore