Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Steve.
I don`t think the VIIC has much of a keel in the aft end, the keel begin at about frame 14. Aft of that a double skin hull takes over before it gradually is transferred into a skeg. May be my images below gives an indication. A detail which seems to be forgotten by everybody is the zinc anodes which are protecting the area from galvanic corrosion. You might see the steel fixing straps on the A brackets. The zinc anodes were only plates of zinc app. 20x35 cm 20-30 mm thick fixed to the propeller A brackets as sacrificing elements for the galvanic corrosion.
Tore

[maillemaker]

Ah-ha, but your blueprint does show the frame/baffle with holes in it above the skeg.

The schematic I was looking at does not show it:

http://files.balancer.ru/forums/attaches/2013/03/31-3107743-planstypeviic.jpg

But yours does - do you have a larger version of your schematic?

Thanks,

Steve

[maillemaker]

This is the piece I need to create:



Steve

[tore]

Steve.
May be one of Simons excellent drawings would clarify the matter.
Tore

[maillemaker]

Hi Tore,

Unfortunately, Simon's drawing does not show the central keel baffle that is in your schematic above.

You can see where I highlighted it here:



Steve

[Don Prince]

Will this help?


Regards,
Don_

[tore]

Steve.
I guess I finally understand your question. I don`t think it is  an alongship bulkhead in the skeg, only atwartship frames and skin. What you see on my crossection drawing is an indication for a doubler in the way where you have support for the propellers-, rudders- and hydroplanes- guards. I guess Simon has indicated the doublers very well on his drawing.
Further you`ll see the crank for the aft hydroplanes operation is fitted in the center of the skeg.
Tore

[maillemaker]

Hi All,

What I am trying to do is make the section of the keel that is behind the lower floods, fore and aft.  I have achieved the forward ones.

This is the effect I am trying to duplicate, from another modeler:



In Tore's earlier post he showed this picture:



In this image, on the aft end of the pressure hull, both above and below you can see a frame with flood holes in it, presumably along the centerline of the hull.

I have highlighted it in this close-up of the same image here:



The purpose of this detail on the model is simply to make it so you don't see straight through the floods from one side of the ship out through the other side without seeing a mock-up of the internal structure of the ship.

All subsequent schematics posted do not show this detail. 

Perhaps it is not really there?

I believe at this point I will simply fake something in; the detail is not actually important as no one will be able to directly see it.

Steve

[tore]

Steve.
You are not the first one who makes effort in preventing that you should not "see through the free flood gates. For some reason there are aversions to this possibility. The fact is you are able to "see trough" on the real VIICs as there are no center bulkheads, so why make up something which are not there in real life? You should never copy the details on the museum U 995, but in this particular case you may, see my images of the area below, on one of the original photos you are actually able to see through the freeflood area.
Tore

[tore]

Steve.
My image showing a longitudenal cross section of the stern is probably not a very good one as the doubler is drawn as a square box which might be mistaken as a floodhole. However Simons drawing is correct and he has drawn the doublers as they looks. A doubler is an additional steelplate riveted in places to increase the strength locally, in these cases to support the propeller-,hydroplane- and rudder guards connection to the hull.
Tore

[maillemaker]

Hi Tore,

The issue is not being able to see through the floods, but to see through unobstructed.  There should be something seen partially blocking the view if you look through the floods.

However, looking again at your picture, the piece that is missing from Simon's drawing may be above the floods anyway.



Though it is not clear to me what this framing structure would rest on if it does not go all the way to the keel.  It would be like a "fin" welded to the aft end of the pressure hull attached to...what?

Steve

[Don Prince]

Hi Steve,


I believe you are looking at stringers with holes (baffles) which are internal to MBT 1. So I believe Simon's drawing is correct (but doesn't show the lower internal stringer) and Mr. Tore pointed out the heavy metal strip which the post was attached.

[maillemaker]

Oh, I think I see what is going on here now.

These stringers are not on the vertical cross section of the hull.

It looks like they are at an angle. 

So instead of going straight down from the pressure hull to the keel, they go radially out from the pressure hull to, it seems, the outer hull, intersecting just above the floods.

I think this is the correct interpretation?



So there appears to be nothing in between the floods looking straight across the hull.  So the previous modeler's interpretation was incorrect.

Thanks,

Steve

[tore]

Steve.
May be my image below illustrates how the double skin hull is attached to the pressurehull, the image is of a IXC but the system is the same as on the VIICs.
I don`t think there are any floodholes in the skeg.
Tore

[SnakeDoc]

Hi Tore,


regarding the discussion about type IXC buoyancy tanks in the next thread, I would like to ask you, how these tanks were used on KMN Kaura? Did you cruise at surface with tanks flooded or blown? Or depended it from the sea state?
If flooded, with vents permanently opened?




--
Thanks, regards
Maciek