Tores mailbox VIIC and VIIC/41 operation and technical details

[VIC20]

Tore and Maciek, I'm still not certain how large (effective) the air & water openings really where - I wonder if the numbers on uboatarchive take grille into account.


Could you open the kingstons or the air outlet venting valves partially? Or were they all like flaps only?


(still have no idea how a kingston really works)


BTW:
I've made a miniature "MBT" of a water bottle and recalculated openings so that the volume and openings fit to MBT3 - did that just to get a totally rough idea how fast this thing could really fill. …sure pressure difference is different and several other effects so it's worthless but it gives at least some really rough idea. This thing filled up pretty fast - 12-13 seconds (and the lowest depth is just the depth of the bottle) - If someone wants to have some fun with water: necessary holes are (I think) like 7.6 * 7.6 mm and 2.2 * 2.2 mm for a 1 liter bottle 

[SnakeDoc]

Hi Mark,

Tore and Maciek, I'm still not certain how large (effective) the air & water openings really where - I wonder if the numbers on uboatarchive take grille into account.

I have no other numbers than these on the uboatarchive.net. The MBT 3 as well as RFO&MBT 2 and 4 have no grille. MBT 1 and 5 have rather flood slots than grille.

Could you open the kingstons or the air outlet venting valves partially? Or were they all like flaps only?

The flood valves were normally opened while at sea, so you don't need consider them partially open.
The vents construction is visible on this plate:
http://uboatarchive.net/U-570Plate28.htm
I think, that only vents of MBT 1 and MBT 5 could be consider partially opened.

--
Regards
Maciek

[tore]

Mark.
Further to Macieks remarks. The Kingstons working is based on the travelling nut principle. For MBT 3 the threaded valve spindles are supported in two location- and turningbearings, the spindle ending through a pressure stuffingbox in a square end in the CR where a removable crank turned the valvespindle. On the spindle is a travelling nut fixed to a yoke moving the Kingston outwards as indicated on my sketch below. You could in fact open it in any position but as Maciek says it was normally not done. The saddletank Kingstons are operated in the same way as can be seen on plate 28 but open inwards. The MBT 3, 2 and 4 vents were directly operated by handle and rod movements and are either shut or fully open as can be seen on plate 28. All the moving parts inside and outside the pressurehull have grease connections.

[VIC20]

tanks err thanks 

[VIC20]

Tore, I think you mentioned the "jet effect" somewhere in this thread. How does that work?
When the tank if full of air and the boat raises the water pressure sinks so air will leave the tank through the flood port, is it just the power of the leaving air that makes such a huge difference when surfacing?

[tore]

Mark.
I should probably mention that it is only the forward double Kingstons on MBT3 which is operated by a yoke as seen on my photo below.
Tore

[tore]

Mark.
It is a combination of air forcing the water out of the ballasttanks at an increased speed as the air expands due to falling ambient pressure rather than anything else. However an increasing jet of water out of the Kingstons (and floodgates) is created as well. I emphasize this is absolutely not the way of surfacing, It is a waste of air and partly an uncontrolled surfacing but of course it could be a show off.
Tore

[VIC20]

Thanks, I've added the jet effect. 

[tore]

Mark.
Watergauge regulating tanks, f.o. reg. tanks.
Below is an image of same ,stb. aft controlroom, same on port side.
Tore

[tore]

Mark.
Regulating tanks reduction of volume.
Below is a red mark off showing the MBT3 airduct  passing the regulating tanks.
Tore

[VIC20]

Tore,


The 4 main ballast and reserve fuel tanks 2 & 4 stb & bb… could those operated together only? In other words: were they like a single tank split into 4 tanks sharing a single vent?
And if so, what about their kingstons? http://www.uboatarchive.net/U-570Plate28.htm shows a cross section area of flow of 3.167 m2, this is much larger than for all other tank so I guess it's for all 4 tanks together and the kingstons were opened together only?



Edit: 2 & 4 shared a vent via a duct on each side between Spant 41 & 42 - hence the pressure of air in both tanks was always equal…

[VIC20]

…when looking at your model of the Kaura I see 6 Kingstons for MBT3 and 4 on each of MBT 2 & 4. The Kingstons look almost identical from their size. I think the 3.167 m2 cross section area of flow are for each of the pairs 2 & 4 (6.334 total for MBT 2 & 4 stb & bb together)

[VIC20]

The Type VII manual shows the distance to the center of mass for all of the tanks. But the center of mass is not static, it can move - what position (horizontally) should I use for placing the tanks based on the information of the manual? (I've tried to estimate geometrical position of the center of mass (of the tanks itself) for each tank before, but this is extremely intuitive and just a rough guess)

[tore]

Mark.
The venting of the MBT 3, 2 and 4 port and stb is arranged as seen on the sketch below. 2 and 4 port and stb are opened simultaneously. MBT3 port and stb likewise.Thus you may say they are operated as one tank, however each tank venting can be shut off by a valve next to the tank in case of a possible damage to the venting duct.  I believe the flood area indicated on plate 28 is the total. If you calculate the tank volumes in relation to the floodareas you get for the MBT 3 total volume 47,7 m3/ floodarea apr. 2,76 m2 = 17,28. For the saddle ballasttanks 2 and 4 total volume 49,6 m3/ floodarea 3,167m2= 15,66. Be aware the MBT 2 port and stb has a venting in the aft end for residual venting. When diving or surfacing at an angle you shall have difference in pressure in the ballasttanks as they are at different depth.
Tore

[VIC20]

OK, then I'll keep them as 4 different tanks because of the pressure calculation and because each tank venting to the duct could be shut off.