Historically Accurate Upgrades

[Lokisaga]

Hi all,
I'm currently running a campaign commanding a Type VIIB in the 7th Flotilla in 1940. I'm running GWX with h.sie's patch. I'm trying to be as historically accurate as possible, given the limitations of the game, with getting upgrades for my boat. I've tried to do as much of my own research as possible, but I've run into two questions that I can't find an answer for, and I'm hoping someone in the community can help me out.

1. Hydrophones:
The VIIB comes with the GHG already installed. Was this the only hydrophone system those boats ever used, or did any of them get the upgrade to the KDB unit? Was such an upgrade even technically feasible considering that it required making a new hole in the pressure hull? Some of the sources I've read seem to indicate that the KDB didn't actually replace the GHG. Instead, the source suggests that the two systems were complementary to each other, but this source was from the interrogation of the captured crew of a VIIC, not a VIIB.

2. Batteries:
Was it really possible to upgrade the batteries on a U-boat once construction had been completed? It seems to me that replacement of such a heavy and bulky piece of equipment would have been arduous, if not downright impossible, but I could be wrong about that.

Thank you for your help.

[K-61]

Good questions. I cannot answer them definitively but nonetheless I would like to participate in the discussion.

I am not sure about the hydrophones. On the subject of hydrophones, I am aware that there are some very skilled players who can conduct sound bearing attacks using the in-game hydrophones. I've read that the actual hydrophones on the earlier war subs [the advanced subs at the end of the war had very advanced sets] were not accurate enough to get such precise data, and that therefore this is not a historical method. Hey, by all means play how you wish and hats off to you. I try to play historically as closely as possible so therefore I do not use this method. Not a criticism, just an observation.

Batteries... it would seem logical that the engineers who designed the U-boats would know that servicing the batteries would be a requirement and that it would be likely that damaged or worn out batteries would need to be replaced at some point. So, although I cannot cite a source, I would think that batteries could be replaced. In the film Das Boot you can see the battery access hatches when the Chief goes down to bridge the damaged batteries. That looks like quite a sizeable opening. I would think that in the yard, with the proper gear they could get in there and haul them out. If it were not possible to replace batteries, then the boat's career would be limited at best according to the status of the batteries. I just can't see the Germans designing subs with such a flaw. My guess.

[Lokisaga]

Thank you K-61. Your comments on the batteries make a lot of sense. I hadn't thought about the need to regularly replace old, worn-out cells.

[Sailor Steve]

As for the batteries, I'm not sure either. On first thought it would take an awfully big opening to get them in and out, and this would compromise the pressure hull. On the other hand they had two hatches going through the pressure hull big enough to get a 21" wide torpedo in, so maybe a removable section for the battery isn't so far-fetched after all.

[Sailor Steve]

The individual cell would pass the 21" torpedo hatch.
I don't disbelieve, because I don't know, but I see nowhere in the linked article that says that.

Also, a large part of the text you copied and pasted seems to have nothing to do with the question at hand, which is replacing or upgrading installed batteries.

[Aktungbby]

:salute: fixed!

[Sailor Steve]

Fixed what? I just wanted to know if there's other information out there. I like to see problems solved.

[Aktungbby]

Slim INFO all 'round:wah:: Well after two hours of relentless (last night) hunting under 'U-boat battery' in German and English sites with a photo of a repairman working on 'it is apparent that the cell is small enough to go through the hatch. http://uboat.net/media/photos/mal.jpg http://uboat.net/media/photos/afa1.jpg (figure the cell size from the techs fist (Mine is 4"+-) and/or tool length size.) Easily under 21".... An AFA technician repairing a battery cell in a German type IX boat, summer of 1942. http://uboat.net/technical/batteries.htm (http://uboat.net/technical/batteries.htm) http://www.jewishvirtuallibrary.org/jsource/Holocaust/VartaFactory.html (http://www.jewishvirtuallibrary.org/jsource/Holocaust/VartaFactory.html)

[codmander]

batts are THEE most important part of any boat and need replacing,,fixing cables n such access to replace vital:huh: without batts any boat goes nowhere:up::up:

[CaptBones]

Changing battery cells, that is...

The battery cells for USN “Fleet” boats, and the Guppy conversions, measured approximately 15”x21”x54”. Given the technology of the day, I’d suspect the battery cells for U-boats were about the same size. So, would they fit through a 21” torpedo loading hatch? Probably, given that the torpedo is 21” in diameter and the loading hatch would be somewhat larger…about 26” on our boats, IIRC.

But, that isn’t necessary, or even a good idea. First, battery cells are rather fragile (that’s why they are installed in “jars” in USN subs). You do not want to be handling them in any orientation other than vertically and with special lifting/rigging equipment attached, which makes them a bit bigger all around.

So, even as K-61 alluded to, the engineers who designed the boats (ours and theirs) incorporated battery loading hatches exactly where they were needed. According to David Westwood’s excellent book “The Type VII U-Boats” (Anatomy of the Ship series), there was a battery loading hatch in the Officers Quarters/Wardroom, directly above the forward battery compartment and another one in the Engineers’ and Senior Rates’ Mess, directly above the after battery compartment. In fact, on pg 69, the “Battery service and lifting tray” for the aft compartment is shown, along with the clearances for hoisting the tray up to and through the hull opening. Judging from how the forward battery loading hatch is depicted on pg 79, the loading hatches were fitted into a coaming and bolted down; to be unbolted and removed only when changing cells.

As for the KDB…cutting and welding on the pressure hull of a WWII era sub would not have presented any particularly difficult challenges. The hull plating in the forward sections of a Type VII U-Boat pressure hull was from 12 to 18mm in thickness. The welding and weld QA testing processes of the day would have been up to the task of cutting a hole and welding a packing tube fitting for the KDB. But, as also mentioned, the external KDB apparatus was very vulnerable to damage.

Frankly, it would be tactically more sensible to just maneuver the boat to establish a satisfactory “baseline” for passive triangulation of a hydrophone contact. That’s exactly what we…er…”they” do today. The passive SONARs consist of hydrophone arrays installed all along the length of the sides of the hull, with further “extensions” through the use of towed arrays.

"Press on" mates...good hunting.:salute:

[Lokisaga]

Thank you for all the information. I'll definitely be using it in my game.