Okay, since you are a good friend I will accept your proposal :haha:

I took a short break from studying today and found some information that might be useful to understand drag. Much of it is highly technical, but it might give you some ideas for balancing drag coefficients. First, here are a couple quotes from Ulrich Gabler's Submarine Design:

Regarding wave drag at different depths:
Regarding periscope drag:
Note that he is talking about true submarines, as opposed to submersibles like U-boats, in the above quotation. I would imagine that the physics for an extended periscope would be similar, but I don't know enough about modern submarine design to say for certain.

And this:

Here are two PDFs that might also be helpful. I have only had time to skim them very briefly, so I can't give you any specifics. This first Australian defense study is interesting. It also contains a concise summary of drag equations as an appendix:

http://www.mediafire.com/view/?d0opglynbhsr9it

The second PDF is probably less useful, but I included it for good measure:

http://www.mediafire.com/view/?134360wcio6bwoe

Thank you Keyser. I am currently busy with a more trivial task (I want to replace the poor shell icons visible in gun camera with real shells used on U-boats), but I will have a look into the essays pointed by you as soon as possible :salute:

Sound like a great project :up:

The two PDFs are quite long, so it's probably not necessary to read them in their entirety (unless you enjoy that sort of thing :03:). The Australian defense study is actually fascinating, even if it is not always directly relevant to flak gun drag. I would not spend too much time obsessing with the drag equations. Unless we can find specific numbers pertaining to U-boats, this information is more useful as a general guideline for game balancing.

Just found some more information on U-boat gun ordinance:

U-boat Munitions thread on uboat.net. Talking about type IX U-boats, it reports (unrefernced):

• 20mm ammo: 8100 rounds (when using 2 twin 20 mm guns); HE tracer and HE tracer incendiary, (Minengeschoß used after June '43);
• 37mm ammo (gun model not specified): 2575 rounds; HE , HE tracer and HE incendiary;
• 105mm ammo: 150 rounds; AP, HE, incendiary and star shells.

U-boat deck guns thread on uboat.net:

• 88 and 105mm ammo: AP, HE and star shells (David Miller's "U-boats" mentioned as source);
• HE (with or without tracer) were surely available, but some doubts are raised on the utility of carrying star shells and AP rounds; the following reasons are abduced:
  • HE rounds would have been more than enough to breach the 5-8 cm plating of merchants (and destroyers, escort destroyers, frigates, sloops, etc);
  • moreover, HE rounds would have caused a bigger hole ( 2.5 feet for 10.5 cm ammo) than AP shells.
  • on the other hand AP rounds were reportedly known to pass right through merchant hulls and explode in the water on the far side of the ship, thus causing an hole of the same diameter as the projectile
  • their use would have been productive only against vessels that U-boats would have normally avoided.

F.d.U./B.d.U.'S War Log 16 - 30 June 1943:

I've been doing some work on turm and flak availability and cost, but I have questions about two issues

First, if I'm not mistaken the starting turm arrangement in SH5 is with the flak gun sited on the after deck, rather than on the bridge. But Robert Stern writes that this arrangement was abandoned before the war, due to a number of disadvantages with having the flak gun so far from the tower hatch. He says:


My second question has been bothering me for a while now. Does anyone know what the C/30 twin that exists in SH5 is supposed to represent? Most of my sources never refer to a C/30 twin being fit to any U-boat towers. As far as I can tell, the upgrade path went from single C/30 to single C/38, then to twin and quad C/38s, and finally to the 37mm guns. There were variations along the way, especially with the MG151 and the Breda 13.5mm guns.

Stern is the only source that explicitly mentions a C/30 twin:

I'm probably just missing the obvious, but is it safe to assume that the C/30 twin and the MG151 are the same gun? Is he using "C/30 twin" and "MG151" interchangeably? As an additional complication, I've found conflicting evidence about whether the MG151 used a 15mm or a 20mm cartridge. The wikipedia article suggest the original Luftwaffe gun was redesigned to fit the 20mm round in 1941, which might be the source of this confusion. Does anyone have additional information about this?

:yeah:

That's true, in game, the standard armament for Type VIIa U-boats includes a single FlaK C/30 mounted on the deck, abafter stern. I will check my sources to see what they say on the topic.

The gun that you are talking about is designated as twin C/38 in stock game, but it got practically the same specifications as the twin C/38 with shield. Since in my opinion it was pointless to have two slightly different models of the same gun, I decided to convert the unshielded version into a double C/30. :yep:

Your historical specifications document makes mention of a twin C/30, and I am sure that it is also listed in some of my sources (I need to recheck them, though). The gun was probably only of marginal use, or maybe its use was initially planned but never really implemented. I will post an update on it as soon as I find the above mentioned sources :hmm2:

There are no many sources on the MG151, besides the one you have already mentioned. In any case, it is sure that the FlaK C/30 and the MG151 were two completely different guns :yep:

One other source mentions that the transition happened "before 1940."

Ohh, that makes more sense. So there is no C/30 twin in the stock game? I never survive long enough to make it to the later years so I don't know from experience :O:

Yes, my mentioning the twin C/30 in that document was a consequence of the aforementioned quote from Stern's book, as well as the fact that I thought I had seen a C/30 twin discussed in this thread. It was a misplaced desire to be complete, whereas I should have raised my concerns immediately :oops: I don't believe I have ever found any specifications for a C/30 twin. I see that I listed range and ceiling data for it, but I believe that was a copy & paste mistake from copying the C/38 twin chart. I'm pretty sure Skwiot does not mention a C/30 twin either.

I'm beginning to suspect that perhaps BdU requested a twin C/30 mount with dual MG151 twin in June 1942, but no twin C/30s were ever produced or fitted, since the C/38 proved a better adaptation anyway.

Sounds good and thanks for the clarification :up:

I need more time to gather all the information I have on conning tower usage. As soon as I get it ready I will share it, so to make you able to take a more pondered decision.

Navypedia lists all the possible gun/mounts conbination. No mention is made of a twin C/30, so you are probably right: this gund didn't exist anywhere but in my fantasies :doh: :O:
Unless we find some contrary evidence, I will revert its specs to C/38 standards, but with slightly better handling and lesser armor than the shielded version (hoping that my destructible gun tweaks will work) :03:

Thanks and take your time


Navypedia lists all the possible gun/mounts conbination. No mention is made of a twin C/30, so you are probably right: this gund didn't exist anywhere but in my fantasies :doh: :O:
Unless we find some contrary evidence, I will revert its specs to C/38 standards, but with slightly better handling and lesser armor than the shielded version (hoping that my destructible gun tweaks will work) :03:[/QUOTE]

Sounds good. I will let you know if I find anything else...fingers crossed that the destructible gun tweaks work :yeah:

Have you looked into uboat.net yet? It says:

Then it lists some turm upgrades (from I to IV) plus a few special configurations.

:sign_yeah: :D

More controversy :hmmm: If that is correct, then maybe Stern meant that all previously constructed Type VIIs were in the process of having the gun re-sited at the outbreak of the war. I'm not sure why this would take until 1940, though. I will see if Skwiot mentions anything about this.

From David Miller's U-boats History, Development and Equipment, 1914-1945 (p. 30):
If we have to believe it, we should deduce that the deck-mounted 20mm gun was the one armament design used on VIIA U-boats, abandoned with the Type VIIB.

EDIT: I am attaching Miller's description of Type VII's tower variations. He also makes some light on the MG151's controversy :yep:

http://imageshack.us/scaled/thumb/7/...variations.jpg

Quick addition: David Westwood's The Type VII - Anatomy of the Ship got some good drawings of various armament and conning tower arrangements. You can get this book for free from scribd.

Of special interest:

table A2: General arrangement Type VII as in 1936-39 (p. 28-29)
tables A3-A4: General arrangement Type VIIB as in 1940 (pp. (pp. 30-31)
tables A5/1 and A6/1: General arrangement Type VIIC as in 1944 (pp. 33, 37)
tables A12/1 to A12/16: Variations in bridge layout and armament (pp. 42-47)

In particular, from tables A12/1 and A12/3, it can be seen that Type VIIA, and the VIIB in its original form, had one 20mm gun mounted abaft tower. This layout was modified on 1940 for the Type VIIB, with the addition of a wintergarten to the turm :up:

Another piece of the puzzle: according to Möller and Brack (The encyclopedia of U-Boats, p. 69), Type VIIA's armament included:

so it seems that even VIIA boats had their conning tower upgraded, but indeed by the reported date, no one of them was a front boat anymore. :03: