KRIEGSMARINE CENTRAL - KM Ship Plans/Discussion

[_Sarcasticat_]

I just wanted to share this bit of interesting information with the rest of you since I had it pop up in recent conversation with one of my other naval circles.

The Breyer Proposal

What we're looking at here is a page coming from the 1970 first-print copy of Siegfried Breyer's Battleships and Battle Cruisers 1905-1970. What we're looking at specifically here is Gneisenau, "Modification Project 1942/43, made according to official records". Note the use of the word "records". This does not say "plans", "images", "sketches", or any other form of drawing, but written records.

So...what is so special about this drawing of Gneisenau?
What makes this particular rendition of Gneisenau's 38cm rebuild so interesting is that it takes a stab at depicting the short-lived plan to provide a unified (single-caliber) Dual-Purpose secondary battery for the ship, replacing the split 15cm/10.5cm secondary gun battery. This is perhaps the earliest attempt at doing so and provides a unique, if incorrect, depiction.

Unified-caliber dual-purpose secondary batteries had gained some amount of traction as early as the late 1930's, as far as I can tell, with the planned Deutschland rebuilds. This rebuild, planned for all three Deutschland-class ships, called for dual-purpose 128mm guns to replace the 15cm/55 singles and 10.5cm twins (the type and number of these 128mm guns is unknown***). More concretely, in 1941 there was also the suggestion of a unified 128mm DP secondary battery for H41 in place of her standard secondary battery (6x2 15cm/8x2 10.5cm). Again, number and type are unknown. This can be found in RM6 if you want to go searching for it.
And, of course, we have the somewhat well-known Gneisenau conversion to 128mm DP guns plan.

Spoiler: *** =

* = Given the year of the planned rebuilds, the Drhl. C/38 turret - the shape, size, weight, and other dimensions completed by the time of the rebuild proposals - is the most likely choice for this (even if weight savings were not as high as expected). By the calculations I made you could get 5.5 (limited to 5 in reality) regularly armored (30mm face, 20mm sides) Drhl. C/38 twin turrets with 12.8cm/45 SK C/34 guns. These turrets would most likely be placed 2 to a side with one centerline aft, replacing the 10.5cm gun there. If this was done, there would have been a weight savings of 29.5 tonnes. If you were to de-armor the turrets for approximately 42-43t, you could get 6.6 turrets (6 with weight savings, 7 with a slight weight penalty) (3 to a side or 3 to a side with one centerline aft). Alternative armor arrangements for the turret have been considered before, the particular example in mind being the O-class (14mm), and of course the smooth-ified Drhl. C/38 for submarines is likely unarmored given the weight (42.2t). A small weight penalty could be allowed for as the ships were expected to increase upwards of 700t in their rebuilds.

For Breyer's interpretation, he has decided to use the 128mm/45 SK C/41 in Drhl C/41 twin turret, developed and prototyped in 1941, therefore replacing the 15cm/55 and 10.5cm twin turrets on a 1-for-1 basis for 11 turrets total. He also took the liberty of upgrading the AA and adding a small tactical radar on the tripod mast aft of the smokestack.
The issue with Breyer's depiction is that he appears to have had very little information to work with - likely just the caliber and number of guns - or in the case of the secondary battery, just caliber - leading to the necessity of making his own version of the project based on the written information he had. You can tell by the out-of-standard placement of the 2cm singles, the fact the tripod mast has no been moved aft (to match Scharnhorst), or even the use of the 128mm SK C/41. If you do not believe me, then by his own admission in the 1978 reprint of the book featuring numerous corrections and alterations, one of which is the removal of the old Gneisenau image above with the one below, as well as the following words:

"[In terms of upgrading only so far as the 38cm guns and 2cm AA] ...Any information to the contrary concerning the conversion of Gneisenau has not stood up to more recent rechecking and is therefore incorrect."
A strange way of admitting you fucked up and made a fictional fan-drawing, but sure enough this drawing does depict design K235/N4 for Gneisenau, created in 1942 and nowadays given the archive code of RM 25/15788:

https://drive.google.com/file/d/1yyFdI57jesEhwGuOy86KfPIvNqnmnzDn/view?usp=share_link

While it may be true that K235/N4 does not feature an altered secondary battery, that is not all there is to the story. In fact, there was actually a plan to replace the secondary battery with DP 128s. Garzke and Dulin's Axis and Neutral Battleships of World War II (not the best authors or most accurate book by any means, but still a generally good source) references this, stating the intention of the study was to source "recently developed" "127mm guns"* (this can reasonably be assumed to only mean the 128mm/61 Flak 40, as it entered production in mid/late 1941, and not the 128mm/45 SK C/41 as the latter would not face the issue of being claimed by other branches on grounds of priority, mainly because it is a weapon developed specifically for naval service) for use on Gneisenau, but the Heer and Luftwaffe claimed priority on the weapons - which were in very short supply, with only 1 being produced per month until mid-1944 - ending the idea almost as soon as it began.
In short, Breyer was incorrect yet again - and this, kids, is why you don't say anything with absolute certainty in a field where there is so much information yet to be released.
* = 12.7cm and 12.8cm were interchangeable in sources of the Wehrmacht, but actual bore diameter of most (if not all) German domestic production 5" caliber guns was 12.8cm.

Still, despite not having Flak 40 guns, to discredit the technical plausibility of the refit is wrong. Why is that? Let's discuss, but first: a developmental history of the gun in question:
"A Short Developmental History of the SK C/41 with Statistics":
In 1941 (thus proving that the KM was aware of and wanting the Flak 40 before 1942), a Flakzwilling 40 (Flakzwilling 40/2 or 42, depending on source) was returned to Rheinmetall-Borsig A.G. (the designer and producer of the Flak 40) so that the barrels could be changed out for shorter 45-caliber models capable of firing the 128mm/45 SK C/34's naval ammunition for use in turrets based on the Drhl C/38 twin. By the end of testing, the barrels had been shortened by just 30mm, the rifling to changed (to 1.7mm x 5.05mm versus 1.5mm x 6.0mm [SK C/34] and 1.7mm x 6.55mm [Flak 40]), and the mount lightened and decreased in size (most notably the guns placed much closer together for use in the new turret that was also designed in parallel with the gun: the Drhl C/41 twin). It is this gun that would be the 128mm/45 SK C/41.
The 128mm/45 SK C/41 is a semi-automatic, manually operated horizontal sliding wedge design with a lined barrel of 40 grooves (same as Flak 40) 1.7mm deep and 5.05mm wide. The gun is fired by an electromagnetic method with a backup mechanical firing system, features a brake hydraulic recoil cylinder + pneumatic knurler, and is loaded by an electric rammer. Horizontal and vertical guidance was also electrical. Also attached to the mount was a fuze-setting device. Most of these features are shared with the Flak 40.
Each gun weighed 4250kg, had an o/a length (includes breech) of 5807mm, barrel body length of 5400mm, and a rifling length of 4547mm. Working pressure is 2950 kg/cm2.
The "technical" rate of fire for these guns is 18 RPM per gun. In field tests with the Flakzwilling 40, rates of fire from a trained crew reached as high as 28-30 RPM per mount (14-15 RPM per gun). This is all well and dandy, but everyone tends to conveniently ignore the other factors, such as the rate of supply, endurance and training of the loaders, and operating environment (which would not be friendly on a rolling and pitching small destroyer turret).
The rounds fired are those from the SK C/34, pressed into a different cartridge and do not match that fired by the Flak 40. The ammunition is unitary. The two rounds are:

1. HE 12.7 cm Spgr. L/4,5 Kz (mHb) (Head fuse, ballistic fairing) [28 kg projectile, 49.0 kg o/a weight, 4.41 pounds/2.0 kg explosive filler, 10 kg RPC/40N propellant charge, 830 m/s MV, 22km range @ 40 degrees.]
2. HE (AA) 12.7 cm Spgr. L/4,5 Kz (mHb) (Time fuse) [28 kg projectile, 49.0 kg o/a weight, 7.05 pounds/3.2 kg explosive filler, 10 kg RPC/40N propellant charge, 830 m/s MV, unknown surface range, 12.2km vertical range at 70 degrees. 20-caliber projectile radius.]
3. Armor piercing ammunition was not supplied, though theoretically it could have been.​

The ammunition for the Flak 40 is as follows:

1. HE (AA) 12.8 cm Sprgr.Patr. L/4,5 (Time fuse) [26 kg projectile, 45.47 kg o/a weight, 7.47 pounds/3.39 kg explosive filler, 9.62 kg propellant charge, 880 m/s MV, 20.9km surface range, 14.8km vertical range.] Another source states a o/a weight of 47.4 kg for the round, 26 kg projectile, and 10.1kg of propellant charge.​

Both AA ammunition types are quite impressive, featuring good muzzle velocity (800+ m/s) and packing over 7 pounds of explosive filler, putting it's explosive weight on par with USN 5"/38 AAC rounds.
The Drhl. C/41 turrets are scaled down Drhl. C/38 twins and serve to lighten the turret both by making it smaller and reducing the armor to just 8mm (sides) - 10mm (face). On the Type 1936A/36A Mob ships, the armor for the Drhl. C/38 was 20mm (sides) - 30mm (face), however the weight reduction is apparent, going from 60.4t (occasionally 62t depending on source) to 40.5t. The guns were placed in a single cradle, and the reduction between the guns from 2325mm (Flak 40) to just 1500mm (C/41) caused a limited elevation of just 52 degrees - a downgrade from the Drhl. C/38's 62 degrees. Additional problems may be faced as the Drhl. C/38 faced issues with keeping water out of the turret, which had caused electrical shorts and faults. The addition of more electronics (such as the rammer) may exacerbate this issue if the mount is not sufficiently weatherproofed.
/end

With the 128mm/45 SK C/41 theoretically ready for tooling and then full production by 1942, it only became an issue with where to put the newly designed weapons. Of course, almost all new destroyer designs from 1941 and onwards would feature the new turret - it was designed for them, after all - but, as most know, only 2 of the designs that would feature it were ever even laid down, and nearly at war's end to boot, ensuring that demand for the production of the system remained low. The same issue was faced with the Drhl. C/38 for the 15cm/48 TK C/36, in design since 1937 (and presumably first constructed in 1938, hence "C/38") it did not reach service until 1942 as most of the designs that might have included it were cancelled (due to the outbreak of the war or in favor of another class) until the refits of the 1936A and the laying down of the Type 1936A (Mob) types.
Of course, that never stopped naval architects from drawing and designing, and with her planned rebuild in 1942-43, Gneisenu is in the perfect position to get the Drhl. C/41. Being essentially a Kriegsmarine-tailored Flakzwilling 40, the KM could now, basically, get the Flakzwilling 40 for their own "domestic" ends without having to fight the Heer and Luftwaffe (both much higher priority branches) for it.
But after this, it sort-of falls apart.
While there are a few Pros to this sort of idea (The ability to fit 16.66 [16] C/41 twins for the same weight as Gneisenau's original secondary battery, the AA-capable performance of all mounts, powered loading, a fully enclosed turret, etc) the cons come to bite much harder:

• The turrets are completely unarmored (8-10mm) and hardly what you would call splinterproof, making them highly vulnerable, nearly equally so to the 105mm/65.
• The turrets are small and cramped, reducing effective ROF and do not make better utilization of Gneisenau's deck space (by placing larger turrets to alleviate this) in a 1-for-1 swap.
• Maximum elevation is only 52 degrees.
• Training and elevation speed limited to 8.5 degrees/second (needs verification), too slow for a mount this light and of year of design.
• The turrets are not triaxial or (appear to be) RPC and would not make fully use of the RPC-capable triaxially stabilized SL-type directors.
• Although theoretically ready for production, production has not yet begun (or, it appears, even prepared for) as compared to the F.Z. 40.
• Possible additional weatherproofing problems by placing them at the weather deck level.
• Destroyers would have priority as it was a small turret with many concessions, designed for them specifically.

Even still it seems that the KM nor its newly designed weapons were completely free of the other branches - or at least the whimsical flirtations of Hitler with his mega-projects:

The P.1000 Ratte mockup as of October 1942, clearly showing the SK C/41 in Drhl. C/41.

In conclusion: There are better alternatives. The 128mm/45 SK C/41 and its turret are good in a pinch if it was the only option available, but there would have to be a concerted effort to get production rolling and an acceptance that, in a combat situation, these turrets are highly vulnerable and may not perform as expected.

Speaking of alternatives.

Most even slightly familiar with Kriegsmarine design will more than likely at least be aware of WarGaming's tier 7 battleship Gneisenau from World of Warships, so, while we're here, why not discuss that too?

---

The WarGaming Model
Gneisenau in WoWs, represented by the "B" hull, features 11* Drhl. C/38 twin turrets. These turrets, designed for the larger 15cm/48 TK C/36, have been re-armed with the 128mm/61 "KM40" (Flakzwilling 40). In addition to the alterations to the secondary battery, WG have also re-arranged the superstructure and enhanced the AA in their typical way (that is, to say, badly).
In spite of that, the concept of WarGaming's Gneisenau secondary battery refit model is actually much better than what your typical elitist would give it credit for, the very same who would scoff at even the thought that a WG creation might have been decent - and to be honest, it's not entirely undeserved, but this is one of those exceptions.
...Wait, what are you doing with that pitchfork and torch? Wait, I'm sorry! Put it down! I'll apologi- screaming
* = Gneisenau could accommodate a maximum of 14.7 (15) 128mm/61 KM40 in Drhl. C/38 turrets for approximately the same total weight as the 15cm and 10.5cm turrets they replace.

So why is this WarGaming version of the Gneisenau 128 DP secondary battery "good"? This design matches the assumed gun type and thus meets the most basic criteria, automatically putting it ahead of the Breyer Proposal, but before we get to the core reasons why, let's discuss the Pros and Cons of using this gun and turret combination:
Pros:

• Turrets at least have a small amount of armoring, enough to stop some small-caliber HE rounds (on the face plate) and splinters from larger caliber weapons (all areas). The armor values match that of the Konigsberg-class cruisers, and is much greater than that of, at least, the 10.5cm/65.
• Turrets are described as large and "roomy" even despite the large 15cm breeches occupying the interior. Even with the 61-caliber Flak 40 being slightly longer than the 15cm/48 (7.835 meters vs 7.165 meters overall) (25.7 ft vs 23.5 ft) the actual space taken up inside the turret would not be significantly more, if at all, even with the electric rammer attached. - and if it was, only longitudinally. An idea can be garnered by viewing this image of the 15cm in Drhl. C/38
  

• Turrets are small enough to fit comfortably in large numbers, but not too small as to be uncomfortable to crew.
• Maximum elevation is 62 degrees. Not optimal, but adequate for AA use and an improvement over the SK C/41.
• Turrets have already entered service as of 1942 with construction of such mounts dating back to 1938.
• Existing turrets could be easily modified or turrets in production altered to better accept the 128mm/61 with no negative impact.
• Destroyers have returned to the 128mm SK C/34 or moved to the SK C/41, leaving this turret design without a priority.
• Turret is fully enclosed and largely protected from the weather.
• Powered loading is included.
• Superior ballistic performance (MV, range, etc) to other 128mm guns, and features a slightly larger bursting charge.
• The same turret was intended for use aboard the O-class battleships both at the weather deck level and a deck above.
• Training and elevation speeds are 8 degree/second, slow but equal to 10.5cm/65 C/37 mounts. This number may improve with the significantly lighter 128mm gun replacing the 15cm/48.
• A couple of (largely unsubstantiated) sources have stated it was the intention to move the 128mm/61 into this turret for testing, using guns placed around major port cities (such as Kiel).*

* = One Flakzwilling 40 was provided a turret called the 'Dopp L (Pzk) C/40' which is described as being armored and had funnel shields to catch fragmentation from a barrel burst. What this turret looks like, or even is, I do not know. All I do know is the Kriegsmarine provided for it. It may be a land-based alternative to the Drhl. C/38, but until I see it, I cannot say for sure.
Cons:

• The turrets are not triaxial or (appear to be) RPC and would not make fully use of the RPC-capable triaxially stabilized SL-type directors. Perhaps the turret could be made with some amount of RPC, but that would take time and weight and would not make the guns any more triaxial.
• Possible weatherproofing problems by placing them at the weather deck level, especially bad on low-sitting ships such as the Scharnhorst-class. Weight removed by the use of 128mm will necessarily be eaten away at by additional weatherproofing.
• Ammunition supply rate is far too slow at just 8 rounds per minute per barrel, necessitating an improved ammunition elevator such as that of the Drhl. C/41 (15 rounds/minute/gun electric-driven) eating again away at saved weight and taking time.

As you can see, the Pros certainly outweigh the Cons, much more so than the 128mm SK C/41 used in the Breyer Proposal, and even the Cons are not things that cannot be overcome with some minor edits (with the exception of triaxial stability or the making of holes in the decks). Even if the weight savings obtained by using the KM40 over the 15cm/48 TK C/36 (Drhl. C/38 w/ KM40 = 52.87t vs 60.4t with 15cm/48) was eaten up entirely, one could still replace the entire secondary battery 1-for-1 and still only break even.

In conclusion: It is the perfect design for the Kriegsmarine in a pinch if they got their hands on the F.Z. 40 for Gneisenau, according to plan - "Kriegsmarine in a pinch" pretty much describing the KM ever since the war broke out. Out of all the turret and gun options, it is the most rapidly sourced among them, requiring only minor modification, already in production, and all-around well-suited for DPAA work as a secondary weapon compared to the 128mm SK C/41.
For the Kriegsmarine, it's all about what could be sourced quickly - there's a war on (or if 1938/39, would be very soon), and you have to use what you have, even if it isn't the best thing. Sometimes that begets creative and otherwise unorthodox solutions, but it generally will consist of things already in production. You will see this reflected in almost every German design from 1938 and on and is just part of the nature of the beast. So, as odd as it might sound, WG nailed their Gneisenau secondary battery refit on the head - and it looks good to boot.

But it's not the most optimal choice.

So what does the most "optimal" possible secondary refit look like? Here's my suggestion:

---

The Sarcasticat Proposal
A few of you probably already know where this is heading, but still, let's discuss.
So if the 12.8cm SK C/41 and Drhl. C/41 and the Drhl. C/38 turret are out of the picture for the F.Z. 40, what's left?

Well, during mid-to-late 1940 and early 1941 there was a series of high-elevation triaxial enclosed turret designs (read: big 10.5cm twin mount) for a "12.7cm Doppelflak L54". Upon closer inspection, it is obvious this is just a shorter 128mm Flakzwilling 40. Whether this is because the KM expected to shorten the 61-caliber barrel to reduce weight (most likely) or because at this time the length of the barrel has not been determined (less likely), it is still clear to see that, with the issue of production not forthcoming at the time, the KM figured that it would have access to a larger number of the 'intermediate caliber' weapons that underwent testing in 1938 and was nearing its final form in late 1940 and as such made a series of pre-emptive designs for twin turrets.
The name of these designs is unknown, but "LM40" is already taken, haven been given to the coastal mounts. Given the date of the final design we have being very early 1941, a prospective name might be "LM41". The guns had an elevation of +85 deg and could depress -10 deg, but other specifications (such as elevation/training speeds, weight, etc) are not known or were not created. However, one can guess that the weapon would be immensely weighty - upwards of 60t with train and elevation speeds somewhere in the ballpark of 10 deg/s. This is a design meant as a large secondary weapon.

The final rendition of the 12.7cm Doppelflak twin turret design, 22 January 1941. For those of you who find this turret familiar, you can find it on some high-tier German ships in WoWs (Preussen, Clausewitz, and Hannover, for example).

For Gneisenau this is about the best that would ever possibly be available - that we currently know of - and despite the unfavorable weight estimate the ship could still handle a 1-for-1 swap and break even with the original 15cm/10.5cm battery weight.

Let's discuss the Pros and Cons:
Pros:

• Turret is slightly larger than the Drhl. C/38 (5.78m long x 3.4m wide for C/38 / 5.6m long x 4.0m wide for LM40)
• Maximum elevation is 85 degrees, perfect for AA work.
• Turret is fully enclosed and protected from the weather.
• Powered loading is included.
• Superior ballistic performance (MV, range, etc) to other 128mm guns, and features a slightly larger bursting charge.
• Gun is triaxial and no doubt will have RPC capabilities, making the most use of pre-existing SL directors.

Cons:

• A lot of information is unknown, which makes it difficult to quantify how good or bad it truly is.
• Most likely of all turret options to suffer at weather deck level from waves and sea spray (corrosion, electrical faults, damage, etc).*
• Unsure if the design work has been completed, production is nowhere near beginning, and no prototypes exist, although it appears that there were efforts underway late in the war to get a turret like this, known as the 'Dopp Flak LM44', going.
• An extremely complex and delicate-looking mount which may take significant R&D time unless heavily prioritized.

* = The electrical faults and corrosion noted in regard to the 10.5cm/65 by authors is far more unsubstantiated (and in some cases just plainly propagated info) than one might think; in fact, there is only one War Diary entry found that makes note of any sort of damage or faults to the 10.5cm and that is only after Scharnhorst had brute-forced her way through a large Atlantic storm causing all sorts of damage topside, to include her 10.5cm battery. However, placing a bigger version, even if designed as an enclosed mount, at weather deck level is just asking for trouble.

As you can see there isn't a lot to write about because there isn't much that is known. In theory, if this is just an enlarged version of the 10.5cm with some additional features, one might expect to see similar levels of armor, comparable train and elevation rates (at least to the 10.5cm C/38 mount), and overall good performance - just at a larger scale. The main issue comes with production, but at least the design dates to 1940 (or latest known, Jan. 1941) which means that it has at least reached paper in a detailed form even if no prototype turrets were made (to our knowledge). However, there is no getting around this production issue (prototyping, tooling, etc) unless the turret has priority and it is certain the KM can attain the F.Z. 40 to mount to it, leaving this proposal dead last in terms of production potential - even the 128mm SK C/41 is slightly ahead due to finalized turret design, mount prototype, the like.

In conclusion: It's the most optimal and reasonable turret for the job, it just needs to get produced. But for 1942-going-on-43 Germany, that's quite a tall order, even if it was as simple as "make 10.5cm - but bigger".

---

Conclusion.

Some people on the internet say that the Drhl. C/38 turret is intended to be the stopgap measure until the triaxial mount ("LM40") (or perhaps LM44) could be produced, which, regardless of truth, makes the most sense when you think about it. In 1943 the C/38 is the only available HA turret or mount of any type that the Kriegsmarine has in production that could take the 12.8cm F.Z. 40/KM40 if they were to receive a batch that year. With the war tipping out of their favor and the disastrous Battle of the Barents Sea (31 Dec 1942) causing Hitler to call for a complete removal of all his capital ships (from existence), it suddenly becomes that much harder to substantiate the worth of getting such a complex turret as the "LM41"/LM44 on short notice. This is probably why only design work was underway when the war ended.

So in short that leaves us with this conclusion: The "LM41" is the most optimal turret, the C/38 is the most realistic and practical, and the SK C/41 is the choice the KM would make if they couldn't get their hands on the Flakzwilling 40 but still wanted to proceed with a secondary battery change.

But I guess K235/N4 trumps all of them because it's the only drawing we have on paper.
Well, maybe there are more drawings of proposed secondary battery changes, or more discussions in books somewhere, but we don't have those yet. Maybe one day.

Whew, another full day taken to revise this! Hope someone learned something.

 

[lukasgrul]

Do you have any blueprints of smaller aa guns like FLAK 103/38 and some else?

 

[TomS]

Was the Walter turbine drive a viable option for submarines or it was a dead end? Did any navy continued it's development post-war?

The RN built two experimental HTP/steam turbine submarines after the war -- HMS Explorer and HMS Excalibur (known to their crews as Exploder and Excruciator). They were not well-loved or successful.

Explorer-class submarine - Wikipedia

en.wikipedia.org

The Soviets also built a single Type 617 (NATO: WHALE) class sub. It too suffered a significant internal explosion and was abandoned as a concept.

H I Sutton - Covert Shores

 

[_Sarcasticat_]

Hello everyone.

I just updated the big Gneisenau post. It should read much better, with new/revised information as well as information concentrated where it should. Any other questions I am standing by to answer. If anyone can find that F.Z. 40 coastal armored turret described (Dopp L (Pzk) C/40) please let me know.

Speaking of revisions, I am going to begin working on a series of revisions and alternate proposals to my Modernized Derfflinger concept and after that I will work on the Deutschland rebuilds and will feature a very special set of plans in regard to that.

If anyone has any sort of Shipbucket or other art experience, is willing to spend a lot of time, endure a lot of nitpicking and changes (literally dozens), and is otherwise capable of putting up with me, please feel free to DM me here or on Discord so that I may have more than just words for these write-ups. My standards are deep, but so are my pockets if you know what I am saying.

Thank you for reading.

Edit:
For convenience, here is the image and the associated text for those who do not like to click links:

Spoiler: Modernized Derfflinger

A fictional design that follows what Derfflinger might have looked like after an extensive rebuild and modernization approximately from 1937 through 1940. This design assumes that very little has changed in the history of the Weimar Republic and the eventual rise of the Nazi Party in Germany and as such reflects the question of: "What would a rebuilt Derfflinger in the Kriegsmarine look like?"

Following the Treaty of Versailles and the subsequent loss of the vast majority of her fleet, Imperial Germany was left with but a token navy largely incapable of even basic defensive measures against her former wartime enemies. For capital ships the Reichsmarine was limited to just six active pre-dreadnought battleships of no more than 10,000 tons (2 in reserve), and this limitation to number and weight included any potential replacement designs which would crop up as the minimum time of 20 years before replacement came around. But what if, for whatever reason you might imagine, a Derfflinger was allowed to survive by fate and enter service in the Reichsmarine? To facilitate this reality, perhaps we could say that the Weimar Republic was given a little more freedom; allowed to utilize 60,000 tons for capital ship displacement and to choose from ships which had already been constructed with the rest being sunk, scrapped, or passed to victorious powers with Scapa Flow being avoided. A token navy of less than four meaningful capital ships, but better than being saddled with six pre-dreadnought battleships. Today, we will assume that the Iron Dog herself is among the few that the infant Weimar Republic is allowed to retain.
However, a little more freedom does not allow the Reichsmarine to escape the reality of its financial situation nor the intense scrutiny of the Naval Inter-Allied Commission of Control (NIACC). Unable to afford to refit the ships throughout the early 20's due to hyperinflation and with an even greater chokehold from the Commission of Control throughout the latter half of the decade due in large part to the still-capable nature of the battlecruiser's design, any work to improve the combat aspects of the ships was almost exclusively rejected. That is not to say that no work was done, as the design of the Derfflinger class did not envisage long-ranged cruises outside of the North and Baltic Sea some alternations to the internal structure (such as removing the underwater torpedo tubes) and quality of life were required to improve long-term habitability. She proved to be an incredibly popular attraction abroad, and the subsequent modifications from initial feedback laid the groundwork for what she was to become later in her lifespan.
By the rise of the NSDAP in 1933, the aging battlecruiser was nearing twenty years of service herself. Despite this the legendary status of the ship, the tried nature of her construction, and the relaxing grip of Allied observers made discussion for refits and modernizations an inevitability. Initial plans were rather conservative in nature, envisaging a simply redesigned superstructure with a tubular mast and replacement of coal-fired boilers with oil-fired models among other small alterations. Given the limited nature of these changes, work commenced and was completed in short order, but things had escalated rapidly when Adolf Hitler renounced the Treaty of Versailles in 1935 and calls for a more comprehensive modernization effort - a rebuild - strengthened significantly - especially in light of the limiting Anglo-German Naval Agreement where Derfflinger was much less likely be passed off for new construction. Such calls were still debated furiously, as the envisaged extensive rebuild would take the ship out of service for years and the expenditure in material and marks might overrun the worth of such a venture. Regardless, the final nail needed for "proof of concept" and to convince Hitler came in 1936 when the British battlecruiser Renown was docked for a rebuild not dissimilar to the one ongoing with Warspite. Simply put, if every other country was going to rebuild their Great War warships, so was Germany. Those calling for the rebuild were soon gratified and design work began the same year.
Designers within the Konstruktionamt took inspiration from ongoing rebuilds from what would become their future allies: Italy and Japan. Not willing to go as far as the Italians were with the Conte di Cavour-class, and only partially inspired by what Japan had done with their Kongo-class, the year-old Kriegsmarine settled upon its own path which, ironically, nearly paralleled that of the British. Several sketches and designs were drawn up with a wide variety of levels to the complexity of the rebuild, but perhaps the most popular one among them is the one we will discuss today which drew heavily from Scharnhorst's construction plans and to a lesser degree those of the Panzerschiffe. The intended goal was to produce - by Kriegsmarine standards - a conventional multirole capital ship with similar performance to the Scharnhorst-class, capable of engaging or disengaging with enemy warships as well as commerce raiding in the Atlantic.
The reconstruction effort began in early 1937 with the complete replacement of the ship's old steam plant with that of the Scharnhorst-class, rated at 125,000 shp with an eventual proved output of 160,000 shp at overload. The process was facilitated by the removal of the funnels, parts of the superstructure, and cutting holes in the casemate and weather decks to allow for easier removal and installation. What would typically have been the central turbine was forced to be split into two units to support the pre-existing four shaft arrangement. Such a measure as reboilering was undertaken as a direct response to the Dunkerque-class as well as to the overall increase in speed shared with new battleship designs. Derfflinger would require an increase in speed to be capable of closing or disengaging with the fast French battleships (and with other battleships in general), and no matter how thoroughly refurbished, her original plant was incapable of providing that. A large central funnel was placed roughly between where the originals had been, and the base was kept narrow by keeping the 12 boilers closer to directly underneath the funnel.
Also undertaken during this initial period was the choice to up-armor the ship in specific areas. The armored deck was increased in thickness over the magazines and machinery spaces utilizing Wotan hart (Wh). Magazine protection was increased to 80mm while the machinery spaces were increased to 50mm, now equivalent with the turtleback. These values were intended to allow for the armored deck to resist deck penetrations from the French 33cm/50-caliber gun at ranges of 20km and 15km respectively. Due to concerns with time, cost, and the mounting weight being applied to a ship already rather low along the waterline, armor increases elsewhere were otherwise kept to a minimum.
Being so close to the waterline as the weather deck was, any increase in topweight that might be imposed by the addition of an extensive superstructure, secondary battery, AA, and electronics would prove dangerous to the seakeeping of the ship in the rough Atlantic waters. As the secondary battery had already proven wet, especially on the Derfflingers, it was decided to remove the casemate armor as well as the 15cm guns and convert the internal space for alternative uses which might prove vital in long raiding cruises (aircraft, torpedo, and metal workshops, crew spaces, galley, etc). Casemates had already been, rightfully, deemed obsolete by other navies (with the exception of Japan, who appear to have been behind this curve) as they lacked the operational freedom of turret-mounted weapons and required too much additional weight spent to protect them. The Kriegsmarine had already come to this conclusion during the design of the Bismarck, and there was no love lost when in OTL the pre-dreadnoughts systematically had their secondary batteries removed. Thus, with the removal of this weight, several hundred tons of topweight was freed to "spend" on necessary improvements to make Derfflinger a formidable rebuilt and modernized capital ship.
The most major of these was the superstructure and electronics. Although it may not appear so, the new superstructure was built off the old, occasionally having to cut it to shape at the base before building vertically. It was decided to build a full capital ship superstructure rather than settle with half-measures such as that of a cruiser-based variety. Although that alternative might have saved some weight, it did not provide the proper facilities required for a ship of her caliber. Regardless, measures to reduce the size and height of the structure were taken where possible. Given that both of the original funnels had been removed, the large tubular command structure has taken the place of the forward funnel while the lower operational base (including the conning tower) has been built up from the original. Further back, where the aft funnel had been, was a new aft rangefinder platform which was built on top of the existing structure.
In keeping with the attempt to maintain at least some parity with the armament of the Scharnhorst-class, efforts were made maximize the secondary and AA armament on the smaller displacement and size. Four twin 15cm/55 SK C/28 turrets with the "short-trunk" design (as seen on the outer twin 15cm/55 on the Bismarck) were utilized, and although it was decided upon to retain the casemate structure, it was necessary to cut into it to provide proper firing angles for these turrets. 15cm/55 guns in single MPL C/28 mounts were considered to bring the broadside up to six barrels, but dropped when both limitations of deck space and weather were factored in. The fully enclosed nature of the twin turret made it far more operable despite the sea than its open single counterpart. Four barrels per broadside was deemed satisfactory, and this is reflected in other Kriegsmarine capital ship raider designs. On the other hand, with some amount of cramping, seven twin 10.5cm/65 SK C/33 mounts were supplied - though it should also be mentioned that Scharnhorst faces a similar, even comparatively worse, problem in terms of crew workspace. Seven mounts were chosen over eight as it still provided the same broadside firepower but reduced weight and still complied with the 2:1 ratio of mounts to directors, a ratio that was followed in most German large warships with the apparent exception of the Hipper-class.
The modifications to the turret tops of B and X turrets were not a part of the original designs, but had been included following an assessment that the interior of the turrets was too small to provide adequate space for a modern large turret-mounted optical rangefinder and had to be placed outside of the existing structure in some manner. Some cheaper, less well-protected options were discussed, but as it became clear that the ship might be operating alone in the Atlantic it became increasingly imperative that the rangefinders - which might end up the only method of fire control (as it nearly had for Graf Spee in 1939) - be properly protected from enemy shellfire. Again, options were discussed until a modified peaked roof design taken from the Admiral Hipper was put forth and ultimately accepted as the two turret designs shared a similar shape for the non-rangefinder variants. Otherwise, the training motors were replaced with improved models and the ammunition hoists improved in much the same way to allow for a slightly higher-than-usual rate of fire of 3 rounds per minute. All turrets were modified for increased elevation.
AA consisted of 8x2 3.7cm/83 SK C/30, 12x1; 2x4 2cm/65 C/38, and the DP AAA of 7x2 10.5cm/65 SK C/33 guns in 1940 when she completed her rebuild. This design reflects an AA upgrade in 1942 to where she now has 4x4 placed atop her 15cm twins, providing an equal distribution of fire in each AA sector (Scharnhorst had her AA sectors divided into four quarters) as well as an additional two singles placed on the forward rangefinder platform. Every effort was made to keep the larger 3.7cm and 10.5cm guns off the weather decks and far away from the corrosive sea.
The catapult and aircraft were placed aft in what can be considered the most un-German fashion. This was borne out of necessity rather than choice as the length of the ship and the required structures amidships did not permit for a catapult and aircraft there. For instance, on the aft deckhouse, the aft rangefinder, mast, and 10.5cm twin take priority over the catapult and aircraft and forcing it to be displaced. It was still believed to be a necessity, and aft catapult designs were not entirely unheard of in the Kriegsmarine, so as such it was given its home on the stern. Flight crew were specifically ordered to weatherproof the aircraft while not in immediate use and conduct constant cleaning and maintenance to keep the aircraft in good condition as the stern of the Derfflinger-class is known to become very wet as it digs into the water at high power (and this is before considering the increase in output the new steam plant provides).
There are many other changes that did not appear on the original designs but were added to the final draft as completion approached in 1939-40. These include the alteration of the bow to that of a clipper (or 'Atlantic') type, a funnel cap, improved rangefinder models (10.5m with FuMO 23), and two quadruple covered torpedo tubes. The bow was not altered below the waterline as the original hull shape was designed as such to increase steerageway and already conforms with the pre-existing hydrodynamics of the hull, but above the waterline an increase in sheer and the addition of the Atlantic-style bow increased buoyancy forward and helped to alleviate any potential issues with seakeeping such as those experienced with the Scharnhorsts. Funnel caps were a common trend by the later stages of the rebuild and the addition of one was seen as unlikely to add any significant time. The two quadruple torpedo tubes were supplied to provide additional close-range power and were covered to protect them splinter damage as well as from the sea, similarly to the Deutschlands.
A lot of effort went into weatherproofing. Many wavebreakers were placed forward, the 3.7cm guns at the casemate deck level were placed in tubs, the torpedo tubes were covered, and even the 10.5cm guns have additional shielding to protect against sea spray. Such measures were deemed necessary as even with the removal of over 700 tons of weight topside the weight budget was quickly eaten and surpassed with new additions and as such was forcing the ship lower into the water. But many of these changes were required to create a competitive capital ship out of such an old design and any penalty to seakeeping they incurred was accepted.
Derfflinger performed exceptionally well during her trials, hitting 30.5-31 knots at her rated horsepower and over 33 knots when at overload. In service she could maintain a higher sustained maximum speed than potential enemy battleships and were capable of even giving chase to most light cruisers, particularly in her sprint. Her 30.5cm guns had been provided with a properly modern APC round which increased the effectiveness and range of her main battery and her suite of secondary weapons were equally worth praise. Her rebuild had taken approximately 3-3.5 years and had resulted in a large improvement to the capability of the ship. The most major flaws stem from the typical troublemakers: low freeboard, complex and permanently-over pressured machinery, and wetness while in the Atlantic. Regardless, the ship was considered a success.

 

[_Sarcasticat_]

Do you have any blueprints of smaller aa guns like FLAK 103/38 and some else?

Some. I can provide for the 3cm Flak 103/38. (Technical data and the like) and some small low-resolution photos. Unfortunately all the great data books for the MK 103 from deutscheluftwaffe.de have not been uploaded from the old site as of right now and I do not have them. I wish I could find someone who has them, they are an unbelievably excellent resource.

 

[lukasgrul]

Thank you very much

 

[DE1083]

Did the various tri-axial mounts/turrets have any significant advantage over the more standard mounts?

 

[Imidiot]

I've saw 40.6 cm/52's reloading speed only about 30 seconds while 38 cm/52 SK C/34 can reload in 20 seconds technically. Is it record for 40.6 cm/ 52coastal version(what really made) so naval version(which is only designed) is faster or just naval version has slower reload rate than 38 cm?

 

[_Sarcasticat_]

I've saw 40.6 cm/52's reloading speed only about 30 seconds while 38 cm/52 SK C/34 can reload in 20 seconds technically. Is it record for 40.6 cm/ 52coastal version(what really made) so naval version(which is only designed) is faster or just naval version has slower reload rate than 38 cm?

It may be that the 40.6cm's noted reload time is 30s because that is the average while you are comparing the 38cm's fastest time. However, if the weight of the projectile and powder + case are taken into account in regard to the ammunition elevation motor and rammer, the 40.6cm SHOULD be capable of reloading at that speed.
However, technology is often limited by the times, meaning that you may see a reduction in reload speed as one might expect.

 

[_Sarcasticat_]

Did the various tri-axial mounts/turrets have any significant advantage over the more standard mounts?

Yes, they did. It improved accuracy considerably even if rangefinding was still done optically (it wasn't until about 1944 for Germany that they fitted the Wurzburg-D anti-air radar to an SL director).

 

[Colonial-Marine]

I'd have to guess that being limited to 52 or 62 degrees of elevation is going to be a pretty severe limit on the utility of heavy AAA. Once dive bombers get past the outer flak radius they could take all day above the target forming up for an ideal attack. Same with heavy level bombers.

Even if the war was going a lot better for Germany I'd imagine that realistically they would have waited for that final turret design using either the 128mm/61 caliber Flak 40 or a shortened 54 caliber version of it.

Going off the tables on Navweaps it seems like the shells used by the 128mm/45 caliber SK C/34 and SK C/41 have a slightly greater range at 45 degrees than the shells of the Flak 40 despite the significantly higher muzzle velocity of the Flak gun. I wonder if that is an error.

 

[_Sarcasticat_]

I'd have to guess that being limited to 52 or 62 degrees of elevation is going to be a pretty severe limit on the utility of heavy AAA. Once dive bombers get past the outer flak radius they could take all day above the target forming up for an ideal attack. Same with heavy level bombers.

Even if the war was going a lot better for Germany I'd imagine that realistically they would have waited for that final turret design using either the 128mm/61 caliber Flak 40 or a shortened 54 caliber version of it.

Going off the tables on Navweaps it seems like the shells used by the 128mm/45 caliber SK C/34 and SK C/41 have a slightly greater range at 45 degrees than the shells of the Flak 40 despite the significantly higher muzzle velocity of the Flak gun. I wonder if that is an error.

The turrets traverse and elevate too slow to be useful at close ranges - and that applies (or is likely to apply) for all of them, sans potentially the LM44. The only ships that would not be capable of being engaged are dive bombers/level bombers at closer ranges, but those are typically engaged by 2cm and 3.7cm Flak at that point, which are far more effective weapons for close-in engagement and exactly why they exist. 62 degrees is adequate to engage aircraft in the outer and medium-distance zones. 62 is actually higher than most think.

Just because the elevation is not 75 degrees+ does not mean that the elevation is insufficient in the role it was intended for, especially given the date of design, size of the turret, and the weapons intended to be housed in them

Maximum surface range does not matter as much as maximum vertical performance or, much more importantly, effective range, with the latter being determined by and large by muzzle velocity. Even in naval battles, given the close ranges destroyers typically fight at, the higher muzzle velocity would be welcome. No destroyer is going to be firing at maximum range (with anything resembling effectiveness) as their small little 3-to-4 meter rangefinders cannot support it. Even the case the Flak 40 is used as a secondary weapon, its other role as anti-surface would see it firing at incoming destroyers at light cruisers which will attempt to close the range rapidly for torpedo runs.

It is not an error. You can determine this by studying the projectile weight. For the naval guns, it is 28 kg. For the Flak 40, it is 26.0 kg. This means that the lighter round will bleed off energy more at longer range and in trade it obtains greater muzzle velocity, which is key to accurate anti-aircraft fire because the chances are that you will not always be using maximum range because aircraft, bombers in particular, are not very accurate at those heights during this period.
Note: a similar (but not exactly so) principle is in use for Minengeschoss found on 2cm+ weapons.

And, of course, if you want to dive without breaking off your wings in the break-off or survive long enough to drop your bombs, you won't be diving from 12+km.


My final conclusion about the Flak 40 in C/38 is that is more than sufficient to be utilized in place of the "LM41" or LM44 and is more effective than the destroyer-tailored SK C/41 in Drhl. C/41.

If, and I am not saying you are, but if you are wondering why the KM uses 28kg if they are 'so much more ineffective', re-read the section regarding the developmental history of the SK C/41, in particular the section regarding projectiles.

 

[_Sarcasticat_]

Uploading a lot of RM6 stuff to the drive.

Upload complete.

RM_6 Folder - Google Drive

drive.google.com

@lukasgrul I'll get your 3cm stuff as soon as I can.

 

[_Sarcasticat_]

Hello everyone, I'm back again.

Today's topic is the Deutschland rebuilds. / and me throwing a bunch of diesel engine development at the screen because I can't help but explain every little facet and detail.

This series of rebuild concepts and proposals that was to encompass only Admiral Scheer and Admiral Graf Spee at first, but grew to include Deutschland.
The genesis of the oft-unknown Deutschland rebuilds starts with the lessons learned at sea with the class over the 1930's, and in particular that of the Spanish Civil War where the Kriegsmarine came to truly understand the issues of their Panzerschiffe steaming outside the relatively calm North and Baltic seas from which they had been operating from a majority of their service lives.

Koop describes in his book Warships of the Kriegsmarine: Pocket Battleships of the Deutschland Class the types of issues faced, and the beginnings of creative solutions to solve them, in this paragraph:

Experiences obtained during the prewar oceanic voyages, such as the South Atlantic cruise by Deutschland, the gunnery trials in the western Atlantic and operations in Spanish waters, suggested the need for limited modifications to the ships. Beyond the relatively short chop of the North Sea and Baltic, the Panzerschiff proved to be very wet forward, and at high speeds the stern tended to dig in, leaving the quarterdeck constantly awash. Topweight was another problem, particularly in Admiral Scheer and Admiral Graf Spee with their pagoda-like battle-masts. Suggestions for the reduction of the secondary armament by four gunhouses, the straight exchange of the secondary armament for twin 12.7cm multi-purpose weapons and doing away with the shipboard aircraft installation were rejected and eventually the idea rebuilding the two later units and replacing the existing battle-mast with a tubular mast similar to that aboard Deutschland came into favour. The raising of the lateral bulges to the upper deck level to improve the the side armor was planned, together with other modifications such as installing radar, improving the ship's wireless system, adding shipboard aircraft, stabilising the searchlights, supplying splinter shields for the small-caliber weapons and strengthening the foundations for the motors. These modifications would in total have amounted to little more than 70 tons extra weight per ship.

The issues described are somewhat similar to the very same as those faced by some Kaiserliche Marine in the First World War: wet bows, sterns awash at high speed, the like. The large cruisers of the Derfflinger-class suffered these two issues listed in particular, which is not surprising given that a lot of basis was taken from Imperial-era design when the Reichsmarine first truly began to rebuild in the mid-20's.
The solution at first was a relatively simple one: reduce the secondary battery to just four (rather than eight) 15cm or alter it to an intermediate DP caliber (12.8cm) and remove the aircraft, thereby reducing topweight. However, as it will be said in later excerpts, the Panzerschiffe are too valuable to just reduce their combat capability for manners such as improved seakeeping (not seaworthiness). The solution would then be to "lighten up" the unnecessarily massive Star Wars-esque battle-masts on Scheer and Spee by cutting them down and making them tubular.
The "raising of the lateral bulges to the upper deck level" idea is reminiscent of Karlsruhe's 1938 rebuild which served to enhance her structural strength, seakeeping, and armor (in particular against sub-6" caliber projectiles). Here you can see Karlsruhe before and after conversion:

The primary difference between Karlsruhe and the Deutschlands was that instead of fitting a new exterior, the larger cruisers were to extend their side bulges upwards. Here is a photo to illustrate what I mean:

Again, the quote was: "raising of the lateral bulges to the upper deck level". A translation into simpler terms being: Moving the side bulges to the uppermost deck that stretches all the way fore and aft. That would be the deck (highlighted in red) from the above photo where the bulge has been raised to. Here is another illustration for clarity, deck colored red to match the above illustration.

The usefulness of such a decision as this is hard to quantify as there are no steel thickness values shown for the bulges. This means that there is an addition of weight above the waterline for only a potentially very small increase in protection. But I suppose any addition in protection is a good one, no? Even 10-15mm would be a great improvement on top of 80mm. Raising the bulges should also add to hull volume, increasing buoyancy and seakeeping characteristics (as so far as my imperfect understanding concludes).
Radar to be installed was, as of the early planning stages in approximately 1938, likely the FuMG 39 (gO) but later (approximately 1939+) to have fitted a full FuMO 22 or FuMO 27. According to Koop/Schmolke, the FuMO 22 is a gunnery radar of 81.5cm wavelength, 500 kHz frequency, 8 kW output, 368 MHz frequency for a 14-18km range with +/- 3 degrees of bearing accuracy. According to Die Deutschen Funkmessverfahren bis 1945 (a much more believable source) the range for the FuMO 22 as installed aboard Scharnhorst/Gneisenau, Admiral Hipper/Blucher, and Admiral Scheer/Deutschland was 25km to battleships with a bearing accuracy of +/- 5 degrees. The statistics from Koop/Schmolke are identical to those of the FuMO 21.
In addition to the new radar, stabilization for the searchlights was to be provided for which would be beneficial in night actions, especially against small fast craft such as motor torpedo boats or destroyers who might otherwise be lost as the ship heaves and rolls in turns at high speed and/or in high seas.
Splinter shields for AA is an underrated improvement that, if anything, provides solace to anti-aircraft gunners that the shield will provide some measure of protection against strafing fire, splinters, etc, allowing them to further focus on their duties instead of fearing for their lives in their wide-open mount and serves to increase overall survivability as well as effectiveness. Germany was behind the curve on such developments - at least for light AA, not really making any attempts to amend this until the latter half of the war.
Perhaps the most important of all these improvements is the strengthening of the motor foundations. Heavy vibration, excessive noise, constant maintenance, shorter operating times and more plagued these early engines, being in 1933 a relatively new and untested technology, especially at this scale. Thankfully there was a fix for biggest problems (vibration and noise) which was to increase the strength and rigidity of the motor's foundations. This served to increase the integrity of the engines (without making them individually heavier, thereby reducing their power to weight ratio). This would prove to be a critical aspect of maintaining the health of diesel motors in the postwar era.

Now that we have gone through an introduction to the problems of the Deutschland's machinery, let's take a deeper dive on how exactly they've become so relatively "common knowledge" to the point of even being picked up in modern "Pop History":
In short, these days the issues of the Deutschland's propulsion plant (such as those described in the paragraph before last) are rather well-known, but what most do not know is that a lot of these problems have been exaggerated wildly on purpose, and as such has forever tainted the legacy of a revolutionary ship and her unique engine system with the effects of such still being felt in today's "Pop History". The Deutschland-class had been a pioneer design which had beyond proved the usefulness and practicality of such systems overall in spite of the initial teething problems, thus leading us to the modern age of gas turbines and diesel engines. But to fully understand the circumstances surrounding the rise of the diesel engines aboard large warships it is necessary that we go on a long tangent to explore the history of German naval diesel development and its interaction with its direct rival: steam.

Spoiler: A Very Short History of MAN Diesels 1928-1945

Let us again refer to Koop:

A large part of all refit work involved the ships machinery, and this always provoked a fresh outbreak of virulent criticism directed at the diesel engines. It is true that there were difficulties initially. But to lay blame on the manufacturer was as reprehensible as to pretend that the engines were perfect. In Works Circular No. 5012 entitled 'Rumours about MAN Diesel Installations aboard the German Panzerschiffe', issued at Augsburg on 24 January 1935, the company drew attention to the fact that 'the shipbuilding press, especially overseas, has recently referred to a number of reports that our diesel motors have proved unsatisfactory. These reports, which apparently originate from certain interested circles, quote excessive engine vibration and noise and argue for a return to steam turbines for new warships...we are aware that certain rumors are being deliberately circulated...we cannot ask the Navy for their feelings in the matter but confirm that MAN diesels give great satisfaction now as before.'

These negative reports undoubtedly influenced the decision of the Kriegsmarine to revert to steam turbine propulsion when the question next arose following completion of the three Panzerschiffe. The medium fast-running MAN large-ship diesels were naturally not without their faults, and these were not fully ironed out until 1941. But the advantage of having them outweighed everything because they were the ideal machinery for oceanic commerce raiders.

In the Kriegsmarine circles which mattered, the boiler and turbine manufacturers had numerous lobbyists whereas MAN's only representative, Pielstik, the Senior Engineer, could not afford to waste days on end in naval chambers 'waiting to be seen'. It was 1938 before the Kriegsmarine suddenly realized the pressing need for the development of new diesels for the new Z-Plan battleships, but by then they had missed the bus. Bearing in mind the contractual precondition imposed by the Reichsmarine that MAN must supply the lightest engines possible, this being ultimately the real reason underlying the later defects, the observations of a MAN specialist involved in the work on the Deutschland are enlightening: 'I would like to make the point here that MAN engineers made every possible effort to reduce the engine unit weight per hp...In the end this [the precondition] was not clever at all, for the ship rode too high in the water, and she had to be ballasted with...cast iron ribs. The designers would have found this enormous extra weight very useful for producing a stronger and more solid engine structure. No further comment is necessary."

Among some naval circles in the modern age (read: nerds in Discord servers who talk about warships all day) the effect of steam lobbyists/steam plant manufacturers in Germany (Wagner, Blohm & Voss, Brown Boveri and Co, DeSchiMag, and more) during this period in the development of large marine diesels has become well-known and understood, but for the wider world of your average naval hobbyist or enjoyer, such information might not have - or more deceptively misleading info has taken root. The purpose of this tangent is to set the record straight on that.
Reading from the above excerpts, the MAN Works Circular from 1935 states that their diesels 'give great satisfaction now as before', this quote referring to earlier MAN diesel engines. Although everyone already knows about the diesel engines present aboard the Panzerschiffe (M9Z 42/58), if one pays a bit of extra attention they will realize that earlier ships in the Reichsmarine also carried MAN diesels. For instance, the Konigsberg-class cruisers carried a pair of 10-cylinder low-power diesels and the Leipzig/Nurnberg carried four 7-cylinder diesels. While these engines themselves had issues and proved troublesome for a time, the type of criticism befalling them is significantly less than the 9-cylinder engines aboard the Deutschlands. Why?
In the late 1920's and early 1930's, diesel and steam propulsion lived in a sort of symbiotic relationship. Diesel did not interfere with the installation of a typical steam plant, but worked to improve the range of the ships. Thusly they lived happily together to increase the overall capability of the cruisers they were installed in.
Then the Bremse appeared.
The very existence of Artillerieschulschiff Bremse (commissioned 1932) represented an actual threat to the steam monopoly being that she was roughly a sort-of 'testbed' or 'proof-of-concept' for the sort of "engine-only" system that that would be upscaled and installed aboard the Deutschlands. Bremse may have carried slightly smaller 8-cylinder "M8Z 30/44" engines compared to the large 9-cylinder "M9Z 42/58" aboard Deutschland, but the ship really was a proof of concept, and an exciting one at that, proving that ships even as small as destroyers (Bremse was 103.62m/1870t max) could be powered exclusively by diesel technology. With this in mind, it should be no surprise that Bremse is where the diesel ridicule truly started as she herself faced many problems with the relatively new technology (especially in so small a package). Regardless, diesels were showing promise and if allowed to further develop could end up producing greater and greater horsepower for their weight to the point they could compete with steam and still offer much greater ranges for the ships they would be installed on. As such the teething issues that inevitably cropped up were, naturally, exploited by lobbyists in favor of steam plant manufacturers to push Kriegsmarine favor back in the direction of their products as the primary method of propulsion which served to protect their control of future contracts. Even worse, MAN is essentially stuck steadfast between a rock and a hard place: the Reichsmarine has dictated that the Diesels must produce the most PS(HP)/kg possible (necessitating making them as light as possible and therefore much more susceptible to noise and vibration) while their rival is looking for any excuse to make them look bad. While you can tell that MAN were fully aware of this given the sarcastic remarks about Deutschland, they had little choice in the matter if they wanted to remain relevant to the Kriegsmarine.

On top of everything MAN has to deal with is the undeniable fact that the steam lobby is sort of...accurate with their criticisms.

Let's break that down.

Let's get this out of the way first: the problems faced by the shipboard diesels MAN created were practically unavoidable. Beyond the fact that MAN is being shafted from both ends, large marine diesel engines of the size and power as those in the Deutschlands are an entirely new territory and as such must be placed in ships to conduct tests before they can create effective solutions. One might think that Bremse, being the 'testbed', might be the ship to do this, but there are some problems:

• The engines are of two different types and power outputs.
• Panzerschiff A (Deutschland)'s diesels were ordered earlier.
• One is a 1,800t destroyer-sized and constructed vessel, the other is a 14,000t heavy cruiser.
• There is literally less than a year between the commissioning of Bremse and Deutschland, so any general diesel-specific issues could hardly be ironed out fully in such a short space of time. (Issues related to Bremse's diesels were not fixed until 1939).
• The issues regarding the diesels are related to their design and the design of their mountings, meaning that the issues aren't superficial and solved quickly (recall that they were not "ironed out" until 1941.)
• In short: MAN is again screwed.

Additionally, I am not so biased or proud as to deny the truth. It is true that the engines were built too light. It is true that the engines vibrated horribly. It is true that the noise is literally unbearable. It is true that constant maintenance must be conducted. It is true that a stock of spare parts must be kept for said maintenance. It is true that diesels, at this period in time, use significantly more space and weight than steam for the same power output.
Deutschland sailors working in the engine rooms stated that without hearing protection the noise was so incredibly loud that their ears bled, and vibrations shook their bodies. Admiral Graf Spee, after having exceeded her scheduled engine maintenance by literally twice the work hours following the 1939 Battle of River Plate, was found to only be capable of a maximum safe speed of 17 knots because some of her engines were showing severe cases of overuse (Misshapen pistons, cylinder cracks, cracks in the foundations, the like). In service, Admiral Scheer typically rotated out her engines by keeping some on for cruising while conducting maintenance on the others. While trails showed that almost all could make 28 knots, maximum service speed was typically just 25 knots, and this means that they have no hope of outrunning the new French Deutschland-killers: the Dunkerque and Strasbourg (as I like the call them: the damn-near greatest overreaction in naval design history, brought to the world by Fr*nch copium and a rampant inferiority complex) or, worse, faster and faster battleship designs emerging in the mid-to-late 1930's (28 and 30-knotters).
It was these types of issues that led the Kriegsmarine to eventually select steam propulsion for Panzerschiffe D and E* (which would later be upscaled to became Scharnhorst and Gneisenau), in particular the lacking speed, of which steam promised miracles in its operation with very high efficiency and ranges capable of matching that of diesels, low maintenance requirements, less space and weight, and high power outputs.
(*Panzerschiff A = Deutschland, B = Scheer, C = Graf Spee, D = later Scharnhorst, E = later Gneisenau).

Yeah, I'm sure we all know how that turned out. It wouldn't be until 1938 that the Kriegsmarine, now forced to re-focus on long-range raiding operations as they could not ever directly face the Royal Navy, began to see reason once more...but as Koop said: "they missed the bus". 4 years of development is a long time to miss out on.

As discussed earlier, most of the issues cropping up from the diesels installed aboard Bremse and the Deutschlands was actually capable of being fixed with some alterations. The truth is that most of these issues (highlighted by the steam lobbyists) featured a strong case of malicious misdirection. While it is true that the problems faced were very much real, they did not decide to disclaim that these were teething issues or that some were endemic to the type of diesels MAN was forced to produce by requirement. Nobody reading this with a diesel truck or car - typically - suffers from having their eyeballs shake from the vibration, or their ears bleed from the noise? Or have to conduct constant maintenance to ensure that the engine works at all and won't have the pistons become misshapen and the cylinders crack? Do you hear these sorts of issues from most modern marine diesel engines? Or from modern MAN diesels? (Yes, MAN does still make marine diesel engines to this day, and they're quite good even if they have no 24-cylinder options to compare to sadly).
Alas there was little MAN could do but publish in their papers. MAN's chief engineer could not wait all day to be seen by the various naval groups to explain what needed to be done as he had work to do himself which essentially left the MAN diesels comparatively less defended and thus far more susceptible to the sort of misdirection posed by steam lobbyists. But that misdirection is not the truth. Even later on in their lifespan the M9Z 42/58 engines aboard the Deutschlands gave good service. Well enough that the Soviets used the engine type post-war, having gotten examples from Lutzow (ex-Deutschland) when they raised her. In Soviet service the engine was named "9CHN42/58" and featured a supercharger, continuing in service until the 1980s aboard some auxiliary vessels. There is even a Soviet diesel destroyer project that potentially uses the engine, having parameters matching the M9Z on top of the fact that the Soviets did not develop high-speed diesels of their own until after the war meaning they would source from their neighbors. It would have used 12 of these engines for three shafts (Project D-35).

Later MAN engines (those designed from 1938 and onward) would take the lessons learned from the Panzerschiffe into account for the M9Z 65/95, M11Z 42/58, V12Z 42/58, and V12Z 32/44 - or at least as best as they could given that they still needed to be capable of producing the most horsepower for the weight to compete with and (eventually) match or supersede steam. With each new model this became more and more of a reality. For instance the V12Z 32/44 - first trialed in 1944 - initially had a 100% rated output power of 10,000 hp on 67 tons (all auxiliaries included sans oil cooler). When the engine was fitted with a "exhaust gas supercharger" (turbocharger) later in testing, and this turbocharger was improved, the engine was capable of maxing out at just over 15,000 hp (approximately 11,600-12,000 hp nominal continuous). That meant it now was possible to get 80,000 continuous maximum continuous horsepower with eight engines geared to two shafts with a minor space and weight penalty - on a DESTROYER, and this is with the stock engine which did not feature the turbocharger. The V12Z 32/44 proved its worth in 1944/45, but unfortunately testing did not continue due to lack of fuel. The Allies were keenly interested in these engines post-war with the U.S. and British each taking one of the four produced. One such engine still exists to this day in Germany. The U.S.S.R. did not get one of these engines. The V12Z 32/44 form factor is still produced by MAN to this day under slightly different nomenclature and with up to 20-cylinders in V-form.

German diesels displayed an astonishing rate of improvement given the circumstances. In 1933 the M9Z was 100t per engine with an absolute maximum of 7,100 hp (abt. 6,000 continuous). In 1944, the V12Z 32/44 was producing (without supercharger) 12,500 hp maximum and 10,000 hp continuous - a massive improvement from just 10 years ago, with a 4 year gap in development thrown in there, with a part of the development cycle occurring during a war they were losing in the second half. Even despite the miracle child 32/44, the V12Z 42/58 held its own in 1940, weighing 136.5t and producing 15,600 hp maximum and easily capable of 10,000 hp continuous (conducting a 200-hr test run at this horsepower).
Among all the engines produced during and after 1938, the only one that may have had a serious problem(s) would be the lightweight V12Z 32/44. Designed primarily for destroyers, it was noted there may be potential vibration issues onboard Z51, the diesel destroyer testbed ship under construction since 1943, if they were to be fitted. Desperate to install the machinery and complete the ship to conduct trials, it was planned to place all four produced engines inside the ship, geared to the center shaft, and omit the wing shafts so that the effects of vibration could be tested as soon as possible. Perhaps fortunately for the safety of the engines this was not carried out due to testing still being conducted. Despite this, resilient mounts to remedy such problems were created after the war ended which drastically reduced vibration and dampened the noise at the cost of some additional weight. Postwar diesels created by Germany were also heavier.

With the explanations of German marine diesel development history done, let's continue with the rebuilds:

Further studies envisaged widening the beam, which would have resulted in a weight increase of 200 tons and a reduction in speed; a more acceptable variation was a broader beam, with greater length, which would have endowed the ships with greater speed but have prejudiced sea-keeping qualities, for a weight increase of 750 tons. Although this conversion, including improved splinter protection and engine room alterations, needed time. Admiral Raeder spoke out in favor in 1938 when the first decisions in this direction were finally announced, twelvemonth refits being scheduled for Admiral Scheer (from January 1940), Admiral Graf Spee (from June 1942) and Deutschland (from December 1942).

Having gotten a taste for a rebuild, it should come as no surprise by now that the project would escalate rapidly. It is almost by nature that the Konstruktionamt would do so, and yet again it brings forth interesting concepts for the rebuild. Surprisingly enough this passage states that the planned increased beam and length would have prejudiced seakeeping qualities, but I do not see how that would be the case unless the beam extension was only a portion of the total side height (increasing weight above the waterline) or if the hull was made much finer in an attempt to reduce drag and increase speed. What of Karlsruhe, though? She, too, features a beam extension in (possibly) much the same way, but there does not appear to be any notes of a deteriorated seakeeping ability. If anything it should be the opposite. Unfortunately it remains a mystery for now.

A memorandum titled 'Sea War Policy against Britain', a treatise concerning German naval building plans from Autumn 1938, remarked in respect of the Deutschland class: The first Panzerschiffe are such a valuable type of ship that an improvement in speed (28-30kt) would bring rewards. Even if with the speed increase they fail to match results obtained in cruiser warfare by the new Panzerschiff (Scharnhorst and Gneisenau), there are certain valuable complementary tasks which they can undertake. In oceanic cruiser warfare, with a top speed of at present of 25kt, their life expectancy is short.' The outbreak of war in 1939 and the periods of international tension preceding it put an end to these plans. Deutschland and Admiral Scheer were indeed ultimately rebuilt, but not to the manner envisaged prewar.

This passage is rather ironic given that two of the three Panzershiffe this refers to survived well into the war, but it does underline one of the biggest issues with the Deutschland class: speed.
Diesel engines of sufficient power to weight ratio did not exist in the early 1930's to propel these cruisers at sufficient speed to be considered acceptable by 1939 standards. Initially their speeds were adequate given the initial mission profile and potential competition they would face. All that was required was that they outgun anything faster (treaty cruisers) and manage to outrun or out-cruise anything larger (battleships). For a short time this was possible as the only nations with ships capable of catching the Panzerschiffe at the time not being foreseen as enemies (the British [Renown/Hood] and the Japanese [Kongo]). In fact, it was only the Polish and Russians that the Germans first considered, France a little later, and finally the British in 1938. Even the US did not have capital ships capable of catching the Pazerschiffe until the North Carolina class and the speeds provided for them only reached parity with the Deutschlands (though, to be fair, the turbines aboard NC would likely outlast the diesels in a sustained chase).
Things would change with the arrival of faster and faster capital ships. It was not long before 28 knots became something of a standard and even this was raised higher in some designs (30-knotters). To put it all simply: a speed increase would be necessary to delay obsolescence and increase the effectiveness and lifespan of the Panzerschiffe with respect to their intended roles.
In reality, the 1940 rebuilds for Deutschland (now Lutzow) and Admiral Scheer only went a small way to increasing the effectiveness of the ships compared to the big dreams planned out in 1937-1939. Though it certainly helped with finally stomping out the big issues around vibration and noise, it did not go so far as to fix the other major issue regarding speed (which would have required a lengthening of the hull or a re-engine). Unfortunately that is just the nature of the beast, and the war had done an excellent job of throwing almost every single naval building plan into disarray.

I can't think of a really good way to segue into this next part so we're just gonna go ahead with it.

Recently something spectacular has been found in relation to that very desire (an increase in speed). In the recent past a good acquaintance of mine went to the US National Archives to picture German machinery plans, NavTechEU documents, and other similar items and he has returned some exciting information, much more than I had expected. One of those is in relation to the Panzerschiffe rebuilds.
Finding these plans reveals that the full scope of the rebuilds is a lot less known that we currently realize. I would say that this falls to the fact a lot was lost or destroyed, but also because there is a lot of information that simply has not been digitized yet. Aside from the BA/MA, the US National Archives is a critical offender for their lack of digitization as those documents and plans represent a vast wealth of untapped Kriegsmarine knowledge; contained within the dozens of boxes are large stacks of papers and plans - a massive missing piece of information for the history of the Kriegsmarine.
Today I am proud to share one of those smaller pieces with the internet, and perhaps the world, for the first time.
1938 was the primary year that a lot of the rebuild planning was conducted, that much is clear, so it should be no surprise that beginning in August of that year three sketches were created to study the possibility of replacing the dated and fault-prone plant of M9Z 42/58 diesels with models that were under study for possible construction.
The year 1938 represents a big shift for the Kriegsmarine as they make a return to diesel systems and re-shift the focus of their navy to that of being fully engaged in a trade war against the Russians, Polish, French, and most particularly the British. Against such long odds simply being good enough or equal to can no longer cut it, and thus gave the motivation for these engine replacement concepts, as no matter how refurbished the M9Z engines were, they could not provide the necessary speed required.

On 19 August 1938, "Entwurf I" of the "Umbau-Panzerschiffe" project was created:


This first sketch is certainly incomplete and is fraught with issues, but is understandable given the tightness of the space provided. For both images depicted the length of the propulsion spaces is split in the middle to demonstrate two possible arrangements, the first (or "aft") being on the left, and the second (or "forward") being on the right. "Panzersch Deutschland" at the top appears to be the first draft, the earliest attempt which is abandoned quite early for Scheer and Spee which have slightly wider machinery spaces.
"Panzersch Adm Scheer u Adm Graf Spee" show a further two ideas and represents a more completed version of the Deutschland plan above it. The first/left/"aft" arrangement shows V10Z 42/58 main engines with attached auxiliary engines - the same arrangement as with the prior M9Z 42/58's aboard Scheer and Spee which featured one auxiliary engine per two main engines. The second/right/"fore" group shows V8Z 42/58 main engines with a single auxiliary engine for auxiliary machinery. The difference here is that there is an 8-cylinder (V4Z) 42/58 engine possibly being used to provide scavenging air and an M7Z 42/58 representing the auxiliaries. Scavenging engines were implemented to provide fresh air to the main engines so they could operate at maximum power without having their power reduced by needing to provide for their own fresh air. (Think of it like the belt on your car engine sucking some power to provide for electronics). A split gearbox featuring only two motors per gearbox (as in the M9Z 42/58 system) is used and sees the oil mills re-arranged.
Both the "aft" arrangement is impossible because the gearbox room needs to be made longer to accommodate the gearbox (it states approximately 11m is required), but cannot be done because there is no more space lengthwise. Additionally, the main engines do not fit (it is noted as 'zu eng!' - "too tight!"). For the "fore" arrangement it appears that the issue regarding the gearbox has been solved, but it has the air blower hanging very slightly outside of the citadel as it cannot be moved anywhere else as there is no room.

On 6 September 1938, another attempt was made. This is "Entwurf II":

The second attempt shows much-reduced ambition as compared to the first: "Greatest power that can be accommodated with V-engines in the old space available for engine room". At the top we can see eight V7Z 42/58 engines each of approximately 9,100 PSe, four per Vulcan gear box, for a total of 67,000 PSe - or about a 10,000 PSe increase over the maximum output of the M9Z 42/58 engine system. It also appears to show two separate arrangements fore and aft with a third below.
The "aft" arrangement shows Spee's auxiliary engines of 420 kW, one per pair of main engines with the possibility of a single 900 kW 9-cylinder engine in their stead. The "fore" arrangement shows a much more conventional method of two Deutschland-style auxiliaries of 270 kW, one per engine.
The final arrangement provided below shows a slightly more powerful system of 72,500 PSe. This is done by removing space from the gearbox room and allocating it to the second motor room so that V8Z 42/58 engines can be provided for. These engines are given a synchronous coupler so that the V7Z and V8Z engines can operate on the same gearbox. Auxiliaries would be as the above depiction (Spee auxiliaries or 900 kW 9-cyl).
Overall this would be the power required to push these ships to the proper speeds of 30 knots that was desired, but it isn't over yet.

The final design was made on 9 September 1938. This is "Entwurf III":

This is where all limitations are dropped and whatever space is needed is provided. The length of the machinery spaces depicted for the V11Z 42/58 engines is 76 meters, a 15.5 meter increase over the original 60.5 meter length. The width has been increased to 12.4 meters at the base (from 11 meters) and 16 meters at the top (from 14.8 meters) and the usable space height has increased to 6.8 meters (from 6.3 meters). In all, the space of the citadel has increased 15.5 meters x 1.4 / 1.2 meters x 0.5 meters - a not-so-insignificant increase in citadel volume. I wonder if this reflects the hull length and beam increases planned for the Deutschlands? Another mystery.
Either way the results are as one might expect. With each engine producing about 14,300 PSe and gearing losses taken into account, the new system was to produce about 106,000 PSe - double the output of the old system. Length and beam extensions were almost certainly in-mind for this, as it would be the only way to fit such a system, but even with the added weight speeds of 32-33 knots would have been possible. No doubt this was the goal so as to match the Admiral Hipper-class cruisers and better keep up with the Scharnhorst and up-and-coming Bismarck class battleships.


It is obvious from looking at the designs presented that the plans for re-engines were not taken too seriously, acting more as initial studies for the very possibility. But why?
Because, unfortunately, there was not a lot of choice.
The funds required to rapidly develop diesel engines (of which had been provided for MAN from 1928-1934) had only just been once again greenlit earlier in 1938. While some advancements such as the V-form engine had been made in the 1934-38 period, their R&D cycles were far from complete. The engines that had been developed during that period (such as the M11Z, M12Z 42/58) were simple extensions of the M9Z 42/58 and as a result were longer. The citadel length had been intended for engines 9 cylinders long and there was certainly no room left to replace them 1:1, leaving V-engines as the only reasonable option.
It would not be until 1940 that the V12Z 42/58 engine conducted its trail runs. This means that in 1938 it would be acknowledged that V-form engines would not be a reality until years later, but at the same time the political situation was rapidly devolving in late 1938 and into 1939, thus putting the threat of war much closer. In addition to this, the required

---

I suppose the big thing I wanted to do here was a prospective poke at what one of the Deutschlands (I was thinking Admiral Scheer) might look like "unleashed", being given the full treatment of the various prospective rebuild ideas (including the special plans I made reference to in one of my earlier posts which detail a 1938 re-engine series of proposals), but at this moment I just don't have the time. I'll have to edit it just like I had to edit the Gneisenau Rebuild one - and that doesn't just apply for this section, there's stuff I know I'm missing from the diesel history section above (including some fact checking) and it almost certainly reads like crap so it will need to be restructured as well.
I won't leave you empty-handed and blueballed of course, so here's what I have in mind:

Umbau-Panzerschiff "Adm. Scheer" (Rebuild 1940 to 1942, stats will reflect ship in 1945)

• Increased length and beam (750t)
• Modified battle-mast to tubular-type.
• Re-engine to two quad sets of V12Z 42/58 engines with improved motor foundations.
• Raising bulges to weather deck level.
• Various improved models of sensors
• Giving shields to AA
• Unifying secondary battery to 12.8cm SK C/34 in Drhl. C/38 twin turrets.
• Other small items of interest noted in the rebuild plans.

Thank you for your time and I hope that you will come by and check the edited version at a later date. It'll be better, I promise. Maybe.

/// REVISION UNDERWAY, PLEASE STAND BY. ///​

 

[Colonial-Marine]

The turrets traverse and elevate too slow to be useful at close ranges - and that applies (or is likely to apply) for all of them, sans potentially the LM44. The only ships that would not be capable of being engaged are dive bombers/level bombers at closer ranges, but those are typically engaged by 2cm and 3.7cm Flak at that point, which are far more effective weapons for close-in engagement and exactly why they exist. 62 degrees is adequate to engage aircraft in the outer and medium-distance zones. 62 is actually higher than most think.

Just because the elevation is not 75 degrees+ does not mean that the elevation is insufficient in the role it was intended for, especially given the date of design, size of the turret, and the weapons intended to be housed in them

Maximum surface range does not matter as much as maximum vertical performance or, much more importantly, effective range, with the latter being determined by and large by muzzle velocity. Even in naval battles, given the close ranges destroyers typically fight at, the higher muzzle velocity would be welcome. No destroyer is going to be firing at maximum range (with anything resembling effectiveness) as their small little 3-to-4 meter rangefinders cannot support it. Even the case the Flak 40 is used as a secondary weapon, its other role as anti-surface would see it firing at incoming destroyers at light cruisers which will attempt to close the range rapidly for torpedo runs.

It is not an error. You can determine this by studying the projectile weight. For the naval guns, it is 28 kg. For the Flak 40, it is 26.0 kg. This means that the lighter round will bleed off energy more at longer range and in trade it obtains greater muzzle velocity, which is key to accurate anti-aircraft fire because the chances are that you will not always be using maximum range because aircraft, bombers in particular, are not very accurate at those heights during this period.
Note: a similar (but not exactly so) principle is in use for Minengeschoss found on 2cm+ weapons.

And, of course, if you want to dive without breaking off your wings in the break-off or survive long enough to drop your bombs, you won't be diving from 12+km.


My final conclusion about the Flak 40 in C/38 is that is more than sufficient to be utilized in place of the "LM41" or LM44 and is more effective than the destroyer-tailored SK C/41 in Drhl. C/41.

If, and I am not saying you are, but if you are wondering why the KM uses 28kg if they are 'so much more ineffective', re-read the section regarding the developmental history of the SK C/41, in particular the section regarding projectiles.

Accurate assessment I think, although that lack of very high angle elevation for those guns would be a problem if you're stuck in the situation most German capital ships were stuck in later during the war. Bombers trying to drop a Tallboy on your stationary battleship are going to have an easier time without flak interference during the final run in to target. Of course I'm sure all of these potential refits would have necessitated a much improved wartime situation for the Kriegsmarine and Germany.

Ultimately I just wonder if without that very high angle capability does it becomes better to stick with the 105mm SK C/33 in an improved enclosed mounting like that planned for the H-series battleships?

As for the maximum range of the 128mm guns I'm just surprised that 2kg of projectile weight can make up for 50-70 mps of velocity for a gun of this caliber. Guess I was underestimating how important shell weight is. Either would be adequate for surface action against destroyers I'm sure.

 

[Tzoli]

This might be of some use:
KMS Deutschland booklet of ship plans

GER - YN 219 KMS Deutschland Booklet of General Plans (193X) : Deutsche Werke AG (DWK), Kiel, Germany : Free Download, Borrow, and Streaming : Internet Archive

GER - KMS DeutschlandPanzerschiffHeavy CruiserDeutschland Classofficial nr: pennant: yard nr: 219yard: Deutsche Werke AG (DWK), Kiel, Germanyyard...

archive.org

KMS Graf Spee:

GER - YN 124 KMS Admiral Graf Spee Booklet of General Plans (1934) : Kriegsmarinewerft, Wilhelmshaven, Germany : Free Download, Borrow, and Streaming : Internet Archive

GER - KMS Admiral Graf SpeePanzerschiffHeavy CruiserDeutschland Classofficial nr: pennant: yard nr: 124yard: Kriegsmarinewerft, Wilhelmshaven, Germanylaid...

archive.org

KMS Tirpitz:

GER - YN 128 KMS Tirpitz Booklet of General Plans (1939) : Kriegsmarinewerft, Wilhelmshaven, Germany : Free Download, Borrow, and Streaming : Internet Archive

GER - KMS TirpitzBattleshipBismarck Classofficial nr: pennant: yard nr: 128yard: Kriegsmarinewerft, Wilhelmshaven, Germanylaid down: november 2...

archive.org

KMS Bismarck:

GER - YN 509 KMS Bismarck Booklet of General Plans (193X) : Blohm & Voss Kommanditgesellschaft auf Aktien, Hamburg, Germany : Free Download, Borrow, and Streaming : Internet Archive

GER - KMS BismarckBattleshipBismarck Classofficial nr: pennant: yard nr: 509yard: Blohm & Voss Kommanditgesellschaft auf Aktien, Hamburg, Germanylaid...

archive.org

 

[_Sarcasticat_]

All are available on Invenio. I believe I have the Dlands up in the Library.

 

[lukasgrul]

Were there any modifications for Graf Zeppelin in terms of AA guns? From what I heard those 37mm SK C30 were pretty bad.

 

[lukasgrul]

I meant if they were proposed

 

[_Sarcasticat_]

Were there any modifications for Graf Zeppelin in terms of AA guns? From what I heard those 37mm SK C30 were pretty bad.

For the time this gun was developed and for a short time in service it was quite decent. While much better than French 37mm guns from the period, it isn't quite as "conventionally" good as the 2-pounder Pom Pom gun developed for the RN and much less so than the very impressive and standard-setting 37mm/54 Breda Model 1932 of the RM.

That isn't to say that the 37mm/83 SK C/30 is bad, but operates on a philosophy that has not stood the test of time. Though for the time it was introduced the gun is what could be considered a strong contender for the apex of its design philosophy: shot quality over quantity.

The 3.7cm/83 SK C/30 features a triaxially stabilized mount with very long barrels, light rounds, and extremely high muzzle velocity. The horizontal and vertical ranges are very good (better than contemporaries), and each mount is directed by a 1.25 meter rangefinder. In short, one could say that SK C/30 is designed as a smaller, 37mm version of the larger triaxially stabilized weapons (8.8cm, 10.5cm, etc) and mimics them in principle, design, and operation to a reasonable degree.

What you have are a pair of very powerful cannons attached to a triaxial mount and dedicated rangefinder - the goal being to provide the most accurate and damaging fire from long ranges, a philosophy shared with the larger anti-aircraft artillery cannons. Germany was under the impression that the most effective AA screen would be set at long ranges, and planned accordingly. While it is not wrong to have that idea to avoid just getting dropped on by torpedo and dive bombers when you would otherwise just open fire, the ability to shoot both your 3.7cm and 2cm weapons at much higher rates of fire and at much closer ranges than the SK C/30 was capable of is certainly superior both in terms of physical and psychological effectiveness while only having to sacrificing accurate long-range fire.
German AA doctrine seems to have been:
Main Battery Barrage Fire --> 10.5cm/8.8cm --> 3.7cm --> 2cm
(exact path differing depending on weapons present)

Nowadays we know that the best thing to do is just brrrt as many rounds as humanly possible at the target at much closer ranges, but that was not the case the last time they had developed naval AA weaponry. Having been prohibited from developing AA weapons with the Treaty of Versailles, Germany found it had a lot of catching up to do and appears to have decided to study what its neighbor, France, was doing and copy their homework. At this point (20's - early 30's) it does not seem clear to everyone that - in terms of 3.7cm/4cm guns - the superiority lie with rate of fire, though this would change later. Instead, Germany developed a gun that was accurate to very long ranges and as such sacrificed rate of fire and was fitted only with manual traverse and elevation, relying on 2cm automatic AA to do its due diligence at very close ranges.

As a whole, outside rate of fire, the stats for the 3.7cm/83 could be considered good. While the burst charge was average, the muzzle velocity is very high, and, as discussed in a prior post, high muzzle velocity is good for AAA work. The triaxial stabilization and 1.25-meter rangefinders helped to extend the effective range and accuracy of engagement for the weapons as well. Unfortunately the rate of fire in particular simply kneecapped this weapon in comparison with more modern types emerging and forced it into (by conventional standards) obscurity almost as soon as it was released in 1934. Honestly, to be put into service in the same year as the 37mm/54 Breda must be quite disheartening.

In service the weapon proved to be reliable enough and certainly accomplished what had been laid out for it to do. While most would wojak-point to Bismarck's battle against the Swordfish, it's becoming more and more common knowledge that it was likely the construction of the aircraft that limited the effectiveness of all guns (foresight, rightfully so, did not exactly account for this type of aircraft construction - especially when aircraft technology was moving at such a rapid pace) involved rather than the weapons simply being ineffective by nature. In fact, it was the opposite; the fire was described as highly (frighteningly) accurate, even if no planes were downed in that engagement.

It was not until war broke out that German long-range AA theory could actually be battle-tested, and things did not pan out as hoped. If that is the case, then why not just simply replace the 3.7cm/83 with Heer and Luftwaffe guns? Unfortunately for the Kriegsmarine, they had little choice. We know from prior discussion that the Luftwaffe and Heer both are much higher priority branches - the Heer being the traditional strong-arm of Germany and the Luftwaffe featuring the slimy, persuasive snake that is Hermann Goring (the KM dead last as the branch that had proved useless in the last war and mutinied in 1918) - and as such found the ability to get their hands on the more modern examples being developed for the other branches to be very difficult, especially after December 1942 when the KM had learned of their folly with the 3.7cm/83 and needed a replacement in production for their surface warships...only for said warships to end up largely deactivated.
You can see struggle faced by the Kriegsmarine by the fact that, much like the 128mm SK C/41, the Kriegsmarine had to steal and modify the design of a weapon (the Flak 36), tailor it to themselves, and then begin production/service (as the 3.7cm/69 M42) in 1943...only for it to be too late and priority go to arming the U-Boats with them.
The reason for such a struggle was because inter-service cooperation was atrocious. Not worse than the Japanese Army-Navy relations, but the branches certainly found it difficult to coordinate and hoarded whatever they could (example: over-filling ships' complements of sailors by ridiculous amounts) until 1944 when they were forced to share or else lose completely. Though by 1944 it was much too late and the only AA weapon aside from the 2cm/65 to see a strong common service between all three branches - the 3.7cm/57 Flak 43 - only made it to a few ships.

Perhaps if the autoloading system and Minengeschoss rounds been provided earlier than they were, the weapons might have been considered at least decent enough to avoid the common criticisms of today. But they were not, and the 3.7cm/83 SK C/30 goes down in history as an outdated weapon placed pointlessly on German designs during the war (the reality of which, as just discussed and as is typically the case, much more complicated).

To directly answer your question about GZ: no. Even in 1942 there were no planned AA changes because there was nothing to replace the SK C/30 with in the first place. Not yet, anyway.

In summary: the SK C/30 is a very decent weapon for what it was intended for, even in the opening years of WWII, but poor by conventional standards, completely outdated past ~1940/41, and did not quite live up to the hype when battle-tested. There was no choice in its utilization, though. Work on including the 3.7cm Flak 36 much earlier than 1942 (3.7cm SK C/36 and improved version 3.7cm Flak M42) might have seen a better-armed KM against the threat of aircraft than the misguided notions of 1930's long-range AA defense from a 3.7cm, but that's for an alternate universe to enjoy.

Remember that hindsight is 20/20, and direct 1v1 comparisons of naval guns can be about as meaningless as 1v1 battleship scenarios.

 

[lukasgrul]

Thank you for info. My great grandfather was in AA battery in postwar Czechoslovakia and he said to me that he hated the SK C/30 gun really much.

 

[_Sarcasticat_]

Thank you for info. My great grandfather was in AA battery in postwar Czechoslovakia and he said to me that he hated the SK C/30 gun really much.

I can imagine why. It's past 1945, there are jets now, and he's stuck with a 37mm single-shot AA gun from 1934. He probably didn't have the twin triaxial version, but the hand-cranked single is past useless in the postwar era.

 

[lukasgrul]

Yes , he didn´t have the twin triaxial. But later he was using czech version of MK 303.

 

[lukasgrul]

Are there any blueprints of Flugzeugtrager C or D? I read somewhere that they would be a bit different than Graf Zeppelin.

 

[_Sarcasticat_]

Yes , he didn´t have the twin triaxial. But later he was using czech version of MK 303.

I know of this weapon, but I wish I knew how similar they were or if there was any differences. If there aren't many, if any at all, it could help to better understand the MK 303 (Br).

Are there any blueprints of Flugzeugtrager C or D? I read somewhere that they would be a bit different than Graf Zeppelin.

I do not believe so. There were some minor differences which were also reflected in B. The biggest being that a part of the propulsion was diesel so as to extend the range.

 

[alexi]

Are there any blueprints of Flugzeugtrager C or D? I read somewhere that they would be a bit different than Graf Zeppelin.

Both have never developed far and only speculative to smaller than "A" and "B", due to Germany carrier developments have shifted from fleet carriers to mass produce light carriers, main propulsion would be diesels and no 15cm casemate guns.
Am still waiting carrier "B" plans to be digitalize on invenio.

 

[lukasgrul]

Yes , he didn´t have the twin triaxial. But later he was using czech version of MK 303.

I know of this weapon, but I wish I knew how similar they were or if there was any differences. If there aren't many, if any at all, it could help to better understand the MK 303 (Br).

Are there any blueprints of Flugzeugtrager C or D? I read somewhere that they would be a bit different than Graf Zeppelin.

I do not believe so. There were some minor differences which were also reflected in B. The biggest being that a part of the propulsion was diesel so as to extend the range.

Czechoslovakian version of MK 303 (Br) is called PLDvK vz. 53 Ještěrka (lizard). Here is a link to czech forum https://www.valka.cz/CZK-vz-53-30-mm-PLDvK-t1111.

 

[lukasgrul]

Do you have blueprint of 38cm SK C-34 L52 gun, and also a double turret for it?

 

[_Sarcasticat_]

Do you have blueprint of 38cm SK C-34 L52 gun, and also a double turret for it?

38cm/52 SK C/34 - Google Drive

drive.google.com

 

[lukasgrul]

Thank you

 

[Imidiot]

Short question about kriegsmarine ships. Is it right that Kriegsmarine ship bigger than Admiral Hipper class has hydrophone? Heard Hipper/Scharnhorst/Bismarck class has it, but not sure about Deutschland class.

 

[lukasgrul]

What part of RM 6 folder is about Graf Zeppelin and Flugzeugtrager B?

 

[_Sarcasticat_]

Short question about kriegsmarine ships. Is it right that Kriegsmarine ship bigger than Admiral Hipper class has hydrophone? Heard Hipper/Scharnhorst/Bismarck class has it, but not sure about Deutschland class.

I believe so, yes.

What part of RM 6 folder is about Graf Zeppelin and Flugzeugtrager B?

Can't recall off the top of my head, but skimming them should be enough to find which is which.

 

[Tzoli]

Do we have any weight and / or rate of fire data for the new turrets recovered from the archives? the 20,3cm triple for example?

 

[_Sarcasticat_]

Do we have any weight and / or rate of fire data for the new turrets recovered from the archives? the 20,3cm triple for example?

No, but given the date of design (1931) and the design it is basing off of (15cm/60 C/28) it could be pretty high. Possibly upwards of 6 RPM.

 

[lukasgrul]

Do you have blueprints of 105 mm SK C/33 L65 in 1938 turret thar were on most Plan-Z ships? Are there any turrets for 55 mm Gerat 58?

 

[_Sarcasticat_]

Do you have blueprints of 105 mm SK C/33 L65 in 1938 turret thar were on most Plan-Z ships? Are there any turrets for 55 mm Gerat 58?

Look under KM weaponry for 5.5cm.
I do not have the C/38 turret drawings though.

 

[lukasgrul]

Do you know why Tirpitz didn´t get 40 mm FLAK 28 or 37 mm FLAK M/42 as replacement for 37 mm SK C/30 guns when ships like Prinz Eugen, Admiral Hipper and Lutzow did?

 

[_Sarcasticat_]

Do you know why Tirpitz didn´t get 40 mm FLAK 28 or 37 mm FLAK M/42 as replacement for 37 mm SK C/30 guns when ships like Prinz Eugen, Admiral Hipper and Lutzow did?

That's an excellent question. I have no 100% for-sure answer, but my best guess is due to supply and supply line issues as well as her relative danger at the time she was in Norway compared to other units in the North and Baltic. U-Boats had undeniably surpassed the surface fleet by a very wide margin in priority and would always be the ones to receive the 3.7cm/69 guns first, leaving the surface units remaining after Hitler's rage in 1943 to scrape together whatever they could get their hands on despite the ambitious Barbara Programme. It is true that many ships were planned to receive the 3.7cm M42, even including Emden, but were curtailed by either the situation or by the lack of mounts to supply. For Tirpitz, she has the added issue of it being particularly difficult to ship those weapons far north enough to have her actually get them. By sea is essentially a death trap and over land does not appear any more viable. Besides, given her location, ships like Hipper, Eugen, Lutzow, Emden, and others needed the weapons far more as they were under much greater threat of aerial attack in the first place. If they're scraping by as far as procurement, then what does that leave Tirpitz?

All is not so bad, even with the 3.7cm C/30. Recently I had a lively debate in a certain Discord server regarding the C/30's capabilities in relation to the 25mm Type 96. While both are undeniably obsolete by 1944 it did bring to light a lot of the hidden benefits that the 3.7cm possessed and certainly served to, at least as far as I am concerned, again highlight just how terrible the 25mm is.

Keep in mind that just because your gun fires faster does not mean you will hit your target or that you will have a greater chance of hitting your target. For AA there are more than just the factors of Rate of Fire. It would be like saying the Uzi (wielded by a child) is better than the Mauser K98 (in the hands of a soldier) because it can dump a mag faster. Probably shouldn't mention the shot weight/min is roughly the same regardless of the ROF.

In short, the 3.7cm/83 is still "good enough" even if obsolete. It's noted as being far more accurate than any land-based contemporaries (such as the Flak 36/37 [by extension the M42]) with a much greater effective range due in part to high muzzle velocity/stabilization/mount weight/director/even the ROF. The increase in 20mm mounts is sufficient enough to provide close-in defense.

3.7cm M42 and M43 weapons would be preferable largely because they are simpler to maintain, easier to train and use, weigh less, require less man hours to construct, less materials, and are less likely to have corrosion-related faults*. This, in conjunction with a higher rate of fire/throw weight per minute, is the sort of criteria one would expect a 1943-45 German to prioritize over what the 3.7cm SK C/30 represents.
(* = while we have discussed that corrosion/seawater-related faults for German secondary weapons are largely a myth, 3.7cm weapons are likely to suffer more than their 10.5cm shielded big sisters.)

Though the ultimate weapon might have been something closer to a C/30 mount with M42's and a 1.25-meter rangefinder. Props if it was powered, shielded, and water-cooled.

Though a 3.7cm/83 with the attached autoloading system and Minengeschoss would have been nice as well.

 

[lukasgrul]

Thank you very much for answer.