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SireneRacker

Turning the Königsberg-class into AA-Cruisers, how could it look?

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Heyo, a month or two ago @MutsuKaiNi asked me if there were any designs for a German Atlanta. To my knowledge, no. But I promised to create one from scratch (so basically what WG did with a good number of Russian BBs, according to their Developer Diary), and it would be a waste if I just left it to rot on my hard drive.

 

The entire background of this is a huge what-if. What if Germany had the time and resources to pull through their Z-plan? What if the war had not begun in 1939? What if Germany realized the need for dedicated anti-aircraft vessels? Now while one can argue the likelihood of all these events ever happening, they do in combination result in this thread. And here it is, what would be if Germany decided to convert one of their K-class cruisers into an AA cruiser? How would this take shape? What would be the most likely changes?

If it is not obvious yet, I shall make it clear now: All the changes while based on actual events or ideas or concepts, have been merged in what is a product of my creativity. There was to my knowledge no plan to make something even remotely similar to this.

To avoid confusion, I will imagine a fourth K-class ship and apply everything to her. I will give her the name Kassel. The K-class ships were named after German cities starting with K, and Kassel meets that criteria.

 

Step 1: We un-suck the K-class

The first few changes are rather obvious. We shall apply the refit that Karlsruhe received, that was also planned for all the other light cruisers not called Emden. Since we have moved the beginning of the war at some other point, this is a plausible step. What it does is adding bulges to the side of the ship, rearranging the searchlights, strengthening the hull and thus making her more seaworthy. Additionally Kassel would receive a 14mm upper belt and a 16mm upper deck, which would give splinter protection (and probably be useful against strafing aircraft, heh). Probably the most important change however is that Karlsruhe after her refit was capable of carrying the 105mm dp gun, which she did for the final months of her career. Since this gun will be the main armament later, enabling the ability to carry them is essential. A downside is that the speed drops to 30-31kn, and the cruising range is also going down. All of the things in this paragraph have been applied to a K-class vessel in reality, and are thus not fictional.

For visualization, this is a plan of Karlsruhe after her refit.

Karlsruhe.thumb.gif.cc2cf0609837360965d444b049e2c7bb.gif

Step 2: We un-suck the K-class, round 2

We know that Köln (the only surviving member of the class after the occupation of Norway) would trade in her rear pair of torpedo launchers and her catapult. This will also be applied to Kassel, which will open up space for smaller arms and remove a fire hazard from the midship section.

Since my drawing skills suck, I simplified the drawing by removing things such as lifeboats, cranes, etc. We do however keep in mind that they take up space.

 491275610_Kassel2.thumb.jpg.a0ff6ff75d9cda1da665e853bbecafa5.jpg

Step 3: We initiate the refit

And now we are somewhere around 1942, the first units of the M-class are entering service, we still got those old K-class grannies around but thanks to their refit they can no longer keep up with the more modern vessels. What to do…? Smart idea, we turn them into an AA cruiser! The US has those fancy Atlanta class ships, and what they can do, Germany can do as well (not really, but anyway). And now we are entering the section where I start making things up, but will back the changes directly or indirectly.

Our weapon of choice? The 105mm gun. Solid. This was the standard heavy AA weapon of the Kriegsmarine, being mounted on all heavy Cruisers at this stage, all Battleships and was also planned for future capital ships.

The first step in our refit is now that the main turrets will have to go. As sad as it may be, there is no use for them on a ship which shall dedicate itself to AA duties. So begone! This would also include the rangefinders for the main armament, of which the one on the conning tower and the one on the rear superstructure would be removed to open up space for other equipment. Additionally there are also the two 3m rangefinders on the side of the foremast, which will be removed. These were initially serving the purpose of directing the torpedo armament and night fighting. However, as Kassel will be serving as an AA vessel her torpedo armament will be a weapon system which won’t be used regularly, so the room that we’d get would be well used on other equipment.

Now there’s plenty of room to use. But an artillery gun can’t just be placed anywhere, a link to the magazines is needed to feed it with ammunition. That is thankfully covered, we still got Kassel’s main battery hoists. So three hoists per barbette, each delivering around 65kg of cargo every 7.5s (to reflect the RoF of the previous main guns). A complete round weights around 27kg, so we can be sure to transport two rounds with every hoist every 7.5s, so total supply per barbette is 48 shells every minute assuming that no hoist modifications take place. With that in mind we can say that each barbette can feed up to two twin mounts for a sustained output of 12 shells per gun and minute. Ready ammunition like it was usual would allow for the output to be initially higher.

As for the placement, I went with this:

 1069010911_Kassel4.thumb.jpg.8757fe51351bd5711e1805e567d1d9d9.jpg

Step 4: Fine-tuning

Now that is all nice and well, but there are a few more things to do. Next up is fire control equipment. We made room for a few fire directors. Using the AA fire director we got already, we can take two more and add them. One around the conning tower, a second one around the rear superstructure. The reason for having two at the rear is that there are six mounts, so to allow for split fire directing like the Germans loved to do two would be provided. An important thing to note here is that the AA fire directors will also be directing the torpedo armament. German warships allowed for the fire directors to feed different systems if needed, so if the torpedo armament is needed, an AA fire director will feed the data to the torpedo computing room and thus a torpedo firing solution will be generated. Also note that these rangefinders work just as well against surface units, however I decided to let one 5m rangefinder remain on the ship for ASu warfare.

Kassel is shaping up already, though we are not done yet. There is obviously a lack of medium and small caliber AA armament. For that we have to look at what was given to Köln, Emden and Nürnberg starting 1944. Aside from the usual array of 20mm guns, there is also the 37mm M42 and the 40mm Bofors being adopted. The Bofors however was acquired through the occupation of several European nations, so given the scenario we are in right now the Bofors falls out. The 37mm M42 however remains as an option, and from what I can gather six twin mounts can be equipped, assuming that the German standards of gun mount placement do not change. As for the 20mm gun, following the German arrangement patterns we saw on other K-class vessels and some cruisers, there would be room for in total ten twin mounted 20mm FlaK38s.

As a note for the picture, I only later on realized that the structure itself on which the catapult rested before remained on Köln, so I added it afterwards. I also made some smaller corrections and additions which include the crest, of the city of Kassel, a smaller platform around the two superfiring 105mm guns for the gun crew and corrected some smaller errors here and there as well as adding at least some sort of watermark.

1837272189_Kassel5.thumb.jpg.365b21a3960c074b20aed089bb09da20.jpg

Dimensions:
- 174m long, 16.8m wide, up to 6m draft

Displacement:
- 6,300 tons standard load
- 8,000 tons full load

Machinery:
- 68,200shp or 1,800shp, depending on type of propulsion
- 31kn speed under steam, 10kn speed under Diesel
- 3,500nm under steam, 6,500nm under Diesel

Armament:
- Sixteen (8x2) 105mm/65 dual purpose guns
- Twelve (6x2) 37mm M42
- Twenty (10x2) 20mm FlaK38
- Six (2x3) 533mm Torpedo launchers

 

Conclusion:

How likely would these steps be in reality? I'd say quite low. With the war breaking out in 1939 no extensive refits could be afforded by the Kriegsmarine, hence why only Karlsruhe was the only one to receive the refit. As there weren't that many 

The refit however does have a few changes whose impacts can't be estimated by me. If someone knows what would happen, feel free to let me know. For example there is a very noticable loss of weight above the waterline. The three 15cm turrets had a weight of around 410 tons. Their replacement with five 105mm twins means that a total weight loss of roughly 270 tons took place. Adding this to the removal of the catapult and two torpedo banks means that the lost tonnage is around 400 tons, if not more. This might result in an increase in speed and improved stability, as well as a longer cruising range. Also I am not sure how the hoists would be affected by this. Could their delivery rate be increased given the lighter individual load?

In its role as an AA ship Kassel would outperform anything that was German. Plenty of long range triple A as well as a modern medium and short range suite would ensure close range defenses, although the medium and short range is by no means special. Fire control wise by refraining from using the tri-axial stabilized 3m rangefinders that Prinz Eugen for example carried there is a good deal of potential lost, maybe it would get replaced with more modern equipment, maybe not, I don't know. Against anything larger than a Destroyer Kassel would stand no chance. The armor being very thin for a ship in the 40s, and only standing up against Destroyer caliber fire and against strafing aircraft, and sort of surface engagement would be risky at best, suicidal at worst.

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Nice work, and intriguing proposal.

However if WG were to go down this route for a 'German Atlanta' then I hope they use Nurnberg as a base instead of Konigsberg. The asymmetrical turret layout at the back bugs me.

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8 hours ago, Super_Dreadnought said:

Nice work, and intriguing proposal.

However if WG were to go down this route for a 'German Atlanta' then I hope they use Nurnberg as a base instead of Konigsberg. The asymmetrical turret layout at the back bugs me.

Nürnberg being a larger ship could easily fit even more of those sweet 105mm guns there :Smile_teethhappy:

However, I haven‘t found anything suggesting that she could carry the 105mm gun in the first place. Karlsruhe post-refit could, Nürnberg would not receive those guns at any point in her career. This wouldn‘t stop WG of course, though my post is more into the historical direction rather than gameplay.

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On 6/9/2019 at 11:17 AM, SireneRacker said:

Heyo, a month or two ago @MutsuKaiNi asked me if there were any designs for a German Atlanta. To my knowledge, no. But I promised to create one from scratch (so basically what WG did with a good number of Russian BBs, according to their Developer Diary), and it would be a waste if I just left it to rot on my hard drive.

 

The entire background of this is a huge what-if. What if Germany had the time and resources to pull through their Z-plan?

So, nice design and all, good work, but Germany did in fact have multiple Atlanta equivalents, all of which were built:

atlanta1.thumb.gif.98bd9eb0ef83dd0a25a2aece43b1144c.gifatlanta3.thumb.png.703c0d21ed51ab3c1dff7ba03f0607ea.png Another Atlanta equivalent, KMS Ariadne, was not noticeably different from KMS Undine.

atlanta2.thumb.png.4294ff7ce981a49bbc42a0422e4e74ca.pngSorry. :Smile_hiding:

Edited by black_hull4

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5 hours ago, black_hull4 said:

So, nice design and all, good work, but Germany did in fact have multiple Atlanta equivalents, all of which were built:

Unfortunately, none of those are even close to being Atlanta equivalents. To know what an Atlanta equivalent would be you have to look at more than just if it's a boat with lots of dp guns (otherwise you might as well call the Fletcher class Atlanta-equivalents). You need to look at what the ship can be used for. In Atlanta's case (and the case of this thread) it's about a cruiser (read: a ship capable of independent operations with a wide variety of applications) with enhanced (read: well above average compared to other ships of their navy) AA capabilities for fleet defense (that's what they were used for in the end. Their initial purpose was being a DD leader but that was not what they became known for).

Now keeping that in mind one can go through what you propose as "Atlanta equivalents":

5 hours ago, black_hull4 said:



atlanta1.thumb.gif.98bd9eb0ef83dd0a25a2aece43b1144c.gif

This is completely out of era. The need for dedicated AA vessels died long before the Deutschland class entered service. Deutschland is not even an AA ship to begin with. She could engage aircraft, but she was a training ship by design and throughout her entire service career.

5 hours ago, black_hull4 said:

atlanta3.thumb.png.703c0d21ed51ab3c1dff7ba03f0607ea.png 

Undine and Ariadne are about as far away as being AA cruisers as you could be. What was left of their machinery post refit was solely for power generation, and movement could only happen when using tugboats. You might as well try to sell those as AA cruisers:

image.thumb.png.e4fd5f7e84db3cbc2fdc1e1892710bf3.png

They were floating AA batteries. Not AA cruisers. And most definitely not equivalents to the Atlanta-class. They lack the ability to act independently.

5 hours ago, black_hull4 said:

atlanta2.thumb.png.4294ff7ce981a49bbc42a0422e4e74ca.png

While Niobe (as well as Nymphe and Thetis) could move under their own power, they were mainly used as stationary AA batteries. Even then, they are no equivalents of AA cruisers, most definitely not of the Atlanta class. They lack the fleet defense element that coined the Atlanta class. They are too slow and too short ranged to be considered cruisers. And the Germans also didn't consider them as cruisers. They referred to them as "floating flak batteries".

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I suppose you could argue that a true "Atlanta-equivalent" would mean adapting dual-purpose destroyer main battery mounts.  Germany was obviously in the "bigger is better" camp for DD armament and 105s were out of the question, so something like an M-class hull with the WG-design-bureau dual-purpose 128mm (Z-49/Z-52 primaries, Agir/Kurfurst secondaries)would be a more direct comparison .. let's say Munchen with no torps, twin 128 L/61s in two superfiring pairs fore and aft, and then for bonus Atlanta points an additional pair of semi-sponsoned wing turrets for a 10-gun broadside.


Of course, there is also the angle that yes- German 105mms were historically a main armament for ultralight cruisers.  France slapped a few on a Paolo Emilio hull.  https://en.wikipedia.org/wiki/French_cruiser_Châteaurenault_(D_606)

I imagine WG will get around to modeling that eventually.

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