Logi's Design Studies

[Logi]

Real purpose-built CL. Turret arrangement a la Mogami.
Because the guns are in turret&barbette, they should have power loading, power ramming, power train/elev

Thoughts?

CL22,  Light Cruiser laid down 1922

Displacement:
   10,000 t light; 10,540 t standard; 11,474 t normal; 12,221 t full load

Dimensions: Length overall / water x beam x draught
   550.00 ft / 550.00 ft x 67.00 ft x 20.00 ft (normal load)
   167.64 m / 167.64 m x 20.42 m  x 6.10 m

Armament:
     20 - 6.00" / 152 mm guns (5x4 guns), 108.00lbs / 48.99kg shells, 1922 Model
     Breech loading guns in turrets (on barbettes)
     on centreline ends, majority forward, 2 raised mounts - superfiring
     4 - 3.00" / 76.2 mm guns (2x2 guns), 13.50lbs / 6.12kg shells, 1922 Model
     Anti-aircraft guns in deck mounts
     on side, all aft, all raised mounts - superfiring
   Weight of broadside 2,214 lbs / 1,004 kg
   Shells per gun, main battery: 250
   6 - 21.0" / 533.4 mm above water torpedoes

Armour:
  - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   3.50" / 89 mm   550.00 ft / 167.64 m   16.00 ft / 4.88 m
   Ends:   Unarmoured
     Main Belt covers 154 % of normal length

  - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   3.00" / 76 mm   2.00" / 51 mm      2.00" / 51 mm
   2nd:   1.00" / 25 mm         -               -

  - Armour deck: 1.50" / 38 mm, Conning tower: 3.00" / 76 mm

Machinery:
   Oil fired boilers, steam turbines,
   Direct drive, 2 shafts, 88,023 shp / 65,665 Kw = 31.00 kts
   Range 10,000nm at 12.00 kts
   Bunker at max displacement = 1,681 tons

Complement:
   553 - 720

Cost:
   £2.729 million / $10.915 million

Distribution of weights at normal displacement:
   Armament: 277 tons, 2.4 %
   Armour: 2,180 tons, 19.0 %
      - Belts: 1,140 tons, 9.9 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 298 tons, 2.6 %
      - Armour Deck: 710 tons, 6.2 %
      - Conning Tower: 33 tons, 0.3 %
   Machinery: 2,986 tons, 26.0 %
   Hull, fittings & equipment: 4,270 tons, 37.2 %
   Fuel, ammunition & stores: 1,474 tons, 12.8 %
   Miscellaneous weights: 287 tons, 2.5 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     12,331 lbs / 5,593 Kg = 114.2 x 6.0 " / 152 mm shells or 1.6 torpedoes
   Stability (Unstable if below 1.00): 1.17
   Metacentric height 3.6 ft / 1.1 m
   Roll period: 14.7 seconds
   Steadiness   - As gun platform (Average = 50 %): 60 %
         - Recoil effect (Restricted arc if above 1.00): 0.43
   Seaboat quality  (Average = 1.00): 1.01

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.545
   Length to Beam Ratio: 8.21 : 1
   'Natural speed' for length: 23.45 kts
   Power going to wave formation at top speed: 60 %
   Trim (Max stability = 0, Max steadiness = 100): 60
   Bow angle (Positive = bow angles forward): 0.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      24.00 ft / 7.32 m
      - Forecastle (20 %):   21.50 ft / 6.55 m
      - Mid (50 %):      20.00 ft / 6.10 m
      - Quarterdeck (15 %):   20.00 ft / 6.10 m
      - Stern:      20.00 ft / 6.10 m
      - Average freeboard:   20.73 ft / 6.32 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 107.1 %
      - Above water (accommodation/working, high = better): 159.2 %
   Waterplane Area: 25,595 Square feet or 2,378 Square metres
   Displacement factor (Displacement / loading): 108 %
   Structure weight / hull surface area: 110 lbs/sq ft or 536 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.95
      - Longitudinal: 1.53
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is adequate
   Room for accommodation and workspaces is excellent

[Sachmle]

Boy, she's a biggun. I'd probably go w/ singles for the 3" AA for RoF concerns and to provide more coverage. Other than that, scary.

[P3D]

Too short hull for five (even four) big turrets. I'd get rid of the fifth one - it takes up too much valuable deck space (12m or so), and don't leave enough room for the machinery. It also pushes A turret far forward that it would have problem at the narrowing hull.

Otherwise, a valid design, if a navy faces a lot of destroyers without Armored cruiser support.

[Logi]

I figured the 6" gun+turret would take up around 11m of deck space, but that's a trivial difference.

Without a whole floatplane contraption, there should be ~90 ft of superstructure eliminated. That places the Mogami's LWL closer (although I don't know the machinery size). There's also the thing to note that this ship goes a lot slower than the Mogami, which in turn means it needs a lot less machinery. (The SS jump from 31 to 32 kts was worth 0.13 composite strength, for example). The PWOE puts the Mogami class's speed at 34.9 kt (That's 0.58 composite strength here and a difference of 191.66 ft in machinery space).

Also SS states that the magazine & machine space is 383 ft, 314.03 with just machinery. My calculations put the space for guns and working space at 210 ft at most. That would be 137 ft left for superstructure and torpedo tubes (which don't interfere with boilers and turbines) if we went with no guns on forecastle or quarterdeck. The barbettes don't have to be particularly deep either.

The BC is at a healthy 0.545, and with the predicted diameter of a quad 6" turret at 30', there should be enough space?

Perhaps you know something more that I don't? If so, I would appreciate it if you would share it with me.

[Kaiser Kirk]

Considering that HMS Orion managed 5 twin 13.5" turrets on Centerline on 5 less feet of length, I'd guess the turrets fit.  Granted she's shorter than the Edinburgh but as pointed out no Aircraft facilities, and she actually has less secondary "spots"s.  Also that at 67ft beam she's wider than the Edinburgh Class which originally was to mount Quad 6", and she does have a healthy BC.. not seeing the length issue.  Machinery space would be all, and that's a SS issue that's been asked and answered.

[Sachmle]

While I agree with you Kirk, I feel the need to point out that HMS Orion had a waterline length of 576', 26' longer than this ship.

As for comparing directly to Mogami, she was 110.5' longer, but as you both pointed out, not placing the aircraft facilities probably saves ~90', so only 20.5' longer in use.

[Jefgte]

 With 5T4, increase the hull to the max -170m
Globaly, certainly a possible 1922 built -  with internal subdivision study interresting to draw.

IMO, reduce to 4T4 is enough & the cruiser better balanced.
Instal 4 high towers with rangefinders to engage 4 # DDs is also an interresting study drawing.


Jef

[Kaiser Kirk]

Well, Preston's Battleships of WWI is wrong then :)
Let me change my reference point to HMS Erin then :)

[P3D]

Look at the magazine+machinery spaces in your design. 313' is taken by the machinery itself. The turrets, why not extending all the way down, still needs the magazines and support structures below them.
The quad  barbette would take up more than 20' space. Smallest barbette ID was 17' for the US triples, for the RN triples it was 23'. I'd assume the RN quad would have fit the latter barbette ID, too. But assume 20' barbette diameter, 4' minimum between barbettes (turret overhang, clearance)
The pyramid turret arrangement of the Brooklyn-class would be more compact, saving ~15' compared to your design, but that's still an extra 110' citadel length. Too far aft/forward (115-120% "hull space by SS2) for a large turret.

I figured the 6" gun+turret would take up around 11m of deck space, but that's a trivial difference.

Without a whole floatplane contraption, there should be ~90 ft of superstructure eliminated. That places the Mogami's LWL closer (although I don't know the machinery size). There's also the thing to note that this ship goes a lot slower than the Mogami, which in turn means it needs a lot less machinery. (The SS jump from 31 to 32 kts was worth 0.13 composite strength, for example). The PWOE puts the Mogami class's speed at 34.9 kt (That's 0.58 composite strength here and a difference of 191.66 ft in machinery space).

Also SS states that the magazine & machine space is 383 ft, 314.03 with just machinery. My calculations put the space for guns and working space at 210 ft at most. That would be 137 ft left for superstructure and torpedo tubes (which don't interfere with boilers and turbines) if we went with no guns on forecastle or quarterdeck. The barbettes don't have to be particularly deep either.

The BC is at a healthy 0.545, and with the predicted diameter of a quad 6" turret at 30', there should be enough space?

Perhaps you know something more that I don't? If so, I would appreciate it if you would share it with me.

[Jefgte]

See now the lenght of the belt

Armour:
  - Belts:      Width (max)   Length (avg)      Height (avg)
  Main:   3.50" / 89 mm   550.00 ft / 167.64 m   16.00 ft / 4.88 m
  Ends:   Unarmoured
    Main Belt covers 154 % of normal length

167m for a 167m hull.

If I understand well SS, Magasines+ boilers + turbines + #machineries = the entire lenght of the ship -
:o :o :o

Impossible
-------------------
test 4T4 & 30kts


Jef

[Sachmle]

See now the lenght of the belt

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   3.50" / 89 mm   550.00 ft / 167.64 m   16.00 ft / 4.88 m
   Ends:   Unarmoured
     Main Belt covers 154 % of normal length

167m for a 167m hull.

If I understand well SS, Magasines+ boilers = turbines + #machineries - the entire lenght of the ships -
:o :o :o

Impossible
-------------------
test 4T4 is better & 30kts


Jef

The belt is the total length by choice, not necessity in this case. If you sim it, it only REQUIRES a ~383ft belt.

[Logi]

Yes, I decided to have total coverage over an AoN scheme.

[Kaiser Kirk]

The only element that strikes me is the total hull space = 107%.
We normally ignore this, but the way I tend to interpret it is that not all critical systems fit under a water-line level armor deck.
So, critical things like the feed water unit on Graf Spee can get hit, and still have the armor intact....
However..
This ship has a 2 deck level high armor belt, indicating to me the armor deck can be at it's top, thus providing room for that 7% that sticks above waterline.

[Sachmle]

The only element that strikes me is the total hull space = 107%.
We normally ignore this, but the way I tend to interpret it is that not all critical systems fit under a water-line level armor deck.
So, critical things like the feed water unit on Graf Spee can get hit, and still have the armor intact....
However..
This ship has a 2 deck level high armor belt, indicating to me the armor deck can be at it's top, thus providing room for that 7% that sticks above waterline.

If he shortened the forecastle and/or quarterdeck (20% and 15% respectively) this would help. That 100% hull volume is the amount of space inside a box created by the forecastle and quarterdeck settings on the freeboard page as ends, the waterline as the top, the keel as the bottom and the sides of the ship as sides.

More hull depth, beam, block coefficient, ship length, or shorter quarterdeck/forecastle would all effect this positively. And at 7% over, he should be able to make some tweaks and squeeze it in.

I would follow Jef's suggestion of going to the full 557' allowed for a type 2, and probably adjust the forecastle to 15% maybe. If one looks at a picture of Mogami, you can see she has a rather short forecastle (distance from A turret to stem).

[Kaiser Kirk]

My point was that because he had a tall belt, one could reasonably presume that there is additional vertical space for things to fit within.

Humorously, what I thought when I read the Mogami reference was ' shouldn't use Japanese ships for structural reference, wasn't Mogami one of those that had to go back for strengthening?'  actually, I can't recall if she was one of them, but they did push their designs.