WesWorld

Instead of the more prevalent "Maximum" 8,000 ton Category-B Light Cruiser, I have been working on this smaller and cheaper alternative.

Still packs armament and armour equivalent to the previous Ersatz Arcona Class, but is significantly smaller and cheaper.
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CL27 City Class, German Light Cruiser laid down 1927

Displacement:
5,532 t light; 5,792 t standard; 7,225 t normal; 8,372 t full load

Dimensions: Length overall / water x beam x draught
476.28 ft / 467.00 ft x 57.00 ft x 19.00 ft (normal load)
145.17 m / 142.34 m x 17.37 m x 5.79 m

Armament:
9 - 5.87" / 149 mm guns (3x3 guns), 121.25lbs / 55.00kg shells, 1927 Model
Breech loading guns in turrets (on barbettes)
on centreline ends, majority forward, 1 raised mount - superfiring
8 - 3.46" / 88.0 mm guns (4x2 guns), 20.79lbs / 9.43kg shells, 1927 Model
Dual purpose guns in deck mounts with hoists
on side, all aft
2 - 3.46" / 88.0 mm guns (1x2 guns), 20.79lbs / 9.43kg shells, 1927 Model
Anti-aircraft guns in a deck mount with hoist
on centreline aft, all raised guns - superfiring
8 - 1.46" / 37.0 mm guns (4x2 guns), 1.55lbs / 0.70kg shells, 1927 Model
Anti-aircraft guns in deck mounts
on side, evenly spread, all raised mounts
16 - 0.79" / 20.0 mm guns (4x4 guns), 0.24lbs / 0.11kg shells, 1927 Model
Breech loading guns in deck mounts
on side, evenly spread, all raised mounts
Weight of broadside 1,315 lbs / 597 kg
Shells per gun, main battery: 150
16 - 21.0" / 533.4 mm above water torpedoes

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 3.15" / 80 mm 334.36 ft / 101.91 m 9.06 ft / 2.76 m
Ends: Unarmoured
Main Belt covers 110 % of normal length

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 3.15" / 80 mm 1.97" / 50 mm 3.15" / 80 mm
2nd: 0.98" / 25 mm 0.49" / 13 mm 0.49" / 13 mm
3rd: 0.98" / 25 mm 0.49" / 13 mm 0.49" / 13 mm
4th: 0.98" / 25 mm 0.49" / 13 mm -
5th: 0.98" / 25 mm 0.49" / 13 mm -

- Armour deck: 1.18" / 30 mm, Conning tower: 3.15" / 80 mm

Machinery:
Oil fired boilers, steam turbines plus diesel motors,
Electric motors, 2 shafts, 66,348 shp / 49,496 Kw = 32.00 kts
Range 14,400nm at 15.00 kts
Bunker at max displacement = 2,580 tons

Complement:
391 - 509

Cost:
£2.203 million / $8.813 million

Distribution of weights at normal displacement:
Armament: 142 tons, 2.0 %
Armour: 1,058 tons, 14.6 %
- Belts: 397 tons, 5.5 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 232 tons, 3.2 %
- Armour Deck: 403 tons, 5.6 %
- Conning Tower: 25 tons, 0.4 %
Machinery: 2,094 tons, 29.0 %
Hull, fittings & equipment: 2,208 tons, 30.6 %
Fuel, ammunition & stores: 1,694 tons, 23.4 %
Miscellaneous weights: 30 tons, 0.4 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
5,863 lbs / 2,659 Kg = 58.0 x 5.9 " / 149 mm shells or 1.1 torpedoes
Stability (Unstable if below 1.00): 1.13
Metacentric height 2.7 ft / 0.8 m
Roll period: 14.5 seconds
Steadiness - As gun platform (Average = 50 %): 70 %
- Recoil effect (Restricted arc if above 1.00): 0.52
Seaboat quality (Average = 1.00): 1.00

Hull form characteristics:
Hull has a flush deck
and transom stern
Block coefficient: 0.500
Length to Beam Ratio: 8.19 : 1
'Natural speed' for length: 25.06 kts
Power going to wave formation at top speed: 65 %
Trim (Max stability = 0, Max steadiness = 100): 70
Bow angle (Positive = bow angles forward): 20.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 25.50 ft / 7.77 m
- Forecastle (14 %): 20.30 ft / 6.19 m
- Mid (50 %): 20.30 ft / 6.19 m
- Quarterdeck (14 %): 20.30 ft / 6.19 m
- Stern: 20.30 ft / 6.19 m
- Average freeboard: 20.60 ft / 6.28 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 110.1 %
- Above water (accommodation/working, high = better): 106.8 %
Waterplane Area: 18,444 Square feet or 1,713 Square metres
Displacement factor (Displacement / loading): 113 %
Structure weight / hull surface area: 73 lbs/sq ft or 357 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.68
- Longitudinal: 1.79
- Overall: 0.75
Caution: Hull subject to strain in open-sea
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is adequate
Ship has slow, easy roll, a good, steady gun platform

The German 15cm weapon was actually 149.1mm / 5.87in.

Transom stern is just part of the ongoing quest for weight reduction.

Quoted

Originally posted by Red Admiral
She looks ok, but not as good as my Condottieri I Class which are also built to 6000t, 0.75 strength. They gain an extra 2knts of speed and 100mm secondaries. Armour in both classes is about the same. Why is the range so long?

Range was not reall a consideration in the design, more that CL27 can operate at 32 knots for 60 hours continuously, which is a good thing in the Baltic and North Sea.

From my point of view, you traded off 2 knots for poor subdivision, a less stable gun platform, a far weaker AA suite, thinner belt armour, fewer guns with lighter shells and a lot less ammunition for your main armament.

About the only thing I would give your design is better deck armour, but how much use is that going to be when a 6in engagement is likely going to be inside 15,000 yards?

Maybe, but your design will choke on a single torpedo and can only take about half as many non-critical shell hits.

It's all tradeoffs. Metacentric height is pretty much the same and if I went for stability, CL27 would come out at 130 with a trim of 51.

I put a higher priority on gunnery performance and survivability while speed is your priority.

The historical German 15cm SK/C25 triple has a faster rate of fire than the mountings used on the 1st group of Condottieri and is at least equal to the later groups as well.

The point is moot from my point of view anyway. The CL27 design is a fleet cruiser designed to screen against torpedo attack and be the command ship for Torpedo Boat flotillas.