1917 cruisers for Peru

[Jefgte]

Studying fast 1917 AC

4T2x230-APQY-32kts, Peru AC laid down 1917 (Engine 1916)

Displacement:
   13 400 t light; 14 009 t standard; 14 972 t normal; 15 742 t full load

Dimensions: Length overall / water x beam x draught
   721.26 ft / 718.50 ft x 72.18 ft x 20.21 ft (normal load)
   219.84 m / 219.00 m x 22.00 m  x 6.16 m

Armament:
      4 - 9.06" / 230 mm guns (2x2 guns), 371.24lbs / 168.39kg shells, 1917 Model
     Breech loading guns in turrets (on barbettes)
     on centreline ends, evenly spread
      4 - 9.06" / 230 mm guns (2x2 guns), 371.24lbs / 168.39kg shells, 1917 Model
     Breech loading guns in turrets (on barbettes)
     on centreline, all amidships
      8 - 4.72" / 120 mm guns in single mounts, 52.72lbs / 23.92kg shells, 1917 Model
     Quick firing guns in casemate mounts
     on side, evenly spread
      4 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1917 Model
     Quick firing guns in deck mounts
     on side, evenly spread, all raised mounts
      4 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1917 Model
     Machine guns in deck mounts
     on side, evenly spread, all raised mounts
   Weight of broadside 3 446 lbs / 1 563 kg
   Shells per gun, main battery: 150
   8 - 21.0" / 533 mm above water torpedoes

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   4.72" / 120 mm   501.97 ft / 153.00 m   10.17 ft / 3.10 m
   Ends:   1.57" / 40 mm   190.29 ft / 58.00 m   8.01 ft / 2.44 m
     26.25 ft / 8.00 m Unarmoured ends
     Main Belt covers 107 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   4.72" / 120 mm   1.97" / 50 mm      3.94" / 100 mm
   2nd:   4.72" / 120 mm   1.97" / 50 mm      3.94" / 100 mm
   3rd:   0.79" / 20 mm         -               -
   4th:   0.50" / 13 mm         -               -
   5th:   0.50" / 13 mm         -               -

   - Armour deck: 1.38" / 35 mm, Conning tower: 4.72" / 120 mm

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 4 shafts, 102 000 shp / 76 092 Kw = 32.08 kts
   Range 7 000nm at 12.00 kts
   Bunker at max displacement = 1 733 tons

Complement:
   676 - 879

Cost:
   £2.478 million / $9.912 million

Distribution of weights at normal displacement:
   Armament: 431 tons, 2.9 %
   Armour: 2 460 tons, 16.4 %
      - Belts: 1 082 tons, 7.2 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 435 tons, 2.9 %
      - Armour Deck: 881 tons, 5.9 %
      - Conning Tower: 62 tons, 0.4 %
   Machinery: 3 800 tons, 25.4 %
   Hull, fittings & equipment: 6 429 tons, 42.9 %
   Fuel, ammunition & stores: 1 572 tons, 10.5 %
   Miscellaneous weights: 280 tons, 1.9 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     15 969 lbs / 7 243 Kg = 43.0 x 9.1 " / 230 mm shells or 1.8 torpedoes
   Stability (Unstable if below 1.00): 1.20
   Metacentric height 4.3 ft / 1.3 m
   Roll period: 14.7 seconds
   Steadiness   - As gun platform (Average = 50 %): 72 %
         - Recoil effect (Restricted arc if above 1.00): 0.41
   Seaboat quality  (Average = 1.00): 1.14

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.500
   Length to Beam Ratio: 9.95 : 1
   'Natural speed' for length: 26.80 kts
   Power going to wave formation at top speed: 51 %
   Trim (Max stability = 0, Max steadiness = 100): 63
   Bow angle (Positive = bow angles forward): 6.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      26.25 ft / 8.00 m
      - Forecastle (19 %):   21.33 ft / 6.50 m
      - Mid (45 %):      18.04 ft / 5.50 m
      - Quarterdeck (18 %):   18.04 ft / 5.50 m
      - Stern:      18.04 ft / 5.50 m
      - Average freeboard:   19.47 ft / 5.93 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 106.9 %
      - Above water (accommodation/working, high = better): 162.9 %
   Waterplane Area: 34 553 Square feet or 3 210 Square metres
   Displacement factor (Displacement / loading): 109 %
   Structure weight / hull surface area: 127 lbs/sq ft or 621 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 1.04
      - Longitudinal: 0.98
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is adequate
   Room for accommodation and workspaces is excellent
   Ship has slow, easy roll, a good, steady gun platform

[Borys]

FAST!
I like it better than the Dutch effort ...
Borys

[Jefgte]

Antisuyu, Peru 5400T Scout Cruiser laid down 1917 (Engine 1916)

Displacement:
   5 400 t light; 5 569 t standard; 6 186 t normal; 6 680 t full load

Dimensions: Length overall / water x beam x draught
   551.18 ft / 551.18 ft x 55.77 ft x 17.61 ft (normal load)
   168.00 m / 168.00 m x 17.00 m  x 5.37 m

Armament:
      2 - 6.00" / 152 mm guns in single mounts, 108.00lbs / 48.99kg shells, 1917 Model
     Breech loading guns in deck mounts with hoists
     on centreline, evenly spread
      4 - 4.72" / 120 mm guns in single mounts, 52.72lbs / 23.92kg shells, 1917 Model
     Breech loading guns in deck mounts
     on centreline, all amidships
      4 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1917 Model
     Quick firing guns in deck mounts
     on side, evenly spread
      2 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1917 Model
     Machine guns in deck mounts
     on side, evenly spread, all raised mounts
   Weight of broadside 481 lbs / 218 kg
   Shells per gun, main battery: 150
   8 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   1.57" / 40 mm   469.16 ft / 143.00 m   8.01 ft / 2.44 m
   Ends:   Unarmoured
     Main Belt covers 131 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.79" / 20 mm         -               -
   2nd:   0.79" / 20 mm         -               -
   3rd:   0.79" / 20 mm         -               -
   4th:   0.50" / 13 mm         -               -

   - Armour deck: 0.79" / 20 mm

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 4 shafts, 62 000 shp / 46 252 Kw = 32.06 kts
   Range 8 000nm at 12.00 kts
   Bunker at max displacement = 1 111 tons

Complement:
   348 - 453

Cost:
   £1.023 million / $4.094 million

Distribution of weights at normal displacement:
   Armament: 60 tons, 1.0 %
   Armour: 529 tons, 8.6 %
      - Belts: 235 tons, 3.8 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 19 tons, 0.3 %
      - Armour Deck: 276 tons, 4.5 %
      - Conning Tower: 0 tons, 0.0 %
   Machinery: 2 310 tons, 37.3 %
   Hull, fittings & equipment: 2 401 tons, 38.8 %
   Fuel, ammunition & stores: 786 tons, 12.7 %
   Miscellaneous weights: 100 tons, 1.6 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     5 115 lbs / 2 320 Kg = 47.4 x 6.0 " / 152 mm shells or 0.9 torpedoes
   Stability (Unstable if below 1.00): 1.41
   Metacentric height 3.8 ft / 1.2 m
   Roll period: 12.0 seconds
   Steadiness   - As gun platform (Average = 50 %): 72 %
         - Recoil effect (Restricted arc if above 1.00): 0.09
   Seaboat quality  (Average = 1.00): 1.19

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.400
   Length to Beam Ratio: 9.88 : 1
   'Natural speed' for length: 23.48 kts
   Power going to wave formation at top speed: 54 %
   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:      22.97 ft / 7.00 m
      - Forecastle (18 %):   18.37 ft / 5.60 m
      - Mid (40 %):      15.09 ft / 4.60 m
      - Quarterdeck (18 %):   15.09 ft / 4.60 m
      - Stern:      15.09 ft / 4.60 m
      - Average freeboard:   16.37 ft / 4.99 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 130.4 %
      - Above water (accommodation/working, high = better): 133.1 %
   Waterplane Area: 18 923 Square feet or 1 758 Square metres
   Displacement factor (Displacement / loading): 108 %
   Structure weight / hull surface area: 82 lbs/sq ft or 399 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.98
      - Longitudinal: 1.24
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is excellent
   Ship has slow, easy roll, a good, steady gun platform

[Korpen]

4T2x230-APQY-32kts, Peru AC laid down 1917 (Engine 1916)

Displacement:
   13 400 t light; 14 009 t standard; 14 972 t normal; 15 742 t full load

Seriously undergunned, those peashooters would be not even being able to defeat 20cm of armour at 10km.
Also the belt is far to narrow, it is likely that shells will find their way in beneath the belt when parts of it is exposed due to wave motion.

[Guinness]

Is there a general rule of thumb for approximating just how much of the hull will be exposed by wave for a ship at speed?

[The Rock Doctor]

I think the armament is reasonable, but I don't care for the layout.  With that much machinery, I'd be looking to keep the main battery concentrated at the ends.

The armor on the scout cruiser is pretty limited; have you considered eliminating deck and belt armor, and going with a smaller, more expendable hull?

[Jefgte]

Rocky wrote:

have you considered eliminating deck and belt armor, and going with a smaller, more expendable hull?

No armour for scout cruiser is interresting.

I have 12.000t of cruisers to built in the 1915-1920 plan.


Jef

[Jefgte]

Testing a 4000t SC with splinter armour

Scout Cruiser, Peru 4000T laid down 1917 (Engine 1916)

Displacement:
   3 996 t light; 4 157 t standard; 4 612 t normal; 4 976 t full load

Dimensions: Length overall / water x beam x draught
   528.22 ft / 528.22 ft x 55.61 ft x 13.27 ft (normal load)
   161.00 m / 161.00 m x 16.95 m  x 4.05 m

Armament:
      6 - 6.00" / 152 mm guns (2x3 guns), 108.00lbs / 48.99kg shells, 1917 Model
     Breech loading guns in turrets (on barbettes)
     on centreline, evenly spread
      4 - 4.72" / 120 mm guns in single mounts, 52.72lbs / 23.92kg shells, 1917 Model
     Quick firing guns in deck mounts
     on centreline, all amidships
      4 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1917 Model
     Quick firing guns in deck mounts
     on side, evenly spread, all raised mounts
      4 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1917 Model
     Machine guns in deck mounts
     on side, evenly spread, all raised mounts
   Weight of broadside 913 lbs / 414 kg
   Shells per gun, main battery: 127
   8 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   1.57" / 40 mm   387.14 ft / 118.00 m   8.01 ft / 2.44 m
   Ends:   Unarmoured
     Main Belt covers 113 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   1.97" / 50 mm   1.18" / 30 mm      1.57" / 40 mm
   2nd:   0.79" / 20 mm         -               -
   3rd:   0.79" / 20 mm         -               -
   4th:   0.50" / 13 mm         -               -

   - Conning tower: 1.97" / 50 mm

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 3 shafts, 34 547 shp / 25 772 Kw = 28.72 kts
   Range 7 000nm at 12.00 kts
   Bunker at max displacement = 819 tons

Complement:
   279 - 363

Cost:
   £0.756 million / $3.025 million

Distribution of weights at normal displacement:
   Armament: 114 tons, 2.5 %
   Armour: 285 tons, 6.2 %
      - Belts: 199 tons, 4.3 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 74 tons, 1.6 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 12 tons, 0.3 %
   Machinery: 1 287 tons, 27.9 %
   Hull, fittings & equipment: 2 195 tons, 47.6 %
   Fuel, ammunition & stores: 616 tons, 13.4 %
   Miscellaneous weights: 115 tons, 2.5 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     5 452 lbs / 2 473 Kg = 50.5 x 6.0 " / 152 mm shells or 1.1 torpedoes
   Stability (Unstable if below 1.00): 1.31
   Metacentric height 3.3 ft / 1.0 m
   Roll period: 12.8 seconds
   Steadiness   - As gun platform (Average = 50 %): 71 %
         - Recoil effect (Restricted arc if above 1.00): 0.23
   Seaboat quality  (Average = 1.00): 1.18

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.414
   Length to Beam Ratio: 9.50 : 1
   'Natural speed' for length: 22.98 kts
   Power going to wave formation at top speed: 49 %
   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:      22.31 ft / 6.80 m
      - Forecastle (18 %):   17.06 ft / 5.20 m
      - Mid (40 %):      13.78 ft / 4.20 m
      - Quarterdeck (18 %):   13.78 ft / 4.20 m
      - Stern:      13.78 ft / 4.20 m
      - Average freeboard:   15.11 ft / 4.61 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 112.3 %
      - Above water (accommodation/working, high = better): 145.1 %
   Waterplane Area: 18 238 Square feet or 1 694 Square metres
   Displacement factor (Displacement / loading): 119 %
   Structure weight / hull surface area: 84 lbs/sq ft or 412 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.99
      - Longitudinal: 1.09
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is excellent
   Ship has slow, easy roll, a good, steady gun platform

[Jefgte]

Always 4000t SC without protection & higher speed.

Scout Cruiser, Peru 4000T laid down 1917 (Engine 1916)

Displacement:
   4 000 t light; 4 145 t standard; 4 603 t normal; 4 970 t full load

Dimensions: Length overall / water x beam x draught
   551.18 ft / 551.18 ft x 52.49 ft x 13.92 ft (normal load)
   168.00 m / 168.00 m x 16.00 m  x 4.24 m

Armament:
      4 - 6.00" / 152 mm guns (2x2 guns), 108.00lbs / 48.99kg shells, 1917 Model
     Breech loading guns in deck mounts with hoists
     on centreline, evenly spread
      4 - 4.72" / 120 mm guns in single mounts, 52.72lbs / 23.92kg shells, 1917 Model
     Quick firing guns in deck mounts
     on centreline, all amidships
      4 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1917 Model
     Quick firing guns in deck mounts
     on side, evenly spread, all raised mounts
      4 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1917 Model
     Machine guns in deck mounts
     on side, evenly spread, all raised mounts
   Weight of broadside 697 lbs / 316 kg
   Shells per gun, main battery: 125
   8 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.79" / 20 mm         -               -
   2nd:   0.79" / 20 mm         -               -
   3rd:   0.79" / 20 mm         -               -
   4th:   0.50" / 13 mm         -               -

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 4 shafts, 44 000 shp / 32 824 Kw = 30.84 kts
   Range 7 000nm at 12.00 kts
   Bunker at max displacement = 825 tons

Complement:
   279 - 363

Cost:
   £0.805 million / $3.220 million

Distribution of weights at normal displacement:
   Armament: 87 tons, 1.9 %
   Armour: 23 tons, 0.5 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 23 tons, 0.5 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 0 tons, 0.0 %
   Machinery: 1 639 tons, 35.6 %
   Hull, fittings & equipment: 2 100 tons, 45.6 %
   Fuel, ammunition & stores: 603 tons, 13.1 %
   Miscellaneous weights: 150 tons, 3.3 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     3 882 lbs / 1 761 Kg = 35.9 x 6.0 " / 152 mm shells or 0.8 torpedoes
   Stability (Unstable if below 1.00): 1.35
   Metacentric height 3.2 ft / 1.0 m
   Roll period: 12.2 seconds
   Steadiness   - As gun platform (Average = 50 %): 71 %
         - Recoil effect (Restricted arc if above 1.00): 0.18
   Seaboat quality  (Average = 1.00): 1.18

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.400
   Length to Beam Ratio: 10.50 : 1
   'Natural speed' for length: 23.48 kts
   Power going to wave formation at top speed: 50 %
   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:      22.31 ft / 6.80 m
      - Forecastle (18 %):   17.06 ft / 5.20 m
      - Mid (40 %):      13.78 ft / 4.20 m
      - Quarterdeck (18 %):   13.78 ft / 4.20 m
      - Stern:      13.78 ft / 4.20 m
      - Average freeboard:   15.11 ft / 4.61 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 133.4 %
      - Above water (accommodation/working, high = better): 141.2 %
   Waterplane Area: 17 810 Square feet or 1 655 Square metres
   Displacement factor (Displacement / loading): 111 %
   Structure weight / hull surface area: 80 lbs/sq ft or 389 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.99
      - Longitudinal: 1.04
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is excellent
   Ship has slow, easy roll, a good, steady gun platform

[Korpen]

Why the odd mix of 12 and 15cm guns?
As I see it the 12cm guns are a compromise in themself,  if you got 15cm guns as well I think they offer little advantage over a 10cm gun.
So if i were you i would change them to either two more 15cm guns, or six 105mm guns.

[Jefgte]

I use 15cm for 15.000nm range battleline.
12cm QF are better to engage DDs at shorter range to protect BBs.

[Korpen]

I use 15cm for 15.000nm range battleline.
12cm QF are better to engage DDs at shorter range to protect BBs.

A 15cm gun is not really effective at 15km, FC or not, and is not just four guns a bit too little if you aim for long-range fire?

But for close range-melee with DDs, do you not feel that six 10,5cm are better then four 12cm, as you already got the 15cm guns for the more serious punch?

[Jefgte]

With 8x12cm - 31.5kts

Scout Cruiser, Peru 4000T laid down 1917 (Engine 1916)

Displacement:
   4 000 t light; 4 143 t standard; 4 601 t normal; 4 968 t full load

Dimensions: Length overall / water x beam x draught
   551.18 ft / 551.18 ft x 52.49 ft x 13.91 ft (normal load)
   168.00 m / 168.00 m x 16.00 m  x 4.24 m

Armament:
      4 - 4.72" / 120 mm guns (2x2 guns), 52.72lbs / 23.92kg shells, 1917 Model
     Quick firing guns in deck mounts
     on centreline, evenly spread
      4 - 4.72" / 120 mm guns (2x2 guns), 52.72lbs / 23.92kg shells, 1917 Model
     Quick firing guns in deck mounts
     on centreline, all amidships
      4 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1917 Model
     Quick firing guns in deck mounts
     on side, evenly spread
      4 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1917 Model
     Machine guns in deck mounts
     on side, evenly spread, all raised mounts
   Weight of broadside 476 lbs / 216 kg
   Shells per gun, main battery: 170
   8 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.79" / 20 mm         -               -
   2nd:   0.79" / 20 mm         -               -
   3rd:   0.79" / 20 mm         -               -
   4th:   0.50" / 13 mm         -               -

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 4 shafts, 48 000 shp / 35 808 Kw = 31.53 kts
   Range 7 000nm at 12.00 kts
   Bunker at max displacement = 825 tons

Complement:
   279 - 363

Cost:
   £0.801 million / $3.203 million

Distribution of weights at normal displacement:
   Armament: 60 tons, 1.3 %
   Armour: 19 tons, 0.4 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 19 tons, 0.4 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 0 tons, 0.0 %
   Machinery: 1 788 tons, 38.9 %
   Hull, fittings & equipment: 1 983 tons, 43.1 %
   Fuel, ammunition & stores: 601 tons, 13.1 %
   Miscellaneous weights: 150 tons, 3.3 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     3 689 lbs / 1 673 Kg = 70.0 x 4.7 " / 120 mm shells or 0.8 torpedoes
   Stability (Unstable if below 1.00): 1.42
   Metacentric height 3.5 ft / 1.1 m
   Roll period: 11.8 seconds
   Steadiness   - As gun platform (Average = 50 %): 71 %
         - Recoil effect (Restricted arc if above 1.00): 0.07
   Seaboat quality  (Average = 1.00): 1.18

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.400
   Length to Beam Ratio: 10.50 : 1
   'Natural speed' for length: 23.48 kts
   Power going to wave formation at top speed: 51 %
   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:      22.31 ft / 6.80 m
      - Forecastle (18 %):   17.39 ft / 5.30 m
      - Mid (40 %):      14.11 ft / 4.30 m
      - Quarterdeck (18 %):   14.11 ft / 4.30 m
      - Stern:      14.11 ft / 4.30 m
      - Average freeboard:   15.41 ft / 4.70 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 139.6 %
      - Above water (accommodation/working, high = better): 144.4 %
   Waterplane Area: 17 810 Square feet or 1 655 Square metres
   Displacement factor (Displacement / loading): 109 %
   Structure weight / hull surface area: 75 lbs/sq ft or 365 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 1.00
      - Longitudinal: 1.04
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is excellent
   Ship has slow, easy roll, a good, steady gun platform

---------------------
With 6x15,2cm - 30.5kts

Scout Cruiser, Peru 4000T laid down 1917 (Engine 1916)

Displacement:
   4 000 t light; 4 143 t standard; 4 601 t normal; 4 968 t full load

Dimensions: Length overall / water x beam x draught
   551.18 ft / 551.18 ft x 52.49 ft x 13.91 ft (normal load)
   168.00 m / 168.00 m x 16.00 m  x 4.24 m

Armament:
      4 - 6.00" / 152 mm guns (2x2 guns), 108.00lbs / 48.99kg shells, 1917 Model
     Breech loading guns in deck mounts with hoists
     on centreline, evenly spread
      2 - 6.00" / 152 mm guns (1x2 guns), 108.00lbs / 48.99kg shells, 1917 Model
     Breech loading guns in a deck mount with hoist
     on centreline amidships
      4 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1917 Model
     Quick firing guns in deck mounts
     on side, evenly spread
      4 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1917 Model
     Machine guns in deck mounts
     on side, evenly spread, all raised mounts
   Weight of broadside 702 lbs / 319 kg
   Shells per gun, main battery: 120
   8 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.79" / 20 mm         -               -
   2nd:   0.79" / 20 mm         -               -
   3rd:   0.79" / 20 mm         -               -
   4th:   0.50" / 13 mm         -               -

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 4 shafts, 42 000 shp / 31 332 Kw = 30.47 kts
   Range 7 000nm at 12.00 kts
   Bunker at max displacement = 825 tons

Complement:
   279 - 363

Cost:
   £0.787 million / $3.148 million

Distribution of weights at normal displacement:
   Armament: 88 tons, 1.9 %
   Armour: 19 tons, 0.4 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 19 tons, 0.4 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 0 tons, 0.0 %
   Machinery: 1 565 tons, 34.0 %
   Hull, fittings & equipment: 2 178 tons, 47.3 %
   Fuel, ammunition & stores: 601 tons, 13.1 %
   Miscellaneous weights: 150 tons, 3.3 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     4 138 lbs / 1 877 Kg = 38.3 x 6.0 " / 152 mm shells or 0.9 torpedoes
   Stability (Unstable if below 1.00): 1.31
   Metacentric height 3.1 ft / 0.9 m
   Roll period: 12.5 seconds
   Steadiness   - As gun platform (Average = 50 %): 71 %
         - Recoil effect (Restricted arc if above 1.00): 0.22
   Seaboat quality  (Average = 1.00): 1.19

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.400
   Length to Beam Ratio: 10.50 : 1
   'Natural speed' for length: 23.48 kts
   Power going to wave formation at top speed: 50 %
   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:      22.31 ft / 6.80 m
      - Forecastle (18 %):   17.06 ft / 5.20 m
      - Mid (40 %):      13.78 ft / 4.20 m
      - Quarterdeck (18 %):   13.78 ft / 4.20 m
      - Stern:      13.78 ft / 4.20 m
      - Average freeboard:   15.11 ft / 4.61 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 128.3 %
      - Above water (accommodation/working, high = better): 141.2 %
   Waterplane Area: 17 810 Square feet or 1 655 Square metres
   Displacement factor (Displacement / loading): 115 %
   Structure weight / hull surface area: 83 lbs/sq ft or 403 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.99
      - Longitudinal: 1.06
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is excellent
   Ship has slow, easy roll, a good, steady gun platform

[The Rock Doctor]

The last design's specifications look good, although I question the midships positioning of the third 6" mount.  It would be much better placed in a superfiring position forward or aft, and there's no technical reason you can't do it.

My gut instinct is that you could get a more capable 4,000 t design with a hull that wasn't quite as long or lean - say the hull form of your 2x3 turreted ship, but without the turrets or armor.

[Jefgte]

This one with 6x152

4000T - 30.3Kts, Peru Scout Cruiser laid down 1917 (Engine 1916)

Displacement:
   4 000 t light; 4 162 t standard; 4 619 t normal; 4 985 t full load

Dimensions: Length overall / water x beam x draught
   542.11 ft / 538.06 ft x 53.81 ft x 13.62 ft (normal load)
   165.23 m / 164.00 m x 16.40 m  x 4.15 m

Armament:
      6 - 6.00" / 152 mm guns (3x2 guns), 108.00lbs / 48.99kg shells, 1917 Model
     Breech loading guns in deck mounts with hoists
     on centreline ends, majority forward, 1 raised mount - superfiring
      4 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1917 Model
     Quick firing guns in deck mounts
     on centreline, all amidships
      4 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1917 Model
     Machine guns in deck mounts
     on side, evenly spread, all raised mounts
   Weight of broadside 702 lbs / 319 kg
   Shells per gun, main battery: 175
   6 - 21.0" / 533 mm above water torpedoes

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.79" / 20 mm         -               -
   2nd:   0.79" / 20 mm         -               -
   3rd:   0.50" / 13 mm         -               -

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 4 shafts, 42 000 shp / 31 332 Kw = 30.30 kts
   Range 7 000nm at 12.00 kts
   Bunker at max displacement = 822 tons

Complement:
   279 - 364

Cost:
   £0.787 million / $3.148 million

Distribution of weights at normal displacement:
   Armament: 88 tons, 1.9 %
   Armour: 19 tons, 0.4 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 19 tons, 0.4 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 0 tons, 0.0 %
   Machinery: 1 565 tons, 33.9 %
   Hull, fittings & equipment: 2 203 tons, 47.7 %
   Fuel, ammunition & stores: 619 tons, 13.4 %
   Miscellaneous weights: 125 tons, 2.7 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     4 349 lbs / 1 973 Kg = 40.3 x 6.0 " / 152 mm shells or 0.9 torpedoes
   Stability (Unstable if below 1.00): 1.29
   Metacentric height 3.1 ft / 1.0 m
   Roll period: 12.8 seconds
   Steadiness   - As gun platform (Average = 50 %): 72 %
         - Recoil effect (Restricted arc if above 1.00): 0.25
   Seaboat quality  (Average = 1.00): 1.19

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.410
   Length to Beam Ratio: 10.00 : 1
   'Natural speed' for length: 23.20 kts
   Power going to wave formation at top speed: 51 %
   Trim (Max stability = 0, Max steadiness = 100): 60
   Bow angle (Positive = bow angles forward): 10.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      22.97 ft / 7.00 m
      - Forecastle (19 %):   18.04 ft / 5.50 m
      - Mid (45 %):      14.76 ft / 4.50 m
      - Quarterdeck (18 %):   14.76 ft / 4.50 m
      - Stern:      14.76 ft / 4.50 m
      - Average freeboard:   16.19 ft / 4.93 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 127.7 %
      - Above water (accommodation/working, high = better): 162.0 %
   Waterplane Area: 17 929 Square feet or 1 666 Square metres
   Displacement factor (Displacement / loading): 116 %
   Structure weight / hull surface area: 83 lbs/sq ft or 404 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.98
      - Longitudinal: 1.17
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is excellent
   Ship has slow, easy roll, a good, steady gun platform