A different approach to anachronistic ship designs: the cruiser Shannon

A different approach to anachronistic ship designs is to take the real gun calibers and numbers, and try and make that work on a ship of the original dimensions. This does not work as easily or as well as the other approach, which is based on choosing a reasonable armament for the size ship. I have a drawing dating from 1988 that uses this approach to HMS Shannon, the classic belted cruiser. To get an acceptable Springsharp design, I had to alter dimensions and increase the displacement. I decided that if altering the design was necessary, the speed needed to be increased to 15 knots. This is the Springsharp report:

Shannon, Great Britain Belted Cruiser laid down 1912 (Engine 1908)

Displacement:
 5,879 t light; 6,237 t standard; 6,580 t normal; 6,855 t full load

Dimensions: Length overall / water x beam x draught
 275.00 ft / 275.00 ft x 59.00 ft x 24.00 ft (normal load)
 83.82 m / 83.82 m x 17.98 m  x 7.32 m

Armament:
      2 - 10.00" / 254 mm guns in single mounts, 500.00lbs / 226.80kg shells, 1912 Model
   Breech loading guns in turrets (on barbettes)
   on centreline, all forward
      3 - 9.00" / 229 mm guns (1x3 guns), 364.50lbs / 165.33kg shells, 1912 Model
   Breech loading guns in a turret (on a barbette)
   on centreline aft
      4 - 9.00" / 229 mm guns (2x2 guns), 364.50lbs / 165.33kg shells, 1912 Model
   Breech loading guns in turrets (on barbettes)
   on side, all amidships
      2 - 4.00" / 102 mm guns (1x2 guns), 32.00lbs / 14.51kg shells, 1912 Model
   Quick firing guns in a deck mount with hoist
   on centreline aft, all raised guns - superfiring
      4 - 4.00" / 102 mm guns (2x2 guns), 32.00lbs / 14.51kg shells, 1912 Model
   Quick firing guns in deck mounts with hoists
   on side, all amidships, all raised mounts - superfiring
 Weight of broadside 3,744 lbs / 1,698 kg
 Shells per gun, main battery: 100

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 9.00" / 229 mm 160.00 ft / 48.77 m 10.00 ft / 3.05 m
 Ends: 6.00" / 152 mm   65.00 ft / 19.81 m 10.00 ft / 3.05 m
   50.00 ft / 15.24 m Unarmoured ends
   Main Belt covers 90 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  1.00" / 25 mm 160.00 ft / 48.77 m 22.00 ft / 6.71 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 9.00" / 229 mm 6.00" / 152 mm  9.00" / 229 mm
 2nd: 6.00" / 152 mm 4.00" / 102 mm  6.00" / 152 mm
 3rd: 6.00" / 152 mm 4.00" / 102 mm  6.00" / 152 mm
 4th: 2.00" / 51 mm 1.00" / 25 mm  2.00" / 51 mm
 5th: 2.00" / 51 mm 1.00" / 25 mm  2.00" / 51 mm

   - Armour deck: 3.00" / 76 mm, Conning tower: 9.00" / 229 mm

Machinery:
 Coal fired boilers, complex reciprocating steam engines, 
 Direct drive, 2 shafts, 4,850 ihp / 3,618 Kw = 15.00 kts
 Range 3,500nm at 10.00 kts
 Bunker at max displacement = 618 tons (100% coal)

Complement:
 364 - 474

Cost:
 £0.661 million / $2.642 million

Distribution of weights at normal displacement:
 Armament: 468 tons, 7.1 %
 Armour: 2,469 tons, 37.5 %
    - Belts: 820 tons, 12.5 %
    - Torpedo bulkhead: 130 tons, 2.0 %
    - Armament: 797 tons, 12.1 %
    - Armour Deck: 653 tons, 9.9 %
    - Conning Tower: 68 tons, 1.0 %
 Machinery: 441 tons, 6.7 %
 Hull, fittings & equipment: 2,500 tons, 38.0 %
 Fuel, ammunition & stores: 701 tons, 10.7 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   8,058 lbs / 3,655 Kg = 16.1 x 10.0 " / 254 mm shells or 1.9 torpedoes
 Stability (Unstable if below 1.00): 1.04
 Metacentric height 2.4 ft / 0.7 m
 Roll period: 15.9 seconds
 Steadiness - As gun platform (Average = 50 %): 52 %
   - Recoil effect (Restricted arc if above 1.00): 0.97
 Seaboat quality  (Average = 1.00): 1.68

Hull form characteristics:
 Hull has a flush deck
 Block coefficient: 0.591
 Length to Beam Ratio: 4.66 : 1
 'Natural speed' for length: 16.58 kts
 Power going to wave formation at top speed: 50 %
 Trim (Max stability = 0, Max steadiness = 100): 31
 Bow angle (Positive = bow angles forward): -1.00 degrees
 Stern overhang: -2.00 ft / -0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  18.00 ft / 5.49 m
    - Forecastle (20 %): 16.00 ft / 4.88 m
    - Mid (50 %):  16.00 ft / 4.88 m
    - Quarterdeck (15 %): 16.00 ft / 4.88 m
    - Stern:  16.00 ft / 4.88 m
    - Average freeboard: 16.16 ft / 4.93 m
 Ship tends to be wet forward

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 114.4 %
  - Above water (accommodation/working, high = better): 98.6 %
 Waterplane Area: 11,772 Square feet or 1,094 Square metres
 Displacement factor (Displacement / loading): 93 %
 Structure weight / hull surface area: 135 lbs/sq ft or 659 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.84
  - Longitudinal: 4.85
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is adequate
 Excellent seaboat, comfortable, can fire her guns in the heaviest weather