The other ship design: GB/PG/1915 (not 1914)

The fast gunboat that was to accompany the scout cruiser is actually designated GB/PG/1915. I have often called it GB/PG/1914. The armament is 4-4in QF guns, mounted on the centerline, but not superfiring. The hull is flush-decked, with dimensions intended to be 260ft x 27ft x 9.5ft. The standard displacement was intended to be 800 tons. The Springsharp design that I did tonight is 21 tons lighter, with greater freeboard and draft. Interestingly enough, the seakeeping improved with heavier machinery. I started with 1950 for the year, and decided that on the order of 60 SHP/ton was excessive. This is the report:

GB/PG/1914, Great Britain Fast Gunboat laid down 1914 (Engine 1932)

Displacement:
 748 t light; 779 t standard; 890 t normal; 979 t full load

Dimensions: Length overall / water x beam x draught
 263.26 ft / 260.00 ft x 27.00 ft x 12.00 ft (normal load)
 80.24 m / 79.25 m x 8.23 m  x 3.66 m

Armament:
      4 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1914 Model
   Quick firing guns in deck mounts with hoists
   on centreline ends, evenly spread
 Weight of broadside 128 lbs / 58 kg
 Shells per gun, main battery: 180

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 2 shafts, 26,478 shp / 19,752 Kw = 32.00 kts
 Range 3,600nm at 15.00 kts
 Bunker at max displacement = 201 tons

Complement:
 80 - 105

Cost:
 £0.133 million / $0.530 million

Distribution of weights at normal displacement:
 Armament: 16 tons, 1.8 %
 Machinery: 461 tons, 51.8 %
 Hull, fittings & equipment: 271 tons, 30.4 %
 Fuel, ammunition & stores: 142 tons, 16.0 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   235 lbs / 106 Kg = 7.3 x 4.0 " / 102 mm shells or 0.2 torpedoes
 Stability (Unstable if below 1.00): 1.39
 Metacentric height 1.2 ft / 0.4 m
 Roll period: 10.1 seconds
 Steadiness - As gun platform (Average = 50 %): 52 %
   - Recoil effect (Restricted arc if above 1.00): 0.40
 Seaboat quality  (Average = 1.00): 1.04

Hull form characteristics:
 Hull has a flush deck
 Block coefficient: 0.370
 Length to Beam Ratio: 9.63 : 1
 'Natural speed' for length: 16.12 kts
 Power going to wave formation at top speed: 71 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 4.00 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 %): 13.00 ft / 3.96 m
    - Mid (50 %):  13.00 ft / 3.96 m
    - Quarterdeck (15 %): 13.00 ft / 3.96 m
    - Stern:  13.00 ft / 3.96 m
    - Average freeboard: 13.40 ft / 4.08 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 181.2 %
  - Above water (accommodation/working, high = better): 132.1 %
 Waterplane Area: 4,267 Square feet or 396 Square metres
 Displacement factor (Displacement / loading): 53 %
 Structure weight / hull surface area: 27 lbs/sq ft or 131 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.43
  - Longitudinal: 3.67
  - Overall: 0.53
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent