My friend Cliff's design for a large, fast gunboat: GB/PGL/1906

I have been battling Springsharp again, because it would not use a sufficiently great SHP/ton figure. I kept having to up the date for the engines until the SHP/ton reached 52.2, which is much lower than was achieved on the Swift (about 64 SHP/ton in 1907). The GB/PGL/1906 was intended to be a 36-knot, 1600 ton destroyer-like vessel with 3-5in QF guns. Here is the Springsharp report:

GB/PGL/1906, Great Britain Large Fast Gunboat laid down 1906 (Engine 1937)

Displacement:
 1,746 t light; 1,810 t standard; 1,913 t normal; 1,996 t full load

Dimensions: Length overall / water x beam x draught
 340.80 ft / 340.00 ft x 35.00 ft x 17.00 ft (normal load)
 103.88 m / 103.63 m x 10.67 m  x 5.18 m

Armament:
      3 - 5.00" / 127 mm guns in single mounts, 62.50lbs / 28.35kg shells, 1906 Model
   Quick firing guns in deck mounts with hoists
   on centreline ends, majority forward, all raised mounts - superfiring
 Weight of broadside 188 lbs / 85 kg
 Shells per gun, main battery: 240

Machinery:
 Oil fired boilers, steam turbines, 
 Direct drive, 2 shafts, 59,409 shp / 44,319 Kw = 36.00 kts
 Range 3,500nm at 12.00 kts
 Bunker at max displacement = 186 tons

Complement:
 144 - 188

Cost:
 £0.240 million / $0.961 million

Distribution of weights at normal displacement:
 Armament: 23 tons, 1.2 %
 Machinery: 1,138 tons, 59.5 %
 Hull, fittings & equipment: 585 tons, 30.6 %
 Fuel, ammunition & stores: 167 tons, 8.7 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   375 lbs / 170 Kg = 6.0 x 5.0 " / 127 mm shells or 0.2 torpedoes
 Stability (Unstable if below 1.00): 1.41
 Metacentric height 1.9 ft / 0.6 m
 Roll period: 10.7 seconds
 Steadiness - As gun platform (Average = 50 %): 55 %
   - Recoil effect (Restricted arc if above 1.00): 0.27
 Seaboat quality  (Average = 1.00): 1.10

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.331
 Length to Beam Ratio: 9.71 : 1
 'Natural speed' for length: 18.44 kts
 Power going to wave formation at top speed: 68 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 2.00 degrees
 Stern overhang: 0.00 ft / 0.00 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  23.00 ft / 7.01 m
    - Forecastle (36 %): 21.00 ft / 6.40 m
    - Mid (36 %):  21.00 ft / 6.40 m (13.00 ft / 3.96 m aft of break)
    - Quarterdeck (15 %): 13.00 ft / 3.96 m
    - Stern:  13.00 ft / 3.96 m
    - Average freeboard: 16.17 ft / 4.93 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 201.7 %
  - Above water (accommodation/working, high = better): 125.2 %
 Waterplane Area: 7,280 Square feet or 676 Square metres
 Displacement factor (Displacement / loading): 55 %
 Structure weight / hull surface area: 36 lbs/sq ft or 176 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.46
  - Longitudinal: 3.24
  - Overall: 0.56
 Hull space for machinery, storage, compartmentation is extremely poor
 Room for accommodation and workspaces is excellent