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Sunday, September 02, 2007

The GB/PG/1915 design

I had thought that this might have been a German design, but then I realized that all the fast gunboats were specified by my friend Cliff, for the British. This is a very "edgy" design, as the speed is specified to be 36 knots. The guns are not listed, but at this point, suspect that the guns should be 3-4in, not 3-5in, but I believe that 5in were what was planned. The ship really does not work in Springsharp, but by doing some bad things, I was able to make the ship work. I was helped by the fact that the only dimension specified was the 275ft length. The hacks that I used were to increase the draft to a unrealistic amount and I used lightweight 5in/35 QF guns. The range is also very low. It would not be a useful ship for long range cruising. I would only want to use the ship with the Dover Patrol or the Harwich Force. This is the Springsharp report:
GB/PG/1915, Great Britain Fast Gunboat laid down 1915 (Engine 1950)

Displacement:
 980 t light; 1,011 t standard; 1,062 t normal; 1,104 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (277.42 ft / 275.00 ft) x 25.00 ft x (14.50 / 14.83 ft)
 (84.56 m / 83.82 m) x 7.62 m  x (4.42 / 4.52 m)

Armament:
      3 - 5.00" / 127 mm 35.0 cal guns - 58.60lbs / 26.58kg shells, 100 per gun
   Quick firing guns in deck and hoist mounts, 1915 Model
   3 x Single mounts on centreline ends, majority forward
  1 raised mount - superfiring
   Main guns limited to end-on fire
      Weight of broadside 176 lbs / 80 kg

Armour:
   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 1.00" / 25 mm 1.00" / 25 mm  1.00" / 25 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 2 shafts, 38,772 shp / 28,924 Kw = 36.00 kts
 Range 1,700nm at 14.00 kts
 Bunker at max displacement = 93 tons

Complement:
 92 - 120

Cost:
 £0.184 million / $0.734 million

Distribution of weights at normal displacement:
 Armament: 37 tons, 3.5 %
 Armour: 21 tons, 2.0 %
    - Armament: 21 tons, 2.0 %
 Machinery: 564 tons, 53.0 %
 Hull, fittings & equipment: 358 tons, 33.7 %
 Fuel, ammunition & stores: 83 tons, 7.8 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   224 lbs / 102 Kg = 3.6 x 5.0 " / 127 mm shells or 0.2 torpedoes
 Stability (Unstable if below 1.00): 1.01
 Metacentric height 0.6 ft / 0.2 m
 Roll period: 13.2 seconds
 Steadiness - As gun platform (Average = 50 %): 51 %
   - Recoil effect (Restricted arc if above 1.00): 1.15
 Seaboat quality  (Average = 1.00): 1.09

Hull form characteristics:
 Hull has rise forward of midbreak,
   a normal bow and large transom stern
 Block coefficient (normal/deep): 0.373 / 0.379
 Length to Beam Ratio: 11.00 : 1
 'Natural speed' for length: 19.11 kts
 Power going to wave formation at top speed: 73 %
 Trim (Max stability = 0, Max steadiness = 100): 47
 Bow angle (Positive = bow angles forward): 6.00 degrees
 Stern overhang: 0.00 ft / 0.00 m
 Freeboard (% = length of deck as a percentage of waterline length):
    Fore end,  Aft end
    - Forecastle: 20.00 %,  23.00 ft / 7.01 m,  21.00 ft / 6.40 m
    - Forward deck: 13.00 %,  21.00 ft / 6.40 m,  21.00 ft / 6.40 m
    - Aft deck: 54.00 %,  13.00 ft / 3.96 m,  13.00 ft / 3.96 m
    - Quarter deck: 13.00 %,  13.00 ft / 3.96 m,  13.00 ft / 3.96 m
    - Average freeboard:  15.80 ft / 4.82 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 182.3 %
  - Above water (accommodation/working, high = better): 130.1 %
 Waterplane Area: 4,318 Square feet or 401 Square metres
 Displacement factor (Displacement / loading): 53 %
 Structure weight / hull surface area: 28 lbs/sq ft or 138 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.39
  - Longitudinal: 6.85
  - Overall: 0.52
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent

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