GMB-A

[TacCovert4]

GMB-A, Aztec Fast Mine Boat laid down 1914

Displacement:
   500 t light; 514 t standard; 587 t normal; 646 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (291.57 ft / 288.71 ft) x 24.11 ft x (7.38 / 7.86 ft)
   (88.87 m / 88.00 m) x 7.35 m  x (2.25 / 2.40 m)

Armament:
      2 - 2.76" / 70.0 mm 50.0 cal guns - 11.09lbs / 5.03kg shells, 160 per gun
     Quick firing guns in deck mounts, 1914 Model
     2 x Single mounts on centreline, forward evenly spread
      1 raised mount
      4 - 0.31" / 8.0 mm 70.0 cal guns - 0.02lbs / 0.01kg shells, 2,000 per gun
     Machine guns in deck mounts, 1914 Model
     2 x Twin mounts on sides, forward deck aft
      Weight of broadside 22 lbs / 10 kg

Machinery:
   Oil fired boilers, steam turbines,
   Direct drive, 2 shafts, 13,712 shp / 10,229 Kw = 29.75 kts
   Range 5,500nm at 10.00 kts
   Bunker at max displacement = 132 tons

Complement:
   59 - 77

Cost:
   £0.077 million / $0.309 million

Distribution of weights at normal displacement:
   Armament: 5 tons, 0.8 %
      - Guns: 5 tons, 0.8 %
   Machinery: 299 tons, 51.0 %
   Hull, fittings & equipment: 145 tons, 24.6 %
   Fuel, ammunition & stores: 87 tons, 14.9 %
   Miscellaneous weights: 51 tons, 8.7 %
      - On freeboard deck: 50 tons
      - Above deck: 1 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     168 lbs / 76 Kg = 16.0 x 2.8 " / 70 mm shells or 0.2 torpedoes
   Stability (Unstable if below 1.00): 1.22
   Metacentric height 0.9 ft / 0.3 m
   Roll period: 11.0 seconds
   Steadiness   - As gun platform (Average = 50 %): 54 %
         - Recoil effect (Restricted arc if above 1.00): 0.06
   Seaboat quality  (Average = 1.00): 0.80

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.400 / 0.413
   Length to Beam Ratio: 11.97 : 1
   'Natural speed' for length: 16.99 kts
   Power going to wave formation at top speed: 62 %
   Trim (Max stability = 0, Max steadiness = 100): 68
   Bow angle (Positive = bow angles forward): 15.00 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 %,  10.66 ft / 3.25 m,  9.84 ft / 3.00 m
      - Forward deck:   30.00 %,  9.84 ft / 3.00 m,  8.20 ft / 2.50 m
      - Aft deck:   35.00 %,  8.20 ft / 2.50 m,  8.20 ft / 2.50 m
      - Quarter deck:   15.00 %,  8.20 ft / 2.50 m,  7.38 ft / 2.25 m
      - Average freeboard:      8.78 ft / 2.68 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 167.0 %
      - Above water (accommodation/working, high = better): 118.7 %
   Waterplane Area: 4,286 Square feet or 398 Square metres
   Displacement factor (Displacement / loading): 52 %
   Structure weight / hull surface area: 20 lbs/sq ft or 100 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.50
      - Longitudinal: 0.74
      - Overall: 0.52
   Cramped machinery, storage, compartmentation space
   Adequate accommodation and workspace room
   Poor seaboat, wet and uncomfortable, reduced performance in heavy weather


50t - 50 x Mines

1t - 1908 Fire Control