Aidhm Ghinearálta Frigates

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C-Class

Cathryn Class, Irish Frigate laid down 1920 (Engine 1912)

Displacement:
   500 t light; 528 t standard; 603 t normal; 663 t full load

Dimensions: Length overall / water x beam x draught
   230.00 ft / 225.00 ft x 20.00 ft x 10.00 ft (normal load)
   70.11 m / 68.58 m x 6.10 m  x 3.05 m

Armament:
     3 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1920 Model
     Quick firing guns in deck mounts
     on centreline ends, majority aft, 1 raised mount aft
     6 - 0.98" / 25.0 mm guns (3x2 guns), 0.48lbs / 0.22kg shells, 1920 Model
     Machine guns in deck mounts
     on centreline, all amidships
     4 - 0.98" / 25.0 mm guns in single mounts, 0.48lbs / 0.22kg shells, 1920 Model
     Machine guns in deck mounts
     on side ends, evenly spread
   Weight of broadside 101 lbs / 46 kg
   Shells per gun, main battery: 275
   3 - 21.0" / 533.4 mm above water torpedoes

Armour:
  - Gun armour:    Face (max)    Other gunhouse (avg)    Barbette/hoist (max)
   Main:    1.00" / 25 mm          -                  -
   2nd:    0.50" / 13 mm          -                  -
   3rd:    0.50" / 13 mm          -                  -

  - Conning tower: 1.00" / 25 mm

Machinery:
   Diesel Internal combustion motors,
   Direct drive, 2 shafts, 11,237 shp / 8,382 Kw = 27.00 kts
   Range 3,000nm at 12.60 kts
   Bunker at max displacement = 135 tons

Complement:
   60 - 79

Cost:
   £0.157 million / $0.629 million

Distribution of weights at normal displacement:
   Armament: 13 tons, 2.1 %
   Armour: 9 tons, 1.5 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 7 tons, 1.2 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 2 tons, 0.3 %
   Machinery: 275 tons, 45.6 %
   Hull, fittings & equipment: 158 tons, 26.3 %
   Fuel, ammunition & stores: 103 tons, 17.1 %
   Miscellaneous weights: 45 tons, 7.5 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     160 lbs / 73 Kg = 5.0 x 4.0 " / 102 mm shells or 0.2 torpedoes
   Stability (Unstable if below 1.00): 1.18
   Metacentric height 0.6 ft / 0.2 m
   Roll period: 10.8 seconds
   Steadiness    - As gun platform (Average = 50 %): 51 %
           - Recoil effect (Restricted arc if above 1.00): 0.45
   Seaboat quality  (Average = 1.00): 1.12

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.469
   Length to Beam Ratio: 11.25 : 1
   'Natural speed' for length: 15.00 kts
   Power going to wave formation at top speed: 68 %
   Trim (Max stability = 0, Max steadiness = 100): 45
   Bow angle (Positive = bow angles forward): 18.45 degrees
   Stern overhang: -2.00 ft / 0.61 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:        15.00 ft / 4.57 m
      - Forecastle (10 %):    14.00 ft / 4.27 m
      - Mid (30 %):        14.00 ft / 4.27 m (9.00 ft / 2.74 m aft of break)
      - Quarterdeck (15 %):    9.00 ft / 2.74 m
      - Stern:        9.00 ft / 2.74 m
      - Average freeboard:    10.54 ft / 3.21 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space    - Hull below water (magazines/engines, low = better): 172.7 %
       - Above water (accommodation/working, high = better): 51.7 %
   Waterplane Area: 2,917 Square feet or 271 Square metres
   Displacement factor (Displacement / loading): 57 %
   Structure weight / hull surface area: 22 lbs/sq ft or 106 Kg/sq metre
   Hull strength (Relative):
       - Cross-sectional: 0.50
       - Longitudinal: 3.10
       - Overall: 0.60
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is cramped

25 tons long range wireless
10 tons for mines
6 tons 21inch torpedoes
4 tons construction reserve and expantion room (will most likely vary by individual ship as to use)
Trial speed: 29 knts

Ships: Cathryn, Catelyn, Cassidy, Catriona, Colleen, Corisa (All to be layed down by 1/1/1921 starting 1/1/1920)