RLT-1 Armed Trawler

[Jeremy]

A small number of civilian trawlers were requisitioned (built to mercantile standards) to serve as coastal ASW patrol boats. Equipped with hydrophones, light depth charges and a limited AA capability, the trawlers were considered a stop-gap before proper subchasers and patrol boats could be designed and built.

RLT-1, Laksmanavati Armed Trawler, laid down 1927

Displacement:
   348 t light; 358 t standard; 374 t normal; 387 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (173.03 ft / 170.60 ft) x 23.62 ft x (5.91 / 6.07 ft)
   (52.74 m / 52.00 m) x 7.20 m  x (1.80 / 1.85 m)

Armament:
      2 - 1.57" / 40.0 mm 39.0 cal guns - 1.85lbs / 0.84kg shells, 900 per gun
     Anti-air guns in deck mount, 1927 Model
     1 x Twin mount on centreline, forward deck forward
      2 - 0.47" / 12.0 mm 90.0 cal guns - 0.07lbs / 0.03kg shells, 2,000 per gun
     Machine guns in deck mounts, 1927 Model
     2 x Single mounts on sides amidships
      Weight of broadside 4 lbs / 2 kg

Machinery:
   Diesel Internal combustion motors,
   Geared drive, 1 shaft, 940 shp / 701 Kw = 15.00 kts
   Range 2,000nm at 10.00 kts
   Bunker at max displacement = 30 tons

Complement:
   42 - 55

Cost:
   £0.060 million / $0.242 million

Distribution of weights at normal displacement:
   Armament: 1 tons, 0.2 %
      - Guns: 1 tons, 0.2 %
   Machinery: 30 tons, 7.9 %
   Hull, fittings & equipment: 120 tons, 32.0 %
   Fuel, ammunition & stores: 26 tons, 6.9 %
   Miscellaneous weights: 198 tons, 52.9 %
      - Hull below water: 24 tons
      - Hull above water: 20 tons
      - On freeboard deck: 154 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     1,195 lbs / 542 Kg = 612.1 x 1.6 " / 40 mm shells or 1.3 torpedoes
   Stability (Unstable if below 1.00): 1.15
   Metacentric height 0.8 ft / 0.2 m
   Roll period: 11.4 seconds
   Steadiness   - As gun platform (Average = 50 %): 50 %
         - Recoil effect (Restricted arc if above 1.00): 0.01
   Seaboat quality  (Average = 1.00): 1.44

Hull form characteristics:
   Hull has raised forecastle,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.550 / 0.554
   Length to Beam Ratio: 7.22 : 1
   'Natural speed' for length: 13.06 kts
   Power going to wave formation at top speed: 52 %
   Trim (Max stability = 0, Max steadiness = 100): 35
   Bow angle (Positive = bow angles forward): 10.00 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 %,  13.78 ft / 4.20 m,  10.83 ft / 3.30 m
      - Forward deck:   30.00 %,  8.20 ft / 2.50 m,  6.56 ft / 2.00 m
      - Aft deck:   35.00 %,  6.56 ft / 2.00 m,  6.56 ft / 2.00 m
      - Quarter deck:   15.00 %,  6.56 ft / 2.00 m,  7.87 ft / 2.40 m
      - Average freeboard:      8.00 ft / 2.44 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 41.1 %
      - Above water (accommodation/working, high = better): 85.9 %
   Waterplane Area: 2,728 Square feet or 253 Square metres
   Displacement factor (Displacement / loading): 144 %
   Structure weight / hull surface area: 29 lbs/sq ft or 139 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.95
      - Longitudinal: 1.84
      - Overall: 1.02
   Excellent machinery, storage, compartmentation space
   Cramped accommodation and workspace room
   Good seaboat, rides out heavy weather easily

Fittings:
-9 t: Diesel engines (vital)
-15 t: Enhanced hydrophones (vital)
-2 t: 2x Thornycroft DC throwers (on deck)
-2 t: 20x 90 kg DC (on deck)
-20 + 150 t: Cargo space / Weight reserve (hull + on deck)

Range: 3700 (geared bonus + diesel bonus)