Patrol Craft: Sloops, cutters, korweta, coastal escorts, etc.

[The Rock Doctor]

Bremen Class Sloop

The B-class sloops are intended to be open-ocean escorts for trade protection and, where appropriate, defence of naval auxiliaries.

The hull form is based on the Liedtke class sloops, although it is finer and faster.  The forward 100mm mounting might get wet, but it is 6 metres above sea level, behind a breakwater, and fully enclosed, so hopefully it won't be too bad.  The aft weapons are superfiring to keep them dry as well.

The armament could be heavier.  It's thought that the 100mm might be easier to handle than the larger 130mm shells if the ship is bouncing around in mid-Atlantic conditions, but it will put the hurt on a surface submarine or an attacking aircraft.  Two 2-gun mounts were considered but I thought it might make for a crowded ship in terms of crew members so stuck with singles.  The ship is not really intended to take on anti-ship duties, hence the lack of torpedoes and the big guns; ideally, they'll be in convoy with bigger guys to do that stuff.

The inclusion of a howitzer is unusual enough but it's a modern-ish piece and worth trying as an ASW weapon.  Worse comes to worst, it gets yanked out and replaced by another 100mm, 50mm, or Hedgehog analogue in a future refit.

The ship has a towing rig aft to help with search and rescue, and I might use some of the unallocated miscellaneous weight for either fire monitors or temporary accommodation for survivors, not sure yet.

Bremen, laid down 1931
Benin, laid down 1931
Berlin, laid down 1932
Braunschweig, laid down 1932
Bronderslov, laid down 1933
Burgsvik, laid down 1933
Bollnas, laid down 1933
Bispfors, laid down 1933

Enter ship name, Enter country Enter ship type laid down 1931

Displacement:
   964 t light; 1,017 t standard; 1,153 t normal; 1,263 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (249.74 ft / 236.22 ft) x 29.53 ft x (11.81 / 12.64 ft)
   (76.12 m / 72.00 m) x 9.00 m  x (3.60 / 3.85 m)

Armament:
      2 - 3.94" / 100 mm 45.0 cal guns - 30.78lbs / 13.96kg shells, 400 per gun
     Dual purpose guns in deck mounts, 1931 Model
     1 x Single mount on centreline, forward deck forward
     1 x Single mount on centreline, aft deck centre
      1 raised mount aft
      2 - 1.97" / 50.0 mm 60.0 cal guns - 4.19lbs / 1.90kg shells, 1,500 per gun
     Anti-air guns in deck mount, 1931 Model
     1 x Twin mount on centreline, aft deck forward
      1 double raised mount
      4 - 0.59" / 15.0 mm 90.0 cal guns - 0.11lbs / 0.05kg shells, 5,000 per gun
     Machine guns in deck mounts, 1931 Model
     2 x Twin mounts on sides, forward deck aft
      2 double raised mounts
      1 - 5.91" / 150 mm 25.0 cal gun - 93.52lbs / 42.42kg shells, 150 per gun
     Breech loading gun in deck mount, 1931 Model
     1 x Single mount on centreline, forward deck forward
      1 raised mount
      Weight of broadside 164 lbs / 74 kg

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.79" / 20 mm   0.59" / 15 mm            -
   2nd:   0.59" / 15 mm         -               -
   3rd:   0.59" / 15 mm         -               -
   4th:   0.79" / 20 mm   0.59" / 15 mm            -

Machinery:
   Oil fired boilers, steam turbines,
   Electric cruising motors plus geared drives, 2 shafts, 10,724 shp / 8,000 Kw = 24.03 kts
   Range 3,600nm at 15.00 kts
   Bunker at max displacement = 246 tons

Complement:
   98 - 128

Cost:
   £0.370 million / $1.482 million

Distribution of weights at normal displacement:
   Armament: 22 tons, 1.9%
      - Guns: 22 tons, 1.9%
   Armour: 14 tons, 1.2%
      - Armament: 14 tons, 1.2%
   Machinery: 321 tons, 27.8%
   Hull, fittings & equipment: 358 tons, 31.0%
   Fuel, ammunition & stores: 190 tons, 16.4%
   Miscellaneous weights: 249 tons, 21.6%
      - Hull below water: 105 tons
      - On freeboard deck: 99 tons
      - Above deck: 45 tons

Fittings:
-3 t:  Fire control (AD)
-5 t:  Night-fighting doodads (AD)
-25 t:  Long-range radio (AD)
-20 t:  ASW munitions (4 DCT + DC) (FD)
-25 t:  Towing rig (FD)
-54 t:  Weight reserve/unassigned (FD)
-80 t:  Electric drive (BW)
-15 t:  Enhanced hydrophone package (BW)
-10 t:  Sonar (BW)

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     1,128 lbs / 512 Kg = 37.0 x 3.9 " / 100 mm shells or 0.5 torpedoes
   Stability (Unstable if below 1.00): 1.19
   Metacentric height 1.1 ft / 0.3 m
   Roll period: 11.8 seconds
   Steadiness   - As gun platform (Average = 50 %): 61 %
         - Recoil effect (Restricted arc if above 1.00): 0.37
   Seaboat quality  (Average = 1.00): 1.79

Hull form characteristics:
   Hull has rise forward of midbreak,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.490 / 0.501
   Length to Beam Ratio: 8.00 : 1
   'Natural speed' for length: 15.37 kts
   Power going to wave formation at top speed: 67 %
   Trim (Max stability = 0, Max steadiness = 100): 34
   Bow angle (Positive = bow angles forward): 20.00 degrees
   Stern overhang: 4.92 ft / 1.50 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00%,  23.62 ft / 7.20 m,  19.69 ft / 6.00 m
      - Forward deck:   30.00%,  19.69 ft / 6.00 m,  19.69 ft / 6.00 m
      - Aft deck:   35.00%,  11.81 ft / 3.60 m,  11.81 ft / 3.60 m
      - Quarter deck:   15.00%,  11.81 ft / 3.60 m,  11.81 ft / 3.60 m
      - Average freeboard:      16.06 ft / 4.90 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 107.7%
      - Above water (accommodation/working, high = better): 138.3%
   Waterplane Area: 4,605 Square feet or 428 Square metres
   Displacement factor (Displacement / loading): 120%
   Structure weight / hull surface area: 33 lbs/sq ft or 162 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.59
      - Longitudinal: 6.96
      - Overall: 0.75
   Adequate machinery, storage, compartmentation space
   Excellent accommodation and workspace room
   Excellent seaboat, comfortable, can fire her guns in the heaviest weather

10,000nm @ 10 kts

[The Rock Doctor]

Type 1931 Coastal Escort

This update to the reasonably popular Type 1926 class adds a DP main gun, puts the AA in a twin mount, and adds a basic minesweeping capabilty.

EP-55 to -57, laid down 1931
EP-58 to -63 laid down 1931
EP-64 to -66, laid down 1932
EP-67 to -69, laid down 1932
EP-70 to -72, laid down 1933
EP-73 to -75, laid down 1933
EP-76 to -78, laid down 1934
EP-79 to -81, laid down 1934

Enter ship name, Enter country Enter ship type laid down 1931

Displacement:
   261 t light; 278 t standard; 301 t normal; 319 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (157.01 ft / 147.64 ft) x 19.69 ft x (7.87 / 8.21 ft)
   (47.86 m / 45.00 m) x 6.00 m  x (2.40 / 2.50 m)

Armament:
      1 - 2.95" / 75.0 mm 45.0 cal gun - 12.98lbs / 5.89kg shells, 400 per gun
     Dual purpose gun in deck mount, 1931 Model
     1 x Single mount on centreline, forward deck forward
      1 raised mount
      2 - 1.97" / 50.0 mm 60.0 cal guns - 4.18lbs / 1.89kg shells, 1,500 per gun
     Anti-air guns in deck mount, 1931 Model
     1 x Twin mount on centreline, aft deck centre
      1 raised mount
      4 - 0.59" / 15.0 mm 90.0 cal guns - 0.12lbs / 0.05kg shells, 5,000 per gun
     Machine guns in deck mounts, 1931 Model
     2 x Twin mounts on sides amidships
      2 raised mounts
      Weight of broadside 22 lbs / 10 kg

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.79" / 20 mm   0.12" / 3 mm            -
   2nd:   0.79" / 20 mm   0.12" / 3 mm            -
   3rd:   0.59" / 15 mm         -               -

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 2 shafts, 2,815 shp / 2,100 Kw = 20.18 kts
   Range 3,500nm at 10.00 kts
   Bunker at max displacement = 41 tons

Complement:
   35 - 46

Cost:
   £0.098 million / $0.391 million

Distribution of weights at normal displacement:
   Armament: 5 tons, 1.7%
      - Guns: 5 tons, 1.7%
   Armour: 4 tons, 1.2%
      - Armament: 4 tons, 1.2%
   Machinery: 84 tons, 28.0%
   Hull, fittings & equipment: 91 tons, 30.2%
   Fuel, ammunition & stores: 40 tons, 13.2%
   Miscellaneous weights: 77 tons, 25.6%
      - Hull below water: 25 tons
      - Hull above water: 6 tons
      - On freeboard deck: 45 tons
      - Above deck: 1 tons

Fittings:
-15t:  Enhanced hydrophone package (BW)
-10t:  Sonar (BW)
-4t:  2x1 450mm torpedoes, fixed to fire just off the bows (FD)
-8t:  ASW weapons (FD)
-2t:  Nightfighting doodads (FD) I should put that above deck.
-6 + 6 t:  Weight reserve (BD/FD)
-25 t:  Minesweeping kit (FD)
-1 t:  1918 fire control (AD)

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     265 lbs / 120 Kg = 20.6 x 3.0 " / 75 mm shells or 0.3 torpedoes
   Stability (Unstable if below 1.00): 1.13
   Metacentric height 0.5 ft / 0.2 m
   Roll period: 11.2 seconds
   Steadiness   - As gun platform (Average = 50 %): 60 %
         - Recoil effect (Restricted arc if above 1.00): 0.21
   Seaboat quality  (Average = 1.00): 1.45

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.460 / 0.468
   Length to Beam Ratio: 7.50 : 1
   'Natural speed' for length: 12.15 kts
   Power going to wave formation at top speed: 69 %
   Trim (Max stability = 0, Max steadiness = 100): 41
   Bow angle (Positive = bow angles forward): 20.00 degrees
   Stern overhang: 3.28 ft / 1.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00%,  16.73 ft / 5.10 m,  12.80 ft / 3.90 m
      - Forward deck:   20.00%,  12.80 ft / 3.90 m,  8.86 ft / 2.70 m
      - Aft deck:   45.00%,  8.86 ft / 2.70 m,  8.86 ft / 2.70 m
      - Quarter deck:   15.00%,  8.86 ft / 2.70 m,  8.86 ft / 2.70 m
      - Average freeboard:      10.35 ft / 3.16 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 110.3%
      - Above water (accommodation/working, high = better): 96.3%
   Waterplane Area: 1,869 Square feet or 174 Square metres
   Displacement factor (Displacement / loading): 114%
   Structure weight / hull surface area: 21 lbs/sq ft or 103 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.59
      - Longitudinal: 6.98
      - Overall: 0.75
   Caution: Hull subject to strain in open-sea
   Adequate machinery, storage, compartmentation space
   Adequate accommodation and workspace room
   Good seaboat, rides out heavy weather easily

[The Rock Doctor]

Type 1932 Korweta

The Union is getting back to korwetas after a pause of a few years as it built up an inventory of coastal escorts and harbour defence boats.  The korweta is well-armed for its size and capable of operating in open oceanic conditions...to a point...but lacks the endurance to actually cross oceans.

As many as twenty could be built over the coming years as the navy replaces the big old batch of vintage patrol cutters in home waters and augments its patrol groups in various colonial settings.

KS-33 to -34, laid down 1932
KS-35, laid down 1932
KS-36, laid down 1933
KS-37, laid down 1933
KS-38, laid down 1934
KS-39, laid down 1934


Enter ship name, Enter country Enter ship type laid down 1932

Displacement:
   499 t light; 533 t standard; 603 t normal; 660 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (184.33 ft / 172.24 ft) x 24.61 ft x (10.17 / 10.88 ft)
   (56.18 m / 52.50 m) x 7.50 m  x (3.10 / 3.32 m)

Armament:
      2 - 3.94" / 100 mm 45.0 cal guns - 30.77lbs / 13.96kg shells, 400 per gun
     Dual purpose guns in deck mounts, 1932 Model
     2 x Single mounts on centreline ends, evenly spread
      2 - 1.97" / 50.0 mm 60.0 cal guns - 4.18lbs / 1.89kg shells, 1,500 per gun
     Anti-air guns in deck mount, 1932 Model
     1 x Twin mount on centreline, aft deck centre
      1 raised mount
      4 - 0.59" / 15.0 mm 90.0 cal guns - 0.12lbs / 0.05kg shells, 5,000 per gun
     Machine guns in deck mounts, 1932 Model
     2 x Twin mounts on sides amidships
      2 raised mounts
      Weight of broadside 70 lbs / 32 kg

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.79" / 20 mm   0.59" / 15 mm            -
   2nd:   0.59" / 15 mm         -               -
   3rd:   0.59" / 15 mm         -               -

Machinery:
   Oil fired boilers, steam turbines,
   Electric cruising motors plus geared drives, 2 shafts, 5,362 shp / 4,000 Kw = 21.43 kts
   Range 2,500nm at 15.00 kts
   Bunker at max displacement = 127 tons

Complement:
   60 - 79

Cost:
   £0.197 million / $0.789 million

Distribution of weights at normal displacement:
   Armament: 14 tons, 2.4%
      - Guns: 14 tons, 2.4%
   Armour: 10 tons, 1.6%
      - Armament: 10 tons, 1.6%
   Machinery: 158 tons, 26.2%
   Hull, fittings & equipment: 204 tons, 33.7%
   Fuel, ammunition & stores: 105 tons, 17.3%
   Miscellaneous weights: 113 tons, 18.7%
      - Hull below water: 65 tons
      - On freeboard deck: 41 tons
      - Above deck: 7 tons

Fittings:
-40 t:  Electric drive (BW)
-25 t:  Sonar and enhanced hydrophone package (BW)
-20 t:  ASW fit TBD (FD)
-21 t:  Weight reserve/TBD (FD)
-2 t:  Fire control, such as it is (AD)
-5 t:  Nightfighting doodads (AD)

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     674 lbs / 306 Kg = 22.1 x 3.9 " / 100 mm shells or 0.4 torpedoes
   Stability (Unstable if below 1.00): 1.20
   Metacentric height 0.9 ft / 0.3 m
   Roll period: 11.2 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.29
   Seaboat quality  (Average = 1.00): 2.00

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.490 / 0.501
   Length to Beam Ratio: 7.00 : 1
   'Natural speed' for length: 13.12 kts
   Power going to wave formation at top speed: 70 %
   Trim (Max stability = 0, Max steadiness = 100): 35
   Bow angle (Positive = bow angles forward): 20.00 degrees
   Stern overhang: 4.92 ft / 1.50 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00%,  19.69 ft / 6.00 m,  15.75 ft / 4.80 m
      - Forward deck:   30.00%,  15.75 ft / 4.80 m,  15.75 ft / 4.80 m
      - Aft deck:   35.00%,  15.75 ft / 4.80 m,  15.75 ft / 4.80 m
      - Quarter deck:   15.00%,  15.75 ft / 4.80 m,  15.75 ft / 4.80 m
      - Average freeboard:      16.06 ft / 4.90 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 106.3%
      - Above water (accommodation/working, high = better): 139.9%
   Waterplane Area: 2,798 Square feet or 260 Square metres
   Displacement factor (Displacement / loading): 127%
   Structure weight / hull surface area: 26 lbs/sq ft or 125 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.52
      - Longitudinal: 17.48
      - Overall: 0.75
   Caution: Hull subject to strain in open-sea
   Adequate machinery, storage, compartmentation space
   Excellent accommodation and workspace room
   Ship has slow, easy roll, a good, steady gun platform
   Excellent seaboat, comfortable, can fire her guns in the heaviest weather

[The Rock Doctor]

Type 1933 Gunboat

The Union Navy's thinking about a new run of the so-called guntubs, the teeny-weeny shallow-draft boats with a 75mm gun on them.

The first batch, from 1929, was about supplying a bit of fire-support capability for korsarz-based amphibious raids.  This batch would be about supporting riverine operations, working with the small depot ships and other small craft in places where even the usual array of river gunboats can't reach due to draft.

The top speed and cruising speed have been reduced but the bunkerage increased.  A bit of protection is added to the main gun and the control room.  Additionally a third machine gun has been mounted atop the control room for bonus firepower.

The miscellaneous weight is for the diesel engines.

Units #1 to #4, laid down 1933
Units #5 to #8, laid down 1934

Enter ship name, Enter country Enter ship type laid down 1933

Displacement:
    19 t light; 21 t standard; 22 t normal; 22 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
    (57.81 ft / 52.49 ft) x 13.12 ft x (2.46 / 2.49 ft)
    (17.62 m / 16.00 m) x 4.00 m  x (0.75 / 0.76 m)

Armament:
      1 - 2.95" / 75.0 mm 45.0 cal gun - 12.98lbs / 5.89kg shells, 150 per gun
      Quick firing gun in deck mount, 1933 Model
      1 x Single mount on centreline, aft deck centre
      1 - 0.59" / 15.0 mm 90.0 cal gun - 0.12lbs / 0.05kg shells, 2,000 per gun
      Machine gun in deck mount, 1933 Model
      1 x Single mount on centreline, forward deck forward
        1 raised mount
      2 - 0.59" / 15.0 mm 90.0 cal guns - 0.12lbs / 0.05kg shells, 2,000 per gun
      Machine guns in deck mounts, 1933 Model
      2 x Single mounts on sides amidships
      Weight of broadside 13 lbs / 6 kg

Armour:
  - Gun armour:    Face (max)    Other gunhouse (avg)    Barbette/hoist (max)
    Main:    0.59" / 15 mm          -                  -

  - Conning towers: Forward 0.59" / 15 mm, Aft 0.00" / 0 mm

Machinery:
    Diesel Internal combustion motors,
    Geared drive, 2 shafts, 134 shp / 100 Kw = 12.34 kts
    Range 200nm at 10.00 kts
    Bunker at max displacement = 1 tons

Complement:
    4 - 6

Cost:
    £0.010 million / $0.038 million

Distribution of weights at normal displacement:
    Armament: 3 tons, 12.9 %
      - Guns: 3 tons, 12.9 %
    Armour: 1 tons, 6.4 %
      - Armament: 1 tons, 5.9 %
      - Conning Tower: 0 tons, 0.5 %
    Machinery: 4 tons, 17.9 %
    Hull, fittings & equipment: 9 tons, 42.7 %
    Fuel, ammunition & stores: 2 tons, 10.9 %
    Miscellaneous weights: 2 tons, 9.2 %
      - Hull below water: 2 tons

Overall survivability and seakeeping ability:
    Survivability (Non-critical penetrating hits needed to sink ship):
      35 lbs / 16 Kg = 2.7 x 3.0 " / 75 mm shells or 0.1 torpedoes
    Stability (Unstable if below 1.00): 1.13
    Metacentric height 0.3 ft / 0.1 m
    Roll period: 10.1 seconds
    Steadiness    - As gun platform (Average = 50 %): 70 %
            - Recoil effect (Restricted arc if above 1.00): 0.39
    Seaboat quality  (Average = 1.00): 0.97

Hull form characteristics:
    Hull has a flush deck,
      a normal bow and a cruiser stern
    Block coefficient (normal/deep): 0.450 / 0.452
    Length to Beam Ratio: 4.00 : 1
    'Natural speed' for length: 7.25 kts
    Power going to wave formation at top speed: 74 %
    Trim (Max stability = 0, Max steadiness = 100): 73
    Bow angle (Positive = bow angles forward): 20.00 degrees
    Stern overhang: 1.97 ft / 0.60 m
    Freeboard (% = length of deck as a percentage of waterline length):
                Fore end,    Aft end
      - Forecastle:    20.00 %,  9.19 ft / 2.80 m,  7.22 ft / 2.20 m
      - Forward deck:    20.00 %,  7.22 ft / 2.20 m,  5.25 ft / 1.60 m
      - Aft deck:    45.00 %,  5.25 ft / 1.60 m,  5.25 ft / 1.60 m
      - Quarter deck:    15.00 %,  5.25 ft / 1.60 m,  5.25 ft / 1.60 m
      - Average freeboard:        6.00 ft / 1.83 m

Ship space, strength and comments:
    Space    - Hull below water (magazines/engines, low = better): 105.9 %
        - Above water (accommodation/working, high = better): 116.2 %
    Waterplane Area: 439 Square feet or 41 Square metres
    Displacement factor (Displacement / loading): 116 %
    Structure weight / hull surface area: 14 lbs/sq ft or 67 Kg/sq metre
    Hull strength (Relative):
        - Cross-sectional: 0.57
        - Longitudinal: 16.57
        - Overall: 0.80
    Caution: Hull subject to strain in open-sea
    Adequate machinery, storage, compartmentation space
    Adequate accommodation and workspace room
    Ship has slow, easy roll, a good, steady gun platform
    Poor seaboat, wet and uncomfortable, reduced performance in heavy weather

[The Rock Doctor]

Espoo Class Sloop

Espoo, laid down 1934
Essen, laid down 1934
Eko, laid down 1934
Enugu, laid down 1934