Riverine Craft

[The Rock Doctor]

Time to break this out separately.

[The Rock Doctor]

Type 1895 Armored Patrol Boat

30 built since 1895 for patrol functions in the northern and eastern Baltic and up river systems such as the Neva.  Waterline armor and extra hull strength permits some degree of interaction with ice, though these are emphatically not icebreakers.

Enter ship name, Enter country Enter ship type laid down 1896

Displacement:
   80 t light; 82 t standard; 83 t normal; 84 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (98.43 ft / 98.43 ft) x 16.40 ft x (3.28 / 3.31 ft)
   (30.00 m / 30.00 m) x 5.00 m  x (1.00 / 1.01 m)

Armament:
      1 - 1.97" / 50.0 mm 40.0 cal gun - 3.66lbs / 1.66kg shells, 100 per gun
     Quick firing gun in deck mount, 1896 Model
     1 x Single mount on centreline, forward deck centre
      3 - 0.39" / 10.0 mm 40.0 cal guns - 0.03lbs / 0.01kg shells, 5,000 per gun
     Machine guns in deck mounts, 1896 Model
     1 x Single mount on centreline, aft deck centre
     2 x Single mounts on sides amidships
      Weight of broadside 4 lbs / 2 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   0.79" / 20 mm     63.98 ft / 19.50 m   4.86 ft / 1.48 m
   Ends:   0.79" / 20 mm     34.42 ft / 10.49 m   4.86 ft / 1.48 m
     Main Belt covers 100 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.39" / 10 mm   0.20" / 5 mm            -
   2nd:   0.20" / 5 mm         -               -

Machinery:
   Coal fired boilers, simple reciprocating steam engines,
   Direct drive, 2 shafts, 42 ihp / 32 Kw = 8.00 kts
   Range 500nm at 5.00 kts
   Bunker at max displacement = 2 tons (100% coal)

Complement:
   13 - 17

Cost:
   £0.004 million / $0.016 million

Distribution of weights at normal displacement:
   Armament: 1 tons, 1.0 %
      - Guns: 1 tons, 1.0 %
   Armour: 18 tons, 21.9 %
      - Belts: 16 tons, 18.8 %
      - Armament: 3 tons, 3.1 %
   Machinery: 8 tons, 9.3 %
   Hull, fittings & equipment: 38 tons, 45.8 %
   Fuel, ammunition & stores: 3 tons, 4.1 %
   Miscellaneous weights: 15 tons, 18.0 %
      - On freeboard deck: 15 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     488 lbs / 221 Kg = 127.8 x 2.0 " / 50 mm shells or 1.0 torpedoes
   Stability (Unstable if below 1.00): 1.31
   Metacentric height 0.5 ft / 0.2 m
   Roll period: 9.4 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.04
   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): 0.550 / 0.551
   Length to Beam Ratio: 6.00 : 1
   'Natural speed' for length: 9.92 kts
   Power going to wave formation at top speed: 34 %
   Trim (Max stability = 0, Max steadiness = 100): 35
   Bow angle (Positive = bow angles forward): 0.00 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 %,  6.56 ft / 2.00 m,  6.56 ft / 2.00 m
      - Forward deck:   30.00 %,  6.56 ft / 2.00 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,  6.56 ft / 2.00 m
      - Average freeboard:      6.56 ft / 2.00 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 34.5 %
      - Above water (accommodation/working, high = better): 108.3 %
   Waterplane Area: 1,127 Square feet or 105 Square metres
   Displacement factor (Displacement / loading): 164 %
   Structure weight / hull surface area: 21 lbs/sq ft or 103 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.92
      - Longitudinal: 4.10
      - Overall: 1.06
   Excellent machinery, storage, compartmentation space
   Adequate 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 1901 River Gunboat

34 units built since 1901 for patrol operations along major river systems.  The 75mm piece is a howitzer.

The entire class was scrapped in 1931.

Enter ship name, Enter country Enter ship type laid down 1901

Displacement:
   145 t light; 150 t standard; 151 t normal; 153 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (114.83 ft / 114.83 ft) x 19.69 ft x (3.61 / 3.64 ft)
   (35.00 m / 35.00 m) x 6.00 m  x (1.10 / 1.11 m)

Armament:
      1 - 1.97" / 50.0 mm 40.0 cal gun - 3.66lbs / 1.66kg shells, 100 per gun
     Quick firing gun in deck mount, 1901 Model
     1 x Single mount on centreline, forward deck centre
      4 - 0.39" / 10.0 mm 40.0 cal guns - 0.03lbs / 0.01kg shells, 5,000 per gun
     Machine guns in deck mounts, 1901 Model
     4 x Single mounts on centreline, aft evenly spread
      1 - 2.95" / 75.0 mm 40.0 cal gun - 12.34lbs / 5.60kg shells, 100 per gun
     Breech loading gun in deck mount, 1901 Model
     1 x Single mount on centreline, aft deck centre
      Weight of broadside 16 lbs / 7 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   0.79" / 20 mm     74.64 ft / 22.75 m   5.31 ft / 1.62 m
   Ends:   0.79" / 20 mm     40.16 ft / 12.24 m   5.31 ft / 1.62 m
   Upper:   0.79" / 20 mm     74.64 ft / 22.75 m   4.92 ft / 1.50 m
     Main Belt covers 100 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.39" / 10 mm   0.20" / 5 mm            -
   2nd:   0.20" / 5 mm         -               -
   3rd:   0.39" / 10 mm         -               -

   - Armoured deck - multiple decks:
   For and Aft decks: 0.79" / 20 mm
   Forecastle: 0.39" / 10 mm  Quarter deck: 0.79" / 20 mm

   - Conning towers: Forward 0.79" / 20 mm, Aft 0.00" / 0 mm

Machinery:
   Coal fired boilers, complex reciprocating steam engines,
   Direct drive, 2 shafts, 67 ihp / 50 Kw = 8.15 kts
   Range 500nm at 5.00 kts
   Bunker at max displacement = 4 tons (100% coal)

Complement:
   21 - 28

Cost:
   £0.007 million / $0.029 million

Distribution of weights at normal displacement:
   Armament: 3 tons, 1.8 %
      - Guns: 3 tons, 1.8 %
   Armour: 62 tons, 40.7 %
      - Belts: 33 tons, 21.8 %
      - Armament: 4 tons, 2.6 %
      - Armour Deck: 24 tons, 16.0 %
      - Conning Tower: 0 tons, 0.3 %
   Machinery: 10 tons, 6.8 %
   Hull, fittings & equipment: 49 tons, 32.2 %
   Fuel, ammunition & stores: 6 tons, 4.1 %
   Miscellaneous weights: 22 tons, 14.5 %
      - On freeboard deck: 22 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     810 lbs / 367 Kg = 212.4 x 2.0 " / 50 mm shells or 1.5 torpedoes
   Stability (Unstable if below 1.00): 1.39
   Metacentric height 0.8 ft / 0.2 m
   Roll period: 9.4 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.05
   Seaboat quality  (Average = 1.00): 1.28

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.650 / 0.651
   Length to Beam Ratio: 5.83 : 1
   'Natural speed' for length: 10.72 kts
   Power going to wave formation at top speed: 33 %
   Trim (Max stability = 0, Max steadiness = 100): 55
   Bow angle (Positive = bow angles forward): 0.00 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 %,  4.92 ft / 1.50 m,  4.92 ft / 1.50 m
      - Forward deck:   30.00 %,  4.92 ft / 1.50 m,  4.92 ft / 1.50 m
      - Aft deck:   35.00 %,  4.92 ft / 1.50 m,  4.92 ft / 1.50 m
      - Quarter deck:   15.00 %,  4.92 ft / 1.50 m,  4.92 ft / 1.50 m
      - Average freeboard:      4.92 ft / 1.50 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 28.7 %
      - Above water (accommodation/working, high = better): 77.3 %
   Waterplane Area: 1,732 Square feet or 161 Square metres
   Displacement factor (Displacement / loading): 136 %
   Structure weight / hull surface area: 22 lbs/sq ft or 110 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.97
      - Longitudinal: 1.38
      - Overall: 1.01
   Excellent machinery, storage, compartmentation space
   Cramped accommodation and workspace room
   Ship has slow, easy roll, a good, steady gun platform
   Good seaboat, rides out heavy weather easily

[The Rock Doctor]

Type 1913 River Gunboat

The muzzle-loading 75mm is a howitzer.  Protection against small arms fire.  Some space to stow a few passengers and cargo.

RGB-31 through -38, laid down 1913
RGB-39 through -46, laid down 1914

Enter ship name, Enter country Enter ship type laid down 1913

Displacement:
   127 t light; 132 t standard; 138 t normal; 142 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (118.98 ft / 114.83 ft) x 19.69 ft x (3.28 / 3.37 ft)
   (36.26 m / 35.00 m) x 6.00 m  x (1.00 / 1.03 m)

Armament:
      1 - 2.95" / 75.0 mm 45.0 cal gun - 12.98lbs / 5.89kg shells, 100 per gun
     Muzzle loading gun in deck mount, 1913 Model
     1 x Single mount on centreline, aft deck centre
      1 - 1.97" / 50.0 mm 45.0 cal gun - 3.85lbs / 1.74kg shells, 250 per gun
     Quick firing gun in deck mount, 1913 Model
     1 x Single mount on centreline, forward deck centre
      2 - 0.39" / 10.0 mm 45.0 cal guns - 0.03lbs / 0.01kg shells, 15,000 per gun
     Machine guns in deck mounts, 1913 Model
     2 x Single mounts on sides, forward deck aft
      2 raised mounts
      Weight of broadside 17 lbs / 8 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   0.59" / 15 mm     74.64 ft / 22.75 m   6.56 ft / 2.00 m
   Ends:   0.39" / 10 mm     40.16 ft / 12.24 m   5.31 ft / 1.62 m
     Main Belt covers 100 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.39" / 10 mm   0.39" / 10 mm            -
   2nd:   0.39" / 10 mm   0.39" / 10 mm            -
   3rd:   0.20" / 5 mm         -               -

   - Armoured deck - multiple decks:
   For and Aft decks: 0.39" / 10 mm
   Forecastle: 0.00" / 0 mm  Quarter deck: 0.39" / 10 mm

   - Conning towers: Forward 0.39" / 10 mm, Aft 0.00" / 0 mm

Machinery:
   Coal fired boilers, complex reciprocating steam engines,
   Direct drive, 2 shafts, 134 ihp / 100 Kw = 10.00 kts
   Range 500nm at 10.00 kts
   Bunker at max displacement = 10 tons (100% coal)

Complement:
   19 - 26

Cost:
   £0.007 million / $0.029 million

Distribution of weights at normal displacement:
   Armament: 3 tons, 2.2 %
      - Guns: 3 tons, 2.2 %
   Armour: 33 tons, 24.1 %
      - Belts: 16 tons, 11.6 %
      - Armament: 5 tons, 3.9 %
      - Armour Deck: 12 tons, 8.4 %
      - Conning Tower: 0 tons, 0.2 %
   Machinery: 9 tons, 6.4 %
   Hull, fittings & equipment: 48 tons, 35.1 %
   Fuel, ammunition & stores: 10 tons, 7.5 %
   Miscellaneous weights: 34 tons, 24.7 %
      - On freeboard deck: 34 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     760 lbs / 345 Kg = 59.1 x 3.0 " / 75 mm shells or 1.4 torpedoes
   Stability (Unstable if below 1.00): 1.37
   Metacentric height 0.8 ft / 0.2 m
   Roll period: 9.5 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.07
   Seaboat quality  (Average = 1.00): 1.27

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.650 / 0.653
   Length to Beam Ratio: 5.83 : 1
   'Natural speed' for length: 10.72 kts
   Power going to wave formation at top speed: 42 %
   Trim (Max stability = 0, Max steadiness = 100): 55
   Bow angle (Positive = bow angles forward): 10.00 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 %,  4.92 ft / 1.50 m,  4.92 ft / 1.50 m
      - Forward deck:   30.00 %,  4.92 ft / 1.50 m,  4.92 ft / 1.50 m
      - Aft deck:   35.00 %,  4.92 ft / 1.50 m,  4.92 ft / 1.50 m
      - Quarter deck:   15.00 %,  4.92 ft / 1.50 m,  4.92 ft / 1.50 m
      - Average freeboard:      4.92 ft / 1.50 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 29.3 %
      - Above water (accommodation/working, high = better): 85.4 %
   Waterplane Area: 1,732 Square feet or 161 Square metres
   Displacement factor (Displacement / loading): 147 %
   Structure weight / hull surface area: 23 lbs/sq ft or 111 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.97
      - Longitudinal: 1.47
      - Overall: 1.01
   Excellent machinery, storage, compartmentation space
   Cramped accommodation and workspace room
   Ship has slow, easy roll, a good, steady gun platform
   Good seaboat, rides out heavy weather easily

[The Rock Doctor]

Type 1923 Armored River Gunboat

And an armored river gunboat to replace some of the Type 1895 class.

It's twice the displacement of the Type 1895, but has a far heavier armament, better protection, and better speed/range.

RGB-47 to -48, laid down 1923
RGB-49 to -50, laid down 1924
RGB-51 to -52, laid down 1925

Enter ship name, Enter country Enter ship type laid down 1923

Displacement:
   174 t light; 184 t standard; 189 t normal; 192 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (148.98 ft / 144.36 ft) x 19.69 ft x (3.94 / 3.99 ft)
   (45.41 m / 44.00 m) x 6.00 m  x (1.20 / 1.22 m)

Armament:
      3 - 2.95" / 75.0 mm 45.0 cal guns - 12.98lbs / 5.89kg shells, 250 per gun
     Quick firing guns in deck mounts, 1923 Model
     3 x Single mounts on centreline ends, majority forward
      1 raised mount - superfiring
      1 - 1.97" / 50.0 mm 45.0 cal gun - 3.86lbs / 1.75kg shells, 250 per gun
     Anti-air gun in deck mount, 1923 Model
     1 x Single mount on centreline, aft deck forward
      4 - 0.59" / 15.0 mm 90.0 cal guns - 0.11lbs / 0.05kg shells, 4,000 per gun
     Machine guns in deck mounts, 1923 Model
     4 x Single mounts on sides, forward deck aft
      4 raised mounts
      Weight of broadside 43 lbs / 20 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   1.57" / 40 mm     36.09 ft / 11.00 m   6.23 ft / 1.90 m
   Ends:   0.79" / 20 mm   108.23 ft / 32.99 m   3.94 ft / 1.20 m
     Main Belt covers 38 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   1.57" / 40 mm   0.79" / 20 mm            -
   3rd:   0.98" / 25 mm   0.39" / 10 mm            -
   4th:   0.39" / 10 mm         -               -

   - Box over machinery & magazines:
   0.98" / 25 mm
   Forecastle: 0.00" / 0 mm  Quarter deck: 0.59" / 15 mm

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

Machinery:
   Diesel Internal combustion motors,  plus diesel motors,
   Geared drive, 2 shafts, 335 shp / 250 Kw = 12.52 kts
   Range 600nm at 10.00 kts
   Bunker at max displacement = 7 tons

Complement:
   25 - 33

Cost:
   £0.029 million / $0.117 million

Distribution of weights at normal displacement:
   Armament: 9 tons, 4.6 %
      - Guns: 9 tons, 4.6 %
   Armour: 73 tons, 38.9 %
      - Belts: 32 tons, 17.0 %
      - Armament: 20 tons, 10.4 %
      - Armour Deck: 21 tons, 11.3 %
      - Conning Tower: 0 tons, 0.2 %
   Machinery: 11 tons, 5.9 %
   Hull, fittings & equipment: 69 tons, 36.8 %
   Fuel, ammunition & stores: 15 tons, 7.9 %
   Miscellaneous weights: 11 tons, 5.8 %
      - Hull below water: 4 tons
      - On freeboard deck: 5 tons
      - Above deck: 2 tons

Fittings:
-2 t:  Fire control, such as it is, and a searchlight (AD)
-5 t:  Weight reserve or deck space (FD)
-4 t:  Diesel engines (BW)

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     675 lbs / 306 Kg = 52.4 x 3.0 " / 75 mm shells or 1.1 torpedoes
   Stability (Unstable if below 1.00): 1.19
   Metacentric height 0.6 ft / 0.2 m
   Roll period: 10.7 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.22
   Seaboat quality  (Average = 1.00): 1.05

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.590 / 0.592
   Length to Beam Ratio: 7.33 : 1
   'Natural speed' for length: 12.01 kts
   Power going to wave formation at top speed: 45 %
   Trim (Max stability = 0, Max steadiness = 100): 67
   Bow angle (Positive = bow angles forward): 20.00 degrees
   Stern overhang: 1.64 ft / 0.50 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   25.00 %,  8.20 ft / 2.50 m,  6.23 ft / 1.90 m
      - Forward deck:   25.00 %,  6.23 ft / 1.90 m,  4.27 ft / 1.30 m
      - Aft deck:   35.00 %,  4.27 ft / 1.30 m,  4.27 ft / 1.30 m
      - Quarter deck:   15.00 %,  4.27 ft / 1.30 m,  4.27 ft / 1.30 m
      - Average freeboard:      5.20 ft / 1.59 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 37.4 %
      - Above water (accommodation/working, high = better): 73.3 %
   Waterplane Area: 2,059 Square feet or 191 Square metres
   Displacement factor (Displacement / loading): 146 %
   Structure weight / hull surface area: 27 lbs/sq ft or 133 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 1.00
      - Longitudinal: 1.09
      - Overall: 1.00
   Excellent machinery, storage, compartmentation space
   Cramped accommodation and workspace room
   Ship has slow, easy roll, a good, steady gun platform

[The Rock Doctor]

RGB-61 Class River Gunboat

A shallow-draft gunboat designed explicitly to carry a platoon's worth of 150mm howitzers for shore bombardment purposes *and* the spotting top to direct the fire.

The vessel would be able to work inshore on oceans, in the big lake in the canal zone, and a fair ways up some of the major river systems in Union territory. 

Although shown with the howitzers stowed forward/aft, actual fire missions would normally occur with the guns firing on a broadside; little to no end-on fire is anticipated here.  Fixed ammunition lockers supply a quantity of ready shells to the battery, the rest being below decks.

The ship is armored and armed for basic defense against air and shore battery attack.  While an earlier version embarked torpedo nets, I'm not really sure it's a major hazard for something with such a shallow draft, especially if it works on rivers a fair bit.

Consideration was given to a layout that had the superstructure well aft and all four howitzers in line amidships, but that seemed a bit vulnerable to mission kills from a single hit or malfunction.  Plus the spotting top seems better placed amidships.

RGB-61, laid down 1926
RGB-66, laid down 1927
RGB-67, laid down 1927
RGB-76, laid down 1928

Enter ship name, Enter country Enter ship type laid down 1925

Displacement:
   898 t light; 974 t standard; 1,017 t normal; 1,051 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (255.81 ft / 249.34 ft) x 39.37 ft x (5.58 / 5.74 ft)
   (77.97 m / 76.00 m) x 12.00 m  x (1.70 / 1.75 m)

Armament:
      1 - 1.97" / 50.0 mm 45.0 cal gun - 3.85lbs / 1.75kg shells, 250 per gun
     Quick firing gun in deck mount, 1925 Model
     1 x Single mount on centreline, forward deck forward
      1 raised mount
      2 - 1.97" / 50.0 mm 45.0 cal guns - 3.85lbs / 1.75kg shells, 250 per gun
     Anti-air guns in deck mounts, 1925 Model
     2 x Single mounts on sides, aft deck forward
      8 - 0.59" / 15.0 mm 90.0 cal guns - 0.12lbs / 0.05kg shells, 4,000 per gun
     Machine guns in deck mounts, 1925 Model
     4 x Twin mounts on sides, evenly spread
      4 raised mounts
      4 - 5.91" / 150 mm 25.0 cal guns - 93.53lbs / 42.42kg shells, 250 per gun
     Breech loading guns in deck mounts, 1925 Model
     4 x Single mounts on centreline ends, evenly spread
      Weight of broadside 387 lbs / 175 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   0.98" / 25 mm   162.40 ft / 49.50 m   11.81 ft / 3.60 m
   Ends:   Unarmoured
     Main Belt covers 100 % of normal length

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

   - Armoured deck - single deck: 0.98" / 25 mm For and Aft decks
   Forecastle: 0.98" / 25 mm  Quarter deck: 0.98" / 25 mm

   - Conning towers: Forward 0.98" / 25 mm,  Aft 0.00" / 0 mm

Machinery:
   Diesel Internal combustion generators,
   Electric motors, 2 shafts, 2,010 shp / 1,500 Kw = 15.57 kts
   Range 2,500nm at 10.00 kts
   Bunker at max displacement = 76 tons

Complement:
   89 - 117

Cost:
   £0.168 million / $0.673 million

Distribution of weights at normal displacement:
   Armament: 34 tons, 3.4 %
   Armour: 255 tons, 25.1 %
      - Belts: 83 tons, 8.2 %
      - Armament: 32 tons, 3.2 %
      - Armour Deck: 138 tons, 13.6 %
      - Conning Tower: 2 tons, 0.2 %
   Machinery: 65 tons, 6.4 %
   Hull, fittings & equipment: 329 tons, 32.4 %
   Fuel, ammunition & stores: 119 tons, 11.7 %
   Miscellaneous weights: 214 tons, 21.0 %
      - Hull below water: 36 tons
      - On freeboard deck: 58 tons
      - Above deck: 120 tons

Fittings:
-36 t:  Diesel/electric drive (BW)
-4 t:  Type 1918 fire control (AD)
-25 t:  L/R wireless (AD)
-10 t:  Extra S/R wireless (AD)
-10 t:  Night-fighting doodads (AD)
-25 t:  Command facilities (AD)
-25 t:  Cage mast and spotting top (AD)
-79 t:  Weight reserve (mostly FD)

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     3,346 lbs / 1,518 Kg = 877.3 x 2.0 " / 50 mm shells or 2.0 torpedoes
   Stability (Unstable if below 1.00): 1.30
   Metacentric height 2.0 ft / 0.6 m
   Roll period: 11.7 seconds
   Steadiness   - As gun platform (Average = 50 %): 100 %
         - Recoil effect (Restricted arc if above 1.00): 0.25
   Seaboat quality  (Average = 1.00): 1.58

Hull form characteristics:
   Hull has raised forecastle,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.650 / 0.653
   Length to Beam Ratio: 6.33 : 1
   'Natural speed' for length: 15.79 kts
   Power going to wave formation at top speed: 44 %
   Trim (Max stability = 0, Max steadiness = 100): 64
   Bow angle (Positive = bow angles forward): 10.00 degrees
   Stern overhang: 3.28 ft / 1.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   15.00 %,  18.04 ft / 5.50 m,  18.04 ft / 5.50 m
      - Forward deck:   45.00 %,  10.17 ft / 3.10 m,  10.17 ft / 3.10 m
      - Aft deck:   25.00 %,  10.17 ft / 3.10 m,  10.17 ft / 3.10 m
      - Quarter deck:   15.00 %,  10.17 ft / 3.10 m,  10.17 ft / 3.10 m
      - Average freeboard:      11.35 ft / 3.46 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 40.9 %
      - Above water (accommodation/working, high = better): 163.7 %
   Waterplane Area: 7,520 Square feet or 699 Square metres
   Displacement factor (Displacement / loading): 145 %
   Structure weight / hull surface area: 36 lbs/sq ft or 175 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.70
      - Longitudinal: 1.33
      - Overall: 0.75
   Caution: Hull subject to strain in open-sea
   Hull space for machinery, storage, compartmentation is excellent
   Room for accommodation and workspaces is excellent
   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 1926 Armored River Gunboat

A "baseline" armored river gunboat that will replace similar sized hulls from the 1890s.

I contemplated a shorter 15mm belt combined with a 20mm box as protection, but opted to go with the more conventional 20mm belt and full deck.  The notion is more about protecting the waterline and the important bits from splinters and small arms fire than from direct shell hits.

Also contemplated trying to shove a 50mm AA mounting in but that isn't practical if I want to keep the size down.  The two twin HMG mountings will have to do that job.

RGB-53 to -60, laid down 1926
RGB-62 to -71, laid down 1927
RGB-72 to -80, laid down 1928
RGB-81 to -88, laid down 1929
RGB-89 to -96, laid down 1930
RGB-97 to -100, laid down 1931

Enter ship name, Enter country Enter ship type laid down 1926

Displacement:
   80 t light; 87 t standard; 88 t normal; 89 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (101.96 ft / 98.43 ft) x 16.40 ft x (3.61 / 3.65 ft)
   (31.08 m / 30.00 m) x 5.00 m  x (1.10 / 1.11 m)

Armament:
      1 - 2.95" / 75.0 mm 40.0 cal gun - 12.34lbs / 5.60kg shells, 250 per gun
     Breech loading gun in deck mount, 1926 Model
     1 x Single mount on centreline, aft deck centre
      1 - 2.95" / 75.0 mm 45.0 cal gun - 12.98lbs / 5.89kg shells, 250 per gun
     Quick firing gun in deck mount, 1926 Model
     1 x Single mount on centreline, forward deck centre
      4 - 0.59" / 15.0 mm 90.0 cal guns - 0.12lbs / 0.05kg shells, 4,000 per gun
     Anti-air guns in deck mounts, 1926 Model
     2 x Twin mounts on sides, aft deck forward
      2 raised mounts
      Weight of broadside 26 lbs / 12 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   0.79" / 20 mm     62.34 ft / 19.00 m   4.92 ft / 1.50 m
   Ends:   Unarmoured
     Main Belt covers 97 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.98" / 25 mm   0.59" / 15 mm            -
   2nd:   0.98" / 25 mm   0.59" / 15 mm            -
   4th:   0.59" / 15 mm         -               -

   - Armoured deck - single deck: 0.79" / 20 mm For and Aft decks
   Forecastle: 0.59" / 15 mm  Quarter deck: 0.59" / 15 mm

   - Conning towers: Forward 0.79" / 20 mm,  Aft 0.00" / 0 mm

Machinery:
   Diesel Internal combustion motors,
   Geared drive, 2 shafts, 301 shp / 225 Kw = 13.27 kts
   Range 300nm at 10.00 kts
   Bunker at max displacement = 3 tons

Complement:
   13 - 18

Cost:
   £0.019 million / $0.077 million

Distribution of weights at normal displacement:
   Armament: 5 tons, 5.3 %
   Armour: 36 tons, 40.3 %
      - Belts: 11 tons, 12.1 %
      - Armament: 9 tons, 10.2 %
      - Armour Deck: 16 tons, 17.7 %
      - Conning Tower: 0 tons, 0.4 %
   Machinery: 10 tons, 10.9 %
   Hull, fittings & equipment: 24 tons, 27.7 %
   Fuel, ammunition & stores: 8 tons, 8.9 %
   Miscellaneous weights: 6 tons, 6.8 %
      - Hull below water: 3 tons
      - On freeboard deck: 1 tons
      - Above deck: 2 tons

Fittings:
-3t:  Diesel engines (BW)
-1 t:  Weight reserve/deck cargo (FD)
-1 t:  FC, such as it is (AD)
-1 t:  Searchlight (AD)

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     177 lbs / 80 Kg = 13.7 x 3.0 " / 75 mm shells or 0.4 torpedoes
   Stability (Unstable if below 1.00): 1.23
   Metacentric height 0.5 ft / 0.1 m
   Roll period: 9.9 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.25
   Seaboat quality  (Average = 1.00): 1.00

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.530 / 0.532
   Length to Beam Ratio: 6.00 : 1
   'Natural speed' for length: 9.92 kts
   Power going to wave formation at top speed: 60 %
   Trim (Max stability = 0, Max steadiness = 100): 70
   Bow angle (Positive = bow angles forward): 10.00 degrees
   Stern overhang: 1.97 ft / 0.60 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   15.00 %,  8.86 ft / 2.70 m,  6.89 ft / 2.10 m
      - Forward deck:   15.00 %,  6.89 ft / 2.10 m,  4.92 ft / 1.50 m
      - Aft deck:   55.00 %,  4.92 ft / 1.50 m,  4.92 ft / 1.50 m
      - Quarter deck:   15.00 %,  4.92 ft / 1.50 m,  4.92 ft / 1.50 m
      - Average freeboard:      5.48 ft / 1.67 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 59.0 %
      - Above water (accommodation/working, high = better): 83.2 %
   Waterplane Area: 1,106 Square feet or 103 Square metres
   Displacement factor (Displacement / loading): 119 %
   Structure weight / hull surface area: 17 lbs/sq ft or 82 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.67
      - Longitudinal: 2.12
      - Overall: 0.75
   Caution: Hull subject to strain in open-sea
   Hull space for machinery, storage, compartmentation is excellent
   Room for accommodation and workspaces is cramped
   Ship has slow, easy roll, a good, steady gun platform