WesWorld

I opted to rebuild a small river flotilla using this design

Project 39RM, Yugoslav Riverine Monitor laid down 1939

Displacement: 256 t light; 268 t standard; 275 t normal; 281 t full load

Dimensions: Length overall / water x beam x draught
157.29 ft / 155.84 ft x 21.33 ft x 4.92 ft (normal load)
47.94 m / 47.50 m x 6.50 m x 1.50 m

Armament:
2 - 3.46" / 88.0 mm guns in single mounts, 20.79lbs / 9.43kg shells, 1936 Model Dual purpose guns in deck mounts on centreline ends, evenly spread
2 - 1.57" / 40.0 mm guns (1x2 guns), 1.95lbs / 0.88kg shells, 1939 Model Anti-aircraft guns in deck mount on side amidships, all raised guns
4 - 0.79" / 20.0 mm guns (1x4 guns), 0.24lbs / 0.11kg shells, 1939 Model Anti-aircraft guns in deck mount on centreline aft
2 - 0.79" / 20.0 mm guns (1x2 guns), 0.24lbs / 0.11kg shells, 1928 Model Anti-aircraft guns in deck mount
on centreline amidships, all raised guns - superfiring
Weight of broadside 47 lbs / 21 kg
Shells per gun, main battery: 225

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 0.79" / 20 mm 78.74 ft / 24.00 m 5.58 ft / 1.70 m
Ends: Unarmoured
Main Belt covers 78 % of normal length

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.79" / 20 mm 0.39" / 10 mm -
2nd: 0.39" / 10 mm 0.39" / 10 mm -
3rd: 0.39" / 10 mm - -
4th: 0.39" / 10 mm - -

Machinery:

Diesel Internal combustion motors,
Geared drive, 3 shafts, 309 shp / 231 Kw = 12.00 kts
Range 2,000nm at 8.00 kts
Bunker at max displacement = 13 tons

Complement: 33 - 43

Cost: £0.088 million / $0.350 million

Distribution of weights at normal displacement:

Armament: 6 tons, 2.1 %
Armour: 19 tons, 7.0 %
- Belts: 16 tons, 5.7 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 4 tons, 1.3 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.0 %
Machinery: 8 tons, 3.0 %
Hull, fittings & equipment: 122 tons, 44.5 %
Fuel, ammunition & stores: 19 tons, 7.0 %
Miscellaneous weights: 100 tons, 36.3 %

Overall survivability and seakeeping ability:

Survivability (Non-critical penetrating hits needed to sink ship): 673 lbs / 305 Kg = 32.4 x 3.5 " / 88 mm shells or 0.6 torpedoes
Stability (Unstable if below 1.00): 1.11
Metacentric height 0.6 ft / 0.2 m
Roll period: 11.6 seconds
Steadiness - As gun platform (Average = 50 %): 60 %
- Recoil effect (Restricted arc if above 1.00): 0.19
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:

Hull has a flush deck and transom stern
Block coefficient: 0.589
Length to Beam Ratio: 7.31 : 1
'Natural speed' for length: 14.47 kts
Power going to wave formation at top speed: 42 %
Trim (Max stability = 0, Max steadiness = 100): 30
Bow angle (Positive = bow angles forward): 10.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 8.20 ft / 2.50 m
- Forecastle (20 %): 8.20 ft / 2.50 m
- Mid (50 %): 8.20 ft / 2.50 m
- Quarterdeck (15 %): 8.20 ft / 2.50 m
- Stern: 8.20 ft / 2.50 m
- Average freeboard: 8.20 ft / 2.50 m
Ship tends to be wet forward

Ship space, strength and comments:

Space - Hull below water (magazines/engines, low = better): 67.5 %
- Above water (accommodation/working, high = better): 118.7 %
Waterplane Area: 2,507 Square feet or 233 Square metres
Displacement factor (Displacement / loading): 150 %
Structure weight / hull surface area: 31 lbs/sq ft or 153 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 1.02
- Longitudinal: 3.21
- Overall: 1.14
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is adequate
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

Miscellaneous Weight - 100 tons reserved for organic troop contingent