I am trying something different - taking a drawing and trying to build a Springsharp to match it. I invite your comments to point out my errors.
The concept drawing
My current working Springsharp
Project 39R - Rev A, TBD Riverine Monitor laid down 1939
Displacement:
234 t light; 243 t standard; 250 t normal; 256 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: 150
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, 286 shp / 213 Kw = 12.00 kts
Range 2,000nm at 8.00 kts
Bunker at max displacement = 12 tons
Complement:
30 - 40
Cost:
£0.083 million / $0.330 million
Distribution of weights at normal displacement:
Armament: 6 tons, 2.3 %
Armour: 19 tons, 7.7 %
- Belts: 16 tons, 6.3 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 4 tons, 1.4 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.0 %
Machinery: 8 tons, 3.1 %
Hull, fittings & equipment: 101 tons, 40.4 %
Fuel, ammunition & stores: 16 tons, 6.5 %
Miscellaneous weights: 100 tons, 40.0 %
Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
546 lbs / 248 Kg = 26.3 x 3.5 " / 88 mm shells or 0.6 torpedoes
Stability (Unstable if below 1.00): 1.01
Metacentric height 0.5 ft / 0.2 m
Roll period: 12.7 seconds
Steadiness - As gun platform (Average = 50 %): 90 %
- Recoil effect (Restricted arc if above 1.00): 0.28
Seaboat quality (Average = 1.00): 2.00
Hull form characteristics:
Hull has a flush deck
and transom stern
Block coefficient: 0.535
Length to Beam Ratio: 7.31 : 1
'Natural speed' for length: 14.56 kts
Power going to wave formation at top speed: 41 %
Trim (Max stability = 0, Max steadiness = 100): 45
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): 72.3 %
- Above water (accommodation/working, high = better): 124.0 %
Waterplane Area: 2,380 Square feet or 221 Square metres
Displacement factor (Displacement / loading): 138 %
Structure weight / hull surface area: 27 lbs/sq ft or 131 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.86
- Longitudinal: 2.92
- Overall: 0.98
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
Miscellaneous Weight - 100 tons reserved for organic troop contingent
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You may fire when ready Gridley!