WesWorld

First try so far. Is she all right?

S.20, Italian Submarine laid down 1918

Displacement:
440 t light; 450 t standard; 502 t normal; 542 t full load
Loading submergence 62 tons/feet

Dimensions:
164.04 ft x 19.69 ft x 9.84 ft (normal load)
50.00 m x 6.00 m x 3.00 m
6 - 17.7" / 450 mm submerged torpedo tubes

Machinery:
Diesel Internal combustion engines plus batteries,
Electric cruising motors plus geared drives, 1 shaft, 1,000 shp / 746 Kw = 14.61 kts
Range 5,000nm at 10.00 kts

Complement:
26 - 34

Cost:
£0.041 million / $0.164 million

Distribution of weights at normal displacement:
Armament: 0 tons, 0.0 %
Machinery: 36 tons, 7.2 %
Hull, fittings & equipment: 274 tons, 54.6 %
Fuel, ammunition & stores: 62 tons, 12.3 %
Miscellaneous weights: 130 tons, 25.9 %

Metacentric height 0.5

Remarks:
Hull space for machinery, storage & compartmentation is cramped
Room for accommodation & workspaces is extremely poor


Estimated overall survivability and seakeeping ability:
Relative margin of stability: 1.08
Shellfire needed to sink: 111 lbs / 51 Kg = 1.0 x 6 " / 152 mm shells
(Approx weight of penetrating shell hits needed to sink ship excluding critical hits)
Torpedoes needed to sink: 0.1
(Approx number of typical torpedo hits needed to sink ship)
Relative steadiness as gun platform: 1 %
(Average = 50 %)
Relative rocking effect from firing to beam: 0.00
Relative quality as seaboat: 0.00

Hull form characteristics:
Block coefficient: 0.553
Sharpness coefficient: 0.37
Hull speed coefficient 'M': 6.31
'Natural speed' for length: 12.81 kts
Power going to wave formation at top speed: 51 %
Trim: 50
(Maximise stabilty/flotation = 0, Maximise steadiness/seakeeping = 100)

Estimated hull characteristics & strength:
Underwater volume absorbed by magazines and engineering spaces: 154.0 %
Relative accommodation and working space: 0.8 %
(Average = 100%)
Displacement factor: 248 %
(Displacement relative to loading factors)
Relative cross-sectional hull strength: 3.84
(Structure weight / hull surface area: 91 lbs / square foot or 446 Kg / square metre)
Relative longitudinal hull strength: 1.71
(for 0.10 ft / 0.03 m average freeboard, freeboard adjustment -8.23 ft)
Relative composite hull strength: 2.09

Operational diving depth; 62.7m

If memory serves, standard practice against merchantships was to surface and use the gun rather than waste a torpedo.
Any reason why no gun?

Ah, shes based on the British R class hunter-killer submarines. She isn't made for prolonged anti-shipping operations but high speed. 14.6knts submerged. A 450mm torpedo will take down a merchie anyway.

Right, sort of an underwater PT Boat!!

One of the roles for the R class submarines was to attempt to hunt down U-boats using their quick speed, great manuverability and diving/surfacing speed.