WesWorld

Filipino Trucha-class Submarine Cruiser, laid down 1932

Length, 247 ft x Beam, 30.0 ft x Depth, 19.7 ft
2002 tons normal displacement (1515 tons standard)

Main battery: 4 x 4.53-inch / 115mm (2 x 2)
AA battery: 1 x 1.38-inch / 35mm

Weight of broadside: 187 lbs

8 TT, 21.0" (submerged)

Operational diving depth: 241 feet
Emergency diving depth: 385 feet
Crush depth: 602 feet

Battery armor:
Main, 50mm
AA, 20mm shields

Maximum speed for 3750 shp = 17.10 knots
Approximate cruising radius, 9000 nm / 15 kts

Typical complement: 150-195


Estimated cost, $1.568 million (£392,000)


Distribution of weights:
Percent
normal
displacement:

Armament ......................... 23 tons = 1 pct
Armor, total ..................... 27 tons = 1 pct

Armament 27 tons = 1 pct

Machinery ........................ 111 tons = 6 pct
Hull and fittings; equipment ..... 899 tons = 45 pct
Fuel, ammunition, stores ......... 542 tons = 27 pct
Miscellaneous weights ............ 400 tons = 20 pct
-----
2002 tons = 100 pct

Estimated metacentric height, 0.8 ft

Displacement summary:

Light ship: 1460 tons
Standard displacement: 1515 tons
Normal service: 2002 tons
Full load: 2383 tons

Loading submergence 129 tons/foot

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Estimated overall survivability and seakeeping ability:

Relative margin of stability: 1.00

Shellfire needed to sink: 1088 lbs = 23.4 x 4.5-inch shells
(Approximates weight of penetrating
shell hits needed to sink ship,
not counting critical hits)

Torpedoes needed to sink: 0.3
(Approximates number of 'typical'
torpedo hits needed to sink ship)

Relative steadiness as gun platform, 1 percent
(50 percent is 'average')

Relative rocking effect from firing to beam, 0.00

Relative quality as a seaboat: 0.00

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Hull form characteristics:

Block coefficient: 0.48
Sharpness coefficient: 0.35
Hull speed coefficient 'M' = 5.99
'Natural speed' for length = 15.7 knots
Power going to wave formation
at top speed: 47 percent


Estimated hull characteristics and strength:

Relative underwater volume absorbed by
magazines and engineering spaces: 93 percent

Relative accommodation and working space: 1 percent


Displacement factor: 234 percent
(Displacement relative to loading factors)


Relative cross-sectional hull strength: 2.60
(Structure weight per square
foot of hull surface: 123 lbs)

Relative longitudinal hull strength: 2.34
(for 0.1 ft average freeboard;
freeboard adjustment -10.9 ft)

Relative composite hull strength: 2.41

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(Yes, there's Yet Another Filipino Gun Calibre. But before you induce the Revolt of the Quartermasters, stay tuned for the rest of the story...when it appears. ;-) )

But why?

Submarine cruiser X1 was made for 1 reason only; to be able to engage a destroyer at 5000yds. It didn't work too well but the 5.2"/42 QF would have been an excellent weapon. Far better than the 5.25/4.5/4.7 weapons.

The 4.5"/115mm calibre will be adopted by the Philippines for two reasons: experience will show that the 130mm shell is too heavy for practical use by Filipino sailors; the "reduced" calibre selected will be 115mm because 75(mm)+155(mm)/2 = 115(mm). ;-)

(I have always wondered why the British never picked a calibre and stuck to it, BTW...)

As for why a cruiser sub, three reasons. One, as an experiment; two, for rapid dispatching of large merchies; and three, for nighttime bombardment of enemy-held islands.

Quoted

The 4.5"/115mm calibre will be adopted by the Philippines for two reasons: experience will show that the 130mm shell is too heavy for practical use by Filipino sailors; the "reduced" calibre selected will be 115mm because 75(mm)+155(mm)/2 = 115(mm). ;-)

Italy took the easy option. Just have lighter shells of c. 28kg which are manageable.

Quoted

As for why a cruiser sub, three reasons. One, as an experiment; two, for rapid dispatching of large merchies; and three, for nighttime bombardment of enemy-held islands.

Experimental how many times you can roll the sub after one of the turrets flood whilst submerging.

Why not use the 110mm from Nordmark? It already exists.

Quoted

Why not use the 110mm from Nordmark? It already exists

National Pride?

115mm mounts will replace both the 130mm and (half/half with 75mm) the 100mm...with 22kg shells.

'If I could start all over...' I'd probably go for 145mm or so instead of 155mm, this was actually suggested in a thread over on Bob Hennemann's battlecruiser board (unfortunatly lost in the Hack Attack), from which I learned about the 'shell size vs sailor size' problem for Filipino crews...which I will use in part to explain the shift to the smaller calibre.

(Which also allows me to comfortably put six guns instead of a very-cramped five on DD31...)

Yes, that will do wonders for hull integrity...