WesWorld

Further fallout from the Otta strike...

The ex-Italian Indomito-class destroyers will all receive a refit in 1925. With the Indian carrier strike (and the no AA = crippling hit conclusion), it has been decided to take one of the 3" mounts and replace it with a 57mm DP.


The third mount from the bow is the one to be replaced.

Indomito-class, ex-Italian Destroyers, laid down 1912

Length, 260 ft x Beam, 26.0 ft x Depth, 10.8 ft
834 tons normal displacement (762 tons standard)

Main battery: 3 x 3.00-inch / 76.2mm
Secondary battery: 1 x 2.24-inch / 57mm
Light battery: 2 x 0.54-inch / 13.7mm

Weight of broadside: 46 lbs

3 TT, 18.0" (1 submerged)

Depth charges @ 550lb each: 30

Hull unarmored

Maximum speed for 25807 shp = 32.00 knots
Approximate cruising radius, 4000 nm / 10 kts

Typical complement: 78-101


Estimated cost, $391,000 (£98,000)

Remarks:

Caution: Hull structure is subject to strain in open-sea
conditions.

Oil firing.

Poor seaboat, wet and uncomfortable; reduced performance
in heavy weather.

Magazines and engineering spaces are cramped, with poor
watertight subdivision.

Cramped ship; poor crew accommodation, limited working space.


Distribution of weights:
Percent
normal
displacement:

Armament ......................... 7 tons = 1 pct
Machinery ........................ 473 tons = 57 pct
Hull and fittings; equipment ..... 251 tons = 30 pct
Fuel, ammunition, stores ......... 93 tons = 11 pct
Miscellaneous weights ............ 10 tons = 1 pct
-----
834 tons = 100 pct

Estimated metacentric height, 1.1 ft

Displacement summary:

Light ship: 741 tons
Standard displacement: 762 tons
Normal service: 834 tons
Full load: 889 tons

Loading submergence 105 tons/foot

+++++++++++++++++++++++++


Estimated overall survivability and seakeeping ability:

Relative margin of stability: 1.33

Shellfire needed to sink: 197 lbs = 14.6 x 3.0-inch shells
(Approximates weight of penetrating
shell hits needed to sink ship,
not counting critical hits)

Torpedoes needed to sink: 0.2
(Approximates number of 'typical'
torpedo hits needed to sink ship)

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

Relative rocking effect from firing to beam, 0.09

Relative quality as a seaboat: 0.79

+++++++++++++++++++++++++


Hull form characteristics:

Block coefficient: 0.40
Sharpness coefficient: 0.30
Hull speed coefficient 'M' = 8.44
'Natural speed' for length = 16.1 knots
Power going to wave formation
at top speed: 71 percent


Estimated hull characteristics and strength:

Relative underwater volume absorbed by
magazines and engineering spaces: 200 percent

Relative accommodation and working space: 89 percent


Displacement factor: 39 percent
(Displacement relative to loading factors)


Relative cross-sectional hull strength: 0.59
(Structure weight per square
foot of hull surface: 33 lbs)

Relative longitudinal hull strength: 1.87
(for 11.68 ft average freeboard;
freeboard adjustment +2.48 ft)

Relative composite hull strength: 0.66

+++++++++++++++++++++++++

I don't get that? why not just develop the 76 mm into a DP?

Developing a 76mm DP surely is the next step. Nevertheless, if there´s no such weapon at hand right now it seems reasonable to use what is - even if that´s a light weight (relatively speaking) 57mm gun. The lesson´s learned from the Andaman Sea battles have to be worked into the fleet asap.

Exactly. Also, modifying a 76mm mount for DP would add weight (well, SS wouldn't, but in RL it would) and that's one thing these ships do NOT need...

In 1935 they'll all be rebuilt; the underwater torpedo tube will be removed, and the armament changed to (probably) 2 x 76mm and 4 x 57mm. A little on the light side, perhaps, but the Fleet Plan calls for them to be simply seaplane-tender-escorts by that time...