WesWorld

The Bhubaneshwar class destroyers have been on the planning table for a couple of years, but kept getting bumped due to other concerns.

The class was added to the books for 1930-31, and incorporated changes already deemed necessary from operational experience. This included the deletion of the torpedo well forward of the bridge, as still seen in the Bassein class, with two quadruple carriages sited amidships. The torpedo armament was to be further doubled with the carrying of a full set of reload weapons. There was also to be an increase in light AA and searchlights, but the main gun armament was to remain at one gun forward and three aft.

This arrangement was finally discredited, after several years of inconclusive internal controversy, by the Filipino Revolution. It was found that a single forward gun was an inadequate armament when destroyers were either attacking or intercepting one; the volume of fire was simply ineffective. Rather than delay the class by re-designing it with a super-firing "Bruno" mount, the gun in "Anton" position was re-designated as a twin mount with much less fuss. The additional top-weight, however, meant that the torpedo reloads had to go.

Two units are planned for 1930, with two more for 1931. It is expected that the follow-up Miraj class of 1932 will be incremental improvements on this class.

Note: L:B ratio is 10.67:1, and the BC as entered is .395, not .40.



Bhubaneshwar, laid down 1930

Length, 112.0 m x Beam, 10.5 m x Depth, 3.8 m
1780 tonnes normal displacement (1582 tonnes standard)

Main battery: 5 x 12.5-cm (1x2, 3x1 DM)
Secondary battery: 6 x 3.5-cm (3x2)
AA battery: 4 x 1.5-cm (1x4)

Weight of broadside: 139 kg

8 TT, 55.0 cm (2x4)

20 t set aside for depth charges + 5 t weight reserve

Hull unarmored

Battery armor:
Main, 3.0 cm shields / secondary, 2.0 cm shields
AA, 2.0 cm shields

Maximum speed for 32502 shaft kw = 34.02 knots
Approximate cruising radius, 7000 nm / 12 knots

Typical complement: 137-178


Estimated cost, $3.644 million (£911,000)

Remarks:

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

Ship has slow, easy roll; a good, steady gun platform.

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


Distribution of weights:
Percent
normal
displacement:

Armament ......................... 38 tonnes = 2 pct
Armor, total ..................... 11 tonnes = 1 pct

Armament 11 tonnes = 1 pct

Machinery ........................ 946 tonnes = 53 pct
Hull and fittings; equipment ..... 499 tonnes = 28 pct
Fuel, ammunition, stores ......... 259 tonnes = 15 pct
Miscellaneous weights ............ 25 tonnes = 1 pct
-----
1780 tonnes = 100 pct

Estimated metacentric height, 0.5 m

Displacement summary:

Light ship: 1520 tonnes
Standard displacement: 1582 tonnes
Normal service: 1780 tonnes
Full load: 1931 tonnes

Loading submergence 636 tonnes/metre

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


Estimated overall survivability and seakeeping ability:

Relative margin of stability: 1.27

Shellfire needed to sink: 182 kg = 6.7 x 12.5-cm 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, 70 percent
(50 percent is 'average')

Relative rocking effect from firing to beam, 0.26

Relative quality as a seaboat: 1.00

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


Hull form characteristics:

Block coefficient: 0.40
Sharpness coefficient: 0.29
Hull speed coefficient 'M' = 9.27
'Natural speed' for length = 19.2 knots
Power going to wave formation
at top speed: 66 percent


Estimated hull characteristics and strength:

Relative underwater volume absorbed by
magazines and engineering spaces: 189 percent

Relative accommodation and working space: 98 percent


Displacement factor: 60 percent
(Displacement relative to loading factors)


Relative cross-sectional hull strength: 0.51
(Structure weight per square
metre of hull surface: 182 kg)

Relative longitudinal hull strength: 1.18
(for 4.40 m average freeboard;
freeboard adjustment +1.13 m)

Relative composite hull strength: 0.56

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


[Machine-readable parameters: Spring Style v. 1.2.1]

367.36 x 34.44 x 12.46; 14.43 -- Dimensions
0.40 -- Block coefficient
1930 -- Year laid down
34.02 / 7000 / 12.00; Oil-fired turbine or equivalent -- Speed / radius / cruise
25 tons -- Miscellaneous weights
++++++++++
5 x 4.92; 0 -- Main battery; turrets
Central positioning of guns
Gun-shields
:
6 x 1.38; 0 -- Secondary battery; turrets
Gun-shields
:
4 x 0.59 -- Tertiary (QF/AA) battery
Gun-shields
:
0 -- No fourth (light) battery
8 / 0 / 21.65 -- TT / submerged / size
++++++++++
0.00 -- No belt armor
0.00 / 0.00 -- Deck / CT
1.18 / 0.79 / 0.79 / 0.00 -- Battery armor


(Note: For portability, values are stored in Anglo-American units)


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

The deletion of the torpedo well is an excellent move. It should significantly improve seakeeping.

Now I can't see any reload torpedoes. If you want to actually reload quickly, as in, less than an few hours, then you need a reload system like the Japanese which takes up over twice as much deckspace. And because you have have 16 torpedoes lying on the deck of a small ship, the chance of 1 of them being hit is extremely large - especially if your enemy employs a few "tricks".

Now reload torpedoes stored below decks. You need a small derrick to move the torpedoes around. The 550mm torpedoes weigh about 2tons each, which gives you 16tons by itself. I'm absolutely sure that SS doesn't give you the first set of torpedoes in the tubes, so you need 16tons of misc. weight at least, just for the 8 torpedoes in the quadruple mounts on deck.

Depth charges; how do you plan to aim them? Hydrophones? They don't weigh that much, maybe 1-2tons but are fairly inaccurate. They give an idea as to general bearing but not as to range.

A few comments on the drawing;

On the plan view, the 35mm duple forward of the bridge is shown as a 15mm quad instead of 35mm.

I'd cut down the deck just after the bridge so that the torpedo tubes are on the same level. Also doing that you can decrease the height of the second funnel which gives a smaller silhouette.

What does DM, with regard to the 125mm guns stand for?

Quoted

Originally posted by Red Admiral
Now I can't see any reload torpedoes.

That would be because there are exactly none:

Quoted

The additional top-weight, however, meant that the torpedo reloads had to go.

RLBH

It probably would have been better to read all of the information before writing things down.

I´m with RA regarding the height of the forward tubes and the second funnel with its platforms. If stability is an issue, see comment on top weight, this really should be done. Giving her a smaller silhouette this way is another bonus that should be welcome.

Otherwise a decent and nice design.

DM was just to be clear that these are deck mounts with hoists, not turrets.

I'll consider the deck height matter, but might leave it be for the first two units of the class, anyway. The Navy probably just wants them built and is to impatient further changes to be made. There's time to revise the specs for the 1931 units, so perhaps those will only be half-sisters.

The forward 35 mm gun is a bit distorted in the drawing, I'll look into that.

On hydrophones: I assume I'd be using whatever's commonly in play. Is everybody setting aside miscellaneous weight for hydrophone weight or what?

Thanks for the comments.

Quoted

On hydrophones: I assume I'd be using whatever's commonly in play. Is everybody setting aside miscellaneous weight for hydrophone weight or what?

Well I'm sure that everyone is using active sonar that can fry a whale at 100mile range.

According to Whitley, the weight of asdic sets fitted to RN destroyers was 9tons. Now your fairly standard depth charge weighs 0.2tons or so. Standard number carried was about 30-40. Thats about another 6-8tons. The weight of the individual racks and depth charge throwers on either beam is a few tons. Hey presto, arrived at your 20tons of misc. weight. Each depth charge dropped has about a 1% chance of sinking the sub, so with the standard pattern, a chance of about 4%. At the moment you have a single rack(or twin) of charges on the stern.

"Because you didn't really know where the sub was, depth charges were dropped in patterns. The patterns depended on the number of stern racks and k-guns (sided projectors). A minimal setup was one stern rack and two k-guns (one on each side). This produced a 5 charge pattern, three from the rack and one from each k-gun. The stern rack, of course, dropped its three charges in a line astern while the k-gun shot theirs out to the side. The pattern was thus a four-cornered diamond with a charge in the middle.

If you added another two k-guns, you got a pattern of seven, a hexagon with a center charge."

"Launching depth charges was no simple task, they were clumsy and heavy, hard to handle on the quarterdeck of a lively escort. The main launcher was a 12-chage launching rack first used in WWI, but still not universal in 1939."

"Control mechanisms were simple. They ranged from a junior officer with a stopwatch to an automated release clock on which speed was entered and the pattern dropped automatically, up to bridge controls for dropping the pattern. "

Good to know. Perhaps some further edits to the pic (and the springstyle) are needed.

For additional firepower forward, what about firing Q turret over the bridge, as was planned with the Fletchers?

I'm sure you could do it, just not dirrectly ahead as the funnels and bridge would be in the way. I'm sure the captain would frown upon seeing one his own ships shells droping into his chair while he's having his cup of coffee.

In her current arrangment Bhubaneshwar has too much clutter forward of Q turret to have any real practical reason to fire over the bridge.

Quoted

I'm sure the captain would frown upon seeing one his own ships shells droping into his chair while he's having his cup of coffee.

"How many shells do you wish in your coffee, sir?"

"one lump or two sir?"

Wouldn't that be:
"one KABOOM or two sir?" :-)

As I said, Fletchers were intended to do that, at long range/high elevation. I don't know if any actually did in combat, though

Some tinkering around with the pic. The upper set shows the original design with some DC throwers abaft the forward funnel and also the amidships 12.5 cm gun.

The lower set of pics show an alternate layout with the break in freeboard further forward, and the inclusion of a larger blast-shield (or whatever the proper term is) around the entire aft superstructure. With the lower location of the AA guns on the second funnel, I think the amidships 12.5 cm gun could reasonable engage targets on the bow (though not directly ahead, obviously).

Comments?

Aw, c'mon guys. Aren't destroyers s'posed to have raked masts and funnels. Other than that, she looks like a winner, 'specially with the torpedo tubes mounted lower-down on the upper deck.

Remember you're talking to the guy who likes pagoda masts. I like to do things a bit differently.

She looks much better now, my only nitpick is her aft superstructure can be narrowed slightly. The bow in the top veiw looks rather sharp too, I don't want to prick my finger on the drawing.

Blast shield? Hmm, I'm thinking more for weatherproofing. Having it there for blast makes no sense as the mount below will be hit by the overpressure.

Definitely the second pic.

Definitly much better-looking.