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1

Friday, August 10th 2012, 8:53pm

Bulgarian refits

Proposed refit for the Bulgarian Danube class light cruisers. The proposed 25% refit will replace the 88mm secondary guns with new 57mm anti-aircraft guns, the old 37mm guns with the BNS's standard 40mm, and add radar. The living quarters will also be brought up to date.

Quoted

[SIZE=3]Danube class, Bulgarian Light Cruiser laid down 1935[/SIZE]

Displacement:
6,959 t light; 7,221 t standard; 7,841 t normal; 8,337 t full load

Dimensions: Length overall / water x beam x draught
565.43 ft / 557.74 ft x 59.06 ft x 16.66 ft (normal load)
172.34 m / 170.00 m x 18.00 m x 5.08 m

Armament:
9 - 5.91" / 150 mm guns (3x3 guns), 102.98lbs / 46.71kg shells, 1935 Model
Breech loading guns in turrets (on barbettes)
on centreline ends, majority forward, 1 raised mount - superfiring
2 - 2.24" / 57.0 mm guns (1x2 guns), 6.61lbs / 3.00kg shells, 1935 Model
Dual purpose guns in a deck mount with hoist
on centreline aft, all raised guns - superfiring
8 - 2.24" / 57.0 mm guns (4x2 guns), 6.61lbs / 3.00kg shells, 1935 Model
Dual purpose guns in deck mounts with hoists
on side, evenly spread
8 - 1.46" / 37.0 mm guns (4x2 guns), 1.55lbs / 0.70kg shells, 1935 Model
Anti-aircraft guns in deck mounts
on side, evenly spread
8 - 0.79" / 20.0 mm guns (4x2 guns), 0.24lbs / 0.11kg shells, 1935 Model
Anti-aircraft guns in deck mounts
on side, evenly spread, all raised mounts
Weight of broadside 1,007 lbs / 457 kg
Shells per gun, main battery: 180

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 3.94" / 100 mm 356.96 ft / 108.80 m 9.22 ft / 2.81 m
Ends: Unarmoured
Main Belt covers 98 % of normal length

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 4.72" / 120 mm 2.76" / 70 mm 3.94" / 100 mm
2nd: 1.57" / 40 mm 0.79" / 20 mm -
3rd: 1.57" / 40 mm 0.79" / 20 mm -
4th: 0.79" / 20 mm 0.39" / 10 mm -
5th: 0.39" / 10 mm - -

- Armour deck: 1.57" / 40 mm, Conning tower: 3.94" / 100 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 64,936 shp / 48,442 Kw = 32.00 kts
Range 6,000nm at 15.00 kts
Bunker at max displacement = 1,116 tons

Complement:
416 - 541

Cost:
£3.088 million / $12.353 million

Distribution of weights at normal displacement:
Armament: 125 tons, 1.6 %
Armour: 1,529 tons, 19.5 %
- Belts: 543 tons, 6.9 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 288 tons, 3.7 %
- Armour Deck: 665 tons, 8.5 %
- Conning Tower: 33 tons, 0.4 %
Machinery: 1,845 tons, 23.5 %
Hull, fittings & equipment: 3,344 tons, 42.6 %
Fuel, ammunition & stores: 881 tons, 11.2 %
Miscellaneous weights: 117 tons, 1.5 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
12,074 lbs / 5,477 Kg = 117.3 x 5.9 " / 150 mm shells or 1.7 torpedoes
Stability (Unstable if below 1.00): 1.22
Metacentric height 3.3 ft / 1.0 m
Roll period: 13.7 seconds
Steadiness - As gun platform (Average = 50 %): 49 %
- Recoil effect (Restricted arc if above 1.00): 0.25
Seaboat quality (Average = 1.00): 1.02

Hull form characteristics:
Hull has a flush deck
and transom stern
Block coefficient: 0.500
Length to Beam Ratio: 9.44 : 1
'Natural speed' for length: 27.07 kts
Power going to wave formation at top speed: 58 %
Trim (Max stability = 0, Max steadiness = 100): 48
Bow angle (Positive = bow angles forward): 15.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 28.71 ft / 8.75 m
- Forecastle (21 %): 21.33 ft / 6.50 m
- Mid (60 %): 17.22 ft / 5.25 m
- Quarterdeck (15 %): 17.22 ft / 5.25 m
- Stern: 17.22 ft / 5.25 m
- Average freeboard: 19.51 ft / 5.95 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 91.1 %
- Above water (accommodation/working, high = better): 193.0 %
Waterplane Area: 22,822 Square feet or 2,120 Square metres
Displacement factor (Displacement / loading): 124 %
Structure weight / hull surface area: 97 lbs/sq ft or 476 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.99
- Longitudinal: 1.37
- Overall: 1.02
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is excellent

Breakdown of Miscellaneous Weights:
- 30 tons for catapult
- 50 tons for 2x aircraft
- 37 tons for radar

2

Friday, August 10th 2012, 9:19pm

Looks to be a reasonable plan to refit them with radar - which is nearly a requirement at this point. I'm not entirely sold on relying on the 57mm as the primary AA weapon, but with improved fire control and radar direction it might be as good as the older 88mm guns.

A rather cost-conscious approach that should do well.

3

Saturday, August 11th 2012, 2:07am

The ex-German Gordi class light destroyers are intended to be used primarily for AA and ASW escort of major Bulgarian Navy assets - convoys, the cruisers, etc. Their relatively small size and low range isn't as much of a concern for the Bulgarian Navy, particularly as the ships were far superior to the torpedo boats they replaced.

Because the ships are seen as fairly valuable, an extensive refit is seen as useful. In this proposed refit, the engines are modernized, the trim adjusted, the 37mm guns are replaced with 40mm, the size of the magazines is increased slightly, and a modest electronics suite is added. In exchange, however, the torpedoes are dropped to free up room for the various new additions.

Quoted

[SIZE=3]Gordi class, Bulgarian Light Destroyer laid down 1932 (Engine 1943)[/SIZE]

Displacement:
987 t light; 1,048 t standard; 1,139 t normal; 1,211 t full load

Dimensions: Length overall / water x beam x draught
325.38 ft / 311.68 ft x 29.53 ft x 10.83 ft (normal load)
99.18 m / 95.00 m x 9.00 m x 3.30 m

Armament:
6 - 4.13" / 105 mm guns (3x2 guns), 35.32lbs / 16.02kg shells, 1932 Model
Dual purpose guns in deck mounts
on centreline ends, majority forward, 1 raised mount - superfiring
2 - 1.57" / 40.0 mm guns (1x2 guns), 1.95lbs / 0.89kg shells, 1943 Model
Anti-aircraft guns in deck mount
on centreline aft, all raised guns - superfiring
4 - 1.57" / 40.0 mm guns (2x2 guns), 1.95lbs / 0.89kg shells, 1943 Model
Anti-aircraft guns in deck mounts
on side, evenly spread, all raised mounts
Weight of broadside 224 lbs / 101 kg
Shells per gun, main battery: 300

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 1.18" / 30 mm 0.79" / 20 mm -
2nd: 0.79" / 20 mm 0.79" / 20 mm -
3rd: 0.39" / 10 mm - -

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 28,150 shp / 21,000 Kw = 33.50 kts
Range 3,000nm at 15.00 kts
Bunker at max displacement = 163 tons

Complement:
97 - 127

Cost:
£0.596 million / $2.384 million

Distribution of weights at normal displacement:
Armament: 28 tons, 2.5 %
Armour: 17 tons, 1.5 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 17 tons, 1.5 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.0 %
Machinery: 522 tons, 45.8 %
Hull, fittings & equipment: 366 tons, 32.1 %
Fuel, ammunition & stores: 152 tons, 13.3 %
Miscellaneous weights: 55 tons, 4.8 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
343 lbs / 155 Kg = 9.7 x 4.1 " / 105 mm shells or 0.3 torpedoes
Stability (Unstable if below 1.00): 1.14
Metacentric height 1.0 ft / 0.3 m
Roll period: 12.2 seconds
Steadiness - As gun platform (Average = 50 %): 71 %
- Recoil effect (Restricted arc if above 1.00): 0.39
Seaboat quality (Average = 1.00): 1.00

Hull form characteristics:
Hull has rise forward of midbreak
and transom stern
Block coefficient: 0.400
Length to Beam Ratio: 10.56 : 1
'Natural speed' for length: 20.33 kts
Power going to wave formation at top speed: 69 %
Trim (Max stability = 0, Max steadiness = 100): 71
Bow angle (Positive = bow angles forward): 30.00 degrees
Stern overhang: 3.28 ft / 1.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 18.04 ft / 5.50 m
- Forecastle (20 %): 18.04 ft / 5.50 m
- Mid (35 %): 18.04 ft / 5.50 m (11.48 ft / 3.50 m aft of break)
- Quarterdeck (15 %): 11.48 ft / 3.50 m
- Stern: 11.48 ft / 3.50 m
- Average freeboard: 13.78 ft / 4.20 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 173.8 %
- Above water (accommodation/working, high = better): 150.0 %
Waterplane Area: 5,879 Square feet or 546 Square metres
Displacement factor (Displacement / loading): 65 %
Structure weight / hull surface area: 30 lbs/sq ft or 146 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.50
- Longitudinal: 2.51
- Overall: 0.58
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is excellent
Ship has slow, easy roll, a good, steady gun platform

4

Saturday, August 11th 2012, 2:37am

This scheme looks good; it does mean sacrificing the offensive punch of the torpedo tubes, but if they are to be employed in a defensive role, that is less important. The miscellaneous weight, though modest and shared with sensors, should allow for a reasonable AS armament.

5

Saturday, August 11th 2012, 2:53am

In theory, I could have left the torpedoes onboard - Springsharp doesn't really force me to remove them - but they're not really adding much to the ship's mission-centric capabilities at the moment. But I figure that by the time I'm done adding the extra gear to the rebuilt ship, it would be more logical to replace them.

6

Saturday, August 11th 2012, 2:55am

Quoted

Originally posted by Brockpaine
In theory, I could have left the torpedoes onboard - Springsharp doesn't really force me to remove them - but they're not really adding much to the ship's mission-centric capabilities at the moment. But I figure that by the time I'm done adding the extra gear to the rebuilt ship, it would be more logical to replace them.


I agree. With a decent radar suite, their gun batteries would make them very effective AA escorts in confined waters.