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[SIZE=3]Minesweepers of the Bulgarian Royal Navy[/SIZE]

Struma-class Minesweepers
Sold to Saudi Arabia 1936

Rila Mountains-class Minesweepers
- BVK Musala - M4 (1937)
- BVK Ovcharets - M5 (1937)
- BVK Golyam Kupen - M6 (1938)
- BVK Malyovitsa - M7 (1937)
- BVK Popova kapa - M8 (1937)
- BVK Lopushki vrah - M9 (1938)

[SIZE=1]Image originally by thesmilingassassin and modified by me[/SIZE]

[SIZE=3]Struma, Bulgarian Minesweeper laid down 1935[/SIZE]

Displacement:
430 t light; 442 t standard; 499 t normal; 544 t full load

Dimensions: Length overall / water x beam x draught
192.75 ft / 189.00 ft x 27.00 ft x 9.00 ft (normal load)
58.75 m / 57.61 m x 8.23 m x 2.74 m

Armament:
2 - 3.00" / 76.2 mm guns (1x2 guns), 13.39lbs / 6.08kg shells, 1935 Model
Dual purpose guns in deck mount
on centreline forward
2 - 1.57" / 40.0 mm guns in single mounts, 1.95lbs / 0.88kg shells, 1935 Model
Quick firing guns in deck mounts
on side, all amidships
4 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1935 Model
Machine guns in deck mounts
on side, evenly spread
Weight of broadside 31 lbs / 14 kg
Shells per gun, main battery: 150

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 1.57" / 40 mm - -
2nd: 0.79" / 20 mm - -

Machinery:
Diesel Internal combustion motors,
Direct drive, 2 shafts, 1,098 shp / 819 Kw = 16.00 kts
Range 5,000nm at 12.00 kts
Bunker at max displacement = 101 tons

Complement:
52 - 68

Cost:
£0.115 million / $0.461 million

Distribution of weights at normal displacement:
Armament: 4 tons, 0.8 %
Armour: 5 tons, 1.0 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 5 tons, 1.0 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.0 %
Machinery: 31 tons, 6.3 %
Hull, fittings & equipment: 209 tons, 42.0 %
Fuel, ammunition & stores: 69 tons, 13.9 %
Miscellaneous weights: 180 tons, 36.1 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,104 lbs / 501 Kg = 82.4 x 3.0 " / 76 mm shells or 0.8 torpedoes
Stability (Unstable if below 1.00): 1.06
Metacentric height 0.8 ft / 0.2 m
Roll period: 12.8 seconds
Steadiness - As gun platform (Average = 50 %): 50 %
- Recoil effect (Restricted arc if above 1.00): 0.06
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:
Hull has a flush deck
and transom stern
Block coefficient: 0.380
Length to Beam Ratio: 7.00 : 1
'Natural speed' for length: 16.50 kts
Power going to wave formation at top speed: 48 %
Trim (Max stability = 0, Max steadiness = 100): 25
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: 14.00 ft / 4.27 m
- Forecastle (20 %): 10.00 ft / 3.05 m
- Mid (50 %): 10.00 ft / 3.05 m
- Quarterdeck (15 %): 10.00 ft / 3.05 m
- Stern: 10.00 ft / 3.05 m
- Average freeboard: 10.32 ft / 3.15 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 66.4 %
- Above water (accommodation/working, high = better): 118.2 %
Waterplane Area: 3,228 Square feet or 300 Square metres
Displacement factor (Displacement / loading): 179 %
Structure weight / hull surface area: 37 lbs/sq ft or 183 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.94
- Longitudinal: 4.34
- Overall: 1.09
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is adequate
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

Ships in class:
- Struma (M1) - Sold to Saudi Arabia 1936
- Kamchiya (M2) - Sold to Saudi Arabia 1936
- Varbitsa (M3) - Sold to Saudi Arabia 1936

[SIZE=3]Rila Mountains-class, Bulgarian Minesweeper laid down 1937[/SIZE]

Displacement:
493 t light; 513 t standard; 581 t normal; 635 t full load

Dimensions: Length overall / water x beam x draught
197.75 ft / 194.00 ft x 27.00 ft x 9.00 ft (normal load)
60.27 m / 59.13 m x 8.23 m x 2.74 m

Armament:
2 - 3.46" / 88.0 mm guns (1x2 guns), 20.79lbs / 9.43kg shells, 1937 Model
Dual purpose guns in deck mount
on centreline forward
2 - 1.46" / 37.0 mm guns (1x2 guns), 1.55lbs / 0.70kg shells, 1937 Model
Anti-aircraft guns in deck mount
on centreline aft, all raised guns - superfiring
2 - 0.79" / 20.0 mm guns (1x2 guns), 0.24lbs / 0.11kg shells, 1937 Model
Anti-aircraft guns in deck mount
on centreline forward, all raised guns - superfiring
4 - 0.50" / 12.7 mm guns (2x2 guns), 0.06lbs / 0.03kg shells, 1937 Model
Machine guns in deck mounts
on side, all amidships, all raised mounts - superfiring
Weight of broadside 45 lbs / 21 kg
Shells per gun, main battery: 300

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

- Conning tower: 0.98" / 25 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 2,834 shp / 2,114 Kw = 19.00 kts (see notes)
Range 5,000nm at 12.00 kts
Bunker at max displacement = 121 tons

Complement:
58 - 76

Cost:
£0.180 million / $0.721 million

Distribution of weights at normal displacement:
Armament: 6 tons, 1.0 %
Armour: 4 tons, 0.7 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 2 tons, 0.4 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 1 tons, 0.3 %
Machinery: 79 tons, 13.5 %
Hull, fittings & equipment: 225 tons, 38.8 %
Fuel, ammunition & stores: 87 tons, 15.0 %
Miscellaneous weights: 180 tons, 31.0 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
971 lbs / 440 Kg = 46.7 x 3.5 " / 88 mm shells or 0.6 torpedoes
Stability (Unstable if below 1.00): 1.08
Metacentric height 0.8 ft / 0.2 m
Roll period: 12.6 seconds
Steadiness - As gun platform (Average = 50 %): 50 %
- Recoil effect (Restricted arc if above 1.00): 0.09
Seaboat quality (Average = 1.00): 1.73

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.431
Length to Beam Ratio: 7.19 : 1
'Natural speed' for length: 13.93 kts
Power going to wave formation at top speed: 58 %
Trim (Max stability = 0, Max steadiness = 100): 29
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: 14.00 ft / 4.27 m
- Forecastle (20 %): 11.00 ft / 3.35 m
- Mid (50 %): 11.00 ft / 3.35 m
- Quarterdeck (15 %): 11.00 ft / 3.35 m
- Stern: 11.00 ft / 3.35 m
- Average freeboard: 11.24 ft / 3.43 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 86.4 %
- Above water (accommodation/working, high = better): 118.9 %
Waterplane Area: 3,292 Square feet or 306 Square metres
Displacement factor (Displacement / loading): 150 %
Structure weight / hull surface area: 36 lbs/sq ft or 176 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.85
- Longitudinal: 4.60
- Overall: 1.01
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is adequate
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

Breakdown of Miscellaneous Weights:
- 10 tons for hydrophones
- 20 tons for depth charges
- 150 tons for minehunting, sweeping, and laying equipment

Ships in Class:
- BVK Musala - M4 (1937)
- BVK Ovcharets - M5 (1937)
- BVK Golyam Kupen - M6 (1938)
- BVK Malyovitsa - M7 (1937)
- BVK Popova kapa - M8 (1937)
- BVK Lopushki vrah - M9 (1938)

Notes:
The Rila Mountains-class is a modified version of the earlier Struma-class minesweepers, incorporating lessons learned from the preceding vessels. The Rilas return to the non-transom stern more desirable in mine operations, and have a larger twin 88mm dual-purpose gun mount.

The Rilas also come equipped with Voith Schneider propellers for better maneuverability during mine warfare operations.