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Friday, July 5th 2013, 4:17am

Indochinese Subchaser

In order to continue the buildup of Indochina's Patrouille Navale, I am considering building an octet of these wood-hulled light subchasers for coastal work.

Quoted

[SIZE=3]Cam Ranh-class, Indochinese Submarine Chaser laid down 1944[/SIZE]

Displacement:
125 t light; 133 t standard; 165 t normal; 190 t full load

Dimensions: Length overall / water x beam x draught
120.42 ft / 114.83 ft x 18.37 ft x 6.07 ft (normal load)
36.71 m / 35.00 m x 5.60 m x 1.85 m

Armament:
1 - 2.95" / 75.0 mm guns in single mounts, 12.87lbs / 5.84kg shells, 1944 Model
Dual purpose gun in deck mount
on centreline forward
2 - 0.91" / 23.0 mm guns in single mounts, 0.37lbs / 0.17kg shells, 1944 Model
Machine guns in deck mounts
on side, all amidships
2 - 0.91" / 23.0 mm guns (1x2 guns), 0.37lbs / 0.17kg shells, 1944 Model
Machine guns in deck mount
on centreline aft
Weight of broadside 14 lbs / 7 kg
Shells per gun, main battery: 500

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.59" / 15 mm 0.20" / 5 mm -

- Conning tower: 0.59" / 15 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 1,100 shp / 820 Kw = 18.00 kts
Range 3,000nm at 15.00 kts
Bunker at max displacement = 58 tons

Complement:
22 - 29

Cost:
£0.066 million / $0.264 million

Distribution of weights at normal displacement:
Armament: 2 tons, 1.1 %
Armour: 1 tons, 0.6 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 1 tons, 0.4 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.2 %
Machinery: 28 tons, 17.1 %
Hull, fittings & equipment: 69 tons, 41.9 %
Fuel, ammunition & stores: 40 tons, 24.1 %
Miscellaneous weights: 25 tons, 15.2 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
316 lbs / 143 Kg = 24.6 x 3.0 " / 75 mm shells or 0.4 torpedoes
Stability (Unstable if below 1.00): 1.10
Metacentric height 0.5 ft / 0.1 m
Roll period: 11.2 seconds
Steadiness - As gun platform (Average = 50 %): 52 %
- Recoil effect (Restricted arc if above 1.00): 0.10
Seaboat quality (Average = 1.00): 1.27

Hull form characteristics:
Hull has rise aft of midbreak
and transom stern
Block coefficient: 0.450
Length to Beam Ratio: 6.25 : 1
'Natural speed' for length: 12.84 kts
Power going to wave formation at top speed: 70 %
Trim (Max stability = 0, Max steadiness = 100): 41
Bow angle (Positive = bow angles forward): 10.00 degrees
Stern overhang: 3.28 ft / 1.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 13.12 ft / 4.00 m
- Forecastle (20 %): 10.66 ft / 3.25 m
- Mid (50 %): 6.56 ft / 2.00 m (8.20 ft / 2.50 m aft of break)
- Quarterdeck (15 %): 8.20 ft / 2.50 m
- Stern: 8.20 ft / 2.50 m
- Average freeboard: 9.01 ft / 2.75 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 83.0 %
- Above water (accommodation/working, high = better): 101.6 %
Waterplane Area: 1,398 Square feet or 130 Square metres
Displacement factor (Displacement / loading): 170 %
Structure weight / hull surface area: 23 lbs/sq ft or 115 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.78
- Longitudinal: 10.10
- Overall: 1.00
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is adequate
Good seaboat, rides out heavy weather easily

Breakdown of Miscellaneous Weights:
- 2 tons for DRBN-1 navigational DEM (radar)
- 3 tons for DUBV-8 sonar
- 15 tons for depth bombs
- 5 tons for ASW mortars (Mousetrap equivalent)

2

Friday, July 5th 2013, 4:22am

The inclusion of a transom stern on such a small and relatively slow craft seems somewhat odd to me, but I can understand why it may have been chosen.

What is more surprising is that there would be a rise aft of the midbreak, rather than forward. Is that a deliberate choice?

This post has been edited 1 times, last edit by "BruceDuncan" (Jul 5th 2013, 4:22am)


3

Friday, July 5th 2013, 4:29am

Um... mistake, probably. Moment...

4

Friday, July 5th 2013, 4:33am

Seems that when I was inputting the freeboard figures, I didn't fully enter a digit, thus leaving a "2." rather than a "2.5". Trimmed freeboard slightly to make things right.

Quoted

[SIZE=3]Cam Ranh-class, Indochinese Submarine Chaser laid down 1944[/SIZE]

Displacement:
125 t light; 133 t standard; 165 t normal; 190 t full load

Dimensions: Length overall / water x beam x draught
120.42 ft / 114.83 ft x 18.37 ft x 6.07 ft (normal load)
36.71 m / 35.00 m x 5.60 m x 1.85 m

Armament:
1 - 2.95" / 75.0 mm guns in single mounts, 12.87lbs / 5.84kg shells, 1944 Model
Dual purpose gun in deck mount
on centreline forward
2 - 0.91" / 23.0 mm guns in single mounts, 0.37lbs / 0.17kg shells, 1944 Model
Machine guns in deck mounts
on side, all amidships
2 - 0.91" / 23.0 mm guns (1x2 guns), 0.37lbs / 0.17kg shells, 1944 Model
Machine guns in deck mount
on centreline aft
Weight of broadside 14 lbs / 7 kg
Shells per gun, main battery: 500

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.59" / 15 mm 0.20" / 5 mm -

- Conning tower: 0.59" / 15 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 1,100 shp / 820 Kw = 18.00 kts
Range 3,000nm at 15.00 kts
Bunker at max displacement = 58 tons

Complement:
22 - 29

Cost:
£0.066 million / $0.264 million

Distribution of weights at normal displacement:
Armament: 2 tons, 1.1 %
Armour: 1 tons, 0.6 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 1 tons, 0.4 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.2 %
Machinery: 28 tons, 17.1 %
Hull, fittings & equipment: 69 tons, 41.9 %
Fuel, ammunition & stores: 40 tons, 24.1 %
Miscellaneous weights: 25 tons, 15.2 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
318 lbs / 144 Kg = 24.7 x 3.0 " / 75 mm shells or 0.4 torpedoes
Stability (Unstable if below 1.00): 1.10
Metacentric height 0.5 ft / 0.1 m
Roll period: 11.2 seconds
Steadiness - As gun platform (Average = 50 %): 52 %
- Recoil effect (Restricted arc if above 1.00): 0.10
Seaboat quality (Average = 1.00): 1.27

Hull form characteristics:
Hull has a flush deck
and transom stern
Block coefficient: 0.450
Length to Beam Ratio: 6.25 : 1
'Natural speed' for length: 12.84 kts
Power going to wave formation at top speed: 70 %
Trim (Max stability = 0, Max steadiness = 100): 41
Bow angle (Positive = bow angles forward): 10.00 degrees
Stern overhang: 3.28 ft / 1.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 13.12 ft / 4.00 m
- Forecastle (20 %): 10.50 ft / 3.20 m
- Mid (50 %): 7.87 ft / 2.40 m
- Quarterdeck (15 %): 7.87 ft / 2.40 m
- Stern: 7.87 ft / 2.40 m
- Average freeboard: 9.00 ft / 2.74 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 83.0 %
- Above water (accommodation/working, high = better): 102.6 %
Waterplane Area: 1,398 Square feet or 130 Square metres
Displacement factor (Displacement / loading): 170 %
Structure weight / hull surface area: 24 lbs/sq ft or 115 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.77
- Longitudinal: 10.06
- Overall: 1.00
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is adequate
Good seaboat, rides out heavy weather easily

5

Friday, July 5th 2013, 4:37am

Looks very neat, and close to historical French subchaser designs. A logical craft for local construction in Indochina. The draft is shallow enough to facilitate inshore operations and interdiction of coastal traffic, yet the ships is weatherly.

6

Friday, July 5th 2013, 4:38am

Seems pretty small to carry a Mousetrap or the like...

7

Friday, July 5th 2013, 5:13am

Quoted

Originally posted by The Rock Doctor
Seems pretty small to carry a Mousetrap or the like...

The USN 110' subchasers built in World War II often mounted Mousetrap on the bow. Several were sunk when the charges accidentally blew up...

8

Friday, July 5th 2013, 4:40pm

I was unaware of that - good to know.

9

Friday, July 5th 2013, 7:54pm

Quoted

Originally posted by The Rock Doctor
I was unaware of that - good to know.

Yes: here's some photo evidence. The Mousetrap launchers can be seen on the foredeck.