I test a SS for the conversion of the 15 yo Caravani class to a troop transport
I remove 2/3 of the 120mm guns, remove all TT, remove too 3 of the 4 boilers.
Add bulges to maintain stability.
Here is the original SS
750T, Peru DD laid down 1905 (Engine 1906)
Displacement:
750 t light; 782 t standard; 909 t normal; 1 010 t full load
Dimensions: Length overall / water x beam x draught
288.71 ft / 288.71 ft x 29.53 ft x 9.24 ft (normal load)
88.00 m / 88.00 m x 9.00 m x 2.82 m
Armament:
2 - 4.72" / 120 mm guns in single mounts, 52.72lbs / 23.91kg shells, 1905 Model
Breech loading guns in deck mounts
on centreline, evenly spread
1 - 4.72" / 120 mm guns in single mounts, 52.72lbs / 23.91kg shells, 1905 Model
Breech loading gun in deck mounts
on centreline, all amidships, 1 raised gun
2 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1905 Model
Quick firing guns in deck mounts
on side, evenly spread, all raised mounts
2 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1905 Model
Machine guns in deck mounts
on side, evenly spread
Weight of broadside 185 lbs / 84 kg
Shells per gun, main battery: 120
4 - 21.0" / 533.4 mm above water torpedoes
Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.79" / 20 mm - -
2nd: 0.79" / 20 mm - -
3rd: 0.79" / 20 mm - -
4th: 0.50" / 13 mm - -
Machinery:
Oil fired boilers, steam turbines,
Direct drive, 2 shafts, 8 773 shp / 6 545 Kw = 24.79 kts
Range 5 000nm at 10.00 kts
Bunker at max displacement = 229 tons
Complement:
82 - 107
Cost:
£0.102 million / $0.406 million
Distribution of weights at normal displacement:
Armament: 23 tons, 2.5 %
Armour: 9 tons, 1.0 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 9 tons, 1.0 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.0 %
Machinery: 399 tons, 43.9 %
Hull, fittings & equipment: 249 tons, 27.4 %
Fuel, ammunition & stores: 159 tons, 17.5 %
Miscellaneous weights: 70 tons, 7.7 %
Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
307 lbs / 139 Kg = 5.8 x 4.7 " / 120 mm shells or 0.3 torpedoes
Stability (Unstable if below 1.00): 1.36
Metacentric height 1.4 ft / 0.4 m
Roll period: 10.5 seconds
Steadiness - As gun platform (Average = 50 %): 95 %
- Recoil effect (Restricted arc if above 1.00): 0.33
Seaboat quality (Average = 1.00): 1.69
Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.404
Length to Beam Ratio: 9.78 : 1
'Natural speed' for length: 16.99 kts
Power going to wave formation at top speed: 56 %
Trim (Max stability = 0, Max steadiness = 100): 56
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 17.72 ft / 5.40 m
- Forecastle (18 %): 13.45 ft / 4.10 m
- Mid (50 %): 11.48 ft / 3.50 m
- Quarterdeck (18 %): 10.83 ft / 3.30 m
- Stern: 10.83 ft / 3.30 m
- Average freeboard: 12.24 ft / 3.73 m
Ship tends to be wet forward
Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 169.5 %
- Above water (accommodation/working, high = better): 97.7 %
Waterplane Area: 5 260 Square feet or 489 Square metres
Displacement factor (Displacement / loading): 65 %
Structure weight / hull surface area: 25 lbs/sq ft or 123 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.50
- Longitudinal: 1.64
- Overall: 0.56
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is adequate
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather
Caravani-1905 - El Alto-Sucre-1906 - Cochabamba-1907
Potosi-1908 - Oruro-Montero-1909 - Trinitad-1910
- 25T: fire control
- 25T: Marconi
- 13T: Weight reserve
- 7T: 20 Depth Charges or 6 Mines
---------------------------------------------------------
The conversion SS
870T, Peru 1920 troop transport laid down 1905 (Engine 1906)
Displacement:
869 t light; 894 t standard; 1 030 t normal; 1 139 t full load
Dimensions: Length overall / water x beam x draught
288.71 ft / 288.71 ft x 29.53 ft (Bulges 33.46 ft) x 9.24 ft (normal load)
88.00 m / 88.00 m x 9.00 m (Bulges 10.20 m) x 2.82 m
Armament:
1 - 4.72" / 120 mm guns in single mounts, 52.72lbs / 23.91kg shells, 1905 Model
Breech loading gun in deck mount
on centreline forward
2 - 1.57" / 40.0 mm guns (1x2 guns), 1.95lbs / 0.88kg shells, 1905 Model
Breech loading guns in deck mount
on centreline aft
2 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1905 Model
Quick firing guns in deck mounts
on side, evenly spread
Weight of broadside 57 lbs / 26 kg
Shells per gun, main battery: 120
Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.79" / 20 mm - -
Machinery:
Oil fired boilers, steam turbines,
Direct drive, 2 shafts, 2 193 shp / 1 636 Kw = 16.90 kts
Range 5 000nm at 10.00 kts
Bunker at max displacement = 245 tons
Complement:
90 - 118
Cost:
£0.056 million / $0.225 million
Distribution of weights at normal displacement:
Armament: 7 tons, 0.7 %
Armour: 2 tons, 0.2 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 2 tons, 0.2 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.0 %
Machinery: 142 tons, 13.8 %
Hull, fittings & equipment: 420 tons, 40.8 %
Fuel, ammunition & stores: 161 tons, 15.6 %
Miscellaneous weights: 298 tons, 28.9 %
Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1 684 lbs / 764 Kg = 31.9 x 4.7 " / 120 mm shells or 0.8 torpedoes
Stability (Unstable if below 1.00): 1.00
Metacentric height 0.8 ft / 0.2 m
Roll period: 15.7 seconds
Steadiness - As gun platform (Average = 50 %): 100 %
- Recoil effect (Restricted arc if above 1.00): 0.08
Seaboat quality (Average = 1.00): 2.00
Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.404
Length to Beam Ratio: 8.63 : 1
'Natural speed' for length: 16.99 kts
Power going to wave formation at top speed: 38 %
Trim (Max stability = 0, Max steadiness = 100): 56
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 17.72 ft / 5.40 m
- Forecastle (18 %): 13.45 ft / 4.10 m
- Mid (50 %): 11.48 ft / 3.50 m
- Quarterdeck (18 %): 10.83 ft / 3.30 m
- Stern: 10.83 ft / 3.30 m
- Average freeboard: 12.24 ft / 3.73 m
Ship tends to be wet forward
Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 82.1 %
- Above water (accommodation/working, high = better): 131.5 %
Waterplane Area: 5 260 Square feet or 489 Square metres
Displacement factor (Displacement / loading): 161 %
Structure weight / hull surface area: 42 lbs/sq ft or 204 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.90
- Longitudinal: 2.47
- Overall: 1.00
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is excellent
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather
- Bulges added to increase stability
- 3 boilers remove ; from 8773shp to 2193shp - from 399t to 142t
Weigh economised affected to material & troop transport
Any thoughts on this?
Bulges on a DD? Ay caramba! You do get it to 1.0 overall strength, so I guess that's ok.
Bulges would change the B/C of the hull, strictly speaking. I'm interested in opinions from others about how that relates to simming a modified ship in SS. My guess is the conclusion may be that SS's BC is for the non-bulged part of the hull maybe?
Otherwise, I'm not sure I'd want to deploy a ship with only one boiler. Whenever that boiler has to be inactivated to cleaning and maintenance, this ship would have no steam for ship service, much less going anywhere.
The boiler part I agree with, I'd keep 2. As to the BC/Bulge thing, I think the BC of the bulged version should be increased to represent the 'fatter' hullform due to the bulges. As to bulges on DDs, I believe the RN bulged some V&W class DDs to use them as fast troop craft similar to this idea. They used the bulge to store extra fuel oil.
You remove 3/4rd of the machinery, not only the boilers. The turbine weights are not negligible.
You are already spending over 200t of materials on the ship ( 170t for the hull strengthenings plus reconstruction). A newbuilt 800-1000t merchant standard transport would be cheaper, more reliable and have higher capacity.
QuoteA newbuilt 800-1000t merchant standard transport would be cheaper, more reliable and have higher capacity.
I agree totaly. This concept is just a test.
Jef