WesWorld

After the incident that led to the loss of the chinese submarine, voices in the chinese navy have been raised, which called for a submarine rescue and recovery vessel. But how it will look like ? Inspired by a OTL ship the SMS Vulkan the promising hull form was a catamaran.



But we didn't have any rules for simulating a catamaran. After discussing this point with Brock and Walther, here is my first draft. Feel free to publish your opinions.

As discussed with Brock, both hulls have to be simed individually. After that putting ~ 15% of the light displacement aside for the bridge and other ship components. After that, sim the ship again, but now as monohull to get the full dimensions (beam = hull + dock + hull) and the stability numbers. This is why we have now two reports.

Step 1: Simulation of a single hull:

Displacement:
3,663 t light; 3,740 t standard; 3,867 t normal; 3,969 t full load

Dimensions: Length overall / water x beam x draught
446.19 ft / 446.19 ft x 27.56 ft x 20.01 ft (normal load)
136.00 m / 136.00 m x 8.40 m x 6.10 m

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 1 shaft, 3,210 shp / 2,395 Kw = 15.00 kts
Range 4,000nm at 10.00 kts
Bunker at max displacement = 229 tons

Complement:
244 - 318

Cost:
£0.915 million / $3.660 million

Distribution of weights at normal displacement:
Armament: 0 tons, 0.0 %
Machinery: 83 tons, 2.1 %
Hull, fittings & equipment: 1,240 tons, 32.1 %
Fuel, ammunition & stores: 204 tons, 5.3 %
Miscellaneous weights: 2,340 tons, 60.5 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
599 lbs / 272 Kg = 5.5 x 6 " / 152 mm shells or 0.1 torpedoes
Stability (Unstable if below 1.00): 0.59
Metacentric height 0.1 ft / 0.0 m
Roll period: 32.6 seconds
Steadiness - As gun platform (Average = 50 %): 86 %
- Recoil effect (Restricted arc if above 1.00): 0.00
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.550
Length to Beam Ratio: 16.19 : 1
'Natural speed' for length: 21.12 kts
Power going to wave formation at top speed: 21 %
Trim (Max stability = 0, Max steadiness = 100): 43
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: 23.23 ft / 7.08 m
- Forecastle (20 %): 14.80 ft / 4.51 m
- Mid (50 %): 14.80 ft / 4.51 m
- Quarterdeck (15 %): 14.80 ft / 4.51 m
- Stern: 14.80 ft / 4.51 m
- Average freeboard: 15.47 ft / 4.72 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 73.3 %
- Above water (accommodation/working, high = better): 96.1 %
Waterplane Area: 8,323 Square feet or 773 Square metres
Displacement factor (Displacement / loading): 154 %
Structure weight / hull surface area: 52 lbs/sq ft or 253 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 1.00
- Longitudinal: 2.91
- Overall: 1.11
Caution: Poor stability - excessive risk of capsizing
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is adequate
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, rides out heavy weather easily

Step 2: Simulation of the complete vessel:

The 15% aside (bridge and other ship components between the hulls) could be find in the Misc. Weight.

Quoted

Jin Yan Zi
China Submarine repair/recovery ship laid down 1943

Displacement:
7,394 t light; 7,549 t standard; 7,734 t normal; 7,882 t full load


Dimensions:
Length overall / water x beam x draught
446.19 ft / 446.19 ft x 89.24 ft x 20.01 ft (normal load)
136.00 m / 136.00 m x 27.20 m x 6.10 m

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 4,561 shp / 3,403 Kw = 15.00 kts
Range 4,000nm at 10.00 kts
Bunker at max displacement = 333 tons

Complement:
412 - 536

Cost:
£1.802 million / $7.208 million

Distribution of weights at normal displacement:
Armament: 0 tons, 0.0 %
Machinery: 118 tons, 1.5 %
Hull, fittings & equipment: 2,597 tons, 33.6 %
Fuel, ammunition & stores: 340 tons, 4.4 %
Miscellaneous weights: 4,680 tons, 60.5 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
12,876 lbs / 5,841 Kg = 119.2 x 6 " / 152 mm shells or 2.9 torpedoes
Stability (Unstable if below 1.00): 1.05
Metacentric height 4.7 ft / 1.4 m
Roll period: 17.4 seconds
Steadiness - As gun platform (Average = 50 %): 70 %
- Recoil effect (Restricted arc if above 1.00): 0.00
Seaboat quality (Average = 1.00): 1.63

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.340
Length to Beam Ratio: 5.00 : 1
'Natural speed' for length: 21.12 kts
Power going to wave formation at top speed: 27 %
Trim (Max stability = 0, Max steadiness = 100): 43
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: 23.23 ft / 7.08 m
- Forecastle (20 %): 14.80 ft / 4.51 m
- Mid (50 %): 14.80 ft / 4.51 m
- Quarterdeck (15 %): 14.80 ft / 4.51 m
- Stern: 14.80 ft / 4.51 m
- Average freeboard: 15.47 ft / 4.72 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 71.4 %
- Above water (accommodation/working, high = better): 165.8 %
Waterplane Area: 24,240 Square feet or 2,252 Square metres
Displacement factor (Displacement / loading): 157 %
Structure weight / hull surface area: 87 lbs/sq ft or 425 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.93
- Longitudinal: 1.80
- 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, rides out heavy weather easily

Further informations:
* Docksize = 97.6x10.4m

* 1110 tons of Misc. Weight simulate the bridge and other ship components between the hulls.

* 3570 tons of Misc. Weight includes cranes, pumps, ballast tanks, diving chamber, diving bells etc.

[size=1]thanks to Walther for the sim[/size]

Can't wait to get the feedback of the community.

And by the way, i know it's waste of material but i like this vessel.

Not sure if I did it the right way so if it is not right, then punch me and not parador.

The SMS Vulkan was smaller than this one. I simmed it for parador so it would be able to handle the biggest of the Chinese submarines (60% bigger than Vulkan when it comes to dimensions).

As for the name Jin Yan Zi, you can see her (played by Cheng Pei-pei) in action here

As stated via PM, I think the idea isn't very useful, particularly since there are much more logical and useful designs for submarine rescue and recovery vessels - designs which would be more justifiable on the basis of cost and historicity. We've already got one clone of the SMS Vulkan (the Danish one), and now it seems we're getting another. If people insist on making more catamarans, then I think we need to codify some gentlemen's design rules for them before we get any further.

No opinions or suggestions from other players ? By the way, i won't insist necessarily on this design, but a little feedback I would have expected.

Well, I find myself in agreement with Brock.

It seems that the approach you have chosen with the design is sound enough, though should catamaran style vessels become even more popular, we would need to lay down basic gents rules for them. On technical merits, I think the vessel is okay.

As a cost-effective answer to the need for recovering sunken submarines, I think it is overkill, particularly for a tonnage-strapped nation such as China. But then, perceived needs may trump cost-effectiveness, and the final decision is yours.

Tying up substantial tonnage in the proposed design will set back the fleet refurbishment program you have embarked upon; for the tonnage soaked up by one submarine rescue vessel you could build several large submarines or a host of smaller ones; or even a couple of destroyers or a light cruiser. It does not seem logical to forego much needed modern combatants in favor of one large auxiliary.

I haven't made any technical comment becuase I'm not sure how I'd sim a catamaran any better and you've obviously already had two inputs from other players who have played around with all kinds of ships on SS.

Submarine rescue; it's a mission that probably doesn't happen often. Even with Davis equipment deeper rescues are harder. I'm thinking of a scenario like the film, Morning Departure, where a shortage of Davis gear leaves men stranded below. Salvage is attempted but fails. A rescue is probably sound on morale grounds and to save experienced crews in peacetime. The flip-side of the coin is expense on a specialist ship which might not see much use and is it really any better than standard salvage tugs for this role?

I'm starting to think that, due to the difficulty of their construction, their cost should perhaps be something like 125% of light tonnage in order to reflect that complexity.

Quoted

Originally posted by Hood
The flip-side of the coin is expense on a specialist ship which might not see much use and is it really any better than standard salvage tugs for this role?

Quite right. This is the first time China's lost a submarine in game, and the apparent answer is to spend 7000+ tons to build a ship to salvage a twenty-five year old 400-ton submarine? While it's logical to rescue the crew, if possible, I can't really comprehend the scale of the overreaction. As I said earlier, a lightly-modified salvage tug would be better for submarine rescue: it can carry the diving bell and maintain station better than a catamaran, particularly a large one. Additionally, given the length of China's coastline, it might be necessary to have more than one ship. After all, what if the submarine goes down in the Gulf of Tonkin while the rescue ship's in the Bohai Sea? It's five days away at maximum speed.

Quoted

Originally posted by Brockpaine
I'm starting to think that, due to the difficulty of their construction, their cost should perhaps be something like 125% of light tonnage in order to reflect that complexity.?

http://commons.wikimedia.org/wiki/File:H…rke_nr473-1.jpg

Looking at the picture, it doesn't look very difficulty to construct this type of vessel. Because in my eyes it's more a ship with two hulls and not really like the modern catamerans.

Quoted

Originally posted by Brockpaine
Quite right. This is the first time China's lost a submarine in game, and the apparent answer is to spend 7000+ tons to build a ship to salvage a twenty-five year old 400-ton submarine? While it's logical to rescue the crew, if possible, I can't really comprehend the scale of the overreaction.

China sometimes tend to overreact at some points. In the opinion of others it may be look strange but that's chinese mentality

Quoted

Originally posted by Brockpaine
As I said earlier, a lightly-modified salvage tug would be better for submarine rescue: it can carry the diving bell and maintain station better than a catamaran, particularly a large one.

For saving the crew you are absolutely right. But this vessel will do both - rescuing the crew and salvaging the vessel. Until the time this vessel is taken into service,a modified salvage tug can take on this task - even if it will take years

Quoted

Originally posted by BruceDuncan
As a cost-effective answer to the need for recovering sunken submarines, I think it is overkill, particularly for a tonnage-strapped nation such as China. But then, perceived needs may trump cost-effectiveness, and the final decision is yours.

Tying up substantial tonnage in the proposed design will set back the fleet refurbishment program you have embarked upon; for the tonnage soaked up by one submarine rescue vessel you could build several large submarines or a host of smaller ones; or even a couple of destroyers or a light cruiser. It does not seem logical to forego much needed modern combatants in favor of one large auxiliary.

In the case of cost-effectivness none salvage ship is economic, because the tonnage of the salvaged vessels never outweight the costs of building this type of vessel. If this is the case, you won't have a reliable navy.
The priority for the construction of this ship does not have to come at first. So the fleet refurbishment program could still be active. Is it realistic for China building some hundred subs and destroyers or cruisers ??? Not really in my eyes. That's also a point why i put my eyes on the auxiliary fleet.