Click on image to enlarge.
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To calculate the Soryu's real size estimates were made using standard published information. On the basis of the cut-aways (top) and other published diagrams a side drawing, with meter measurements, (immediately above) was created. This is all part of reverse-engineering the Soryu's principal particulars.
The conclusion (in summary) was:
- difference between calculations and standard published information is 800 to 1,100 tonnes and
- the Soryu is bigger by 25% to 33% in reality.
A heavier submarine requires more engine power and fuel to achieve speed-range requirements. The disparity in surface displacement (2,900 tonne published, but 3,700 tonnes estimated) would particularly impact the Soryu's surfaced, speed-range.
SPECIFICATION (with wiki published figures if available) | CALCULATION |
Pressure hull calculated volume: | 3,300 m3 |
Pressure hull displacement: | 3,300 x 1.025 (average seawater density) = 3,382 tonnes |
Estimated ballast tanks: | 500 tonnes |
Estimated external fuel tank: | 150m3 – 127 tonnes. Not sure much room left for more inside, even alongside batteries (compensating tanks and others need room too!) |
Estimated submerged displacement: | >4,200 tonnes (between 4,200 to 4,500 tonnes) |
Estimated surface displacement: (2,900 tonnes published in wiki) | >3,700 tonnes (= 4,200 tonnes – 500 tonnes): (between 3,700 tonnes to 4,000 tonnes) |
Estimated accuracy of calculations: | 300 tonnes (7 to 8%) |
Difference between calculations and standard published information: | 800 to 1,100 tonnes! |
Soryu is bigger by 25% to 33% in reality. |
ANONYMOUS COMMENT
"So that tells you something about Soryu's real size...
The reserve of buoyancy is indeed 13-15% on that submarine (500/3700). Sorry, not possible to add more ballast tanks, because your submarine would be too high on the water. And the pictures tell us that Soryu's draught is around 7.6-7.8 m. So I made the calcs on my software tool, they check out. !
The reserve of buoyancy is indeed 13-15% on that submarine (500/3700). Sorry, not possible to add more ballast tanks, because your submarine would be too high on the water. And the pictures tell us that Soryu's draught is around 7.6-7.8 m. So I made the calcs on my software tool, they check out. !
Shorter life expectancy raises another interesting point: the Japanese keep the same 2 Kawasaki diesel-generators sets on Australian Soryu but claim to extend Future Submarine life to 35 years; so either you de-rate their power by, say 50% and there is little left, or you ditch the engines every 15 years (current life span of Japanese boats)? by cutting the hull (can their steel accommodate that?). At the end of the day, the winner is: higher indiscretion ratio than Collins!
And fuel storage: largely inferior to what is needed. you would need to add 50% for the 3rd diesel and double the lot to have Collins legs. Issue: Soryu's design would become infeasible and diverge due to added length and drag etc...
SIMILAR DOUBTS
PETE'S COMMENT
SIMILAR DOUBTS
Geoff Slocombe, writing in the ASPI Strategist, March 11, 2016 also has doubts http://www.aspistrategist.org.au/sea-1000-is-there-a-strategic-necessity-to-choose-the-japanese-submarine/:
“Modern European submarine construction uses a single pressure hull, while the Soryu class uses a combination of double pressure hulls for the forward and aft compartments, but with a different steel alloy from single pressure hulls for the intermediate four compartments. Does this create differential expansion/cracking and corrosion problems at the dissimilar metal junction and is this the reason why Soryu has a 20 year life, not the 30 required by Australia?
While double pressure hulls increase a submarine’s reserve of buoyancy, they also increase cost and complexity of manufacture, probably give a shorter planned sea life, and increase the wetted area of the submarine requiring more energy to propel the vessel underwater.
A 4,200 tonnes Soryu has a crewing capacity around the same as Israeli Navy’s 2,400 tonnes Dolphin 2 Class submarines. The physical layout inside the current Soryu won’t meet ergonomic standards for future RAN submariners, affecting their alertness, health and welfare during a long range/endurance mission. Arguably the current Japanese internal design is inefficient and a poor starting point for an evolved Soryu detailed design.”
PETE'S COMMENT
The Anonymous calculations and observations tend to reinforce comments I made in a Submarine Matters article of February 12, 2015 where I wrote:
"One additional issue is that the Japanese Navy has been running its submarines with the assumption the service life is 15-20 years - while Australia assumes submarines should be in service for at least 30 yours. This may or may not be a problem. After 15-20 years moving parts may or may not start to wear out. This may be most significant in the submarine's diesel engines and the very large electrical motor. Changing engines-motors is very heavy maintenance involving cutting into the submarine hull. This might only be possible in Japan for the Soryu? Maintenance realities may or may not be a problem.
NO ELASTIC MOUNTS ON SORYUS
Anonymous also located the above diagram from the KHI
website specifically http://global.kawasaki.com/en/corp/rd/magazine/166/img/n166tr102a.jpg . Anonymous commented:
"Their "modular" building is indeed decks rigidly mounted/welded on the hull: there are NO pre-outfitted platforms on elastic mounts such as in Collins. So what? It means radiated noise much higher than Collins (seriously higher, not marginally: something like a dud sub of the 80s) and difficult to build".
Anonymous and Pete