Oxygen Torpedoes VS late game BB *Post-Hotfix upadate*

[Accipiter]

This is a Followup to this other topic, since the game has been updated, the old one is now obsolete.

 

I have reproduced 2 times the same test as described in the original topic, under the Hotfix patch:

610mm Torpedoes with Oxygen Propulsion and 1940 Tech with Unlock mode: ON , the MOST powerful torpedoes possible in the game.

Target was an AI BB with 2 esport CA, the 1st one was based on the Bismark Hull and displaced around 80 000 Tons, on the second test, the BB was just a little under 100 000 Tons displacement, also based on the Bismark Hull.

In both tests, the BB Had Maximum Bulkheads. but i have no way to know what Bulkhead armor, Hull Bottom, Pumps, Auxilliary Power Plant, and Torpedo Protection Level the AI chose.

Results:

The 1st BB (80 000 Tons) was sunk in just about 20 Torpedos, the first 5-7 Torpedo hits almost completely nuked the structure to about 30% (like in the 1st test, after it reached that point structure would not go down further because all compartiments at the bottom of the hull where already red). and it flooded kind of slowly but continually (the flooding was not stopped quickly, unlike in the pre-hotfix test) untill sinking trough flooding. it is hard to tell if less torpedoes than 20 whould have been enough to sink it slowly trough flooding or not. i suspect the AI had not chosen good pumps or Bulkhead armor option, nor good torpedo defence system in this one, because the BB in the 2nd test did not behave the same (read on).

The 2nd BB (almost 100 000 Tons) took 31 Torpedoes to sink but even after over 20 Torpedoes hit (the initial volleys) first, his flooding eventually stabilized at around 20%, and the structure was still at 40% or so. the flooding was stabilized and the BB Still going; albeit with 3 out of 3 engines and the rudder damaged. the flooding whould probably have been brought back up a bit trough pumping too, given time. after the next torpedo volley hit (32 Hits total) the flooding was enough to bring the flooding from about 20% down to sinking (rather quickly). i count 31 hits to sink instead of 32 because the last hit happened just seconds before sinking and i do not think it made a difference. structure was still at about 40% when sinking.

As for the CA: on the second test, the AI did build 2 modern CA Hulls, the ones based on Admiral Hipper Hull (i think). they had Many bulkheads, and displaced about 17 500 Tons each. both where absolutely nuked and sunk near-instantly by 3 torpedoes hit each. the 1st one had its structure brougt very low (i think it was less than 10%) by the 3 hits, but moreover, started flooding incredibly quickly (some of the fastest flooding i've ever seen in this game) and went down from 100% to 0% Flooding and sunk in less than 10 seconds. the 2nd CA had the 3 torpedoes hit at good spacing all across the hull (one in the middle, one in the bow, one near the stern) and was instantly nuked to 0% Structure, sinking instantly trough structure damage. considering how quickly they sunk, i am pretty sure 2 torpedoes each whould have been enoug to sink them, 1 torpedo hit each whould have at least nearly sunk and crippled them.

Conclusion:

Much better than Pre-Hotfix. yet the late game BBs still seem overly survivable to torpedoes. bear in mind these are the most powerful torpedoes in the entire game, and it is unlikely the AI fully maxed out all the torpedo protection options; yet one BB was able to survive and stabilize after more than 20 torpedo hits well spread all across the hull!

Considering how easily they sunk the big 17 500 tons CA, i don't think the issue is the late game torpedoes being underpowered. i think it's more a case of big late game BB and BC with all the maxed out torpedo defence options stacking with their huge hull resistance stat becomes exponentially too much torpedo-resistant compared to smaller ships (though this is only my guess of course, i'm not sure).

*Edit*

i have also tried designing the BB myself: 130 000 Tons based on Bismark hull. Maxed out everything relating to hull resistance, torpedo protection and flooding reduction. 0% Weight offset. Diesel 2 engine (because it has more damage resistance). Also, 1000mm main belt and 280mm belt extended (don't think it makes any difference for torpedoes, but i had a bunch of weight leftover so...)

result:

Test 1: 39 torpedoes to sink. 47% structure remaining. AI was using 22 Inch torpedoes with (i think) fast propulsion, 10059dmg stat per torpedo.

Test 2: 43 torpedoes to sink. 48% (or 47%) structure remaining. AI was using 23 Inch torpedoes with (i think) Oxygen propulsion, 14119dmg stat per torpedo.
 

interesting to note the torpedo dmg and size essentially made no difference, and in both case it takes around 40 torpedoes to sink, and structure cannot be damaged more than to 47%.

Edited February 14, 2020 by Accipiter

[Shaftoe]

Late game BB from a torpedo boat/destroyer captain's perspective: 

 

[Friedrich]

Well I think we need to ask ourselves what level of torpedo defense, anti-flooding, etc the Yamato class had in game terms. Yamato and Musashi each provide a good metric, with the former being all to a single side and the latter being from every direction.

[arkhangelsk]

 

I suggest a way to try this is to make the battleship yourself - it's more important to control the qualities of the battleship than the destroyers. However, do note that Yamato is far from the ultimate in what can be achieved in torpedo protection. Here's an article filched from RamJB over at the Alpha v67 thread.

Quote

 

ARTICLE BY TIM THORTON
© 1987 WARSHIP MAGAZINE
...With his submerged speed limited to 10 knots he had no real alternative Course of action and although he was unable to identify it he was rewarded by the gratifying sound of one detonation.
...
After the attack, Yamato's speed was unimpaired and she continued on to Truk anchoring later the same day.
...
"A hole about 16ft (5m) deep extending downwards from the top of the bulge connection and 82ft (25m) in length between frames 151 and 173. Water flooded into No 3 turret upper magazine from a small hole in the longitudinal bulkhead caused by caving in of the waterline armor"

Put simply, her underwater defenses had been breached by a single torpedo and she had shipped over 3000 tons of water,
...
On the other hand, a shorter and beamier hull which was still thought likely to confer a speed comparable with future US ships was not without compensations which they did their best to exploit
...
The result was an armored central raft which left the bow and stern sections virtually unprotected. The smaller an area this raft represented the stronger could he the armor, and this was not of inconsiderable importance given that a single 12in cube of steel plate weighed a quarter of a ton. In the case of Yamato her great beam, which at the maximum was 127.7ft (38.9m), proved a great boon because her four main turbines and their associated boiler rooms could all be placed side by side across her hull. As a consequence, the area to be shielded shrank to a surprisingly short section of the hull, amounting to just 53.3 percent of the waterline length of 839ft (256m). This was a great achievement and her broad hull also conferred sufficient buoyancy for her to float even if all the unprotected spaces were left open to the sea after enemy action. 
...
Volume was the best protection against torpedoes since it allowed for the expansion of the explosive gases while the remaining force rapidly dissipated with distance. There was never enough internal volume in a hull to provide much space for this and designers generally had to be satisfied with providing the minimum.
...
The width of this around her machinery spaces was on average 5.1m, and was narrower than that of almost all her contemporaries in other navies despite her displacing considerably more. Two examples will suffice to illustrate this. The American North Carolina, on a displacement calculated in a comparable manner at 45,298 tons, had a system 5.6m deep, while the German Scharnhorst on only 35,398 tons still managed a depth of 5.4m. For Yamato, it was therefore essential that within the comparatively narrow space remaining the best possible arrangement was used.

In order to counter a torpedo explosion, a space outside the true hull was required which would be strong enough to detonate the weapon well away from a stronger yet flexible main bulkhead beneath. The Japanese developed empirical formulae to determine the thickness of protective bulkheads and bulges based on tests with models and full scale systems. Once established they were then used with much confidence and for Yamato the main bulkhead was to be 75mm ducol steel. When a full scale plate of this was duly tested in 1939 against a blast of 400kg of TNT, the results were encouraging since it did not split open although its watertight integrity was lost.
...
Given a larger bulge outboard this main defense would have been far more formidable but by linking it to the main belt the bulge was only 3m wide at most at mid-draft.
...
In the USN, the South Dakotas had a similar arrangement but they were designed within stringent Treaty constraints, a worry Yamato's designers did not have. In the US Montana class, a planned vessel of similar dimension to Yamato, the holding bulkhead was placed much deeper and not tied to the belt at all.
...
Yamato's outboard explosion chambers were left watertight and empty of anything more tangible than air. 

Since the advantages of liquid loading were understood, this result is difficult to comprehend
...
This is supported by the fact that a proposal to reduce the individual volume of compartments outside the citadel was rejected because the extra weight would have had an adverse effect on her draft.
...
This, in essence, is what happened when Skate's torpedo struck. Running shallow it hit the bulge where it was less than 2m wide and the main belt took most of the blast.
...
Nonetheless, even with the flaws discussed here her defenses were still powerful and her resilience under assault later amazed her American foes. However, her torpedo protection was without doubt the weakest element in an impressive design and it is not surprising that torpedoes were eventually to dispatch both vessels.

 

The takeaways (at least IMO) is that the Yamato has resilience due to her bulk and floatability, not due to her TDS or bulkheads. She takes more than the "minimum" amount of damage from torpedo hits (especially if they are 24 inch and/or have Torpex inside).

It is entirely possible to imagine that a properly done maximum TDS and bulkhead configuration, designed from the outset to resist 24 inch torpedoes, will be able to do significantly better.

[Accipiter]

14 hours ago, arkhangelsk said:

I suggest a way to try this is to make the battleship yourself - it's more important to control the qualities of the battleship than the destroyers.

Done. cheche the *Edit* section i added after conclusions in the OP