Need help with WW2 Torpedo performance.

General naval discussions that don't fit within any specific time period or cover several issues.
steffen19k
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Need help with WW2 Torpedo performance.

Post by steffen19k » Sun May 19, 2019 5:17 pm

I'm playing World Of Warships and i've gotten into an argument about how torps work in the game vs. how they worked in reality. I've posted the remarks that have driven me to start this topic, and I'm looking for all the help I can get. Please note that I would like to use the information here to post on the World of Warships Forum so let me know if there are privacy concerns for you regarding your answer. Thank you in advance.
torpedoes have always been significantly more damaging and lethal than a battleship shell..even a full salvo of them... striking any class of ship.

Since I know someone will come and spew the 'it took 20x torps to sink Yamato/Musashi' argument I remind you that air dropped torps are significantly smaller in size/warhead than destroyer and cruiser launched torpedoes. Submarine torpedoes are also smaller than surface vessel torpedoes. 

Torpedoes carry more explosive power than an 18" Yamato shell and they hit from the underside where the armor and ship sections are sloped upwards. Torpedo bulges were an ad-hoc countermeasure that never really provided much defense against a torpedo hit from a surface ship or submarine given their warheads were much larger and the overpressure wave these heavier warheads created easily defeated the torpedo belt itself... but it did function very well vs air dropped torpedoes which had smaller warheads.
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OpanaPointer
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Re: Need help with WW2 Torpedo performance.

Post by OpanaPointer » Sun May 19, 2019 7:19 pm

We have a variety of items related to torpedoes at Hyperwar. Google "Hyperwar torpedoes" for links.

Byron Angel
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Re: Need help with WW2 Torpedo performance.

Post by Byron Angel » Mon May 20, 2019 4:10 am

steffen19k wrote:
Sun May 19, 2019 5:17 pm
I'm playing World Of Warships and i've gotten into an argument about how torps work in the game vs. how they worked in reality. I've posted the remarks that have driven me to start this topic, and I'm looking for all the help I can get. Please note that I would like to use the information here to post on the World of Warships Forum so let me know if there are privacy concerns for you regarding your answer. Thank you in advance.
torpedoes have always been significantly more damaging and lethal than a battleship shell..even a full salvo of them... striking any class of ship.

Since I know someone will come and spew the 'it took 20x torps to sink Yamato/Musashi' argument I remind you that air dropped torps are significantly smaller in size/warhead than destroyer and cruiser launched torpedoes. Submarine torpedoes are also smaller than surface vessel torpedoes. 

Torpedoes carry more explosive power than an 18" Yamato shell and they hit from the underside where the armor and ship sections are sloped upwards. Torpedo bulges were an ad-hoc countermeasure that never really provided much defense against a torpedo hit from a surface ship or submarine given their warheads were much larger and the overpressure wave these heavier warheads created easily defeated the torpedo belt itself... but it did function very well vs air dropped torpedoes which had smaller warheads.

Do follow up on Opanapointer's recommendation. Hyperwar is an indispensable reference source.

Torpedoes carried by WW2 surface warships, submarines (and even air-launched) carried high explosive warheads ranging from 600 to 1000+ lbs. By comparison, the HE content of a typical AP projectile was about 1.5-2.5 pct of overall projectile weight (i.e. - a US 16in 2700 lb AP had a HE charge of ~50 lbs. Any warship smaller than a BC, BB or CV likely had little or no anti-torpedo protection; also, the torpedo protection systems of older BB and CV classes, unless these ships were extensively re-fitted later in life, were usually unable to withstand the effects of larger warheads of newer torpedo classes (which they were never designed to resist). The damage effects inflicted by unimpeded torpedo hits were almost always of a critical nature - machinery, electrical or main battery or steering/propulsion damage and often a combination thereof - plus fires plus heavy flooding. A 75,000 ton Yamato might be able to absorb a dozen or more torpedo hits and stay afloat (while being heavily flooded, slowed down and losing stability), but 3 or 4 hits would almost without question be sufficient to sink an older Barham class BB. Two hits by a Japanese Type 93 torpedo had a 50/50 chance of sinking a heavy cruiser; a single hit would usually sink a destroyer and send a heavy cruiser into port for 6 months to a year of repair work.

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Thorsten Wahl
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Re: Need help with WW2 Torpedo performance.

Post by Thorsten Wahl » Tue May 21, 2019 9:26 am

Damagesummaries for german ships
Scharnhorst
https://drive.google.com/file/d/0B12aaM ... p=drivesdk
Lützow
https://drive.google.com/file/d/0B12aaM ... p=drivesdk

USN Damagereports
https://www.history.navy.mil/research/l ... ports.html

aka Captain_Hook_

very approximative:
a explosive charge weighting about 300 KGs of TNT produces about 291 m³ gaseous explosion products. this volume corresponds to a gas bubble with an radius of about 5 m.
Almost all light structures in this volume will be completely destroyed and removed. The fragments will riddle all adjacent plates in flight direction.

Heavier structures might survive: about 10 cm armor grade steal structure may survive in about 2 m distance but get ruptured if not flexible enough.
except if the compressionshock is delivered directly on this structure.
about 5 cm armor grade steel require about 4,5 m distance(Typical TDS protection).

increasing the weight of the charge does not increase the destruction in a linear manner.
a 600 kg charge produces about 580 m³ gaseous products. The created gas bubble should have a diameter of about 6,3 m

BUT WG has artistic freedom as far as real physics is concerned and differ considerably from reality :whistle:
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Byron Angel
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Re: Need help with WW2 Torpedo performance.

Post by Byron Angel » Tue May 21, 2019 6:56 pm

Hi Thorsten,
Would you agree it is fair to say (basically) that the radius of destruction is approximately equal to the cube root of the charge weight (assuming equivalent explosive performance)?

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Thorsten Wahl
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Re: Need help with WW2 Torpedo performance.

Post by Thorsten Wahl » Wed May 22, 2019 8:04 am

radius of destruction is (appears) approximately equal to the cube root
Yes and its modified by the type of explosive (aluminized explosives for instance produce more bubble whipping(have no better explanation)wich breaks up structures more easily over relatively larger distances instead of pulverizing them directly.

These explosives have a far better performance against surface-ship-targets at non contact explosions, there is a "optimal distance" depending on charge weight.

Submarines had exceptional good structural strenght, against them contact explosions appears as the better choice.
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marcelo_malara
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Re: Need help with WW2 Torpedo performance.

Post by marcelo_malara » Thu May 23, 2019 1:19 am

The torpedo protection of a modern battleship is about 5 m wide, that is why it is very difficult to sink a battleship with a couple of torpedoes, they just explode away from the vitals, they can not penetrate the hull as a shell does. On a cruiser it is almost imposible to find 5 m on each side for a decent anti torpedo protection.

Regards

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Re: Need help with WW2 Torpedo performance.

Post by Byron Angel » Sat May 25, 2019 11:09 pm

marcelo_malara wrote:
Thu May 23, 2019 1:19 am
The torpedo protection of a modern battleship is about 5 m wide, that is why it is very difficult to sink a battleship with a couple of torpedoes, they just explode away from the vitals, they can not penetrate the hull as a shell does. On a cruiser it is almost imposible to find 5 m on each side for a decent anti torpedo protection.

Regards
Hi Marcelo,
While depth of the defensive systems is without question important, the resistance of a torpedo defense system relies upon a number of other factors as well - basic design, nature(s) materiels employed in construction, details of physical method(s) of attachment employed of construction, accurate and up-to-date grasp of threat level over the service life of the ship, and proper "system management".

My impression is that this was (and remains) a complicated topic.

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marcelo_malara
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Re: Need help with WW2 Torpedo performance.

Post by marcelo_malara » Sun May 26, 2019 4:37 pm

I fully agree Byron. There is no easy way to know the effect of a hit. The Yamato was able to cope with about 10 torpedoes. But Scharnhorst was seriously damaged by one, same for Bismarck.

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Byron Angel
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Re: Need help with WW2 Torpedo performance.

Post by Byron Angel » Mon May 27, 2019 7:25 pm

marcelo_malara wrote:
Sun May 26, 2019 4:37 pm
I fully agree Byron. There is no easy way to know the effect of a hit. The Yamato was able to cope with about 10 torpedoes. But Scharnhorst was seriously damaged by one, same for Bismarck.

Regards
You raise an interesting argument: Irrespective of the strength/efficacy of any torpedo defense system or physical size (Yamato class @ 75,000t for example), every warship remains vulnerable to a crippling hit to steering or props. Such a hit may be low in percentage of likelihood, but there was at that time no known protection scheme.

That having been said, the powers of resistance to torpedo attack of Yamato and Musashi (in terms of retained flotation) were quire impressive - with best estimates of ten torpedo hits required (apart from numerous bomb hits) required to sink them.

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marcelo_malara
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Re: Need help with WW2 Torpedo performance.

Post by marcelo_malara » Tue May 28, 2019 12:43 am

The special case of the Q ships come to my mind. They were common merchant ships, but the holds were full of empty barrels, a torpedo may open the hull, but the barrels make the compartment permeability (I hope I am using the correct term, the percentage of a compartment that can be filled with water, 100% being a totally empty one) very low, making the foundering of such ships extremely hard.

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Re: Need help with WW2 Torpedo performance.

Post by Byron Angel » Tue Jun 04, 2019 3:01 pm

marcelo_malara wrote:
Tue May 28, 2019 12:43 am
The special case of the Q ships come to my mind. They were common merchant ships, but the holds were full of empty barrels, a torpedo may open the hull, but the barrels make the compartment permeability (I hope I am using the correct term, the percentage of a compartment that can be filled with water, 100% being a totally empty one) very low, making the foundering of such ships extremely hard.
Yes, I think the term "permeability" is apt. IIRC, for reference, the permeability of a typical compartment in a warship was ~65pct

Similar examples can be found in the case of laden tankers, whose cargoes of oil and other petroleum-based products meant that large amounts of interior hull volume were filled with fluid(s) of a specific gravity less than that of sea water. This made them more difficult to sink (if not afire).

I have also read of damaged timber carriers being kept afloat by their cargoes.

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