Simple Naval Answers to Simple Naval Questions: Why did German naval artillery shells during WWII have a knack of not detonating when they hit an enemy ship?

[dseehafer]

Greetings all,

 

A new little series for you lot. Its real simple, its all in the title.

 

Anyone who begins to dig deep into German naval history during the Second World War will soon notice a recurring problem. There are several recorded instances where a German ship fired upon and hit an enemy target but the shell passed through without detonating.

 

For example, Admiral Hipper hit HMS Berwick 4 or 5 times and none of the shells that hit Berwick detonated within the ship, Gneisenau hit HMS Renown 2 or 3 times and none of her shells detonated, Scharnhorst hit DoY 2 or 3 times and none of her shells detonated, the list goes on...

 

Most assume that the shells were simply faulty, or duds, or that they were poorly made or designed. However, truthfully, none of these are the case. You see, when German naval engineers set out to solve one problem, they created another. Allow me to explain...

 

In order to achieve superior penetration, the Germans equipped their armor-piercing shells with what is known as a "Makarov's Cap". The armor-piercing tip was extremely tightly fastened to the shell glass with the help of special high-temperature welding using Krupp technology. This increased the amount of armor the shell could penetrate before losing it's cap. Post-war American tests showed that removal of the cap required the thickness of a homogenous armor of 0.12 caliber, which is approximately 50% more than for similar shells from other countries. However, there was a side-effect, these same tests revealed that, in order for the shell to arm itself, it needed to penetrate at least 7% of the shell's caliber in armor...

 

Simply put, if a shell passed through a unarmored (or lightly armored) area of an enemy ship it would not detonate. 

 

Shown below is the minimum armor thickness required to arm different sized WWII German naval artillery shells

 

380mm - 27mm
280mm - 20mm
203mm - 14mm
150mm - 11mm

 

 

Well, now you know! Hope you enjoyed! Keep your eyes peeled for the next one!

 

 

[Stauffenberg44]

OK. Well the Kreigsmarine seems to have gotten it about right for the poor Hood.

[crzyhawk]

It really wasn't uncommon for any navy to hit with a large amount of duds.  If I had to hazard a guess, it's probably a similar issue that USN torpedoes had early in the war with brittle firing pins.  Those shells had a lot of mass, making very sudden stops.

[Crucis]

Did you seriously need such a long thread title?

[mohawkdriver]

Good information.  So, true overpenetration was the culprit?

[Khafni]

Thanks dseehafer! I certainly appreciate the information you bring to all your posts. Thanks for the research leg work.

[HMCS_Devilfish]

3 hours ago, dseehafer said:

Greetings all,

 

A new little series for you lot. Its real simple, its all in the title.

 

Anyone who begins to dig deep into German naval history during the Second World War will soon notice a recurring problem. There are several recorded instances where a German ship fired upon and hit an enemy target but the shell passed through without detonating.

 

For example, Admiral Hipper hit HMS Berwick 4 or 5 times and none of the shells that hit Berwick detonated within the ship, Gneisenau hit HMS Renown 2 or 3 times and none of her shells detonated, Scharnhorst hit DoY 2 or 3 times and none of her shells detonated, the list goes on...

 

Most assume that the shells were simply faulty, or duds, or that they were poorly made or designed. However, truthfully, none of these are the case. You see, when German naval engineers set out to solve one problem, they created another. Allow me to explain...

 

In order to achieve superior penetration, the Germans equipped their armor-piercing shells with what is known as a "Makarov's Cap". The armor-piercing tip was extremely tightly fastened to the shell glass with the help of special high-temperature welding using Krupp technology. This increased the amount of armor the shell could penetrate before losing it's cap. Post-war American tests showed that removal of the cap required the thickness of a homogenous armor of 0.12 caliber, which is approximately 50% more than for similar shells from other countries. However, there was a side-effect, these same tests revealed that, in order for the shell to arm itself, it needed to penetrate at least 7% of the shell's caliber in armor...

 

Simply put, if a shell passed through a unarmored (or lightly armored) area of an enemy ship it would not detonate. 

 

Shown below is the minimum armor thickness required to arm different sized WWII German naval artillery shells

 

380mm - 27mm
280mm - 20mm
203mm - 14mm
150mm - 11mm

 

 

Well, now you know! Hope you enjoyed! Keep your eyes peeled for the next one!

 

 

That’s interesting, my first guess would have been sabotage as Germany was into forced labour bigtime 

After the war some German tanks were rebuilt to original condition for collectors and what they found was oil galleries plugged with cigarette butts gear teeth filed down that kind of thing

[Doomlock]

Oo, nice thread! Thanks! 

[dseehafer]

7 hours ago, Crucis said:

Did you seriously need such a long thread title?

 

Yeah, its a bit long. But I dont see how i could have left anything out without offputting the reader. Leaving out "WWII" would have been confusing because WWI German shells did not have this issue. Leaving out "naval" would have been confusing because then people would have  thought i was talking about all shells period. So on and so forth.

 

The next one will have a shorter title. ;)

[Crucis]

3 hours ago, dseehafer said:

 

Yeah, its a bit long. But I dont see how i could have left anything out without offputting the reader. Leaving out "WWII" would have been confusing because WWI German shells did not have this issue. Leaving out "naval" would have been confusing because then people would have  thought i was talking about all shells period. So on and so forth.

 

The next one will have a shorter title. ;)

Could have written something like:  Why were so many German shells duds in WW2?  I think we all know what a dud is.

[dseehafer]

17 minutes ago, Crucis said:

Could have written something like:  Why were so many German shells duds in WW2?  I think we all know what a dud is.

 

But they weren't duds, that's the point. A dud is a shell that doesn't explode because of an internal error. There was nothing wrong with the German shells, they just didn't meet the minimum thickness of armor required to detonate. They were working as intended, there was nothing wrong with the shells, and therefore weren't duds.

 

Also your title would be confusing because it's not specific to the naval shells. It just says German shells, as in any German shell from any military branch. We're not talking about army shells.

[Crucis]

1 minute ago, dseehafer said:

 

But they weren't duds, that's the point. A dud is a shell that doesn't explode because of an internal error. There was nothing wrong with the German shells, they just didn't meet the minimum thickness of armor required to detonate. They were working as intended, there was nothing wrong with the shells, and therefore weren't duds.

Better to say duds, even if it wasn't 100% accurate than to burden people with utterly ridiculous, grossly long titles.  A title that's more than a single short line is a failure on the part of the writer of said title.  And said writer should immediately delete it and start over again, and continue to do so until he or she gets it right.

 

[Murotsu]

So, from the information given in the OP, the Germans designed their rounds wrong.  They went for maximum armor penetration, instead of maximum destructive power regardless of where the round hit the enemy ship.  I think that's a poor trade off given that most of any ship is lightly armored or not at all protected.  It's like the Japanese diving shell design.  When on the rare occasion it gets to function as designed it's a great and deadly thing.  But, the rest of the time it performs markedly inferior to other rounds.

So, there was something wrong with German naval rounds.  They were designed to accomplish a specific task that they rarely encountered but would be much better than other nation's rounds in that limited capacity while sacrificing a more general destructiveness when they didn't encounter the conditions for which they were designed.

[mofton]

Question - does that thickness have to be concurrent, or can it be separated?

For instance with Berwick I'm pretty sure if the shell passed through the shell plating on both sides of the ship it would be >14mm so might well set it off, even if it missed everything heavier.

 

I would be interested to know what the required penetration percentage was compared to other nations. Was 7% of caliber for detonation a wild outlier, or just slightly atypical?

[dseehafer]

2 hours ago, mofton said:

Question - does that thickness have to be concurrent, or can it be separated?

For instance with Berwick I'm pretty sure if the shell passed through the shell plating on both sides of the ship it would be >14mm so might well set it off, even if it missed everything heavier.

 

I would be interested to know what the required penetration percentage was compared to other nations. Was 7% of caliber for detonation a wild outlier, or just slightly atypical?

 

Interesting question! While my source doesn't directly say it, I'm almost certain it would have to be concurrent. It would also have to be a homogenous armor plate, I don't know that Berwick has homogenous hull armor as thin as or thinner than 14mm.

[Jumarka]

The amount of "bad luck" the surface ships of the Kriegsmarine had in WW2 is astounding.

[Lord_Slayer]

On 10/25/2017 at 9:46 PM, Stauffenberg44 said:

OK. Well the Kreigsmarine seems to have gotten it about right for the poor Hood.

 

They now now believe Hood was penetrated through the belt armor. That would have armed the Shell.

 

[hipcanuck]

On 10/28/2017 at 2:26 AM, Lord_Slayer said:

 

They now now believe Hood was penetrated through the belt armor. That would have armed the Shell.

 

 

Got a source? The math Ive seen says Bismarcks shells had a very, very slim chance to penetrate through the belt or deck at the range Hood was at.

 

Im more inclined to believe Hood blew herself up.

[Dunk_Master_Flex]

32 minutes ago, hipcanuck said:

 

Got a source? The math Ive seen says Bismarcks shells had a very, very slim chance to penetrate through the belt or deck at the range Hood was at.

 

Im more inclined to believe Hood blew herself up.

 

What? At such a range and angle, Hood's deck would have almost surely deflected or protected her from any 15 inch or 8 inch shells.

 

http://www.zhanliejian.com/navweaps/INRO_Hood_p3.htm

Give this a read, belt armor penetration is the most likely candidate by far for Hood's sinking. 

[Murotsu]

On ‎10‎/‎27‎/‎2017 at 11:26 PM, Lord_Slayer said:

 

They now now believe Hood was penetrated through the belt armor. That would have armed the Shell.

 

Whereas I think it was a case of the shell hitting the deck and ricocheting off but in doing so it gouged a big chunk of armor off through overmatch that sprayed into the magazine (the British put the powder magazine above the shell magazine for stability reasons unlike US or German practice of putting the powder magazines at the bottom of the ship for maximum protection) igniting the powder and leading to the magazine detonation.  This sort of thing has been seen on a number of battleships in both WW 1 and 2.

So, a full penetration wouldn't be necessary to ignite the magazines and then in a few minutes lead to an explosion as was witnessed with Hood.  This would also eliminate the need for the shell to explode.

[mofton]

13 minutes ago, Murotsu said:

Whereas I think it was a case of the shell hitting the deck and ricocheting off but in doing so it gouged a big chunk of armor off through overmatch that sprayed into the magazine (the British put the powder magazine above the shell magazine for stability reasons unlike US or German practice of putting the powder magazines at the bottom of the ship for maximum protection) igniting the powder and leading to the magazine detonation.  This sort of thing has been seen on a number of battleships in both WW 1 and 2.

So, a full penetration wouldn't be necessary to ignite the magazines and then in a few minutes lead to an explosion as was witnessed with Hood.  This would also eliminate the need for the shell to explode.

I had read somewhere that the powder-shell arrangement on the British ships was more to do with concerns about mine/torpedo damage from below setting off the powder than shell damage from above.

Once they realized post-WWI that the risk was slight I believe the later Admiral's onwards would have had it rectified.

The penetration properties of shrapnel, even a big chunk of it penetrating even Hood's thinnish lower deck armor I don't necessarily buy.

[Murotsu]

47 minutes ago, mofton said:

I had read somewhere that the powder-shell arrangement on the British ships was more to do with concerns about mine/torpedo damage from below setting off the powder than shell damage from above.

Once they realized post-WWI that the risk was slight I believe the later Admiral's onwards would have had it rectified.

The penetration properties of shrapnel, even a big chunk of it penetrating even Hood's thinnish lower deck armor I don't necessarily buy.

It happened to the Dunkerque at Mers el Kebir.  Turret 2's roof was crushed in by a 15" British shell.  Set that half of the turret's ammunition on fire and wiped out the gun crew.  Lion at Jutland took a turret hit like that, and only quick action by a surviving officer on the mount to flood the magazines saved the ship.  That's just two of several such incidents.

An 1800 lbs. shell like Bismarck fired hitting the 3" deck of Hood at an oblique angle would definitely cause it to shatter even if the shell ricocheted off.  Big chunks of steel could easily penetrate a quarter inch deck or bulkhead of mild steel and be hot enough to ignite powder.  That's all it takes.

I'm not saying with certainty it happened, but it is clearly possible and one way Hood might have been lost.  We will never know for sure though. But, we shouldn't dismiss any possibility that is within reason.

[mofton]

Ah, an interesting thought. I was thinking more that you were saying a weather deck hit throwing something through the armored deck, rather than directly. Your examples are good, flash/shrapnel into the turret did burn them out though the 'quick action' on Lion's Q turret prevented a catastrophe that cooked off about 30 minutes after the original hit.

 

[Azumazi]

2 hours ago, Murotsu said:

Whereas I think it was a case of the shell hitting the deck and ricocheting off but in doing so it gouged a big chunk of armor off through overmatch that sprayed into the magazine (the British put the powder magazine above the shell magazine for stability reasons unlike US or German practice of putting the powder magazines at the bottom of the ship for maximum protection) igniting the powder and leading to the magazine detonation.  This sort of thing has been seen on a number of battleships in both WW 1 and 2.

So, a full penetration wouldn't be necessary to ignite the magazines and then in a few minutes lead to an explosion as was witnessed with Hood.  This would also eliminate the need for the shell to explode.

One problem with that statement.

German powder rooms were above the shell handling rooms. This is also true for Scharnhorst and Bismarck. They considered such dangers less of an issue due to the fact that their propellant were partially protected by the metal casing for the rear charge and the fact that the propellant that they used was less volatile than most foreign navies.

(Bismarck's Forward Turret magazine arrangement)

As for if that happened to Hood, it's unlikely. I'm looking at Hood's armor layout now in her blueprints that HMS Hood society allowed to be published and at her magazines she had another lower deck above the powder rooms that's 2 inches thick. 2 inches is more than enough to stop any such spalling from the 3 inch armored deck before reaching the powder magazine.