Prinz Eugen's Performance at DS Battle

Discussions about the history of the ship, technical details, etc.

Moderator: Bill Jurens

Tiornu
Supporter
Posts: 1222
Joined: Mon Oct 25, 2004 6:13 am
Location: Ex Utero

Post by Tiornu » Mon Jun 12, 2006 10:20 am

It is possible for a fuze to "work" yet without detonating the burster. That is, the fuze may perform exactly as designed, but the burster simply isn't detonated.
It is also possible for a fuze to initiate properly but be destroyed before finishing its own process.

Bgile
Senior Member
Posts: 3658
Joined: Wed Mar 09, 2005 7:33 pm
Location: Portland, OR, USA

Re: Armour Design

Post by Bgile » Mon Jun 12, 2006 7:46 pm

phil gollin wrote:If anyone has Raven and Roberts book on British Battleship Of World War Two, please turn to 154 and 155 which summarises the debate the RN had regarding side protection and the 1928 battleship design studies. (Which formed the beginings of the KGV designs).

These looked at both side armour and side protection against torpedoes/mines.

As far as armour was concerned the choice was (simplistically) between a modified Nelson type extended extremely thinned to the bottom (i.e. like the South Dakota system) and a deep external system (i.e. the KGV system). Both were examined based on the trajectories of various shell, one of which was a diving underwater short which penetrated towards the bottom of the ship having passed through 30 - 45 feet of water. The deep outer belt system was designed such that it would (in "fighting condition" be deep enough to intercept an shell in a still working fused condition. Shell which would strike under this belt would (normally) have to be only with non-working fuzes. It was noted that there was always a chance that the shell could hit whilst the ship was rolling away from the enemy and into a trough and MAYBE get to the unarmoured ships side in an operable condition, but even then it would only expolode on or just inside the torpedo defences.

So the POW side defence system worked as advertised and speculation on what might-have-beens is in the realm of vague possibilities.
You seem to be implying that if Bismarck had had PoW's side defensive system, she would not have suffered flooding from the side hit below her belt. Wasn't it low enough to pass under PoW's belt also?

phil gollin
Member
Posts: 167
Joined: Mon Oct 18, 2004 6:33 am

Post by phil gollin » Tue Jun 13, 2006 8:58 am

Not too sure I understand, but the POW's belt was low (or better deep) enough to keep most if not all operating shells away from the ship.

Only shells which had non-operating fuzes would get below the external belt (there could, of course always be the freaks where the combination of non-normal extra-long fuze delay, roll of ship and trough in the wave COULD get a shell into the ship below the belt but then it would explode in the torpedo side protection system).

For the vast majority of shell which hit the ship below the belt in a non-operable condition it all depends on remaining velocity, and possibly more importantly orientation. The 1928 study believed that heavy AP shell would start to tumble after about 25 feet under water. Thus the shell would hit the torpedo part of the side protection system at a much reduced velocity at an unknown orientation. This becomes a problem of what happens to a torpedo defence system when a large tumbling mass of metal hits it, and looking at the Bismarck and POW gives examples.

Tiornu
Supporter
Posts: 1222
Joined: Mon Oct 25, 2004 6:13 am
Location: Ex Utero

Post by Tiornu » Tue Jun 13, 2006 10:06 am

It certainly does seem that the hit on PoW was tumbling energetically by the time it penetrated the hull. I would be very interested in knowing if the hit on Bismarck was tumbling. Unfortunately, that is something we'll never know. The effect on the torpedo bulkhead might differ greatly depending on the shell's orientation. The nosepiece of an exploded shell sometimes has the ability to travel a long distance within a hull.
There are several books with good accounts of Japan's Tosa trials. Kaigun by Evans and Peattie is a good source. The underwater hit in that case landed about 25m short and burst effectively in the machinery spaces. A descent angle of 17deg is optimal for such hits.

Bgile
Senior Member
Posts: 3658
Joined: Wed Mar 09, 2005 7:33 pm
Location: Portland, OR, USA

Post by Bgile » Tue Jun 13, 2006 4:19 pm

phil gollin wrote:Not too sure I understand, but the POW's belt was low (or better deep) enough to keep most if not all operating shells away from the ship.

Only shells which had non-operating fuzes would get below the external belt (there could, of course always be the freaks where the combination of non-normal extra-long fuze delay, roll of ship and trough in the wave COULD get a shell into the ship below the belt but then it would explode in the torpedo side protection system).

For the vast majority of shell which hit the ship below the belt in a non-operable condition it all depends on remaining velocity, and possibly more importantly orientation. The 1928 study believed that heavy AP shell would start to tumble after about 25 feet under water. Thus the shell would hit the torpedo part of the side protection system at a much reduced velocity at an unknown orientation. This becomes a problem of what happens to a torpedo defence system when a large tumbling mass of metal hits it, and looking at the Bismarck and POW gives examples.
I will rephrase my question. You have stated that under normal circumstances, the KGV system was essentially immune to diving shells which were still able to activate their fuze. The shell which hit Bismarck exploded, and therefore the fuze functioned. It passed below her belt. Bismarck was obviously not immune to this type of hit, and I asked whether you felt that if Bismarck posessed the KGV scheme she would not have suffered internal flooding from this hit.

This is an interesting discussion, because if true, it renders the US system unnecessary, as well as that on Yamato and the projected Montana class.

My personal opinion is the the Japanese shells, with their long fuse delay and hydrodynamic design, would be capable of passing under the KGV belt and detonating afterwards.

User avatar
tommy303
Senior Member
Posts: 1528
Joined: Mon Oct 18, 2004 4:19 pm
Location: Arizona
Contact:

Post by tommy303 » Tue Jun 13, 2006 4:37 pm

Tiornu has a good point concerning fragments from the shell nose. Splinter propagation tends to be directional in relation to the position of the fuze since the detonation wave of the filler is direction from nose to base in a point detonating shell and base to nose in a base detonating shell.

My understanding is that with clyndro conoidal projectiles, if one fails to stabilize nose first in water and begins to tumble, it makes one 180 degree turn at which point it will stabilize and continue on its way in a base first attitude--the flat base being more condusive to stable under water or in fluid trajectories than the ogival nose--hence the employment by the Japanese of a flat nosed main piercing cap with detachable upper piercing cap piece and ballistic cap. On Prince of Wales, the crescent shaped mark left by the shell on the torpedo bulkhead seems to indicate a base first impact. The large tearing hole in the shell plating might indicate the shell was still in the process of reorientation when it made contact--possible but unlikely in my opinion considering its apparent low velocity at the time, or it might be indicative of first contact being at an oblique enough angle to cause tearing of the plating instead of a more normal hole being punched through.

Their shoulders held the sky suspended;
They stood and Earth's foundations stay;
What God abandoned these defended;
And saved the sum of things for pay.

phil gollin
Member
Posts: 167
Joined: Mon Oct 18, 2004 6:33 am

Post by phil gollin » Wed Jun 14, 2006 9:30 am

I can't comment on the Bismarck's system versus a 14-inch shell as I don't have enough detail on the path that the shell may have taken and more importantly the time. Also, even an inert lump of steel weighing around a ton can do an awful lot a damage at the residual speeds involved


The US system was essentially looked at by the RN in 1928 and was by no means thought of as "unnecessary". The RN study believed that in pure direct AP shell hit protection terms it was slightly better per equal weight due to the slope of the armour. However, they saw a possible problem with diving shell that hit the water near enough to end up within the ship's structure (inside the hull and torpedo defence system but outside the angled belt) when the exploding shell propelled the armoured cap through a reduced thickness (and for the US but not RN type of armour) of the belt. Either way you are looking at the extremes of behaviour, do you want every little bit of absolute armour resistance or do you want the widest possible protection. The RN made their decision, the US theirs (but changed for the Montanas). I THINK (???) that the RN would also have liked the Montana class system, but would never have been able to build a battleship wide enough to employ it..


Re. Japanese shells, with their long fuse delay and hydrodynamic design, you may well be correct, but one would have to look at the paths and TIMES concerned and look at where in the side defence they would explode. You MAY be taking the chances of a hit from (you choose your own comparators) very unlikely to vaguely possible, but one thing I have always wondered about is these hits seem even more prone to the playing with angles for attacker and defender and that they only seem sensible for battleline versus battleline where the attacking angle is nearer the normal (0 or 90-degrees depending on terminology). The RN intended, IF FREE, to fight at a nominal inclination of about 30 degrees and this wouldincrease underwater paths.

User avatar
nwhdarkwolf
Member
Posts: 55
Joined: Fri Jun 02, 2006 4:42 pm
Location: Appleton, USA

Post by nwhdarkwolf » Wed Jun 14, 2006 1:59 pm

From what I am reading, Phil...Most navies had that thought. 30 degrees seems to be the general thought when it comes to armor.

Bgile
Senior Member
Posts: 3658
Joined: Wed Mar 09, 2005 7:33 pm
Location: Portland, OR, USA

Post by Bgile » Wed Jun 14, 2006 4:35 pm

Hi Phil,

Thanks for your thoughtful response. I was also under the impression that all navies would attempt to achieve an offset angle for incoming shells, but the Japanese knew this and may have designed their fuses accordingly. I don't know. IMO this is why the US used such very thick armor on turret faces - because they would be expected to be facing the enemy directly. IMO those are weak points on the Bismarck and KGV schemes, because they aren't thick enough to stop direct hits from shells which would be deflected by their belt armor.

User avatar
Karl Heidenreich
Senior Member
Posts: 4808
Joined: Thu Jan 12, 2006 3:19 pm
Location: San José, Costa Rica
Contact:

Post by Karl Heidenreich » Wed Jun 14, 2006 6:08 pm

What all this imply in Bismarck´s case? :?:

In previous occasions this discussion has taken place without a conclusion, one way or another.

Was Bismarck main armoured belt too shalow, as seem to be demonstrated by the PoW´s hit amidships or not? In comparison with other contemporary BBs: KGV, Nelson, North Carolina, Richelieu, was it a better concept + design or not? In comparison with the biggest BBs: Iowa and Yamato Class, where Bismarck stands?
My sincere opinion to this date, not a very technical one I must admit, is that Bismarck´s armoured belt let the PoW 14" live shell get inside important comparments of the ship... and explode! And that sounds too close to a DESIGN FLAW, even for me: a Bismarck unconditional fan! That stands because other BBs, KGV and Richelieu included, had a deeper belt that protect their interior from "live" AP shells.
Is that it?
:?:
An appeaser is one who feeds a crocodile, hoping it will eat him last.
Sir Winston Churchill

phil gollin
Member
Posts: 167
Joined: Mon Oct 18, 2004 6:33 am

Post by phil gollin » Wed Jun 14, 2006 10:55 pm

Bgile wrote:Hi Phil,

Thanks for your thoughtful response. I was also under the impression that all navies would attempt to achieve an offset angle for incoming shells, but the Japanese knew this and may have designed their fuses accordingly. I don't know. IMO this is why the US used such very thick armor on turret faces - because they would be expected to be facing the enemy directly. IMO those are weak points on the Bismarck and KGV schemes, because they aren't thick enough to stop direct hits from shells which would be deflected by their belt armor.
I must admit I do not understand the choices the Japanese made, but I don't pretend to have looked at them in detail. The choice of fuze delay seems a choice of the lesser of many evils. All I can say is that the RN chose their delay based on the expectation of penetrating the thick belt armour and travelling into the vitals.

As far as US fast battleship turret fronts versus KGV turret fronts there are lots of immutables :

USN thick but homogeneous armour whereas KGV is face-hardened (cemented).

It looks like the KGV barrel slots are bigger but don't know for sure.

The USN turrets are angled back the wrong way.

So I couldn't really say, other than I doubt it would be likely for any turret to be in a very good condition after being hit straight on by a large calibre AP shell.

Tiornu
Supporter
Posts: 1222
Joined: Mon Oct 25, 2004 6:13 am
Location: Ex Utero

Post by Tiornu » Wed Jun 14, 2006 11:43 pm

The Japanese Type 88 of 1931 had a delay of 0.2 seconds, probably about 5x as long as the delay in foreign AP shells. Then the Type 91 shell, which was the standard WWII type, upped the delay to 0.4 seconds, which seems insanely long.
The striking velocity of a shell is at a minimum when the descent angle is about 35deg. The faceplates of the US fast battleships were angled back at about 35deg. It's possible that this is coincidence, but it looks like the US faceplates were hit most directly when shells were at their least penetrative.
Tests conducted post-WWI on old US battleships were used to simulate 14in hits at extremely close range. I'm not sure what the angle was on those plates, but it was probably near that of the later ships. That means the impact would be near 30-35deg for these tests. The damage was slight. Some splinter plating around the gunports was deformed enough to jam the elevation, so that feature was omitted from other ships.

Bgile
Senior Member
Posts: 3658
Joined: Wed Mar 09, 2005 7:33 pm
Location: Portland, OR, USA

Post by Bgile » Wed Jun 14, 2006 11:52 pm

I see the faceplate angle in a somewhat different way. This is my opinion:

British faceplates were vertical, which meant that the flatter the trajectory of the incoming shell, the closer to the normal it was going to hit the armor. In other words, at velocities likely to achieve penetration of the armor, there was less deflection. Also, if the shell was deflected, it would be deflected down into the ship.

The US faceplates were angled fairly sharply, which means that higher velocity impacts were more likely to hit at an angle. As the trajectory increased and impact velocity dropped, the angle approached the normal, when it wasn’t likely to penetrate 17” of homogeneous armor anyway because of it’s lower velocity.

The U.S. had trouble making really good facehardened armor early on in really thick plates. Years later, when they were capable of doing so, they decided not to because tests had confirmed that the new 2700 lb AP shell wasn’t likely to shatter even against modern face hardened armor, so face hardening was largely irrelevant.

I suspect the vertical plates in the British and German ships were to facilitate the piercings necessary for their sights. In the US and Japanese case the sights were in periscopes on the side of the turret.

Please note that even though the armor of the turrets used in the Vanguard had to be replaced, they didn’t use vertical plates.

Your point regarding turrets being damaged by any heavy caliber hit is well taken, and we have few examples to work with. I can only say that heavy armor was provided to make it possible to survive such a hit, and if they didn't think it possible they'd have only armored them against cruiser fire.

Tiornu
Supporter
Posts: 1222
Joined: Mon Oct 25, 2004 6:13 am
Location: Ex Utero

Post by Tiornu » Thu Jun 15, 2006 3:10 am

The larger gun port is a inescapable result of the more vertical faceplates. For mounts with only low elevation, it might not make much of a difference. For a gun with 45deg elevation, I wonder if the smallest gunport would be for a faceplate mounted at 22.5deg.

User avatar
nwhdarkwolf
Member
Posts: 55
Joined: Fri Jun 02, 2006 4:42 pm
Location: Appleton, USA

Post by nwhdarkwolf » Thu Jun 15, 2006 12:57 pm

Tiornu wrote:The larger gun port is a inescapable result of the more vertical faceplates. For mounts with only low elevation, it might not make much of a difference. For a gun with 45deg elevation, I wonder if the smallest gunport would be for a faceplate mounted at 22.5deg.
That, certainly, makes sense to me. You might be able to get away with less.

I'm not convinced that the US face angle was wrong, does anyone have any proof of this?

Most hits on Battleships weren't on the faceplates of turrets, even though most of the turrets were armored as such. I'm in the process of reading Whitney's Encyclopedia on WWII Battleships. Even though I am only 1/4 of the way through, he does mention faceplate armor being very thick, but I have yet to see a hit of this type.

Post Reply