SMS MarkGraf V USS Texas.

[Bgile]

When I said WV's situation might be worse than Shinano's, I was thinking she was the one with all her watertight doors and hatches clipped open for inspection, and of course much of her crew was ashore as with all the others.

Have I mistaken her for another ship? They sometimes run together in my mind.

[Tiornu]

You may be thinking of California. She sank after progressive flooding from just two torpedoes.

[paul mercer]

If the danger from torpedoes was a known factor with the later build battleships, why did they not increase the amount of protection - or could no amount of armour really protect the underside of a ship?

[Tiornu]

The modern battleships had better torpedo protection, but there was no way to provide protection proportional to the increase in torpedo destructiveness.

[paul mercer]

The modern battleships had better torpedo protection, but there was no way to provide protection proportional to the increase in torpedo destructiveness.

Thanks Tiornu,
Could you say why?
There have been many debates on this site about shell v armour, with the general conclusion seeming to be that the armour won i.e. the last WW2 Battleships being almost unsinkable through shelling alone, even with the latest type of shell.
Is it because the torpedo explosion is enhanced through being underwater but next to the hull in a similar war that the Dambusters bomb was dropped so that it would roll down the side of the dam?

[Tiornu]

The best of the old battleships had a TDS about 18ft deep. The new ships didn't have much more hull volume for deeper systems, but they did refine the details of liquid loading and such. The advance was modest. In contrast, a powerful WWI torpedo might have, what, 500 lbs of TNT? By the end of WWII, there were torpedoes in service with the equivalent of a 1800-lb TNT charge. Destructiveness is not exactly proportional to the warhead weight, but you can see that torpedoes were advancing far faster than protection could.

[paul mercer]

Thanks again!
Out of interest, what amount of explosive would be in 14/15/16" shells?

[RF]

About one ton I believe.

[Tiornu]

US AP shells were about 1.5% explosive. British AP shells were about 2.5%.

[Bgile]

US 16" AP = about 40 lbs of explosive.

US 16" HE = about 150 lbs.

US Mk 14 torpedo = about 660 lb TORPEX.

[paul mercer]

US 16" AP = about 40 lbs of explosive.

US 16" HE = about 150 lbs.

US Mk 14 torpedo = about 660 lb TORPEX.

Wow, I'm not surprised that a torpedo knocks a big hole in the bottom! Presumably the ones carried by aircraft were a lot smaller, I understand that the one that hit Bismarck on the side hardly dented the armour and that the two Japanese superships absorbed quite a few on both sides before sinking.
Out of interest, when they were attacked was it was the torpedoes that did the real damage rather than bombs which presumably would make a mess of the upperworks but not penetrate the armoured deck to any extent?

[Tiornu]

Early-war aerial torpedoes had charges weighing about 400 lbs, give or take. Late-war models were generally in the 600-lb neighborhood.
Torpedoes are not designed to defeat armor, so the fact that Bismarck's belt was only slightly displaced by a 388-lb charge is no surprise.
Musashi took twenty torpedo hits and sank only after a prolonged battle. Yamato took thirteen hits and sank rather quickly. The difference is that in the second instance, the airmen specifically planned to put their torpedoes all in the same side of the ship.
A 1000-lb bomb could cause significant damage if placed in the right spot. One hit was able to send hot splinters into Yamato's aft 155mm hoist tube which caused a dreadful fire. You can see it in pictures, truly a frightening sight with flames blasting out from the magazines. This fire was not quenched until the ship sank. It may have been possible only because a previous bomber had scored a truly damaging hit--wiping out the entire aft DC team.

[paul mercer]

Thanks yet again Tiornu.
What puzzles me is that if a 1000lb bomb could penetrate and cause so much damage to what was probably the most heavily armoured ship ever built, how come there have been so much discussion in other threads about the penetration and damage capabilities (or rather lack of them in some cases) of shells weighing up to or more than twice that weight?
Also, where can I view the pictures you referred to?

[tommy303]

Hi Paul,

A shell from a naval rifle will always be coming in at a relatively oblique angle to a ship's deck armour, even at long range where its final trajectory will be steep; an armour piercing bomb, on the other hand, being dropped from above, will have a much more favorable impact angle and will usually strike the decks at very close to normal impact angle (much closer to a right angle impact). The closer a shell or bomb comes to hitting the armour square on the better, and in most situations the bomb will have the decided advantage provided it is dropped from optimal height so it both stabilizes and reaches its terminal velocity.

[Bgile]

Tommy,

I was under the impression that bombs dropped by dive bombers were always too low to reach terminal velocity. Is that correct, or am I in error?

Bombs dropped by high altitude bombers almost always miss because the ship has lots of time to move, and the bombs are less accurate in any case.

My understanding is that the torpedo which hit Bismarck amidships was a surface runner which failed to run at a depth which would do significant damage, unlike the one which hit aft.