Few naval battles were as lop-sided as the Battle off Tamar in WWII. And fewer still are those where the lesser side of the ‘lop’ can claim to have emerged victorious. One of the reasons the US ships survived, or survived as long as they did during the engagement, was because the Japanese armor-piercing shells would often pass right through them without exploding. This occurred when the shells didn’t encounter sufficient armor at/after impact to detonate their fuses. So, paradoxically, the ships’ lack of armor protected them. (As an aside, if the incoming shell managed to hit a reinforced structure such as a heavy support beam or the iron housing of, say, a propeller shaft, it would detonate; often deep within the ship)
All that said, some of the Taffy III ships did have at least 3/4" armor. And, even in the absence of armor, the ships’ hulls and much of the rest of their basic construction was of steel.
So, my questions:
Especially with respect to technologies available at the time:
how did the fuses work such that they would ‘ignore’ simple steel walls, bulkheads, and thin armor, yet be detonated by more substantial resistance? What mechanism enabled the fuses to ‘distinguish’ between the various hard sites they might strike?
generally (and again keeping in mind the ca. WWII technology) how did one get a delay on the order of milliseconds (in order to explode inside the target and not on its surface)?
As to the armor piercing: the shells, themselves were “armored” in that their noses were built of heavier construction to allow them to penetrate other armor. The fuse was set back against the explosive and if there was not sufficient resistance that would crush the nose of the shell, the fuse would be untouched.
(The weight of the nose was sufficient that an Armor Piercing 16" shell only carried 1,600 lbs. of explosives while a High Explosive 16" shell carried about 2,000 lbs. of explosive.)
ETA: 3/4" of armor was really nothing to an AP shell from a heavy gun. They were designed to penetrate several inches of hardened steel.
Regarding the 3/4" armor, this link to a comparison of battleships across multiple navies shows armor on every ship selected thicker than 12". 3/4" armor was intended to stop 20mm cannon fire from strafing aircraft and splinters from nearby explosion, not actual cannon fire. Even tanks were carrying armor more than 2" thick by that point in the war.
Excellent! Very neat - a low tech solution; simple, elegant, and reliable. Thanks.
Clearly, 3/4" armor is negligible compared to what’s found on, say, a battleship. My intuition (which was clearly mistaken) was that even 3/4" steel would provide enough resistance to detonate armor-piercing shells. But, with the mechanism you’ve described, it now seems intuitively to be the case that 3/4" could well be inadequate!
Just to note 3/4" armor was the maximum belt armor on the destroyers, deck armor was 1/2" over machinery sections and 0" on the rest of the deck.
To nitpick, the Battle of Tassafaronga can really give the Battle off of Samar a run for the money in terms of lop-sided odds and a lop-sided victory for the weaker force. A Tokyo Express run of 8 destroyers, 6 of them loaded with supply drums under the command of Tanaka bringing supplies down to Guadalcanal was intercepted at night by a USN force of 4 heavy and 1 light cruisers and 4 destroyers which took the Japanese by surprise. The Japanese reacted swiftly by having the column reverse course 180 degrees and launch torpedoes. Only one Japanese destroyer was lost, while the heavy cruiser Northampton was sunk and all of the other 3 heavy cruisers were severely damaged; two of them having their bows blown off. The extent of the damage is clear in post action pictures of them; USS Minneapolis, USS New Orleans and USS Pensacola.
To the OP IIRC it was deceleration which set the fuse of. A near 3000 ib shell fired at Mach 3 is not going to suffer much deceleration from hitting the thin skin of a destroyer, but it will suffer the a huge amount from the foot plus of armour on a battleship. The mechanism varied, some had a vial of acid which broke at a specific deceleration, others saw a pin released.
Ideally you wanted the shell to explode when it had pierced the armour, causing general distress inside the ship, killing sailors, wrecking machinery, setting off British powder magazines etc. The biggest problem was actually getting the rounds to NOT explode until they had achieved the desired penetration. At Jutland, British rounds tended to detonate on impact against German ship, one of the reasons that the Germans were able to absorb such brutal amounts of punishments.
Thanks! But I was hoping for something a bit more detailed.
I looked through the fuze section (actually, I looked through almost the entire document) and am starting to get a better sense of how the fuzes work, especially those of the pre-electronics era. In fact, your earlier link on “How Shell Fuzes Work” (post #9) also went over it (although I found the style of writing therein not quite what I might have expected :D).
The bottom line seems to be that for shells of that era and type, there were delays on the order of milliseconds (6 to 13) which were set into action by (as AK84 also points out) by the shell’s deceleration (or, phrased differently, by the continued forward movement of the firing pin which allowed it to plow into the primer which then, in turn, ignited a bit of black powder aft of the primer). What I am having a hard time believing is that millisecond precision could be achieved by the chemical process of burning black powder, especially when the entire apparatus had just experienced the monumental shock of being slammed into armor at some 2000 mph! At best, I would have expected something critical to have been jiggled loose by the impact thus making it a bit of a miracle that it still fired, and an absolutely huge miracle that the powder so ignited still burned for the precise number of milliseconds originally intended!
(BTW, as a complete aside, the large Navy gun link above also helped resolve a question I had asked here a few weeks ago about naval shells containing spotting dye. In fact, on page 3-29 of that document, figure 3-34 shows how the dye was placed. One sees there that the arrangement would have been unlikely to significantly alter the ballistics of the shell. See? I told you I looked through the entire document.)
Thanks! I really do appreciate all the help everyone’s provided.
The 16" AP projectile has only 40.9 lb of explosive. (Explosive D, yellow D, etc.). This is out of a total weight of 2700 lb for the Mk 8 projectile. The Mk 13 and 14 HC (high capacity) shells weighed 1900 lb with an explosive weight of 153.6 lb. Pretty surprising how little an explosive charge.
The delay comes from the design of the fuze and the fact that it’s installed in the base of the projectile.
Most of what you need to know about US 16" guns and shells is at:
Note that this site has a picture that debunks any claim that a battleship broadside moves the ship sideways.
I understand and don’t disagree. Still, in one of the pages at smithsb’s link above, the statement is made that for the US Navy at least, the fuse of armor piercing shells would activate so long as the shell encountered (at 0 degrees obliquity) just one inch of armor plating (cited part is about 15% deep in the linked page, under section entitled, “Fuzes”).
Durin the Falklands War, many bombs fro Argentinian A-4s would pass through ships without going off because the fuse hadn’t been activated due to the short time the werr “flying”. I can guess a similar thing happened.
