Effect of bombs

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paul.mercer
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Effect of bombs

Post by paul.mercer » Mon Apr 18, 2011 8:41 pm

Gentlemen,
We have discussed the effect of shells and torpedoes on capital ships such as Bismarck, but what about bombs? If we ignore the 6 tonners dropped on Tirpitz and the guided bomb that hit Warspite what effect would the average bomb dropped either from a carrier or land based aircraft have on a heavily armoured battleship - besides making a bit of a mess of her upperworks? I have always thought that the sinking of Yamoto & Mushashi was the direct effect of multiple torpedo hits, so would the bombs just bounced off them and other modern ships?

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Re: Effect of bombs

Post by Bgile » Mon Apr 18, 2011 11:56 pm

The bombs don't "bounce off". They can do tremendous structural damage, destroy secondary battery and AA weapons and cause heavy crew casualties, making the ship vulnerable to attack by destroyers and torpedo carrying aircraft. Additionally, near misses by heavy bombs can cause flooding in the TDS, reducing it's protective value. Finally, direct hits to bow and stern areas can cause flooding and reduce the ship's speed, as well as sometimes making fuel stored there inaccessible.

A bomb on Yamato destroyed the aft 6.1" turret and started a fire they were never able to put out. If a fire is bad enough, it can spread to the citadel area.

Bombs can destroy intakes and uptakes to the powerplant, reducing it's efficiency and sometimes even force the abandonment of machinery spaces. This effects power to all parts of the ship, including speed.

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Re: Effect of bombs

Post by Keith Enge » Tue Apr 19, 2011 2:52 am

While generally I agree with bgile, I wouldn't have used the term "tremendous structural damage". To do this, the bombs would have to penetrate better than the commonly used bomb sizes, types, and drop heights typically did. Also, trying for penetrating hits and damaging near misses was basically an either-or proposition. One required AP (armor piercing) bombs while the other required large GP (general purpose) bombs. Near misses by AP bombs generally had little effect; even if the impact with the water did set off their fuse, the burster of an AP bomb was too small to have the desired effect. Even GP bombs didn't have the optimal submerged explosion effect like a torpedo; GP bombs exploded at the surface and so wasted too much of their force up into the open air. The British tried to make a bomb type (B bombs) to get the desired effect. These bombs had a floatation chamber and a delay fuse; they were designed to miss the ship, sink down with their momentum, and finally rise back up before exploding with the desired "water hammer" effect. Unfortunately, they could never get the design right and very few were used operationally.

As for the effect of non-penetrating bombs, their danger was shrapnel. A battleship, however, tended to have adequate splinter protection to protect everything remotely vital. These things needed only splinter protection because they were relatively so small as to be unlikely to be hit (and redundant so even the remote chance of a direct hit wasn't devastating, there were others still left). One aspect of splinter protection wasn't, at times in some navies, properly considered. Since the bomb didn't penetrate, the shrapnel couldn't go down so flew up and out. Therefore, it was important to put splinter protection not only on the sides of things but the bottoms too. Thus, things like AA mounts and directors needed their undersides armored as well as the side bulwarks.

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Re: Effect of bombs

Post by frontkampfer » Tue Apr 19, 2011 3:57 am

I agree with Bgile. My Father was an FC in the USN and he said a near miss from a bomb could be almost as damaging as a hit as far as the hull of the target was concerned. My 2 cents!
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Re: Effect of bombs

Post by Bgile » Tue Apr 19, 2011 6:58 am

I wonder what the burster of a 1,600 lb SAP bomb is. I have no idea, really. I expect those would burst on contact with the main armor deck of a battleship and in the case of Bismarck would penetrate the upper armored deck first, but I really don't know. If it did, I suspect the damage would be substantial.

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Re: Effect of bombs

Post by lwd » Tue Apr 19, 2011 2:21 pm

The effects of two AP bombs on WV are mentioned here: http://www.usswestvirginia.org/stories/story.php?id=16
My ship had been hit with five 18” aircraft torpedoes on her port side, and two 15” armor-piercing bombs. The first bomb penetrated the superstructure deck, wrecking the port casemates and causing the deck to collapse to the level of the galley deck below. Four casemates and the galley caught fire immediately with the subsequent detonation of the ready-service projectiles stowed in the casemates. The second bomb hit further aft, wrecking one OS2U floatplane atop the “high” catapult on the 16” turret C and pitched the second one over onto the poop deck below. It then penetrated a 5-inch turret roof, wrecking one 105-ton gun inside the turret itself. Although the bomb proved a dud, burning gasoline from the damaged aircraft caused a lot of damage.
Here's a page with stats for Japanese WWII bombs http://en.wikipedia.org/wiki/List_of_Ja ... navy_bombs
This one has what I think are US bombs but the site isn't working right for me: http://www.globalsecurity.org/military/ ... bs-ww2.htm
Some period info at: http://www.eugeneleeslover.com/ENGINEER ... html#part1

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Re: Effect of bombs

Post by Keith Enge » Tue Apr 19, 2011 6:14 pm

bgile, as a general rule, the percentage by weight of burster explosive is fairly uniform across the various navies. The reason for this is the relative weight of steel versus explosive. Thus, a hollow shell of thin steel filled with explosive still has a weight of 40% steel and 60% explosive even though the explosive is almost all of the volume. An SAP bomb is 30% explosive; an AP bomb is 15%. Therefore, in answer to your specific question, the 1600 lb SAP bomb should have 480 lbs of explosive. However, as far as I know, there was no US 1600 lb SAP bomb. There was an AP bomb of that weight. Actually, although nominally 1600 lbs, it weighed 1590 lbs with a 215 lb burster or 13.5% explosive which close to the expected 15% for an AP bomb. The US Navy didn't favor SAP bombs; they felt that they had few advantages. An SAP bomb didn't provide the penetration of an AP nor the "water hammer" effect of a GP near miss.

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Re: Effect of bombs

Post by Bgile » Tue Apr 19, 2011 8:14 pm

Thank you for the clarification. I'd seen that 1,600 lb bomb listed as both SAP and AP but it makes more sense as an AP bomb. The explosive weight seems consistent with that of a 500 lb GP bomb, and I don't think that is necessarily inconsequential in the water alonside a ship. Not like a torpedo of course, but still of consequence.

However, you said a GP bomb would explode on impact with the surface and not produce any mining effect; merely shrapnel which would largely be stopped by a battleship's protection. This explains my interest in an SAP bomb which would presumably have a small fuse delay.

Now you are saying a GP bomb would have a greater mining effect. This seems inconsistent to me. I do know that GP bombs did have a significant mining effect in some actual cases, which would imply that they didn't necessarily explode on contact with the surface. It's a conundrum, because if you give a GP bomb a fuse delay and the bomb hits armor it may break up before the fuse has a chance to explode it. On the other hand, it would do much more damage with a fuse delay if it hit water near a ship or relatively thin structure on the ship.

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Re: Effect of bombs

Post by paul.mercer » Tue Apr 19, 2011 8:21 pm

Gentlemen,
Many thanks for your replies. Previously I had always imagined that the average carrier aircraft could not carry a bomb heavy enough or high enough for it to penetrate a Battleship's armoured deck.
As a matter of interest just how hard would it be to hit a moving (and presumably zigzaging) ship, I wonder if Yamoto & Musashi were slowed down by torpedoes first?

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Re: Effect of bombs

Post by Bgile » Tue Apr 19, 2011 9:21 pm

Akagi, Kaga, Soryu, and especially Hiryu were undoubtedly maneuverning at high speed when they received fatal bomb hits from dive bombers. I suspect Yamato was also hit one or more times while maneuvering at high speed, but I don't know. From the prior examples, it was possible. High speed maneuvering ships are undoubtedly harder to bomb than slow ones.

edit: I believe there is at least one phot of Yamato being hit by a bomb while exhibiting a substantial wake, signifying high speed.

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Re: Effect of bombs

Post by RF » Wed Apr 20, 2011 8:09 am

Presumably dive bombers will obtain best results on a fast moving target, as they aim straight at it, whereas high level bombing would almost certainly miss. This I believe was experienced on HMS Illustrious in the Med in 1940 and 1941; the Italians tried to bomb at high level and missed, the stukas made the first serious (so far as the RN was concerned) assault on the carrier.
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Re: Effect of bombs

Post by lwd » Wed Apr 20, 2011 12:56 pm

Bgile wrote:Akagi, Kaga, Soryu, and especially Hiryu were undoubtedly maneuverning at high speed when they received fatal bomb hits from dive bombers.
From what I recall one or more of them didn't spot the dive bombers until they were entering their dives so they may not have been at high speed unless they were conducting flight ops at the time although they certainly were maneuvering. There are accounts of even smaller craft DDs and Cruisers being hit by bombs while at or near their top speeds and maneuvering to avoid the bombs though.
I suspect Yamato was also hit one or more times while maneuvering at high speed, but I don't know. ....
According to http://en.wikipedia.org/wiki/Japanese_b ... ion_Ten-Go
Yamato avoided being hit for four minutes until, at 12:41, two bombs obliterated two of her triple 25 mm anti-aircraft mounts and blew a hole in the deck. A third bomb then destroyed her radar room and the starboard aft 127 mm mount. At 12:46 another two bombs struck the battleship's port side, one slightly ahead of the aft 155 mm centreline turret and the other right on top of the gun. These caused a great amount of damage to the turret and its magazines; only one man climbed out alive. At 12:45 a single torpedo struck Yamato far forward on her port side ...
That looks like 5 bomb hits before the first torpedo hit and since they had picked up the attack coming in on radar they were very likely at or near top speed.

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Re: Effect of bombs

Post by paul.mercer » Fri Apr 22, 2011 9:35 pm

Gentlemen'
Thanks again for all your replies. What still puzzles me is that huge ships like Yamoto/Musashi were presumably designed to keep out the heaviest shells (some well over a ton) but were severly damaged by bombs weighing a lot less (and presumably coming in a a lesser velocity) than say a 16" from an Iowa class ship.
Perhaps they were only giants of the Battleship world in size and name.

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Re: Effect of bombs

Post by tommy303 » Fri Apr 22, 2011 11:21 pm

Bombs tend to strike horizontal surfaces at near normal angles of impact, whereas shells hit at much more oblique angles. Bombs also tend to have much larger bursting charges.

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Re: Effect of bombs

Post by Byron Angel » Sat Apr 23, 2011 4:37 am

paul.mercer wrote:Gentlemen'
Thanks again for all your replies. What still puzzles me is that huge ships like Yamoto/Musashi were presumably designed to keep out the heaviest shells (some well over a ton) but were severly damaged by bombs weighing a lot less (and presumably coming in a a lesser velocity) than say a 16" from an Iowa class ship.
Perhaps they were only giants of the Battleship world in size and name.
..... Heavy armor of battleships was confined to (hopefully) protecting vital systems - main battery, propulsion, steering. Many areas and substantial volumes aboard even the heaviest battleships were protected to a substantially lesser degree than their vitals, or to no particular degree at all in the case of light and medium AAA, sensor arrays, superstructure, etc.

B

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