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Bomb Damage Question


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#1 Joe McCabe

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Posted 21 September 2008 - 11:51 AM

I have a query regarding bomb damage to ships -If armor penetration is required and the bomb is not large enough the hull damage is to be halved.However, what should apply if the hull damage listed on the bomb table is only half a hull box already - this would be halved to a quarter. Quarter boxes are not recorded so should it be rounded up to a half again or disregarded totally.I ask because the max penetration for a Heavy bomb is BC armor - so any BB, BA, BA+ would always receive half hull hits. If dmage is rounded down then bombing is totally ineffective against them and I don't think this is the intention.ThanksJoe

#2 Dave Franklin

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Posted 24 September 2008 - 02:36 PM

An interesting question, though looking at the Bomb Damage Table (from Amendment 1), only BA+ would be totally exempt. You could still net a half hull box against BA on a 2-9, for example.The special rule for the FX-1400 (Frtiz-X) allows it to penetrate BA armor, so you can duplicate history and sink RN Roma.However, I'm not sure how one duplicates sinking USS Arizona. Her sister USS Pennsylvania is in the Operation Landcrab file, and has BA hull armor. A Bomb Type H cannot penetrate BA armor, so you can't get an Ammunition Critical Hit. Even more difficult since the B5N Kate is only listed as carrying an M type bomb...

#3 DAVID THORNLEY

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Posted 25 September 2008 - 02:25 AM

You'd have to sink USS Arizona with a special rule. The bomb that was dropped was a somewhat modified battleship-caliber AP shell, and was able to penetrate thick deck armor. The Pearl Harbor strike used ordnance tailored to the situation. The aerial torpedoes were slightly modified to stay shallow, for another example.If you're going to run a Pearl Harbor scenario, make up some rule for the first wave of Kate level bombers. Their bombs would penetrate a lot better, but would have less actual explosive. (Speaking very roughly, an AP shell would have about 2-3% explosive by weight, and an AP bomb would be more like 10% or so - maybe more, I'm not remembering right now.)

#4 Cpt M

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Posted 25 September 2008 - 06:49 PM

I ask because the max penetration for a Heavy bomb is BC armor - so any BB, BA, BA+ would always receive half hull hits. If dmage is rounded down then bombing is totally ineffective against them and I don't think this is the intention.

As co diver correctly pointed out, under the Amendment 1 table, the only ship armor that would be immune to hull damage by a Heavy bomb would be BA+ (and the only ships with that class of hull armor is Yamato and Musashi). Of course, all their non-armored systems (secondaries and non-armored critical hit areas such as the bridge) would still be open to damage as well as any hull hits caused by near misses (armor penetration is not required for a hull hit caused by a near miss).

However, I'm not sure how one duplicates sinking USS Arizona. Her sister USS Pennsylvania is in the Operation Landcrab file, and has BA hull armor. A Bomb Type H cannot penetrate BA armor, so you can't get an Ammunition Critical Hit. Even more difficult since the B5N Kate is only listed as carrying an M type bomb...

True enough, but as Thornley mentioned, the bombs used at Pearl Harbor were specially modified AP shells with a much better armor penetration than a normal bomb. Such a situation would need a scenario specific rule such as a higher penetration with the effects of a smaller bomb.

#5 Joe McCabe

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Posted 26 September 2008 - 12:53 PM

So the quick answer to my initial question is that hull hits are halved and ROUNDED DOWN. Meaning as you say, that Yamato and Musashi can suffer no hull box losses from bombs - better make sure TBs are included in any strike against them !

#6 Cpt M

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Posted 26 September 2008 - 02:27 PM

So the quick answer to my initial question is that hull hits are halved and ROUNDED DOWN. Meaning as you say, that Yamato and Musashi can suffer no hull box losses from bombs - better make sure TBs are included in any strike against them !

Correct on both points!

#7 Dave Franklin

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Posted 02 October 2008 - 02:28 PM

Been doing a little more investigation, and wonder if 1000lb "H" class bombs are being shorted a little in their armor penetration. The following are excerpts from the TROMs for Yamato and Musashi on the Nihon Kaigun site (http://www.combinedfleet.com/):Yamato:24 October 1944: ...1350: A Curtiss SB2C "Helldiver" dive-bomber from USS ESSEX (CV-9) drops two AP bombs that damage the port bow abreast of main gun turret No. 1.1430: Attacked by four Grumman F6F "Hellcat" fighters and 12 SB2C dive-bombers. They drop five 1000-lb AP and seven AP bombs. The first bomb penetrates the anchor deck, demolishes the port chain locker, explodes below the waterline, blows out a side plate and holes the bow. The mess deck is wrecked. Two bombs hit turret No. 1. One blows a hole above the waterline. Another bomb penetrates through the top deck to the crews' quarters.YAMATO ships 3, 000 tons of seawater and takes on a five-degree list to port. Damage Control counterfloods and reduces the list to one degree. YAMATO is down by the bow and maintains a 2-ft, 8-in. bow trim.26 October 1944:0834: The Force is attacked by about 50 Curtiss SB2C Helldivers and Avenger torpedo planes from USS HORNET (CV-12). Two bombs hit YAMATO. The first penetrates the forecastle forward and to the right of the main breakwater, demolishing nearby crew's spaces. The second bomb causes slight damage to the side of main gun turret No. 1. 7 April 1945:1240: YAMATO is hit by two AP bombs. Smoke rises from the vicinity of the mainmast and a bomb explodes in the same area. The aft secondary battery fire control, secondary gun turret and the air search radar are knocked out. The Attack Force changes course to 100 degrees. Helldivers from BENNINGTON and HORNET attack from port. At flank speed, YAMATO commences a right turn but two 1000-lb AP bombs hit her. The first explodes in the crew's quarters abaft the Type 13 radar shack. The second penetrates the port side of the aft Command station and explodes between the 155-mm gun magazine and main gun turret No. 3's upper powder magazine. It starts a fire that cannot be extinguished and rips a 60-foot hole in the weather deck. One Helldiver is shot down, another is damaged badly.Musashi, all 24 October 1944:1203: Enemy planes are sighted. A second attack by eight Helldivers from INTREPID scores two bomb hits and five near-misses. A dud penetrates two upper decks, demolishes the crew's head and exits above the waterline. A second bomb strikes portside ahead of 127-mm AA gun No. 4, penetrates two upper decks and explodes on the middle deck in crew space No. 10. Fragments rupture a steam pipe in engine room No. 2 directly below. This engine room and the adjacent boiler room No. 10 fill quickly with superheated steam and are abandoned. The damage results in the loss of the port inboard shaft. MUSASHI's speed falls off to 22 knots. Two Helldivers are shot down.1515: Nine of ENTERPRISE's SB2C Helldivers score four 1,000-lb AP bomb hits. The first three strike in the port bow area and cause damage below decks. The entire forward damage control team is annihilated. The fourth bomb wrecks the Chief Steward's office.=========================================Several of these instances might be explained by hits forward of the armored "citadel" in the "all of nothing" scheme, but then that just means the vessel shouldn't be rated BA+ everywhere. One could argue the "Fire" result that is possible on the (Amendment 1) Campaign Air Ops Bomb Damage Table (on the roll of a "1") does allow the posibility of hull damage to a BA+ ship, but that is the only chance (and note it is not possible on the Tactical Air Ops Bomb Damage Table).

#8 Cpt M

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Posted 02 October 2008 - 02:57 PM

Been doing a little more investigation, and wonder if 1000lb "H" class bombs are being shorted a little in their armor penetration.

Well, most of the instances you mentioned are, as you pointed out, outside the main armored citadel. And much of the damage mentioned would not, in GQ3 terms, be modedled as it doesn't threaten the survival of the ship itself (no damage that leads to flooding, fires or the loss of major systems). Full armor peneteration constitutes penetrating the citadel itself, causing severe damage to such systems as engineering and the very structure of the ship, thereby threatening the ship's very survival. (In point of fact, according to a review of post action damage reports, some of the most damaging hits a ship can endure are the close aboard near misses that cause flooding.)

#9 Lonnie Gill

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Posted 02 October 2008 - 07:53 PM

Good dialog on an interesting question Joe raised.The BOMB DAMAGE table reflects that 1000 pound and smaller bombs were effective at destroying the superstructure, secondary and AA batteries of battleships (BB, BA and BA +) but were unlikely to cause major structural damage to these heavily armored targets. The hull damage listed on the table represents significant flooding rather than any/all hull damage. Thus halving the damage from bomb hits that fail to penetrate the heavy deck armor of these ships reflects that flooding may result, but it is less likely to significantly affect the stability or floatation of these targets, which were large enough to have anti-torpedo bulges/defenses and had significant counter flooding and pump damage control capacity.In the interest of streamlining the pace of the basic simulation, halving a “˝ Hull Box “ hit is not significant damage recorded on the target’s Ship Log. For those who want more detail in bomb damage simulation, I would recommend rolling an additional D12 for the halved “˝ Hull Box “ hit: ODD = ˝ Hull • EVEN = no significant damage. This is similar to the gunnery process you are familiar for finalizing an attack that results in a net ˝ equivalent damage roll.Hopefully, you and other gamers will try this suggestion in your scenarios and let us know if you find it effective. If it proves successful after play testing, we will make it an optional rule as we continue to evolve GENERAL QUARTERS together.A further note; Rule Section 2.10.5 also indicates that the damage from a “Near Miss” is not halved as penetration is not required.Finally as noted, the hit on Arizona at Pearl Harbor was made by specially modified AP shell much heavier than the 1000 pound bomb (classified as H) and smaller bombs listed on the table. Pre war, aviators in all navies were aware that the 1000 pound or smaller bombs carried by dive bombers and most medium and heavy bombers would probably not penetrate a modern battleship’s heavily armored deck. Accordingly, the torpedo bombers of the USN and IJN, in particular, were equipped with bombsights and a third crew bombardier position for level bombing with approx. 1700 pound bombs to be dropped from a high enough altitude for gravity to enable penetration. In fact, the famous Norden bombsight started out as a Navy bombsight to fit this requirement.Much of the training time for pre war TB crews was devoted to level bombing. But, it was well recognized that the hit probability against a maneuvering target at sea was abysmally low and the practice was quickly abandoned once the war started. Accordingly, the BOMB DAMAGE table does not include these heavier bombs. Part of the genius of IJN aviation planning was the recognition that Pearl Harbor represented a special, one time circumstance in which stationary battleships would be vulnerable to this type of attack using specially converted AP shells to ensure penetration.Thus, simulating an attack of this type with heavier bombs than listed on the BOMB DAMAGE table would require an optional rule reflecting greater penetration and damage. Anyone want to take a shot at an optional rule for this circumstance?LONNIE

#10 Dave Franklin

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Posted 03 October 2008 - 08:56 AM

I guess I think "YAMATO ships 3,000 tons of seawater and takes on a five-degree list to port" might be enough to count half a hull box. It would take a second such hit to reduce her top speed by 3 knots in GQ3 terms.Also, for Musashi, "Fragments rupture a steam pipe in engine room No. 2 directly below. This engine room and the adjacent boiler room No. 10 fill quickly with superheated steam and are abandoned. The damage results in the loss of the port inboard shaft. MUSASHI's speed falls off to 22 knots." sounds pretty close to an Engineering critical to me.The comments about near misses is irrelevant since there is no hull damage for near misses for BA or BA+.I like the idea of Lonnie's of rolling for halving 1/2 hull hits, as it still leaves the possibility for them, and is consistent with the Gunnery mechanics.Regarding Arizona, I would treat the special bomb (a converted 16" shell) as a 16" plunging shell hit. It would penetrate BA armor, and do 1 equivalent hit vs BA.Lastly, did you notice my comment about the difference between the two Bomb Damage Tables? Is there a reason they are different, or is it an error? On the original tables, neither one had the possibility of a Fire against BA/BA+.

#11 Jim O'Neil

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Posted 03 October 2008 - 03:13 PM

Very obviously the two cases above are penetration of the armored box, as likely was the "landed between the 155 mm magazine and the 18" magazine and started a large fire that could not be put out". I do think the 50-50 chance of a half of a damage box is appropriate. Fire and or flooding seem likely outcomes.

#12 Lonnie Gill

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Posted 09 October 2008 - 05:51 PM

Co_diver,Looks like a gotcha'; I must have missed updating those final two cells on the Tactical Air Ops chart. The intent was to make the Bomb Damage table the same on both charts - as shown on the Camapign Air Ops chart. I'll be out of action for a few days with minor surgery, but when I get going again, we'll post a fix for you to download. Cheers,LONNIE

#13 CinC

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Posted 14 October 2008 - 04:51 PM

The fix has been posted to the Amendment 1 folder.CinC




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