Dec.7'41: A Day That Nobody Bombed Panama !

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phylo_roadking
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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#451

Post by phylo_roadking » 27 Feb 2009, 22:22

Certainly I have demonstrated with sources that the highest levels of the US military and civilain command structures, up to and including the American Secretary of War , were indeed greatly worried about the destructive abilities of bomb attack against the Gatun Dam.
No, you have demonstrated with ONE (1) source that they were worried about a carrier air group-sized attack i.e. several DOZEN aircraft minimum.
and probably the President that he reported it to
Don't make statements like that without proving them. Sec. Of State for War Stimson probably had QUITE a lot of responsibility for and within his own Department :wink:
One inspecting expert reported that there were three Gatun Dam points that could be diabled with but a single bomb hit which would take the Canal "offline".
You keep mentioning this visiting expert but have NEVER provided ANYTHING about him/her/them or a link to their so-far fictional report.

And the "one bomb" scenario you're talking about was the Fleet Problem where ONE simulated hit on the dam was seemn to count as a penetration of the Canal Zone defences, not the destruction of the Dam.
I've never understood why you gents all seem to feel this question to be so important.
Becuase, AS you've been frequently told...

1/ anyone hearing or seeing aircraft in the vicinity of the Galapagos when they're NOT supposed to be there would be A/ concerned they were in trouble and report them, and B/ be concerned that they were in neutral territory unscheduled and report them.

2/ a civil OR military air presence in the islands will increase the chances of the Chitose and/or her aircraft being spotted. BTW - are you proposing the IJN would manage to winch out fuelled and ARMED aircraft without the benefits of [ilights....? :lol:
If you were to examine the photo at https://www.allposters.co.uk/-sp/Soldie ... 92336_.htm that I previously listed you could compare the amount of earth fill installed beside the right hand buttress of the spillway structure, with the 42' width of the spillway gate clearly visible there in the photo. That thickness of grass covered soil is hardly 42' let alone the 300-400 yards that you claim.
Compare it yourself with the top ten feet of damage done to the Sorpe Dam by THREE tons of explosive...
then I think that you would now have a far better appreciation of just how fast rushing water can erode down thru an earthfill dam once the waterproof layer is breached and water flow thru the dam itself begins
Three lots of 800lbs of explosive dropped in three places is NOT going to excavate a channel through which "water flow" will even BEGIN, to further erode after that.
I have very clearly indicated that the 3 Japanese bombs would be deliberately dropped into the soft soil behind that wingwall, not in any attempt to directly or repeatedly hit the narrow top edge of that wingwall
Robert, I think NOW you should PROVE from the extensive material available that what is there IS indeed "soft soil".
How so ? The Gatun Dam is an earthfill structure what has a unreinforced concrete wingwalls installed as part of it's centre concrete spillway.The vast majority of the Gatun Dam is dirt/rubble excavated from other cut areas of the Panama Canal project.
Silly me - up until now I and others have been assuming you'd actually READ how the Dam was constructed. It appears NOT.
It appears to me that each unreinforced concrete wingwall segemt has east and west end concrete pier supports but nothing save the dirt of the dam itself in support between those buried piers
Robert, you've got that @rse-about-face; it's the DAM behing the curtain wall that reinforces it in this instance by absorbing blast and shock.
It appears that there are underground piers within the body of the dam at about the same 45' spacing as is visible in the nearby comcrete spillway structure.
And what do these underground piers DO? Do you think they're there to make a pretty diagram? They're there to reinforce the curtain wall.
Other than several unsourced repetions from you, I have seen no indications anywhere that the Gatun Dam was a "rammed earth" structure rather than just an earthfill dam built with a roughly centred concrete spillway
Robert, either you really are NOT a civil engineer...or you'd know an "earthfill" dam IS a rammed-earth dam; the material forming the Dam is allowed to settle and compact under its own weight when being built. It's the WEIGHT of its own material that rams it. I suggest as I've said above that YOU go and make yourself more aware of the construction techniques used in the Dam's construction before you embarass yourself further.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#452

Post by RichTO90 » 28 Feb 2009, 00:57

phylo_roadking wrote:Three lots of 800lbs of explosive dropped in three places is NOT going to excavate a channel through which "water flow" will even BEGIN, to further erode after that.
Actually there are numerous problems with bombing and each must be solved to make it work.

Fuzing - the Type 80 bomb proposed utilizes either a nose or tail instantenous fuze. A delay fuze would have to be developed. Of course delay fuzes were notoriously unreliable.

Bomb type - the Type 80 is a light case or general purpose bomb. Although noted as being capable of penetrating 400mm of concrete that is highly unlikely. Depending on the strength of concrete LC/GP invariably break up on impact unless dropped within certain low altitude range bands producing either no or a low order detonation. Typically a use 2,000lb GP must be dropped under 5,000 feet and preferably under 1,500 feet if striking 5,000 PSI rated concrete.

Cratering - to produce a useful crater the bomb must penetrate before exploding. But an instantaneous fuzed 2,000-lb GP bomb will penetrate at most about 2 feet of medium hard surface and will produce a crater roughly 21 feet in diameter and 6 feet deep. If a maximum normal delay (0.1 sec) is used it will penetrate 14 feet of medium surface and will produce a 52 foot diameter crater 24 feet deep. You can expect the Japanese bomb with less filling to produce perhaps a 10 to 20 percent smaller effect.

So they have to know that they will be hitting either dirt or concrete, since it affects which type fuzing is practical and which type attack. Given that the profile of the dam was 20 feet above the lake, then maximum delay fuzes have to be used and only soil can be hit and there still is a good chance that even perfectly overlapping strikes will have zero result.

(See US Army Terminal Ballistics Data, Volume I and III, APG, September 1945)


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phylo_roadking
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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#453

Post by phylo_roadking » 28 Feb 2009, 01:08

Cratering - to produce a useful crater the bomb must penetrate before exploding. But an instantaneous fuzed 2,000-lb GP bomb will penetrate at most about 2 feet of medium hard surface and will produce a crater roughly 21 feet in diameter and 6 feet deep
Yes, looking around tonight I'd found reports of craters in EXACTLY these proportions reported from No.80s dropped on Corregidor.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#454

Post by phylo_roadking » 28 Feb 2009, 01:18

And there's the additional and almost insurmountable problem of ALL the bombs needing to be exploded in EXACTLY the same location excavate a hole in the top of the Dam. From those heights precision bombing of THAT degree was not possible from unguided munitions of the period, not without quite a few feet of difference on the ground between craters due to the differences between bombing runs and release points of each aircraft. The advantage of UPKEEP was it would deliver a MUCH larger amount of explosive to within a very few feet a number of times in a row.

Interestingly, the top of the Sorpe Dam at the point of impact was only ten feet across; not the hundreds of yards of Gatun Dam. Damage from the RAF raidS plural DID show up....but not until 1953 IIRC!!! People looking at the Sorpe Raid tend to forget or not know that THIS later damage was actually the cumulative effect of CHASTISE and the TWO later precision Grandslam raids on the Dam..!!! 8O

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#455

Post by Sid Guttridge » 28 Feb 2009, 13:43

Hi David,

There is no Galapagos airfields issue to put on a separate thread. The default position is necessarily that nowhere initially had a airfield. The onus is therefore on the proposers to produce evidence for the proposition that the Galapagos had one in 1941.

I have asked for sources that such an airfield existed TEN times and have received no specific answer.

Rather than evade the issue by placing it elsewhere, I would suggest it would be more appropriate to ask here what the two proposed sources are.

I personally don't mind whether there was or wasn't an airfield on the Galapagos, but I very much mind when posters make definitive and heavily emphasised statements on any subject that they repeatedly refuse to justify. This just undermines AHF's credibility as a research tool.

On the other hand it is rather important to this thread whether there was an airfield on the Galapagos or not and so it would most appropriately be addressed here.

Do you know what these two sources are yet? If so, please tell me. If not, why not ask yourself? Then we can at last begin to address if they have any substance.

Cheers,

Sid.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#456

Post by glenn239 » 28 Feb 2009, 16:34

Would it be too much to request some/any explanation at all from you as to why you think that such a torpedo/bomb attack would fail?
Assuming (very liberally) that the chances of the torpedo hit to be 50% and the complimentary bomb hit to be 15%, then the overall probability for a completed attack in a 0-defense environment is 7.5%. For three bombers, they will fail about 79% of the time. And that is with the gigantic caveat that supposes your theory of a bomb/torpedo combination is sufficient to achieve the task.

The original mission profile was stated as an attempt to increase the chance that an invasion of Oahu would succeed. However, if the probability of achieving the necessary result is as low as 7.5% per bomber, then the operational risks to such a mission would outweigh the probability of success, and so actually decrease the chances of an invasion of Oahu. The result would be the opposite to the original objective..

Overall impression is that you are vastly overrating the effectiveness of the tools available and underrating the resilience of the target.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#457

Post by phylo_roadking » 01 Mar 2009, 19:07

Assuming (very liberally) that the chances of the torpedo hit to be 50% and the complimentary bomb hit to be 15%, then the overall probability for a completed attack in a 0-defense environment is 7.5%. For three bombers, they will fail about 79% of the time.
...bearing in mind the requirement for all torpedoes to be delivered in the SAME point three times in a row. At Pearl Harbour the IJN couldn't even hit the 555foot-long USS Raleigh TWICE, let alone in the same place.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#458

Post by David Thompson » 01 Mar 2009, 22:47

Several posts from phylo_roadking, dealing with the Galapagos Islands airbase issue, were moved to the appropriate thread at http://forum.axishistory.com/viewtopic. ... 4&t=150312 .

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#459

Post by phylo_roadking » 01 Mar 2009, 22:57

In reference to the above, if viewed there the reader will now see that there IS a confirmed U.S. military presence in the Galapagos from late September 1941 onward.
So I'm afraid that puts the kibosh on Robert's idea that his attack could be mounted from the Galapagos; the Islands WERE covertly being used as a refueling facility by the USN's PBY flyingboats. I'm afraid you DO have an unfriendly "eye in the sky" above the Chitose...we NOW know it was agreed and set up, that the US Army was told by the US Navy it was operational AND the Japanese intelligence head-of-station knew about it.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#460

Post by ChristopherPerrien » 02 Mar 2009, 02:44

phylo_roadking wrote:
Assuming (very liberally) that the chances of the torpedo hit to be 50% and the complimentary bomb hit to be 15%, then the overall probability for a completed attack in a 0-defense environment is 7.5%. For three bombers, they will fail about 79% of the time.
...bearing in mind the requirement for all torpedoes to be delivered in the SAME point three times in a row. At Pearl Harbour the IJN couldn't even hit the 555foot-long USS Raleigh TWICE, let alone in the same place.
Well they did hit the Oklahoma 5+ times. But even that, is neither here nor there, in this "far-fetched" topic. I am suprised it has lasted this long.

Chris
Last edited by ChristopherPerrien on 02 Mar 2009, 02:58, edited 1 time in total.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#461

Post by Simon K » 02 Mar 2009, 02:58

RobDab has mentioned he needs to undertake further research in the U.S.
Therefore until further major evidence is produced I propose this thread go on ice and we should discuss the major adjunct of this minor diversion, the invasion of the Hawaiian Island(s). Is there an existing thread that has not been corrupted or shall the original author wish to resummarise and start afresh?
Loads of great research and a coherent WI operational plan was drafted. I cant see this attack being in any way critical to the main Hawaiian operation.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#462

Post by ChristopherPerrien » 02 Mar 2009, 03:15

Simon K wrote:RobDab has mentioned he needs to undertake further research in the U.S.
Therefore until further major evidence is produced I propose this thread go on ice and we should discuss the major adjunct of this minor diversion, the invasion of the Hawaiian Island(s). Is there an existing thread that has not been corrupted or shall the original author wish to resummarise and start afresh?
Loads of great research and a coherent WI operational plan was drafted. I cant see this attack being in any way critical to the main Hawaiian operation.
Try http://forum.axishistory.com/viewtopic. ... ilit=+oahu or http://forum.axishistory.com/viewtopic. ... it=+nagumo or http://forum.axishistory.com/viewtopic. ... ilit=+oahu

3 prime topics, 3 prime "suspects", :roll: :roll: :roll: , :) 8-)

Chris

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#463

Post by Simon K » 02 Mar 2009, 03:24

I was trying to be polite.
Dumb move :lol:
This is terminal dentistry at the moment.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#464

Post by David Thompson » 02 Mar 2009, 16:24

A post from Sid Guttridge, dealing with the Galapagos Islands airbase issue, was moved to the appropriate thread at http://forum.axishistory.com/viewtopic. ... 4&t=150312 .

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#465

Post by David Thompson » 02 Mar 2009, 18:07

An opinion post from moab76, containing insulting personal remarks about another poster, was removed by this moderator - DT.

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