# Allied/Axis Bomb-Shapes



## Zipper730 (Aug 6, 2018)

From what it appears: The USAAF/USN both employed bomb-fins that used an X-fin arrangement with a box-fin surrounding it (); the RAF used a cylindrical bomb-fin; the Luftwaffe used either X-fins with some designs having a cylindrical fin, at least one having a circular metal connector between the fins; the USSR seeming to use similarities to the Luftwaffe.

What motivated the decisions for the following

X-shaped fin with no cylindrical fin
X-shaped fins with cylindrical fin
X-shaped fins with box-fin
Were there any advantages and disadvantages


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## wuzak (Aug 6, 2018)

The cylindrical fin on British and German bombs was usually the same diameter, or less, as the body of the bomb.

The box fins are larger than the body of the bomb, so that becomes the limiting factor, rather than the body diameter.

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## Zipper730 (Aug 6, 2018)

wuzak said:


> The cylindrical fin on British and German bombs was usually the same diameter, or less, as the body of the bomb.


So the box-fins are bulkier?

Were the box-fins sturdier or flimsier, easier to build, more accurate?


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## tyrodtom (Aug 6, 2018)

Some of the German bombs were stored in the bomb bay vertically (H-111, maybe others too), fins down, so that fact might have had something to do with the size of the fins on German bombs.


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## Shortround6 (Aug 6, 2018)

Some of it has to do with the shape of the bombs.

British 250lb bomb






US 250lb bomb





Please note that the long cylindrical body and very quick taper at the rear of the bomb would not provide good airflow to fins that were the same diameter as the bomb. Supercaliber fins (larger than the body of the bomb) give the needed stability. The long gradual taper of the British bomb means the tail assembly will get good airflow.


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## wuzak (Aug 6, 2018)

MC bombs were closer in size to US GP bombs






Note that tails of some of the bombs were shortened to fit more into a bomb bay (500lb MC for Mosquito, 1,000lb MC for Lancaster) and it was found there was little difference in accuracy.

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## Zipper730 (Aug 6, 2018)

Shortround6 said:


> Some of it has to do with the shape of the bombs.


Was there a reason for the different bomb-shapes? The British seemed to have a better knowledge of aerodynamics than us, so I'm curious if that's it.


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## wuzak (Aug 6, 2018)

Zipper730 said:


> Was there a reason for the different bomb-shapes? The British seemed to have a better knowledge of aerodynamics than us, so I'm curious if that's it.



The British changed the shape of their bombs to something similar to the American shape.

The bomb shown by SR is a GP bomb. British GP bombs were developed in the '20s and early '30s and had a charge to weight ratio of ~25% compared to the American GP bomb charge to weight ratio of ~50%.

The British GP bomb may have been more aerodynamic, it certainly looks that way from the picture, but the shape may have contributed to the low charge to weight ratio.

In the late 1930s the British started developing the Medium Capacity (MC) bombs. I can't recall if that included a 250lb MC bomb, but they did develop 500lb MC, 1,000lb MC and 4,000lb MC bombs. Note that they did not develop a 2,000lb MC bomb.

They also developed the High Capacity (HC) bombs (~70-80% charge to weight). The first was the 2,000lb HC bomb, which was long and slender, the 4,000lb HC bomb (often called the Cookie), 8,000lb HC and 12,000lb HC bombs. The HC bombs were decidedly unaerodynamic, but did include some sort of tails for stability.

When the Mosquito was doing initial testing it was suggested that if the tails were cropped that 4 500lb MC bombs could be carried. This proved to be the case, doubling the design bomb load of the Mosquito. Ballistic tests showed little difference between the long and short tail bombs for accuracy.


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## Shortround6 (Aug 6, 2018)

Long, streamlined bombs need longer bomb bays than short fat bombs. 
short fat ones need wider/taller bomb bays. 

Iron/steel is much heavier per cubic in than high explosive material so bombs with a higher percentage of explosive are fatter than low capacity bombs of the same weight. 
Just because certain bombers could carry the right amount of weight doesn't mean they could carry an equal number of all types of bombs of that weight.

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## wuzak (Aug 6, 2018)

An example of how the size changed for the later bombs is the difference between the 1,000lb MC and GP (British) bombs.

From memory, the 1,000lb GP bomb was 13.5" in diameter. The 1,000lb MC bomb was 17.75" in diameter. I can't recall the lengths, but I believe the MC was significantly shorter than the GP.

Depending how the bomb bay is arranged, whether length, width or height is the limiting factor, one type could be favoured over another.

(The 1,000lb GP bomb had about as much explosive filling as the 500lb MC bomb, which was similar in diameter and much shorter, which meant that, potentially, more could be carried.)

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## dogsbody (Aug 6, 2018)

The RAF used lots of American made bombs during the last half of the war. If you see bombs with one lug on one side and two lugs on the other, it's an American bomb. Also, the tail fins were inter-changeable.

RAF bombs:






Chris

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## Zipper730 (Aug 6, 2018)

Shortround6 said:


> Long, streamlined bombs need longer bomb bays than short fat bombs


And with short fat bombs requiring deeper and wider bomb-bays the lesson evidently is "design your bombers with long cavernous bomb-bays", and never build several small bomb-bays when one huge one will do


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## Zipper730 (Aug 6, 2018)

wuzak said:


> An example of how the size changed for the later bombs is the difference between the 1,000lb MC and GP (British) bombs.
> 
> From memory, the 1,000lb GP bomb was 13.5" in diameter. The 1,000lb MC bomb was 17.75" in diameter. I can't recall the lengths, but I believe the MC was significantly shorter than the GP.


Is there any thread on this site regarding bomb-dimensions used by the USAAF, USN, RAF, and RN/FAA if not the Luftwaffe and former USSR?

If not, where would I find such things?


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## fubar57 (Aug 6, 2018)

Technical section has manuals for all I believe

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## wuzak (Aug 6, 2018)

fubar57 said:


> Technical section has manuals for all I believe



Certainly there are catalogs for British and American bombs. I haven't seen Russian or German bomb catalogs on here, but there must be something?

There are websites that have that information, too.

And books. I have a book on German bombs at home - "German Air Dropped Weapons", or similar, is the title.


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## fubar57 (Aug 6, 2018)

I'll get back to you. I believe I up-loaded both........


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## fubar57 (Aug 6, 2018)

This is the Russian one...




​....and the German one




​They're in here somewhere

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## pbehn (Aug 7, 2018)

With the accuracy of bomb aiming from 25,000 feet I think most of the aerodynamics was concerned with making sure the bomb exploded when it hit.

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## wuzak (Aug 7, 2018)

The Luftwaffe Resource Center has info on German bombs:

Luftwaffe Resource Center - Drop Ordnance - A Warbirds Resource Group Site


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## fastmongrel (Aug 7, 2018)

wuzak said:


> The British changed the shape of their bombs to something similar to the American shape.



The British Medium Capacity bomb body shape was inspired by the Luftwaffe SC (Sprengbombe Cylindrisch) but the tail design remained much the same as the older GP bombs. The GP bomb shape was very good aerodynamically and when Jets came along the bomb shapes reverted to the GP style though with much thinner higher quality steel walls to keep explosive capacity high


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## dogsbody (Sep 2, 2018)

Chris

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## wuzak (Sep 2, 2018)

That graphic doesn't give a type of some of the American bombs.

2 and 5 are General Purpose bombs.
3 is a light case bomb.

For the British bombs, 10 is the short tail version of the 1,000lb MC bomb, 9 is an early version of the 4,000lb HC bomb (MK I). 13 is a GP bomb, which had a much lower charge to weight ratio than the US GP bombs or the British MC bomb.

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## Zipper730 (Feb 17, 2019)

wuzak said:


> The British changed the shape of their bombs to something similar to the American shape.


Yet they still retained the cylindrical fins: I thought the box-fins were needed due to the plumper shape our bombs had. This clearly does not appear to be the case.


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## tyrodtom (Feb 17, 2019)

Except for the Tall-Boys and the armor piecing bombs, none of those bombs are designed with much thought to aerodynamics. Probably very few ever saw their shape evaluated in a wind tunnel.
As long as when they were released from the aircraft they fell away was all they cared about. 
They weren't looking for a individual bomb to be accurate, when you drop bombs in masses, it all averages out. 
Can you imagine the accuracy potential of that #9 bomb, all it had to guide it was gravity.

As for box or round tail fins, box fins were just cheaper to mass produce.


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## Zipper730 (Feb 17, 2019)

tyrodtom said:


> As for box or round tail fins, box fins were just cheaper to mass produce.


Okay, that makes sense... did they have to be supercalibur for it to work?


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## tyrodtom (Feb 17, 2019)

Zipper730 said:


> Okay, that makes sense... did they have to be supercalibur for it to work?


Define supercalibur .


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## fubar57 (Feb 17, 2019)

Must be the shortened version of this.......Supercalifragilisticexpialidocious

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## KiwiBiggles (Feb 17, 2019)

tyrodtom said:


> Define supercalibur .


A better Excalibur

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## Zipper730 (Feb 18, 2019)

tyrodtom said:


> Define supercalibur .


Diamter of the fins are bigger than the bomb fins


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## tyrodtom (Feb 18, 2019)

What ?
Or do you mean the fins are bigger than the diameter of the bomb ?
There may be some bombs like that, but I haven't noticed any.
Having the fins bigger than the bomb diameter will cause stowage problems.
Of coarse, the bombs would be much more stable with giant fins out back, but it would take up room in the bomb bay. plus increase the chance of bombs becoming entangled early in the drop.

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## Zipper730 (Feb 18, 2019)

tyrodtom said:


> Or do you mean the fins are bigger than the diameter of the bomb?


That's correct


> There may be some bombs like that, but I haven't noticed any.


Most of the bombs we built in the US fit that profile, I'm curious if we could have made them smaller...

I'm curious why the box fins are so much easier to manufacture, didn't they have a slip-roll back then?


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## fubar57 (Feb 18, 2019)

Somewhere in here might have something on the "Bomb Board" Records of the office of the Chief of Ordnance

"In 1921 the War Department convened a Bomb Board to conduct an extensive program for testing bombs against various kinds of structures and surfaces. The tests, running over a period of two years, provided data that guided the Ordnance Department and the Air Corps through the 1930s, Ordnance engineers strengthened demolition bomb cases by forging them as nearly as possible in one piece, with a minimum of welding, and substituted for the long fins of World War I short box fins that gave greater stability in flight"

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## tyrodtom (Feb 18, 2019)

Zipper730 said:


> That's correct
> Most of the bombs we built in the US fit that profile, I'm curious if we could have made them smaller...
> 
> I'm curious why the box fins are so much easier to manufacture, didn't they have a slip-roll back then?



Can you post any picture where US bombs have fins that stick out beyond the largest diameter of the bomb body ?

Of course they had slip rolls back then, it's easier to assemble about any structure out of flat panels than curved.

The way bombs in the early 20's and 30's was made didn't have a lot to do with the methods the manufactories went to when they had to start mass producing bombs.

I've had close contact with plenty of WW2 munitions, one word that describes them best is crude.


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## Zipper730 (Feb 18, 2019)

tyrodtom said:


> Can you post any picture where US bombs have fins that stick out beyond the largest diameter of the bomb body?


I don't have dimensions readily on hand...


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## GrauGeist (Feb 18, 2019)

tyrodtom said:


> Can you post any picture where US bombs have fins that stick out beyond the largest diameter of the bomb body ?


Several of the AP/semi-AP bombs had fins that extended beyond the body of the bomb, like the AN-M58 (500lb), AN-M59 (1,000lb) and so on.

Here's an image of the AN-M59, used by both the USN and USAAF:

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## Zipper730 (Feb 18, 2019)

GrauGeist said:


> Several of the AP/semi-AP bombs had fins that extended beyond the body of the bomb, like the AN-M58 (500lb), AN-M59 (1,000lb) and so on.
> 
> Here's an image of the AN-M59, used by both the USN and USAAF:
> View attachment 529570


What I meant was the diameter of the fins, not their length. The fins are way bigger than the diameter of the rest of the projectile


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## fubar57 (Feb 18, 2019)

Zipper730 said:


> What I meant was the diameter of the fins, not their length. The fins are way bigger than the diameter of the rest of the projectile


You mean exactly as the photo in Post #34 shows?

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## Zipper730 (Feb 18, 2019)

fubar57


Well post #35


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## tyrodtom (Feb 18, 2019)

Maybe my memory has failed me on this, I just don't remember those fins sticking out hardly any beyond the bombs girth. 
Those fins extend maybe 6 inches beyond the biggest diameter of the bomb. 
If they extend too much, they interfere with mounting the bombs externally on bomb racks. The fins will touch the aircraft's structure underneath the wing.

The bombs I'm familiar with could have the fins rotated, either inline with the hanging lugs, or on either side of the lugs.


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## GrauGeist (Feb 18, 2019)

Probably not a failure of memory at all.

I'm sure that most WWII ordnance (in the way of bombs, at least) were used up in Korea or at least equipped with a new tailfin standardization by the time of the Vietnam war. With the advent of the jets, there had to be a uniform (more compact) shape that would allow for mounting on various jet's hardpoints without danger of damage to the wing surface.

I recall perusing Long Beach surplus when I was a kid in the 70's and they had a mountain of tailfin assemblies piled up out back that were WWII and Korean war vintage.

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## tyrodtom (Feb 19, 2019)

No we were still using WW2 munitions, partly at NKP, Thailand.
We operated only prop jobs, A1, AT-28, A 26, O-2, etc.
I remember one in particular, a British 500 lbs thermite cluster bomb, I think M-47,or MK-47, we had a lot of problems with it after it had been in storage somewhere for over 20 years.
That same M-47 designated some other bomb types too

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## alsaad (Feb 21, 2019)

Highly recomend following titles:

Wolfgang Fleischer- German Air-Dropped Weapons to 1945 

John A. MacBean and 2 more - Bombs Gone: Development and Use of British Air-dropped Weapons from 1912 to Present Day 

Castle and Bromwich - Story of Ordnance

Arthur Hariss - War dispatches

There you will find a lot on development and use of the aerial bombs. There are several more titles like col. Meriman - Italian Bombs and Fuzes and few on Soviet bombs which can put some light on the topic.


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## alsaad (Feb 21, 2019)

fastmongrel said:


> The British Medium Capacity bomb body shape was inspired by the Luftwaffe SC (Sprengbombe Cylindrisch) but the tail design remained much the same as the older GP bombs. The GP bomb shape was very good aerodynamically and when Jets came along the bomb shapes reverted to the GP style though with much thinner higher quality steel walls to keep explosive capacity high



British MC design was inspired by both German SC and US GP design. Actually, British GP design was among the poorest bomb designs at the beginning of the WWII. Quality of British steel prior to WWII was lower than US and German forcing British bomb designers to increase bomb casing thickness and decrease charge weight. That is why British bombs performed worse than German. That was the reason for the development of MC series which corresponds with SC and US GP designs.


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## Brooke (Feb 21, 2019)

pbehn said:


> With the accuracy of bomb aiming from 25,000 feet I think most of the aerodynamics was concerned with making sure the bomb exploded when it hit.



This is the elephant in the room. Horizontal iron bombs are very inaccurate. The Navy developed the Norden bombsight and after testing it went to dive bombing. The Army picked it up but when they tried to do "precision bombing" it was a failure and "carpet bombing" was the outcome. 
Gyroscopes
Aircraft
TED: Malcolm Gladwell: The strange tale of the Norden bombsight


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## BAGTIC (Feb 21, 2019)

tyrodtom said:


> Some of the German bombs were stored in the bomb bay vertically (H-111, maybe others too), fins down, so that fact might have had something to do with the size of the fins on German bombs.



I have often wondered* why *some German bombs were stored vertically tail down. As a child I was intrigued by videos of them doing their flip.

Did this have any effects on accuracy versus a horizontal drop?


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## alsaad (Feb 22, 2019)

Part of the answer is in the fact that all German bombs larger than 50 kg had transversal electrical fuzes rather than mechanical nose/tail setup. In such design it was much easier to provide arming installations in the bomb bay for the bombs in vertical position. The other part of answer is fact that German bombers could receive more bombs in there bomb bays vertically than horizontally. For the same reason Italians were hanging their bombs vertically in some bombers.


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## tomo pauk (Feb 22, 2019)

alsaad said:


> ...
> The other part of answer is fact that German bombers could receive more bombs in there bomb bays vertically than horizontally.
> ...



IIRC only the He 111 was able to carry bombs in vertical position, 8 x 250kg. 
Do-217 carried up to 3 tons of bombs, all in horizontal position.


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## Shortround6 (Feb 22, 2019)

I believe the HE 111 could carry 110lb bombs (50Kg) in the vertical cells, four per cell that carried a single 250kg bomb.


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## fastmongrel (Feb 22, 2019)

alsaad said:


> British MC design was inspired by both German SC and US GP design. Actually, British GP design was among the poorest bomb designs at the beginning of the WWII. Quality of British steel prior to WWII was lower than US and German forcing British bomb designers to increase bomb casing thickness and decrease charge weight. That is why British bombs performed worse than German. That was the reason for the development of MC series which corresponds with SC and US GP designs.



There was nothing wrong with the steel but the low filling weight was down to the fact that the bombs were cast steel rather than the German SC bombs which were forged and rolled. The design of the later MC bomb probably owes virtually everything to the SC after all there were plenty of them to study they were falling out of the sky for free, whereas a US GP bomb would have to be imported for hard cash before 1942.

There was a problem with bad fuses on the GP bombs caused by the mad rush to ramp up production in 1940/41. Fuses are a precision manufacturing job not something you can easily farm out to an inexperienced company. 

The aerodynamics of the GP were very good for external carry but explosive weight counts for more in wartime than fuel savings.

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## alsaad (Feb 22, 2019)

British forging technology prior to WW2 could not produce casing strong enough so they were forced to produce casings by casting and make them thick. Later that technology improved due to some American "know how" and British could produce thinner casings that were strong enough not to break upon impact. The other thing is that prior to WW2 in Britain there was literally no live bomb drop tests but structural strength of the bombs was tested by firing bombs from some kind of gun to concrete obstacles while explosion effects were tested by static bomb detonation. Only aerodynamics was tested by dropping the dummy bomb. The results were bombs with the poorest terminal effect at the beginning of the War. Very important thing is that drop like shape of the British GP series, even very aerodynamic, leaves smaller explosive cavity than cylindrical SC/US GP bombs shape.


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## alsaad (Feb 22, 2019)

And regarding the fuses... if you look into British No 28 or No 30 tail pistol you will notice that they were functioning same way as US AN M100/101/102 fuse...and mostly every inertia operated tail fuse...which was quite satisfactory. Problem with British fuses generally was not malfunction upon impact but short arming time and vertical safety due to no arming gear mechanism which was present on US fuses. Short arming time sometimes caused bombs to detonate in mid air after colliding with each other too close to the aircraft which dropped them and to destroy or damage it. For example on US fuses vanes had to make no less than 158 revolutions to arm the fuse (except on fuses for low level bombing) while on British fuses arming process was completed after 7-11 revolutions.


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## Shortround6 (Feb 22, 2019)

The British seem to have had a "thing" for cheap ammo and it also seems that some of the lessons of WW I had been forgotten. 

see, Shell Crisis of 1915 - Wikipedia

for just part of it.

The follow up part was that scores of guns (if not hundreds) were wrecked and scores of gunners killed/wounded when the hastily built substitute standard shells were used at the front and prematures began to happen (shell explodes in the bore of the gun or just in front of the muzzle). 

Part of the "solution" between the wars seems to have been a deliberate policy of designing ammunition that could be built using low grade steel and still have a decent safety margin. 
The 'trap" with this solution is that you need more shells to get the same target effect if the desired effect was destruction of earth works or buildings. A British 25pdr shell carried less explosive than an American 75mm shell of less that 15lbs. 

The British for example were still fooling around with a cast iron projectile for the 25pdr gun half way through 1944. after years of effort and numerous trials where the projectiles (or at least a certain percentage) simply disintegrated after leaving the muzzle due to centrifugal force. Cast Iron may work for mortar shells (no rotational forces) and the British may have learned quite a bit about cast iron in high stress situations but it had zero effect on the artillery war. 

This may have carried over to the aircraft bombs. Or the price they were willing to spend for them.


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## alsaad (Feb 22, 2019)

The British after WWI ended reduced investment into the explosive ordnance development. Due to such policy at some point during late 1930s they just could not keep up with Germans which ordnance designs at the time were among the best globally. Fortunately on some other fields British were in front of Germans significantly.


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## fastmongrel (Feb 23, 2019)

alsaad said:


> British forging technology prior to WW2 could not produce casing strong enough so they were forced to produce casings by casting and make them thick. Later that technology improved due to some American "know how"




The casting method of production and the cheap low grade Steel were chosen for cost reasons not because the forging method was faulty. Forging and or rolling a shape like a bomb casing was well known technology by the 20th Century. After all if virtually every foundry in Europe could do it in WWI why would they suddenly lose the knowledge.


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## alsaad (Feb 24, 2019)

Drop like shape chosen by British was much easier do cast than to forge, that might be a part of the answer too. However British were on the wrong path of the development as they admitted by themselves. On the other side 500lbs GB bomb with 531.334 pieces expended by the Bomber Command was the most used bomb from the British inventory. Still in the 1000lbs category MC with 253.800 pieces expended is far in front of GP with 82.164 pieces dropped.

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## Reluctant Poster (Feb 24, 2019)

alsaad said:


> The British after WWI ended reduced investment into the explosive ordnance development. Due to such policy at some point during late 1930s they just could not keep up with Germans which ordnance designs at the time were among the best globally. Fortunately on some other fields British were in front of Germans significantly.


Britain did make significant advances in explosives, in particular their development of RDX.


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## alsaad (Feb 24, 2019)

RDX, cyclonite or hexogen is invented in Germany. British took part in the invention of the method for desensitising RDX by mixing it with small amount of wax. Germans did it by mixing RDX with graphite. British actually invented Torpex (Torpedo explosive) which was mixture of RDX, TNT and aluminum powder and about 50% more brisant than TNT, but that explosive was not in use prior to mid 1942. It was used in MC bombs 500-4000lbs, HC 4000 lbs and both DP bombs. US version of RDX based mixture was Comp B present in some number of US GP bombs. Germans in their bombs used Trialen which had only about 15% of RDX.

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## Zipper730 (Mar 19, 2019)

fubar57 said:


> "In 1921 the War Department convened a Bomb Board to conduct an extensive program for testing bombs against various kinds of structures and surfaces. The tests, running over a period of two years, provided data that guided the Ordnance Department and the Air Corps through the 1930s, Ordnance engineers strengthened demolition bomb cases by forging them as nearly as possible in one piece, with a minimum of welding, and substituted for the long fins of World War I short box fins that gave greater stability in flight"


So the box-fins came out of this period of time?


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## Zipper730 (Jun 10, 2019)

I read the article, and will post some questions and stuff later, provided I remember.


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## Niceoldguy58 (Jun 11, 2019)

I was very recently reading some USAAC documents on tests in the late 1930's of round bomb "fins" -which the Air Corps had been using since WWI - vs the box fin. The AAC's findings were that the box fin made the bombs more stable and allowed for greater accuracy, a very important aspect to the Air Corps and its daylight bombing philosophy. 

Thus the box fins.

AlanG


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## Zipper730 (Jun 11, 2019)

Niceoldguy58 said:


> I was very recently reading some USAAC documents on tests in the late 1930's of round bomb "fins" -which the Air Corps had been using since WWI - vs the box fin. The AAC's findings were that the box fin made the bombs more stable and allowed for greater accuracy, a very important aspect to the Air Corps and its daylight bombing philosophy.


From what I was reading from this site, I got...


> In 1921 the War Department convened a Bomb Board to conduct an extensive program for testing bombs against various kinds of structures and surfaces. The tests, running over a period of two years, provided data that guided the Ordnance Department and the Air Corps through the 1930s, Ordnance engineers strengthened demolition bomb cases by forging them as nearly as possible in one piece, with a minimum of welding, and substituted for the long fins of World War I short box fins that gave greater stability in flight. Uniformity of fragment size of the fragmentation bomb was achieved by encasing the body in rings cut from steel tubing or in wound steel coil. For low-level bombing, experiments with means of delaying the action of the fragmentation bomb sufficiently to permit the airplane to get to a safe distance before the bomb detonated produced a parachute attachment in place of fins. The parachute slowed descent and caused the bomb to strike the ground with its axis nearly vertical so that the fragments tended to be scattered above ground instead of being buried. Collaboration with the Chemical Warfare Service developed bombs that could be filled either with a fire-producing substance or with gas or smoke. The filling was the responsibility of the Chemical Warfare Service, the case of the Ordnance Department. The case had thin walls like the demolition bomb but had a burster tube running down its center. Shortly before the United States entered World War development of the incendiary bomb became entirely the responsibility of the Chemical Warfare Service.


I'm not sure what types of fins they evaluated from

The old, long annular fin
The short box-fin
All the designs in between
You'd think a cylindrical fin of proper aerodynamics (the cross-section of the fin) would work better because the airflow over the bomb is circular, and the airflow over the fin is circular, plus a box-fin is made of an upper & lower, bottom & top, as well as four fins at the junctions, where as an annular fin has the annular ring (one part), and the X-fin arrangement as before.


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## tyrodtom (Jun 11, 2019)

Zipper730 said:


> From what I was reading from this site, I got...
> I'm not sure what types of fins they evaluated from
> 
> The old, long annular fin
> ...



That ring was or box section purpose was to brace the fins.
The major cause of inaccuracy in a bomb is the fins vibrating or moving around, it's easier to brace the fins, and stronger, with just a straight piece of steel between the fins.
The US bombs were quite squatty, the fins were mostly in turbulent airflow.
A curved piece between the fins would just change it's curvature, and let the fins still move around unless you made it very thick and heavy..

Also box fins meant the bombs were easier to handle on the ground once the fins were installed. You could set them on a trailer, still had to tie them down, but not as much trouble keeping them in place as you would have with a round fin at the back.

You'll notice on about any aircraft that has a visible external brace of a flying surface, that brace, is straight, not curved.

What they did later when aircraft got faster was get rid of the brace between the fins entirely, they made the fins stronger.


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## Shortround6 (Jun 11, 2019)

The box fins had an advantage (theoretical?) in that they were super caliber. That merely means that the span of the fins (over the diagonal) was greater than the diameter of the bomb and the last few inches of the fins should be operating in undisturbed air. 

US bombs tended to short squatty things with a rather abrupt taper at the rear end.






Airflow over the fins of a circular or drum shape of equal or lesser diameter than the bomb body is going to be turbulent. 
The British used a much more gradual taper on their bombs 





At least in the early part of the war. Please note the two british bombs are not to scale. The 250lb bomb was 10.2in in diameter while the 500lb bomb was 12.9in and the 500lb bomb was about 25% longer with standard fins.


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## wuzak (Jun 11, 2019)

Those would be the GP bombs, with about 25%-30% charge-to-weight ratio.

The MC bombs, introduced early in the war, were more like US GP bombs.

500lb MC bomb
500lb Mk.II Bomb (M.C. = Medium Capacity) by Lord Throplebury of Winklesham

This also appears to be the long/standard tail.

IIRC, the 500lb MC had a diameter of 17.75", nearly 5" greater than the GP equivalent.


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## wuzak (Jun 11, 2019)

These MC bombs (500lb and 1,000lb) have the short tails, though it is hard to see from that angle. Also there is the 4,000lb MC bomb. Seems they didn't bother with a 2,000lb MC bomb.

https://i1.wp.com/www.junobeach.org/wp-content/uploads/2014/04/arms_air_bomber_aircraft_3.jpg 

Aircraft, Bombs and Radars


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## Zipper730 (Jun 12, 2019)

tyrodtom said:


> That ring was or box section purpose was to brace the fins.


Didn't know that


> The major cause of inaccuracy in a bomb is the fins vibrating or moving around, it's easier to brace the fins, and stronger, with just a straight piece of steel between the fins.


Didn't know that. I thought the ring had some aerodynamic benefit. It makes sense that they'd be in turbulent airflow, but aircraft have tails in the rear too and they clearly have a benefit, so I figured if the ring shape was used, the airflow would still be cylindrical (the cross section of the bomb) rather than cubic (the fins).


> A curved piece between the fins would just change it's curvature, and let the fins still move around unless you made it very thick and heavy.


Are we talking about the curve of the fins? Also, how much did the RAF's annular ring cost over our box-fins?

As for the removal of the braces, that makes a lot of sense, and to be honest, a lot of the bombs that we'd carry later on kind of had the same look as the tallboy, just smaller.



Shortround6 said:


> The box fins had an advantage (theoretical?) in that they were super caliber. That merely means that the span of the fins (over the diagonal) was greater than the diameter of the bomb and the last few inches of the fins should be operating in undisturbed air.


You still do require more space in the bomber to carry them.

Did they produce any significant ballistic accuracy improvement?


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## tyrodtom (Jun 12, 2019)

If you'll look at the American AN M64 bomb in Shortround6's post and the British Mk II bomb in Wuzak's post you'll notice both are 500 lbs bombs, with very similar bomb bodies, but different fins. 

Just the British bomb is quite a bit longer, the more tapered tail might have produced less turbulence, and might have been a more accurate bomb
But the longer length might have meant fewer bombs could be carried in some bomb bays. 

A lot of war material America made during WW2 might not have been the best that could have been made.
But whatever they made, they made in massive amounts.
A lot of the massive production came from designing products so they were simple to produce.

I don't like quoting Stalin, but I think he said " quantity has a quality all it's own "


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## Shortround6 (Jun 12, 2019)

Unless you could drop both bombs at the same time from the same plane and do so repeatedly and measure the miss distances (or drop a crap load (thousands) of each type and plot the miss distances) you are not going to get a good comparison. There are too many variables for small scale testing to sort out if the bombs are dropped on different flights even on the same day.

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## Reluctant Poster (Jun 15, 2019)

alsaad said:


> RDX, cyclonite or hexogen is invented in Germany. British took part in the invention of the method for desensitising RDX by mixing it with small amount of wax. Germans did it by mixing RDX with graphite. British actually invented Torpex (Torpedo explosive) which was mixture of RDX, TNT and aluminum powder and about 50% more brisant than TNT, but that explosive was not in use prior to mid 1942. It was used in MC bombs 500-4000lbs, HC 4000 lbs and both DP bombs. US version of RDX based mixture was Comp B present in some number of US GP bombs. Germans in their bombs used Trialen which had only about 15% of RDX.


A poorly worded post on my part. I was intending to convey the point you are making ie the development of explosives based on RDX as well as methods of production that greatly increased output. Torpex was actually preceded by Minol in torpedoes and depth charges


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## alsaad (Jun 20, 2019)

Related to box shaped fins...box and shrouded fins give more stabilizing surface for the same length and span. i.e. making bomb overall length shorter, reducing longitudinal vibrations in the airflow thus making trajectory smoother.


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## Dimlee (Jun 26, 2019)

tyrodtom said:


> I don't like quoting Stalin, but I think he said " quantity has a quality all it's own "



He did not. Another misattributed quote.
He could say/write something similar of more general meaning as "quantity turns into quality", since that was typical for Engels and Hegel, whose works were studied by all Communists at that time.


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## Milosh (Jun 26, 2019)

Did any of the bombs under 2000lb have fins that caused the bombs to rotate in flight?


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## Zipper730 (Jul 2, 2019)

This is something confusion here, there are two figures here for the 4000 lb light-case AN/M56: Two different sources list 34.25" as diameter, the other listing 36" (3'). One source was from 1944 (which lists dimensions), the other from 1950 (which lists a picture)

The thing is usually the overall body diameter (not the fin diameter) seems bigger than basic cylindrical body (the basic bomb-body shape minus all the stuff that allows it to be mounted to the aircraft). I'm not certain which figure is correct, as it seems to be the same model depicted.


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## Zipper730 (Mar 17, 2020)

Niceoldguy58 said:


> I was very recently reading some USAAC documents on tests in the late 1930's of round bomb "fins" -which the Air Corps had been using since WWI - vs the box fin. The AAC's findings were that the box fin made the bombs more stable and allowed for greater accuracy, a very important aspect to the Air Corps and its daylight bombing philosophy.


So, they were doing tests all the way into the 1930's?


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## Zipper730 (Oct 29, 2020)

I should seriously start putting together my excel graph on this.


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## Zipper730 (Jan 17, 2021)

I'm curious if I should do it by nation or by type and mass?


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## GrauGeist (Jan 17, 2021)

By nation would provide a good contrast of types, then you can do the weights and types as a sublist within each nation's list.

And don't forget to include the US's 55 gallon drum bombs that had plywood fins!


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## Zipper730 (Jan 18, 2021)

I never heard of the 55 gallon drum bomb


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## pbehn (Jan 18, 2021)

Zipper730 said:


> I never heard of the 55 gallon drum bomb


I have a feeling that I know what it looks like.


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## GrauGeist (Jan 18, 2021)

Zipper730 said:


> I never heard of the 55 gallon drum bomb


Used on some occasions in the Pacific.

Posted (with pic) about it a while back, here:
Picture of the day.


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## Zipper730 (Jan 18, 2021)

I'm starting to set-up the list. It's interesting that the RAF and USAAF have some differences in categories.


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## wuzak (Jan 19, 2021)

Zipper730 said:


> I'm starting to set-up the list. It's interesting that the RAF and USAAF have some differences in categories.



Such as?

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## Zipper730 (Jan 19, 2021)

wuzak said:


> Such as?


If I recall, the RAF had the following categories of bombs

Fragmentation
General Purpose & Medium Capacity
High Capacity
Armor Piercing / Semi-Armor Piercing
Anti-Tank
Deep-Penetration
Anti-Submarine
Depth-Charges
Buoyancy Bombs (Mines)
Smoke & Target Identification
Light-Case (Chemical Warfare)
Incendiaries
Practice
Miscellaneous
The USAAF had the following

General Purpose/Demolition
Light Case
Armor/Semiarmor Piercing
Depth-Bombs
Chemical: Incendiary / War Gas
Fragmentation
Clusters
Practice / Drill
Differences

The US designation for General Purpose would cover the UK's deep-penetration category
The RAF's light case would go under part of the US's chemical category
The US doesn't seem to have an anti-tank category, so I guess AP/SAP and possibly some cluster munitions might be covered there
The US doesn't seem to have a mine category listed, though we dropped an enormous amount in WWII.
The following sources I have are as follows

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## GrauGeist (Jan 19, 2021)

I believe the USN used the Mark 12 and Mark 13 mines.

The USAAF also mined Japanese waters extensively with their B-29s, so I might think that they would have used USN Mark 12s for the job.


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## wuzak (Jan 19, 2021)

Zipper730 said:


> If I recall, the RAF had the following categories of bombs
> 
> Differences
> 
> ...



Since the US didn't have any deep penetration bombs in WW2, I doubt that they would fit into the GP bomb category.

RAF's High Capacity (HC) would be equivalent to US Light Case.

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## Zipper730 (Jan 20, 2021)

So I guess one could place

USA light-case w/ RAF's high capacity
USA depth bombs w/ RAF's anti-submarine bombs
Should mines used by the US be put under the UK depth-bombs / anti-submarine bomb category or put under something else? Some were basically torpedoes, so...


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## wuzak (Jan 20, 2021)

Zipper730 said:


> So I guess one could place
> 
> USA light-case w/ RAF's high capacity
> USA depth bombs w/ RAF's anti-submarine bombs
> Should mines used by the US be put under the UK depth-bombs / anti-submarine bomb category or put under something else? Some were basically torpedoes, so...



I would think "depth bombs" would be in the same category as "depth charges".


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## pbehn (Jan 20, 2021)

Zipper730 said:


> So I guess one could place
> 
> USA light-case w/ RAF's high capacity
> USA depth bombs w/ RAF's anti-submarine bombs
> Should mines used by the US be put under the UK depth-bombs / anti-submarine bomb category or put under something else? Some were basically torpedoes, so...


Well a mine isn't a depth charge or anti submarine bomb but usage can change, the Germans dropped mines on cities by parachute.


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## Zipper730 (Jan 20, 2021)

The US's Depth Bomb category seems to include the UK's Anti-Submarine and Depth Charge category.

The UK buoyancy bombs are basically mines, but they don't _appear_ to be self-propelled, but some of the mines we used in WWII were self-propelled. I suppose buoyancy bombs and mines could be put together. Do you or anybody else here have anything on types of torpedoes deployed from airplanes either used by the USAAF, USN, RAF/RN:FAA?


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## GrauGeist (Jan 20, 2021)

The USN's Mark 13 could be used as a bomb, too.
So perhaps if you are categorizing bombs in groups like AP, HEI and such, maybe create a maritime category that covers depth-charges, mines and torpedoes?


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## Zipper730 (Jan 21, 2021)

GrauGeist said:


> The USN's Mark 13 could be used as a bomb, too.


So, they just took the screws off and all the associated equipment and hooked it onto a bomber and dropped it on it's way?


> So perhaps if you are categorizing bombs in groups like AP, HEI and such, maybe create a maritime category that covers depth-charges, mines and torpedoes?


Well, I was thinking of going from general to specific and from explosive to non-explosives.

So I figured

General purpose
High Capacity
SAP / AP / Anti-Tank
Deep-Penetration
Depth-Bomb/Anti-Submarine & Torpedoes/Anti-Submarine
Blast-Frag
Incendiaries
Smoke & Target Identification
Chemical Warfare
Letter Bombs
Practice & Drill
Sound good?


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## GrauGeist (Jan 21, 2021)

Zipper730 said:


> So, they just took the screws off and all the associated equipment and hooked it onto a bomber and dropped it on it's way?


Appears that it didn't need any mods, it was designed to be air-dropped outright.
Even though It had a magnetic trigger, being dropped on a target simply removed the "wait for it..." portion of it's original mission.

Follow this link, the Mark 13 is aboit halfway down:Mines of the United States of America - NavWeaps



Zipper730 said:


> Well, I was thinking of going from general to specific and from explosive to non-explosives.
> 
> So I figured
> 
> ...


Looks great!


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## nuuumannn (Jan 21, 2021)

BAGTIC said:


> I have often wondered* why *some German bombs were stored vertically tail down.



As Tomo stated, it was just the He 111 that had vertically stowed bombs, out of the German aircraft. The reason behind this was that it's bomb bay was essentially created by having holes in the floor structure and building containers to stow the bombs within the confines of the fuselage. The bay doors were rubber and it was not uncommon for the fins to strike the doors on the way out. This comes from the dual intent of the type being designed as a transport as well. The He 111 could carry larger bombs on exterior pylons as well, but these increased drag and reduced its good performance for the mid to late 30s bomber set.





Bomb doors

The Italian SM.79 had similarly configured bomb stowage for essentially the same reason; it too had a dual purpose of sharing its airframe between airliner and bomber.




Bomb bay

In terms of affecting accuracy, depends on what you are trying to do. In terms of carpet bombing, doesn't really make much of a difference if the intent is a large number of aircraft to level city blocks, but if you are wanting to attack smaller targets, like a ship or an aircraft hangar, it doesn't appear to have made too much of a difference in some cases, as the Luftwaffe used the He 111 in these scenarios and scored successful hits, although not in every occasion. Within days of the war's outbreak an He 111 dropped bombs on and sank two Kriegsmarine destroyers during a naval exercise, the pilot thinking the German ships were British. Of course, things like wind speed, wind direction, altitude, aircraft speed etc all affect bomb delivery.


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## Airframes (Jan 22, 2021)

Note that the Ju-52, when fitted for bombing ( and some were in WW2), also used the "vertical cell" type of bomb stowage, as in the He-111.

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## Snautzer01 (Jan 22, 2021)

Airframes said:


> Note that the Ju-52, when fitted for bombing ( and some were in WW2), also used the "vertical cell" type of bomb stowage, as in the He-111.


And a very few wing mounted bombs. I have a photo.


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## Koopernic (Jan 23, 2021)

pbehn said:


> Well a mine isn't a depth charge or anti submarine bomb but usage can change, the Germans dropped mines on cities by parachute.



That claim is common but has been called into doubt or at least contested. Parachute retarded anti shipping mines were deliberately aimed at and dropped into the harbours of British ports to disrupt and sink shipping. The ones that missed the water and landed on land self destructed (about 10 seconds latter) in part to protect the secrets of the trigger. It appears they were never dropped on land targets deliberately (expensive and probably less accurate). Of course the many that hit warehouses and port side dwellings would have been perceived as deliberate and perhaps . To an extent this collateral damage may have been deliberate side effect. Likely in my view.

In German usage the term “mine” is used for a munition designed to destroy entirely by blast rather than splinters or penetration.


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## Koopernic (Jan 23, 2021)

wuzak said:


> Since the US didn't have any deep penetration bombs in WW2, I doubt that they would fit into the GP bomb category.
> 
> RAF's High Capacity (HC) would be equivalent to US Light Case.


They had the Disney bomb similar to the German rocket boosted bombs


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## Juha3 (Jan 23, 2021)

Koopernic said:


> That claim is common but has been called into doubt or at least contested. Parachute retarded anti shipping mines were deliberately aimed at and dropped into the harbours of British ports to disrupt and sink shipping. The ones that missed the water and landed on land self destructed (about 10 seconds latter) in part to protect the secrets of the trigger. It appears they were never dropped on land targets deliberately (expensive and probably less accurate). Of course the many that hit warehouses and port side dwellings would have been perceived as deliberate and perhaps . To an extent this collateral damage may have been deliberate side effect. Likely in my view.
> 
> In German usage the term “mine” is used for a munition designed to destroy entirely by blast rather than splinters or penetration.



22 second self-destruction time. And definitely they were deliberately dropped on land targets, Central London etc, because of their blast effect.


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## Juha3 (Jan 23, 2021)

.


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## pbehn (Jan 23, 2021)

Koopernic said:


> That claim is common but has been called into doubt or at least contested. Parachute retarded anti shipping mines were deliberately aimed at and dropped into the harbours of British ports to disrupt and sink shipping. The ones that missed the water and landed on land self destructed (about 10 seconds latter) in part to protect the secrets of the trigger. It appears they were never dropped on land targets deliberately (expensive and probably less accurate). Of course the many that hit warehouses and port side dwellings would have been perceived as deliberate and perhaps . To an extent this collateral damage may have been deliberate side effect. Likely in my view.
> 
> In German usage the term “mine” is used for a munition designed to destroy entirely by blast rather than splinters or penetration.


If you can show me the harbour and docks in Coventry Manchester and Birmingham you have a point.


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## wuzak (Jan 23, 2021)

Koopernic said:


> They had the Disney bomb similar to the German rocket boosted bombs



The Disney Bomb was developed and manufactured by the British.


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## Milosh (Jan 25, 2021)

Liverpool - Unexploded parachute mine sits in a garden on Score Lane, Childwall. 28 November 1940 






SC2500???

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## Zipper730 (Jan 25, 2021)

Milosh said:


> Liverpool - Unexploded parachute mine sits in a garden on Score Lane, Childwall. 28 November 1940
> View attachment 610187
> 
> 
> SC2500???


No wonder the British and German bomb-disposal guys are trained in disarming old bombs. It wasn't long ago that they found a cookie under a bank in Germany, and I don't mean the kind with chocolate chips.


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## pbehn (Jan 25, 2021)

Zipper730 said:


> No wonder the British and German bomb-disposal guys are trained in disarming old bombs. It wasn't long ago that they found a cookie under a bank in Germany, and I don't mean the kind with chocolate chips.


They find bombs all the time in Germany and elsewhere in Europe it rarely makes the news. Farmers in France where the WW1 trenches were plough up unexploded shells all the time, they just put them in the corner of a field until they have a pile and call someone to dispose of them.

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## nuuumannn (Jan 25, 2021)

Zipper730 said:


> It wasn't long ago that they found a cookie under a bank in Germany, and I don't mean the kind with chocolate chips.



When I was in Berlin in 2019 they discovered an unexploded munition. This was the day I was doing my city stroll around that area. The centre of Alexanderplatz, near where the bomb was found that same afternoon.




Berlin Tour 91 

World War II bomb defused in Berlin | News | DW | 15.06.2019


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## wuzak (Jan 25, 2021)

Zipper730 said:


> No wonder the British and German bomb-disposal guys are trained in disarming old bombs. It wasn't long ago that they found a cookie under a bank in Germany, and I don't mean the kind with chocolate chips.



https://raafansw.org.au/docPDF/Gate_Guard_bomb_was_live1958_Vintage_news_151106.pdf

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## Dimlee (Jan 27, 2021)

Milosh said:


> Liverpool - Unexploded parachute mine sits in a garden on Score Lane, Childwall. 28 November 1940
> View attachment 610187
> 
> 
> SC2500???



Luftmine B, more likely.
Parachute mine - Wikipedia
SC2500 bomb - Wikipedia


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## Dimlee (Jan 27, 2021)

pbehn said:


> They find bombs all the time in Germany and elsewhere in Europe it rarely makes the news. Farmers in France where the WW1 trenches were plough up unexploded shells all the time, they just put them in the corner of a field until they have a pile and call someone to dispose of them.



"Even now, 70 years later, more than 2,000 tons of unexploded munitions are uncovered on German soil every year. Before any construction project begins in Germany, from the extension of a home to track-laying by the national railroad authority, the ground must be certified as cleared of unexploded ordnance....
Eleven bomb technicians have been killed in Germany since 2000, including three who died in a single explosion while trying to defuse a 1,000-pound bomb on the site of a popular flea market in Göttingen in 2010...
Early one recent winter morning, Horst Reinhardt, chief of the Brandenburg state KMBD, told me that when he started in bomb disposal in 1986, he never believed he would still be at it almost 30 years later. Yet his men discover more than 500 tons of unexploded munitions every year and defuse an aerial bomb every two weeks or so..."
There Are Still Thousands of Tons of Unexploded Bombs in Germany, Left Over From World War II | History | Smithsonian Magazine

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## pbehn (Jan 27, 2021)

Dimlee said:


> "Even now, 70 years later, more than 2,000 tons of unexploded munitions are uncovered on German soil every year. Before any construction project begins in Germany, from the extension of a home to track-laying by the national railroad authority, the ground must be certified as cleared of unexploded ordnance....
> Eleven bomb technicians have been killed in Germany since 2000, including three who died in a single explosion while trying to defuse a 1,000-pound bomb on the site of a popular flea market in Göttingen in 2010...
> Early one recent winter morning, Horst Reinhardt, chief of the Brandenburg state KMBD, told me that when he started in bomb disposal in 1986, he never believed he would still be at it almost 30 years later. Yet his men discover more than 500 tons of unexploded munitions every year and defuse an aerial bomb every two weeks or so..."
> There Are Still Thousands of Tons of Unexploded Bombs in Germany, Left Over From World War II | History | Smithsonian Magazine


One disturbing article I read stated that on average 2 detonate themselves every year due to corrosion.

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## Zipper730 (Jan 28, 2021)

How many tons of bombs were dropped through the whole of WWII?


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## Koopernic (Jan 28, 2021)

Milosh said:


> Liverpool - Unexploded parachute mine sits in a garden on Score Lane, Childwall. 28 November 1940
> View attachment 610187
> 
> 
> SC2500???


LMB parachute mine targeted at harbours was supposed to self destruct if it missed water.


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## pbehn (Jan 28, 2021)

Koopernic said:


> LMB parachute mine targeted at harbours was supposed to self destruct if it missed water.


Maybe initially, but they were later fitted with a photo electric trigger to kill people trying to defuse them. As previously, there is no harbour in Birmingham or Coventry.


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## YakMan (Jan 28, 2021)

fubar57 said:


> This is the Russian one...
> 
> View attachment 504707
> ​....and the German one
> ...


Ohh! I'd really like a copy of the USSR bomb book - I can't find it in a search - know where it is please? I need to make a replica FAB-50 and FAB-100!


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## fubar57 (Jan 28, 2021)

I'll get back to you, out of town for a few more days. Are you just after the 50 and 100?


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## Dimlee (Jan 28, 2021)

Koopernic said:


> LMB parachute mine targeted at harbours was supposed to self destruct if it missed water.


Or landing in waters too shallow, etc. But, apparently, there were malfunctions. In my home town, LMB has been discovered in the ground in the early 2000s.


pbehn said:


> Maybe initially, but they were later fitted with a photo electric trigger to kill people trying to defuse them. As previously, there is no harbour in Birmingham or Coventry.


Actually most, if not all models were fitted with both. DIfferent mechanisms for different functions: self destruction in case of landing in the wrong place (wrong depth) and self destruction to prevent de-fusing. The latter was optical and called Geheimhaltereinrichtung .
Detailed article in 2 parts. In Russian, but there are English/German language sources in the footnote.
Немецкие морские мины серии ВМ. mormine BM.shtml
Немецкие морские мины серии ВМ. mormine BM.shtml

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## pbehn (Jan 28, 2021)

Dimlee said:


> Or landing in waters too shallow, etc. But, apparently, there were malfunctions. In my home town, LMB has been discovered in the ground in the early 2000s.
> 
> Actually most, if not all models were fitted with both. DIfferent mechanisms for different functions: self destruction in case of landing in the wrong place (wrong depth) and self destruction to prevent de-fusing. The latter was optical and called Geheimhaltereinrichtung .
> Detailed article in 2 parts. In Russian, but there are English/German language sources in the footnote.
> ...


Thanks, however the discussion started about the use of sea mines on land targets, there are as many harbours in Birmingham and Coventry as there are in Moscow, there is no doubt that the LW dropped mines on land targets in UK, I don't know why it is denied, well actually I do, but I don't know why I am expected to believe such nonsense.


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## Koopernic (Jan 29, 2021)

pbehn said:


> Thanks, however the discussion started about the use of sea mines on land targets, there are as many harbours in Birmingham and Coventry as there are in Moscow, there is no doubt that the LW dropped mines on land targets in UK, I don't know why it is denied, well actually I do, but I don't know why I am expected to believe such nonsense.



Do you have primary documents that LMB mines were dropped on inland targets? One can imagine mines hitting parts of say London, Portsmouth, Liverpool the mines that are perhaps off by several Kilometers are perceived as deliberate attacks. In the course of time it becomes assumed that this was the norm.


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## pbehn (Jan 29, 2021)

Koopernic said:


> Do you have primary documents that LMB mines were dropped on inland targets? One can imagine mines hitting parts of say London, Portsmouth, Liverpool the mines that are perhaps off by several Kilometers are perceived as deliberate attacks. In the course of time it becomes assumed that this was the norm.


They fell on Birmingham and Coventry which are about as far from the sea as you can get in England.


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## Koopernic (Jan 29, 2021)

pbehn said:


> They fell on Birmingham and Coventry which are about as far from the sea as you can get in England.


Are you sure


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## pbehn (Jan 29, 2021)

Koopernic said:


> Are you sure


Absolutely BBC - WW2 People's War - Birmingham War Experiences Quote "
In Sutcliffe's book on p.35 I found a reference to a Civil Defence report giving the total of bombs in Birmingham during the war as follows:
"Civil defence reported 5,129 High Explosive bombs of which 930 did not explode. In addition 48 parachute mines of which 16 did not explode".

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## pbehn (Jan 29, 2021)

Koopernic said:


> Are you sure


BBC - WW2 People's War - Parachute Mines In this account it describes bombs being dropped by parachute on Coventry, the sc1800 was a conventional bomb, not a sea mine.


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## Dimlee (Jan 29, 2021)

Was SC1800 used with a parachute ever? I don't see the purpose.


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## pbehn (Jan 29, 2021)

Dimlee said:


> Was SC1800 used with a parachute ever? I don't see the purpose.


An unexploded bomb with a timing device is a bigger nuisance/problem than the bomb itself. If you read the account, large areas of the city were cordoned off and some exploded anyway killing those trying to defuse them, dropped by parachute they were a surface blast which frequently caused more damage than a bomb penetrating the ground.


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## Koopernic (Jan 29, 2021)

Dimlee said:


> Was SC1800 used with a parachute ever? I don't see the purpose.



In the case of bombs with a very light case and therefore a high explosive content it is very likely that the explosives will spill out as the case breaks up on impact before the trigger ignites the primer ignites the explosives. This greatly reduces the effectiveness of the explosion. Also there is a likelihood that the bomb will partially burry itself in soil before triggering which will also absorb its energy. 

Whereas a human parachutist falls at about 25fps (7m/s) these mines fell at either 70fps or 220fps (I've heard both)


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## pbehn (Jan 29, 2021)

Koopernic said:


> In the case of bombs with a very light case and therefore a high explosive content it is very likely that the explosives will spill out as the case breaks up on impact before the trigger ignites the primer ignites the explosives. This greatly reduces the effectiveness of the explosion. Also there is a likelihood that the bomb will partially burry itself in soil before triggering which will also absorb its energy.
> 
> Whereas a human parachutist falls at about 25fps (7m/s) these mines fell at either 70fps or 220fps (I've heard both)


The SC 1800 was just a standard bomb, it was dropped by parachute for terror and disruption not for some theoretical reason of velocity and energy distribution. Yesterday you didn't know it happened now you are explaining the theory of why it did, a while ago you argued that they were naval mines that missed the sea, what is your game here? Parachute mines were and are part of British WW2 folk lore they had a much greater effect on the population's psyche than conventional bombs as you can see if you read the links I posted.

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## Koopernic (Jan 29, 2021)

pbehn said:


> Absolutely BBC - WW2 People's War - Birmingham War Experiences Quote "
> In Sutcliffe's book on p.35 I found a reference to a Civil Defence report giving the total of bombs in Birmingham during the war as follows:
> "Civil defence reported 5,129 High Explosive bombs of which 930 did not explode. In addition 48 parachute mines of which 16 did not explode".



Ok thanks, I accept that parachute bombs were used. You were right. Nice to see some primary documents. There might even be a reference in Wolfgang Fleischers "German Air Dropped Weapons to 1945"

I didn't make this up, A historian at a British Museum mentioned it on YouTube documentary about a month ago as we were debating that Opperation Sea Lion stuff. I think now he was referring only to its initial use in dock attacks during the BoB as bombing escalated on both sides. YouTube deleted my account over some TOS issue and I've lost my history.


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## pbehn (Jan 29, 2021)

Koopernic said:


> Ok thanks, I accept that parachute bombs were used. You were right. Nice to see some primary documents. There might even be a reference in Wolfgang Fleischers "German Air Dropped Weapons to 1945"
> 
> I didn't make this up, A historian at a British Museum mentioned it on YouTube documentary about a month ago as we were debating that Opperation Sea Lion stuff. I think now he was referring only to its initial use in dock attacks during the BoB as bombing escalated on both sides. YouTube deleted my account over some TOS issue and I've lost my history.


Sea mines may have been used initially to mine ports but some missed and it was noted that they were probably more disruptive and destructive dropped at random on cities.


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## Koopernic (Jan 29, 2021)

pbehn said:


> The SC 1800 was just a standard bomb, it was dropped by parachute for terror and disruption not for some theoretical reason of velocity and energy distribution. Yesterday you didn't know it happened now you are explaining the theory of why it did, a while ago you argued that they were naval mines that missed the sea, what is your game here? Parachute mines were and are part of British WW2 folk lore they had a much greater effect on the population's psyche than conventional bombs as you can see if you read the links I posted.



The parachute mines were used to prevent the case from splitting open before detonation or to stop the bomb penetrating the ground before detonation. I think we'll find I will be right on this. Note the British used them as well in the early war years.

Clockwork delays of up to 6 days were fitted to some LMB used over land *but the bulk at least initially exploded on impact or within a about 10 seconds*. Most of the clockwork delays Ive seen in Fleischers German air dropped weapons are for a few minutes to max 2 hours. Keeping the bomb intact so that a time delay may be used was one probable reason but I would refer to it as more a harassment than a terror though I wouldn't deny that there would be a feeling of terror. A parachute bomb, sitting on the surface with its parachute draped around the area with a time delay would very easy to see, walk away from and avoid thereby reducing casualties. One the other hand it would need to be defused or sand bagged meaning that the street, factory etc where it fell could not be opened.

Smaller non parachute retarded bombs such as the SC250 or SC500 often had short time delay fuses (several seconds, these were the electrically programmed fuses) so that if the aircraft was dropping low (which Ju 88 often did) the aircraft could clear the area.

A significant proportion of UXB (a TV drama I remember) would also be just faulty detonators.

There was an attempt by the Luftwaffe to adopt the FuG 101a altimeter into a proximity fuse called Marabu.

The ELAZ electric fuses usually had time delays of less than a second designed to assure penetration but one type could be programmed for around 15 seconds.


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## Koopernic (Jan 30, 2021)

pbehn said:


> Sea mines may have been used initially to mine ports but some missed and it was noted that they were probably more disruptive and destructive dropped at random on cities.



I agree. The story is that after the sea lane and harbour mining campaign against Britain stopped, in part because the British developed several effective anti mine measures such as degaussing, there was a surplus of these mines. The cases were then used over land where they were very effective due to their being able to detonate above ground, their high explosive content and the issues I noted such as not spilling out or burying themselves in soil. The mechanical clockwork timer was latter added as a harassment device.

There was also a parachute adaption known as the SC 1000 parachute. Not sure if this was to ensure above ground detonation of for low level attack purposes.

The LMB was also latter improvised as a parachute delivery container known as a Mischlastabwurfbehelter 1000 with a shock absorber nose. (Mixed load container). There were properly engineered parachute delivery containers for fuel, ammunition, supplies as well, very neat with man transportable containers inside for ammunition, food and fuel. It's said that when Jenkonshenk told Hitler that the 6th Army surrounded at Stalingrad could be supplied by air he had incorrectly assumed the various containers could actually carry in kg the 'number' at the end of the designation. While generally this number refers to the approximate weight of the bomb it more properly refers to the bomb shackles mount. Mischlastabwurfbehelter 1000 certainly couldn't carry 100kg of Ryebread, Bacon and butter. I'm sure there was more too it than that.


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## Zipper730 (Mar 11, 2021)

I forgot about this thread. I should definitely start getting to work on this.


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## Koopernic (Mar 20, 2021)

Zipper730 said:


> From what it appears: The USAAF/USN both employed bomb-fins that used an X-fin arrangement with a box-fin surrounding it (); the RAF used a cylindrical bomb-fin; the Luftwaffe used either X-fins with some designs having a cylindrical fin, at least one having a circular metal connector between the fins; the USSR seeming to use similarities to the Luftwaffe.
> 
> What motivated the decisions for the following
> 
> ...




I can not see the advantage of cylindrical, box or plain fins except maybe strength or some modest length reduction. So long as the fins stabilise the bomb in the forward direction and rotate it slightly so that it evens out any minor differences in manufacturing and it falls in a consistent way it will be enough. The Luftwaffe bombs tended for 4 simple plain fins.

The US M65 500 lb GP bomb if dropped from 20,000ft/6096m at 200mph (90 meters sec) will hit the ground in about 37 seconds as opposed to the 35.2 seconds of the vacuum trajectory. The trail of the bomb under the aircraft in a vacuum would be 3330m and the bomb trail error due to air resistance will be 300m. In other words the bomb trail error is 9% of the vacuum trail and the time to fall is 4.5% longer. There is probably a Coriolis effect as well.

A more aerodynamic bomb with the same weight and half the Cd would roughly halve these percentages. Any variation in air density, manufacturing variation, head wind will have halve the effect of error from those published in the bombs trail error tables.

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## Zipper730 (Jun 12, 2021)

I'm starting to compile stuff. It's not much data so far.


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