delcyros
Tech Sergeant
Thanks for the hint. I am looking forward for the "frame by frame" armor scheme drawings of these books (I think we have it here in the library).
German Battleships and convoy hunting.
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delcyros
Tech Sergeant
Got it.
And I also found a verification for the latent weakness of the torpedo defense system of US fast battleships:
The failure of Washingtons TDS between turret A and B led to the idea to improve the TDS of the Iowa by adding some extensive blisters between turret A and B (and some more forward). This could have fixed the TDS weaknes there but for some uncomfortable costs:
Most concerning is the negative effect in hull drag coefficient, reducing the top speed by between 1.2 and 1.8 kts.
But even more worrisome is that by doing this the pressure curve of the longitudinal CoB would have been shifted more aft. In the end this would have considerably decreased the seakeeping abilities of all Iowas in heavy seas by increasing the downward pull of the bow! Gurgle, gurgle.
Ahh. Some more very interesting informations provided by Nathan Okun shows that the decapping plate on Iowa and South Dakota WILL NOT DECAP a german 14.96" AP PzSprGr. 38.
Originally he simply assumed that 0.0805 calibre thicknesses of STS or comparable homogenious steel will always decap an AP projectile
(in case of Bismarcks guns: 1.205" would decap the AP. Soth Dakota has a plating of 1.25" and Iowa 1.5") Deeper investigations by Nathan Okun proved that this only belongs to soft capped AP(type 1), not hardened AP-caps.
With his corrections it would need between 0.12 and 0.14 calibre thicknesses to have a 50% chance to decap (1.8") type 2= hardened AP(compare attached image). This means the decapping plate of Iowa/South Dakota WILL ALWAYS FAIL to decap the 15" AP.
This would also effect the calculations of combinedfleet.com. The 15" AP of Bismarck will effectively penetrate Iowa and South Dakota at even longer ranges!!! It means the 15"ers will penetrate in effective conditions (EEF, formerly not possible due to decapping effect) the belt. This offsets one of the most striking advantages of South Dakota/Iowa. I have to recalculate belt penetrations
And I also found a verification for the latent weakness of the torpedo defense system of US fast battleships:
The failure of Washingtons TDS between turret A and B led to the idea to improve the TDS of the Iowa by adding some extensive blisters between turret A and B (and some more forward). This could have fixed the TDS weaknes there but for some uncomfortable costs:
Most concerning is the negative effect in hull drag coefficient, reducing the top speed by between 1.2 and 1.8 kts.
But even more worrisome is that by doing this the pressure curve of the longitudinal CoB would have been shifted more aft. In the end this would have considerably decreased the seakeeping abilities of all Iowas in heavy seas by increasing the downward pull of the bow! Gurgle, gurgle.
Ahh. Some more very interesting informations provided by Nathan Okun shows that the decapping plate on Iowa and South Dakota WILL NOT DECAP a german 14.96" AP PzSprGr. 38.
Originally he simply assumed that 0.0805 calibre thicknesses of STS or comparable homogenious steel will always decap an AP projectile
(in case of Bismarcks guns: 1.205" would decap the AP. Soth Dakota has a plating of 1.25" and Iowa 1.5") Deeper investigations by Nathan Okun proved that this only belongs to soft capped AP(type 1), not hardened AP-caps.
With his corrections it would need between 0.12 and 0.14 calibre thicknesses to have a 50% chance to decap (1.8") type 2= hardened AP(compare attached image). This means the decapping plate of Iowa/South Dakota WILL ALWAYS FAIL to decap the 15" AP.
This would also effect the calculations of combinedfleet.com. The 15" AP of Bismarck will effectively penetrate Iowa and South Dakota at even longer ranges!!! It means the 15"ers will penetrate in effective conditions (EEF, formerly not possible due to decapping effect) the belt. This offsets one of the most striking advantages of South Dakota/Iowa. I have to recalculate belt penetrations
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delcyros
Tech Sergeant
Ok-here it goes:
South Dakota vs 14.96"/52 AP 1764 lbs (1552 lbs body weight).
1.1.) armor layout (compare attached picture):
outer hull: unarmored (0.3" STS)
decapping plate: 1.25" STS
main belt: 12.2" US class"A" face hardened, 19.9 degrees inclined
(lower) main belt: tapered down gradually from 11" to 0.7" at the bottom
weather deck: 1.5" US class "B" homogenious
main deck: 5.3" US class "B" homogenious
splinter deck: 0.625" STS
splinter belt/decks: 0.3" STS
Now we assume that deck penetration isn´t possible in our ranges (I exclude all ranges beyond 30.000 yrds because of obvious reasons). Belt penetrations are therfor the only possibility to reach Iowa´s / South Dakotas vitals:
lets check 10.000 yrds: the striking velocity is 2160 fps at AoF 5.8 degrees. The shell will went through the outer hullskin and loose its windscreen(no significant loss in striking velocity and AoF), leaving a hole. In case this hole is in the waterline or in the pressurewave, it will cause flooding and contamining oilreserves with seawater.
Next is the decapping plate. According to Okun the decapping plate FAILS to decap the 15" AP (as it would fail to decap 11"ers and even 8"ers AP-caps). The shell will reamin intact AP-cap and 2151 fps. It´s base fuze will be set by defeating the decapping plate, AoF still the same.
Now it can defeat the 12.2", 19 degrees inclined face hardened class"A" belt with ease. Obliquity is 25.3 degrees, remaining striking velocity will be around 741 fps, so the shell may travel betwen 15 and 22 ft behind the armor plate before detonating at normal fuze delay.
AT which distance will the belt prevent penetration?
The holing limit will be reached at 19.400 yrds. The Navy Ballistic limit with full penetration may occur at 16.400 yrds (nose shattered), so if we take longitudinal impact angles also into consideration the South Dakota will be hurt at all distances under 15.000 yrds for sure, Iowa at all under 14.800 yrds. This makes for a pretty large immune gap from 0-15.000 yrds, where Iowa´s and South Dakotas vitals are totally exposed to Bismarck´s 15" guns! In order to ensure decaping the 15"ers they would need a 2.54" STS decapping plate instead of the 1.25" or 1.5" plates. In opposition to this Iowa would have been better protected in case they removed completely the 1.5" STS plate for beefing up the main belt to 13.3" class "A"(this would close the immune gap to 0-13000 yrds). But I suspect this wasn´t possible due to concernings regarding longitudinal hull stiffness (which is -for my knowledge- the originally intendet reason for the 1.5" plate).
South Dakota vs 14.96"/52 AP 1764 lbs (1552 lbs body weight).
1.1.) armor layout (compare attached picture):
outer hull: unarmored (0.3" STS)
decapping plate: 1.25" STS
main belt: 12.2" US class"A" face hardened, 19.9 degrees inclined
(lower) main belt: tapered down gradually from 11" to 0.7" at the bottom
weather deck: 1.5" US class "B" homogenious
main deck: 5.3" US class "B" homogenious
splinter deck: 0.625" STS
splinter belt/decks: 0.3" STS
Now we assume that deck penetration isn´t possible in our ranges (I exclude all ranges beyond 30.000 yrds because of obvious reasons). Belt penetrations are therfor the only possibility to reach Iowa´s / South Dakotas vitals:
lets check 10.000 yrds: the striking velocity is 2160 fps at AoF 5.8 degrees. The shell will went through the outer hullskin and loose its windscreen(no significant loss in striking velocity and AoF), leaving a hole. In case this hole is in the waterline or in the pressurewave, it will cause flooding and contamining oilreserves with seawater.
Next is the decapping plate. According to Okun the decapping plate FAILS to decap the 15" AP (as it would fail to decap 11"ers and even 8"ers AP-caps). The shell will reamin intact AP-cap and 2151 fps. It´s base fuze will be set by defeating the decapping plate, AoF still the same.
Now it can defeat the 12.2", 19 degrees inclined face hardened class"A" belt with ease. Obliquity is 25.3 degrees, remaining striking velocity will be around 741 fps, so the shell may travel betwen 15 and 22 ft behind the armor plate before detonating at normal fuze delay.
AT which distance will the belt prevent penetration?
The holing limit will be reached at 19.400 yrds. The Navy Ballistic limit with full penetration may occur at 16.400 yrds (nose shattered), so if we take longitudinal impact angles also into consideration the South Dakota will be hurt at all distances under 15.000 yrds for sure, Iowa at all under 14.800 yrds. This makes for a pretty large immune gap from 0-15.000 yrds, where Iowa´s and South Dakotas vitals are totally exposed to Bismarck´s 15" guns! In order to ensure decaping the 15"ers they would need a 2.54" STS decapping plate instead of the 1.25" or 1.5" plates. In opposition to this Iowa would have been better protected in case they removed completely the 1.5" STS plate for beefing up the main belt to 13.3" class "A"(this would close the immune gap to 0-13000 yrds). But I suspect this wasn´t possible due to concernings regarding longitudinal hull stiffness (which is -for my knowledge- the originally intendet reason for the 1.5" plate).
Attachments
Henk
Master Sergeant
Very interesting mate, but some of it is a bit to technical for my brain, it still very nice and a great help.
Henk
Henk
delcyros
Tech Sergeant
My fault. I like to dig into technical details. Originally wanted to point out that the highly reputated decapping plate wouldn´t positively effect belt protection, it was too thin to do so. The Littorio class BB was the only BB to use (and it´s designers proofed to understand) the benfits of a decapping plate. They used a 70 mm homogenious armor grade plate instead of 32mm (South Dakota) and 38 mm (Iowa) of STS. They would succesfully remove the AP-caps of all allied guns. Only Yamato´s 18.1"ers will have a 40% chance to remain it´s AP-cap. And without AP-cap, the armor penetration abilities of the main projectile is 1.) greatly reduced (we are talking about a maximum loss of around 35% at direct and gradually lowering to 8% at high obliquities) and 2.) the shell is very likely to shatter (which may render the cavity charge useless but doesn´t prevent from penetrating).
Henk
Master Sergeant
How did they decap the plates? Great info mate, this will help me quite a lot.
Henk
Henk
delcyros
Tech Sergeant
The shell don´t decap the plate. The plate decaps the shell!
This has to do with shell design. Shortly before WW1 the german high sea fleet introduced the armor peircing cap to it´s shells. The contemporary british shells had a simple, homogenious shell body. The benefits of armor piercing caps have to do with the usual armor type of those times: The face hardened armor (call for Krupp). It´s outer layer (face) was hardened to over 600 Brinell, sometimes even 700 and more (which is close to crystaline or cementated). This ultra hard face will damage a hitting projectile and usually break it´s nose (and sometimes renders its cavity useless). The AP cap attached to the nose of the shell will hit the ultra hard face earlier and destroy the thin cementated layer, allowing the main projectile body to penetrate in intact condition and to penetrate deeper (the backing layers were gradually tapered down to around 260-300 Brinell causing less resistance).
The first to develop a AP-counter armor layout (and the only in ww2) were the italian with their special high tensile 70 mm decapping plate placed 1.4-2.2 m in front of the main belt. This plate has enough resistance (compare the necessary plate thickness with Okuns table above) to strip off the AP-cap of any gunsize under 18" before it will reach the main belt. Such an uncapped projectile will now again suffer nose shatter and all the disadvantages common for shell without AP-cap against the face hardened armor.
This has to do with shell design. Shortly before WW1 the german high sea fleet introduced the armor peircing cap to it´s shells. The contemporary british shells had a simple, homogenious shell body. The benefits of armor piercing caps have to do with the usual armor type of those times: The face hardened armor (call for Krupp). It´s outer layer (face) was hardened to over 600 Brinell, sometimes even 700 and more (which is close to crystaline or cementated). This ultra hard face will damage a hitting projectile and usually break it´s nose (and sometimes renders its cavity useless). The AP cap attached to the nose of the shell will hit the ultra hard face earlier and destroy the thin cementated layer, allowing the main projectile body to penetrate in intact condition and to penetrate deeper (the backing layers were gradually tapered down to around 260-300 Brinell causing less resistance).
The first to develop a AP-counter armor layout (and the only in ww2) were the italian with their special high tensile 70 mm decapping plate placed 1.4-2.2 m in front of the main belt. This plate has enough resistance (compare the necessary plate thickness with Okuns table above) to strip off the AP-cap of any gunsize under 18" before it will reach the main belt. Such an uncapped projectile will now again suffer nose shatter and all the disadvantages common for shell without AP-cap against the face hardened armor.
Attachments
Henk
Master Sergeant
Thanks for the info mate.
Henk
Henk
