delcyros
Tech Sergeant
Hello Juha,
now I understand You, thanks for taking the trouble to explaining this.
For my part, I can also not agree that -speaking from the british perspective- not
seeing the effects of an explosion deep inside the vitals would necessarely force the conclusion that
nothing like this happened. That´s probably a weak part in the discussion, mainly caused by the expectation
that the destruction of boilers under pressure may have caused similar effects to those envisioned on HESSEN, a noticable fuel fire, f.e. to be observd from outside. Boiler explosions may have very shocking effects.
But that doesn´t necessarely be the case under all conditions because the fire would be deep within the vitals of the ship, shielded by at least the Pzdeck, the Splitterlängsschott and the main and upper belt from outside observation.
That beeing said, it´s not the prime reason in the discussion either, Bonomi used the word "interesting" in that context and further cites survivors. The testimonies of these survivors reporting from boiler room one which never said something like a penetration happened is in his and my opinion much more weightful than the missing british observation of eventual effects of the hit.
Altough the Seastate has a fair amount of pitching and rolling on these ship´s fire, the principal reason for the poor hit ratio on both sides,
it´has no effect on a change of the target angle.
The final impact angle is composed of different components:
angle of fall: quite well understood for this range to be 18 deg
target angle: in larger than 70 and not larger than 80 deg
roll: variable (seastate) but typically not more than + or - 4 deg (else bow or stern of the BB´s are completely submerged and DoY would have been unable to fire her fwd battery group)
pitch: variable (seastate) but typically not more than + or -30 deg (else the DD´s are in serious danger of capsizing)
If You assume the best conditions, that are only 70 deg TA and 18 deg aof, the netto obliquity would be 71.02 deg. To much for deep penetration.
If You assume +4 deg pitch, the obliquity raises to 72.37 deg
if You assume -4 deg pitch, the obliquity changes to 69.75 deg
if You assume -4 deg pitch and +30 deg roll the impact obliquity changes to 71.82 deg
if You assume -4 deg pitch and -30 deg roll, the impact obliquity changes to 68.02 deg
if you assume +4 deg pitch and +30 deg roll, the obliquity changes to 70.31 deg
The seastate doesn´t affect rotation of the ship (=target angle). Thus, since it is known that the target angle was larger than 70 deg it´s fairly certain that a penetration at the specific conditions of impact is out of question. The total netto obliquity change at such high target angle´s doesn´t change much from the projectile´s point of view.The fuse delay of british shells was 0.025 sec, the impact velocity at this range varied between 1580 and 1540 fps. It would have been necessary first to defeat the 45mm Wh + 6mm St52 (=48mm Wh single layer) outer hull shell at ca. 70 deg obliquity then the 6mm St52 deck at more than 72 deg obliquity, again a 30mm Wh extra hard splinterbulkhead at ca. 70 deg and the 80mm Wh hump which is 45 to 50ft distant from the hull shell at 70 deg rotational angle. In order to physically hit the hump at 0.025 sec nominal fuse delay You would require either an average velocity of 1800 fps of the projectile or an average velocity in order of 0.035 sec nominal fuse delay, which is much longer than usual (longer than US delays, equal to Krupp Psgr delay) and an average velocity of 1400fps.
That´s really not very likely to expect. Alternatively, a penetration through the 50mm armoured weatherdeck, the the 2.45m interdeck, then the 6mm St52 deck at 70 deg and the hump at ca. 72 is even more complicated and would require 48 to 55 ft delay and is again out of question (the trajectory is also blocked by turret and the armoured rear GCT, which would trigger fuse action of the projectile even earlier).
The energy consumed to penetrate even thin plating at very high obliquity goes rapidly up. A scaled up, 3in M79 AP-shot to 14in and the weight of the british 14in requires in betwee 800 and 1100fps (depending which formula you prefer) for intact penetration at 72 deg of just the 45mm WH and 6mm St52 plating of the outer hull shell. Assuming the lowest number is correct and the best target angle then the projectile has about 1400fps remaining velocity, which means it will never touch the hump. Further high obliquity penetrations further inboard will cause additional deceleration of the shell. The decapped 14in, assuming it behaves similar to the 3in model shot (=1.67crh nose shape while the 14in had 1.6crh, in the same ballpark at the very least) would require in excess of 1600fps to defeat the final, 80mm "hump" Wh plate, which is a significantly higher velocity than the projectile impacted the first plate with and even for a dud projectile should be excluded unless the armour plate is sufficiantly below acceptance minimum quality or the projectile is sufficiently above reference penetration performance.
Note that we already stretched the probability a bit, since the TA was not 70 deg but more acute than 70 deg, other conditions make the penetration appear an even more improbable event. A projectile may, on the other hand, quite handily pass into the region of the boiler uptakes within the margins of fuse delay and penetration envelope. Similar to one of the hits (round 17 first series of trials IIRC) with 15in done on former SMS BADEN. The funnel uptakes were critical components of a ship, rarely ever put under armour (some early US standarts armoured them as thickly as the CT or main belt, for some reason, I guess) other than the thicker than usual armoured gratings. These armoured gratings were successful in limiting the amount of splinters entering the boiler rooms through the holes but they were unable to provide complete ballistic protection and under direct impact shock in a couple of documented cases gave way (they are not pressure proof).
The damage created by the event in my mind speaks against a penetration and wasn´t observed or reported as such. It very well agrees to shock induced or splinter induced damage created by a projectile exploding at or close to the uptakes.
now I understand You, thanks for taking the trouble to explaining this.
For my part, I can also not agree that -speaking from the british perspective- not
seeing the effects of an explosion deep inside the vitals would necessarely force the conclusion that
nothing like this happened. That´s probably a weak part in the discussion, mainly caused by the expectation
that the destruction of boilers under pressure may have caused similar effects to those envisioned on HESSEN, a noticable fuel fire, f.e. to be observd from outside. Boiler explosions may have very shocking effects.
But that doesn´t necessarely be the case under all conditions because the fire would be deep within the vitals of the ship, shielded by at least the Pzdeck, the Splitterlängsschott and the main and upper belt from outside observation.
That beeing said, it´s not the prime reason in the discussion either, Bonomi used the word "interesting" in that context and further cites survivors. The testimonies of these survivors reporting from boiler room one which never said something like a penetration happened is in his and my opinion much more weightful than the missing british observation of eventual effects of the hit.
Altough the Seastate has a fair amount of pitching and rolling on these ship´s fire, the principal reason for the poor hit ratio on both sides,
it´has no effect on a change of the target angle.
The final impact angle is composed of different components:
angle of fall: quite well understood for this range to be 18 deg
target angle: in larger than 70 and not larger than 80 deg
roll: variable (seastate) but typically not more than + or - 4 deg (else bow or stern of the BB´s are completely submerged and DoY would have been unable to fire her fwd battery group)
pitch: variable (seastate) but typically not more than + or -30 deg (else the DD´s are in serious danger of capsizing)
If You assume the best conditions, that are only 70 deg TA and 18 deg aof, the netto obliquity would be 71.02 deg. To much for deep penetration.
If You assume +4 deg pitch, the obliquity raises to 72.37 deg
if You assume -4 deg pitch, the obliquity changes to 69.75 deg
if You assume -4 deg pitch and +30 deg roll the impact obliquity changes to 71.82 deg
if You assume -4 deg pitch and -30 deg roll, the impact obliquity changes to 68.02 deg
if you assume +4 deg pitch and +30 deg roll, the obliquity changes to 70.31 deg
The seastate doesn´t affect rotation of the ship (=target angle). Thus, since it is known that the target angle was larger than 70 deg it´s fairly certain that a penetration at the specific conditions of impact is out of question. The total netto obliquity change at such high target angle´s doesn´t change much from the projectile´s point of view.The fuse delay of british shells was 0.025 sec, the impact velocity at this range varied between 1580 and 1540 fps. It would have been necessary first to defeat the 45mm Wh + 6mm St52 (=48mm Wh single layer) outer hull shell at ca. 70 deg obliquity then the 6mm St52 deck at more than 72 deg obliquity, again a 30mm Wh extra hard splinterbulkhead at ca. 70 deg and the 80mm Wh hump which is 45 to 50ft distant from the hull shell at 70 deg rotational angle. In order to physically hit the hump at 0.025 sec nominal fuse delay You would require either an average velocity of 1800 fps of the projectile or an average velocity in order of 0.035 sec nominal fuse delay, which is much longer than usual (longer than US delays, equal to Krupp Psgr delay) and an average velocity of 1400fps.
That´s really not very likely to expect. Alternatively, a penetration through the 50mm armoured weatherdeck, the the 2.45m interdeck, then the 6mm St52 deck at 70 deg and the hump at ca. 72 is even more complicated and would require 48 to 55 ft delay and is again out of question (the trajectory is also blocked by turret and the armoured rear GCT, which would trigger fuse action of the projectile even earlier).
The energy consumed to penetrate even thin plating at very high obliquity goes rapidly up. A scaled up, 3in M79 AP-shot to 14in and the weight of the british 14in requires in betwee 800 and 1100fps (depending which formula you prefer) for intact penetration at 72 deg of just the 45mm WH and 6mm St52 plating of the outer hull shell. Assuming the lowest number is correct and the best target angle then the projectile has about 1400fps remaining velocity, which means it will never touch the hump. Further high obliquity penetrations further inboard will cause additional deceleration of the shell. The decapped 14in, assuming it behaves similar to the 3in model shot (=1.67crh nose shape while the 14in had 1.6crh, in the same ballpark at the very least) would require in excess of 1600fps to defeat the final, 80mm "hump" Wh plate, which is a significantly higher velocity than the projectile impacted the first plate with and even for a dud projectile should be excluded unless the armour plate is sufficiantly below acceptance minimum quality or the projectile is sufficiently above reference penetration performance.
Note that we already stretched the probability a bit, since the TA was not 70 deg but more acute than 70 deg, other conditions make the penetration appear an even more improbable event. A projectile may, on the other hand, quite handily pass into the region of the boiler uptakes within the margins of fuse delay and penetration envelope. Similar to one of the hits (round 17 first series of trials IIRC) with 15in done on former SMS BADEN. The funnel uptakes were critical components of a ship, rarely ever put under armour (some early US standarts armoured them as thickly as the CT or main belt, for some reason, I guess) other than the thicker than usual armoured gratings. These armoured gratings were successful in limiting the amount of splinters entering the boiler rooms through the holes but they were unable to provide complete ballistic protection and under direct impact shock in a couple of documented cases gave way (they are not pressure proof).
The damage created by the event in my mind speaks against a penetration and wasn´t observed or reported as such. It very well agrees to shock induced or splinter induced damage created by a projectile exploding at or close to the uptakes.
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