Blast From the Past II

The Discussion Board For The True Queen Of The Seas
Joined: February 26th, 2007, 7:57 am

June 13th, 2018, 10:13 pm #11

As before, regarding potential impact angles -- and neglecting the fact that the impact velocities and angles of impact quoted can not be brought into congruence with actual range tables to begin with -- my statement was not that such low impact angles were impossible, only that they were highly improbable.  

As an example, in one posting it was suggested that a list (or heel) of 9 degrees away could make a 10 degree obliquity performance relevant.  If such occurred, it would in any case to be more likely -- at least in the later stages of an action -- to be towards rather than away from one's enemy, and would -- if roll is the issue -- only apply for a relatively short period of time compared to the period when the roll was less than that.  I personally would place that situation in the category of 'highly contrived.

The 9 degree example represents, in any case, a rather large value.  For many battleships (admittedly using normal drafts)  a heel of 9 degree would bring the lower edge of the vertical belt out of the water, or nearly so.   In that sort of situation,  I would suggest that the threat to survival would be much more likely to revolve around a the possibility of a direct penetration of the unarmored shell below the belt rather than some nuance of extra penetration of the belt itself.

The utility of enhanced penetrations revolving around the metallurgical constitution of the impacting projectile cannot generally be accurately measured via proving ground acceptance tests. The impact obliquity and striking velocity combinations used in acceptance testing are in most cases not designed to reflect actual range table conditions at all, but instead are built around the ability to meet or exceed a collection of somewhat artificial (and often arbitrary) sets of conditions arrived at by negotiation between the manufacturer and the customer of the product. 

While it's tempting to assume that 'better' performance in meeting these somewhat artifical armor plate acceptance tests will also be expressed as better performance in actual combat, there is in most cases little concrete evidence that this hypothesis is actually valid, except perhaps accidentally. While performing better under a set of conditions "a" may imply better performance under a set of conditions 'b', actual experience will show that this is often not the case.

Bill Jurens
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Joined: April 23rd, 2011, 5:01 pm

June 14th, 2018, 2:06 am #12

Ikeda - You are embarrassing yourself.
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Joined: May 3rd, 2011, 1:03 pm

June 14th, 2018, 8:24 am #13

So far it seems to have been assumed that we are talking about opposing fleets engaging more or less beam on. Chases were much more common in WW1. Here obliquities were quite high, for instance 45 to 55 deg at Dogger Bank. In these situations penetrations of turrets and barbettes were much more common than belt penetrations,

Neil Robertson
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Joined: May 5th, 2018, 1:11 pm

June 14th, 2018, 1:25 pm #14

55 degrees is far from 10
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Joined: April 23rd, 2011, 5:01 pm

June 14th, 2018, 2:40 pm #15

Net angle of obliquity is a geometric function of projectile angle of fall, line of fire relative to target heading, relative angularity of the plate (inclination, barbette curvature), target motion (roll/yaw).  Average net obliquities are probably in the range of 30-40deg at typical WW1 battle ranges.  Penetrative behavior of AP projectiles, particularly those of early design, can differ dramatically as obliquity increases.  Hence, any comparison of different projectiles at a single and relatively modest obliquity is, practically speaking, a woefully inadequate measure in terms of their performance under real world battle conditions.
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Joined: May 5th, 2018, 1:11 pm

June 14th, 2018, 4:57 pm #16

I bet if I hit a superstructure with a 12 inch shell it the shell would penetrate it.
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Joined: February 16th, 2007, 11:10 pm

June 14th, 2018, 6:12 pm #17

GrandGulf wrote: I bet if I hit a superstructure with a 12 inch shell it the shell would penetrate it.
Don't be silly!  In Ikeda-land, US ships only get hit in the main belt...
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Joined: February 10th, 2010, 3:58 pm

June 15th, 2018, 4:30 pm #18

Blutarski wrote: Net angle of obliquity is a geometric function of projectile angle of fall, line of fire relative to target heading, relative angularity of the plate (inclination, barbette curvature), target motion (roll/yaw).  Average net obliquities are probably in the range of 30-40deg at typical WW1 battle ranges.  Penetrative behavior of AP projectiles, particularly those of early design, can differ dramatically as obliquity increases.  Hence, any comparison of  different projectiles at a single and relatively modest obliquity is, practically speaking, a woefully inadequate measure in terms of their performance under real world battle conditions.
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Regardless of the range or obliquity and regardless of the measure of performance used, the US 14” shell will outperform the German 12” shell and the US 16” shell will outperform the German 15” shell. Physics.

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Joined: April 23rd, 2011, 5:01 pm

June 16th, 2018, 1:31 am #19

Ikeda wrote -
"Regardless of the range or obliquity and regardless of the measure of performance used, the US 14” shell will outperform the German 12” shell and the US 16” shell will outperform the German 15” shell. Physics."


..... Physics is a harsh mistress.  The US projectile proof performance you cite at 10deg obliquity is fine as far as it goes, but it represents an artificially established proving ground case.  A projectile impact of </= 10deg under combat conditions is rare; average striking obliquities under combat conditions are more on the order of 30deg.  And herein lies the problem.  Given the historical period under discussion, there is no guarantee that the performance hierarchy you posit will remain consistent at higher angles of obliquity.  It is a demonstrable fact that British Jutland era APC striking KC plate =/> 1/3 caliber thickness would tend to break up at obliquities of 15deg and would be almost certain to do so at an obliquity of 20deg or more - irrespective of striking velocity; they might hole the plate in the process, but the greater part of the projectile effect would be wasted outside the face of the plate.  In comparison, given sufficient striking velocity, contemporaneous German APC would reliably pass intact through plate up to 1/2 caliber at 30deg obliquity (which was the German projectile proof standard).

Until you can present proper data on the performance of the American WW1 AP projectiles in question at these higher obliquities, it is simply not possible to declare any sort of comprehensive superiority for the WW1 era American AP projectile design under combat conditions.

As you were so kind to point out, it all depends upon the physics.

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Joined: February 10th, 2010, 3:58 pm

June 16th, 2018, 12:27 pm #20

Blutarski wrote: Ikeda wrote -
"Regardless of the range or obliquity and regardless of the measure of performance used, the US 14” shell will outperform the German 12” shell and the US 16” shell will outperform the German 15” shell. Physics."


..... Physics is a harsh mistress.  The US projectile proof performance you cite at 10deg obliquity is fine as far as it goes, but it represents an artificially established proving ground case.  A projectile impact of </= 10deg under combat conditions is rare; average striking obliquities under combat conditions are more on the order of 30deg.  And herein lies the problem.  Given the historical period under discussion, there is no guarantee that the performance hierarchy you posit will remain consistent at higher angles of obliquity.  It is a demonstrable fact that British Jutland era APC striking KC plate =/> 1/3 caliber thickness would tend to break up at obliquities of 15deg and would be almost certain to do so at an obliquity of 20deg or more - irrespective of striking velocity; they might hole the plate in the process, but the greater part of the projectile effect would be wasted outside the face of the plate.  In comparison, given sufficient striking velocity, contemporaneous German APC would reliably pass intact through plate up to 1/2 caliber at 30deg obliquity (which was the German projectile proof standard).

Until you can present proper data on the performance of the American WW1 AP projectiles in question at these higher obliquities, it is simply not possible to declare any sort of comprehensive superiority for the WW1 era American AP projectile design under combat conditions.

As you were so kind to point out, it all depends upon the physics.

B
Just because a shell breaks up doesn't mean it won't penetrate and cause damage. Nathan has data on hundreds of test impacts at different impact obliquities that show just what various shells are capable of.
Half caliber penetration of a 12" shell means that they could not even penetrate the 6.5" upper casemate armor of a US ship unbroken at 30 degrees obliquity. A 14" US shell penetrating broken will do more damage than a 12" broken German shell, and a 16" broken US shell will do more damage than a 15" German broken shell.
I stand by my previous statement.
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