American SH shells - Famed or Folly

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Ski206
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Re: American SH shells - Famed or Folly

Post by Ski206 » Fri Oct 18, 2019 9:15 pm

I think that what is being missed in this discussion are the negatives associated with light weight high velocity projectiles. Look at the RN experience with the 16” MK 1 guns kn the Nelson which had a light projectile and high velocity. In service this gun had issues with rapid barrel wear leading to poor accuracy and the RN planned to go back to a heavy projectile/low velocity combination for the Lion class.

Given when the guns on the Nelson entered service we can strongly suspect that BuOrd in the US was aware of the issues they were having.

Additionally recall that the 16”45 and 16”50 were originally intended to use the 2240lb armor piercing round then in service. What the SH shell offered was the ability to significantly increase the penetration power of a gun that was already designed. For example at 20,300 yds the 16” MK 5 as fitted to the Colorado class firing the 2240 lb AP shell could penetrate 16” of armor. By contrast the NC class with the 16” MK 8 with the 2700lb AP shell could penetrate 17.62” at 20,000 yds. So in guns with comparable performance the new shell bought another 1.5” (rough figures due to range differences) or so of penetration.

Consider too the design of the South Dakota class ships. The NC had been originally designed around a 14” gun and when up-gunned to 16” was considered unbalanced. The South Dakota class was intended to be a balanced 35,000 ton treaty battleship with the 16”45 2240lb combination. But when BuOrd developed the 2700lb SH AP shell both it and the Iowa’s were essentially unbalanced as a result. The desire to have a properly balanced ship against the 16”50 2700lb was one of the major drivers behind the Montana class.

Lastly consider the fact that BuOrd did trial and 18” gun and developed a SH shell for that gun which it also trialed. And yet even in a post treaty world they felt that the 16”50 2700lb was such a destructive and well balanced combination that they didn’t need to move beyond it.

The real genius of the SH shells and the reason why it’s utter nonsense to call them folly is that they took existing guns and significantly improved their penetration without creating other negative affects. The SH shells were simply better period. And to quote NavWeaps “These conclusions led to the development of "Super-Heavy" AP projectiles in the late 1930s, which made the US guns using them superior to other nation's weapons of the same caliber.” Something true not only of the 16” battleship rifles but also the 8” guns on most US Heavy Cruisers. Though I don’t have I data I suspect the same was true of the 6” gun as well.

So Farmed or Folly? I would say it was a great folly to argue that their fame isn’t well deserved.

Ski206
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Re: American SH shells - Famed or Folly

Post by Ski206 » Sat Oct 19, 2019 4:38 pm

I think a quote from the Navweaps page on the British 18” guns designed for the N3 battleships is particularly interesting.

“The original 18" (45.7 cm) APC shell weight was decided upon in August 1920. Shortly afterwards, from a series of gunnery trials, a mistaken theory was conceived that held that a high-velocity, low-weight projectile would have superior oblique impact armor penetration characteristics, which was the opposite of previous findings. As a result of this new theory, the APC projectiles were redesigned in 1921 for a significantly lighter shell weight. This theory was not substantiated by later trials, but these took place too late to affect the decision to use light weight APC projectiles.”

So what we see is that a heavier lower velocity shell has better oblique impact penetration when compared to a light weight high velocity shell. Which would again point to the fact that BuOrd was on the right path with the SH shells.

Thorsten Wahl
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Re: American SH shells - Famed or Folly

Post by Thorsten Wahl » Tue Oct 29, 2019 8:14 am

A superheavy projectile held some outer ballistics advantages but,

U.S. Navy F-function wich was used for prediction of penetration in american fireeffect tables(Ordnance Sketch 78841) tend to predict a too low critical velocity for penetration at all impact angles above 20 degrees. The error was in the magnitude of about 10 to 15 % velocity at 60 degrees obliquity.

The "real superheavy advantage" came from mostly from the facts that a superheavy projectile retains more kinetic energy and the obliquity advantage at long range against horizontal targets.
lower impact speeds also reduce the likehood of (early)shatter.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: American SH shells - Famed or Folly

Post by Dave Saxton » Tue Oct 29, 2019 2:24 pm

The important factors affecting oblique penetration performance have to do the head shape.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

Thorsten Wahl
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Re: American SH shells - Famed or Folly

Post by Thorsten Wahl » Tue Oct 29, 2019 2:47 pm

addition to the previously said
Headshape dependend angular performance.jpg
Headshape dependend angular performance.jpg (55.54 KiB) Viewed 573 times
additionally the heavy armor-piercing-cap used supports penetration at high obliquities compared to no cap or relatively lighter caps.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: American SH shells - Famed or Folly

Post by Thorsten Wahl » Wed Oct 30, 2019 10:07 am

a question does someone know the CRH of the windscreen of the 2240 lb and 2700 lb US AP-shells
sample german L/3,7 Psgr had 8,5 cal
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Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

Ski206
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Re: American SH shells - Famed or Folly

Post by Ski206 » Thu Nov 07, 2019 5:28 pm

Thorsten Wahl wrote:
Tue Oct 29, 2019 8:14 am
A superheavy projectile held some outer ballistics advantages but,

U.S. Navy F-function wich was used for prediction of penetration in american fireeffect tables(Ordnance Sketch 78841) tend to predict a too low critical velocity for penetration at all impact angles above 20 degrees. The error was in the magnitude of about 10 to 15 % velocity at 60 degrees obliquity.

The "real superheavy advantage" came from mostly from the facts that a superheavy projectile retains more kinetic energy and the obliquity advantage at long range against horizontal targets.
lower impact speeds also reduce the likehood of (early)shatter.
So your saying the SH shell is better than the alternative?

I’m not familiar with the F-function you mention so I’m not sure why the but. Are you suggesting the brits were wrong and the lighter higher velocity shell would have been better at oblique penetration?

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Re: American SH shells - Famed or Folly

Post by Byron Angel » Fri Nov 08, 2019 1:36 am

When considering the design evolution of USN super-heavy projectiles, it is worth noting the increasing bluntness of the nose, which yielded a shorter projectile length. For any given caliber, a shorter projectile length would reduce the bending stresses introduced by oblique impact upon the projectile body.

FWIW.

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Re: American SH shells - Famed or Folly

Post by Byron Angel » Fri Nov 08, 2019 2:41 am

Thorsten Wahl wrote:
Tue Oct 29, 2019 8:14 am
A superheavy projectile held some outer ballistics advantages but,

U.S. Navy F-function wich was used for prediction of penetration in american fireeffect tables(Ordnance Sketch 78841) tend to predict a too low critical velocity for penetration at all impact angles above 20 degrees. The error was in the magnitude of about 10 to 15 % velocity at 60 degrees obliquity.

The "real superheavy advantage" came from mostly from the facts that a superheavy projectile retains more kinetic energy and the obliquity advantage at long range against horizontal targets.
lower impact speeds also reduce the likehood of (early)shatter.

Hi Thorsten,
You wrote - "The error was in the magnitude of about 10 to 15 % velocity at 60 degrees obliquity."
Am I correct that you are referencing that 60deg obliquity angle to the plane of the plate? i.e. - addressing the issue of penetration of horizontal armor? IIRC, the F-function was related to the Thompson AP formula; would I also be correct in my understanding that the performance over-estimate would apply to all types of projectiles evaluated under the conditions you describe and would not have been unique to the super-heavy projectile?

If so, based upon the performance data given in USD 1944 range tables, the move to the super-heavy projectile design format seems to have made sense. For example - consider the performance of the 2700lb and 2240lb AP projectiles of the USN 16in/45 gun:

16in/45 / W = 2700 lbs / MV = 2300 fps
AoF @ 20,000 yds = 17.9 deg
ToF @ 20,000 yds = 32.55 sec
S V @ 20,000 yds = 1604 fps

16in/45 / W = 2240 lbs / MV = 2520 fps
AoF @ 20,000 yds = 16.3 deg
ToF @ 20,000 yds = 30.58 sec
S V @ 20,000 yds = 1629 fps

... which gave the 2700 lb projectile (@ 20,000 yards) a superiority in Striking Energy of 17 percent along with a designed ability for intact penetration of vertical armor at ~35 degree obliquity as opposed to 15 degrees for the older projectile design, not to mention an assumed extension of gun tube life due to the reduced MV.

A complicated issue to be sure!


Byron

Thorsten Wahl
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Re: American SH shells - Famed or Folly

Post by Thorsten Wahl » Fri Nov 08, 2019 1:10 pm

Am I correct that you are referencing that 60deg obliquity angle to the plane of the plate? i.e. - addressing the issue of penetration of horizontal armor?
yes.
------------------------------------------------------------------------------------------------------------------------------------------------------
using metrics data from navweaps expected penetration performance according Thompson Formula (= F formula = US empirical)
projectilemass-muzzle velocity-muzzle energy-calculated-------------
--------------------------------------------------------penetration at muzzle
1016 kg ---------768 m/s --------------~300 MJ---------754 mm
1225 kg ---------701 m/s --------------~300 MJ---------755 mm
edit german
800 kg------------820 m/s---------------~269 MJ------- ~800 mm (based on Gercke formula but completely out of bounds of validity)


if all guns had the same same max elevation of 45 degrees the lighter US-projectile would have a range of about 36,6 km the SH projectile 33,7 km and the german projectile ~42 km

at ~32 km(35 kyard) range expected performance
-------------impact condition ----flighttime----vertical pen----horizontal pen
1016 kg----453m/s at 40° AOF---~70 sec-------254 mm---------207 mm
1225 kg----488m/s at 44° AOF--~78 sec-------266 mm----------268 mm
800 kg------457 m/s at 35°AOF--~61 sec------256 mm----------144 mm
performancewise the superheavy AP-shell appears as the somewhat favourable choice.
but requires a reduction of number of shells carried by the ship for the same displacement.
-----------------------------------------------------------------------------------------------------------------------------------------------------
from my personal point of view a flightime of more than one minute should be taken as unrealistic with regards to hitting probabilities, as the target had ample of time to outmaneuver the firing solution, but fluke hits may be possible

I would consider flightimes of about 30 - 40 seconds as "realistic" for unguided projectiles to hit a moving target.
so we are moving into the 18,5km(20 kyard)-22,7 km(25 kyard) distance bracket.

expected performance using F-Formula for US projectiles and Gercke Formula for german projectile
------------------ at ~18,5 km----------------------------~22,7 km
------------vertical pen---horizontal pen---vertical pen------horizontal pen
1016 kg---412 mm----------90 mm-----------349 mm------------121 mm
1225 kg---448 mm---------109 mm-----------382 mm------------146 mm
800 kg----435 mm---------<80 mm-----------362 mm--------------90 mm
even the superheavy shell had about 25,5 degrees AOF at 22 km.

As i said before there are problems with the calculated performance( thompson F-Formula) of the projectiles compared to real performance at high obliquity as well as problems with the performance of american FH-armor at low obliquity.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: American SH shells - Famed or Folly

Post by Thorsten Wahl » Mon Nov 18, 2019 12:47 pm

british comment in SUPP 6/481
SUPP 6-481 _section_Effect of weight.jpg
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Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: American SH shells - Famed or Folly

Post by paul.mercer » Fri Nov 22, 2019 5:17 pm

Consider too the design of the South Dakota class ships. The NC had been originally designed around a 14” gun and when up-gunned to 16” was considered unbalanced. The South Dakota class was intended to be a balanced 35,000 ton treaty battleship with the 16”45 2240lb combination. But when BuOrd developed the 2700lb SH AP shell both it and the Iowa’s were essentially unbalanced as a result. The desire to have a properly balanced ship against the 16”50 2700lb was one of the major drivers behind the Montana class.

Gentlemen, please excuse my ignorance in this, but what is meant by being 'balanced', is it the size and weight of the gun and turret against the size of the ship or the shell balanced in flight, against the length of the rifling of the barrel or what?
Would I be correct in assuming that the longer 16x50 was better at stabilizing the heavier shell
I always thought that the 'Montana's were basically enlarged 'Iowa's with 12 instead of 9 x16" guns - or am I wrong on all counts!

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Re: American SH shells - Famed or Folly

Post by Bill Jurens » Mon Nov 25, 2019 2:39 am

There is, so far as I know, no precise definition of the term "balanced" regarding design issues, and it seems to appear basically nowhere in formal naval architectural terminology. It appears to suggest a design where various tradeoffs result in a design which is in no way clearly outstanding or deficient -- in other words basically unremarkable with no feature in the 'iron triangle' of design -- i.e. speed, protection, and armament -- being seen to be excessive or markedly deficient. Of course the concept of the 'iron triangle' itself represents a convenient but somewhat simplistic metric in design, neglecting issues revolving around reliability, range, habitability, and versatility, to name just a few.

A good deal of ink has been spilled regarding the escalation from the Iowa class to the Montana class. Although the Montana class certainly represented a much larger and more powerful design, and General Arrangement plans were completed describing the design in detail, it's not clear whether they were really considered, in practical terms, more than a design exercise, especially after the war broke out. Considering the Iowas would have to be completed first, there is little chance that any would have been completed before the end of any practical war breaking out in the 1940s. The Iowas took about three years to complete so that group of ships in an of themselves would probably have not fully completed before 1945. Starting the Montanas after that would place them in commission probably somewhere around 1950. As most of us know, they were cancelled in 1943. By then, most of the design work was going into aircraft carriers of designs like the Midway class. Although the General Board conducted extensive discussions regarding the characteristics of the Montana class ships, this may be because the board was really not familiar enough with aircraft carrier operations, which were, of course evolving very rapidly during that time, to discuss many of the operational characteristics completely coherently. They understood guns well, but the mechanics of moving airplanes around rapidly and efficiently, etc. were probably a bit beyond them.

The Montana class was only similar to the Iowa class with respect to armament, both sharing basically the same 16" guns. The secondary armament, though still of 5" caliber, was of a fairly different design. The protective arrangements on the Montana class was very greatly enhanced, notably with regard to relatively thin splinter protection. This represents an area largely neglected in discussions where only protection against major-caliber bullets is usually considered important. The power plant, though basically similar mechanically, was geometrically rearranged so as to greatly enhance redundancy and overall resistance.

Bill Jurens.

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Re: American SH shells - Famed or Folly

Post by paul.mercer » Mon Nov 25, 2019 4:23 pm

Thanks for your reply Bill.
You are of course quite right in saying that the US were more interested in building aircraft carriers, but I can't help thinking that a 'Montana' would have been a spectacular sight had they been built!

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Re: American SH shells - Famed or Folly

Post by Ski206 » Sat Dec 07, 2019 5:52 pm

paul.mercer wrote:
Fri Nov 22, 2019 5:17 pm
Consider too the design of the South Dakota class ships. The NC had been originally designed around a 14” gun and when up-gunned to 16” was considered unbalanced. The South Dakota class was intended to be a balanced 35,000 ton treaty battleship with the 16”45 2240lb combination. But when BuOrd developed the 2700lb SH AP shell both it and the Iowa’s were essentially unbalanced as a result. The desire to have a properly balanced ship against the 16”50 2700lb was one of the major drivers behind the Montana class.

Gentlemen, please excuse my ignorance in this, but what is meant by being 'balanced', is it the size and weight of the gun and turret against the size of the ship or the shell balanced in flight, against the length of the rifling of the barrel or what?
Would I be correct in assuming that the longer 16x50 was better at stabilizing the heavier shell
I always thought that the 'Montana's were basically enlarged 'Iowa's with 12 instead of 9 x16" guns - or am I wrong on all counts!
Balanced in USN parlance refers to a useful immunity zone against the guns and shells carried by the ship in question. I don’t have my copy of Friedman handy but a google search for the South Dakota class turned up a designed immunity zone of 17.7k to 30.9k yards against the 2240 lb round. The 2700lb SH round reduced that to 20.5k to 26.4k yards. That narrow immunity zone meant that the USN viewed the design as unbalanced because the ship lack sufficient protection to stand up to her own guns and shells.

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