Comparisons of Axis vs Allied Combat Vessels

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Thorsten Wahl
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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Thorsten Wahl » Wed Dec 17, 2014 3:23 pm

on the following chart you can determine the approximative effect of thicker walls on armor piercing projectiles (both projectiles had the same weight.)
this chart compares the early 7,5 cm Pzgr rot with the improved model 7,5 cm Pzgr 39 with smaller cavity for projectile condition pentration whole fit to burst.
At impact velocities up to about 500 m/s both performances were approximativly equal, but at higher velocites the older model begins to deform and shatter, even increasing velocity does not increase penetrative capability.

additionally you may determine a effect of relatively reduced ballistic capability of armor plate by reduced ultimate tensile strength of the armor plate with increased thickness
Modellwechsel.jpg
Modellwechsel.jpg (37.74 KiB) Viewed 5701 times
on the following chart you may determin a effect of changing ultimate tensile strenght on ballistic capability of a plate with given thickness, but be careful with conclusions, the presentation is greatly simplified for the single case tested (as penetration is a multidimensional problem changing other possible variables may change the graph unforeseen even different thicknesse may change the course)
Festigkeit.jpg
Festigkeit.jpg (23.71 KiB) Viewed 5700 times
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Dave Saxton
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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Dave Saxton » Wed Dec 17, 2014 3:55 pm

Steve Crandell wrote:The thing is, the Yamato belt armor was inclined, so that would tend to reduce the penetration. Also, in post war US testing against an Iowa size faceplate the British 14" shell tended to deform and ricochet off of thick armor because of the thin walls they accepted in order to get the large (for the caliber) explosive filler.
This brings up another thing about modern shells. In tests, the L/4.4 naval shell still penetrated heavy face hardened armour intact at striking angles as great as 60* from the normal. (see Adm213/951). The penetration was slightly lower but it penetrated intact nonetheless.
the British 14" shell tended to deform and ricochet off of thick armor because of the thin walls



British tests post war of 14" and 15" service shells pulled at random from service inventory, found that they did in fact tend deform or even break up when striking heavy armour with some obliqity. However, select 14" and 15" shells from the Royal Ordnance Factory did not, and all the short body 16" shells tested for the Nelson and Rodney did not. Further testing indicated it was not the wall thickness as much as the length of the main body. Slightly shorter shells remained intact better than longer shells. This length factor was also a finding by Krupp.
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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Thorsten Wahl » Fri Dec 19, 2014 9:04 pm

mis post
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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Neil Robertson » Wed Jan 21, 2015 8:12 pm

Dave Saxton wrote:
Garyt wrote:Well, if we knew before the wat that we will fight mostly the Kongo class in battleship engagments, the 14" guns make sense. But we had no idea if it would be the Kingo class, the Nagato class, or even the Yamato.

I'd hate to go up against the Yamato with 14" guns!
14" guns could be effective against the Yamato. Inside of 21,000 yards they could defeat the Yamato's belt protection just as much as the Kirishima's belt. Also at ranges exceeding 25km the American 1500lb 14" shell was a good deck penetrator due to a steep angle of fall * and due to having a good head shape for oblique striking angles. The British 14" gun was a better belt penetrator short of extreme range than the Washington's 16" gun. These comments were made by Mr Okun in this forum a few years ago:

Also, shell weight does not matter very much as to penetration of face-hardened armor (it is only to the 0.2 power), though full weight effects occur against homogeneous armor. The homogeneous armor gives way slowly and the entire projectile momentum has time to get involved in punching a hole. Thus, projectile weight and the square of the velocity can be seen to balance the complete kinetic energy required to penetrate (a heavy projectile has a lower striking velocity to penetrate in accordance with the conservation of energy of the entire plate and projectile).

Face-hardened armor, however, is rigid and does not give until the force gets too great to resist, at which point the hard face caves in suddenly and the pressure can then tear through the soft, ductile rear of the armor. Usually, the face breaks prior to the full weight of the projectile getting involved ...This is why the use of 2700-lb 16" shells (US final Mark 8 AP design) does not buy you much compared to 2100-lb 16" shells (WWI Mark 3 AP design) -- a 29% weight increase -- against the same face-hardened armor plate, assuming equal damage to both projectiles from the impact. You only can reduce the impact velocity with the heavy shell here to 94% of what you need for the light shell; hardly worth the effort to make the heavy shell here.

Actually the 14" gun KGV was better suited to the historical Guadalcanal battle (Kirishima or Yamato) than the 16" gun Washington and South Dakota because the 14" gun is good enough and the belt armour of KGV is miles better. Better yet would be a scarp triangle protection scheme.

*The lighter weight results in a greater loss of velocity with range and therefore a steeper angle of fall at very long range compared to a heavier shell.
I find this interesting because I have never thought before how penetration varies with weight. While I often find Mr Okun to be a bit biased his reasoning in this quote seems logical. The low exponent of 0.2 given evidently explains why the British 14 in gun had the edge over the US 16/45 firing the slow superheavy shell.

Looking at the Gercke armor penetration formula the exponent of velocity is 1.25 and, on the face of it, the exponent of the shell weight is 0.5. The latter involves an interpretation of the Gercke formula that is probably not permissible. Namely, this formula applies to a specific family of shells where the shell weight was closely determined by the calibre. So varying the shell weight for a given calibre is not valid but nevertheless doing so is instructive as it gives some comparison, and backing, for Mr Okun's weight exponent of 0.2.

I did look at the Navweaps penetration data by Mr Lundgren and Mr Worth to discover, somewhat to my surprise, that the British 14 in gun did have the edge in vertical KC penetration over the US 16/45 with the slow superheavy shell up to a little over 20000 yds. The German 15/48.4 was superior again and slightly better than the British 15/42 with supercharges.

The above holds true at face value. Although not stated by Mr Lundgren and Mr Worth I take it that the ballistic data they use is as given elsewhere on the Navweaps site. Namely, the US data are for a new gun and a charge temperature of 90 F, the British data are for average used gun and 80 F charge temperature, and the German data are for new gun and a charge temperature of 15 C (59 F). If all the data were normalised to the same gun condition and charge temperature then the results would be changed a little. As it is the data presented on Navweaps are favourable to the US gun, unfavourable to the British gun, with the German figures some way between the two.

Pertinent to the subject of this thread, this comparison is for the US Mark 5 shell, which was contemporary with those on German ships and to the Guadalcanal battle. Supporters of the US ships are apt to use the data for the later (1945 onwards) US Mark 8 shell which not unsurprisingly shows the US weapon in a more favourable light.

The upshot of all this seems to be that the slow superheavy shell 'bought' its decidedly superior deck penetration at the expense of mediocre vertical penetration for the calibre. It was certainly superior in broadside to its European contemporaries but not in terms of vertical penetration or burster weight.

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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Garyt » Sat Jan 24, 2015 12:25 am

Supporters of the US ships are apt to use the data for the later (1945 onwards) US Mark 8 shell which not unsurprisingly shows the US weapon in a more favourable light.
You are absolutely right. Whenever it comes to comparing ships, it seems those biased towards US vessels use the 1945 "super heavy" stats. And while it may penetrate well, it trafes the enhanced penetration for a smaller burster.
While I often find Mr Okun to be a bit biased his reasoning in this quote seems logical.
While I love his work, I fond him to be a bit biased as well, favorably biased for the US. Also what I find interesting is he has somewhat recanted on two areas, one the Japanese armor which he originally gave a factor of .90 and later changed it to .95. The decapping effect of the Iowa's and a few other US battleships seems to have been revised a bit as well, seems as though now the Iowa's decapping layer seems to have been too thin to decap full sized battleship shells (not too mention it was never designed as a decapping layer to begin with).

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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Neil Robertson » Sat Jan 24, 2015 12:46 am

I have found in the meantime an error in my post above. The exponent of shell weight in the Gercke formula is 0.625 (exactly half the exponent of velocity (1.25)) and not 0.5 as I stated earlier. Basically, the Gercke formula is rearranged to have thickness of armor penetrated on one side of the equation and shell weight and velocity on the other. On doing this the exponent of thickness is 0.8 and the exponent of shell weight is 0.5. Hence when the thickness exponent is increased to 1 the exponent of shell weight becomes 0.5/0.8 = 0.625.

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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Byron Angel » Sat Jan 24, 2015 3:33 pm

I know Nathan. There is not a biased brain cell in the man's cranium.

For example -
Best medium thickness WW2 armor ever tested? Nathan's opinion is Japanese.
Best heavy WW1 armor? Nathan is very fond of the Austrian Witkowitz product.

What may be perceived by some as a "pro-US bias" is IMO quite likely a function of his data on foreign weapons, projectiles and armor not being as complete as his US data.

B

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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Steve Crandell » Sat Jan 24, 2015 7:02 pm

What I don't understand is when this topic was stated to include "combat vessels", but then the point is made that USN "battleships" didn't take a lot of damage so there was no indication of their ability to do so. What about all the cruisers and other ships that were heavily damaged and through good damage control survived to fight another day? Aren't those "Combat Vessels"?

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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Paul L » Sun Jan 25, 2015 4:47 am

Garyt wrote:Mostlyharmless - Excellent points in expounding upon the topic.

I think that much of the real issue I'm speaking about here may be sample base.

For instance, the North Carolina and Yamato each get struck by one torpedo. The Yamato takes on about 3000 tons of water, the North Carolina 1000 tons. JUst from this it would seem the torpedo protection on the North Carolina is better. But it is merely one torpedo. Depending upon where the hit was, the damage can by highly variable, as could the amount of flooding. As the Yamato and her sister the Musahi took 12-20 torpedoes prior to sinking (notice I did not say "in order to sink them") in addition to a lot of bomb damage it is hard to fault the overall effects of these vessels torpedo protection systems. I think part of the issue stems from the Yamato's lower belt extending deeper than on most battleships. I might add though that the Iowa and South Dakota classes had a deeper belt as well, and the rigidity of a deeper belt is often thought to be a negative factor on the Yamato class for torpedo protection. It is thought that a less rigid armor scheme protects better against the concussive force of a torpedo hit. So why is the Yamato class maligned for it's extension of it's lower belt, while the other american BB's are not? My guess is that with enough torpedo hits, you would see some breakdown caused by problems with the lower armor belt of the America Battleships. As we have on record only a single torpedo hit on an american battleship, we can never see this theory tested.

But the real point is we cannot look at the effects of one torpedo striking each vessel and determine the effectiveness of the torpedo defense systems. For if we extrapolate the amount of water taken in vs. ship displacement of these two vessels, one could argue that it would take 20-33 torpedoes to sink the North Carolina, and I do not feel that is at all accurate.

The Prince of Wales could possible been sunk by the first torpedo that hit her. If this would have indeed happened, should we surmise that this class of battleship could be sunk by one torpedo? Or should we assume there was a lucky hit?

I'd think the KG5 class was not the best protected vs. torpedoes, not because of the hit sustained but largely because the narrowness of the voids, 13 feet vs 17.5' for the American classes, or 23.5' for the Yamato or Vittorio Veneto.


If a vessel takes 12 torpedoes to sink it, that's what it takes.

If another of the same model takes 20 torpedoes to sink it, THAT ship took 20 torpedo hits to sink it. Can't change these facts.

What it probably means is their is a huge variation in shot to shot effects that can generate a range of results.
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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Neil Robertson » Mon Jan 26, 2015 8:03 pm

Byron Angel wrote:I know Nathan. There is not a biased brain cell in the man's cranium.

For example -
Best medium thickness WW2 armor ever tested? Nathan's opinion is Japanese.
Best heavy WW1 armor? Nathan is very fond of the Austrian Witkowitz product.

What may be perceived by some as a "pro-US bias" is IMO quite likely a function of his data on foreign weapons, projectiles and armor not being as complete as his US data.

B
The point you make is very true. At the moment I am reading Friedman's Fighting the Great War at Sea. I am up to p 293 and it may be the hardest book to read because of the great density and complexity of material that I've ever read. The book is a great achievement, despite numerous typos. However, there is a lot more about British ships and technology than German. The author has clearly spent a lot of time in the British archives. That is not to say there is nothing new about German ships, on the contrary there is (and that includes in the German texts such as Griessmer that he cites). However, his knowledge of German sources is obviously less than that of the British, and quite a bit about the German side has been taken from British sources. So what we have, as well as the purely factual and technical stuff, is one side evaluated on the basis of its own sources and the other side evaluated on the basis of a relatively limited amount of its sources and a good bit of their opponent's sources. This is not a good starting point for a truely impartial assessment.

Friedman says at several points in the book that postwar German authors such as those of Krieg zur See were at pains not to be critical of the German side. So far he has not said that of the British side. But does he really think the British were not interested in accentuating the positive of their side too?

Despite this Friedman is still in my opinion one of the more impartial authors on this subject.

And what of myself? Well the material I have, primary and secondary, is mainly of British and German origins. Stepping back, I see that I am generally more favourable about the ships of these nations than others. So, yes, what you say usually holds true,

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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Thorsten Wahl » Mon Jan 26, 2015 9:03 pm

im not sure on the unbiased approach there were some with regard to Krupp "hit on the head"
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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Garyt » Tue Jan 27, 2015 12:17 am

What about all the cruisers and other ships that were heavily damaged and through good damage control survived to fight another day? Aren't those "Combat Vessels"?
That is indeed relevant Steve, and any direct comparisons you have regarding vessels other than BB's would be intertesting.

For instance we can compare non armored deck carriers. What I have seen is survivability is most directly correlated to the status of the carrier at the time it was struck, basically were flight operations such as arming and fueling going on when struck. Many will point to Midway as to a lack of survivability of Japanese carriers. Most imortant issue was that they were caught during flight operations. For American carriers, we don't really see this until the Kamikaze attacks, in which case we have new modern fleet carriers hit by 1 kamikaze, maybe 2, and burn out so bad they are almost too badly burnt to repair. And this is with late war damage control on new vessels built after 1940, 2 areas which both help in damage control, and they were still almost a total loss.

In light of this, in my opinion if a carrier is struck while flight operations are going on it's pretty well toast. Good damage control can prevent a total loss, but it's not going to be conducting any flight operations until repaired, and heavy damage is the best possibility for this type of carrier.

Without flight operations going on, a carrier can sustain hits and live on, such as the Shokaku class, the Yorktown, etc. I actually put the Shokaku class pretty high on survivabilty as extensive damage was taken by this class at both Coral Sea and Santa Cruz. Perhaps it was a function of their rather thick armor over machinery and ammo.

The ability to stop flight operations though was largely a result of effective air search radar. The Japanese did not have it at Midway of course. For the US carriers struck by kamaikazes it was a different story. When you ar elooking at a few planes at a time, sometimes trailing behind friendly formations, radar detection becomes much more difficult. And even if the US could detect these at a distance, I'm not sure they would be willing to shut down all carrier flight operations everytime they noticed a bogey coming in.

I'd also say that closed hangar carriers like the US Lexington class and all Japanese carriers were vulnerable to fumes caused by fractured AVGAS tanks and AVGAS vapors. The better ventilation of open hangared carriers made AVGAS fume buildup less of an issue.

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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Garyt » Tue Jan 27, 2015 12:29 am

If a vessel takes 12 torpedoes to sink it, that's what it takes.

If another of the same model takes 20 torpedoes to sink it, THAT ship took 20 torpedo hits to sink it. Can't change these facts.
I think you must be comparing the Yamato and Musahi. At this point, I'm more inclined to believe the US technical mission's recount of things, which would put the Musahi in the realm of 12-14 torpedoes, depending on how you account for probables and possibles.
I know Nathan. There is not a biased brain cell in the man's cranium.

For example -
Best medium thickness WW2 armor ever tested? Nathan's opinion is Japanese.
Best heavy WW1 armor? Nathan is very fond of the Austrian Witkowitz product.

What may be perceived by some as a "pro-US bias" is IMO quite likely a function of his data on foreign weapons, projectiles and armor not being as complete as his US data.
Perhaps not. It just looks interesting that his decapping formula changes, initially the New Jersey had a decapping layer effective against most battleship shells, a later revision shows it effective against not much more than cruisers shells, which should be stopped by it's belt armor at most ranges anyway. And the Yamato's armor isinitially graded about a .90 compared to US "A" class armor of 1.0, and it's later revised to be more effective.

There are other studies that perceive US class "A" armor to be flawed, I don't believe Nathan has addressed this. I have more specifics on this, just not at my fingertips this instant.
Best medium thickness WW2 armor ever tested? Nathan's opinion is Japanese.
I have not seen this stated by him - can you reference the source for this, and the specific armor type being rated this highly?

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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Steve Crandell » Tue Jan 27, 2015 1:31 am

Garyt wrote:Perhaps not. It just looks interesting that his decapping formula changes, initially the New Jersey had a decapping layer effective against most battleship shells, a later revision shows it effective against not much more than cruisers shells, which should be stopped by it's belt armor at most ranges anyway. And the Yamato's armor isinitially graded about a .90 compared to US "A" class armor of 1.0, and it's later revised to be more effective.
Try this (Decapping Revisited): http://www.navweaps.com/index_tech/tech-085.htm

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Re: Comparisons of Axis vs Allied Combat Vessels

Post by Byron Angel » Tue Jan 27, 2015 3:44 am

GAryT - Re Japanese armor, it came up in private correspondence some years ago. I may have some related material/documentation filed away on this, but I would need to track it down. IIRC, it was part of a US postwar evaluation of Japanese versus US armor.

B

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