Hypothetische Szenarien > Schiff A vs. Schiff B

Yamato vs Iowa von Bill Jurens

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Das gabs von ihm drüben bei warships1. Ist ganz interessant, auch wenn man mit der Simultaion vielleicht nicht ganz einverstanden sein mag.

I have read the threads now, but unfortunately have time to reply only briefly regarding an Iowa-Yamato 'one-on-one'.

Many years ago, c. 1985, I did a comprehensive study of these issues which involved integrating the total capacity of these various ships to inflict and receive damage over all range bands. The basic scheme was to have each ship fire a salvo at each opposing ship at increments of 1000 yards -- or sometimes at random intervals from zero to the maximum range of the guns -- and summing for each salvo the percentage of hits, and the percentage of penetrating hits. At the end of the exercise, the ship with the highest cumulative number of penetrating hits was considered the 'winner'.

Here are some sample results based on 100 salvos fired at randomly selected ranges from zero to c. 40000 yards. A penetrating hit penetrates the main armor, a non-penetrating hit strikes but is rejected by the armor, and an ineffective hit does not strike armor at all. These may not add up exactly due to rounding, as I have taken the values to the nearest half-hit. Armor Penetration was calculated using the method of ORD SK 78841 and assuming all armors of basically equal quality; other methods would be unlikely to yield significantly different results overall. Quibbiling aside, armor is -- pretty much -- armor...

Iowa firing Yamato target, Iowa optical fire control:

Cumulative hits 364
Penetrating hits 59
Cumulative non-penetrating hits 123
Cumulative ineffective hits 305

Iowa firing Yamato target, Iowa radar fire control:

Cumulative hits 425
Penetrating hits 54.5
Cumulative non-penetrating hits 158
Cumulative ineffective hits 370.5

Yamato firing, Iowa target, Yamato optical fire control:

Cumulative hits 301
Penetrating hits 70
Cumulative non-penetrating hits 80
Cumulative ineffective hits 231

Unfortunately, I did not do a computer run for Yamato using radar fire control, but we can estimate the effect by multiplying by the same ratios as for Iowa optical radar, results, which over all range bands looks to be about 1.16:1.
This yields:

Yamato firing, Iowa target, Yamato radar fire control:

Cumulative hits 349
Penetrating hits 81
Cumulative non-penetrating hits 93
Cumulative ineffective hits 268

What's interesting here is that in this particular sequence, Iowa actually obtains FEWER penetrating hits using radar than using optical. There is a bit of scatter in the data, due to the random selection of ranges, with every range being equally likely. In that regard, six successive runs under identical conditions yield:

Iowa firing Yamato target, Optical fire control:
100 samples, 7 runs.

No of penetrating hits: 59,49,43,46,44,57,50.

Regardless, the overall outcome would seem to be fairly clear, with Iowa achieving approximately 55-60 penetrating hits on average, and Yamato -- from her single sample -- achieving something between 70 and 80 penetrating hits depending upon her fire control arrangements. This would mean that overall, under randomly selected initial conditions, Yamato should be able to defeat Iowa most of the time. In general, the advantage always tends to go with the larger ship, which is, of course, why battleships tended to grow over the years.

The US estimates of the number of hits required to sink, derived from the Airborne Weapons survey assume a frank magazine penetration and a 100% probability of a magazine explosion thereafter. From directly above, the average magazine area is about 25% of the average overall ship area, which is where they got the 0.23 figure for a single-hit kill probability. For normal surface engagements, the magazine percentage seems to be about 17% of total projected area, and the chances of a magazine explosion being 100% are, in my opinion, somewhat overstated. My guess would be about a 50% chance of fuze action after penetration, and about a 50% chance of a catastrophic magazine explosion thereafter, which yields a catastrophic hit probability of 0.17 x .5 x .5 = 0.043, i.e. about 1 hit 23 or 24.

Hope this helps...

Bill Jurens.

P.S. Incidentally, Iowa vs Bismarck yields for 10 salvos each at 5000 yard increments, 0-40000 yards yields:

Iowa firing Bismark target, radar fire control:
113 cumulative penetrating hits

Iowa firing Bismarck target, optical fire control:
85 cumulative penetrating hits

Bismarck firing, Iowa target, optical fire control:
70 cumulative penetrating hits

Bismarck firing, Iowa target, radar fire control:
No run made.

Iowa is a fairly clear winner here, again, as might be expected.

Bill Jurens

*Mal den Staub vom Thema pust*

Dieses Bild soll eine Stirnpanzerplatte eines SA-Turms für Shinano, also Yamato-Klasse sein, die mit einem US-16"-Geschütz )wie auf der Iowa-Klasse verbaut) beschossen wurde:

 --/>/> http://www.flickr.com/photos/duddyd2003/3579844909/sizes/o/

Und hier der passende englische Text dazu:



Test of 26" (66cm) Class "A" Main Armament Turret Face (Port) Plate, originally for IJN SHINANO, the third Japanese YAMATO-Class super-battleship (converted into an aircraft carrier, instead, and sunk on its way to final fitting out yard by a U.S. submarine), which made up far left side of turret face looking from inside turret out of gun port, with "D"-shaped cutout making up about half of left curved gun port forming center of long right side of plate.


Japanese Vickers Hardened (VH) face-hardened, non-cemented armor (used only on YAMATO-Class battleships)






COUPON_ Y.S._ T.S.__ %EL._ %R.A

LONG.__ 68.5_ 99.4__ 22.3_ 45.6
TRAN.__ 70.1_ 98.2__ 25.5_ 62.2
NORM.__ N/A__ 93.16__ 7.0_ 20.3
(Average of 6 coupons)


COUPON# -105 -78 -50_ 0__ 50_ 100 <-TEMP.

LONG.#1_ 10G 23G 35G 73FG 75F 95F
LONG.#2_ 14G 20G 31G 77FG 94F 80F
TRAN.#1__ 8G 20G 30G 56FG 73F 70F
TRAN.#2__ 9G 20G 26G 48FG 71F 69F


LONG.=Longitudinal (parallel to plate face; long plate axis direction)
TRAN.=Transverse (parallel to plate face; short plate axis direction)
NORM.=Normal (in thickness direction)
Y.S.=Yield Strength (x1000 lb./sq.in.)(0.2% elongation point) (sq.in.=original cross-section)
T.S.=Tensile/Ultimate Strength (x1000 lb./sq.in.)
%EL.=PERCENT ELONGATION (% coupon had stretched when it broke)
%R.A=PERCENT REDUCTION IN AREA (% coupon cross-sectional area had shrank by at narrowest when it broke)

(Above data averaged from two coupons in each direction)

CHARPY V-NOTCH TEST=Hammer snaps off one end of coupon while other end is held in a vise with a notch-shaped groove put into coupon just above vise grip where coupon will fold and split apart (the higher the number, the greater the toughness)
"G"=All GRAIN (brittle fracture) at break point
"F"=All FIBER (ductile tearing) at break point
"FG"=Both GRAIN & FIBER MIXED at break point, more FIBER than GRAIN


(Ave. of two tests; measured from plate face surface directly into plate)

SURFACE:_46.5 (Tempered surface lost some carbon)
0.75":___50.0 (Maximum hardness of plate)
5.00":___36.0 ("Undrillable" face ends and transition layer begins)
9.25":___15.0 (Inner edge of back layer reached)

Hardness varied in smooth "ski-slope" curves between these points--at 0.75" hardness increase reversed direction abruptly. Back hardness varied from ROCKWELL "C" 11.0 to 15.5 in long undulations to back surface.



Steel had many tiny pieces of dirt and so forth, being about the same as pre-WWI British Vickers Cemented (VC) KC-type armor steel in quality (VC was used for the first time in the Japanese battleship IJN KONGO, built in Britain, and manufactured in Japan under license thereafter), from which the unique Japanese armors New Vickers Non-Cemented (NVNC), the homogeneous, ductile form of VH used in a number of Japanese post-WWI warships, and VH itself was derived (this steel was not up to U.S., British, or German post-1930 steel quality). Carbon content was raised above VC steel level to increase ease of hardening, some copper added to allow some nickel (in short supply in Japan)




U.S. Navy 2700-lb 16" Mark 8 Mod 6 AP with inert filler ("BL&P") (last version of this projectile manufactured during WWII)

OBLIQUITY: Near-normal (0°)

TEST #1 on 16 October 1946 (IMPACT #33443):

POINT OF IMPACT: Upper center near joint with turret roof at 0.33° obliquity from normal where plate was 25.99" thick.

STRIKING VELOCITY: 1992 feet/second (607.2 m/sec)

RESULT: Complete penetration and plate snapped in two through impact between side edge and upper end of curved gun port hollow. Hole more-or-less cylindrical, with little difference between front and back of plate. Numerous small cracks also put in plate around impact. No damage to projectile indicated, though projectile had considerable remaining velocity and ended up in the Potomac River, never being recovered. Considerable amount of lamination noted in hole (layering effect parallel to face, much like pages in a book glued together). The upper portion of this broken plate is now on display at the U.S. Navy Memorial Museum at the Washington Navy Yard, Washington, DC, just in front of the old Gun Factory building which houses much of the museum today.

TEST #2 on 23 October 1946 (IMPACT #33459):

POINT OF IMPACT: About halfway between first impact and base of plate, centered between cutout for gun port and left edge of plate, at 0.5° obliquity from normal where plate was 25.98" thick.

STRIKING VELOCITY: 1707 feet/second (502.3 m/sec)

RESULT: Projectile nose tip only penetrated 21" (53.34cm) into the plate, though punching a hole entirely through. Projectile was completely undamaged (merely lost its windscreen and AP cap, as usual). Plate had exactly the same thing happen to it as with the first test, with numerous small cracks, many laminations, and a complete break through hole between left edge and curved gun port cutout.


The U.S. Navy Ballistic Limit (complete penetration minimum velocity with this projectile at normal) estimated at 1839 feet/second (560.5 m/sec), plus or minus 3%, which gives it about a relative plate quality of 0.839 compared to U.S. Class "A" armor (estimated, as no such super-thick plate was ever made in the U.S.). This was about the same as the best WWI-era British KC-type armor, which was what the Japanese were trying for--they had not attempted to make improved face-hardened armor, as the U.S. Navy did during the 1930's, for actual ship installation.

The plate was excessively brittle internally, with too much "upper bainite" crystal structure due to too-slow cooling. This was due to using the same pre-WWI British Vickers KC-type armor-hardening techniques on plates over 17" (55.8cm) thick, for which they were never intended. This problem was solved during WWII, but no more VH was ever made except for some thin experimental plates. Brittleness did not seem to reduce resistance to penetration, though cracking might cause problems due to hits that ricocheted off.

Note that one of these experimental plates--7.21" (18.3cm) VH plate NPG #3133--was patterned on Krupp KC n/A (probably from data traded with Germany during WWII) and was tested by the U.S. Navy at the NPG using 335-pound 8" Mark 21 Mod 3 and Mod 5 (the latter with the super-hard AP cap, which turned out to be required to penetrate that plate intact) during this same test series. It was found to be THE BEST PLATE OF ITS THICKNESS RANGE (6-8" (15.2-20.3cm)) EVER TESTED BY THE U.S. NAVY, even though its steel was of the same rather poor quality as the other VH plates tested!!! This caused the U.S. test conductors to state that obviously they did not understand what it took to make a high-quality Class "A" plate, since the 7.21" VH plate should not have been so good from everything they thought they knew about face-hardened armor!!! Obviously the Japanese could make armor as good as anyone if the specifications had required it!



At about 40,000 yards, the U.S. Navy 16"/50 firing a 16" Mark 8 Mod 6 AP projectile (the later Mod 7 and Mod 8 designs were post-WWII, so I usually do not count them and they were no better ballistically, to my knowledge) will hit at about 45° downward angle and 1607 feet/second (489.8 m/sec). Just as with a point blank hit at 2500 feet/second (762 m/sec) and 45° obliquity, this hit too will barely hole the plate as the projectile is hitting at 0° (normal) obliquity, though not completely penetrate it. Any slight barrel wear will lower the muzzle and striking velocities and no holing will occur at THESE OR ANY OTHER ranges, as mentioned. However, this is so far above any real fighting range (even with radar it is hard to see the target due to the earth's curvature interfering, especially in any kind of imperfect seeing conditions) that I do not even consider it in my computations, while putting the gun barrel up to almost touching the enemy turret is also a pipe dream in real life! Thus, no holing or complete penetrations, ever, though possibly some cracking of the plate and possible jamming of the turret if the crack-off plate piece is dislodged badly enough.

Therefore, these plates are the only warship armor plates that could not be completely penetrated by ANY gun ever put on a warship when installed leaning back at 45°, as they were in the actual turrets!!! Even to completely hole the plate all the way through at that inclination requires a brand new 16"/50 Mark 7 or German 38cm SK C/34 gun at point-blank range firing the latest versions of their respective AP projectiles; it might be cracked at a lower striking velocity, but no hole put entirely through it.
--- Ende Zitat ---

Sieht aber nicht nach 650mm Turmfrontpanzerung aus. Bissl "dünn", daher auch das nette Loch.


Entscheidend sind Okuns Final Comments. ;)

Die Beschusstests waren nicht gerade realitätsnahe, da die Treffer bei fast 0° Obliquity (oder Einschlagswinkel = 90 Grad) stattfanden.

welcher einschlagwinkel wäre denn auf eine angemessene Gefechtsentfernung (10km vlt????) zu erwarten?


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