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Dec 17 16 7:33 PM
Maciej wrote:In calculation I used 3.5" thickness. With WWII Japan deck armour quality. So "flat part" was penetrable at ~20 000 yards, ~18 000 meters, sloped closer.
It is not 100% accurate for sure, but what to do better? 2.8"? OK, but what parameters put into program?
If 2.8" with WWI euality, say WWII era japan qulity, flat part will be penetrable at what? 18 000 yards?
And finally we have declaration of program designer that results are not so accurate, as program is based only one one 3" uncapped shell performance.
Dec 17 16 8:21 PM
I measured the "slope" of the outer 16' of BB-49 and it is much less than 5 degrees
Dec 17 16 8:59 PM
Maciej wrote:I measured the "slope" of the outer 16' of BB-49 and it is much less than 5 degrees
I used Corel Draw. Original plan was as a "background"
Than exactly horizontal line I rotate exact 5 degree - all data can be used manually. That moved 5 degree match exact original dravings, like 3 degree from vertical match exact external belt.
OK use exact 3" WWII US steel. So "flat part" is penetrable at ~20 000 yards, so ~18 000 meters.
Sloped - as You can see. That 5 degree makes big difference in calculation
Dec 18 16 4:32 AM
Dec 18 16 8:16 AM
At 1:48 scale, they are very detailed indeed.
If one is discussing the Colorado class, one should indeed be using drawings of the Colorado class, and not extrapolating from a hypothetical design, i.e. the South Dakota class, which was not actually built.
It's also worth noting that the armor suites aboard these ships changed somewhat over time, especially after post-Pearl Harbor reconstruction, so details taken at time 'x' may not be very relevant at time 'y' some years later.
The 2nd Deck, at the top of the armor belt, is flat midships, cambered 10 1/8" in 22 feet outboard. This is equivalent to a radius of about 287'-1"
As the decks are curved, the idea that there is some discrete angle of slope involved, is basically wrong, as the slope changes with distance outboard from the tangent point. The decks are not flat with a 'knuckle'.
When considering deck penetration from high-obliquity impacts, it's important to note that the plate is not merely 'floating in space' but is supported by a rather substantial grid of heavy structural members underneath,. in this case 10" deep 20# I beams. The degree of penetration would be very dependent upon where the projectile struck the plate, either on top of one girder or between two adjacent girders, and whether or not the projectile, should penetration occur, would intercept any additional structure underneath. It's no use quibbling about a few millimeters of armor thickness, or issues of elongation etc. -- though these are interesting in and of themselves -- when the effects of supporting structure underneath the deck would probably have an order-of-magnitude greater effect depending upon exactly where the projectile hit.
Dec 18 16 9:58 AM
Dec 18 16 10:05 AM
What is being lost in all this chatter is my original question of how the deck of Colorado could possibly be pierced at only 12,500 meters by Nelsons shell.
Dec 18 16 1:59 PM
Dec 18 16 4:45 PM
Dec 18 16 7:17 PM
Dec 18 16 7:47 PM
Dec 18 16 8:10 PM
Dec 18 16 9:13 PM
Neil Stirling wrote:Thanks Maciej! Your post has moved me to post after a nearly total absence of about 15 years. How about KGV and Washington vs the German 15" and Japanese 16"? Looking forward to HMS Lion.
Dec 19 16 12:16 AM
Dec 19 16 1:06 AM
Neil Robertson wrote:The US Navy itself added 0.7 x (thickness of thinner plates) to the thickness of the thickest plate. Admittedly that was usually for horizontal protection.I prefer the IZ approach in evaluating ship protection in comparison to looking at one typical range alone which most threads have revolved round over the years,Neil Robertson
Dec 19 16 7:21 AM
program is based on one uncapped undamaged US Army 76mm (3") M79 AP
Monobloc Shot projectile with a typical average middle-nose-height
1.67-caliber Tangent Ogive nose, about the simplest middle-of-the-road
nose compared to all projectile nose shapes used by all navies. EVERY
penetration formula is based on a single projectile design and then uses
some sort of quality factor to adjust it for other plate and/or
projectile designs. My program is almost exactly in the center of all
homogeneous, ductile naval armors of WWII as to plate parameters, though
at the high end of plate quality, and the projectile is too. My
HCWCALC program allow modifications for AP Caps (only two types,
though), Hoods, and Windscreens. It does not have adjustments for
projectile nose shape, a major defect, to be sure, but neither do any
other penetration formulae ever made, other than bending the projectile
quality factor to try to handle this in tabular form. I have some data
on nose shape effects and hope to include it in some fashion in the
future, but that is a major thing with homogeneous, ductile armor and I
do not wish to do this attempt before I have a good idea of what is
important and what is not and how important the word "important" is for
each nose shape effect (some noses, especially when AP caps are acting
as the projectile noses, have complex shapes that drag in all sorts of
positive and negative factors and trying to sort out what is what is
difficult). If you have some good test results to match with the given
quality factors in the programs, you will have some reasonable idea of
what that projectile will do against different plates at different
obliquities, as long as the nose shape does not deviate too much from
the one given -- WWI noses were usually longer with sharper points and
WWII noses were usually shorter, sometimes even oval, but both shapes
can be roughly estimated with HCWCALC.
these programs and some good test data to adjust the quality factors,
you can get a reasonable idea of what to expect, in general, with
pointed or oval nose shapes and even with tapered-flat-nose shapes,
which covers the majority of uncapped projectile noses and, with
HCWCALC, even some of the capped noses.
general rule is that the blunter noses have significantly better
penetration in the region between about 50 and 65-70 degrees obliquity
(normal = 0 here, not 90) than longer, more pointed noses, though this
is reversed at under 30 degrees, where a long point will dig in deeper
and allow easier penetration. Above, 70 degrees, details of the nose
shape for oval/pointed noses starts to lose any effect since the plates
are so thin to have the ability to penetrate at all, that the projectile
forms a long, deep dent (wide dish to the sides with a central
canoe-shaped gouge under the projectile body) and only when the nose
finally can dig deep enough to open up a torn slot at the bottom of the
gouge will the armor bend outward and downward enough to let the nose
dig into the end of this slot, bend it up as a upward-curving triangular
spur, and then push up the plate to be above the nose to, in effect,
ricochet downward through the armor off of the back of the plate,
usually still going at a high speed even when barely penetrating (the
projectile merely changes ricocheting upward and away to ricocheting
downward and through (at a somewhat lower remaining velocity for the
latter, to be sure). Against extremely thin plates, the base can punch
through the widened slot at a lower velocity than the nose can, so when
the nose is deflected upward to ricochet, the projectile "surfs"
sideways with its nose tilted upward for some distance through the
plate, rapidly slowing down, until it either flips upward and away from
the plate or backward and through the plate -- in neither case will the
projectile be moving very fast nor have any kind of stable, predictable
direction of motion after leaving the plate, and its base fuze, if any,
will not be functioning since there was not enough force parallel to the
projectile centerline to throw the firing pin into the primer. HCWCALC
predicts a base-through NBL for the thin plates at high obliquity, but
it is more of a rough estimate, not a hard-and-fast value like the
nose-first, somewhat-higher-velocity NBL for those same plates.
This is more than is available anywhere else...
Dec 19 16 8:25 AM
Dec 19 16 5:25 PM
Dec 19 16 6:21 PM
Maciej wrote:Thank all of you for explanations.
1. I need to recalculate deck penetrations. It was some time ago, when I carefully checked all Nathan’s Okun texts, so I used outdated program to calculate deck penetration.
It will be redone.
I’m a bit reluctant to mix modern program with old calculations of combined thickness of “sandwich” or “space arrays”. It will add to uncertainly of results.
In deck I possibly add 1-2 color lines, to show difference in different calculations. Usually deck is more or less flat, so it will be not so time consuming, but I’m not sure about that. Depends what graphs with too many lines will look like.
In case of Colorado’s deck.
Using information from Delcyros we will see 2.5” WWII era STS….
With 4.3 slope in largest portion, I even don’t want to start calculations
Some time ago Thoddy put US own calculation of deck penetrations. Colorado was included.
I was sure that I copied it on my HDD, but I can’t find it. On this forum too. Help please!
Dec 19 16 11:18 PM
Actually according to Nathan...If we assume that the NS has only the resistance it had in 1890, QA = 0.76, so 1.75” NS = 1.33” STS, and the thickness is lowered to T(lam) = 2.81”. Not 2.5"
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