Dave Saxton wrote:Could You give data from live tests?
I have boxes and boxes of documents. Unfortunately, because of my present circumstances they are in storage and they are not handy. Nonetheless, if I recall correctly the British study that found that no British battleship gun could defeat more than about 5-inches effective deck protection at less than 32k was documented in the ADM281 set of documents. This was a post war (WW2) live ammunition study.
Test against plates taken from Tirpitz. Armorur homogeneous, 65 degree oblique – penetration at 1100 f/s.
It corresponds to ~25 000 yards.
Tests against 8” armour at 45 degree – again full penetrations in condition to bust. Now I'm agay from my sources, but will check it later today or tomorow. It was not such bad.
Several years ago, I graphed various battleship gun’s deck penetration attainments on the Y axis vs range on the x axis. Seeing this in graphic form instead of on a chart was very interesting, particularly when put into the context of IZ. About 5 ½ -inches effective was the point of diminishing returns in terms of how much IZ it bought. 130-140mm was good to around for 30,000- 32,000 yards with just about every gun 14” and larger-including super heavies. Adding a couple of more inches only bought a marginal increase in IZ.
That correlates quite well with my pgraphs. With differences in details.
Something between 5 and 6” was „good enough”. Anythig thicker pushes protection in such area when shells falls so stepp, that increase in thickness must be very large to gain anything important.
If You add 2 thickness of deck on Bismarck add 2 thickness (or more if existed) on other ships.
Vanguard had weather deck ~30 mm thick, so sum was ~180 (magazines) and ~155 (machinery)
It is difference.
The problem is that the 30mm in not armour grade steel.
Armour/not armour is not so simple.
American STS used for deck protection sometimes, but was „construction steel” were tested with Tirpitz plates. Were slight better than German
Britiss Ducol steel were slight inferior. Say was 90% that of Tirpitz. So instead of 32 You have 29 mm.
Dismiss? British throw it away, and take into calculation only armour alone. But that plate was there.
I would agree wthat with very low obliques any impact of that plate on incoming shell is marginal. Byt with high oblique impacts ( as standard for deck penetration ) I'm not so sure.
It is not likely to induce much yaw because it is incapable of consuming much energy (and the distance between the weather deck and MAD is too small for much yaw to become manifest anyway),
Any yaw taking into caclulation is dangerous anyway.
and it is unlikely to de-cap incoming large caliber ordnance. In that case the Krupp rule for calculating effective thickness comes into play using the square root of plate 1^ + plate 2^+ plate 3^… method. This means its addition to the effective thickness is not significant. The British understood this, because they made sure that KGV’s deck protection was 5-inches over the machinery and 6-inches over the magazines, counting the homogenous armour plates only. This was deemed adequate against 16-inch fire out to ~30k in their IZ calculations.
Depends which 16” guns,
But I don't fully inderstand all British metodology
For example. They had tests of actual 14” shells fired from KGV. It clearly shows that at ~30 000 yards for new gun that could penetrate (more – perforate so in condition to burst) ~12” of british face hardened armour.
And still apply to any data that such a gun could penetrate 12” of vertical armour at ~16 000 yards or so (from memory have to check) with „0” inclination.
Splinter decks, as well as structural decks, in my opinion, are very inefficient allocations of armour weight. Why not just include that weight into the primary plate (or decapping plate if applicable) where it can do some good? Or exclude that weight from the design if it only provides a marginal or insignificant improvement of protection?
Depends on total distribution of compartments below.
Bisrmack just under the main deck had magaiznes. Any fragmets from plate could start troubles. Splinter protection could be very effective if there is room.
But if shell fully perforated deck, any splinter protection is waste of weight. See Jean Bart hit on Cassablanca.
[/quote]Bismarck seem to be exact that design only with more modern materials and 30 knots. Everything else is virtually the same
I disagree that it the same thing even if it looks similar on a cross sectional drawing. It is fundamentally different in concept. The earlier designs were based on arresting splinters after ordnance was fused by the outer layer. Hoyer’s lecture and other documents make it clear that the two armoured decks, and the scarps of the more modern design were part of the effective thickness calculations in the context of modern IZ requirements.
There is nothign in being agree/disagree there is description of design and logic behind.
Description of that 1919 design is simple
Modern AP shells become so powerful that it is virtually impossible to put single plate to protect ship from such shells at short range.
Deck had to be so thick that it is impossible to put it on top of belt to give adequate protection against such shells. So something different is needed.
So belt of moderate thickenss (12+ inch), heavy slope behind and main armour deck more or less on waterline level.
Higher plate to activate fuses, start yaw of shell and forece detoations above main armour deck.
Only this could quarantee protection of vitals from point blank range to long range.
More – ship had to have 3 shafts, 8x15” C50 guns (4x2). Lenght in British therms, so in German metodology it will be C52 guns, 16x 6” guns in twin turrets preferable, but 12x6” acceptable. AA outfit to be decided later.
Distributon of artillery, internal arragement, armour scheme – it is simply description of Bismarck. With exact the same logic behind. With only difference – 25 knots max speed, and smaller fuel tanks. Bitish had larger bases netwoerk, so don't need very long range.