Design "feature" of R-class

[wmh829386]

Under D'Eyncourt, the R-class design has the main armour deck raised to the main deck level, which aligns to the top of the 13 inch belt. This, along with narrowing the beam reduced stability.
Further more rather than closing the top of the main belt with the flat deck, the deck slope downwards to the bottom to the belt, putting the armour slope at an unfavorable angle to incoming shell and splinters.

I have two questions.
1. Is there any evidence that reducing the GM improve gunney as claimed by D'Eyncourt?

2. The armour layout was kept from R-class to Hood, why does it take so long to move away from this design? (I guess after the Hood Mockup trial around 1919)

[marcelo_malara]

Hi. In my knowledge:

1-I do not know of evidence, but yes, reducing the GM smooths the response of the hull to a roll, making the righting moment more gentle and disturbing less the sights.

2-I understand that an angle of fall that would pass thru the thinner upper belt and into the slopes of the armoured deck was unthinkable at the time of design, basically because that angle of fall needs a corresponding high angle of fire, which was not then in use.

Regards

[wmh829386]

1. According to comments from DK Brown in "the Grand fleet"
"The effect of changes in metacentric height on roll behaviour is complicated and it is by no means clear that reduction in GM had much effect on the ships as gunnery platforms."

Worst still

"D’Eyncourt claimed that the reduction of metacentric height in the Royal Sovereign was achieved partly by reducing the beam by 18in and partly by raising the protective deck, giving a higher centre of gravity. This would have had a greater effect on flooded stability than on intact GM, something which was appreciated by d’Eyncourt and his head of battleship design (who was probably E L Atwood) and, for this reason, they decided to raise the protective deck ‘to a position well above the level of the deep load line, thus giving more protected freeboard in the damaged condition than in any of our earlier battleships’."

There are two problems. 1. In service, there doesn't seem to be anything to suggest that the R-class are better gunnery platforms than other ships. 2. Although R-class has a more extensive belt, it has thinner torpedo bulkheads than QE (1.5 inch vs 2 inch). This means R-class are much more vulnerable to torpedo hits.

To be perfectly blunt, it seems like there is no appreciable gains from reducing stability.

[wmh829386]

2. That is not true. DK Brown quoted the previous DNC Phillip Watts on this issue

"
In all of the Dreadnoughts up to the Royal Sovereign, the thick protective deck has been placed approximately at the position of the deep load line, because this was considered the best position for it. This deck is the final defence against shell reaching vital parts of the ship by penetrating the armour at, or near, the waterline or by dropping in over the top of the armour. The lower this deck is, the less likely to be struck by flat trajectory fire, and the more likely a dropping shell is to burst by passing through two or three decks before it reaches the protective deck, so that the deck will only be required to keep out the fragments. The new arrangement is not, I contend, nearly as good as that hitherto generally followed.
"
From Friedman's "The British Battleship 1906-1946"
"
Reviewing the design, Second Sea Lord (Admiral Jellicoe, formerly Controller) questioned the armour arrangement, particularly the thinner upper belt. D’Eyncourt argued that the high armoured deck, with its slopes, offered a kind of second line of defence behind the main belt. Future very heavy shells would often so damage the belt as to dislodge some of the plates, in which case the slope inboard of the main belt would limit the loss of intact water plane area and hence of stability. However, both the belt and the slopes might be penetrated, in which case he wanted a further protected lower deck under the armour deck.
"
It seems to show that even D'Eyncourt is partly aware of the problem.

[Steve Crandell]

And of course in the KGVs they went to a thick armored deck which met the top of the belt.

[marcelo_malara]

Hi all. In this section are these labels correct?

S-Lower or middle deck
T-Armoured deck
W-Upper deck
X-Forecastle deck
Z-Superstructure deck

[wmh829386]

One interesting point to note is that earlier RN 12 inch Dreadnoughts had heavier middle deck armor (both flat and slope) than the 13.5 inch super Dreadnaughts and the QE are the worst in terms of deck armor because of the 1 inch middle deck and the lack of any coal bunkers.

It is totally true that the R-class needs a different armour layout, but just definitely not the solution proposed by D'Eyncourt

[wmh829386]

Yes, that is the right graph. T is the main deck and S is the middle deck. There is no lower deck in this section.

The problem we are taking about is shell penetrating of the 6 inch plate (U) will end up on the 2 inch slope (R). Such penetration will be possible by WWI German 11/12 inch shells.

For example a hit on Tiger During run to the North in Jutland (Excerpt from Jutland: An Analysis of the Fighting by Campbell)

"This hit at 1555, pierced the 6in side armour a little below the upper deck, and 2ft forward of the after edge of `Q' barbette. The angle to the normal was estimated at 5-10°, and the shell made a hole of 12.5 in diameter in the side armour with a piece 6in wide broken away to the edge of the plate, passed through a 3/8 in bulkhead and burst against a second one, 22ft from impact and 8ft from the after 6in hoist."

[hans zurbriggen]

Hello Mr. wmh829386,
does Campbell mention Angle of Fall of this shell (or range at the time shell was fired) ?
AoF is key to establish probability for the shell, striking 'a little above the armored deck' (instead of 'little below the upper deck') , to penetrate slope (while de-capped, slowed and 'destabilized'): I assume slope was 2in non-armor-grade steel plate(s), do you know its inclination from horizontal ?

hans

[paul.mercer]

One interesting point to note is that earlier RN 12 inch Dreadnoughts had heavier middle deck armor (both flat and slope) than the 13.5 inch super Dreadnaughts and the QE are the worst in terms of deck armor because of the 1 inch middle deck and the lack of any coal bunkers.

It is totally true that the R-class needs a different armour layout, but just definitely not the solution proposed by D'Eyncourt

Gentlemen,
It's interesting to see that the QE class armed with 15" guns and presumably designed to fight an opponent with a similar armament had less deck armour than their predecessors and were very little faster, were RN designers a bit too complacent because Britain had the largest navy in the world?

[paul.mercer]

Double post!

[wmh829386]

Hi Hans,
The range of HMS Tiger at 3:55 pm is hard to say. At 3:50 pm Tigher is firing at 18500 yds. However there is no certainty on how accurate the range is. Since range was closing rapidly, a rough guess would be around 15000 yds at 3:55.

Regardless, the angle of fall should be around 5-10 degrees judging from the diagram on Campbell's book.

Hi Paul,
The problem of QE is not really because of complacency, rather it is a result of many compromises. There are a few things that compete with the middle deck protection for weight.

1. 2 inch torpedo bulkhead around the entire citadel
2. The 6 inch secondary battery with it's associated armour at the upper and forecastle deck.
3. Switch to oil fire that completely removed coal bunkers on middle deck.
4. Increasing the maximum thickness at the waterline and turrets.

The 6 inch battery is probably the worst when viewed in hindsight. As the 6 inch side and 1 inch roof is insufficient against battleship calibre shells. So despite the weight allocated, the 6 inch battery produce large casualties when being hit due to cordite fires. (See damages in Jutland)

To further illustrate the point, the 6 inch casemate armour is completely removed when QEs are rebuilt. And 1 inch middle deck are reinforced by 4 inch over magazine and 2.5 inch over machinery, all of the added deck are Non-cemented armour.

As for the speed, the QE are massively overweight, partly because of the lack of experience in using oil fire in such large ships. But still, their speed are just enough for them to be with the battlecruisers in Jutland. And oil fire means that they can sustain the top speed without worrying the stokers getting tired.

[marcelo_malara]

The problem we are taking about is shell penetrating of the 6 inch plate (U) will end up on the 2 inch slope (R). Such penetration will be possible by WWI German 11/12 inch shells.

This seems a remote possibility. The German 12" (http://www.navweaps.com/Weapons/WNGER_12-50_skc12.php) have a maximum elevation (as built) of 13.5%, that would make an angle of fall of about 15°, the shell would need to strike the very lower part of the upper belt to strike the upper part of the slope.

[wmh829386]

I am not so sure about the angle of fall for German 12" shell since I have never seen a range table for it. However, I have found the following in Campbell's book

There were four hits on the Barham, all from the Derfflinger, and probably by SAP shells, though the last may have been AP.

The hit at about 1658 was one of the most destructive in the battle. The shell struck the 1 1/4in upper deck, where this formed the glacis near No 2 starboard 6in gun, in line with the aftermost part of `B' barbette and about 7ft from the ship's side. The angle of descent was estimated at 30-35° which indicates that the shell was deflected downwards by c5-10°.

This implies an initial angle of fall closer to 20 degrees. Perhaps it is also due to the effect of roll of the ship.

Furthermore the central part of the R-class main deck is also only 1 inch thick. Now we consider the rest of the description of the hit.

The explosion blew a hole 7ft x 7ft in the main deck(3/8 in), and part of the shell head went through the 1 in middle deck and was found in the lower conning tower. The 3/8in lower deck, forming the roof of the forward 6in magazine directly below the lower CT, was holed and this magazine and the 6in shell room filled with smoke. Other fragments also pierced the middle deck, and the starboard forward hydraulic pump was put out of action by fracture of the pressure pipe to the hydraulic governor, though the remaining three pumps kept all four turrets going. The largest hole in the middle deck measured 18in x 15in and that in the lower deck over the 6in magazine 15in x 12in.

One more thing to consider is that the center part of the main deck of the R-class is also only 1 inch thick. So a WWI era shell passing the 6 inch plate between main and upper deck would meet one of the following ends.

1. Explode on/ penetrate the upper part of the 2 inch slope
2. Explode over the flat of the main deck that is 2 inch
3. Explode over the flat of the main deck that is 1 inch

[hans zurbriggen]

Hello everyone,
looking at ship section, I would not say the probability of an hit against slope is remote: any shell striking at the lower end of upper belt may hit sloped deck except at point blank: scenario n.1 from Mr. wmh829386 is most dangerous as 2in (construction steel) slope, very inclined from horizontal, is not enough to stop intact shell.
I see this design as very weak: either 1) main belt must end quite higher then flat deck to protect its sloped part or 2) thick flat deck must be added over slope to protect it (e.g. modification to Hood over magazines).

hans