A SAI Jutland AAR and turret armor philosophy in RTW and RL

[rimbecano]

I did a playthrough of Jutland in SAI tonight, and the results demonstrate the weakness of a design philosophy that appears to have been pervasive for a while in real life, and that I have also seen people report using in RTW, namely,  the use of an armor profile where turret face armor is thinner than the belt. 

A brief AAR of the alt-Jutland action is as follows: once my (Britain's) scouting CLs contacted the German BC force, I sent 5th BS on an ESE course to get behind Hipper, while sending the BC line itself on a NE course to engage him and draw his attention. My BCs actually engaged him fairly late, his CLs were in earlier, more solid, and more constant contact with 1st BCS  than they were with 5th BS, so even before the BC lines were in visual contact, I was able to use the movement of 1st BCS to steer him and lure him north. I soon had him cornered between the BCs and 5th BS, and maneuvered to hold him there until the Grand Fleet could arrive on scene. The cohesion of the German line broke up as they tried to find a way out and started facing torpedo attacks from two directions from the supporting elements of the BC and 5th BS forces, and as the Grand Fleet arrived Seydlitz was significantly further south than the rest of Hipper's force, but his destroyers and an attempt by his line to break out to the south had positioned 5th BS fairly far away from her, while my BC force was much closer to the other German BCs. I was nervous about my BCs engaging the German force at close range for too long, so I arranged for the leading elements of the Grand Fleet to press in just as close. The result was that the German BCs were engaged by most of the RN battle line at ranges that got, at times, to within 5000 yd. Von Der Tann was immobilized by having power knocked out, and within another few minutes took a penetrating hit to A turret and blew up.

I was worried about my own ships,  especially the BCs, taking a golden BB at that range, and also worried about torpedoes, so I began opening the range, but other than Seydlitz, the German BCs were no longer in fighting condition: Lutzow lost mobility and took over a hundred heavy hits and 10(!) torpedoes as the whole Grand Fleet passed by her at the same ranges that its leading elements had, and Derflinger and Moltke were engaged less closely, but each ate 60+ heavy shells and a torpedo. Seydlitz was not engaged by the Grand Fleet or the BCs, which had closer targets, and remained under the combined fire of the whole 5th BS for a good chunk of the engagement. However, German destroyers remained an obstacle to the 5th BS engaging her closely, and she took only 24 hits and remained in fighting condition.

I was just beginning to consider engaging Seydlitz with the whole fleet when outlying CLs reported contacts traveling in line astern to the southeast. Within a few minutes, it was confirmed that this was the leading division of the High Seas Fleet. I did not want to risk British BCs against full German battleships, so I sent the BCs home, while having the 5th BS move to take the vanguard of the Grand Fleet. The two battle lines met with about two hours of daylight left, and the only occurrence of note in the ensuing textbook parallel slugging match was that HMS Orion took a German 11" shell to a turret and blew up. At nightfall, I opted to disengage, and that was the end of it.

This brings me to the issue of armor profile: 5 capital ships were lost, 4 German and 1 British. Of these, two were lost to turret fires. Von Der Tann probably was doomed anyways, as she was taking fire at very close range, but she only took 12 hits in the entire battle, half of what Seydlitz took, and right on the cusp between the ships that were reported as having "light" vs. "medium" damage in the battle report. Orion only took 7 hits, solidly in "light" damage territory, and, unlike VDT, would not have been in danger if immobilized, as she was engaged at long range and was part of a cohesive line of battle, which would have served to shelter her. Both ships' belts were thicker than their turret faces by about an inch, and it seems that shaving an inch off the belt would have allowed for significantly more armor on the turrets, which in Orion's case would likely have saved the ship, and in VDT's case would have allowed her to do more damage to the enemy, or at least would have made sinking her take more resources.

Does anyone know why this was done historically, or can anybody that uses such armor schemes in RTW say why they do so? 

[bcoopactual]

I can't tell you for certain.  I can guess that the designers of the ships historically did not anticipate that the crews would stow extra powder charges around in the turrets so they considered the chance of a fire getting from the gun house to the magazines to be less likely.  If you consider a catastrophic flash fire to be unlikely or already accounted for by safety features in the turrets then I could see them looking at a shell penetrating a turret meaning at worst (probably) the loss of two guns where a shell that penetrates the belt has the possible consequence of a direct hit to the magazines or the engine room.  So you protect the belt more.  With hindsight I would think the armored deck should provide some backup in most cases and the designers probably could have put some of the belt weight on the gun houses instead but again, that's with the benefit of knowing the results of the historical Jutland and SMS Seydlitz's experience at Dogger Bank previous to that as well.    

I personally don't follow that philosophy.  My turrets are always the most heavily armored space on the ship with the possible exception of the conning tower if I have a little weight leftover to add a half inch or so to the CT.  Now days, I'm more likely to use that extra weight for ammunition though.  

Also, I thought that was a very interesting strategy for a Jutland battle, using the BCS and the 5th BS in a hammer and anvil attack is not something I would have wanted to experience if I was a member of the German 1st Scouting Group.  

[dorn]

Turret armor is big question. Top Turret is quite quite cheap, so there is no difficulty to have 1 or 2 inches more.
However armor is quite heavy.

Firstly we can look what happened in history. RN battlecruisers were lost because their armor was not adequate against capital ships and RN procedures and cordite.

But we can look further, RN increased their safety precautions that penetrating hit to turret would have no negative effect on magazines. There was price for that as KGV turrets need time to remedy all the issues with more complicated system. However even lower forward turrets armor did not jeopardize ship.
Now se can look ať Bismarck, her turrets were knocked out quite quickly. But she got so many hits that question is if more turret armor could help.

No we can look ať Scharnhorst, the damage to machinery was fatal.

So in history there is no easy question as technology envolve that penetration hit to turret was not fatal for any capital ship. And that fire control which was much more easily disabled was important too. Having all turrets without proper fire control was almost same as not having turrets.

Now se can look on RTW. Ships blow up quite offen, disabling turrets by hits is a lot of time just luck.

I agree that for the first half of game turret armor is vítal but as time go on I think that turret armor is not as important as it was.

[garrisonchisholm]

One thing that was painfully apparent to me in my PLC AAR is that twice I was forced to reduce speed for the whole battle-line to keep a belt-holed ship in line, once that nearly lead to me destruction, the other time it allowed the foe to escape a catastrophic blow. Consequently I have not skimped on belt at all in my designs, unless the game has put me in a desperate situation. Having one valuable ship slowed to 10 knots can ruin a very fine day.

[rimbecano]

Jan 7, 2019 13:15:28 GMT -6 garrisonchisholm said:

One thing that was painfully apparent to me in my PLC AAR is that twice I was forced to reduce speed for the whole battle-line to keep a belt-holed ship in line, once that nearly lead to me destruction, the other time it allowed the foe to escape a catastrophic blow. Consequently I have not skimped on belt at all in my designs, unless the game has put me in a desperate situation. Having one valuable ship slowed to 10 knots can ruin a very fine day.

I myself don't tend to slow down the line for cripples. If there is no doubt as to their buoyancy and no threat of them being overwhelmed by the enemy, I tend to let them follow at best speed. If there is doubt as to their buoyancy, I detach them and send them home. If there is risk of them being isolated by a superior force, I send them home and use my main force to screen their withdrawal. 

If I have the enemy on the run, my main force is generally between the enemy and my cripples anyways, and generally won't suddenly become a superior force because one of my ships falls behind, so I generally have anything that isn't in danger of sinking follow at best speed. 

[aeson]

Jan 7, 2019 13:00:14 GMT -6 dorn said:

Turret armor is big question. Top Turret is quite quite cheap, so there is no difficulty to have 1 or 2 inches more.
However armor is quite heavy.

If we're being technically correct, then by area the turret top is the largest exposed part of the turret by a significant margin - especially with three or four guns in the turret - while the turret face is one of the smallest parts. Turret face armor should therefore have a significantly lower weight cost per inch of thickness than the turret top armor. Even if you include side and rear armor with the turret face you're probably still looking at something no worse than comparable in weight cost per inch of thickness to the turret roof.

Does anyone know why this was done historically,

My suspicion is that it was presumed that turrets would be relatively unlikely to be hit, because they typically have a low profile and so present a "small" target relative to the rest of the ship for low-trajectory shells, and that it was believed that even if the turret was hit and penetrated it was relatively unlikely that it could threaten the ship, because "modern" powders and explosives were safer than older powders and explosives, and of course everyone knows that gunpowder and high explosives are dangerous so who's going to cut a few corners on safe shell/powder handling procedures or disable safety measures installed in the magazines and hoists?

There's also that turret face armor was often inclined even on relatively early ships whereas belt armor - especially on earlier warships - was more nearly vertical, so, at least against low-trajectory shells, the apparent thickness of the turret face armor might be greater than the apparent thickness of the belt armor for low-trajectory shells even if the actual thickness of the turret face armor was less than that of the belt armor, and on top of that the higher angle of obliquity for low-trajectory shells impacting on the sloped turret face rather than on the vertical belt meant that shells were more likely to glance off or break up. An 8" armor plate inclined 45 degrees from horizontal looks like it's more than 11" thick to something moving in the horizontal plane, and on top of that a 45-degree impact angle is pretty bad for penetration, so for short-range engagements where shells will have relatively flat trajectories that'd probably be a pretty decently armored turret.