design of turrets

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paul.mercer
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design of turrets

Post by paul.mercer » Fri Feb 05, 2021 10:26 am

Gentlemen,
Looking at some of the turrets on later battleships they appear to be almost flat on top, if, as has been discussed elseware, a shell arrives at an angle and does not fall vertically, surely a turret roof with a bit of a 'dome' on it would increase the chances of it glancing off. Obviously the designers knew what they were doing, but I wonder why they went for almost flat tops?

HMSVF
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Re: design of turrets

Post by HMSVF » Fri Feb 05, 2021 1:40 pm

paul.mercer wrote:
Fri Feb 05, 2021 10:26 am
Gentlemen,
Looking at some of the turrets on later battleships they appear to be almost flat on top, if, as has been discussed elseware, a shell arrives at an angle and does not fall vertically, surely a turret roof with a bit of a 'dome' on it would increase the chances of it glancing off. Obviously the designers knew what they were doing, but I wonder why they went for almost flat tops?

This is just a guess. If the roof is flat then the shell has more armour to bite through as its coming down at an angle.If you "dome" it your effectively reducing that amount. Vice versa tanks developed sloped hulls to effectively increase the armour thickness by angling the plate. Same plate as before (say 70mm) but more protection as the shell has more to penetrate if it doesn't ricochet off. Difference being between naval guns and tanks being that tank guns fire far more on a flat trajectory. Probably wasn't an issue when fighting was thought to be around 10000 yards max but was when the range opened up to 20000+


Sorry probably haven't explained my reasoning too well!

Steve Crandell
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Re: design of turrets

Post by Steve Crandell » Sat Feb 06, 2021 1:18 am

Yes, I think a dome would be counterproductive because the shell would likely hit on it's side, making it more likely to penetrate. In addition, a dome would be more difficult to fashion with face hardened steel and weigh more for a given thickness.

edit: I just realized that most navies didn't make turret roofs out of face hardened steel because it was more likely to shatter if hit a glancing blow by a heavy shell. That in fact happened to a french ship when it was hit during the British harbour attack early in WWII.

Mostlyharmless
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Re: design of turrets

Post by Mostlyharmless » Mon Feb 08, 2021 10:55 pm

The optimal shape for a main gun turret for a WW2 battleship was not obvious. The simplest solution was a box with a vertical face and a flat top as chosen by the British. The USN designs were similar but the face was sloped back, slightly reducing the weight of the roof at the price of making a penetration of the face slightly more likely. The USN designs used significantly thicker armour than the RN designs.

The French designs looked almost the same shape as the RN and USN except that the roof was slightly sloped so that the turret was higher at the back and thus a shell was more likely to defeat the roof armour at long range. However, the most significant difference was the use of face hardened armour for the turret roofs. This was more likely to defeat bombs at the price of creating a danger that fragments might be thrown into the turret by a shell hit that might be safely deflected by the same thickness of homogeneous armour.

The German designers used a more complex faceted shape. This has been criticised but has its logic as discussed in an old thread http://www.kbismarck.org/forum/viewtopi ... =45#p53736. The point is that even the 16" thick faces of North Carolina's turrets could be penetrated by Bismarck's guns out to 28,000 yds according to http://www.navweaps.com/index_nathan/Pe ... 2%2F47_gun. Thus reducing the size of the target was an attractive alternative. The 180 mm facet had the additional advantage that it might deflect a shell rather than try to stop it and thus cause less shock to the mechanism. German roofs were much thinner at 130 mm than the British at 149 mm or the USN at 7.25" (184 mm).

The Italians also chose a "pitched" roof but with 200 mm thick armour on the roof. This gave the Littorio Class far the best resistance of turret roofs to bombs apart from the Yamato Class and both Littorio and Roma survived bomb hits on turret roofs with little damage.

If you really want to defeat shells hitting the face and also bombs, one might follow the Yamato Class with its massive 650 mm face angled back at 45 degrees and a 270 mm roof (4 plates with the highest rear one flat and the other three angled back and slightly overlapped). Unfortunately those turrets weighted more than a destroyer.

HMSVF
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Re: design of turrets

Post by HMSVF » Tue Feb 09, 2021 4:22 pm

Steve Crandell wrote:
Sat Feb 06, 2021 1:18 am
Yes, I think a dome would be counterproductive because the shell would likely hit on it's side, making it more likely to penetrate. In addition, a dome would be more difficult to fashion with face hardened steel and weigh more for a given thickness.

edit: I just realized that most navies didn't make turret roofs out of face hardened steel because it was more likely to shatter if hit a glancing blow by a heavy shell. That in fact happened to a french ship when it was hit during the British harbour attack early in WWII.

Dunkerque at Mers El Kebir wasn't it?

Steve Crandell
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Re: design of turrets

Post by Steve Crandell » Tue Feb 09, 2021 7:24 pm

Yes, I believe so. Sad history of a beautiful ship.

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