Pivot guns on gun decks

[johnpjones1775]

I’m going to guess the answer to this is structural integrity, but why didn’t they cut large long gun ports into what was nominally the gun deck for the large 9”, 100pdr parrot and dahlgren type guns, allowing for 4 of these big guns in a broadside?

Let’s take the USS Kearsarge as an example.
2 11” dahlgren guns on the main deck, and I believe that’s also where the other 5 smaller guns were as well.

So why not have large long gun ports in the first deck, between 8-12 ft long, and place similarly sized pivot guns there as well creating a broadside of 4 11” guns 4 32pdrs, and 1 30pdr.

 

[southwestforests]

I wonder if there might also be a factor of, where do you want your heaviest masses, inboard or outboard?

(off topic, my Dad was on another USS Kearsarge, the one numbered CV-33)

 

[WatcherZero]

The USS Powhatan had five 9" Dahlgren broadsides and an 11" on a forward deck swivel mount. I think there is several reasons why it wasn't more widespread though:
1. As you said cutting a large hole for a wide field of fire increases the vulnerability of the ship to incoming fire.
2. They were very large muzzle loaded guns so if you had them poking out the side of your ship you still had to recover them back to reload before running them out again, being centrally mounted on a swivel the crew could reload them quicker.
3. It was better for weight balance if the mass was in the centre of the ship.
4. They had much longer range than previous weapons so you often elevated them to a high angle.
5. The US principally had employed them in a shore bombardment role rather than ship to ship combat, even going so far as to mount them in small boats so they could be rowed closer to shore where a larger ship couldn't approach.
6. During this period the US was heavily using paddle wheel frigates which obstructed a gun decks broadside.
7. You are starting to reach the point where its more efficient to have one large gun covering both broadsides rather than having two which cant fire half the time.

 

[johnpjones1775]

The USS Powhatan had five 9" Dahlgren broadsides and an 11" on a forward deck swivel mount. I think there is several reasons why it wasn't more widespread though:
1. As you said cutting a large hole for a wide field of fire increases the vulnerability of the ship to incoming fire.
2. They were very large muzzle loaded guns so if you had them poking out the side of your ship you still had to recover them back to reload before running them out again, being centrally mounted on a swivel the crew could reload them quicker.
3. It was better for weight balance if the mass was in the centre of the ship.
4. They had much longer range than previous weapons so you often elevated them to a high angle.
5. The US principally had employed them in a shore bombardment role rather than ship to ship combat, even going so far as to mount them in small boats so they could be rowed closer to shore where a larger ship couldn't approach.
6. During this period the US was heavily using paddle wheel frigates which obstructed a gun decks broadside.
7. You are starting to reach the point where it’s more efficient to have one large gun covering both broadsides rather than having two which cant fire half the time.

I’m still advocating pivot gun mounts (swivel guns being small guns).
You wouldn’t have to run them out, hence why you’d need large long gun ports, but that might cause issues with smoke and ventilation.
Weight would still be centerline

Also they were mostly used for shore bombardment by the USN during the civil war because the confederates didn’t have enough ships for such guns to see widespread usage in that role.

 

[johnpjones1775]

I wonder if there might also be a factor of, where do you want your heaviest masses, inboard or outboard?

(off topic, my Dad was on another USS Kearsarge, the one numbered CV-33)

I’m not proposing any guns outboard.
Just mirror the main deck set up…one deck down.

 

[Scott Kenny]

I’m still advocating pivot gun mounts (swivel guns being small guns).
You wouldn’t have to run them out, hence why you’d need large long gun ports, but that might cause issues with smoke and ventilation.
Weight would still be centerline

Muzzle blast inside the decks?

No thank you!

 

[Dilandu]

I’m going to guess the answer to this is structural integrity, but why didn’t they cut large long gun ports into what was nominally the gun deck for the large 9”, 100pdr parrot and dahlgren type guns, allowing for 4 of these big guns in a broadside?

The elevation angle would be an issue. Those guns were designed for long-range fire (well, of course long range by cotemporary standards), and putting them on gun deck would severly limit their elevation.

 

[Dilandu]

You wouldn’t have to run them out, hence why you’d need large long gun ports, but that might cause issues with smoke and ventilation.
Weight would still be centerline

Erm... are you suggesting firing the 11-inch gun from INSIDE the ship's hull? Firstly, it would be insanely dangerous in terms of fire danger onboard wooden vessel. Secondly, the blast and smoke in enclosed space would likely disable gun crew for a while. Thirdly, the reload time would be abysmal. Gunners would be forced to wait till the atmosphere would clear enough before reloading - and due to muzzle flash and sparks, no ready ammunition could be stored near gun (one spark, and all gundeck would go "BOOM!

 

[DWG]

The core issue is a small port fits between frames, which are the structural strength of your ship, and an extended one cuts through multiple ones. Note that when they did move to pivot mountings on the later ironclads, the gun pivoted at the front, not the rear, allowing it to continue to use the small ports.

On top of that you need to seal the ports when conditions demand it. Even in WWI and post-WWI designs, casemate-mounted guns were generally so wet as to be useless, which was why they were abandoned in favour of turrets at main deck level or higher.

 

[southwestforests]

On top of that you need to seal the ports when conditions demand it. Even in WWI and post-WWI designs, casemate-mounted guns were generally so wet as to be useless, which was why they were abandoned in favour of turrets at main deck level or higher.

That strongly comes to mind in today's photo here,

Picture of the Week 44

Three of the five Queen Elizabeth-class battleships operate together in 1941. They are HMS Valiant (nearest to camera), HMS Queen Elizabeth, and HMS Barham. Each carried a main battery of eight 15”…

inchhighguy.wordpress.com

Three of the five Queen Elizabeth-class battleships operate together in 1941. They are HMS Valiant (nearest to camera), HMS Queen Elizabeth, and HMS Barham. Each carried a main battery of eight 15” guns.