How close did the USS North Carolina come to sinking

[Tiornu]

That's a good point. The 3rd deck, just 30-lb outboard of the inner belt, was completely mangled. The potential path of flash from that space to other inboard spaces is not readily aparent from the material I have, but it is cerrtainly conceivable.
While none of the powder was scorched at all, the four crewmen who died at the point of the blast had their hair singed off.

[Werner]

That's a good point. The 3rd deck, just 30-lb outboard of the inner belt, was completely mangled. The potential path of flash from that space to other inboard spaces is not readily aparent from the material I have, but it is cerrtainly conceivable.
While none of the powder was scorched at all, the four crewmen who died at the point of the blast had their hair singed off.

30 pound steel is 1 1/4 inches, is it not? As I recall, the innermost bulkhead was mild steel, the others ductile steel.

For comparison, a Gato's pressure hull was 11/16 inch of mild steel.

The singed hair sounds like it may have been a consequence of electrostatic effects of the explosion. That sounds even more dangerous than flash.

[Tiornu]

A 30-lb plate is .75in. In this portion of the hull, the innermost torpedo bulkhead was the thickened inner belt of 2-3.75in STS. Bulkheads 1-4 are not labeled, so I take it to mean they are mild steel.

[Werner]

A 30-lb plate is .75in. In this portion of the hull, the innermost torpedo bulkhead was the thickened inner belt of 2-3.75in STS. Bulkheads 1-4 are not labeled, so I take it to mean they are mild steel.

You're right. I was thinking of the weight of 1/2 inch steel. My bad.

[Guest]

That's a good point. The 3rd deck, just 30-lb outboard of the inner belt, was completely mangled. The potential path of flash from that space to other inboard spaces is not readily aparent from the material I have, but it is cerrtainly conceivable.
While none of the powder was scorched at all, the four crewmen who died at the point of the blast had their hair singed off.

30 pound steel is 1 1/4 inches, is it not? As I recall, the innermost bulkhead was mild steel, the others ductile steel.

For comparison, a Gato's pressure hull was 11/16 inch of mild steel.

The singed hair sounds like it may have been a consequence of electrostatic effects of the explosion. That sounds even more dangerous than flash.

That's backwards. The innermost bulkhead in the TDS is the one intended to absorb any remaining explosive force by elastic membrane deformation, and then return to its original shape after the explosive force is spent. To allow this bulkhead to deform as necessary, it is usually unsupported in the middle by any frame and rely on its own strength for structural integrity. So this bulkhead is usually fairly thick, strong, and built of elastic high tensile steel.

The intermediate bulkheads inside the TDS were sacrificial, and intended to progressive absorb the force of the explosion by rupturing one after another. So those bulkheads are usually ductile mild steel. Furthermore, in the process of rupturing, these bulkheads must not generate fragments and splinters so massive such that when propelled by the remaining explosion they could be driven through the inner most bulkheads. So these intermediate bulkheads are usually fairly lightly built.

[Werner]

30 pound steel is 1 1/4 inches, is it not? As I recall, the innermost bulkhead was mild steel, the others ductile steel.

For comparison, a Gato's pressure hull was 11/16 inch of mild steel.

The singed hair sounds like it may have been a consequence of electrostatic effects of the explosion. That sounds even more dangerous than flash.

That's backwards. The innermost bulkhead in the TDS is the one intended to absorb any remaining explosive force by elastic membrane deformation, and then return to its original shape after the explosive force is spent. To allow this bulkhead to deform as necessary, it is usually unsupported in the middle by any frame and rely on its own strength for structural integrity. So this bulkhead is usually fairly thick, strong, and built of elastic high tensile steel.

The intermediate bulkheads inside the TDS were sacrificial, and intended to progressive absorb the force of the explosion by rupturing one after another. So those bulkheads are usually ductile mild steel. Furthermore, in the process of rupturing, these bulkheads must not generate fragments and splinters so massive such that when propelled by the remaining explosion they could be driven through the inner most bulkheads. So these intermediate bulkheads are usually fairly lightly built.

That's what I thought, too. I didn't say anything because I didn't have the reference handy (and I already goofed on the weight of mild steel). The innermost bulkhead is meant to be deformed many feet without rupture in North Carolina. In the later classes, they extended the armor down to the inner bottom with negative consequences for torpedo protection. North Carolina was probably the safest modern US battleship in the area of torpedo defense.

[Guest]

That's what I thought, too. I didn't say anything because I didn't have the reference handy (and I already goofed on the weight of mild steel). The innermost bulkhead is meant to be deformed many feet without rupture in North Carolina. In the later classes, they extended the armor down to the inner bottom with negative consequences for torpedo protection. North Carolina was probably the safest modern US battleship in the area of torpedo defense.

The relative advantage of extending side armor down to the bottom is a debated issue. Experience of Bismark and POW clearly shows the potential for long range steeply diving shells to penetrate below normal belt is no joke. It is in principle plausible, and by no means yet disprove as an actuality, that the penetrating hit which destroyed the Hood was an underwater hit that pierced the TDS.

[Ron Smith]

Turret One was out of commision until she returned to Pearl Harbor as Ulithi did not have the proper facilities to repair her.

Just a minor point, but Ulithi was not yet in US hands. Forward base repairs were being done at Esprito Santo, and no drydock facilities were available there.

Done specifically at Tongatabu assisted by Vestal.

[Ron Smith]

The handling room flooding was a rate of 50 gallons per hour leakage caused by a deflected rollerpath support and loosened rivets. Flooding second deck and above was due to ruptured or loosened seams where the compartments immediately below were flooded. A number of compartments were deliberately counter flooded to remove the list, she was list free and resumed steaming within six minutes of the hit. Total weight gained from all flooding 970 tons, at no time was flooding severe enough to endanger the ship. At Tongatabu Vestal cut away some blown out plating along the hull, assisted in shoring the damaged structures, sealing leaks and retrimming the ship 7 feet down at the stern. During the trip to Pearl the few leaks that existed were dealt with using temporary pumps run for 15 minutes each watch.

All smoke was believed to be from the initial explosion, no fires resulted. Probably the initial flash of the explosion scorched a few things that contributed to the smoke. Compartments A-310-L and A-317-T are the only compartments to report a confirmed flash. Reported but unconfirmed flash powder handling room and access trunk. A magazine fire was reported but no evidence of fire was ever found in the magazine. As a precaution only the sprinklers were activated in the powder handling rooms and magazines of turret 1, they were turned off quickly as no fires were evident.

Turret 1 had a distorted roller path with burrs that prevented training, the burrs were removed and the turret could be trained. Its use was restricted to "situations of extreme gravity" until it could be adequately tested. Part of the structural concerns were bulkheads crushed against the turret stool and the possibility it was forced off axis or had hidden damage.

Most severe in terms of combat capability was the increased vibration to the forward fire control instruments and the shock damage to the main radar antenna.

No cause was ever determined for the 4 dead men with singed hair.

[Ron Smith]

I wonder if the "smoke" was not indeed dust and paint flakes dislodged by the compression waves that would have proceeded across the width of the ship and for some odd distances fore and aft....

Could be, it was reported a grey or yellowish grey. Some could also be pulverized ceramic as a head and shower were pretty much crushed. One man was showering and died there.

[Tshipley]

Ron, by chance have you read "Boys of the Battleship North Carolina" by Cindy Ramsey? It is a great read about the crew stories tying them to the ship's log.

[Ron Smith]

Ron, by chance have you read "Boys of the Battleship North Carolina" by Cindy Ramsey? It is a great read about the crew stories tying them to the ship's log.

Nope, I've read her decklog and damage reports and have full copies of the latter.