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Thread: Iowa horizontal protection (over magazines)

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    Iowa horizontal protection (over magazines)

    I have a few questions regarding the horizontal protection of the Iowas, especially over magazines. Based on Friedman's diagram and Nathan Okun's description, the horizontal protection over the magazine is as follows.

    Weather deck: 1.5" (38 mm) STS
    Armored deck: 4.75-5.75" (121-147 mm) Class B on 1.25" (32 mm) STS
    Third deck: 1" (25 mm) STS.

    So the question is this. Does the 0.625" splinter deck mounted slightly below the armored deck not extend to the area above the magazines? Additionally, what is the thickness of the third deck in areas other than over the magazines? Finally, is the third 1" STS deck over the magazines laminated to a metal backing or just there by itself? I've heard conflicting reports regarding this.

    Thanks.
    Last edited by Radical; 28 Jul 16, at 11:41.

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    Defense Professional RustyBattleship's Avatar
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    Quote Originally Posted by Radical View Post
    I have a few questions regarding the horizontal protection of the Iowas, especially over magazines. Based on Friedman's diagram and Nathan Okun's description, the horizontal protection over the magazine is as follows.

    Weather deck: 1.5" (38 mm) STS
    Armored deck: 4.75-5.75" (121-147) Class B on 1.25" (32 mm) STS
    Third deck: 1" (25 mm) STS.

    So the question is this. Does the 0.625" splinter deck mounted slightly below the armored deck not extend to the area above the magazines? Additionally, what is the thickness of the third deck in areas other than over the magazines? Finally, is the third 1" STS deck over the magazines laminated to a metal backing or just there by itself? I've heard conflicting reports regarding this.

    Thanks.
    Those are very interesting and intelligent questions. I will try to answer them to the best of my 80 year old memory.

    Your first three listings of the upper three decks is correct. As for the splinter deck (30 inches below the 2nd deck) is 25.5 lb (5/8" thick) of STS on the Iowa and New Jersey. It was increased to 30.6 lb (3/4" thick) on Missouri and Wisconsin.

    Well thanks to Pearl Harbor attack and both Germany and Japan ignoring London Treaty restrictions on standard weights of Battleships, it was open season for how big or heavy we were going to build Battleships from then on (such as the Montana class).

    Even the 20mm and 40mm AA machine gun shields were increased from 25.5 lb to 30.6 lb. We needed to increase our lightest armor to at least stop the 7.7mm Arisaka or 8mm Mauser rounds. Hopefully any larger caliber could possibly glance off if not hitting straight on.

    The transverse armored bulkhead on frame 50 of Class A armor was increased a couple of more inches on BBs 63 & 64.

    Now, the aft armored bulkhead at frame 166 was not the end of the "Armored Box" (as we called it). Where the 2nd deck armor ended but aft of that bulkhead, 3rd deck armor continued to frame 203 to protect the aft steering gear rooms, which also had Class A armor bulkheads port & starboard to protect the sides.

    Sorry, I'm a little tired to dig out my armor diagram plans at this time, but just remember: The Iowas were the most heavily armored ships built by ANY nation. Oh yeah, some countries said they had thicker armor. But nowhere did they come close to our Class A armor. Nor did they consider adding the armor several feet INBOARD to use the outer bulkheads and shell plating to act as sacraficial trigger plates or at least slow the weapons down.

    As for overhead armor of the magazines, you seem to be referring to the 16"/50 magazines. But all 5"/38 magazines were ON the 3rd deck and only the 6" thick laminated STS/Class B armor was above them. Adding a splinter deck would have taken up too much room and when you have a squadron of suicide planes coming at you -- you need as many rounds as you can get because you have to load those guns with VT/FRAG as fast as possible.

    LEAD, DAMN IT! LEAD!

    But during their 1980's modernization, I was tasked to design where to add an extra 400 tons of HY-80 armor plate ABOVE the Main Deck to support the Tomahawk Cruise Missile machinery and electronic rooms below the ABLs and the 20mm Magazines under each CIWS "Gatling Gun". That was mostly 30.6 lb armor. Oh yes, also added 40.8 lb armor all around the new communications radio room on main deck about amidships. Then there was the 61.2 lb HY-80 armor all around our new Combat Engagement Center on 02 level.

    Oh, almost forgot, also had to add 10.2 lb armor ON TOP of existing 30.6 lb STS armor in a few critical spaces.

    Now you may be wondering why I'm describing the thickness of armor in pounds rather than gauged inches. That's the way we have to order it on all of our engineering drawings. That's also the way we have to order it from the steel mills. The poundage shown is what one square foot of steel (of the thickness required) weighs. Comes in very handy for our Scientific Design Section to calculate how much heavier the ship weighs (in long tonnes), where the new center of gravity will be and where the new center of buoyancy will be and how much more draft the ship will have when fully loaded.

    Okay, that's my history lesson for today. Still tired out from my birthday yesterday. The crew on the Iowa presented me with a small party and birthday cake and at my favorite VFW post I got more tokens for fee drinks that I could use. (Did use the last one earlier this afternoon).

    Thank you for asking some technically critical questions. I'll look up my armor diagrams tor the steering gear room armor tomorrow. I hope.
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    Thank you very much for the response.

    Yes, I was referring to the 16" main battery powder magazines. As far as I know, between the powder storage and the 6-7" armored deck, there is another 1" STS splinter deck. Perhaps I didn't pick it up in your post, but is the 25.5 lb (5/8") STS under the main armored deck only above machinery spaces, or is it also above the 16" powder magazines? Also, are the powder magazines themselves subdivided, i.e. magazines are divided into separate armored compartments? Do you know why the inboard part of the deck armor is 4.75" Class B + 1.25" STS (total of 6") while the outboard deck armor is 5.75" Class B + 1.25" STS (total of 7")? As far as I know the thicker deck armor area does not apply over the 16" powder magazines. Is there a reason why?

    Also, the transverse armor at Frame 50 is 11.3" Class A on Iowa/New Jersey, and 14.5" on Missouri/Wisconsin. Is this armor mounting similar to that of the side belt Class A, with 2" cement between the armor and backing plate, or does the Frame 50 armor not have cement?

    Again, thank you very much for your knowledge.
    Last edited by Radical; 28 Jul 16, at 11:41.

  4. #4
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    Quote Originally Posted by Radical View Post
    Thank you very much for the response.

    Yes, I was referring to the 16" main battery powder magazines. As far as I know, between the powder storage and the 6-7" armored deck, there is another 1" STS splinter deck. Perhaps I didn't pick it up in your post, but is the 25.5 lb (5/8") STS under the main armored deck only above machinery spaces, or is it also above the 16" powder magazines? Also, are the powder magazines themselves subdivided, i.e. magazines are divided into separate armored compartments? Do you know why the inboard part of the deck armor is 4.75" Class B + 1.25" STS (total of 6") while the outboard deck armor is 5.75" Class B + 1.25" STS (total of 7")? As far as I know the thicker deck armor area does not apply over the 16" powder magazines. Is there a reason why?

    Also, the transverse armor at Frame 50 is 11.3" Class A on Iowa/New Jersey, and 14.5" on Missouri/Wisconsin. Is this armor mounting similar to that of the side belt Class A, with 2" cement between the armor and backing plate, or does the Frame 50 armor not have cement?

    Again, thank you very much for your knowledge.
    You are almost right on the first part. There IS a 1" thick STS "splinter" protection over the 16" magazines but it is actually the 3rd deck itself, not an overhead catchall. This 1" deck runs from Bhd 50 aft to Bhd 87 then picks up again from Bhd 152 to Bhd 166. Those areas cover the powder can stowages down below for the Main Batteries.

    And yes, the powder magazines are sectionalized. Very sectionalized. I have redrawn their arrangements with Corel Draw 5 which worked extremely well with Windows XP but with this %$#*@ Windows 7 I can only show them for a few seconds in hopes of typing "print" before Bill Gates stops my Corel from working.

    To continue: The subdivisions of the powder mags are separated "only" by 3/8" thick M.S. Bulkheads. BUT, the passing scuttles from the magazines to the turret's ammo hoists go through TWO circular STS bulkheads. The scuttles are designed in such a way that to open the outboard scuttle the inboard scuttle MUST be CLOSED and vice versa. Also, there are NO gunners mates BETWEEN those circular bulkheads. Sorry, I don't know if the thickness is still classified or not.

    Yes, the BHD 50 Class A armor is attached to 5/8" thick STS. Also, the 3rd Dk FWD of frame 50 to the bow ranges from 1/2" to 7/8" STS, but going aft from Fr 50 to Fr 97 it is 1" STS.

    AFT STEERING: 3rd Dk Fr 166 to 184 is 5.8" Class B on top of 3/4" STS. From Fr 184 to 203 it's 6.2" Class A on top of 5/8" STS.
    The side armor is 13 1/2" thick Class A armor. Bhd 203 is 11 1/4" thick C;ass A on top of 5/8" thick STS. ALSO, outer longitudinal bulkheads from Fr 189 to Fr 204 are 5/8th" to 7/8" thick STS (that was used to protect the small boats gasoline tanks. Now it protects a JP-5 tank on the starboard side).

    Well, gotta go. Keep those questions coming.
    Last edited by RustyBattleship; 28 Jul 16, at 22:43.
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  5. #5

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    This is a section view of the Iowa from Friedman, I believe.



    For the powder magazines, is there another bulkhead beyond the innermost 5/8" (16 mm) holding bulkhead of the torpedo defense system? Was each powder bag stored in individual containers?

    Furthermore, is anyone here familiar with the layout of the HMS Vanguard battleship? The layout of the ship is below.



    My readings seem to show that the magazines are the lowest deck on the ship, just above the keel, and is only in one deck. It seems like the Vanguard's magazines are particularly difficult to reach and hit.
    Last edited by Radical; 29 Jul 16, at 19:11.

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    Radical asked: For the powder magazines, is there another bulkhead beyond the innermost 5/8" (16 mm) holding bulkhead of the torpedo defense system? Was each powder bag stored in individual containers?

    As I mentioned earlier (I think) there are two circular bulkheads around the base of the turret foundation. They are VERY effective against a flash over. Regrettably this was proven during the Turret II "incident" on the USS Iowa, but in reverse. Though 47 men lost their lives, it was every man from the turret on down to the lowest level where the powder bag hoists are. Because of the double sealed scuttle design, all gunners mates in the powder rooms themselves were never injured. The only thing they knew that something went wrong is that the sound of the rapid deflageration of the propellent bags sounded much different than one of the guns firing. It wasn't until one of the powder handlers opened the door and saw the lower deck of the turret on fire they knew a disaster had happened.

    The armor arrangement and fire-zone bulkheads on the USS North Carolina was another proof of well designed "pocket traps" when she was hit by a Japanese Long Lance torpedo. One of my fellow Configuration Managers (Don Wolcott) at LBNSY was a "Devil Dog" (US Marine serving aboard a ship) was at his gunnery station in the starboard 40mm gun tub on the fantail at the time. He told me that after the fish hit, witnesses up forward said they could see some flashing of crushed powder cannisters starting to ignite but the water came in so fast the fire was put out almost immediatly.

    And, by the way, the torpedo hit BELOW the armor belt -- we think. It could have hit the lower end of the armor belt BUT when a high explosive warhead goes off, for a split second its initial fireball is heavier than water, and drops down a foot or two before expanding into a larger explosive force. After WW II we were able to confirm that theory in tests using ultra high speed underwater cameras. This is especially true with mines (anchored or free floating) that have an air chamber on top so they would rise to the surface.

    Hmmm. That just gave me an idea for a Naval Quiz question.
    Able to leap tall tales in a single groan.

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    Thank you very much for your response.

    What are your thoughts about the practice of the Royal Navy (and IJN) where they place their powder magazines under the shell room? It also seems like they put each individual powder bag inside a metal container to protect it from fire. Do you believe this is safer than the method that the USN battleships use?

    Since I'm in Irvine I might want to drop by the Iowa some time, since she's quite close.

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    Quote Originally Posted by Radical View Post
    Thank you very much for your response.

    What are your thoughts about the practice of the Royal Navy (and IJN) where they place their powder magazines under the shell room? It also seems like they put each individual powder bag inside a metal container to protect it from fire. Do you believe this is safer than the method that the USN battleships use?

    Since I'm in Irvine I might want to drop by the Iowa some time, since she's quite close.
    I'm not that familiar with foreign ships. Us "yankees" always strived to make OUR warships better. Well, it's just our nature. If it works, can we make it work better? All of our powder bags were stored (originally) in steel cannisters - 3 bags per cannister. To conserve on weight (and better qualities of Aluminum) they are stored in Aluminum cannisters.

    I have a Corel drawing I made up of the cannisters but don't know how to post it on this web site.

    Perhaps on the way down to the Iowa, you can stop by my house and do it for me.

    I was on a full ammo load out of the New Jersey in Seal Beach once. It's amazing how well the crew worked like a Swiss Watch. We loaded up all 16-inch magazines (bullets & powder), all 5-inch magazines and all 20-mm Gatling magazines in about 8 hours. The ship's photographer took pics of the whole thing as we also had a representative from the Earl Naval Weapons Handling Center observing the load out.

    Unfortunately, the only set of prints made were left on a desk over lunch and mysteriously dissappeared. I really wanted a set because the last two top rows of 16-inch powder cannisters were too high for the monorail. The cannisters had to UNLOADED outside of the magazine and the cannister manually set in place. Then each 110 lb powder bag "chain ganged" in and manually stuffed into the cannister. Some of them had too many cardboard seperators between the bags so one GM would chin himself on the monorail and "kick" the last bag in so they could close and screw down the lock of the cover.

    Ah! The good-ole- days.
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    Thank you very much for your response. I visited the Iowa two days ago, and it was truly a sight to behold. It's difficult to appreciate the sheer size of it until I saw it in person.

    Do you know what is the outer hull plate thickness forward and aft of the armored citadel? As I understand, around the armored citadel the hull thickness is 1.5" (60 lbs) STS. How thick is it on the bow in front of the citadel?

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    Rusty, how do you add armor\protection that spans many bulkheads\frames when you already have the ships structure in place? With the ships existing structure already attached to the existing armor, is the added armor just placed where it is needed in sections between the bulkhead\frames and fastened in place?

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    Quote Originally Posted by Ken_NJ View Post
    Rusty, how do you add armor\protection that spans many bulkheads\frames when you already have the ships structure in place? With the ships existing structure already attached to the existing armor, is the added armor just placed where it is needed in sections between the bulkhead\frames and fastened in place?
    There are various ways of adding extra armor topside. For the radio center on main deck, we merely added 1" thick HY-80 over the 1/4" thick Medium Steel (MS) bulkheads. BUT we also but we also torched out big X's in the MS bulkeads and welded them to the inside surfaces of the HY-80. This also helped flatten out the oil panning of the MS plating giving a tad more room to mount the "J" racks.

    After removing the four aft 5"/38 gun mounts, to make way for the armored control and equipment rooms for the Tomahawks, we merely kept the 5"/38 upper handling rooms as they were already 2 1/2" thick of STS. The ammo stowage rooms for the 20mm CIWS were new construction, BUT for the forward Gatlings (Mounts 21 & 22) we used the existing 40mm platform.

    CEC was a whole different animal however. Where the 1 1/2" HY-80 could rest its weight on a deck, the forward two thirds had no deck support. With no structure holding it up, I could not count on only outside welds to be strong enough to take even a Grade B shock. So between the frames of the existing 3/8" MS bulkheads I cut the plating out 2 to 3 inches from the stiffeners. Now the armor could also be welded on the INSIDE as well as the outside.

    I remember one of the officers asking me why we were cutting out holes in the bulkheads and he was very pleased with the above explanation. He also asked where did I learn all that stuff about armor. Of course I answered that I was a shipfitter for 10 years plus a tank crewman in the Army Reserves for over 6 years. Therefore i like lots of THICK STUFF between me and incoming.

    Check page 244 of my "yellow" book.
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    Rusty, do you know the thickness of the hull plates on the bow?

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    Quote Originally Posted by Radical View Post
    Rusty, do you know the thickness of the hull plates on the bow?
    I'm a little pooped out right now, but you can look up the cross sections in a Booklet of General Plans. That will be close enough except for the bulbous Paravane eye at the Forefoot Skeg (which I had removed from the New Jersey and inserted with 3/4" thick Medium Steel). See pages 204 & 205 of my "yellow" book.

    The only thicknesses of hull plating NOT identified in the BGP are strakes M and N where they are 1 1/2" thick Special Treated Steel to serve as trigger plates for surface torpedoes and/or free floating mines or even bullets from strafing planes. That thickness of STS will stop 40mm rounds so anything a fighter plane can carry is smaller. I think the biggest guns ever carried on a single engine combat plane were 32mm anti-tank guns on JU-87 Stuka dive bombers. Hans Rudel was credited with knocking out over 500 Russian tanks with those guns. BUT, he still had to aim for the REAR of the tanks where the armor is lighter to provide service "hatches" over the engines.
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    I just found the plans. These are great and I didn't even know they existed. Thank you very much for the reference. It seems like most of the strakes in the bow at 25# (0.625") MS. Is there a reason for using Mild Steel instead of HTS or STS in the bow section? Since it looks quite thin I would have thought that it used thicker plates.

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    Rusty, do you know why the outer part of the deck armor is 7" (5.75" Class B + 1.25" STS) while the inner part is 6"? It seems almost counterintuitive because wouldn't the inner part cover more of the ships vitals?

    Edit: fixed math error, it's combined 7".
    Last edited by Radical; 17 Aug 16, at 12:23.

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