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  • Structural design

    I hope Rusty Battleship can confirm my understanding on how Iowa is structurally built.

    First the side armor - The class A plates and B plates are keyed together and then have a backing plate of either 0.825 or 0.625" STS with 2" of cement inbetween. This backing plate stops at the lower edge of the class A plate. The bolts attaching the class A plate to the backing plate have thick rubber gaskets to help with shock forces. Then the entire system is buttressed from the main armored deck to the top of the triple keel. The buttress is bolted/riveted/ or welded to its adjacent plates from above, side and below so there is no natural weak spot that is waiting for failure. Is this correct?

    Each torpedo bulkhead being a continous longitudinal bulkhead that is over 2/3rd of the ships length acts as a strength bulkhead to the ships box girder. The armor plates being interlocked will also act as a strength bulkhead as any hogging motion would place the plates into compression which these plates would resist considerably. Any sagging motion would place the plates into tension which would need to break the interlocking keys and the backing plates in order to sag significantly. Is this correct?

    The main turrets and barbettes are supported by the keel which has transverse and longitudinal bulkheads underneath them. These structures help support the weight from underneath and to the ships sides. The upper decks do not have to support the weight of the turrets as they are not really attached. This off loads the upper hull structure from attempting to support their weight. They do play a role in keeping the barbette structure vertical being pressed up against them with a weather seal making up the last couple inches of space. So the upper strength decks support the barbettes and turrets from sideways motions and not up and down motion. Is this correct?

    The keel is made up of the central "I" beam but additional "I" beams run parallel for the entire ships length. The triple bottom is made to the grillage system box grid with intercostal plates all bolted/riveted/or welded on all four sides to their adjacent plates again leaving no natural weak spot. Under each turret the supporting structure in effect gives the ship a quadruple keel under each turret. Is this correct?

    Her hull girder as three upper strength decks being the main, second, and third decks in which the second deck is by far the strongest with the class b deck plates also being keyed together. Is this correct?

    In effect her sides because of the fully developed side protection she has 8 strength bulkheads with the armored 3rd bulkhead being the strongest for longitudinal strength. Since this bulkhead also extends to the main armored deck it directly supports this upper strength deck. Is this correct?

    The ship has three lower strength decks which make up her triple bottom. This box girder would be extremely difficult or resistant to bending forces such as hogging or sagging. This is one reason she tends to sink her bow in rough weather along with the bow does not have much buoyancy within it. Is this correct?

    If her keel took some form of damage her sides and upper strength decks are so strong they can support her weight.

    Case in point - Arkansas on test Baker at 0.22 seconds after detonation her keel was impacted with a force of 7,000 psi. Her superstructure was seen to collaspe at 0.38 seconds after detonation but this structure had been badly damaged by test Able.

    Her keel is crushed into the hull in places over six feet deep. Both starboard propeller shafts and both rudders were ripped off her hull and are gone. The ship was lifted by the explosion into the air and was lost from sight 1 second after detonation. At some point when the water moving skyward slowed to a point it could no longer support her weight she fell upside down and landed on the sea floor smashing what was left of her superstructure into the mud. Her turrets are still within the barbettes but her keel at each of her turret locations shows that the keel was bent in and out about 2 feet. Even with a totally destroyed keel almost her entire ship length the ship showed no sign of bending, twisting, or distortion and is was found intact. The rivets and seams of her bottom plating suffered severe damage with most failing.

    Arkansas suffered crush damage to her keel and not the typical hog/sag that would break the ship in half. In fact her side armor plates are only cracked on both sides in one place forward but not pulled apart. Even when the ship was essentially in mid air with a crushed keel and absolutely no support her upper strength decks did not bend. So what held Arkansas together? I have more detailed information on the damage at specific frames if you wish me to post it.

    If my understanding of how Iowa is constructed is correct then it would be virtually impossible for the ship to suffer a total structural failure and break in half due to a conventional mine or torpedo exploding below her keel. Ships with fully developed side protection in this case suffer local crush damage to the keel which attempts to limit the size of the hole in the keel and her subdivision will contain flooding. A single conventional warhead will not destroy enough of her structural integrity so that the chance of a total structural failure seen in destroyer type ships is basically impossible.

    Shock damage can be severe but she was built to withstand a shock of about 2,000-3,000 ft lbs. Is this correct?

  • #2
    Boy! You sure have a lot of questions and are rather close on your theories.

    To begin with, only the conical shaped foundation (1.5" STS) goes down to the 2nd Platform to tie into the ship's structure. The Class A armor barbette only goes down the 2nd Deck. From 2nd to 3rd deck it's an STS cylinder. Under the 3rd deck there is a circular "I" beam for support called a Carlin Beam.

    2nd Deck Armor is not keyed into place but attached by "Quilting Pins" to the actual 2nd Deck plating underneath.

    Therefore, the Main Deck is still the uppermost structural deck of the "box girder" being 1.5 " of STS plate for most of it's length.

    The Class A armor and Class B armor making up torpedo Bulkhead 3 are actually bolted to a structural bulkhead of STS. Therefore hog is drastically reduced.

    It is true that the torpedo bulkheads are long enough and strong enough to provide extra strength to the centerline keel. In effect she really is a triple keeled ship.

    It's not just the stiffness of the ship that causes it to "dive" into the next wave but the length of the ship and the low freeboard (only 18 feet amidships).

    That's all I'm going to answer for now as I need a nap. This is the 3rd day the roofers have been on my house and still trying the find the bowling balls they keep dropping on it.
    Attached Files
    Able to leap tall tales in a single groan.

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    • #3
      Its like standing on the floor (powder magaizine) and looking up at an opera theaters balconies. The balconies would be your upper shelf shell storage for what is not lashed on the upper shell flats proper to the bulkheads. And yes it does have an echo too.;)

      You should see the fire protection system layout. It resembles something that the three stooges would build but it works quite well for flooding the magazines all in a circular waterfall of water.
      Last edited by Dreadnought; 10 Jun 09,, 21:03.
      Fortitude.....The strength to persist...The courage to endure.

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      • #4
        It's not just the stiffness of the ship that causes it to "dive" into the next wave but the length of the ship and the low freeboard (only 18 feet amidships)


        *Wave frequency, subject to change pending the waterway (ocean) Atlantic and Pacific are very different indeed as compared to the Med.
        If it matches the length of the ship it can be thrown around like a toy in your bathtub.
        Fortitude.....The strength to persist...The courage to endure.

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        • #5
          Gonna throw these two links in here. This was the rebuilding of the BB's from Pearl Harbor damage. Some interesting shots. Enjoy.

          YouTube - Pearl Harbor Salvage Of The Revenge Ships Part 6

          YouTube - The Revenge Ships Of Pearl Harbor - Part 7
          Fortitude.....The strength to persist...The courage to endure.

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          • #6
            Flag Bridge

            I know this is slightly off subject but does anyone know how thick South Dakota's exterior bulkheads are to her Flag Bridge superstructure? I believe it is made up of 0.75 or 0.625" STS or HTS.

            If correct I believe I may be able to show a 7th 14-inch shell hit on South Dakota or hit 5 in the BuShips report. The photo present within this report only shows fragment damage to the 40mm director. This damage in her action report is spead out over three pages and is difficult to read. The damage blew a 6 x 6 foot hole into the bulkhead. If I can locate a photo at the National Archives of the actual impact sight in which there are many more photos in her records so there is a good possibility I may be able to show more proof.

            Rob

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            • #7
              R@L - Puget Sound Naval Shipyard USS South Dakota Damage Report, June 19, 1944

              Her damage report from bombing.

              http://www.dcfp.navy.mil/mc/museum/War_Damage/57.pdf

              Her damage report from gunfire at Savo.

              http://www.dcfp.navy.mil/cgi-bin/War...ls=3&PgConst=9

              Pictures that go along with the gunfire damage.;)
              Last edited by Dreadnought; 12 Jun 09,, 17:26.
              Fortitude.....The strength to persist...The courage to endure.

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              • #8
                Print showing location of damage due to gunfire.

                WWII War Damage Reports Gallery
                Fortitude.....The strength to persist...The courage to endure.

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                • #9
                  Bomb Damage

                  This report is her bomb damage in 1944. Though the bomb detonated on the first superstructural deck close to the frames of the Flag Bridge level it still does not give me the thickness of the exterior bulkhead of the Flag Bridge itself.

                  The shell damage in 1942 blew a hole 6 feet by 6 feet and then blew out the interior bulkheads for the Admiral's cabin and a Senior Officer's cabin. It sent shrapnel down into the 1st superstructural deck over 45 fragments ranging from 0.5" to 4" in diameter some penetrating the steel deck below the teak. It also punctures a hatch with 11 shrapnel holes, sent shrapnel and demolished the 40 mm director and more shrapnel onto the navigation level bridge. Blew out three heat treated windows and destroyed the raising and lowering mechanism. The full description in her action reports is mixed up over three pages. On Plate 1 of the 1942 BuShips report is drawing showing where all the hits took place. Hit 5 which is the one I am now investigating is shown on the drawing as a rather large diameter hole in the side of her superstructure. This alone is not proof. However if the hole is 6 feet by 6 feet in a 0.75" STS plate only a nose fuzed 14-inch projectile would have the explosive charge to blow a hole that large into that size plate. A 8-inch noze fuzed shell will blow a hole about 26" in diameter and an 8-inch AP shell would not have detonated on impact nor its 7-8 lbs of powder can produce the damage inflicted.

                  Why I missed this shell hit is because the photo in the BuShips report shows shrapnel damage to the 40 mm director which I assumed was the impact sight and the damage to the director is simply too small. I am writing an article on South Dakota so I have been re-visiting her reports and realized the descriptions for this damage actually was spread out over three different pages within her action report making it a bit confusing. If I can find a photo of the true impact point then I believe I will have the evidence to prove what I suspect.

                  The cruisers opened so late and fired so few shells at South Dakota that the original 16-18 estimated 8-inch hits is illogical. Many of these are simply documented has happening long before the heavy cruisers ever sighted South Dakota much less actually opening fire at her. Radar plot is an example.

                  Kirishima estimated she hit South Dakota with ten 14-inch shells. If I am correct this would bring confirmation of 7 hits by Kirishima's main battery. She most likely added another 12-13 hits from her secondary and the total number of hits made on South Dakota was actually 32 not 26.
                  Last edited by lundgrenr; 12 Jun 09,, 17:59.

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                  • #10
                    This report is her bomb damage in 1944. Though the bomb detonated on the first superstructural deck close to the frames of the Flag Bridge level it still does not give me the thickness of the exterior bulkhead of the Flag Bridge itself.

                    *Only two ways to figure that out.

                    1) Obtain her blueprints on CD from Navsea.
                    2) Have a look at either Alabama or Massachusetts since they are museums and of the same class.

                    *Keep in mind though her plating could have been upgraded during refit after Savo's battle. Many times in order to find this you have to have the prints and any following revisions.
                    Fortitude.....The strength to persist...The courage to endure.

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                    • #11
                      Will do

                      I have actually just ordered more of her builder's blueprints. Ironically her action report is very good at listing the plate thickness and type of steel yet for this hit it does not.

                      I was just hoping someone might know. Not to worry I will get the data.

                      Rob

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                      • #12
                        Originally posted by lundgrenr View Post
                        I have actually just ordered more of her builder's blueprints. Ironically her action report is very good at listing the plate thickness and type of steel yet for this hit it does not.

                        I was just hoping someone might know. Not to worry I will get the data.

                        Rob
                        Rob,

                        I'm glad to see you back at your research. You certainly come up with some fascinating stuff.

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                        • #13
                          Research,

                          Thanks Hoss,

                          I hope to return to the National Archives soon. There are a significant number of photos that have to my knowledge never been published showing South Dakota's damage. Since all are in the public domain there is no problem publishing them.

                          The blueprints came in on Friday and they will help me show how the shells ripped through her superstructure and which compartments they traveled through which are listed.

                          Hit 5 I missed because I assumed the photo of the 40 mm director was the impact point and the damage is not that great. Writing a technical article for Tony D on another web site on South Dakota's damage I realized this hit's damage was actually spread out over three pages in different locations and again this was one reason I missed this one.

                          On the starboard side on the second deck level is a senior staff officer's cabin and on the port side the Admiral's cabin. The shell blew out the senior staff's bedroom, bathroom, closets, into the passage and then blew out the seperating bulkheads to the Admiral's cabin on the port side. I'll be able to show this now that I have the blueprints.

                          Then on the flag bridge level in blew out windows, bulkheads, and the 40 mm director. On the 1st superstructural deck it sent shrapnel over 45 in one location and 11 through a hatch with some penetrating the steel deck.

                          In most area's where her superstructure is listed it runs between 0.75 inches and in some places 1.25 inches near her main gun range finder of STS plate.

                          The only shell that will blow a 6 by 6 foot hole in plates this thick that were present would be a 14-inch type 0 shell. I still want a photo and I believe I remember some including interior shots of the cabins. This was about 5-6 years ago but I know exactly how to pull her files.

                          The other hit I am interested in is hit 25 or the hit that dug into her main belt 8 inches. Her report says the exterior hole was 5 inches but this is inconsistent as a 5 inch common shell would shatter on her main belt. The estimate of an 8-inch shell is certainly possible but the exterior hole should be at least 8 inches in diameter. However the cap head should have been removed which was designed to come off under any impact and again her shell body should have shattered.

                          If the 5 inch hole listed is a miss-print and should read 15 inches a 14-inch shell certainly could have dug into the plate 8 inches deep. At the range and target angle a 14-inch shell could not penetrate the main belt even at 2,000 yards.

                          Please understand at this point I am just suspicious and in no way am I saying I am correct. I need more evidence and need photos. There are simply inconsistencies in the data and South Dakota estimated two 14-inch shell hits but never identifies the second hit. Lee also said two 14-inch shell hits but again never identifies the second hit.

                          The additional 6 hits are below hit two. Originally estimated by her crew as 6-inch shell hits BuShip's explained them away as coming from a cap head of an 8-inch AP shell that made hit two. Well hit two was made by a 14-inch type 0 so no cap head would be present but take a moment to consider this. How can a single cap head make 6 new entry holes? Did it reverse course exit out the original entry hole reverse course penetrate the hull and reverse again and do this 5 more times? The estimate is silly. The hits match 6-inch nose fuzed projectiles perfectly which was the original crew's estimate. A salvo from Kirishima.

                          I have more but hope to lay it all out soon.

                          To Rusty battleship did you have any more to add about the original topic and why Arkansas stayed intact and Iowa's ability to resist underwater damage?

                          Rob

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                          • #14
                            IMO, Its all determined by what the USN will call battle damage. Hits and fragments are two different things but it all comes down to nomenclature and who did the inspections. This may give a reason as to why the numbers dont match.;)
                            Fortitude.....The strength to persist...The courage to endure.

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                            • #15
                              Rob,

                              I'm familiar with your writings on the "other web site" and of Tony D's work as well. That's why I'm glad to see you back at it. You seem to do some very thorough work and I enjoy reading it. Keep at it!

                              Hoss

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