A Solution to the Inherent List on Nimitz Class Aircraft Carriers

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density. It was also discovered at this early stage of analysis that for corrections at or beyond 1.5 degrees, <strong>the</strong> 2" deck was a much better location for this ballast addition due <strong>to</strong> <strong>the</strong> lesser weight addition resulting from <strong>the</strong> larger moment arm generated by filling <strong>the</strong> 2"'' deck voids. The costs associated with adding ballast <strong>to</strong> <strong>the</strong> 2"'' deck is much higher, but <strong>the</strong> amount of ballast required is significantly less than that required for <strong>the</strong> 4"" and 8"' decks. For corrections less than 1.5 degrees, <strong>the</strong> 2" deck and <strong>the</strong> 8"" decks have a fairly comparable weight addition, however, ballasting <strong>the</strong> 8' deck tanks costs significantly less. The complete preliminary cost comparison for <strong>the</strong> 2"^ 4*^, and 8'" decks is found in Appendix D. Adding ballast <strong>to</strong> <strong>the</strong> 2"'' deck voids does increase KG and thus reduces <strong>the</strong> KG service life allowance margin; however, <strong>the</strong> increase seen is fairly small. In fact, as shown in Appendix D, a 1.5 degree list correction results in approximately a 0.1 percent KG increase. On average, <strong>the</strong> Nimitz class carriers currently have a KG of 47 feet, as shown in Table 1. The goal KG service life allowance is not <strong>to</strong> exceed 48.5 feet. Thus, <strong>to</strong> fix an inherent list of 1.5 degrees, <strong>the</strong>re would be a .05 foot increase in KG. 34
2.4 Structural Analysis One tank on each deck was chosen for structural analysis due <strong>to</strong> <strong>the</strong> geometrical similarities between tanks. Analysis was performed on any existing shell and/or deck plating, as well as all longitudinal and transverse bulkheads for <strong>the</strong> tank chosen from each deck. The volume of each tank was obtained from POSSE so that <strong>the</strong> weight of Perma Ballast® required <strong>to</strong> fill <strong>the</strong> entire tank could be calculated in I<strong>to</strong>ns. The density used for all <strong>the</strong> Perma Ballast® calculations was 200 Ib/ft^. All structural calculations are located in Appendix E. All surface ships shall be designed <strong>to</strong> withstand a number of loading conditions including ship motion loads. Ship motion loads are defined by [6] as <strong>the</strong> inertia forces and gravity components resulting from <strong>the</strong> motion of <strong>the</strong> ship in a seaway. The ship motion fac<strong>to</strong>rs for this analysis were obtained from Naval Sea Systems Command's Ship Survivability Division. Although <strong>the</strong>se fac<strong>to</strong>rs will vary slightly depending on location, <strong>the</strong>y were assumed <strong>to</strong> be constant. They are as follows: Ship Motion Fac<strong>to</strong>rs: V:=1.25 Vertical A := 0.75 Athwartship F := 0.4 Fore/Aft Once <strong>the</strong> ship motion fac<strong>to</strong>rs were applied <strong>to</strong> each direction respectively, <strong>the</strong> <strong>to</strong>tal normal force could be calculated. The force affecting <strong>the</strong> structural analysis was dependent on <strong>the</strong> location of <strong>the</strong> deck or bulkhead being analyzed. For example, <strong>the</strong> <strong>to</strong>tal force acting on <strong>the</strong> 2" deck's sponson shell plating had <strong>to</strong> be resolved from both a vertical and athwartship force. The resulting pressure, or equivalent head, on <strong>the</strong> plating was <strong>the</strong>n found using this resolved normal force. Each tank was based on a 95% usable volume <strong>to</strong> account for structural internals or utilities running through <strong>the</strong> space. 35
Page 1 and 2: A Solution <strong
Page 3 and 4: A Solution <strong
Page 5 and 6: Table of Contents Abstract 3 Acknow
Page 7 and 8: 1.0 Introduction 1.1 Motivation Air
Page 9 and 10: class. Changes to
Page 11 and 12: classified into fo
Page 13 and 14: o Control the KG g
Page 15 and 16: the intact stabili
Page 17 and 18: for ships propulsion, respectively.
Page 19 and 20: combined with the
Page 21 and 22: 1.3.7 Ballast Addition 1.3.7.1 Wate
Page 23 and 24: 2% entrained air (by volume) in <st
Page 25 and 26: Tank name Tank volume Ballast type
Page 27 and 28: was successfully performed and <str
Page 29 and 30: of each tank's location was added,
Page 31 and 32: 2.3 Preliminary Decision-Making Cos
Page 33: All further costin
Page 37 and 38: this pressure. This resulted in a r
Page 39 and 40: 2.4.1 Structural Modifications 2.4.
Page 41 and 42: Main Deck Shell FR 165 - FR 180 Tra
Page 43 and 44: 2.4.1.3 Modifications to</s
Page 45 and 46: 3.1 Final POSSE Results The minimum
Page 47 and 48: Table 6: Final Cost, Weight Additio
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Page 51 and 52: 5.0 Recommendations 1. As can be se
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structural Analysis for Compartment
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Resulting Pressure on Sponson Plati
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Calculations to De
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Stress Calculations: k = coefficien
Page 97 and 98:
Page 99 and 100:
FR 165 - FR 180 Transverse Bulkhead
Page 101 and 102:
Design of Plating for Surface Ships
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Page 105 and 106:
Main Deck Shell FR 165 - FR 180 Tra
Page 107 and 108:
Calculations to De
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Page 113 and 114:
Calculations to De
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Calculations to De
Page 121 and 122:
Stress Calculations: Stiffening k =
Page 123 and 124:
Resulting Pressure on Shell Plating
Page 125 and 126:
Calculations to De
Page 127 and 128:
Stress Calculations for 227 I<stron
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Resulting Pressure on Inner Longitu
Page 131 and 132:
Calculations to De
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Page 135 and 136:
Page 137 and 138:
Stress Calculations k = coefficient
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Resulting Pressure on Transverse Bu
Page 141 and 142:
Calculations to De
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MATERIAL WORK SHEET PERMA BALLAST®
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A Solution to the Inherent List on Nimitz Class Aircraft Carriers

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