A Solution to the Inherent List on Nimitz Class Aircraft Carriers

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Table 5: Required Structural Modifications for 8-225-6-V Ship Structure Structural Modiflcations Shell Plating Inner Longitudinal Bulkhead (Shaft Alley Bulkhead #4) Outer Longitudinal Bulkhead (Bulkhead #3) Transverse Bulkhead (Frame 225) Transverse Bulkhead (Frame 230) No modifications required Add 5 vertical stiffeners (5" X 4" X 7.5# X T) (MS) Max Panel Plating Size: 24" X 114" Add 5 vertical stiffeners (5" X 4" X 7.5# X T) (MS) Max Panel Plating Size: 24" X 87" Add 4 vertical stiffeners (5" X 4" X 7.5# X T) (MS) Max Panel Plating Size: 15" X 114" *Note-panel height is dependent on trapezoidal geometry Add 4 vertical stiffeners (5" X 4" X 7.5# X T) (MS) Max Panel Plating Size: 15" X 114" *Note-panel height is dependent on trapezoidal geometry 3.0 Final Analysis and Results This project design spiraled <strong>to</strong>ward finding <strong>the</strong> most cost effective and advantageous solid ballasting solution for correcting <strong>the</strong> inherent list on <strong>the</strong> Nimitz class carriers. The preliminary decision-making cost estimation proved that <strong>the</strong> 200 Ib/ft^ density was <strong>the</strong> most cost effective for <strong>the</strong> same amount of ballast weight. The 325 Ib/ft^ ballast was so much more expensive, that although <strong>the</strong> number of tanks required <strong>to</strong> ballast with 200 Ib/ft^ was higher, it was still more cost effective <strong>to</strong> use <strong>the</strong> 200 Ib/ft^ density ballast. Once <strong>the</strong> structural analysis was complete, <strong>the</strong> minimum ballasting weights that were found had <strong>to</strong> be analyzed in POSSE again. For this analysis, <strong>the</strong> 4'*' deck was eliminated completely due <strong>to</strong> its structural limitations. Similarly, any required structural modifications that were not already included in <strong>the</strong> cost estimations had <strong>to</strong> be taken in <strong>to</strong> account for both <strong>the</strong> 2"'' and S"' decks. 44
3.1 Final POSSE Results The minimum amount of 200 Ib/ft^ ballast that could be added <strong>to</strong> compartment 2-165-8-V was found <strong>to</strong> be 281 I<strong>to</strong>ns which corresponds <strong>to</strong> 79% of that compartment's <strong>to</strong>tal capacity. Up until this point, all tanks had been analyzed <strong>to</strong> 95% of <strong>to</strong>tal capacity due <strong>to</strong> structural internals or possible utilities running through <strong>the</strong> space. Structural analysis was <strong>the</strong>n performed for compartment 2-180-6-V. A minimum ballast weight of 448 I<strong>to</strong>ns was calculated so that <strong>the</strong> maximum pressure design criterion of 1000 psf was not violated. Because less ballast could be added <strong>to</strong> <strong>the</strong>se tanks, <strong>the</strong> POSSE analysis had <strong>to</strong> be expanded <strong>to</strong> include compartment 2-250-4-V. These new results for <strong>the</strong> 2""^ deck had little effect on KG and only enhanced <strong>the</strong> aft trim correction. The minimum amount of 200 Ib/ft^ ballast that could be added <strong>to</strong> compartment 8-225-6-V was 227 I<strong>to</strong>ns. This was calculated <strong>to</strong> avoid performing structural modifications on <strong>the</strong> ship shell plating. As a result, only 90% of that compartment's <strong>to</strong>tal capacity could be utilized which was 5% less than originally analyzed in POSSE. This time, ra<strong>the</strong>r than perform a structural analysis on all <strong>the</strong> 8* deck voids, a maximum capacity thumb rule of 90% was applied <strong>to</strong> all <strong>the</strong> 8"' deck voids. As a result, different tanks were selected and analyzed <strong>to</strong> achieve <strong>the</strong> least I<strong>to</strong>n addition for <strong>the</strong> same incremental change in degrees. Again, this had little effect on KG and change in trim. A table providing POSSE modeling results in a combat load condition for list correction in half degree increments up <strong>to</strong> 3 degrees for 200 Ib/ft^ is included in Appendix F. This information includes: • Tank name • Tank volume 45
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Page 3 and 4: A Solution <strong
Page 5 and 6: Table of Contents Abstract 3 Acknow
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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
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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 and 34: All further costin
Page 35 and 36: 2.4 Structural Analysis One tank on
Page 37 and 38: this pressure. This resulted in a r
Page 39 and 40: 2.4.1 Structural Modifications 2.4.
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Page 47 and 48: Table 6: Final Cost, Weight Additio
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FR 165 - FR 180 Transverse Bulkhead
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Design of Plating for Surface Ships
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Main Deck Shell FR 165 - FR 180 Tra
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Calculations to De
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structural Analysis for Compartment
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Calculations to De
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Calculations to De
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Stress Calculations: Stiffening k =
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Resulting Pressure on Shell Plating
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Calculations to De
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Stress Calculations for 227 I<stron
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Resulting Pressure on Inner Longitu
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Calculations to De
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Stress Calculations k = coefficient
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Resulting Pressure on Transverse Bu
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A Solution to the Inherent List on Nimitz Class Aircraft Carriers

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