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M. G 3. Z 3. Z. G. Z 2. G 2. B. B 1. Lesson 4.3. Loose Water. References. NSTM 079 Volume 1 NTTP 3-20.31 Damage Control Book, section II (a). ENABLING OBJECTIVES. Explain why FSE impairs stability. Compute FSE. List methods to reduce FSE. Explain why FCE impairs stability.

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  1. M G3 Z3 Z G Z2 G2 B B1 Lesson 4.3 Loose Water

  2. References • NSTM 079 Volume 1 • NTTP 3-20.31 • Damage Control Book, section II (a)

  3. ENABLING OBJECTIVES • Explain why FSE impairs stability. • Compute FSE. • List methods to reduce FSE. • Explain why FCE impairs stability. • Compute FCE. • Describe pocketing, surface permeability, size of hole, and venting on FSE and FCE. • Correct stability curve for FSE and FCE.

  4. CLASS TOPICS 1. Free Surface Effect2. Example3. Free Communication Effect4. Example

  5. M M M M M M G G G G G G Z B B B B B B B1 B1 B1 B1 B1 FREE SURFACE EFFECT

  6. M M M M M M G3 Z3 G2 Z G G G G G G2 G2 G G2 Z2 G2 G2 B1 B B B B B B1 B1 B1 B1 B1 B FREE SURFACE EFFECT GZ2 = GZ3

  7. M G3 G B B1 GG3

  8. B3 x L MOMENT OFINERTIA = FSE= SHIP'S DISPLACED VOLUME 12 x 35 x Wf = FREE SURFACE EFFECT B= BREADTH OF COMPTL = LENGTH OF COMPTWf = SHIP'S DISPLACEMENT

  9. POCKETING - SHALLOW

  10. POCKETING - ALMOST FULL

  11. POCKETING (NO POCKETING EXISTS)

  12. SURFACE PERMEABILITY

  13. SLUICE VALVES - Closed

  14. SLUICE VALVES - Open

  15. FREE SURFACE EFFECT • Independent of the depth of the liquid • Greater w/ increased length and width of the compartment • Increases as draft decreases (de-ballasting) • Can be reduced by pocketing

  16. CLASS TOPICS 1. Free Surface Effect2. Example3. Free Communication4. Example

  17. AFT STBD 25 FT 4 FT PORT 30 FT FWD Wo = 3500 LT FSE?

  18. FSE = (30 FT)3 x 25 FT 12 x 35 FT3/LT x 3585.71 LT FSE = 675000 FT4 = 1505998.2 FT3 FSE = B3 x L 12 x 35 FT3/LT x WF .45 FT

  19. CLASS TOPICS 1. Free Surface Effect2. Example3. Free Communication4. Example

  20. M G B FREE COMMUNICATION EFFECT FREE COMMUNICATION EFFECT

  21. M G B FREE COMMUNICATION EFFECT FREE COMMUNICATION EFFECT

  22. M G5 Z5 G3G5 G3 G Z4 B G2 G4 B1 FREE COMMUNICATION EFFECT

  23. FREE COMMUNICATIONEFFECT Bx L x Y2 FCE= 35 x Wf B = BREADTH OF COMPTL = LENGTH OF COMPTY = DIST FM SHIP C/L TO COMPT COG.Wf = SHIP'S DISPLACEMENT

  24. FREE COMMUNICATION EFFECT(All 3 must exist) • COMPARTMENT OPEN TO THE SEA • COMPARTMENT PARTIALLY FLOODED • COMPARTMENT OFF-CENTERLINEOR “UNEVEN” ABOUT THECENTERLINE

  25. . . . Y = 0 NO F.C.E. • COMPARTMENT OPEN TO SEA • COMPARTMENT PARTIALLY FLOODED

  26. Free Communication Effect • Size of the hole will reduce FCE. (Formula assumes entire skin of ship is “open to sea”) • Venting will reduce FCE. (More air transfer = more water “communicating” into the compartment.) • Increases as draft decreases (de-ballasting) • Can be reduced by pocketing

  27. CLASS TOPICS 1. Free Surface Effect2. Example3. Free Communication4. Example

  28. Wo= 2880 LT L = 28 FT Depth = 4 ft B = 29 FT 40 ft 20 ft y = 20 ft – 14.5 ft y = 5.5 ft 28 FT 14.5 ft 29 FT wFLOODING = 28 FT * 29 FT * 4 FT 35 FT3/LT wFLOODING = 92.8 LT WF = W0 +wFLOODING = 2972.8 LT

  29. 29 FT x 28 FT x (5.5 FT)2 35 FT3/LT x (2880 LT + 92.8 LT) FCE = 24563 FT4 104048 FT3 FCE = B x L x (y)2 35 FT3/LT x WF FCE = .24 FT

  30. Quiz… • Why does FSE impair stability? • ANS: Horizontal weight shifts off centerline cause a “virtual rise” in G, reducing GM. • Factors that reduce FSE? • ANS: Compartment size, pocketing, baffle plates, surface permeability, sluice valves, venting. • Which variable is the “determining factor” in the FCE equation? • ANS: “Y” the distance from the ship’s centerline to the compartments center… it is squared.

  31. Quiz… • What three factors must be present for FCE to exist? • ANS: 1) Off centerline or Uneven about centerline. 2) Open to the sea 3) Partially flooded.

  32. Instructor will now… • Assign Practice Problems for lesson 4.3 (Stability Problems #4, #7. Try problems #8, #11) • Read Student Guide!! • Homework # 2 Due end of class TODAY!

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