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VESSEL STABILITY

VESSEL STABILITY

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VESSEL STABILITY

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  1. VESSEL STABILITY CANADIAN COAST GUARD AUXILIARY - PACIFIC

  2. Principles of Stability

  3. Definitions

  4. Definitions Stability - the tendency of a vessel to rotate one way or the other (to right itself or overturn) Initial Stability - the stability of a vessel in the range from 0° to 7°/10°

  5. Definitions Overall Stability - a general measure of a vessel's ability to resist capsizing in a given condition of loading Dynamic Stability - the work done in heeling a vessel to a given angle of heel

  6. Six Motions Of A Ship Roll – side to side or port to starboard. (Rotate about longitudinal axis) Pitch – up down or bow to stern. (Rotate about transverse axis) Yaw – twisting (rotate about vertical axis) Sway – “sliding” laterally or side to side Heave – up down as in lifted by waves. Surge – “sliding” longitudinally or front back

  7. Definitions ROLL - The action of a vessel involving a recurrent motion (Longitudinal Axis). Semi-permanent angle of inclination, caused by external forces. HEEL - LIST - Permanent angle of inclination caused by a shift in the center of gravity, -GM, or both.

  8. Laws Of Buoyancy • • A floating object has the property of buoyancy • A floating body displaces a volume of water equal in weight to the weight of the body.

  9. G 00 DISPLACEMENT Capital W =

  10. G B 04 DISPLACEMENT Capital W =

  11. G B 09 DISPLACEMENT Capital W =

  12. G DISPLACEMENT B 16 Capital W =

  13. G DISPLACEMENT B 20 Capital W =

  14. Laws Of Buoyancy • A floating object has the property of buoyancy. • A floating body displaces a volume of water equal in weight to the weight of the body. • A body immersed (or floating) in water will be buoyed up by a force equal to the weight of the water displaced.

  15. Displacement • The weight of the volume of water that the ship's hull is displacing • Units of weight long ton = 2240 lbs short ton = 2000 lbs metric tonne = 2204.72 lbs

  16. Force A push or a pull. Tends to produce motion or a change in motion. Units: TONS, POUNDS, ETC.

  17. 5 T 15 T 5 T 5 T Force Parallel forces may be combined into one force equal to the sum of all forces acting in the same direction and so located to produce the same effect.

  18. WEIGHT:Gravitational force. Direction toward center of earth UNITS: LONG TONS, POUNDS, etc MOMENT:The tendency of a force to produce rotation about an axis UNITS: FT-LT, FT-POUNDS, etc d F a MOMENT = F x d F is the force of your hand while d is the length of your “wrench” & Moment is the torque applied.

  19. 2 m 3 m 1 m VOLUME - Number of cubic units in an object UNITS: Cubic Feet, Cubic Inches, Cubic Metres V = L x B x D V = 3 m x 2 m x 1 m V = 6 m3

  20. 2 m 3 m V = 6 m3 1 m SPECIFIC VOLUME - Volume per unit weight UNITS: CUBIC METRES PER TONNE Salt water = 0.9756 m3/tFresh water = 1 m3/t wflooding = Volume Sp. Vol wflooding = 6 m3 0.9756m3/tonne wflooding = 6.15 tonnes

  21. Stability Reference Points

  22. Stability Reference Points M etacenter G ravity B uoyancy K eel CL

  23. Stability Reference Points M other G oose B eats K ids CL

  24. B The Center Of Buoyancy RESERVE BUOYANCY WATERLINE B B1

  25. Reserve Buoyancy, Freeboard, Draft and Depth Of Hull Remember this color!! RESERVE BUOYANCY WATERLINE B

  26. WL WL WL WL WL B B B B Center Of Buoyancy B

  27. B B B B B B B B B RULE OF THUMB = “B” FOLLOWS THE WATERLINE.

  28. G1 G G1 G The Center Of Gravity KG1 KGo KGo KG1

  29. Center Of Gravity • Point at which all weights could be concentrated. • Center of gravity of a system of weights is found by taking moments about an assumed center of gravity, moments are summed and divided by the total weight of the system.

  30. Movements In The Center Of Gravity • G MOVES TOWARDS A WEIGHT ADDITION

  31. Movements In The Center Of Gravity • G MOVES TOWARDS A WEIGHT ADDITION • G MOVES AWAY FROM A WEIGHT REMOVAL

  32. G1 G G G G G G G KG1 KGo

  33. Movements In The Center Of Gravity • G MOVES TOWARDS A WEIGHT ADDITION • G MOVES AWAY FROM A WEIGHT REMOVAL • G MOVES IN THE DIRECTION OF A WEIGHT SHIFT

  34. G1

  35. B B20 B45 METACENTER The Metacenter M B B2 B1 M20 M45 M M70 B70 CL

  36. B B B B B B B Metacenter

  37. B SHIFTS Metacenter M

  38. 0o-7/10o M B CL

  39. M20 M B B20 CL

  40. M20 M45 M B B20 B45 CL

  41. M20 M45 M M70 B B20 B70 CL B45

  42. M20 M45 M70 B CL M M90 B20 B90 B45 B70

  43. Movements Of The Metacenter THE METACENTER WILL CHANGE POSITIONS IN THE VERTICAL PLANE WHEN THE SHIP'S DISPLACEMENT CHANGES OR • WHEN B MOVES UP M MOVES DOWN. • WHEN B MOVES DOWN M MOVES UP. RULE OF THUMB = “M” MOVES OPPOSITE OF “B”

  44. M M M M1 M M M1 M M1 M1 G G G G G G B B B1 B1 B1 B1 B B B B

  45. Linear Measurements In Stability M METACENTRIC HEIGHT GM METACENTRIC RADIUS BM G HEIGHT OF METACENTER KM B HEIGHT OF GRAVITY KG CL K

  46. The Stability Triangle

  47. M G B K The Stability Triangle M G Z CL

  48. M M M M M Z G G G G G B B B B B B1 B1 B1 B1 K K K K K CL CL CL CL CL