## Questions Ship stability

1.

1. What does “stable”mean in general?

2. How can we cause a floating object to loose its state of equilibrium? Give some examples.

3. What will be the effects of becoming unstable on a floating object?

4. Give the definition of stability (for a ship).

5. Name some of the external forces that can be exerted on a ship.

6. An external force is exerted on a stable ship for a short period. How will the ship react?

7. Name the three types of stability?

8. Show each of these types in a drawing.

9. What can be the advantage af a small stability?

10. Name some examples of small stability..

11. Why can a small stability be safer than a (too) large stability, for certain types of vessels?

12. What does “ the lateral shift of buoyancy” mean?

13. What causes the constant change in the distribution of buoyancy on a mooving ship?

14. How can we influence the stability of a vessel?

2.

2.1

1. What do: “ Fpp” and “ App“ mean?

2. Where are they situated?

3. What does: “molded dimensions” mean?

5. where are the:

– llight waterline

– and the construction (scantling) waterline

situated?

6. What information can we derive from the Plimsoll mark?

7. What is the exact distance over which the minimum operating freeboard is measured?

8. Name some deviations from summer conditions.

9. Why is it (in principle) compulsory to state the abbreviations used in the draft marks and the plimsoll mark in the language of the flag state of the vessel?

10. May the vessel be loaded until the lower edge or until the upper edge of the relevant loadline?

11. How can the plimsoll mark be applied permanently on the shell plating?

12. What do the following abbreviations mean: TF, F, T, S, W en WNA?

13. What determines the placement of the draft marks?Waarvan is de plaats van de uitwateringslijnen afhankelijk?

14. Why is it that the geographical position and the season cause deviations from the loadline in summer conditions?

15. What determines the placement of the deckline?

16. Why is the deckline marked right above the Plimsoll mark?

17. Why is a ship that carries a deckload of timber sometimes allowed to load with less freeboard?

18. Explain why a tanker has less freeboard than other cargo ships.

19. Where do we find information that tells us whether we can load for summer, tropical or winter conditions?

20. How is it that we may not be allowed to load until “tropical draught,”even though we are in a port where it is allowed to load for tripical conditions?

21. What argument is used to determine W, S and T?

22. Till which loadline is one allowed to load in a cyclone region?

23. Read the draughts of the vessels on the photographs on pages 14 and 15, as far as they are visible.

24. The draught of a vessel is 31 dm, is the figure just above or just below the water?

2.2

25. What do the following abbreviations mean and what do they stand for?

– LLL

– LOA

– LWL

– TV

– TA

– BSPANT

– BOA

– D

26. What is the difference between freeboard and summer freeboard?

27. From which line is the low profile air draft measured?

28. How can the low profile air draft be diminished? Please explain.

29. Where does the ship get extra buoyancy through the sheer? Please explain.

30. What is the advantage of “camber”?

31. Where do we find the baseline?

32. On which intersection do we find the keel (K)?

33. Show the following terms in a drawing:

– Rise of floor.

2.3

34. How is the trim determined?

35. What is the term for zero trim?

2.4

36. – What is the advantage of a large L/B ratio?

– What is the advantage of a small L/B ratio?

37. Where does the L/D ratio play a part?

38. Explain why the deck will be submerged sooner with a large B/D ratio

2.5

39. Why is the size of different ship types expressed in different units?

40. What does RT mean and what is the corresponding value?

41. What does GT mean?

42. Which arguments are used to determine GT?

43. Why is GT dimensionless and what does that mean?

44. – What options do ship builders have to ensure as small a GT as possible?

– What dangers can occur because of this?

45. What does NT mean?

46. Which space is resented very well by NT?

47. What is the relation between GT and NT?

48. – Which value is represented by the carene?

– In what unit do we express the carene?

49. What is the difference between carene and displacement?

50. What are the two possible ways of expressing displacement?

51. How do you calculate the water displacement if the volumetric displacement is known?

52. What is the definition of ”lightship weight”?

53. What does the “ regular inventory” include?

55. Why is the deadweight a fixed value?

57. The cargo capacity is the weight in tons a ship can load. Why does that amount constantly change?

58. How do you calculate the cargo capacity?

2.6

59. Which part of the underwater body of the vessel is represented by the form coefficient?

60. In short, what is the “reserve buoyancy”?

61. Why doesn’t the form coefficient have dimensions?

62. Fir the following coefficients state:

– What it means

– The formula

– Which information can be derived from:

1. waterline coefficient

2. midship section coefficient

3. block coefficient

4. prismatic coefficient.

63. What is meant by “geometrical shape” of the ship?

64. What is the purpose of the lines plan?

65. In the lines plan; what are the waterlines?

66. What is the design waterline?

67. In the lines plan; what are the ordinates?

68. What is the usual number of ordinates, and from where to where do they run?

69. In the lines plan; what are the verticals?

70. What is the longitudinal plan?

71. In the lines plan; what are the diagonals?

72. What are the diagonals used for?

2.7

73. Name the parts numbered in chapter 2.7

2.8

74. What comprises the ship’s weight?

75. Give the meaning and a short explanation for the following abbreviations:

– COG

– COg

– COB

– M

– K

– COF

76. Explain the meaning of “G” in two ways.

77. Is “G” normally a fixed or a moving point on a moving vessel? Please explain your answer.

78. Explain the meaning of “B” in two ways.

79. Explain why “B” is not a fixed point on a moving vessel.

80. What is meant by “an area, or plane of reference”?

81. Give the meaning and a short explanation for the following abbreviations:

– VCB

– LCB

– TCB

82. What is a “resultant”?

83. What causes weight?

84. What is “mass”?

85. Which lines coincide when “G” is directly under “B”?

86. Name 2 situations where G and B are not in the same vertical plane.

87. When does the upward pressure diminish?

88. Why, during bad weather (moving vessel),

– does the total upward pressure remain unchanged

– does the distribution of the upward pressure around the underwater body of the ship change?

89. What does “LCF” mean?

90. Which point of gravity does COF denote?

91. Which axes run through COF?

92. Which important particular can be derived from COF?

93. How can we define “M” when the angle of heel is

– less than 5°

– bigger than 5°?

94. When does “M” coincide with the area of keel and stem?

95. Why do we use “N” instead of “M” for calculation purposes?

96. Where is “N” situated at any given angle of heel?

97. What determines the distance between “B” and “M”?

98. What is approximately the distance between “B” and “M” on most ships (no list)?

99. Why is “M” transverse situated at a different location from “M” longitudinal?

100. Which points are essential for the transverse stability?

101. When do we speak of negative stability?

102. Why is “BM” longitudinal usually much bigger than “BM” transverse?

103. What causes “BM” transverse to change much more during rolling and pitching than “BM” longitudinal?

2.9

104. Name at least 5 factors that influence the amount of cargo a ship can take on any given trip.

105. State a cargo for which the only point of consideration is the weight of the cargo to be loaded. Please explain this.

106. State a cargo for which the only point of consideration is the volume of the cargo to be loaded. Please explain this.

107. What is the density (ρ) of a substance and what is the ratio in which it is expressed?

108. What is the stowage factor (sf) of a cargo and what is the ratio in which it is expressed?

109. What is the relationship between ρ and sf? Give the formula and explain in words.

Vragen Stabiliteit UK 3-4.htm

3.

3.1

1. Only the shipbuilder can influence the positions of M and B. Why?

2. In which way can the crew influence the position of G?

3. Which two stadia of transverse stability are there?

4. What determines the distance KM?

5. What determines the distance KG?

3.2

6. What are the three main factors for (form) stability?

7. Why does the stability decrease when the bilge rises out of the water?

8. When the deck is flooded, what happens to the stability? Please explain

9. Make a drawing explaining form stability and indicate the stability moment.

10. What is the difference between form stability and stability of weight?

11. Make a drawing explaining weight stability and indicate the stability moment.

3.3

12. Which resultant is situated in punt B?

13. What happens when weight and buoyancy are unequal? Please explain.

14. Why does the point of buoyancy change continuously when the ship sails in waves? Please explain.

15. When are the resultant forces aligned?

16. Why are resultant G and resultant G almost always equal?

17. In which direction will B move with a rolling ship?

18. Why will B usually return to the vertical plane of symmetry after the ship has turned fully over?

19. On a rectangular vessel, where is B situated? (Draft wise.)

3.4

20. What determines the position of M?

21. Where is G situated with respect to M in the following states of stability?

– Positive

– Neutral

– Unstable

22. Name 2 factors that determine the position of M?

23. Make two drawings that show that the width of the water plane area is of much more influence on the stability than the length of the water plane area.

24. When will the width of the water plane area decrease with increasing list?

25. Define:

– N

– M.

26. Why Is M usually replaced by N when the list is > 50?

3.5

27. Which information can we derive from the lines plan?

28. How many water lines and how many ordinates are there in the lines plan

29. How do the Bonjean-curves come into being?

30. What can be read from the Bonjean curve?

31. Why is the computer calculation of the volume of the underwater body much more accurate than a calculation following Simpson’s rules?

3.6

32. Which weight is concentrated in G?

33. Why is the crew able to influence the position of G?

34. What is a vector?

35. What is a resultant?

36. What is the difference between “g” en “G”?

37. What does “light ship” mean?

38. What is the compulsory equipment?

39. – In which 2 ways can the ship builder manipulate the position of G?

40. Which data are needed to determine VCG?

41. What is a Moment?

42. Indicate how VCG can be determined using the Law of Moment Equilibrium?

43. Is it impediment that the point (or Plane) of reference remains in the same place when the Law of Moment Equilibrium is applied. Please explain.

44. What is the difference between the sum of the moments on starboard side and the sum of the moments on portside if the ship has no list? Please explain.

45. In a ship we come into contact with three different moments.

– state the directions

– state and define the abbreviations used

– state the planes of reference and name the distances with respect to these planes

46. How does VCG develop when

– weight below G is discharged

– weight above G is discharged.

– weight below G is loaded

– weight above is G is loaded

47. Where should weight be placed in order to:

– decrease VCG (2 possibilities)

– increase VCG (2 possibilities).

48. When is Movement of center of gravity usually applied?

49. State Movement of center of gravity for

– shifting weight

– discharging weight

– explain the abbreviations used.

50. Why is the Inclining test compulsory?

51. What are the conditions for the Inclining test?

52. Which are the 2 demands on the weight used?

53. In short, describe the stability test.

54. Prove the formula, G0M = pxa/Δ x tanφ, in a drawing.

55. How can KG0 be calculated after GM0 has been established through the stability test?

56. What is determined with the stability test?

57. State the formula to calculate GM0 using the Inclining test

58. How do we determine the oscillation period?

59. Describe an easy way to perform an inclining test.

60. May GM0 as obtained with the oscillation test be considered permanent?

61. What is the relationship between oscillation period and GM0?

62. What are the characteristics of a stiff ship?

63. Is KG too large or too small with a stiff ship? Please explain.

64. Name some problems / dangers that can occur when the ship is (too) stiff.

65. What can the ship builder do to prevent a ship to become too stiff or too tender

66. What can the crew do in that respect?

67. When is a ship considered to be tender?

68. What happens to the oscillation period when the ship becomes tender

69. Give an example of a ship that becomes tender.

70. Why is a tender ship more comfortable for the crew than a stiff ship

71. Why will the cargo be less inclined to shift on a tender ship than on a stiff ship?

72. What can the crew do to prevent a tender ship?

3.7

73. In which can BM0 be determined?

74. What is the lateral moment of inertia (IT) door for a rectangular pontoon?

75. Which argument plays the biggest role in IT?

3.8

76. What are the components of the stability moment?

77. How big is the righting arm?

79. Draw a cross section of a ship with list, as a result of e.g. a wave, showing the stability moment. Use this to prove the formula: moment = Δ x (KNsinφ – KGsinφ).

80. Which factor in the above mentioned formula that the crew can influence?

81. For the following conditions, make one drawing each showing the moment for a ship with list due to e.g.a wave:

– positive

– neutral

– unstable

82. Indicate the turning circle of the moment in each of the drawings.

83. Show the effects of the horizontal movement of a weight in three steps.

84. When will a ship capsize due to such a horizontal shift of weight? Please explain.

85. What causes a ship, with no list and a negative stability to get a list instead of capsizing?

86. How can G be brought down at sea?

87. Whet the stability is too small, which double bottom tank should be filled first, the ones on the low side or the ones on the high side? Please explain.

3.9

88. What can we read from the curve of static stability, for every heeling angle

89. Why does this curve usually not exceed angles > 60°?

90. When is the stability curve applicable?

91. Name at least four situations for which the stability curve must be appraised., to see whether it complies with the rules.

92. What determines the area below the curve?

93. Why is the curve only applicable in calm water?

94. For ever angle of heel, which information can we derive from the curve.

95. When will the area below the curve decrease?

96. What is the meaning of a change in the direction of the curve?

98. Give an example of static and of dynamic, and explain these terms.

99. Indicate, in the curve, the point of capsizing due to a static load and due to a dynamic load.

100. What effect can list have on the draft and on the trim? Please explain.

101. Use a drawing to prove that GZ can be determined with KNsinφ – KGsinφ.

102. Explain how the curve can be constructed after determining GZ

103. How is the first part of the curve accurately drawn?

104. What is the dynamic stability?

105. What is the dimension of the dynamic stability?

106. Name some vessels with different criteria for stability.

107. What does: “ angle of flooding” mean?

108. What is meant by Dynamic Stability?

109. Why is there a minimum value for the Dynamic stability?

110. What is the minimum value for:

– angle of heel up to 30°

– angle of heel between 30° and 40°

111. What is the minimum righting arm for an angle of heel ≥ 30°?

112. At which angle of heel should the maximum GZ preferably be reached?

113. What is the minimum initial metacentric height?

114. How can the area below the curve be calculated when the horizontal axis depicts the angle of heel and the vertical axis depicts righting arm in cm? Please explain.

116. Give three ways to calculate the area below the curve.

117. Draw stability curves for the following situations:

– GM is 0

– GM is negative

– The ship has a list.

118. Wat rae the effects on the stability of a ship when

– its width is increased? Please explain.

– its depth is increased? Please explain

119. State some advantages of a higher freeboard.

120. State some advantages of a wider ship.

121. Draw a cross section of a ship with a constant list, with the moments due to a steady wind force.

122. Draw a curve and indicate:

– Wind moment lever

– Heeling angle φS

– The reduced righting arm.

123. What is the center of lateral resistance?

124. What is the rolling amplitude?

125. What determines the rolling amplitude?

126. Why is it not always possible for a ship to absorb a strong wind gust? Explain this with a curve.

127. With regards to the static equilibrium, show the differences between the wind levers and the righting arm prior to a list φS and after a list φS.

128. Suppose the wind lever is 13 cm. What is the effect for all righting arms?

129. Draw a stability curve and a curve for a wind gust, indicate the resulting righting arm.

130. What is the minimum value for the resulting righting arm to prevent the ship from capsizing due to a wind gust?

131. The wind arm is considered constant during the whole rolling period, but what is the actual development of the lever when the list increases? Please explain

132. What does “an excess of energy is exerted on the ship” mean?

133. When do we speak of a dynamic equilibrium after the ship has experienced a wind gust?

3.10

134. Give some examples of listing moments:

– from inside the ship

– from outside the ship.

135. Give some examples of forces that cause a

– static moment

– dynamical moment

– a static as well as a dynamical moment.

136. draw a cross section of a vessel and indicate M0, G0, B0 and K. Now draw the same ship with a list due to lateral shifting of weight and indicate:

– the movements of B en G.

– the decrease of the righting arm

– the righting moment after the weight has been moved.

Show the decrease of the righting arm in the curve.

137. Liquid that can freely move can be extremely hazardous on a ship. Name some factors that can increase the danger.

138. The effect of the freely moving liquid is usually static. When does a dynamic effect occur?

139. What do the abbreviations VVC, FSC and FSM mean?

140. draw 4 cross sections of ships with a double bottom tank and a list due to e.g. waves.

– draw the stability moment in case the double bottom tank is empty in drawing 1

– draw the stability moment in case the double bottom tank is full in drawing 2

– draw the stability moment in case the double bottom tank is half full in drawing 3

– draw the stability moment in case the double bottom tank is half full, but when a longitudinal bulkhead has been placed in the double bottom tank, in drawing 4

– indicate FSC in drawings 3 and 4.

141. Why is the reduction of GM (with a FSC) considered to be virtual?

142. Explain why after placing 2 longitudinal bulkheads in the double bottom tank FSC is only 1/3 of the original value.

143. Explain why the danger of capsizing due to free moving liquids is bigger on Ro-Ro vessels than on other vessels.

144. Why is it necessary to restrict list as a result of loading a heavy lift, to 2°?

145. Which measures can be taken before starting to load a heavy lift to restrict the list to 2°?

146. From which moment will the weight of the heavy lift appear to be concentrated at the top of the crane?

147. In which direction and over which distance will G move as soon as the weight is airborne?

148. Which is the desired effect of a pontoon alongside the vessel during loading or discharging?

149. State the formula to calculate the list that can occur during loading and discharging. Explain the abbreviations used.

150. What is the effect on the stability when the stability pontoon gets under water?

151. How can the list be kept to a minimum when a heavy lift is loaded

152. Use sand to illustrate the three possible stadia of bulk cargo

153. What is meant by “grain”?

154. What is the effect of settling on “g” of the grain?

155. What is the advantage for the ship if it meets the regulations for a grain cargo?

156. What problem can occur if the stowage factor is smaller than pre arranged? Please explain.

157. If grain shifts in a certain compartment, G will move over a distance of G0G1 = pxa/Δ. Rewrite the formula to contain all factor pertaining to a grain cargo show. Explain the abbreviations used.

158. Why must factor K be used?

159. Draw two cross sections to show the movement of G after the grain has shifted

160. To obtain the righting arm G1Z1, what should be deducted from the original righting arm?

161. Why do we use the “maximum allowable grain heeling moment” table and which factors have to be known to be able to use this table?

162. How is the heeling moment (mt) of the cargo calculated when the volumetric heeling moment is given?

163. Draw a stability curve indicating:

– the grain curve

– GM –> > 30 cm

– resulting dynamic moment.

164. Why is shifting ore much more dangerous than shifting grain?

165. Wind can cause list. What determines the effect?

166. Why do IMO regulations consider wind pressure from abeam?

167. The profile area above the water line difference. Name some factors that cause

169. Why is a wind gust considered a dynamic force?

170. What is meant by the rolling amplitude of a ship?

171. What does the rolling amplitude depend on?

172. What do the abbreviations φA and φS mean?

173. What is the rolling period?

174. Suppose φS is 3° over starboard and φA is 7°. How many degrees does the ship roll to starboard, and how many degrees does the ship roll to port?

175. draw a stability curve and indicate the curve of the static arms due to a steady wind force

– determine φS

– draw the curve after a wind gust

– Color the area that shows the energy that gives the ship a list.

– Indicate K.

– color the area that shows the resulting arms.

– Indicate the areas that have to be equal to determine φc.

– determine φc.

176. When the ship rolls from one side to the other, a counter pressure will be experienced after 0° equal to the excess water pressure.

– what does this mean?

– Indicate this water pressure in the curve of question 175.

177. The area under the curve that indicates the energy that causes the ship to roll should equal the area that indicates the resulting arms. What happens when the area under the curve is not big enough for that? Please explain.

178. Suppose: the deck is immersed at 40°. What will be the consequences for the curve in question 175?

179. Why does counter ballasting enable us to forego calculating small lists that are expected to occur?

180. If the expected list exceeds 10 to 15°, this can easily be determined beforehand with a stability curve. Explain this procedure.

181. How can the list, due to shifting grain, be read from the curve

182. Why do we have to multiply the grain lever with 0,8 at 40°?

183. What can be deduced from all the following curves:

– stability curve with the curve for grain levers

– stability curve with the wind curve?

Name at least two things.

3.11

184. What determines the magnitude van KNsinφ and KM?

185. How is KG max determined for any given draft?

186. Name 2 reasons why KG max.– in general – has to be smaller with a shallow draft than with a deeper draft.

187. Name some standard stability criteria as stated in rule A749 of the IMO.

188. What problem occurs when the stability is checked with KG max?

189. Give a simple way to determine the area under the curve.

190. State Simpson’s 1st rule and explain the abbreviations used.

191. How is Simpson’s rule applied?

4.

4.1

1. Why is Mlongituninal situated much higher than Mtransverse?

2. Why is the longitudinal stability less important to consider than the transverse stability for the safety of the vessel?

3. Why is Mlongituninal practically a fixed point with regards to the trim?

4. When the shape of the waterline differs greatly in the stem and the stern, this affects the position of Mtransverse. Explain this.

4.2

5. COF:

– What does the abbreviation mean?

– Define COF.

6. – Where is COF situated in a rectangular barge?

– If we trim this barge 1 meter, what is the change in draft forward and aft?

7. Suppose: the COF on a ship is situated well before ½LLL. Where will the change in draft be greatest when we trim the sip, forward or aft? Explain your answer.

9. State the influences, during loading, of a wide stern on the trim.

4.3

10. ETM:

– What does the abbreviation mean?

– Define ETM.

– In what unit is ETM expressed?

11. which two factors determine the longitudinal moment?

12. explain why draft and trim determine ETM.

13. State the formula for trim, and explain the abbreviations.

14. The distance, mentioned in the formula can be determined for three different states of the vessel. Name these states.

15. When is the change in trim also the ultimate trim?

16. How is the ultimate trim ascertained?

17. State the formula for a certain trim, when the position of the load weight is known.

18. State the formula for a certain trim, when weight of the load is known, but the position of the load weight is not.

19. What is the plane of reference for the distance in question 18?

20. How do you ascertain whether the trim is forward or aft?

21. What is the difference between COF and LCF, and what is the similarity between these two?

4.4

22. what do LCB and LCG mean?

23. How can the trim formula (Δ trim = pxa/ETM) be changed for use during loading, discharging and shifting cargo?

24. Where is B (longitudinal) situated with respect to G (longitudinal) in the following situations:

– On even keel?

– Trim aft?

– Trim forward?

For each situation, draw the moment.

25. State the formula to calculate trim when several weights are discharged, loaded or moved.

4.5

26. Suppose: Trim is 10cm. When will the trim be evenly distributed between fore and aft? Please explain.

27. If COF is aft midships, where will the trim have a bigger effect, forward or aft?

28. State the formula to calculate the change in draft aft.

29. When the change in draft aft is known, haw can we calculate the change in draft forward?

30. How is the Total trim calculated when draft forward and draft aft are known?

31. Which trim is positive, and which is negative?

Vragen Stabiliteit UK 5-9.htm

5

5.1

1. Which points are important to determine whether a ship can survive a certain amount of damage?

5.2

2. What is the importance of balancing cost and safety?

3. What organisation occupies itself with the criteria?

4. – What is meant by symmetric flooding?

– The chance of symmetric flooding will increase with the amount of longitudinal bulkheads. Explain this.

5. What is meant by the “margin line”?

6. What does the “bulkhead curve” tell us?

7. What is the difference between a 1 compartment ship and a 2 compartment ship?

8. Explain the difference between the deterministic and the probabilistic damage stability.

10. What is IMO resolution A.265 about?

5.3

11. How do you calculate the end situation when for instance 1 double bottom tank has been damaged?

12. Explain how the end state of a ship can be determined with the “constant displacement” method?

13. how the end state of a ship can be determined with the “loaded weight” method?

14. Give two examples of dangerous situations that can arise from damage to a chemical tanker?

15. Which two possibilities do you have to calculate the end state after incurring damage, for every state of loading?

16. What does ERS mean and what are the possibilities of this provision?

6

6.1

1. Name the 6 independent movements of a ship in swell.

2. – Which movements are periodic, and which are not?

– What is the difference between the two?

3. What causes the continuous change in waterline?

5. Why does GM constantly vary in swell?

6. Explain that (specifically with relatively short vessels) the stability of a ship sailing in stern quartering waves can decrease to the point of capsizing.

7. Sailing in a trough of a wave the stability of the vessel can increase. Explain this.

8. Draw a periodical and an a-periodical movement.

6.2

9. Define the dynamic stability in words.

10. Name some external dynamic forces that can apply to a vessel.

6.3

11. What are the characteristics of the wave pattern around a ship to cause a decrease in stability?

12. Explain why a negative GZ can cause the vessel to capsize.

6.4

13. When is the ship in danger of collapsing due to dynamic rolling?

14. What wave pattern around the vessel can cause parametric rolling?

15. What kind of vessels is particularly prone to parametric rolling, and what type of shape do the hulls of these vessels usually have?

15 a Why does this shape in particular cause parametric rolling?

16 When does resonant rolling occur and which factors have an influence on resonant rolling?

17. What is the danger of quartering, breaking waves?

6.5

18. What danger can occur through stern quartering waves?

19. What danger can occur through stern quartering waves with lower speed than the speed of the vessel?

20. What problem can occur with a single wave? (Chapter 6.5.3)

21. How does surf riding come about?

22. What can increase the danger of surf riding?

23. What can cause a longitudinal directional instability during surf riding?

– How can this cause the ship to broach into a beam sea condition?

24. When does surf riding on the front slope of a long steep wave occur?

– What can this cause?

25. Which circumstances cause pitching, rolling and yawing at high speed to be extra dangerous?

– What is the danger when a critical wave overtakes the vessel in combination with a downwards movement followed by a significant roll?

7

7.1

1. What are the consequences of the continually changing draft during docking?

2. The force of the vessel on the dock blocks increases during the docking process. What is the increase equal to? Explain your answer

3. When does this force reach its maximum?

4. Why does KG change in the process of docking and KB stay the same?

5. Why should a ship be adequately supported by struts or bilge blocks long before it stands clear of the water? Explain your answer.

6. How is the water depth in the dock determined if we assume that the force “P” is considered to be discharged weight? Explain your answer.

7. What is the advantage of a floating dock compared to a graven dock when docking a vessel with trim or list?

8. What is the “slope” of a dry-dock?

9. What can be the result of a difference in slope of the dock and trim of the ship?

7.2

1. Why is the displacement of a grounded ship smaller than the original displacement?

2. Why will KM and KnsinQ decrease?

3. What can the result of deminished KM and KnsinQ be?

4. How do we determine the position of the grounding?

5. In which cases will it be necessary to deballast or unload after grounding?

6. What danger can occur as a result of deballasting a grounded ship?

7. When do you call for help of salvagers?

8

8.1

1. Why is the stability of sailing vessels slightly different from the stability of other vessels?

2. What are the two deciding factors for the magnitude of the capsizing arm?

3. Explain the following terms:

– Center of effort

– Center of lateral resistance

– Lateral resistance

– Setting to leeward

– Frictional Resistance

4. What does “luff up” mean?

5. Why will a sailing vessel have a tendency to luff up when it is subject to a heeling angle?

6. What is a dynamic force due to a wind gust as experienced by a sailing vessel?

7. Why does the wind moment decrease with increasing heeling angle?

8. Explain with a drawing why the stability of a Dutch round bottom mainly depends on the form of the vessel.

9. Now do the same for a centerboard yacht. Idem

10. Why is ballast a necessity for a sailing cargo vessel without cargo?

11. Explain with a drawing why the form stability is of less importance than the weight stability for anS-frame.

8.2

1. Use some drawings to illustrate that the form stability determines the stability of a catamaran with diverse heeling angles

2. Name 2 causes for reduced wind pressure with steady wind force.

3. Name 3 to influence stability through shifting of weight on a sailing vessel.

4. What causes stiffness in Catamarans during bad weather?

5. Whet will the stability curve for a catamaran reach its highest point? Explain your answer.

6. Name an advantage of a Swath.

7. What are the changes for the stability curve when a float of a swath is immersed in the water? Please explain.

8. What are the changes for the stability curve when a float of a swath comes out of the water? Please explain.

8.3

1. Crane ships possess a large waterplane area. Explain the effects this has on the behavior of crane vessels in swell, and on the stability of these vessels.

8.4

1. Certain types of fishing vessels have a small freeboard. What can be the consequences for the stability? Explain your answer.

2. Form stability of sterntrailers increases due to the wide stern of the vessel. Please explain.

8.5

1. What can cause a negative effect on the stability of a supply vessel?

8.6

1. What are the effects of the fact that the cargo of a dredger is heavier than water?

2. Why should a hopper dredger have a large waterplane area?

8.7

1. What danger is countered if a submersible pontoon is trimmed when it is brought up?

8.8

1. Why doesn’t a submarine have form stability?

2. Use a drawing to explain that a submarine only has weight stability.

9

1. Which 2 types of stability programs are there?

2. What are the calculations of both programs based on?

3. What is the difference between deterministic and probabilistic damage stability calculations?

4. What are the different in approval policies that the classification societies use for loading software?