Revision Questions

Question 3

Draw the following
a. length between perpendiculars;
b. length overall;
c. fore perpendicular;
d. aft perpendicular;
e. freeboard;
f. aft sheer;
g. sheer forward;
h. camber;
i. beam;
j. draft;

Answer 3

draw them

Question 4

Describe EACH of the following types of motion:
a. roll;
b. pitch;
c. yaw;
d. surge;
e. heave

Answer 4

a) a rocking motion resulting in the ship tilting from port to stbd
b) a longitudinal rocking motion with the bow & stern rising and falling
c) the turning of the vessel’s bow to port or starboard around its vertical axis
d) the forward or backward motion of a ship or boat along its longitudinal axis
e) heave describes the up-and-down motion of a ship or boat along its vertical axis due to wave action

Question 5

Sketch and explain set of freeboard markings for a vessel of length greater than 100m

Answer 5

Draw them

Question 6

With respect to the LOAD Line rules, define EACH of the following terms:
a. Freeboard;
b. Freeboard Deck;
c. Superstructure

Answer 6

a) Freeboard is the distance measured vertically downwards amidships from the upper edge of the freeboard deck to the upper edge of the loadlines
b) The deck of a ship from which the freeboard is measured.
c) any enclosed structure on the deck of a vessel that extends above the main deck.

Question 7

b. Give reasons why the fitting of freeing ports assist in maintaining the stability of a ship

Answer 7

As allows water on the main deck to drain off back to the sea, without them the water could accrue over time leaving to an increased ship net displacement potentially affecting stability. the water trapped on the net could would could also have free surface effect which again could compromise the ships stability.

Question 8

State the four intentions of the loadline regulations

Answer 8

adequate strength for the proposed loading

• adequate reserve buoyancy in all probable conditions of loading
• sufficient stability in all probable conditions of loading
• adequate protection for the crew when on deck in bad weather

Question 9

Describe, with the aid of a sketch, EACH of the following:
i) racking;
ii) pounding;
iii) panting.

Answer 9

i)When a vessel is rolling in a seaway the transverse section will try to distort at the corners due to racking stresses.
ii) When the ships bow leaves and re-enters the water due to heaving/pitching
iii) a stress that occurs on the ends of a vessel due to changes in water pressure acting upon the ships hull from pitching/heaving

Question 10

b. Explain the measures taken to combat each of the following stresses:
i) racking;
ii) pounding;
iii) panting.

Answer 10

i) transverse bulkheads and diagonal bracing to reinforce the corners of the ships structure and help distribute the stress evenly along the frames
ii) strengthened bow structure as this is the area that is primarily affected by pounding & a bulbous bow to improve hydrodynamics and reduce the impact forces during pounding.
iii) panting beams & stringers to reinforce and distribute the fluctuating pressures acting upon the vessel.

Question 11

a. Explain, with the aid of sketches, the terms hogging and sagging, with reference to vessels meeting waves having the same length as the vessel.

Answer 11

hogging, when the ships bends vertically upwards in the middle, this can be due to excessive loads at the fwd/aft ends of the vessel or excessive buoyancy acting upon the middle of the vessel. This can also occur when a vessel rides a wave crest in its middle, causing excessive buoyancy.

sagging, the opposite of hogging the ship bends vertically downwards in the middle, this can be due to excessive loading in the midships or in terms of waves the ship rides 2 waves crests at both the fwd & aft ends causing a lack of buoyancy in the ship’s middle causing the sag.

Question 12

State the parts of a ship’s structure that resist the following stresses hogging and sagging

Answer 12

keel
deck plating
Bottom Shell Plating
Deck Stringers
Internal Longitudinal Girders

Question 13

With the aid of a sketch, explain the meaning of EACH of the following terms:
a. beam;
b. frame;
c. girder;
d. beam knee;
e. duct keel.

Answer 13

a) the horizontal structural elements that extend across the width of the ship
b) the skeleton of the hull. They provide a structural skeleton (rib-like)
c) girders are longitudinal structural components that run along the length of the ship
d) L-shaped piece installed where the ship’s deck beams meet the hull.
e) Duct keel is provided in double bottom hull ships and consists of solid plates welded into a box shape, forming an internal watertight passage running along the length of the ship

Question 14

State the purpose of the collision bulkhead and the regulations appertaining to its dimensions and position.

Answer 14

limiting the damage of a head-on collision to the part of the bow forward to it.

The collision bulkhead must be watertight upto the bulkhead deck. * There must be no doors, manholes, access hatches, ventilation ducts or any openings
on the collision bulkhead below the bulkhead deck.

Question 15

Explain the difference between A, B and C class bulkheads.

Answer 15

A, B, and C class bulkheads differ in their level of fire resistance, structural robustness, and effectiveness in containing and preventing the spread of fire within a ship. A-class bulkheads offer the highest level of protection, followed by B-class and then C-class bulkheads.

Question 16

Sketch and describe EACH of the following ship construction features
i. Plate floor.
ii. Watertight bulkhead.

Answer 16

i) plate floors are horizontal plates that are attached to the ship’s longitudinal frames such as the bottom shell plating.
ii) A vertical partition that divides the hull into
separate compartments, running either
transversely or longitudinally

Question 17

With reference to a vessel’s hull:
a. State the meaning of the term racking;
b. Explain how racking occurs;
c. State the structures that resist racking.

Answer 17

A) The ships transverse structure will be subject to distortion as the pressures try to bend the structures at the corners.
B) Excessive rolling from waves causes excessive racking especially when the vessel is lightly loaded or in ballast condition
C) Beam Knees and corners brackets help strengthen the structures and the transverse bulkheads take majority of the stress caused by racking

Question 18

With reference to forward collision bulkheads:
a) Describe their construction;
b) State their function;

Answer 18

a) it is a watertight bulkhead that is heavily strengthened and positioned just behind the bow. it is strengthened by panting stringers and vertical stiffeners. it must be watertight upto the bulkhead deck, There must be no doors, manholes, access hatches, ventilation ducts or any openings
on the collision bulkhead below the bulkhead deck.
b) its main purpose being
limiting the damage of a head-on collision to the part of the bow forward to it.
c) the forward-most bulkhead in a ship, its positioning is based off three factors, Position based on floodable length calculations, Position based on the classification society code books, Position based on SOLAS rule, which states that the collision bulkhead
should be located aft of the forward perpendicular at a distance not less than 5
percent of the ship’s length of the ship or 10 meters.