Ship Construction Flashcards
Define: freeboard deck
The upper most deck exposed to the weather and sea which has permanent means of closing all openings and below which all openings in the side of the ship are fitted with permanent means of closure
There’s a direct link between a vessel’s freeboard and : Safety with regard to personnel Stability Strength hull structure Prevention of ingress of water
Assigned freeboard
The distance measured vertically downwards at amidships from the upper edge of the freeboard deck to the upper edge of the summer load line
Weathertight
In any sea condition water will not penetrate the ship
Define Panting
Panting is the in and out movement of the shell material due varying pressure changes
Briefly explain how the locality is stiffened to resist this stress (Panting)
Reduce the unsupported opener area by close frame spacing and/or additional stiffening members (eg panting beams) and/or increase shell thickness
Wood - advantages
Floats, strength, appearance, easy to work with
Wood - disadvantages
Rots, can burn expensive poor radar reflector Marine borers
Steel - advantages
Relatively strong, widely available, easy to work with, cheap to produce and recyclable, good radar reflector.
Steel - disadvantages
Corrosion, relatively heavy 3x heavier than aluminum, conducts heat, needs regular maintenance
Aluminum- advantages
High strength to weight ratio, doesn’t corrode as easy as steel, good radar reflector, recyclable
GRP/FRP - advantages
High strength to weight ratio,
non corrosive
low cost if moulds are used
Readily available
GRP - disadvantages
Blistering and delamination, once of fire - burns intensely giving off toxic gas, poor radar reflector Poor in bending Specialist Labour
Explain How chemical corrosion in steel occurs
Caused when the oxygen in the atmosphere combines with the metal and forms iron oxide. The oxide film is not firmly attached to the parent plate and thus permits further oxidation to occur
Discuss the factors and conditions that would cause chemical corrosion to be accelerated and how good ship design could reduce this
Accelerated by and prevention :
Good ventilation
Reduce heat
Avoid water traps
Accessibility for preservation :
Regular inspection and maintenance
Center grider - importance/function
Furthest from the neutral axis
Contributes substantially to the Longitudinal strength to resist sagging and hogging
Receives load when in dry dock
Plate floor - importance/function
Vertical plates running transversely across the bottom to stiffen the bottom
Transfer loads from the tank top and gives support to the side and center griders
Shell material - importance/function
Watertight skin of the ship. Major part of the ships strength.
Efficiently unites the supporting longitudinal and transverse members the make up the framing system.
Upper deck -
importance/function
Furthest from neutral axis;
Top flange of the grider
Strength deck
Deck beam - importance/function
Part of deck framework (with griders)
Supports deck plating
Transfer loading to frames bulkheads and pillars
Beam knee - importance/function
Unites the beam and frame enabling stresses to be transferred from one to the other
They offer some resistance to racking
Transverse frame - importance/function
Part of the framing system
Receives the deck loading via the beams and transfer the load to the bottom structure
Transverse bulkhead - importance/function
Subdivides the yacht into separate compartments
Contain flooding and fire
They contribute greatly to the structural integrity of the ship by providing the primary resistance to transverse deformation and so resist racking
They also are efficient load bearers and effectively distribute loads to the adjacent structure
Pillar - importance/function
Supports deck and transfers loading downwards, the unsupported span of the beam is reduced and hence beam sections can be reduced in depth so the clear space
Where extra deck loading is need ie: helicopter
Give four items of information to be found on a general arrangement drawing
plan, profile and section views
Division into compartments (tanks, engine room, holds)
Location of bulkheads
Location and arrangement of superstructure
Parts of the equipment (winches, loading gear, bow thruster, life boats) Dimensions (Length, Breadth, Draft) Volumes of the holds (Cargo Capacity Grain & Bale) Tonnage Deadweight Engine power Speed (Service Speed) Class
Sketch and explain the term “pounding”
Is the vertical slamming of the forefoot of the vessel onto the trough of a wave being caused by a combination of pitching and heaving.
Produces large impulsive forces on bottom plating
Explain how the locality is stiffened to resist this stress (pounding)
Frame spacing reduced
Additional stiffeners introduced
Shell plating thickness increased
State two reasons/functions for fitting each of the following :
Transverse bulkheads
Subdivides yacht into separate compartments
Contains flooding and fire
Contribute to resisting of racking
Contribute to load bearing
Effectively distributes loads to adjacent structures