GSK - Ship´'s Construction Flashcards
Freeboard
Vertical distance at amidships between the uppermost continues watertight deck (Freeboard Deck) and the waterline
Assigned Freeboard
Vertical distance at amidships between uppermost continues watertight deck (Freeboard Deck) and the Summer Load line (SLL)
Freeboard Deck
Uppermost continues watertight deck having permanent means for closing all openings to maintain watertight integrity. Below which all openings in the vessel’s side have permanent means for watertight closure
Deck Girder
Supports the deck & secures the deck beams adding Longitudinal Strength to resist Hogging and Sagging
Pillar
Supports the deck beans transferring weight to the plate floor
Beam Knee
Supports the join between the deck beam and the transverse Frame;
resists Racking and helps to transfer the load from the deck into the frames
Deck Beam
Supports the deck and transfers the load from the deck into the transverse frames. Adds Transverse Strength to resit Racking
Transverse Frame
Ribs of the Ship giving support to the plating, deck and the deck beams as well as transferring the load to the bottom
Plate Floor
Vertical plates running across the ship transferring weight from the deck & Pillars to the Keel giving Transverse Strength.
It stiffens the bottoms plating and transfers weight of the ship to the surrounding water. Some have lightening holes to reduce the weight
Galvanic Corrosion
The Galvanic corrosion is a form of electrolysis whereby two different metals will react with one another to from an electric cell when they are placed in a suitable medium (an electrolyte).
In this case the less Nobel metal is aluminum which will give up its iron and become eaten away (it corrodes). The aluminum is known as the Anode while steel becomes the Cathode, The process is speed up due to the efficient salt water electrolyte.
- When on a hull with Propeller, use zink least nobel metal in galvancic scale as anode !!!
Sacrificial Anodes
ICCP Impressed current cathodic Protection
How does Chemical corrosion occur in steel?
What factors cause it to be accelerated and how Good ship design could reduce it?
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.
Accelerated by:
water and heat
Prevented by:
good ventilation, reduce heat, avoid water traps, regular inspection and maintenance
What is Pounding ?
How can locality be stiffened to resist stress
Pounding is the vertical slamming of the Forefoot of the front of the Ship onto the trough of a wave being caused by a combination of pitching and heaving.
This Produces large impulsive forces on the bottom plating
- reduce frame spacing
- additional stiffeners introduced
- increase shell plating thickness
What is Panting?
How can locality be stiffened to resist stress
Panting is the In and Out movement of the shell material due to varying pressure changes.
The area is stiffened by:
- closer frame spacing
- increasing shell thickness
- thicker keel plate
- thicker plate stem
- additional Panting stringers
adding additional stiffeners (panting beams)
Items found in General Arrangement Plan
-Side elevation / Profile of decks
-tanks
-accomodation, bidgelayout
-alleyways, ladders
-Ships name
-Yard number
-storerooms
-general dimensions
-deckplan
Side Stringer
Horizontal longitudinal girder giving support to the frames & longitudinal strength to the structure
Side Girder
Supports the floors and gives longitudinal strength to the Ship reducing the effect of Hogging and Sagging
Task provided by Classification Society
-supervise the building process and ensure quality of work
-Construction rules
-materials specs
-surveyors available
-resale value
-offer insurance
Directions of Movement a vessel can experience
Yaw, Heave
Surge, roll
Sway and pitch
Hogging
Happens when ship is supported at amidships and not on bow and stern
draw
Sagging
Happens when ship is supported at bow and stern and not at amidships
draw
Aluminium
Pros and Cons
Pros:
- light
- does not rust
- less maintenance
-good radar detection
Cons:
- expensive
- poor fire resistant
-corrodes rapidly in contact with other metals
FPR - Fibre reinforced plastic
Pros and Cons
Pros:
- corrosion free
- light
- easily repaired
- easily moulded
Cons:
- poor fire resistant
- osmosis
- easily damaged
Wood
Pros and Cons
Pros:
- buoyant
- light
- laminate use
- looks nice
Cons:
- expensive
- rots
- burns
- subject to insert attack
Steel
Pros and Cons
Pros:
- Cheap
- easy to repair
- good fire resistant
-good radar detection
Cons:
-needs insolation against condensation
- heavy
-corrodes
Rolling motion of the vessel `Tender´
long short slow and lazy roll
Pros:
comfortable
no stress on vessel
no moving of weights
cons:
easily inclined
less ability to return once inclined
Rolling motion of the vessel stiff
Short period of roll ; can be jerky violent
Pros:
reserve stability
difficult to incline
easy to keep upright
Cons:
uncomfortable
items move around
racking &structural stress
Racking
How to improve ?
When a ship is rolling in a seaway or is struck by beam waves, the ships structure is liable to distort in a transverse direction
Increase transverse bulkheads
beams and beam knees
web frames
Continues Center Girder
large Steel section running the length of the ship resting on the keel plate
It gives longitudinal strength to the ship and helps to resist hogging and sagging
Hull / Shell Plating
Watertight skin of the ship keeping the water out and supporting the structure
Upper and lower parts are thinker to give strength due to stress of hogging and sagging
Transverse Bulkheads
-sub-divides yacht into separate compartments:
-to contain flooding (w/t integrity);
-to contain fire;
-contribute to transverse strength of vessel; contribute to resisting of racking;
contribute to load bearing;
effectively distributes loads to adjacent structures.
Describe one method of cathodic protection.
That galvanic action is an electro-chemical form of corrosion where one of two dissimilar metals are eaten away. The metal that is eaten away is the one less Nobel in the Galvanic Scale. To counteract this in respect to mild steel, a metal more ignoble/anodic e.g. zinc or magnesium may be used and these are termed sacrificial anodes which will waste in preference to the steel.
Forward Perpendicular (FP)
Vertical line perpendicular to the base line where the Summer load line (SLL) crosses the stem.
After Perpendicular (AP)
Vertical line perpendicular to the base line where the Summer load line crosses the stern (passing through the rudder stock (on a conventional ship).
LBP
Lenght between perpenticulars
The length of the vessel measured between the forward and the aft perpendiculars.
Length Overall LOA
The extreme length of the vessel.
Camber
Transverse curvature of the deck, helping to shed water from the deck.
Sheer
Longitudinal curvature of the deck, adding buoyancy to the ends of the vessel.
Osmosis
Osmosis is the cracking or blistering of the surface. Gel coat damage allows water to come into direct contact with the resins which are porous and allowed water to be sucked in.
This increases the pressure in the gaps forcing the laminate apart and breaking up the FRP
Use Epoxy resin to improve and fix
Jet Bonding
- Explosive bolding is a method of joining two metals to give a corrosion free point
- gap is left between the two metals and once explosion is initiated, jet forces any particles out to have no corrosion occur
Light Displacement
Mass of the vessel when complete but with no passengers, stores, fuel, cargo – an empty ship
Summer Deadweight
Difference between lightship and Summer displacements at assigned freeboard. Load displacement - Light Displacement
Reserved Buoyancy
Volume of enclosed watertight spaces between Load line and Freeboard deck. The Reserve buoyancy must prevent the deck line from submerging when the largest watertight compartment is bilged
Gross Tonnage
Internal Volume calculated at a rate of 2.83m3 per tonne
Items to be found on Fire Plan
- Fire mains and Hydrants
- fixed fire extinguishing systems
- portable fir extinguishers
- firemans outfit
- fire lockers
- fire pumping arrangements
- LSA equipment
- escape routes
List items that must be checked in annual survey
- watertight integrity
- overboard discharges
- freeboard marks
- steering gear
- ventilation, scuppers, freeing imports
- anchors and mooring equipment
- stability checks
IACS
IACS = International Association Classification Societies
What plans are you required to have on board ?
- GA Plan
- Fire Plan
- LSA Plan
- Damage Control Plan
Watertight
Water cannot pass through in any direction
Weathertight
Water cannot pass through into ship in any sea condition
