VESSEL CONSTRUCTION

(Extracts courtesy of A.N.T.A. publications, Ranger Hope © 2008 www.splashmaritime.com.au)

 

Definitions

 

Panting

Is the stress which occurs at the ends of the vessel due to variations in water pressure on the shell plating as the vessel pitches in a seaway. The effect is accentuated when the vessel is making headway.

 

Pounding

Heavy pitching assisted by heaving as the whole vessel is lifted out of the water and “slammed” onto the water.

 

Hogging

  Is the bending of the hull, where the forward and after draughts of the vessel are greater than the midships draught. Caused either by vessel “sitting” on a wave crest or due to the weight distribution of the vessel.

 

Sagging

Is the bending of the hull, where the midships draught of the vessel is greater than the forward and after draughts.  Caused when the wave length is the same as the length of the vessel or by the weight distribution of the vessel.

 

Water Pressure

  Is the deformation of the vessel's hull that could occur due to the water pressure acting against the hull equal to the weight of the vessel.

 

Dry Docking

  Localised pressure on the vessel's hull due to the vessel resting on its keel and being supported by “chocks”.

 

Structural components

The name given to the various parts of a ship have mainly been derived from the old sailing ships and are now used to describe a part or section of a ship.

The following terminology is used on a regular basis by the seafaring community.

 

Vessels are built from a number of materials each of which has definite advantages and disadvantages. Each also has many characteristics that may be advantageous or disadvantageous when constructing a vessel for a specific purpose. The USL code recognises six construction materials and they are noted below.

Aluminium

It is light, easy to work, requires little maintenance, is non magnetic and is immune to attack by marine life.

Has a low melting point and poor fire resistance, is comparatively easily damaged and expensive.

GRP

Glass Reinforced Plastic or fibreglass.

It is light, lends itself to mass production, is easily repaired and does not rust or rot.

Has poor fire resistance, requires skilled construction and can be easily damaged.

Steel

Has good fire resistance, is not easily damaged and is cheap and easy to build.

It is heavy, corrodes easily and is magnetic.

Timber

It is easy to work, can be light, and has aesthetic appeal.

Has poor fire resistance, rots and is expensive.

Ferro cement

Has good fire resistance, is cheap, has a one piece hull and is corrosion free.

It is heavy, requires skilled construction, chips and is magnetic.

Copper-nickel alloy

Has good fire resistance, is rust free and discourages marine growth.

It is moderately heavy, skilled construction is required and very expensive.

 

Major Components of Ships

 


1  Apron

  A backing or strengthening timber behind and fastened to the stem post.

2  Bulkhead

  Vertical wall or division between compartments, adding to the strength of the hull and helps to prevent racking.

3  Butt

  An end-to-end joint between two planks or boards.

4  Butt block

  A short board fitted behind a butt in a side or plank to which the abutting planks are securely fastened.

5  Chine (Older form “chime”)

  The line formed by the intersection of the sides and bottom of a “Vee” or flat bottom boat. Hence the length of timber which forms the corner is called the chine timber or just the chine. Generally this is screwed or bolted to frames.

6  Dead wood

 


Term generally applied to timber used in the build of forward or after end of the keel structure, providing solid material for the fastening of stem or sternpost and horn timbers. The built up timbers are through bolted to the stern post, keel and horn timbers.

7  Engine Bed

The heavy timbers on which the engine rests and is fastened. These in turn are bolted to floors and stringers to give rigidity.

 


8  Dove Tail or Fish Tail Plates

Metal plates, usually bronze, let into the after end of keel and lower end of the stern post or rudder post. These plates are fitted each side and through bolted to hold the two timbers together.

9  Floor timbers

  Transverse wooden members crossing the keel and attached to the lower end of a frame and bolted thereto as well as to the keel. Plank fastening are frequently driven or screwed into floor timbers. Do not confuse with sole boards (or Bearers). Floors tie the bottom of the ship to the keel and help to prevent the sagging of the ship’s bottom.

10  Hog Piece (or Keel Batten)

  A flat timber member fastened to the keel forming a T-section which supports the garboard planking and helps to prevent hogging and sagging.

11  Horn Timber

  Timber or timbers connected to the after dead wood projecting aft to form the backbone of the overhanging stern.

12  Keel

  The principal fore and after member, forming the backbone of a boat’s construction and helps to prevent hogging and sagging.

 


13  Keelson

  A fore and aft member fastened on top of the floors through them to the keel and fastened to the dead wood at each end. Generally fitted in larger types of wooden ships. When fitted they further help to prevent hogging and sagging.

14  Knees

  Brackets shaped from grown elbows or crooks. Fitted under or along side beams at deck edge, or at the transom or stem. Metal fabrications, also laminations are now used.

15  Rabbet

  A groove cut along the edge of a wooden member such as the keel to receive and give backing to another wooden piece such as the garboard plank.

16  Shaft Log

  Portion of stern dead wood through which the shaft passes.

17  Stem

  The extreme forward member of the main framework of a ship to which stringers and plank ends are attached.

 


 

18  Stern Post

  The vertical post ending the deadwood at the stern. It helps prevent the deadwood blocks from twisting and also transmits the shock load from touching the bottom of the ocean through to the deck.

19  Stringers

  Fore and aft members extending from stem to stern inside the timbers of a carvel or outside of the framing in a sharpie.

20  Timbers (RIBS)

  Transverse members either steam bent or laminated onto which the planking is fastened.

21  Transom

 


 

 

Broad transverse area, either flat or curved at either end of the ship.