Free Board Mark Construction & Inspection

The following regulations concern the process, testing guidelines, and testing criteria for
freeboard marking which is done on the outer surface of the shell during ship construction. Before to read this article, you may read the relevant definitions at DRAUGHT MARKS AND SURVEYING.

Purpose
The purpose of this article is to test and manage quality by accurately regulating methods and standards of measurement, as well as to maintain measurement accuracy in the location, size, and measure of the freeboard marking process performed by ship according to floor plans based on I.M.O regulations and class requirements.

Terminology

Freeboard
Refers to the perpendicular distance from the upper side of the load line to the upper side of the freeboard deck on the midship area.

Freeboard deck
Generally refers to the uppermost area on the ship; the traditional deck, exposed to the outer atmosphere and seawater. (the upper deck is usually the freeboard deck, and if there are others such as a sunken deck, this sunken deck is referred to as the freeboard deck.)

Load Line
The maximum draft (restricted due to safety reasons) during sailing is called a full draft and the waterline at this point is called the load line.

fr1.png

*** S: SUMMER LOAD LINE
*** W: WINTER LOAD LINE
*** WNA: WINTER NORTH ATLANTA LOAD LINE
*** T: TROPICAL LOAD LINE
*** F: FRESHWATER LOAD LINE IN SUMMER
*** TF: TROPICAL FRESHWATER LOAD LINE
*** LTF: LUMBER TROPICAL FRESHWATER LOAD LINE

fr2.jpeg
Note: “L” letter is additionally marked on all wood carrying ships

Timber Load Line

A special load line assigned to ships complying with certain conditions related to their construction set out in the International Convention on Load Lines and used when the cargo complies with the stowage and securing conditions of the Code of Safe Practice for Ships Carrying Timber Deck Cargoes.

Freeboard depth
Value of moulded depth (M.D) + freeboard deck plate thickness

Freeboard length
96% the length of total length (includes thicknesses of stem/stern) at the water line for 85% of M.D, or whichever value is largest among distances from the front side of the stem to the rudder stock C.L at the water line for 85% of M.D is selected.
Note: must be distinguished from LBP.

Amidship
The center of freeboard length (LF); therefore it refers to LF

Freeboard mark
The various markings that distinguish the freeboard are called the freeboard marks. These are divided into three main types as follows: deck line, center of the ring, and load line.

Inspection Notes:

The distances between the ring center line and the letters specifying class differ by class.

fr3.png

The Designation of Deck Line
**For square gunwale type
Deck line is appointed upon the extension of a line parallel with the upper part of freeboard deck and the measuring point designated in below image.

fr4.png
**For round gunwale type
Appointed deck line at a point 1-2mm below the upper deck. In this case, the significance of the deck line is that it serves as the reference mark for easier measurement of freeboard to the load line.

 

fr5
In general, the minimum summer freeboard is the distance from the deck line top to the
summer load line top

Where to put the Circle Ring on ship?

The Circle should be done with amidship (at 1/2 of freeboard length or LF/2) on both Port/ Starboard sides symmetrically.

Welding and Tolerances?

Final touch-ups (by welding) must be done on freeboard markings that have gone through dimension inspection; basic principles specify that inspections in the presence of shipowner/ship registration are not done.
The dimension testing criteria should be assigned according to the Shipyard Standard. (Typical standards: ±0.5mm, tolerance limit ±1.0mm)

 

One thought on “Free Board Mark Construction & Inspection

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s