Question

What is a margin plate?

Margin Plate is the outboard strake of the inner bottom and when turned down at the bilge the margin plate (or girder) forms the outer boundary of the double bottom.

Question

What is a Margin line. This is a line drawn parallel to and 76mm below the bulkhead deck at side (see Figure).

Question

How is the length determined?

Loss is generally accepted to occur when the damaged waterline is tangent to the bulkhead deck line at side.

The bulkhead deck is the upper most weathertight deck to which transverse watertight bulkheads are carried.

A margin is desirable and the limit is taken when the water line is tangent to a line drawn 76mm below the bulkhead deck at side. This line is called the margin line.

The floodable length at any point along the length of the ship is the length, with that point as centre, which can be flooded without immersing any part of the margin line when the ship has no list.

[Floodable length.

This is the maximum allowable length of a compartment at any point along the length (with that point as centre), that can be flooded without submerging the margin line. Vessel to be always upright, with no heel.]

What is Subdivision load line.

This is the waterline corresponding to the normal designed waterline.

It is drawn parallel to the ship’s keel.

Subdivision length (L). This is the length measured between the perpendiculars erected at the ends of the subdivision load line.

Subdivision beam (B). This is the greatest breadth, at or below, the ship’s deepest subdivision load line.

Subdivision draft (d). This is the moulded draft to the subdivision load waterline.