This ship has been carrying chemical for whole of its life. Imagine there is an Oil / chemical tanker of 22000 T deadweight. There can be many reasons why loadlines are changed on ships with dual loadlines. The deck line marking is 300 mm long and 25 mm in width. It is not changed during the life of the ship. The deck line is fixed and marked when the vessel is built in the yard.

In Simple words, Deck line is line from where freeboard is measure and is drawn at a point on midship where deck plate meets the side shell plate. Its upper edge shall normally pass through the point where the continuation outwards of the upper surface of the freeboard deck intersects the outer surface of the shell plating. The deck line is a horizontal line marked amidships on each side of the ship. So here the Deck line comes into picture.

Does increasing the height of the fish plate make the ship more seaworthy ? Absolutely not. When we say 'freeboard', from what point we need to measure the freeboard ? Can we say we should measure the freeboard from the top most point of the side plating ? If it was so, I as the owner can increase the fish plate height and will be able to load more cargo. Loadline convention gave a way to calculate the minimum freeboard for a ship and plimsol marks are marked on the sides of a ship as per the loadline convention.īut why do we have the deck line ? What is its significance ? The point is that it is so important to have a minimum freeboard for any ship. The words 'plimsoll marks' were derived from his name. Samuel Plimsol worked really hard to pass a bill in the British parliament for minimum freeboard to maintain for the ships. He would load the ship with hardly any freeboard and these ship would obviously sink in usual bad weather.

Coffin ships because these ships were over-insured and it was more beneficial for the owner if the ship sinks. These ships were also known as Coffin ships. Long back the ships used to sail fully loaded and with hardly any freeboard. Samuel Plimsol is the person who has a great contribution to the maritime industry.

Margin plate ship construction