Why Oil Tankers have lesser freeboard than General Cargo Ships?

Freeboard:

Freeboard is a vertical distance from the waterline to the uppermost continuous deck, also known as the Freeboard deck.

Why do Tankers have less Freeboard? 

An Oil Tanker have less Freeboard than General Cargo ships of similar LBP for the following reasons:

• They have considerably smaller deck openings in the Upper deck.

• They have greater Subdivision, by the additional longitudinal and transverse bulkheads. 

• The density of Cargo Oil is less than Grain Cargo.

• Tankers have much larger and better pumping arrangements to control any water ingress after a bilging incident.

• Tankers have larger Transverse GM values.

• In Tankers, cargo oil has a permeability of about 5% whilst Grain Cargo has a permeability of 60% to 65%. The lower permeability will instantly allow less water ingress following a bilging incident.