A Note On Hull Performance

A vessel's fuel performance usually begins decreasing after six months from dry-dock and continues to decrease rapidly. Underwater marine growth, barnacles, and/or sea grass can cost a ship owner millions of extra dollars in time and fuel costs each year. To prevent spending additional dollars for fuel, a ship should be cleaned twice a year. The following example shows the projected net fuel savings, with hull cleaning, for tankers maintaining speeds of 13 knots over a 24-month dry-docking cycle.

A new VLCC tanker uses approximately 96 tons of bunker fuel per day and 610 barrels of fuel per 24-hour period. The cost per day for fuel alone would be approximately $30,000 with an additional $20,000 for operating expenses per day. On an average 15,000-mile cruise, the VLCC tanker would make the cruise in about 25 days with a clean hull. If the ship's hull is fouled with marine growth not exceeding 0.5 inch, the same trip would take 28 days. The difference is the loss in speed of over 2 knots, which equates to 3 days. Those additional three days cost $90,000 in fuel consumption alone.