All shipping companies have implemented Performance Monitoring, Performance Management and then Operational Optimization to some extent. That's probably the most interesting because you have a picture of how the organization is made up and what type of policy is set, depending on ship type, operations and user data. It's often said that one thing that separates one company from another is how they use data; everybody has nearly the same data, but it's how a company uses that data and also the saving potential goes up as the commitment goes up! So, what is the purpose of hull and propeller performance analysis? For establishing economically optimal intervals for hull cleanings if it is required; propeller polishing and to compare fuel consumption for different hull coating systems?

I think everybody knows the coating suppliers these days are making some quite prolific claims on fuel savings attainable from using their coating systems. ISO is developing a standard for evaluating speed decay over time in attempting to give a level playing field to the hull coating suppliers. One thing that we have seen is that lot of the fuel savings that come from hull coatings is because of the blasting of the hull and not because the coating itself. Also, hull and propeller analysis has the purpose to reduce client need to develop and maintain an accurate fuel consumption system and to validate that ships are performing in accordance with charter party. In SEEMP there's discussion about propulsion resistance management and that can go from the entire range of looking over the side of the ship to see if it's fouled all the way to a more sophisticated approach where performance losses are accounted for due to hull and propeller condition by correcting the performance variables.

Unique data collection procedures are required as this type system usually cannot use noon data. Noon data presents a lot of changing variables and to put it simply, when the ships are steady its easier to get a good snapshot of the performance of the ship. It's also important in a robust performance analysis system to have some checks with met-ocean data. This could be the Global Real-Time Ocean Forecast system or the Near Real-Time Global Ocean Surface Currents models, because slight changes at sea state can cause an enormous change in performance (speed- FOC) of the ship. The point of this is to correct the performance data so that you can come up with an actual smooth curve from the scatter and performance data. It seems to me that the discussions and IMO about MRV and SEEMP are going to drive more and more interest in this area. SEEMP will become a more serious document for the goal-setting and more accountable on improving vessel performance.

What factors are in our control? If we want to improve the performance of the ship, we may select hull coating systems such as  Foul Release or Anti Fouling systems.  Regarding the frequency of inwater husbandry, it is important to polish the propeller anywhere from every three months, every six months or every nine months depending on condition and daily FOC. For the efficiency of inwater husbandry, there are several new hull cleaning robots coming out on the market, some been around for a long time and so there's discussion if unmanned or autonomous robot can clean the hull as efficiently as divers with machinery. Regarding hull blasting; from our experience one of the greatest performance losses on vessels sailing the seas these days is the minimal investment made in dry dock. I don't have a lot of experience with energy-saving devices; I know that a lot of their work is in a specific speed regime, they're not effective at low speeds but they're effective at high speeds whereas if you do a blasting of the hull and a good investment in the Hull Coating you have an energy efficiency that rides  with the ship its entire docking cycle at all speeds and drafts.

How do these changes in hull propeller resistance look like? There's a typical graph showing time history of added resistance as follows:

 

Added resistance is not equal to the added fuel consumption. Typically, a 10% increase in added resistance is equal to an 8% or 9% increase in fuel use (at design speed /draft, depending on hull form).

 

The resistance translates into speed consumption curbs as follows:

 

The Non- Dimensional added resistance translates into a speed/ fuel penalty

 

The picture below we may see where a whole fleet can be plotted in one graph. In the vertical access, you may see how fast is the hull and propeller fouling and in the horizontal line how much has been increased the resistance at the ship since last dry dock.

 

In summary, hull and propeller performance analysis is more popular and necessary now than at any time in the shipping industry.  Not only because it saves fuel and reduces emission, but also because it allows there to be a common and transparent understanding of the ship's Fuel Oil Consumption at all speed, drafts and weather factors.

 

Thank you