The measurement procedure for each vessel is exactly the same. From all roughness measurements an AHR, average hull roughness, is distracted. The AHR is a statistical number. For the statistics to count we need at least 100 measurements. The principle of the TQC hull Roughness gauge is based upon 120 measured sections. So we divide the hull into 120 sections, 10 horizontal sections and 6 vertical sections on both starboard and portside of the ship. For a 190m vessel each horizontal section measures 19 meters each.
The height of the sections is variable upon each ship. From the 6 vertical divisions on each side of the ship, 3 sections are spread over the bottom and 3 upon the side of the ship.
- Portside: 30 sections (3×10)
- Portside flat: 30 sections (3×10)
- Starboard: 30 sections (3×10)
- Starboard flat: 30 sections (3×10)
For the NB stage I’d like to refer to: ITTC Hull and Propulsor Survey Procedure 7.5-04-01-01.3.
For the existing fleet there is a lack of a baseline to compare the results against. Guidelines and reference point from other similar hull roughness surveys could be used. For existing vessels a new baseline can be determined after blasting and recoating. Future roughness surveys could be compared against the baseline.
Though different types of ships, tankers, bulk carriers, containers etc., have their own characteristics the principle of roughness surveys stays the same. The matter in which the hull condition effects the ship is different for each type of ship, container vessels for example have a greater influence of drag caused by wind because of the height of the ship compared to bulk carriers.