A Common Language for Hull and Propeller Performance

Every technical department has lived some version of this meeting. The coating maker's slide shows the hull performing beautifully. The charterer's weather-routing report shows chronic underperformance. Your own analyst shows something in between. All three used the same ship, the same months, the same ocean, and three different definitions of "performance."

That meeting is the reason ISO 19030 exists.

What the standard is

ISO 19030, Measurement of changes in hull and propeller performance, is the industry's agreed method for answering one question from in-service data: how has the hull-propeller system's performance changed between two periods of time? Not the engine. Not the weather. Not the crew. The wetted, rotating hardware that connects delivered power to speed through water.

The standard was developed through the 2010s by a working group spanning owners, coating makers, class and academia, and published in three parts. A readable account of its motivation and structure by two people at the centre of that work is openly available: the HullPIC paper ISO 19030: Motivation, Scope and Development, and it is this course's recurring open reference. (The standard itself is a paid ISO document; this course teaches its method and logic, in our own words, with the open literature as the citable trail.)

The three-part structure is worth memorising, because it is also this course's structure:

• Part 1: General principles. Definitions, the performance model, the primary and secondary parameters, the four indicators, and the method for estimating the uncertainty a measurement carries.
• Part 2: Default method. The full-accuracy recipe: continuously logged data, strict filtering to reference conditions, a wind correction for the records that survive, defined reference and evaluation periods, the computation of performance values and indicators, and the accuracy the default fit can expect.
• Part 3, Alternative methods. What to do on ships without the default instrumentation, acceptable substitutions and their quantified cost in accuracy, plus a few alternatives that match or better the default with elements not yet broadly used.

What it is not

A standard earns trust as much by its refusals as by its scope, and ISO 19030 refuses a lot. It does not measure engine performance: a drifting specific fuel consumption is invisible to it by design, because power is taken at the shaft, downstream of the engine's sins. It does not judge voyages, routing or crews. It does not correct heavy weather; it discards it. And it produces no absolute verdict, no "this hull is good", only change between periods computed the same way.

That last refusal is the deep one. The standard's authors understood that absolute performance claims inherit every uncertainty in the baseline, the instruments and the ship's particulars, while changes measured by a fixed method on the same ship cancel most of those uncertainties out. Relative measurement is what the method can promise to do well, so relative measurement is all it promises.

Why "standard" matters more than "method"

Nothing in ISO 19030 is exotic. Speed loss against an expected speed, filtered data, averaging windows: a competent analyst could have built (and many had built) something similar in a spreadsheet. What the spreadsheet could never provide is the thing the meeting at the top of this lesson was missing: a number both sides accept before the argument starts.

A coating guarantee written against ISO 19030 in-service performance can be enforced, once the contract pins the method down to the filter settings (lesson 8 lists what has to be pinned). A dry-dock business case built on its indicators can be audited by someone who was not in the room. A fleet that adopts the standard's vocabulary can compare its coatings and its cleaning vendors on one scale, ship by ship, and switch analysts, or software, without switching truths. What it cannot do, by its authors' own statement, is rank one ship against another: each ship is compared only with herself.

That is the promise. The next seven lessons are the machinery that has to hold for the promise to be kept: the performance model (lesson 2), the instruments and their failure modes (lesson 3), the filters (lesson 4), the computation from values to indicators (lessons 5 and 6), the low-instrumentation alternatives (lesson 7), and, honestly, the places where the standard runs out and judgment takes over (lesson 8).

If the standard is already familiar in outline, our course The Road to Efficiency gives it a lesson and reaches the same four indicators, this course is the same ground taken part by part. Meeting it twice is deliberate: the overview makes those indicators legible, while the eight lessons here make them computable.