Paid PractitionerCertificate
Currents and Water Properties
The weather term that, in a uniform stream, is not a force: what a current actually does to a ship, why it changes required power without adding resistance, how it disguises itself as hull degradation, and what the water itself, its density and viscosity, genuinely does add.
- Lessons
- 7
- Quiz questions
- 63
- Exercises
- 1 (10 min)
- Calculators
- 1
- Time
- About 72 min
- Price
- €169+ VAT
- Certificate
- Graded final exam, then a PDF certificate with a number anyone can verify
- Who it's for
- Performance analysts and superintendents who compute or defend speed-loss figures, charter-party analysts arguing about good weather and adverse current, and anyone who has wondered why two analysts get different answers from the same voyage.
- Assumed knowledge
- Our course Ship Resistance Fundamentals for the calm-water floor. If you have met the speed-through-water problem in our ISO 19030 or ISO 15016 courses, this course is where it gets settled properly.
- Taught by
-
CEO & Founder, Blue Autonomy
- Naval architect and marine engineer, National Technical University of Athens
- 15 years of experience in fleet performance and operational data
- Chief Scientific Officer, NEMO, previously DeepSea Technologies, StormGeo, Athenian Sea Carriers, PwC
Part of the Added Weather Resistance specialisation.
What you will be able to do
By the end of the course. Each outcome names the lessons that deliver it, and the final exam samples every one of them.
- Explain why a uniform current adds no resistance to a hull, and convert between speed over ground and speed through water using the along-track component of the current. Lessons 1, 2
- Price what a current does instead on the speed-power curve, one cosine and one cube, sliding along the curve rather than inventing a force. Lesson 2
- State the direction convention of every channel in a performance dataset, normalise the current's towards-convention once at the boundary, compute a folded relative angle correctly, and design the test that catches a 180-degree sign inversion. Lesson 3
- Recognise a one-signed current artefact masquerading as hull fouling in a speed-loss trend, and apply the four defences, calibrated log, current filter, balanced headings and speed cross-check, in order of strength. Lesson 4
- Separate the crab angle, which is geometry, from the drift-and-rudder cost a beam current puts on a ship holding her track, size the rudder's induced drag in shaft power, and justify measuring rudder angle over modelling leeway. Lesson 5
- Compute the density and viscosity corrections the water itself genuinely adds, and argue an adverse-current clause or a current-riding diversion on the along-track component, stating the provenance that makes the figure defensible. Lessons 6, 7
Every other weather term in this specialisation is a force. Waves add resistance. Wind adds resistance. Current does not, and that single fact is the most misunderstood thing in vessel performance.
A ship in a uniform current is a ship in a moving room. The water it moves through does not know it is drifting; the hull sees the same flow, the same Reynolds number, the same resistance. What changes is the ground the ship covers. So current does not push on the hull: it moves the goalposts of the speed you are measured against. That distinction sounds academic until you notice how much rests on it: whether a speed loss is real or an artefact, whether a charter-party claim survives, whether your speed log or your GPS is the number that belongs in the calculation.
This course takes the whole of that problem. First the physics of why a uniform current adds nothing, and the along-track arithmetic that converts a current into the speed through water the engine actually has to produce. Then the sign convention that catches everyone: currents are reported by the direction they flow towards, while every other weather variable is reported by the direction it comes from: a 180-degree error that survives plausibility checks because the answer stays the right order of magnitude. Then the failure that costs real money: current masquerading as hull fouling, and the filtering and velocity-reference discipline that prevents it. Then the cross-track half of the problem, honestly bounded: drift, rudder and why serious practice measures the rudder rather than modelling the leeway.
And finally a term that is a genuine resistance, whatever the current does: the water itself. Warm water is less dense and less viscous than cold, and the difference is worth about a per cent of shaft power on a tropical trade, one-signed, systematic, and invisible unless you correct for it.
The opening lesson is free to read as a sample. By the end you should never again accept a speed-loss figure without asking which speed it was measured against.
What the course covers
- The Current That Adds No Resistance 8 min
- The Along-Track Component: One Cosine, One Cube 9 min
- The Sign Trap: Direction Conventions and the 180-Degree Error 9 min
- When Current Masquerades as Fouling 19 min + exercise
- The Cross-Track Half: Drift, Rudder and What to Measure 9 min
- The Water Itself: Density, Viscosity and a Real Correction 9 min
- Currents in Contracts and Routing 9 min
How was this course?
You have completed every lesson. One rating and, if you like, one line: it goes to the author, and it is how the course gets revised.
€169 + VAT
Paid once, for one person, for as long as the Academy runs: every lesson, the Excel workbook, the final examination and the certificate. Part of the Added Weather Resistance specialisation, which costs less than its courses bought one at a time.
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You own this course. Every lesson below is open to you.
Common questions
What exactly is included?
7 lessons (about 72 minutes in total), 63 quiz questions with explained answers, and 1 working Excel calculator: Current, speed reference and the false speed loss.
How much does it cost?
€169 plus VAT, paid once: €209.56 with 24% VAT, which is what an individual in the EU pays; outside the EU no VAT is added, and a company in another EU country with a VAT number valid in VIES pays the net price. That buys every lesson, the Excel workbook, the final examination and the certificate, for one person, for as long as the Academy runs. The course is also part of the Added Weather Resistance specialisation, which costs less than its courses bought one at a time. Everything else is on the pricing page.
Is there work to do, or is it only reading?
1 lesson carries a required exercise, about 10 minutes of hands-on work in total. You download that lesson's Excel workbook, follow the numbered steps against the numbers the lesson states, then change one input and watch the answer move. The exercises are where the method stops being something you have read and becomes something you can run; the stated course time includes them.
Do I get a certificate?
Yes. The course ends with a graded final exam, marked on our server rather than in your browser: you see your score and which questions you got wrong, but not the answers, because the questions are drawn from a pool. Pass it and you get a PDF certificate in your name, with a certificate number on it.
That number is the point. Anyone you show the certificate to can check it themselves at academy.blueautonomy.gr/verify, with no account and no email to us: the page states the name, the course and the date we issued it. A certificate nobody can verify is a decorated PDF, and we would rather issue one that stands up.
Can I preview the course?
Yes: the first lesson, The Current That Adds No Resistance, is free to read in full. It is a real lesson, not a trailer: same depth, same quiz.
Do I need prior knowledge?
Our course Ship Resistance Fundamentals for the calm-water floor. If you have met the speed-through-water problem in our ISO 19030 or ISO 15016 courses, this course is where it gets settled properly.