Why a Ship's Speed Is Measured in Knots: Actual Knots, in a Rope
Sailors threw a piece of wood into the sea, counted the knots in the rope behind it, and timed it with an hourglass. That is why speed is in knots.
All papers, articles, and talks
The Circle Painted on Every Ship Because One Man Lost His Temper
The circle on a ship's hull is there because one angry member of Parliament fought owners who overloaded ships for the insurance money. It still sets how deep a ship may load.
Energy-Saving Devices: Collecting the Propeller's Leftovers
A propeller leaves a third of its power behind in the water: spin in the slipstream, a vortex off the hub, and an uneven wake. ESDs are fixed steel aimed at those named losses: 1–5% each, forever, if the device matches the hull.
Air Lubrication: The Bubble Carpet and the Compressor's Bill
Air is 800 times less dense than water, so a bubble layer under the flat of bottom, the wide underside of the hull, all but erases local friction there. The saving is real, but only after the compressors take their cut, and only at the draughts the ship actually sails.
Wind-Assisted Propulsion: Lift, Not Nostalgia
Rotor sails, wingsails, suction wings and kites all work the same way: they turn lift into forward thrust. The saving depends on the route as much as on the hardware, and regulation now pays a premium on the proven figure.
Where the Fuel Goes: A Map of Energy-Saving Measures
Five families of efficiency measures, sorted by where they do their work between the fuel tank and the delivered cargo, plus the three questions that show what any vendor's savings claim is really made of.
Mud and Silt: The Seabed That Moves
Fluid mud recreates Nansen's dead-water mystery in modern ports: internal waves, yield-stress drag, and a seabed defined by density, not the echo sounder.
Wave Pattern Deformation: The Waves That Come Back
In open water a ship's waves leave forever. In a canal they reflect off the banks and return to the hull — added resistance governed by the blockage ratio.
Critical Speed: The Shallow-Water Resistance Wall
In shallow water waves cannot outrun √(g·h). As the depth Froude number nears 1.0 resistance spikes — and the trap starts at normal service speed.
Bank Effect: When the Channel Steers the Ship
Near a canal bank the bow is pushed off and the stern pulled in — a yaw moment that scales with speed squared. The physics behind the NTSB Genesis River case.
Squat: When Shallow Water Pulls the Ship Down
In shallow water the flow accelerates under the hull and pressure drops — the ship sinks bodily and trims, full forms by the bow and fine forms by the stern. Why squat is a resistance problem, not just a safety margin.
Shallow Water Changes the Physics: Five Effects
Rivers, channels, and port approaches play by different rules than open water. Five hydrodynamic effects — squat, bank effect, critical speed, wave deformation, and mud — reshape resistance, power demand, and safety margins.
Sea Currents: The Medium Fights Back
Currents alter the very water a ship sails through: head currents force a higher speed through water, and cross-currents force a drift angle — both quietly inflating fuel consumption.
Added Steering Resistance: The Autopilot Tax
Heavy weather penalizes a ship twice — once through wind and wave drag, and again through the rudder corrections needed to hold course. Steering drag grows with the square of rudder angle, and an over-tuned autopilot can quietly add 3–10% to fuel consumption.
Added Wave Resistance, Part 2: Radiation
In long waves a pitching ship becomes a wave-maker of its own — radiating energy stolen straight from the propeller's thrust. In a Beaufort 6 sea, wave radiation alone can exceed 20% of total resistance.
Added Wave Resistance, Part 1: Diffraction
Before a ship ever pitches or heaves, it loses energy to wave diffraction — short waves shattering against the bow act as an invisible hydrodynamic brake, even when the vessel feels perfectly stable.
Added Wind Resistance: The Square Law
Wind drag scales with the square of apparent wind speed — so headwinds punish fuel consumption far more than tailwinds help. Phase 2 of the vessel resistance series looks at the physics, and why wind correction decides whether your data blames the weather or the hull.
From Calm Water to Real Weather: Added Resistance
Wrapping up the calm-water resistance series and opening Phase 2 — added weather resistance, where the real fuel bill is decided.
Hydrodynamic Drag from Appendages and Steering
Two underestimated sources of drag: underwater appendages (bilge keels, rudders, shafts) and the cost of steering.
Air Resistance: The Headwind You Can't Escape
Even on a dead-calm sea, moving forward creates an apparent headwind. Why air resistance matters even without weather.
Viscous Pressure (Form) Resistance
The localised drag at the stern: how pressure recovery along the hull (or the lack of it) creates viscous pressure resistance.
Wave-Making Resistance
How a ship's hull generates a system of gravity waves as it advances — and why wave-making resistance is a key driver of efficiency.
Why Fleet Performance Culture Cannot Be Purchased
Buying a performance monitoring platform does not buy you a performance culture. This talk argues that the value of fleet data is unlocked by the people and habits around it — and looks at what actually changes behaviour on board and ashore.
Frictional Resistance: The Dominant Component of Drag
A technical look at frictional resistance — the ITTC-57 correlation line, Reynolds number, boundary layers, and why it dominates calm-water drag.
Frictional Resistance: Why Fouling Is a Performance Issue
Frictional resistance is one of the most underestimated drivers of inefficiency — and why fouling is a performance issue, not just a maintenance one.
The Five Components of Calm-Water Resistance
Even in calm water, hidden forces fight a ship's progress. A breakdown of the five fundamental components of total resistance.
Data Quality Is the Ultimate Form of Compliance
Is your vessel performance data an asset or a liability? Why data quality is the foundation of compliance in modern shipping.
Measuring Hull & Propeller Performance with ISO 19030
Poor hull and propeller performance is an underestimated cost drain — ISO 19030 gives operators a disciplined, data-driven way to measure and manage it.
Why Raw Data Isn't Enough: Engineered Data Pipelines
High-quality data is the only foundation for reliable insight — and that takes engineered data pipelines, not just collection.
Hull Fouling: The Hidden Tax on Fleet Operations
Hull fouling quietly raises fuel consumption, cuts speed, and undermines compliance — a challenge for technical managers, owners, and charterers alike.
Why Continuous Vessel Monitoring Is a Commercial Necessity
Continuous vessel monitoring is shifting from a nice-to-have to a commercial necessity for performance and decarbonisation.
Interpretable Data-Driven Ship Dynamics Model: Enhancing Physics-Based Motion Prediction with Parameter Optimization
A ship motion prediction model that combines physics-based equations with data-driven parameter optimization — keeping the interpretability of hydrodynamic models while capturing ship-specific behaviour. Validated on two container ships, with predictions over 50% more accurate than traditionally tuned physics-based baselines.
Comparative Study of Ship Motion Prediction Models: Data-Driven Physics-Based vs Pure Machine Learning
Two data-driven routes to vessel trajectory prediction go head-to-head: optimising the parameters of a physics-based hydrodynamic model versus a pure feed-forward neural network. Trained and 5-fold cross-validated on 90 simulated trajectories, the physics-based-with-optimisation approach wins — roughly 40% lower summarised error and 35% tighter consistency than the black-box model.
Towards Real-World Validation of a Physics-Based Ship Motion Prediction Model
Physics-based ship motion models are rarely validated against real-world voyages. This study tailors a physics-based 3D dynamics model to a container ship and evaluates its sub-second predictions against real vessel trajectories — visually and with multiple distance measures.
Advancing Autonomous Navigation with AI for a Sustainable Maritime Future
A COP29 talk on how AI and autonomous navigation are moving shipping from the 'dark ages' of vessel performance toward a measurable, incremental path to lower fuel consumption and emissions — and what it will take to reach fully autonomous, efficient sailing.
AI: Changing the Game — Today and Tomorrow
Where artificial intelligence is genuinely changing maritime operations today, and where it is heading next — told as a journey from the 'dark ages' of vessel performance to a practical, incremental path toward autonomous, efficient sailing.
Ship Navigation & Voyage Optimization — Conference Q&A
A question-and-answer session from the 2nd Ship Navigation and Voyage Optimization conference, covering audience questions on navigation, voyage optimization, and the data behind both.
Predicting VLCC Fuel Consumption with Machine Learning Using Operationally Available Sensor Data
Fuel consumption models often demand data operators simply don't have. This peer-reviewed study builds main-engine FOC forecasting models for a VLCC using only sensors and simple weather data that are routinely available — with XGBoost predicting within 5% of the true value in more than 86% of cases.
How to Establish a Culture of Energy Efficiency by Utilizing the Potential of Fleet Data
Fleet data has enormous untapped potential for energy efficiency — but only if it changes day-to-day decisions. This talk covers how to move from collecting data to building an energy-efficiency culture around it.
Voyage Efficiency for CII Compliance
CII turns voyage decisions into a rating with commercial consequences. This conference session looks at how voyage efficiency — speed, routing, and operational choices — feeds the Carbon Intensity Indicator, and what operators can actually influence.
Harnessing Energy-Efficient Habits with Data in Shipping
Energy efficiency in shipping is ultimately a set of habits — and data is what makes good habits visible, measurable, and repeatable. A virtual conference talk on connecting fleet data to the daily behaviour that determines fuel consumption.
Utilising Data for Smarter Vessel Maintenance
A Riviera Maritime webinar on how operational data turns vessel maintenance from a fixed-schedule routine into a condition-based, evidence-led practice — catching problems earlier and avoiding unnecessary work.
How to Establish a Culture of Energy Efficiency in Shipping
An article on why energy efficiency in shipping is as much about culture and habits as it is about technology — and how fleet data helps build that culture.
How to Improve Fleet Performance & Efficiency — ISO 19030
A ShipIT 2021 talk on improving fleet performance and efficiency, and how the ISO 19030 standard provides a disciplined way to measure changes in hull and propeller performance.
Parametric Design and Multi-Objective Optimization of SWATH
A parametric design tool for fast, robust optimization of SWATH (Small Waterplane Area Twin Hull) ships, developed at NTUA's Ship Design Laboratory and validated against the Aegean Queen ferry design — optimizing the hull form for two different seasonal operating speeds.