Of science friction and chocolate fireguards

For his latest monthly column, Pierre Aury picks out two numbers – 43 and 75 – as a source of inspiration.

This month numbers have provided some inspiration. And no we are not going to be debunking some numerical myths nor are we going to make a case about the fact that if numbers, allegedly, don’t lie they can be tortured and framed to tell pretty much anything. Everybody knows that. Courtesy of the summer break we are simply going to meander around some selected numbers: the numbers, for this month, are 43 and 75. We will visit other numbers later in the year.


Like the 43 mt fuel consumption of the Baltic Cape size index vessel which is described as sailing at 12 knots laden and 13 knots ballast on 43 mt of fuel oil with no diesel at sea. But why is that amount of fuel needed?

We will answer this question by revisiting Newtonian physics applied to a 182,000mt dwt modern capesize sailing at 12 knots. In an ideal world that is to say a world without any friction once an object has been “pushed” it is accelerating to reach a speed commensurate with the initial push and then, again in a world without any friction, once the “push” stops the object continues forever at the speed set by the “push”. The “push” or thrust, expressed in newtons is simply the mass of the ship in kilograms multiplied by the acceleration of the ship in meters per second per second (m/s^2). If we assume the laden vessel to reach its 12 knot speed in one hour the thrust required is a very small 311,220 newtons. This thrust applied over six nautical miles translates into 3,458,276,640 Joules which expressed in quantity of heavy fuel oil is only 0.086 tons or 86 kg assuming 40,000 kilo joules of calorific value per kilogram of fuel. This long detour to confirm one thing that every naval architect and any marine propulsion engineer is aware of. That thing being that the fuel consumption of a ship is not to bring a ship to a certain speed but solely to maintain it once reached.

Expressed differently the power requirement for a ship to maintain a certain speed is solely dependent on the resistance met by the ship while moving through the water. This resistance is made of different components including the hull shape and the water friction on the hull.

The holy grail of shipping decreasing its CO2 emissions for the years to come is not to be found in improving the efficiency of engines which are already as efficient as they can be or using fanciful fuels nor in decreasing the speed of the fleet but in eradicating or at least dramatically reducing water resistance. Science friction? Perhaps but given the numbers it is odd that so little resources are dedicated to reducing water friction.

On the shape of hulls (10% to 20% of the total resistance) a lot of progress has been made in the past and it is unlikely that major improvements are made again. This leaves us with the reduction of friction of the water on the hull (80% to 90% of the total resistance) which can be dealt with in two different ways. One is to separate the hull from the water with, for instance, air bubbles injected between the hull and the water. The other one is to use more efficient paints. Improvements have been made there and now we even see charterers paying owners to apply low friction coatings on long term time chartered ships.

However, at the same time we are devoting too much time and resources to tally CO2 emissions real time when the real time bit is as useful as a chocolate fireguard. What is the point of reporting CO2 in master’s noon reports and having these reports certified through AI-powered systems when the CO2 emitted is there to stay in the atmosphere for 300 to 1,000 years? Perhaps an annual compilation of marine fuels invoices, although less glamorous, would be more than adequate if coupled with a good old carbon tax embedded in the fuel price? Throwing AI to deal with CO2 emissions is clearly, yet again, a case of rearranging the deck chairs on the Titanic.


Like in the Allianz Global Corporate & Specialty (AGCS) analysis of almost 15,000 marine liability insurance claims between 2011 and 2016 which shows that human error is the primary factor in 75% of the value of all claims analysed, claims with a total value equivalent to over $1.6bn of losses meaning that such a sample has some statistical relevance. It is so statistically relevant that some companies have concluded that removing the human element from ships will dramatically reduce the number of accidents at sea hence the push for unmanned ships. A no brainer Really?

There is a commonly accepted definition of what an accident is: an accident is an uninterrupted chain of incidents.

Humans onboard of ships, like your scribe a long time ago, do intervene all the time to stop chains of incidents before they become accidents. Unfortunately stopping a chain of incidents before an accident happens is not the object of any statistics but the odds are that there are many more interrupted chains of incidents, courtesy of human intervention than there are uninterrupted chains of incidents ending up as an accident due to human error.

In a nutshell removing the human element from ships is more than likely to lead to a substantial increase in the number of accidents. Statistics on their own, statistics without a context are nearly always leading to erroneous conclusions a bit like the latest statistics from France showing that 30% of lethal car accidents are caused by inebriated drivers. Therefore 70% of accidents are caused by sober drivers. According to these statistics and the logic applied above to accidents in shipping sober drivers should be banned from driving in order to see a dramatic decrease in the number of lethal car accidents.

More on other selected numbers later in the year.

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