Samuel Plimsoll and the development of vessel Load Line legislation
Samuel Plimsoll and the development of vessel Load Line legislation.
Have you ever looked at a ship hull and wondered what the lines were called? David McNeil a retired merchant seaman can answer this question
The marks halfway along the hull indicate how much load the vessel can carry, it may come as some surprise that the man who had the idea faced lawsuits from shipowners anxious to stop him because they were convinced he would put them out of business or leave them facing financial ruin.
The enormous loss of life sustained by the seafaring fraternity of years ago was not, it seems, at the forefront of their minds.
A stone bust of Samuel Plimsoll stands on one side of the river in Bristol, gazing with petrified authority upon the graving dock where the SS Great Britain sits in its state-of-the-art preservation dock on the other side. To the best of my knowledge and belief, the SS Great Britain does not have any load-line markings on the hull.
Samuel Plimsoll was active in this area during the transition from wooden hulls to steel. The full transition is wood to composite, composite to iron, iron to steel. Reproductions of drawings of the Cutty Sark in my possession show a vessel built in 1869 with tonnage marks in the form of the first Plimsoll line on the hull. These appear in the forerunner of the general arrangement drawing that became standard in vessel design. To anyone looking at them now the lines of the vessel can be clearly discerned along with the dimensions that can be calculated from the scales drawn out.
Before I go any further I think it right to identify some of the lines appearing either side of the original, circular, plimsoll mark. They are as follows.
- Tropical Fresh.
- Salt Water.
- North Atlantic.
WNA. Winter North Atlantic.
The letters that sit on the line either side of the circle denote the Classification Society that originally assigned the Freeboard. Freeboards may, from time to time, need to be re-assigned. Here are some instances where this may be necessary.
- Vessel lengthening.
- Change of vessel type.
- Change of trade from Coastal to Foreign-Going and vice versa.
You will clearly see that the vessel will float at different draughts in different water types and temperatures. In Plimsoll’s time this was not widely understood.
Samuel Plimsoll’s career as an MP stands out as an example of the sort of thing that statesmen politicians ought to do. Engage in the development of workable legislation that improves the lot of the greater number of working men and women.
In the same way that the first Factory Act sought to improve the working conditions of apprentices (Children; slaves had been liberated by this time) Plimsoll’s work sought to increase the chances of survival of the seafarers who either transported the wealth of the nation to client states or the resources to be transformed into that wealth. Both the Factory Act and the Merchant Shipping Act had small beginnings. They both grew to encompass huge numbers of sections with the passage of time. Following the Napoleonic Wars, Britain became more dependent upon sea trade and the families with shipyards in their inventory sought to make a killing.
Plimsoll’s primary concern was with the vessels that carried timber as deck cargo. That the holds were full of the same material was neither here nor there to the shipowners of the time. The timber became wet in transit, vessels capsized and went down. It may have looked perfectly in order on departure.
Without too much detail, the timber became heavier when wet and this caused a reduction of the transverse metacentric height. This leads to instability. Roll too far in one direction and……..oblivion.
In a purely academic sense, it could be argued that if all it took to cause the loss of the vessel was a deck cargo getting damp, the metacentric height may have been too small when the cargo was loaded dry in the first instance.
At one point in the uninformed social arguments about the Herald of Free Enterprise loss in 1987, it was said that the quantity of water on the car deck was purely academic. Its presence in any depth may have been sufficient to cause the calamity.
The arguments thrown at Samuel Plimsoll by the shipowners centred upon one premise.
“How do YOU know,” they said “just WHERE that line should be?”
Samuel Plimsoll had NO idea at all.
The fixing of load lines at this time was purely arbitrary. Calculations that could establish, either by mathematical evidence or deduction, where it should be were conspicuous by their absence.
The loss of any vessel, for the ship owner, was not of any great consequence. The insurance paid out.
At this point we should all make a cry of lamentation, great wailing and gnashing of teeth in support of this self-serving, self-interested club the while wearing sack cloth and ashes.
Lloyd’s of London had what some might describe as dodgy beginnings. It was a coffee house in London which served the new and fashionable beverage that had caused so much trouble in Europe after the Moors abandoned the siege of Vienna leaving sacks of beans behind them. The Viennese picked them up, sniffed them, ground them and stewed them. Bach composed a Cantata drawing attention to the slightly narcotic properties. The Coffee Cantata is worth a listen, has a wonderful musical resolution to the counterpoint in the best of Baroque styles without the froth.
The coffee in Lloyd’s was stewed to oblivion and served to men in powdered wigs smoking clay pipes while discussing the insurance risks on vessels trading in and out of London. They had classifications which, in altered guise, still hold true today. They were Good, Middling and Bad. These were assigned according to information received, known or suspected. It could be anything from the vessel’s observed condition to the quantity of liquor loaded for the Master’s consumption before the voyage.
One event that did concentrate minds was the transitions I mentioned earlier. The transition to iron hulls was marked with an increased number of losses. Wooden vessels would creak and make other noises which could be heard and this was a sure way of knowing whether to lower sail. Ship handler vocabulary was peppered with all manner of adjectives that described how the ship sounded in a seaway.
Iron vessels just cracked and that was it. They went down almost without warning. Plimsoll saw these transitions and events with mounting alarm.
As the new materials became more common it became clear that iron and steel used in ship construction was subject to something called stress and while metal fatigue was a condition yet to be better understood, vessel designers and builders had to design new ways of putting strength into their products and vessel framing began to be adopted.
Plimsoll’s activity led to the first Merchant Shipping Act of 1876. This made a load line compulsory on all foreign going ships. This was a circle with a diameter drawn horizontally and extended outside the circle as illustrated. The idea was that the water, when loaded, would simply not reach this line.
From one book in my possession, here is the original wording.
“That the centre of the disc shall indicate the maximum load line in salt water to which the owner intends to load that vessel for that voyage.”
Two points emerge from this. The Owner is now legally liable. The second is that the load line makes no allowance for a change of the water during the voyage.
At this time, rules were not in existence to determine the ‘right and safe’ position for the load line at a defined position as prescribed by government rules. In other words, the new Act made no mention of HOW the load line position was to be calculated. Simply that there had to be one on either side. But…….where?
It is worth quoting the lines from my book on Load Line calculations, published in 1945 and used by my Father from 1950.
“To restore to life the dead bones of history from the valley of despair would only still further confuse the mind of the reader whose business brings him into contact with Government Regulations.”
Who said books on topics as dry as this were not entertaining?
This is a tacit admission that the history of Load Lines is tortuous so, we will keep the story as simple as it can be made.
Then comes an astonishing admission.
“The Load Line Regulations have no claim to be based upon scientific investigations.”
And this is a statement made against a backdrop of increasing use of mathematical analysis for the solution of many problems, even in the 19thcentury?
Initially, there were Freeboard Tables drawn up in 1886. The requirements for the load line, as rules in some form, did not become compulsory until 1890. In other words, guidance was available before the rules. These rules were later to be incorporated into an International Load Line Convention.
The term “Freeboard” is the distance at longitudinal ‘midships from the Freeboard Deck to the water line. This is the first mention of a datum, in any form, about which Plimsoll could not be clear.
By this time, Lloyds Register of Shipping had clear ideas about the dimensions to be used. Even here, this is still a huge assumption.
“The Freeboard tables originally introduced in 1886 were formulated on the assumption that the ship was strong enough for the freeboards assigned, and that the scantlings used were in accordance with the 1885 Rules of Lloyd’s Register for the 100A, spar or awning Class, as the case might be.”
The term “Scantling” is a curious word which is still used in this context and means the dimensions of principal constructional features. The word origin is possibly Norse. Not even my huge Chambers Dictionary lists it.
Two points come from the quote above. The assumption is that the vessel is strong enough and not “scant” in its constructional features. The second is that the vessel has been built to a set of Scantlings that has been established over many years of experience. By now you may have some idea how all of this came about. The scantlings used are the first indication of what we now understand to be the Construction Rules for a vessel. Every vessel type has them. Even Cross Channel Ferries.
You may imagine then, the difference between these rules for a passenger liner and a bulk carrier of a similar tonnage. This was why the then Board of Trade wound up with egg all over its face in connection with the Titanic. The Clearance Certificate for the vessel did not properly reflect the vessel type and, as such, the vessel was found wanting with respect to Lifeboat provision.
By now it is clear that the business of load line assignment was acquiring a vocabulary all of its own that was never heard in Plimsoll’s time. Out of it comes one term for which he must have been clutching during his arguments with Ship owners, anxious to stop him.
The Freeboard Deck is the deck from which the load line is measured when assigned.
From my text, here is how Freeboard Deck is defined.
“It is the deck from which freeboard is measured. If the deck is continuous, it can be identified as a freeboard deck. If not, it must have permanent means of closure for all openings where the deck is exposed to weather. This includes all such openings as hatches, water tight doors that open outwards, that would permit persons to enter parts of the vessel from exposed decks.”
In summary, the work of Plimsoll not only formed the first legislation on Merchant Ships in respect of safety but it also led to the first Construction Rules for vessel types to which designers had to conform. It also led to the first considerations on vessel stability and ensuring that guidance was in place that would prevent the vessel leaving port in an unstable condition or reaching that condition at some point in the voyage. This is called the angle of vanishing stability which is the angle of heel at which the Righting Moment, the lever that restores the vessel to upright, vanishes totally.
So we have one Member of Parliament with a conscience and a bunch of men in powdered wigs to thank for the increase in Maritime Safety. Not bad really.
This does not alter the fact that we still lose ships and the last time I looked a Bulk carrier was lost at the rate of one per month with all hands. Ferries remain, the world over, among the most likely vessels to capsize or sink for one reason or another.
Written by David McNeil