The combined effects of the Gaul’s stability shortfalls and duff and offal chute design faults

The principal finding of the 2004 Re-opened Formal Investigation (RFI) into the loss of the Gaul was that flooding of the factory space had occurred through two hull openings in the side of the vessel and that it was probable that this ingress of water led to the capsize and sinking of the Gaul.

Up until December of last year this blog focussed on a number of obvious design faults and flaws in the construction of the duff and offal chutes on the Gaul, and criticised the conduct and outcome of the 2004 RFI which, ignoring these facts had concluded that the flooding and loss of the vessel had been caused by the crew’s failure to close the inner covers of the duff and offal chute hull openings. Recently, however, we have added a summary of the results of a separate investigation, which has revealed significant stability shortfalls (on IMCO’s minimum stability standards [*]) that would have affected the Gaul in a number of her normal operating conditions.

As far the capsize and loss of the vessel is concerned, it should be noted that, while the stability shortfalls and flooding of the factory space through the duff and offal hull openings (facilitated by defective closing arrangements) are two different matters, they do not suggest differing causes for the loss of the Gaul; in fact, the impact of each is complementary to the chain of events which led to the loss of the vessel.

The stability reserves of a trawler may be regarded as a finite but variable quantity, dependent upon the vessel’s condition of loading, disposition of fuel, water etc. If seawater is allowed to flood into the hull, the stability of that trawler is reduced and the possibility of capsizes rises.
The 2004 RFI concluded that an ingress of about 100 tonnes of seawater (entering through her duff and offal chute openings) would have been necessary before the Gaul’s stability reserves would have been depleted to a level where capsize was probable in the weather the vessel encountered.
Our investigation has shown that, because the Gaul’s actual stability reserves were initially much lower than those assumed by the RFI, capsize would have been probable after only a modest ingress of seawater.

However, regardless of the design faults in the chutes’ closing arrangements, the Gaul’s stability problems and their combined effect on the safety of the vessel, the 2004 RFI was still content to attribute her loss to a failure on the part of the crew to close and secure the duff and offal lids during the storm they encountered on 8 February 1974.
Their conclusion, however, appears now extremely far-fetched.
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[*] One of the most important safety standards for a sea-going trawler is that it should meet the IMCO minimum stability criteria, however:

- Compliance with the IMCO minimum stability standard does not guarantee that a trawler will be safe from capsize in severe weather
- A trawler having stability reserves that significantly exceed the IMCO minimum standard is unlikely to capsize in severe weather
- Non-compliance with the IMCO minimum stability standard does not automatically mean that a trawler is likely to capsize in severe weather
- A trawler having stability reserves that fall significantly below the IMCO minimum standard is likely to capsize in severe weather.

Laying the blame on those who cannot defend themselves

(click to enlarge)

The areas coloured in orange represent the critical down-flooding openings, which were deemed to have played a part in the loss of the Gaul.
The areas coloured in blue (the funnel vents) are also critical in the down-flooding scenario, although these are meant to be kept open at all times.

The duff and offal chutes were found open on the wreck. The 2004 RFI concluded therefore that they had been left open by the crew.
As we have attempted to demonstrate on these pages and in the attached documents, the chutes’ outer flaps had a design fault, while their inner covers could not provide sufficient protection against flooding.

The fish loading hatches and the net store hatch, as our previous post explained, could have been opened by air pressure or by the force of internal floodwater acting on them from inside the vessel.
The RFI panel’s opinion, however, was that these hatches, also, had been left unsecured by the crew and had opened due to gravity when the vessel was sinking.

The engine room escape door, the RFI surmised, had been opened by one of the crew when trying to escape from the lower deck at the time of the incident.
In the absence of any contrary evidence, the hypothesis that this door had been opened by air pressure is again more probable.

The RFI panel concluded that the access door to the accommodation space, also, had been left open by the crew; and we can contend again that trapped air pressure or internal floodwater pressure could have opened it just as well.

As to the factory deck access door the RFI concluded, this time on the basis of some tangible evidence, that the crew had failed to secure it in the closed position.

All in all, the only conclusion we can draw from the dubious RFI findings is that the 2004 investigation panel was too eager to suggest a pattern of widespread crew negligence and to lay the blame for the loss of the Gaul on the victims to bother about plausibility.
Ignoring the existence of alternative explanations, underpinned by simple scientific principles, the RFI panel chose to put forward a loss scenario that was not only unsupported by any credible evidence, but also defied common sense.

The fish loading hatches on the Gaul

In 1999, in the year following their first underwater survey of the wreck of the Gaul, the MAIB produced their Marine Accident Report no. 4/99.
Amongst other things, this report put forward the MAIB’s hypothesis as to why the two large fish loading hatches on the Gaul had been found open during the survey. This stated that, at the time of the loss, the hatches had been unsecured and that they had therefore fallen open during the vessel’s capsize and sinking ’by the stern’.

As we have attempted to demonstrate in the document published at this LINK, the MAIB analysis, taken as read by the 2004 RFI panel, appears to have been seriously flawed.
The error it contains relates to one of the possible mechanisms that could have opened the fish loading hatches, namely, an increase in pressure of the air trapped between the water that was flooding into the vessel and the under side of the closed hatches.The MAIB report stated that the maximum lifting pressure on the underside of the fish loading hatches was only 478 N/m² (49 kg/m²), and that this would occur, for some unknown reason, when the vessel was exactly 80m below the sea surface. (!?)

A simple calculation can show, however, that if the Gaul had had a trim by the head of only 5º [1] and had been submerged to merely two metres below the sea’s surface, the lifting pressure on the underside of each fish-loading hatch could have been of the order of 900 kg/m² (i.e. approximately 3.5 tonnes per hatch), while the self-weight of each hatch was approximately 0.9 tonnes.

This ‘error’ meant that one plausible scenario for the opening of the hatches was incorrectly eliminated from the formal investigation, while another similarly plausible hypothesis – the possibility of the hatches having been opened by the force of internal floodwater acting on the hatches from inside the vessel – was not even mentioned.

Here again, as in the case of the duff and offal chutes, the preferred explanation was crew error.

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[1] Although both the MAIB and RFI experts have concluded that the Gaul sank initially and sedately by the stern, this theory cannot be relied upon with any degree of certainty, as it does not take into account the dynamic loads and ship motions that the vessel would undoubtedly have experienced, whilst at or near to the sea’s surface and following the redistribution and loss of buoyancy that would have occurred, as it flooded and sank. At the time of the loss the weather was extreme, with a significant wave height of circa 10m and with infrequent individual waves of up to 19m in height.