A second design error

So far, we have revealed that there were two design faults and one, what we would call, error in the in the design of the duff and offal chutes on the Gaul:

The principal design fault (for details, see this LINKED DOCUMENT and this VIDEO CLIP), related to the construction and arrangement of the chutes, meant that the non-return flaps in the duff and offal chutes on the vessel could have been opened by the action of the sea

The second design fault showed the possibility for the bolted assemblies of the non-return flaps to become twisted due to the force of the sea, and remain open thereafter (further details can be found at this LINK).

The design error described in our post of 26 June 2007 was a dimensioning mistake in the shipyard’s construction drawing which, in certain circumstances, could have caused the flap to jam in the open position, after having been opened under the action of the sea. (For further explanations please follow this LINK)

Now, we are presenting yet another design error (explained HERE as well as HERE): a miscalculation of the relative weights of the components of the chutes’ non return flaps, the consequence of which meant that a wave load of only 7.5 kg could have been enough to force them open.

It should be noted that the design of ‘non-return flaps’ within the duff and offal chutes should have enabled them to withstand the forces of the sea, close automatically and prevent water ingress. However, as a result of the inadequacies listed above, the action of the sea could have caused the flaps to fail in their main functions.

Thus, it is evident that the design of the Gaul’s chutes was vitiated by multiple flaws (and, we warn you, there is more to come) and that the unfortunate nature of these flaws was such that they augmented each other’s effects, rendering the vessel unacceptably vulnerable to flooding and capsizing.

A design error

"18.17... it is important to note that although both chutes were found on the wreck to be open both in way of the non-return flap and the internal top cover, there is no known mechanical reason why this was so." (Report of the 2004 Re-opened Formal Investigation into the Loss of the FV Gaul)

In the paper describing the MAIN DESIGN FAULT on the Gaul, we gave an account of how the closed flaps of the duff and offal chutes on the vessel could have been forced open by the sea at the time of the incident. (You can also see a model of the design fault captured on this VIDEO clip).

Furthermore, the factor tree analysis diagram, published earlier on THIS PAGE, presented a range of alternative explanations, as to how the outer flaps of the duff and offal chutes on the Gaul could have become open and remained in the open position (the RFI having only examined and accepted that the flaps were open, prior to the vessel’s departure from Hull, as a result of corrosion and lack of maintenance).

One of these alternative explanations (i.e. THE SECOND DESIGN FAULT), mentioned in an earlier POST, put forward the possibility that the bolted non-return flap assemblies within the chutes could have become twisted due to wave action and remained open as a result.

Today, we are presenting another alternative explanation, whereby a simple dimensioning error in the shipyard’s construction drawings meant that, if ever the brass gland within the flap hinges was loosened by the operation of the flap, parts of it could have bound together, thus causing the flap to remain seized in the open position.

THIS PAPER gives the details. (The document can also be viewed HERE)

A few essential details that went missing

In any major and costly marine accident investigation, such as the Gaul RFI, one would normally expect lots of data and information relevant to the identified cause of the tragedy to emerge and be made available.
Yet, looking at the government website: www.fv-gaul.org.uk, the sole repository of official information on the Gaul case, one cannot help wondering why so little was published about those things that were pertinent and central to the loss of the vessel, while many tangential issues were generously treated.

Anyway, to make up for the government’s oversight, we have taken it upon ourselves to publish some ADDITIONAL DATA from the vessel’s design plans together with a few detail views of the duff and offal chutes on the Gaul.

These diagrams, apart from adding clarity to the general arrangements on the Gaul and the construction of its chutes, also show that the RFI panel’s claim, that maintenance of the Gaul’s flap assemblies was not possible, is clearly not correct. [This latter aspect has, in fact, already been covered in the full TECHNICAL REPORT.]

Another small observation

The 2004 Formal Investigation into the sinking of the FV Gaul concluded, as we all already know, that the cause for the loss of the vessel was the ingress of a large quantity of seawater through the two duff and offal chutes openings in the hull of the vessel.

The double-barrier protections of these openings – the inner covers and the outer flaps - were found to be in the open position during the underwater survey in 2002.
The fact that the outer flaps were found open, the investigation concluded, was due to seizure caused by corrosion in the vessel’s 16 month old flap hinges and failure on the part of the crew and shore maintenance staff to identify and rectify this problem.
The fact that the inner covers were also found open was explained away by crew negligence.
However, the trouble with these findings (as we have attempted to explain in our earlier posts) is that they were based on unsubstantiated assumptions.

Let’s take, this time, the presumed corrosion at the flap hinges. (For a few more details on this issue please click HERE.)
As the same combination of materials, mild steel and brass, had been used in a number of other structures on the Gaul (e.g. for the toggles and clips on all weathertight hatches and doors), one would expect similar corrosion problems in those areas.
In reality, though, this doesn’t seem to be the case.
Quite the reverse, as the following clips[1] show, even after 28 years under the sea, the toggles and clips on the Gaul did not present such a level of corrosion and seizure that would prevent them from being easily unscrewed by the ROV[2] arm.

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[1] Extracts from the 2002 MAIB video footage - © Crown copyright
[2] Remote Operated Vehicle

weathertight hatch mild-steel clips & brass bush

weathertight hatch brass toggle & steel toggle bolt

weathertight hatch brass toggle & steel toggle bolt