Martin & Ottaway has been involved in dozens of capsize failures. Capsizes are strange events because the cause of a capsize can be difficult to determine.
There are clear incidents of negligence with regard to capsizes, but, in our experience, about half of the world's capsizes strike like lightning on a clear day, and are totally unexpected. Then the analysis and cause determination becomes quite complex and often tracks back far in time.
Often there is fingerpointing, but it often loses track of the actual cause of the incident. One such incident that we worked on was the Ethan Allen in 2005.
The vessel capsized in mostly normal operating conditions with passengers aboard and loss of life. The analysis indicated that there were a number of factors at work which, together, interlinked to result in the subject incident and there was a red herring.
The red herring issue that was raised related to a modification of an existing canopy. The modification was performed by Scarano Boats in 1989, who, ironically, also performed the post incident stability test in 2005 on behalf of the NTSB.
At the face of it, it appeared that the change from a steel pipe canopy to a rigid wood canopy reduced the stability, but a closer examination shows that the modification was completely acceptable within existing USCG stability regulations. As a matter of fact, under the existing stability requirements, the canopy modification allowed the vessel to carry 14 passengers as compared to zero under the original canopy design.
John Scarano was very much troubled by the innuendo with regard to the modification and prepared a stability summary that explains how the modification was not a causal issue and this was included with the NTSB report and resolved Scarano's involvement as far as cause was concerned.
The real cause of the lack of stability of the vessel was related to an unapproved installation of the original canopy in 1969. This modification was never evaluated or approved, but the vessel retained its USCG approval and was sold for in state waters service in New York State after that. The New York State authorities accepted the USCG certification (which had never recognized the steel tube canopy installation) and the vessel operated without incident until 1989 at which time the steel tube canopy was wearing out and John designed a more attractive wooden replacement canopy.
John is a thorough professional and intimately familiar with USCG stability regulations and checked to see if his modification from the existing design would affect the stability of the vessel within the USCG requirements. That analysis is explained in this powerpoint. Bottom line, the modification would improve the stability, and the "why" requires close study of the powerpoint.
The modification was made and the vessel operated without incident until 2005, when it capsized. The capsize itself is also a mystery since the conditions that day were no different than they had been for years, but there must have been a combination of forces that just crossed the point where the limited righting energy that had been available since 1969 was reduced to zero and the vessel capsized.
These lessons all came together with a number of other small vessel capsizes that all occurred at about the same time (all of which we worked on as forensic consultants), but all capsized for different reasons.
Overall, it resulted in higher passenger weight assumptions and a USCG regulatory directive that a small passenger vessel's stability needs to be periodically evaluated. We worked with the USCG on those issues and these changes were also adopted by NY state.
Meanwhile, all the naval architects involved, me included, learned a new lesson: Always back check historic data on a vessel, and make sure it still is correct when you work on it, since hidden change can sneak up and cause harm where you least expect it. That is very difficult and even expensive, but, first of all, should remind us to be professionally paranoid.
The updated USCG regulations are an attempt to close the stability gap, but there will always be other gaps, whether fire safety, structural or operational.
Thanks for allowing us to spread the work on this lesson John.
In the words of Hill Street Blues: Let's be careful out there.
Follow us on Linked In by clicking the "Follow" button on our blog page.