kjman55 said..
About 15 years ago I did the inquest ( and the subsequent suit) into the deaths of 2 women when the bolt on keel of Rising Farrster fell off about 8 ks off Ballina in Force 1-2 conditions late at night. The boat sank without any prior warning in a matter, literally, of seconds, according to the survivors. I think 4 or 5 occupants were asleep, and 2 did not have time to get out. One of the dead was an SAS member, so they were fit! No one had time to get life jackets and the survivors had to swim maybe 15ks ( with currents) to get to shore. They were all fit and young.
The keel failed , the Coroner found, because of inadequate keel washers,compared to the floor frames as built which caused a series of calamatous failures , ultimately leading to a full peeling of the laminate as the keel,came off. I will not go into any questions of fault here, or cast any aspersions on anyone, but raise it only to show that bolt on keels rely upon a number of critical factors and that failure may be lurking unknown and unwarned without any visible signs. This keel had been flexing the hull imperceptibly in way of the floor frames, till it reached a critical failure mode in calm conditions. I no longer have the brief obviously, but I seem to recall that the failure actually sheered at least one of the bolts which was solidly anchored through a frame, and that it was a stress overload failure , not a corrosion fracture. Of course a Farr 40 is not a particularly big boat nor is the keel particularly heavy compared to some modern boats utilizing bolt on keels.
Modern composite construction often leaves little choice but to utilise a bolt on keel. Luckily failures are rare, but when they happen are catestrophic. Had there been any sea running when Rising Farrster was lost, all would surely have perished that far out.
i do not know what the answer is other than significant over-engineering. Andy Dovell said that it was then usual to allow ( this from my fading memory) well over a 200% margin of safety in design . I do apologise to Andy if my memory is wrong. The problem seems to me that issues can be lurking within a composite structure that looks perfect upon inspection, the latent failure being well within the structure. Maybe x ray-ing as they do with welds?? I dont know if that is even possible.
Just my 2 cents.
Cheers Keith.
Hi Keith.
The coroner's report is still available on the net but I can no longer find the judgment of the subsequent suit, which had more detail if I recall correctly.
The reading I did into the incident confirmed that (1) the IMS keel, which had a much higher righting moment, was fitted without the required extra frames being installed; (2) the IMS keel was later modified by the installation of about 165kg extra lead on the bottom of the bulb to increase the AVS to Cat 1 levels - but again no extra structure was installed to take these even higher loads. I don't think the latter bit got into the coroner's report.
It's not really an indicment of bolt-on keels per se. If someone had modified a long keel or an encapsulated keel in the same way there could have been a similar failure.
One example could be the loss of the Swanson 42 Miintanta in the 1998 Hobart. She had a hull leak and I'm fairly sure that the owner, an engineer, felt that it was around the area of the (encapsulated, I think) keel. Similarly, some of us here know a Top Hat that cracked around the keel badly.
I've sailed with Andy a bit. I've moved away from Sydney so haven't seen him for years but his overall opinion last time I asked was that modern boats when well designed are pretty much as safe as anything else.
Rising Farrster was one of the post '84 generation with high aspect keels and a bulb; they have a dodgy record of lost keels but there are no comparable losses of lower-aspect fin keels.