MAIB Investigating Keel Loss - Tygar

[boatboat]

A nearly new Luffe 37 called Furia also sank in the North Atlantic last year. Suspected keel failure even though it was attached to one of those steel frames like x yachts. Mitigating factor its a lightweight boat in a big storm during a race.

 

[lpdsn]

Looking at pictures of the design, it is a race boat. Twin wheels, bulb keel, light weight.
The failure happened after ten years. I expect the yacht saw harder conditions during that history?

It'll have been built under the RCD, like Cheeki Rafiki and unlike racers. I know the RCD is a bit lax on skin fittings lasting only five years but I think it requires the keel to stay on for a bit.

 

[lw395]

It'll have been built under the RCD, like Cheeki Rafiki and unlike racers. I know the RCD is a bit lax on skin fittings lasting only five years but I think it requires the keel to stay on for a bit.

To what extent does RCD define safety factor in scantlings?
We understand the processes of skin fittings lasting five years, but most people's idea of the life cyle of GRP seems to centre on it being non-degrading and how the hell to get rid of it at 50 years?...
So why would a ten year old boat break in benign conditions?

 

[lpdsn]

To what extent does RCD define safety factor in scantlings?

I believe it relies on other standards for scantlings. In fact I got the understanding that it is up to the builder to justify which standards they use rather than the RCD specifying them. If I get spare time I might try to read up on the exact details of what it says.

So why would a ten year old boat break in benign conditions?

Exactly, that's what I hope the MAIB will investigate thoroughly.

It was a F7 beat but that is within the spec for RCD A - the current Comet 41 & 45 are RCD A.

 

[lw395]

Depends. Are we talking "tennis racquet" or "glider"?

The gliders I'm most familiar with are paragliders, which are binned after so many hours, I don't think ten year old gear would be credible.
I'd best not comment on tennis bats.

 

[Tranona]

To what extent does RCD define safety factor in scantlings?

The MAIB report on CF had a large appendix discussing the scantling requirements for keel attachments in the RCD. They had recently been upgraded following further research by wolfson in Southampton uni, and based originally on the ABS rules. The first met the revised standard except in one monor area, even though it was built before the revision came into force.

Difficult to criticise either Beneteau or Farr design when both design and manufacture met or exceeded the standard although there is still the unresolved issues of in service wear and damage, particularly identifying failures and potential failures and subsequent repairs.

 

[lpdsn]

The MAIB report on CF had a large appendix discussing the scantling requirements for keel attachments in the RCD. They had recently been upgraded following further research by wolfson in Southampton uni, and based originally on the ABS rules. The first met the revised standard except in one monor area, even though it was built before the revision came into force.

Difficult to criticise either Beneteau or Farr design when both design and manufacture met or exceeded the standard although there is still the unresolved issues of in service wear and damage, particularly identifying failures and potential failures and subsequent repairs.

OK. RCD is even worse than some of the directives I've had to read for the day job. It simply says the boat has to be strong enough, with reference to the design category and the load. However going on from there to the Harmonised Standards (https://ec.europa.eu/growth/single-...ds/harmonised-standards/recreational-craft_en) this seems to be the one:

EN ISO 12215-9:2012 Small craft - Hull construction and scantlings - Part 9: Sailing craft appendages (ISO 12215-9:2012)

However that post dates the construction of the Tygar of London. It's also one of those standards that you have to buy. Anyone got a copy?

 

[Tranona]

OK. RCD is even worse than some of the directives I've had to read for the day job. It simply says the boat has to be strong enough, with reference to the design category and the load. However going on from there to the Harmonised Standards (https://ec.europa.eu/growth/single-...ds/harmonised-standards/recreational-craft_en) this seems to be the one:

EN ISO 12215-9:2012 Small craft - Hull construction and scantlings - Part 9: Sailing craft appendages (ISO 12215-9:2012)

However that post dates the construction of the Tygar of London. It's also one of those standards that you have to buy. Anyone got a copy?

The previous standard was the ABS standard.

Think you are looking for something that is not there, which is why I referred you to the MAIB report. Read that and you will be up to date and perhaps not be so critical.

You really need to read the background to causes of keel failures, and those that are published do not generally show inadequate design standards used in the RCD for production boats.

It is all too easy to rabbit on about poorly designed and built modern boats while ignoring the lack of any systemic evidence that this is the case and ignoring the fact that there have always been design and construction failures in boats, particularly intensively used racing boats.

 

[lpdsn]

The MAIB report on CF had a large appendix discussing the scantling requirements for keel attachments in the RCD. They had recently been upgraded following further research by wolfson in Southampton uni, and based originally on the ABS rules. The first met the revised standard except in one monor area, even though it was built before the revision came into force.

I've just re-read that annex with the extracts from the report from Wolfson. Interesting that in some parts the structure exceeded the minimum standard by just a few percent. Of course the standard was never there for them to conform to when CR was built (or indeed when Tygar of London was built) but the margins above the minimums seem very small when you appreciate it doesn't include fatigue or the effect of damage and 'cottage industry' repair.

Anyway, we haven't a clue why Tygar of London lost her keel. It could've been from something else entirely. We'll have to see what the MAIB says.

 

[lpdsn]

It is all too easy to rabbit on about poorly designed and built modern boats while ignoring the lack of any systemic evidence that this is the case and ignoring the fact that there have always been design and construction failures in boats, particularly intensively used racing boats.

It's also very easy to stick your head in the sand too and just blame racers etc. Clearly there is an issue. although not a big one as there are only a handful of cases worldwide each year. If wings fell off aircraft at a similar rate though they'd be doing a lot about it. As I've just said above we don't know why this particular boat lost its keel (could just be an insane crew member attacking the keel bolts with a large spanner) but I'm glad MAIB are investigating and if they find that there are conclusions that are critical to any standards then I hope they go ahead and say what they think.

 

[Skylark]

I did feel that Beneteau came out of it with very little criticism after the loss of the Cheeki Rafiki and having a bit of a bee in my bonnet about good design including design for maintainability I thought they got off lightly.

With a working lifetime in automotive engineering I’m the first to acknowledge that yacht design is not my field, that said, it seems a stretch to expect a keel to be designed for maintainability (other than a very occasional, perhaps once in a lifetime, bolt torque check). What’s to maintain in normal use? Or are you suggesting that the keel should have an inspection routine against abnormal use (grounding?). That would be pretty hard for the manufacture to make objective.

As the owner of an AWB with saildrive, I think that the builder can legitimately be criticised for poor maintainability of the seal (in my case every 5 years and almost complete removal of engine and gearbox), but surely not it’s keel arrangement.

Other than a very rare manufacturing defect, often outside the scope of maintenance, I don’t believe that there’s much evidence to support the bee in your bonnet?

 

[doug748]

It's also very easy to stick your head in the sand too and just blame racers etc. Clearly there is an issue. although not a big one as there are only a handful of cases worldwide each year. If wings fell off aircraft at a similar rate though they'd be doing a lot about it. ....

Yes they would. generally with aircraft you have:

A high degree of public interest.
Enforced maintenance schedules.
Failures rigorously examined. Manufacturers made active by statute, repairs certified and enforced through established channels.
Incidents and accidents are recorded and investigated.

All things we lack ( and probably would not want) with boats
Plus the utility and long term performance of metals has a longer history and is better understood.

To a certain extent, hull failure is the price you pay for cheap boats, in another the price paid for extra performance.
A cynic once said that engineers are very clever people but, in the final analysis, all they do is design something down till it breaks and then make it a bit stronger.
As we understand the stresses and performance of structures more completely, or at least more easily, it's possible that margins of safety are trimmed back because it looks convincing on a computer screen. Unfortunately boats are tested at sea without the controls that aircraft have.

The irony being that the eponymous man with the bucket of resin may have done a better job.

 

[Tranona]

I've just re-read that annex with the extracts from the report from Wolfson. Interesting that in some parts the structure exceeded the minimum standard by just a few percent. Of course the standard was never there for them to conform to when CR was built (or indeed when Tygar of London was built) but the margins above the minimums seem very small when you appreciate it doesn't include fatigue or the effect of damage and 'cottage industry' repair.

Anyway, we haven't a clue why Tygar of London lost her keel. It could've been from something else entirely. We'll have to see what the MAIB says.

You will find almost certainly they used the ABS standard. Rather pointless commenting on being just above minimum standard when you don't know how "high" the minimum is. Surely if as you are implying the minimum is inadequate then it should be higher.

Of course there is consideration of fatigue and the effect of damage. Plenty of boats are damaged by running aground without the keel becoming detached and are subsequently repaired. There is a danger of reading too much into one incident (which the MAIB thankfully avoided doing). Set against approx 800 boats built to the same design, the failure of one in extreme conditions following a record of misuse and poor maintenance is hardly evidence of systemic failure.

Not burying heads in sand, just taking a balanced view of the evidence. No doubt the Tygar investigation will uncover more as the hull is available for inspection and there are survivors. However, willing to bet that the causes will be unique to the particular situation and not an indicator of systemic failure.

 

[JumbleDuck]

With a working lifetime in automotive engineering I’m the first to acknowledge that yacht design is not my field, that said, it seems a stretch to expect a keel to be designed for maintainability (other than a very occasional, perhaps once in a lifetime, bolt torque check). What’s to maintain in normal use?

Is it not hull maintainability which is the issue? Yachts do run aground, and it should be possible (a) to inspect for damage (b) to find damage if there is any and (c) to repair it to at least original strength. Or, if any of these things are not possible, it should be made clear: "If any sign of pond failure between the grid and the hull is noted, the vessel should be taken out of use".

As has been pointed out, the inspection, maintenance and regulatory regimes for aircraft are very different, but aircraft manufacturers provide very clear instructions on inspection and repair and it ought to be possible for boat manufacturers to do the same. In the case of relatively highly stressed designs, built near the limit (and there is nothing wrong with that) such information should be seen as essential.

 

[Skylark]

Is it not hull maintainability which is the issue? Yachts do run aground, and it should be possible (a) to inspect for damage (b) to find damage if there is any and (c) to repair it to at least original strength. Or, if any of these things are not possible, it should be made clear: "If any sign of pond failure between the grid and the hull is noted, the vessel should be taken out of use".

As has been pointed out, the inspection, maintenance and regulatory regimes for aircraft are very different, but aircraft manufacturers provide very clear instructions on inspection and repair and it ought to be possible for boat manufacturers to do the same. In the case of relatively highly stressed designs, built near the limit (and there is nothing wrong with that) such information should be seen as essential.

No, it’s not hull maintainability, that’s why I made my comment in response to the assertion of “design for maintainability” by lpdsn.

Deriving a meaningful, objective test post grounding is something altogether different but was not mentioned by lpdsn in that post.

I don’t see the point in comparing boats to aeroplanes as they are very different things.

 

[dom]

Is it not hull maintainability which is the issue? Yachts do run aground, and it should be possible (a) to inspect for damage (b) to find damage if there is any and (c) to repair it to at least original strength. Or, if any of these things are not possible, it should be made clear: "If any sign of pond failure between the grid and the hull is noted, the vessel should be taken out of use".

As has been pointed out, the inspection, maintenance and regulatory regimes for aircraft are very different, but aircraft manufacturers provide very clear instructions on inspection and repair and it ought to be possible for boat manufacturers to do the same. In the case of relatively highly stressed designs, built near the limit (and there is nothing wrong with that) such information should be seen as essential.

Agree, maintenance is key: take for example Sunsail's SO37 Solent fleet. These vessels were routinely hammered at full-tilt into the ground, which is why the fleets are kept away from rocks. Sunsail noticed that problems were starting to appear following repeated heavy groundings. So they dropped the keels, pulled out a chunk of the inside and reinforced the structure. I have spoken with surveyors who tell me they'd happily sail a sorted one across the pond because they "know" it's strong. .

You often make comparisons to aircraft and it's not a bad one. One however wonders whether a rigorous mandatory coding schedule might be a good idea for all yachts which travel 5m or more offshore. No exceptions.

Can you imagine the howls!! So what's the solution?? For some reason, cruising sailors and club racers seem to spend hours tweaking antifoul, battery chargers, and anchors, without caring for a decent structural maintenance programme.

I've no answers though :ambivalence:

 

[lpdsn]

With a working lifetime in automotive engineering I’m the first to acknowledge that yacht design is not my field, that said, it seems a stretch to expect a keel to be designed for maintainability (other than a very occasional, perhaps once in a lifetime, bolt torque check). What’s to maintain in normal use? Or are you suggesting that the keel should have an inspection routine against abnormal use (grounding?). That would be pretty hard for the manufacture to make objective.

As the owner of an AWB with saildrive, I think that the builder can legitimately be criticised for poor maintainability of the seal (in my case every 5 years and almost complete removal of engine and gearbox), but surely not it’s keel arrangement.

Other than a very rare manufacturing defect, often outside the scope of maintenance, I don’t believe that there’s much evidence to support the bee in your bonnet?

I was halfway through an answer before I realised JD had answered it for me - my thoughts are similar to his so I wouldn't want to get hung up on different definitions of design for maintainability. CR was not a manufacturing defect. It was just very difficult to identify and reliably repair issues arising from in-service wear and tear.*

Of course you could debate till the cows come home what is an abnormal event and where the limit lies in terms of grounding, but to call all contact of a sailing yacht with the bottom an abnormal event has to be wrong. Some light groundings would have to fall into the same category as a car bumping up onto a kerb to park.

My twenty quid tether has an indicator of overload if subject to forces that would weaken it yet I could spend £200K on a new yacht tomorrow that wouldn't have an indicator of overload on the keel structure despite it being weakened and the risk of several lives being lost if it fails. Is that not bad design?

If I can answer a few other points in the same reply.

Aircraft analogies are reasonable to a certain extent. Modern yachts have foils based on the NACA series so you are getting into the realms of aircraft design in that there are wing like structures that have to be attached to the body. Obviously with aircraft the wings will come off with a heavy grounding, but based upon anecdotal evidence from someone I know who did structural repairs on commercial airliners, minor bumps and scrapes, especially with ground vehicles, are not that uncommon. Unlike boats there is a clearly defined process for identifying exactly what repair is to be carried out, based upon a history of previous repairs, and of course a process for certifying those repairs. I understand minor ones are carried out as part of the maintenance schedule.

Regarding Tranona's points. I'd be very wary of rationalising this away. Clearly boats are strong enough when they come out of the factory, a few manufacturing and design defects aside, but a small number of keels are being lost in open water, whatever the cause, and these incidents are continuing. Of course with such a small number there will be differing causes and trends will be harder to identify, but continuing to dismiss them as misuse, or just racers, or similar, risks going down the same path they went down with the Comet.

*There were hints in on another thread from a newbie poster that CR had suffered a heavier grounding than the MAIB were aware of but the poster was reluctant to come back with details - presumably he was worried about getting dragged into a court case.

 

[JumbleDuck]

No, it’s not hull maintainability, that’s why I made my comment in response to the assertion of “design for maintainability” by lpdsn.

Was it not suggested that the hull-matrix join in Cheeky Rafiki (a) may have been damaged in an accident (b) was very difficult to inspect and (c) would have been very difficult to repair. That seems to put hull maintainability at the very heart of the matter. With the exception of that Dutch yacht, keels themselves don't seem to break much.

I don’t see the point in comparing boats to aeroplanes as they are very different things.

Not perhaps as dissimilar as you might think. A modern composite aircraft or glider has a stressed skin construction to which the high local loads of wings, tail and undercarriage must be transmitted; a modern composite yacht has a stressed skin construction to which the high local loads of mast, rudder and keel must be transmitted. I hope we never have the sort of regulation in sailing which the flying world accepts, but yacht manufacturers might have something to learn from the inspection and maintenance regimes used by aircraft manufacturers. In fact, I believe that there already are moves in that direction.

 

[JumbleDuck]

You often make comparisons to aircraft ...

Sorry about that. I took about 15 years away from (much) sailing to fly gliders, and I found comparisons between the two activities interesting. There is a lot of overlap - almost all glider pilots I know/knew also sail. The biggest personal change I found was in my approach to inspection and maintenance. It generally doesn't matter too much on a boat, but a missing split pin can very easily kill you in a glider and when I came back to sailing I found myself almost automatically making daily inspections and sorting stuff now.

Oops. I've done it again.

 

[Tranona]

Regarding Tranona's points. I'd be very wary of rationalising this away. Clearly boats are strong enough when they come out of the factory, a few manufacturing and design defects aside, but a small number of keels are being lost in open water, whatever the cause, and these incidents are continuing. Of course with such a small number there will be differing causes and trends will be harder to identify, but continuing to dismiss them as misuse, or just racers, or similar, risks going down the same path they went down with the Comet.

.

I am not dismissing them. That is why I use the term systemic. If you are trying to claim that there is a failure in design and manufacture then that is systemic, and in that case you would see commonalities in the causes of failure. So far the main commonality (particularly if you read the full ISAF report) is GROUNDING, closely followed by the boats also being involved in racing. So, ignoring those two factors is indeed putting your head in the sand.

It is perfectly possible to build more robust keels and supporting structures as Swedish builders (among others) have demonstrated but it invariably involves a performance penalty. Those looking for performance advantages have to accept the compromises or suffer the performance penalty. One way of resolving this with racing boats and particularly dual purpose boats like the First is change the rules to either reward more robust keels or penalise what might be considered less robust. Not sure that would go down well with owners, designers or builders!

So far there has been sufficient explanation of the small number of keel losses on production cruising boats and none of these suggest a serious systemic issue in design or manufacture. This does not mean as you say that there are not issues in using these boats, but they are very firmly the responsibility of owners - that is the way the boats are used, maintained and repaired if damaged. I recognise that grid reinforcing structures present new potential problems, but that does not mean that previous methods were trouble free as many owners of some well known boats will testify.

The reality is that you are never going to eliminate failures, but I would suggest that the vast majority of boat owners will never experience problems with the keels on their boats.