Another Keel Failure

[Joker]

I had my rudder rebuilt in Southampton. They fabricated a new rudder stock by using a stainless steel pipe, and welding a stainless steel bar onto it. The tangs were attached to the bar. The weld was about 12 inches into the rudder.

One day it failed on me, and the rudder folded through 90°, which was not very helpful.

Later examination showed that it had been corroding for some time – in other words was no clean shiny metal visible at the break.

I have the feeling that welds underwater are not a good idea.

 

[Triassic]

Guys, it's a race boat, you expect to break things. If things don't break then they are either to big, to thick, to heavy etc etc...
Racing is all about pushing margins, both in terms of design and construction. The important thing to remember is just that when sailing and to have plans in place to deal with failures. As somebody pointed out nobody was hurt in this incident, it's just another step in learning what works, or doesn't......

 

[flaming]

Guys, it's a race boat, you expect to break things. If things don't break then they are either to big, to thick, to heavy etc etc...
Racing is all about pushing margins, both in terms of design and construction. The important thing to remember is just that when sailing and to have plans in place to deal with failures. As somebody pointed out nobody was hurt in this incident, it's just another step in learning what works, or doesn't......

Absolutely not. Keels are not supposed to break.

 

[lw395]

Absolutely not. Keels are not supposed to break.

Neither are masts supposed to fall down, sails to rip, blocks to wear out, oilskins to leak ......

 

[flaming]

Neither are masts supposed to fall down, sails to rip, blocks to wear out, oilskins to leak ......

Masts I can just about accept as an occasional failure, and there is normally a reason. The rest is small.

But keels? No, absolutely not. We cannot as sailors get to a place where we accept that keels falling off is in any way shape or form normal or acceptable.

 

[lw395]

Masts I can just about accept as an occasional failure, and there is normally a reason. The rest is small.

But keels? No, absolutely not. We cannot as sailors get to a place where we accept that keels falling off is in any way shape or form normal or acceptable.

Depends what you mean by normal.
IT's not exactly an everyday occurrence in club racing is it?
A keel falls off in an extreme race on the other side of the world and it makes the news here.

If racing boats never pushed the boundaries, we'd all be stuck racing Contessa 32s or something.

 

[flaming]

Depends what you mean by normal.
IT's not exactly an everyday occurrence in club racing is it?
A keel falls off in an extreme race on the other side of the world and it makes the news here.

If racing boats never pushed the boundaries, we'd all be stuck racing Contessa 32s or something.

A Ker 40 is not an extreme race boat. And it was on a delivery at the time.

I agree entirely that boundries should be pushed, but this was not a keel that had done a load of miles, it was a replacement keel on a relatively new boat that sought a bit extra performance.

Zero excuses for it failing in normal use.

 

[Triassic]

Flaming, I'm not trying to imply that a keel falling off is acceptable. What I am saying is that competition drives people to push limits, both in design and application, so the risk of a failure, any failure, is much higher in competition. Obviously it would be nice if people only pushed limits that have small consequences if they didn't work, however that isn't the nature of the beast is it.

If this is relatively new boat why did it need a replacement keel? Now I admit I'm only speculating here but I suspect the person who instigated the idea of fitting it didn't do it with the intention of increasing the risk of it falling off, they more likely did it because they thought it would improve performance in some way. Now the original designers of this boat are not fools but with any production boat there is an element of redundancy to provide a safety bubble. This is because the manufactures have a reputation and business to protect, but an individual owner may not be so concerned about that. They are more prepared to sail closer to the edge so to speak and I don't see a problem with that provided those involved know the risks involved and take reasonable steps to mitigate a failure.

 

[Zing]

Welds are relied on in many structures for safety. Most ships are held together by welds, but I agree there is added risk with a weld and if you can do it a different way, then, especially where safety is hanging on it then don’t weld.

Was it a stainless keel? If so, double trouble. Stainless is really hard to weld well and is particularly vulnerable in sea water.

 

[flaming]

If this is relatively new boat why did it need a replacement keel? Now I admit I'm only speculating here but I suspect the person who instigated the idea of fitting it didn't do it with the intention of increasing the risk of it falling off, they more likely did it because they thought it would improve performance in some way.

Yes, they went searching for more performance, a lighter bulb on a longer keel.

Now the original designers of this boat are not fools but with any production boat there is an element of redundancy to provide a safety bubble. This is because the manufactures have a reputation and business to protect, but an individual owner may not be so concerned about that. They are more prepared to sail closer to the edge so to speak and I don't see a problem with that provided those involved know the risks involved and take reasonable steps to mitigate a failure.

Amazingly, in the immediate aftermath of the incident the owner appeared on sailing Anarchy to berate Ker, initially claiming that the internal structure had failed and that his keel designer knew what he was doing, and there was no chance that the keel had failed, so it must have been the structure of the boat.
It has since emerged that Ker quoted for the redesign of the keel (which would not have included welds) but was deemed too expensive. And that the boat structure was not damaged (crew testimony) but the keel broke flush with the hull.
I think it would be fair to put that reaction down to the shock of losing his boat, and perhaps some aspect of denial that the bit he was responsible for (hiring a designer and builder to fit a new keel to a secondhand boat) could be at fault.

And on the face of it, he didn't really do anything wrong, he hired a well known designer and manufacturer for his new keel. But the keel fell off. And when it did, the original designer said "well, I wouldn't have designed it like that".
I know who I'd be going to for a new keel...

 

[DJE]

Submarine hulls and nuclear reactor pressure vessels contain welds at pretty critical locations and don't fail. The difference is that the engineering team designing the welds, carrying them out, and inspecting them are well versed in the strengths and weaknesses of welding. So a great deal of care is taken to check the design, choose the correct materials, and ensure the skill of the welders. I wonder how well this approach transfers into the boat building environment.

 

[lw395]

Submarine hulls and nuclear reactor pressure vessels contain welds at pretty critical locations and don't fail. The difference is that the engineering team designing the welds, carrying them out, and inspecting them are well versed in the strengths and weaknesses of welding. So a great deal of care is taken to check the design, choose the correct materials, and ensure the skill of the welders. I wonder how well this approach transfers into the boat building environment.

Likewise in many other structures.
Part of the skill of the designer is to design what the builders can build.
Designing something which is strong enough if it's built in a lab or aerospace facility doesn't cut it when you know it's going to be fabricated in a damp shed.

But the keel survived the race, it's not as if it fell off the first time it was exposed to its design loads.

I assume the boat has been recovered?

 

[DJE]

Designing something which is strong enough if it's built in a lab or aerospace facility doesn't cut it when you know it's going to be fabricated in a damp shed.

But the keel survived the race, it's not as if it fell off the first time it was exposed to its design loads.

Agree entirely about designing to suit the available skills. But the design should state the required standard of welding and if the fabricator can't achieve that standard he shouldn't quote for the work. The failure was likely the result of fatigue and if so it wouldn't fail the first time it was exposed to high stress but cracks would slowly grow due to the oscillating load applied by the waves. And poor weld quality often leads to poor fatigue resistance.

 

[rgarside]

Try looking at the Hooligan V report:
Keel failure and capsize of sailing yacht Hooligan V with loss of 1 life

Sounds like the Showtime keel ended up with similarly poor detailing.

 

[Birdseye]

Absolutely not. Keels are not supposed to break.

Both you and Triassic are right. He follows the Colin Chapman approach of pushing things to the absolute limit, but as you say in effect, you shouldnt push over the limit.

I spent a significant part of my working life in the special steels industry where we made components for jet engines , nuclear reactors, big pressure vessels , guns and pockets out of all sorts of materials from high nickel alloys through to stainless steels and titanium alloys. Components were welded as routine because welding properly done is no less strong than the parent metal on either side. Likely the last plane you flew in had some of our welded compnents in critical locations.

Seems clear to me that this failure was either a keel subjected to more than its design stress in which case was it the Chapman philosophy gone too far / bad design. Alternatively it was badly made and the weld wasnt x rayed and tested to ensure quality. Two statements of the bleeding obvious but until you can get a detailed examination you will never know which. But certainly welding a keel, properly done, is no issue at all.

 

[lw395]

Both you and Triassic are right. He follows the Colin Chapman approach of pushing things to the absolute limit, but as you say in effect, you shouldnt push over the limit.

I spent a significant part of my working life in the special steels industry where we made components for jet engines , nuclear reactors, big pressure vessels , guns and pockets out of all sorts of materials from high nickel alloys through to stainless steels and titanium alloys. Components were welded as routine because welding properly done is no less strong than the parent metal on either side. Likely the last plane you flew in had some of our welded compnents in critical locations.

Seems clear to me that this failure was either a keel subjected to more than its design stress in which case was it the Chapman philosophy gone too far / bad design. Alternatively it was badly made and the weld wasnt x rayed and tested to ensure quality. Two statements of the bleeding obvious but until you can get a detailed examination you will never know which. But certainly welding a keel, properly done, is no issue at all.

Things often turn out to be way more complicated than 'the bleeding obvious'.

 

[duncan99210]

Having looked through this thread and read the linked report from the designer, it sounds to me that it’s not welding per se that lies at the heart of this failure. Rather it is the design of the replacement keel which was done as a cheap option, possibly without the benefit of the full design calculations made by the original builder. That, to me, screams inadequate design where probably perfectly sound welds were stressed beyond their failure limits because the loads imposed on them.
It may also be nothing to do with weld failures but with metal fatigue acting on the horizontal/vertical join between the fixing plate and the keel itself.
It’ll be interesting to see the eventual Aussie equivalent of the MAIB report in due course, which should examine the original design, the planned modification and how the modified keel was eventually made.

 

[bbg]

Having looked through this thread and read the linked report from the designer, it sounds to me that it’s not welding per se that lies at the heart of this failure. Rather it is the design of the replacement keel which was done as a cheap option, possibly without the benefit of the full design calculations made by the original builder. That, to me, screams inadequate design where probably perfectly sound welds were stressed beyond their failure limits because the loads imposed on them.
It may also be nothing to do with weld failures but with metal fatigue acting on the horizontal/vertical join between the fixing plate and the keel itself.
It’ll be interesting to see the eventual Aussie equivalent of the MAIB report in due course, which should examine the original design, the planned modification and how the modified keel was eventually made.

It is a huge assumption that this is a design issue rather than a fabrication / manufacturing issue.

 

[flaming]

It is a huge assumption that this is a design issue rather than a fabrication / manufacturing issue.

Boat has been found and salvaged, so I suspect we will find out in due course...

 

[savageseadog]

Yes, they went searching for more performance, a lighter bulb on a longer keel.


Amazingly, in the immediate aftermath of the incident the owner appeared on sailing Anarchy to berate Ker, initially claiming that the internal structure had failed and that his keel designer knew what he was doing, and there was no chance that the keel had failed, so it must have been the structure of the boat.
It has since emerged that Ker quoted for the redesign of the keel (which would not have included welds) but was deemed too expensive. And that the boat structure was not damaged (crew testimony) but the keel broke flush with the hull.
I think it would be fair to put that reaction down to the shock of losing his boat, and perhaps some aspect of denial that the bit he was responsible for (hiring a designer and builder to fit a new keel to a secondhand boat) could be at fault.

And on the face of it, he didn't really do anything wrong, he hired a well known designer and manufacturer for his new keel. But the keel fell off. And when it did, the original designer said "well, I wouldn't have designed it like that".
I know who I'd be going to for a new keel...

Interestingly It's not the first fairly new Ker designed yacht to have had a replacement keel. I am aware that Software Mistress a Ker 36 went through at least one keel iteration. When it was bought by a new owner it came with a spare keel of different design! I understand the replacement was intended to increase performance, nothing to do with structural issues as far as I know.