Cheeki Rafiki loss report

[Exile]

Originally Posted by Polux

I don't understand what you want to highlight about the boat maintenance. The conclusions state that there is a need of a protocol for inspections and repairs and that's true but on the report it is said also that the boat grounded 5 times, that there is no reports of inspections on some of those groundings and say that the surveyors, when the boat was officially inspected for commercial coding found a matrix detachement and that the boat was not surveyed again (as it should) to see if it was repaired because they took a loophole, coding the boat very low, avoiding further inspections. I wonder why?

All that is on the report.

Agreed. But as the report explained, five prior groundings with a boat used this long for charter racing is hardly unusual. Nor is the failure to follow through with proper procedure with an out of the water survey following repairs, sorry to say. It shouldn't happen, but of course it does, and it's certainly not beyond the realm of what's reasonably foreseeable when engineering a boat. Regardless, the report never conclusively determined after a lengthy investigation and analysis, as your mysterious surveyor did from one photo alone, that the maintenance to repair these five groundings had been negligent. As transmitterdam responded when you first introduced this surveyor's "evidence" into this thread:

I don't know how he can say someone was negligent or if he knows who it is. But his opinion as to the proximate cause of the failure seems to be based solely on the examination of the picture. The MAIB investigation did a lot more work than that. In terms of the technical reason for keel loss the report and the surveyor seem to agree. Although, the surveyor just thinks it was loose keel bolts. But why were they loose? The MAIB report seems to answer that question. The liner/hull adhesive bond failed allowing the keel side loads to increase dramatically the pressure on hull. The liner is supposed to spread the keel load out. But it has to be bonded to the hull for that to work. As soon as the bond is broken the pressure moves to right where the keel bolts are.

There is also the opinion of another surveyor that stated clearly that the boat was not on a seaworthy condition (keel bolts lose) and that the maintenance was negligent.

Again, based on one photo and the communications concerning water ingress from the skipper. What could this surveyor you quoted possibly have known about the maintenance history of this sailboat that the MAIB inspectors failed to uncover after a year-long investigation??

Do you mind to explain to me why after all this evidence do you think that the boat was in an adequate state of maintenance?

If you mean a boat that apparently checked out visibly when dived on in Antigua but then lost its keel a week later after hitting heavy seas? No, I'd say that boat was definitely "not in an adequate state of maintenance!" But the report could only say that the quality of the prior maintenance, the groundings, the design & construction, the heavy seas, etc., were all possible factors in the boat's demise. Nowhere in the report does it state that negligent maintenance had been conclusively uncovered, let alone that this is what caused the keel to fail.

That is what we are discussing. Someone stated that the boat was well maintained and that was to that that I replied saying that it was not and explaining why, not with my opinion but with the opinion of a surveyor and with facts that are on the report.

The point is that, based on the factual record analyzed in the report, it is incorrect to attribute the blame solely to negligent maintenance as your surveyor did (and you seem to be interested in doing now), and it is equally incorrect to conclude that the boat had been well-maintained. Apparently it's yet another sub-topic you feel obliged to argue about for the sake of . . . well . . . argument, but unless additional facts come out -- perhaps through an insurance investigation and/or private lawsuit -- it's one we're likely to never know. If you disagree, then please quote that portion of the report that makes this conclusion, and explain why this mysterious surveyor of yours appears to have more facts than the inspectors from MAIB!

[malbert73]

To answer the question, bolt on lead is probably best because a hard grounding (assuming the keel is low enough aspect and well bolted like most quality cruisers) will be absorbed by deformation of the soft lead, which can easily be hammered and faired back to shape. Encapsulated keels eliminate the bolt issue, but water ingress into the ballast can happen with a hard grounding that damages the fiberglass shell. Most encapsulated ballast has some voids around it so water can collect. If it's lead, it won't rust. Some builders take shortcuts and encapsulate iron which will rust.
Bolt on iron will transmit all shock loads of a rock/hard grounding to the hull. It's much less dense than lead. It rusts. it's cheaper. Has no redeeming qualities for a keel except that it's cheap and strong. Love watching folks try to beat back the rust year after year in spring commissioning. Oh wait, scratch that since we're supposed to buy new and discard after 5-7 years for latest and greatest.


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[downunder]

Originally Posted by donradcliffe

The First 456 does have an internal matrix, but it is tabbed onto the hull and separation is pretty detectable. On one hand the F456 layup is probably 25 mm thick at the keel, bu ton the other hand the factory keel bolts are only backed with simple fender washers--not nearly as substantial as in the 40.7. I know of one 456 which had keel problems (grounding in a hurricane), and it was repaired with much more substantial backing plates.

I've been trying to figure out how the cheeky Rafiki keel attachment failed so suddenly. We will probably never know for sure, but the MAIB report seems to point toward the shearing failure of the two forward and one aft centerline keel bolts. From the rust stains, it may have been that the aft keel bolt was corroded and was the first to fail--perhaps well before the incident. This put more load on the forward centerline bolts leading to their fatigue failure. AFTER the 3 bolts had sheared, the remaining structure was not up to the task, as the remaining keel bolts and backing plates tore through the laminate structure.

There is a lot of MAIB discussion of groundings and the detachment of the stiffening matrix from the hull. However, it is not at all clear to me how that detachment lead to the failure of the centerline keel boats, especially as the keel boats clamp the matrix and hull together in that area.

A grounding at hull speed is going to put more stress on the forward keel boats, while the aft bolt is going to have less stress, or even be in compression. Yet it was the aft bolt which showed signs of corrosion, probably due to the failure of the sealant around the bolt in some much earlier incident.

A contributing cause to the sudden detachment was the skipper's decision to keep driving the boat hard after the water started coming in. With 20-20 hindsight, if he had cut the sail area and run with the wind and sea, he might have had enough time to declare a Mayday and get rescued.

After seeing the aftermath of a hard grounding in a modern Bene I think the builder's shortcut of gluing the matrix to the hull results in a 'throwaway' boat, as the repair costs came close to the value of a 6 month-old boat.

This is my takeaway.

After seeing the aftermath of a hard grounding in a modern Bene I think the builder's shortcut of gluing the matrix to the hull results in a 'throwaway' boat, as the repair costs came close to the value of a 6 month-old boat.

[neilpride]

Originally Posted by Exile

I was planning on asking Minaret this myself, but then thought I may not wanna hear the answer. I would hazard a guess that not many fall off catastrophically, but it would be useful to know what sorts of problems one can or should anticipate. I suspect to hear about fewer problems with lead vs. iron, but maybe Minaret will respond. Also curious about his opinion that (properly) bolted-on lead is best.

What seems most relevant to the thread discussion, of course, is that properly bolted-on keel structures seem to enjoy a good reputation generally, a fact which, if true, only makes the CR incident that much more bothersome. IMHO, that is . . . .

No idea Minaret, but i never see a encapsulated keel falling off from a hull, they suffer some short of problems to, but it really depend of the quality and if they take care of recent groundings in time, lead is for me the best stuff you can pour in a keel mold, iron cement and other raw crap is the worst thing you can found in some vintage boats, the thicknes laminate around the keel,keel shoe is normally thick, groundings and collisions can break the hull laminate and allow wáter to found a path between voids in the laminate , if the repair dont respect drying times sometimes is glassed back with wáter inside , and we know what happen with iron and sea wáter in a encapsulated enviroment, another place for wáter to found a path inside of the mold is by the bilge, cracks mostly,,,,

Most encapsulated keels boats are made by 2 hull molds or 2 halfs joined together after the hulls lay up are finished , since glassing the bottom of the keel molds in a single mold hull is really hard to do it properly, the halves are glassed at the joint after when the 2 pieces are joined together ..inside and outside...

Also there is a rare ways to built a encapsulated keel like my CSY 44, they make the keel in 2 steps , or kind to have 2 keels in the same mold, the bottom of the keel is cement encapsulated in more than 2 inches of FG, then this is glassed over the top with a solid 2 inches of glass to , over this laminate rest lead ingots mixed with resin and they glass it again in the top to with solid laminate... overkill... but so far so good to me the best way is lead bolted to a solid structure,,, lead and nothing else, they absorb impacts, groundings, the structure take care of the rest, and they dont collect wáter inside ,,,if they are troughbolted to solid members much better...and with enough bolts and well spaced ...

Iron is for me a hull killer, since iron is tough and dont absorb impacts or groundings like lead, the aft trailing edge in a iron keel is like a knife , ready to slice the structure in a serious grounding, also rust and corrosión are a isue....

Lead troughbolted is by far the best compromise in a production boat...

[minaret]

Originally Posted by Exile

I was planning on asking Minaret this myself, but then thought I may not wanna hear the answer. I would hazard a guess that not many fall off catastrophically, but it would be useful to know what sorts of problems one can or should anticipate. I suspect to hear about fewer problems with lead vs. iron, but maybe Minaret will respond. Also curious about his opinion that (properly) bolted-on lead is best.

What seems most relevant to the thread discussion, of course, is that properly bolted-on keel structures seem to enjoy a good reputation generally, a fact which, if true, only makes the CR incident that much more bothersome. IMHO, that is . . . .

Malbert and Neil seem to have covered most of the salient points. I'll just add that despite torquing a lot of keel bolts, sistering bolts, and replacing bolts on bolt on lead keels, I have seen far more long term damage and expense in integral ballast keels. Aside from the issue of being far more expensive to repair in the case of a grounding, the damage is often more extensive. Lead is super fast and easy to fair-glassing the bottom of a keel not so much. I've seen lead ballast keels absorb amazing damage without affecting the bolts, keel stub, or hull structure at all. Another point would be that the nature of a lead ballast requires a more substantial design. And cast iron keels of all sorts are a nightmare to maintain. They just rust no matter what you do. Also seen a lot of problems with water ingress into internal ballast leading to rust scale/swelling of the ballast, causing the keel to crack at the centerline laminate. This can be caused by freezing of water in the keel in boats on the hard too. Seen all sorts of weird internal ballast; boiler punchings, bricks, all kinds of strange stuff. Give me lead any day.

[leftbrainstuff]

Originally Posted by Polux

That contradicts the analyses a reputable surveyor has made (he talked about negligence) and contradicts also what the MAIB report says about Cheeki Rafiki maintenance. Why do you say that? Based on what?

From memory the loss report didn't indicate the vessel was poorly maintained. It did highlight keel maintenance was not adequate.

I've read several loss reports lately so apologies if I've misquoted. I'm travelling and dont have access to the report just now.

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[Exile]

Hmmm . . . twice now after hauling out I've drilled a small hole on the aft bottom end of my keel and both times had water dribbling out. Encapsulated lead, with the only logical (to me) source where the rudder post enters. Hard to imagine but possible I suppose that it's coming from above, namely the deep bilge where all water drains down into. Shouldn't drift too far here . . . maybe best to start a different thread.

Anyway, thanks for all the replies to questions about encapsulated vs. bolt-on keels. Assuming it's done properly, it sounds like bolt-on (lead) is clearly an overall improvement maintenance-wise, has good performance benefits, and may in fact be less expensive for a builder to produce. Also instructive were Neil's photos awhile back showing a bolt-on keel prior to installation on a Bob Perry-designed boat. Very telling, even to a layman. Your comments also bring to mind a posting from Dockhead in another thread about hitting an uncharted submerged rock at speed in his Moody 54. He said they hit so hard that the entire bow came out of the water, but there was no immediate or long-term damage (he hauled out & surveyed) to his bolted-on keel.

I, for one, find this discussion directly relevant to CR's loss report. It only highlights how off-base it is to assume the problem may lie with bolted-on keels generally, just like failed rudders have little to do with the overall integrity of a spade rudder vs. other type of design. In all cases it comes down to choice of materials & quality of construction. Of course maintenance plays a critical role, assuming the design is maintainable to begin with that is!

Thanks again for taking the time to respond.

[minaret]

Try reading the latest Professional BoatBuilder issue, "Shearography in the Expanded Frame" article, to learn more about modern methods of NDT and boats. They are using laser shearography with a new method of stressing, called dynamic excitation, to allow much larger screen captures. They just went from over 10k images required to NDT a 100' hull to 240 images required. Of course, at that resolution you can't find defects smaller than about 20mm. Much is discussed in this article that has been mentioned here, including a fair bit of info about thermography and ultrasound (which is described as fairly useless due to the extremely small image size).


Professional BoatBuilder - #155 PBB June/July 2015


Table of Contents 155 - Professional BoatBuilder Magazine



http://www.shipstructure.org/proj/ya...licability.xls



Shearography - Wikipedia, the free encyclopedia

[Polux]

Not related with the First 40.7 but related with the lose keel bolts that seem to have played an important part on the keel loss.

Yesterday the bolt keels of my boat were tightened. The boat has 8 years, I owned it for 4 years and I don't know if they had been tighten before. At the same time the keel bolts of a sister ship of about the same age were tighten too (this one used in hard racing).

Both boats showed exactly the same behavior being all bolts tightened in about 3/4 of a turn. They have huge backing plates and big nuts with a two nuts system to prevent becoming lose.

Probably with time and effort a small compression of the fiberglass had occurred in an uniform way and that is consistent with all bolts having the same 3/4 of turn tightening on both boats.

Probably this will occur in all boats with a similar bolted keel and just confirms the importance of checking the keel bolts regularly and always before an ocean crossing.

[minaret]

Originally Posted by Polux

Not related with the First 40.7 but related with the lose keel bolts that seem to have played an important part on the keel loss.

Yesterday the bolt keels of my boat were tightened. The boat has 8 years, I owned it for 4 years and I don't know if they had been tighten before. At the same time the keel bolts of a sister ship of about the same age were tighten too (this one used in hard racing).

Both boats showed exactly the same behavior being all bolts tightened in about 3/4 of a turn. They have huge backing plates and big nuts with a two nuts system to prevent becoming lose.

Probably with time and effort a small compression of the fiberglass had occurred in an uniform way and that is consistent with all bolts having the same 3/4 of turn tightening on both boats.

Probably this will occur in all boats with a similar bolted keel and just confirms the importance of checking the keel bolts regularly and always before an ocean crossing.

More likely the builder simply torqued to a different spec. Probably they torqued to the lubricated rating and your yard torqued to the dry rating. 3/4 turn is quite a bit.

[Polux]

Originally Posted by minaret

More likely the builder simply torqued to a different spec. Probably they torqued to the lubricated rating and your yard torqued to the dry rating. 3/4 turn is quite a bit.

I doubt since my shipyard is the official shipyard from the brand and the guys that work there are the same that built the boats. Maybe it was just half a turn, dificult to say with the bigger lever harm that was used and the small movements but they certainly found that normal (I asked) as they found normal the need to verify keel bolts from time to time.

[mstrebe]

This is similar with aluminum, which will compact under compression and need a follow-on torquing of bolts after a year or so from new. Periodic retorquing is a good measure and should probably be done at every haul-out. Steel seems to spring back from compression and not require retorquing, at least in other fields.


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[Muckle Flugga]

Originally Posted by Polux

Not related with the First 40.7 but related with the lose keel bolts that seem to have played an important part on the keel loss.

Yesterday the bolt keels of my boat were tightened. The boat has 8 years, I owned it for 4 years and I don't know if they had been tighten before. At the same time the keel bolts of a sister ship of about the same age were tighten too (this one used in hard racing).

Both boats showed exactly the same behavior being all bolts tightened in about 3/4 of a turn. They have huge backing plates and big nuts with a two nuts system to prevent becoming lose.

Probably with time and effort a small compression of the fiberglass had occurred in an uniform way and that is consistent with all bolts having the same 3/4 of turn tightening on both boats.

Probably this will occur in all boats with a similar bolted keel and just confirms the importance of checking the keel bolts regularly and always before an ocean crossing.

All showing the same behaviour is likely a good thing. As is "huge" backing plates. Glad all seems well with your craft. Well done for due diligence.

[leftbrainstuff]

Originally Posted by Exile

Hmmm . . . twice now after hauling out I've drilled a small hole on the aft bottom end of my keel and both times had water dribbling out. Encapsulated lead, with the only logical (to me) source where the rudder post enters. Hard to imagine but possible I suppose that it's coming from above, namely the deep bilge where all water drains down into. Shouldn't drift too far here . . . maybe best to start a different thread.

Anyway, thanks for all the replies to questions about encapsulated vs. bolt-on keels. Assuming it's done properly, it sounds like bolt-on (lead) is clearly an overall improvement maintenance-wise, has good performance benefits, and may in fact be less expensive for a builder to produce. Also instructive were Neil's photos awhile back showing a bolt-on keel prior to installation on a Bob Perry-designed boat. Very telling, even to a layman. Your comments also bring to mind a posting from Dockhead in another thread about hitting an uncharted submerged rock at speed in his Moody 54. He said they hit so hard that the entire bow came out of the water, but there was no immediate or long-term damage (he hauled out & surveyed) to his bolted-on keel.

I, for one, find this discussion directly relevant to CR's loss report. It only highlights how off-base it is to assume the problem may lie with bolted-on keels generally, just like failed rudders have little to do with the overall integrity of a spade rudder vs. other type of design. In all cases it comes down to choice of materials & quality of construction. Of course maintenance plays a critical role, assuming the design is maintainable to begin with that is!

Thanks again for taking the time to respond.

As an engineer I don't share your enthusiasm for bolt on keels.

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[Exile]

Originally Posted by leftbrainstuff

As an engineer I don't share your enthusiasm for bolt on keels.

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Still not enthusiastic about it for my own boat, just recognizing that it doesn't seem to constitute a faulty design per se, but rather one that seems to be generally accepted if built properly. I am not an engineer, but it seems logical that basic design/engineering standards should contemplate a certain number of light groundings and perhaps less than ideal maintenance intervals as factors that are reasonably foreseeable in an ocean going yacht. Some may call this "over-engineering," but it seems logical that if you cannot reasonably estimate the foreseeable stress on a structure, then you must engineer acceptable margins to a level "x" number of times beyond what you can estimate, particularly if failure could mean loss of life. I'm sure you guys have terminology for this.