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Old 02-12-2015, 06:47   #226
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Re: Oyster Problems?

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Originally Posted by four winds View Post
. . . .

Also on the russian article there is a diagram of the hull in section showing the elements of the hull, with red arrows describing the forces involved. Also some curious points marked and labelled in Russian describing the failure I think.

Wish I could read the label's but it seems to be suggesting failure of the hull laminate.
Not the whole Russian text is shown in the clip, but here's what is shown:

At the upper aft corner of the keel, red text: "Line of tearing off of the cladding" I think by cladding ("obshivka") is meant the outer skin of the hull, and they are indicating the dotted red line.

A red dot mid-way down the aft edge of the keel, with the label: "place of discovery of the first problems."

Then, at the lower right corner of the clip, is this text:

"Apparently, the vertical brackets failed first, not holding up under the loads from the keel. The fin lost strength in the vertical direction, between this and the bulb a gap appeared, and the whole mass of the ballast keel started to hang just from the outer skin of the hull."


So I guess what that means is that the hull outer skin was not intended to take the loads from the keel, and ripped out not because of a problem with the bonding (as speculated in posts above), but because of failure of the structural brackets first.

I'm neither engineer nor boatbuilder, but what they are calling "brackets" -- shown as 5mm (!) thick in the Russian drawing, sure don't look anywhere nearly up to the job, to my unqualified eye.
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Old 02-12-2015, 07:05   #227
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Re: Oyster Problems?

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Originally Posted by four winds View Post
Actually it looks to me like the failure occurred at the innermost layers of the laminates of the hull. And not at the hull to grid bond.
On the Russian article there is a picture when just lifted from the water. The large area of damage below the water shows few open holes to the inside. Mostly three long holes down low. Then a later photo shows many holes, having exposed the inside through almost every opening in the grid structure.

So it seems to me the inner layers of the hull stayed bonded to the grid , then were later on the hard poked and broken away between the grid members.

Hull laminate failure, not grid to hull bond failure, maybe?

Also on the russian article there is a diagram of the hull in section showing the elements of the hull, with red arrows describing the forces involved. Also some curious points marked and labelled in Russian describing the failure I think.

Wish I could read the label's but it seems to be suggesting failure of the hull laminate.
The hull laminate was one of the things that was holding the stub to the hull, being the other the extension of the boat keel structure below, the one that is shown on the last photo. There was also a big single bolt and for what I have understood the boat had already problems on the connection of the stub with the rest of the keel.

That lonely bolt could not maintain alone the stub and the keel with the ballast together (that bolt was one of the parts that was not recovered). An important role regarding that support was on the laminate of the hull and laminate of the part of the keel structure that went down (photo).

It seems one of the parts that failed was the stub itself and as the stub is part of the hull (meaning that is contained on the hull laminate) when the stub failed laterally and fall, it peeled with it a considerable part of the hull.

So in the end yes, that part of the laminate (and its probable inappropriate thickness), including the hull laminate seem to have had a big role on the accident, as it was stated by an independent surveyor that actually saw the boat.
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Old 02-12-2015, 07:19   #228
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Re: Oyster Problems?

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Originally Posted by poiu View Post
Not so with buildings in the UK and I believe the US, there is no assumption of what is going on; it is verified continually. Local government inspectors or independent controllers will visit often during the build to check that it is being built according to the design and regulations and will stop the job from continuing if it isn't.
..
I don't know if that is being made like that in the US but that seems crazy to me, specially in a country that considers Europe a nanny kind of state.

Can you imagine the costs that represent? You have not only any building followed by the responsible technician for the works, but also for a state technician that assures that the responsible is doing his job correctly????

Who is going to pay that?

I work on the sector being responsible for designs and working directly with the engineers that take the responsibility for the building to be conform with the designs, including structural ones and I don't know of any country where a state engineer follows the works.

Sure in the end there is (depending on countries) an inspection but that inspection regards architectural conformity more than anything being impossible to determine if the right amount of steel was put on the concrete and if the hidden structures (by walls) conform with what was projected.
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Old 02-12-2015, 07:45   #229
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Re: Oyster Problems?

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Originally Posted by Polux View Post
I don't know if that is being made like that in the US but that seems crazy to me, specially in a country that considers Europe a nanny kind of state.

Can you imagine the costs that represent? You have not only any building followed by the responsible technician for the works, but also for a state technician that assures that the responsible is doing his job correctly????

Who is going to pay that?
In the US that is how it works. The taxpayers pay for the building inspectors and the builders also pay. The builder must get a signoff from a government employed inspector at various significant points in the construction process. This also applies even to single family homes in most areas. Building code compliance is a local government function and not done by the federal government. Therefore, specific process and specification details vary from place to place.

Some of the cost for inspectors is covered by fees (building permits) charged to builders before they can start construction. Woe unto a builder who does a construction job without a permit.
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Old 02-12-2015, 07:58   #230
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Re: Oyster Problems?

So the thinking is that the keel trunk structure which consists of 4-5 fiberglass lateral girders encased by the keel stub fairing. The keel hangs from this box structure which failed (fiberglass sections broke apart). I am ignoring the one long bolt aft which is probably some kind of electrical thing but certainly not structural.

The fiberglass breaking caused the loud sound and vibration reported by the captain. The boat was turned from a reach so there was little or no heel thereafter. Then the dead weight of the keel was supported only by the hull skin and this force tore the hull open allowing water in. This sort of held together for some time while the crew furled staysail, radioed mayday and prepared abandon ship materials. The weight of the keel eventually was too much and a huge section of the hull completely delaminated and the whole mess including keel fell to the bottom. This caused the boat to immediately capsize.

I want to comment further but first I want to know if this scenario is an accurate explanation of what happened along the timeline. If this scenario is right the crew are obviously very skilled but also very lucky.
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Old 02-12-2015, 08:06   #231
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Re: Oyster Problems?

While these types of accidents seem to be quite rare at this time the comments of the CF members who are professionally involved in boat building and repair indicate that there are many vessels out there that may suffer structural failure as time goes on. One wonders if any reasonable type of survey could find defects of this nature.

It has been noted that aircraft which necessarily are built using advanced techniques to spread out loads are destructively tested and fatigue life limited. This vessel made passages for which it was apparently designed and exceeded its actual fatigue life without warning. As practical matter we could just say s**t happens but if cruising is the planned outcome of a boat purchase these "advanced" construction techniques may well be miss applied for those of us who want cruse as opposed to conducting a science experiment.
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Old 02-12-2015, 09:04   #232
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Re: Oyster Problems?

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Originally Posted by Alessiocannoni View Post
Some reply to your questions:
1-The story was published in Russia because Artur (the journalists and naval architect ) was the first one to investigate seriously around the accident; he was a Oyster fun, he came to Spain and he spent 10 days with me during last part of the rescue operation.
...
Alessio,


As said by others, I think you showed tremendous seamanship to not have a loss of life in this incident.
Trying to scapegoat you by slander is really bad and IMHO detestable.
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Old 02-12-2015, 09:17   #233
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Re: Oyster Problems?

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Originally Posted by Dockhead View Post
Not the whole Russian text is shown in the clip, but here's what is shown:

At the upper aft corner of the keel, red text: "Line of tearing off of the cladding" I think by cladding ("obshivka") is meant the outer skin of the hull, and they are indicating the dotted red line.

A red dot mid-way down the aft edge of the keel, with the label: "place of discovery of the first problems."

Then, at the lower right corner of the clip, is this text:

"Apparently, the vertical brackets failed first, not holding up under the loads from the keel. The fin lost strength in the vertical direction, between this and the bulb a gap appeared, and the whole mass of the ballast keel started to hang just from the outer skin of the hull."


So I guess what that means is that the hull outer skin was not intended to take the loads from the keel, and ripped out not because of a problem with the bonding (as speculated in posts above), but because of failure of the structural brackets first.

I'm neither engineer nor boatbuilder, but what they are calling "brackets" -- shown as 5mm (!) thick in the Russian drawing, sure don't look anywhere nearly up to the job, to my unqualified eye.
That is also what that Spanish independent surveyor had said regarding the most probable cause. I believe that the hull "skin" would have on this case and regarding the stub, also a structural function since the stub was part of the hull.

The saddest thing is that was an announced catastrophe, as on the magazine they point out given an airplane example, it was clear from the many problems on that area that something very wrong was happening.

The boat was repaired and the problem appeared again on the US.

It was a great risk to bring the boat from the other side of the Atlantic knowing that something was very wrong but most of all it was very dumb from Oyster not having send someone to US to see the boat out of water and to see and judge the gravity of the defect that was appearing again on the connection between the stub and the keel.

If they had done that they would probably have made a provisional repair and brought the boat motoring to the Oyster Shipyard for a full big repair and all this would be avoided.
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Old 02-12-2015, 10:21   #234
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Re: Oyster Problems?

Quote:
Originally Posted by transmitterdan View Post
So the thinking is that the keel trunk structure which consists of 4-5 fiberglass lateral girders encased by the keel stub fairing. The keel hangs from this box structure which failed (fiberglass sections broke apart). I am ignoring the one long bolt aft which is probably some kind of electrical thing but certainly not structural.

The fiberglass breaking caused the loud sound and vibration reported by the captain. The boat was turned from a reach so there was little or no heel thereafter. Then the dead weight of the keel was supported only by the hull skin and this force tore the hull open allowing water in. This sort of held together for some time while the crew furled staysail, radioed mayday and prepared abandon ship materials. The weight of the keel eventually was too much and a huge section of the hull completely delaminated and the whole mess including keel fell to the bottom. This caused the boat to immediately capsize.

I want to comment further but first I want to know if this scenario is an accurate explanation of what happened along the timeline. If this scenario is right the crew are obviously very skilled but also very lucky.
That's exactly what I'm thinking to..
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Old 02-12-2015, 11:10   #235
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Re: Oyster Problems?

Folks we have removed several posts that contained images that are the subject of a copyrights complaint from Yacht Magazine who affirm ownership of these images.

Please do not post images taken from another website here - you may post images that you have taken but not those taken by others unless consent is granted (directly to the forum). Thanks for understanding.
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Old 02-12-2015, 13:40   #236
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Re: Oyster Problems?

I AGREE, WE ARE SUPER LUCKY!!!!!
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Old 03-12-2015, 08:49   #237
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Re: Oyster Problems?

This is a great/deeply informative discussion (I really appreciate some of the posts concerning keel bolts). Given the photos of the failure on this Oyster (and the Beneteau First 40.7 Cheeki Rafiki) I was wondering how deep should a sailboat bilge be and from what surface point do you measure the depth? Said differently, what is the formula for an appropriate bilge design (boat length, weight, keel, etc.)? I’ve had a number of sailboats and with the exception of a Concordia 41, none of their bilges seemed to me to be that deep or large in diameter (see photo of new 2015 Beneteau - note we are having mast lights worked on so wires are usually not present). Thoughts appreciated.

PS: Alessiocannoni, sorry to hear about what you’ve been going through. Keep posting on Cruisersforum as I’ve found through experience that when you do, it gets the word out and the OEMs seem to respond as they do monitor this forum.
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Old 03-12-2015, 10:15   #238
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Re: Oyster Problems?

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Originally Posted by Fluer de Mer View Post


Said differently, what is the formula for an appropriate bilge design (boat length, weight, keel, etc.)?

Possibly there is no such formula. You design the bilge to perform a certain function and the engineering then is done to meet this function.

In other words, bilges can be anything from nil too very deep and from nil to very wide - all of them fine, as long as the design, engineering, materials and workmanship were executed flawlessly.

Engineering and design are here the same like for any other structures - choosing the right shapes and materials and their amount.

Building is done with safety margins as desired by the designer. There are boats with huge margins and boats with zero margins. Where speed is desired (racing) there are often zero margins BUT there is at the same time the bleeding edge design and engineering. (See damage of B. Stamm boat, e.g.)

b.
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Old 03-12-2015, 10:21   #239
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Re: Oyster Problems?

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Originally Posted by Janet H View Post
Folks we have removed several posts that contained images that are the subject of a copyrights complaint from Yacht Magazine who affirm ownership of these images.

Please do not post images taken from another website here - you may post images that you have taken but not those taken by others unless consent is granted (directly to the forum). Thanks for understanding.
Huh. That's interesting. A link to where to find them might be helpful.

Just so there's not any ambiguity here, the pictures showed a careless, sloppy build of a structure that most here would feel was so undersized as to be possibly criminally negligent.

Shame on Oyster, or rather, the selfish clowns who now own Oyster.
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Old 03-12-2015, 11:05   #240
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Re: Oyster Problems?

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Originally Posted by Fluer de Mer View Post
This is a great/deeply informative discussion (I really appreciate some of the posts concerning keel bolts). Given the photos of the failure on this Oyster (and the Beneteau First 40.7 Cheeki Rafiki) ....
The causes for failure seems to be different. On the Oyster the keel bolts seem to be innocent. It was the structure that supported the stub that seems to have failed as well as the hull composite that evolved it (the stub was part of the hull).
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