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Old 12-12-2015, 11:16   #376
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Re: Oyster Problems?

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Originally Posted by neilpride View Post
Dock, stubs are very popular for many brands, ask Minaret in how well build is the Nauticat keel stub, they are a really well design when the builder try to link a keel with a hull, they act like a proper bilge sump and the stub if is build it right can sustain lots of punishment without breaking the hull, add to this a strong inner structure and the result is a strong as hell keel conection...
I bet the Nauticat brackets are more than 5mm thick


No, I wasn't intending to malign all keel stubs, and defer to your knowledge of them.

I've never had a boat like that, but I can imagine that they could be very strong. If properly engineered, of course

I guess Oyster must be thrashing their naval architect about now for foisting this on them. Who designed that boat? Could not possibly have been Humphries, could it?
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Old 12-12-2015, 11:18   #377
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Re: Oyster Problems?

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Originally Posted by poiu View Post
...
Tha Oyster 825 keel was a terrible mistake of bad design/build and so is the First 40.7 for a whole set of totally different reasons. I have to say I am shocked that Polux is defending the First design and to imply it and other designs that are based on similar design principles are acceptable. They are so clearly unacceptable in my view.
It is obvious that the basic design, meaning a keel attached to a structure bonded to the hull is a sound design and it is one of the most used on the industry. You should read the conclusions and the observations of the chief engineer that leaded the investigation: That type of keel design is very popular on the industry and very successful as it is the one that uses Oyster.

With the Oyster it was not a problem of a particular type of design, but one regarding the right specifications and scantlings or building methods?

On the case of the First 40.7 it is a design that has to be inspected in what regards the bonding of the structure after the boat having some age or after having suffered groundings, as in any other boat with that keel design, and if needed repaired.

Not a particular problem with the First 40.7 specifically and again I am not the one that I am saying that just quoting what the chief investigator said. If that keel structure was inappropriate or dangerous he would have stated that and it was not the case.

However the First 40.7 represents a particular problem regarding the difficulty of inspection due to the type of structure and the chief engineer suggests that Beneteau should provide information regarding how to do that. I agree and I would add also the needed technological equipment or provide the service trough some of their dealers. Beneteau replied stating how the repair should be made even if to my knowledge that has not been made public.

Regarding the problem with some First 40.7, its gravity and dimension, it has nothing in common with the problem of the Oyster. There are about 600 first 40.7, most of them did not had any keel problem (even not having the keel properly inspected or maintained) some have done circumnavigations, many have been hard sailed and raced extensively for years and only two keels were lost both on boats that had been grounded and not properly repaired.

There is one First 40.7 making this Sydney-Hobart race and I bet they have full confidence on the boat. Several have made that race, one of the hardest, without any problem.
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Old 12-12-2015, 11:24   #378
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Re: Oyster Problems?

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Originally Posted by Kenomac View Post
Then maybe your memory needs a refresher.... Our Hunter 450 keel came loose and saltwater intrusion corroded the keel bolts without the boat ever experiencing a hard grounding
Maybe you need a refreshed for when I told you that the previous owner had asked about the boats keel being loose before selling it to you. It didn't suddenly come loose on you.

But you spin it however you want.

Yet that doesn't change the fact on this very expensive Oyster keel falling off and taking the stub right off the keel.
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Old 12-12-2015, 11:30   #379
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Re: Oyster Problems?

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Originally Posted by minaret View Post
The whole point here is that Oyster veered away from their "traditional solution" to the sort of thing you are constantly espousing, and this was the result. Everyone here but you can see that a return to the traditional solution is exactly what is called for.
You are wrong about that. The type of structure used was not different than on other many recent Oysters, or Halberg Rassy for that matter and it is a sound one.

In fact I did not understood what they were referring when saying this one was different. They talk about different building methods without specifying to what they are talking about.

It seems to me more a problem of inappropriate scantlings more than anything else and if they are talking about infusion as a method, well, the problem is not the infusion but the way it is done and controlled. Not the method in itself but the bad use of it, if it is about that they are talking about because nobody have really understood their explanations.
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Old 12-12-2015, 11:43   #380
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Re: Oyster Problems?

Quote:
Originally Posted by Polux View Post
. . .

It seems to me more a problem of inappropriate scantlings more than anything else and if they are talking about infusion as a method, well, the problem is not the infusion but the way it is done and controlled. Not the method in itself but the bad use of it, if it is about that they are talking about because nobody have really understood their explanations.
I think we can all agree about that.

I think there has been a lot of confusion in this thread between criticism of methods, and criticism of execution of those methods. I think there might have even been some intentional obfuscation of these different issues.

I think in the case at hand, we have two fundamental issues -- scantlings (5mm brackets!), and construction quality (infusion quality). The rest of it is are related, and interesting, but different conversations.
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Old 12-12-2015, 12:12   #381
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Re: Oyster Problems?

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Originally Posted by Polux View Post
You are wrong about that. The type of structure used was not different than on other many recent Oysters, or Halberg Rassy for that matter and it is a sound one.

In fact I did not understood what they were referring when saying this one was different. They talk about different building methods without specifying to what they are talking about.

It seems to me more a problem of inappropriate scantlings more than anything else and if they are talking about infusion as a method, well, the problem is not the infusion but the way it is done and controlled. Not the method in itself but the bad use of it, if it is about that they are talking about because nobody have really understood their explanations.


Very much so. But if scantlings aren't a critical part of the "method" of construction, I don't know what is. This is obviously not a case of a failed grid liner, but rather a case of a dramatically light build for a big boat. How does that mesh with your constant mockery of heavier layups? It's a ridiculous place to try to save weight in any case, just above the ballast keel. It really only saves the builder money, no reason not to put more material there, it would only make the boat stiffer. More glass, less ballast, same weight, no? It just goes to show that boat design, engineering, and construction is nothing like the space age science magazine readers like you are always trying to make it out to be on the forum. Especially when you start to look at bigger builds.
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Old 12-12-2015, 12:19   #382
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Re: Oyster Problems?

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Originally Posted by Dockhead View Post
I think we can all agree about that.

I think there has been a lot of confusion in this thread between criticism of methods, and criticism of execution of those methods. I think there might have even been some intentional obfuscation of these different issues.

I think in the case at hand, we have two fundamental issues -- scantlings (5mm brackets!), and construction quality (infusion quality). The rest of it is are related, and interesting, but different conversations.
Looking at design and to the photos I have doubts that the main problem was the thickness of the brackets (even if probably inadequate) but the thickness and resistance of the part of the keel structure that supported the stub and also the thickness of the hull around the stub. The stub was part of the hull and in that zone the hull worked structurally regarding maintaining the stub (and the keel) vertical.

The drawings on the Russian magazine regarding torsional forces are about that. Just speculating but if that stub moved around slightly stressing the hull, the many times that would happen would provoke an unexpected fatigue rate on the composite on that zone and that can be the ultimate cause for the failing. I very much doubt the calculations were incorrect, but that some factor was not taken in consideration and it can be this.
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Old 12-12-2015, 12:24   #383
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Re: Oyster Problems?

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Originally Posted by Dockhead View Post
I think we can all agree about that.

I think there has been a lot of confusion in this thread between criticism of methods, and criticism of execution of those methods. I think there might have even been some intentional obfuscation of these different issues.

I think in the case at hand, we have two fundamental issues -- scantlings (5mm brackets!), and construction quality (infusion quality). The rest of it is are related, and interesting, but different conversations.


I would love to know whether or not this hull was infused. Samples for burn testing would be very interesting. I believe even a field burn test would tell a lot. The few pics we've seen certainly have what looks like a dry layup, but a nice lean layup can look like that after heavy delamination. No way to tell for certain without burn testing. It also looks like there may be a lot of uni involved in the layup, which can lead to delam issues if not done right, especially in any resin system but epoxy. But it may just look that way due to where it delammed in the few pics I have seen. No point speculating, I'm sure more info will come out. Best thing for Oyster to do is divulge completely and return to the tried and true methods, it's what people buy an Oyster for. The other side of the coin is that anyone who shells out that kind of cash for a semi production boat without fully informing themselves about all details of it's construction before purchase shouldn't be too surprised with the results. This was obviously to anyone who bothered to look a pretty cutting edge design, and the last similar size and type boat I built cost more than twice as much to complete, and I'm sure took much longer. I would have had a lot of hard questions about this build before accepting delivery. That's not to say the owner didn't, or to lay the blame at his feet, at all. Just trying to say this is not the realm of the average cruising vessel, production or not, and things are very different in that size range. Caveat emptor rules the day here.
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Old 12-12-2015, 12:26   #384
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Re: Oyster Problems?

Dockhead,

Please include us in the users of forward looking sounders. Our forward looking Probe showed us the location of an uncharted reef in the Solomons. We could not see into the water, too muddy, opaque as hot chocolate. The display showed us exactly where to not go. It paid for itself many times over. Of course, we were going slowly enough to turn in time, too.

So yes, they have a place in the avoidance of a hard grounding.

And now, back to the discussion of what went wrong with the Oyster construction.

Cheers.
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Old 12-12-2015, 12:34   #385
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Re: Oyster Problems?

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Originally Posted by Dockhead View Post
I bet the Nauticat brackets are more than 5mm thick


No, I wasn't intending to malign all keel stubs, and defer to your knowledge of them.

I've never had a boat like that, but I can imagine that they could be very strong. If properly engineered, of course

I guess Oyster must be thrashing their naval architect about now for foisting this on them. Who designed that boat? Could not possibly have been Humphries, could it?


No "brackets" in my keel stub, you've seen the pics, wall thickness in my keel stub probably exceeds 3". Nothing but nice clean sump. A keel stub should be monolithic, it's the foundation for the rest of the boat. However, obviously when you start designing much bigger/deeper keels, the design challenges go up exponentially. Last one I did in that size range, I pulled hole saw cutouts for wire runs from the bulkhead/stringer tabbing overlap area near the keel that had carbon 2" thick on EITHER SIDE of the bulkhead. Mind you, this was in a tabbing overlap zone and hence not indicative of laminate schedule everywhere, but still quite an example.
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Old 12-12-2015, 12:51   #386
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Re: Oyster Problems?

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Originally Posted by minaret View Post
I would love to know whether or not this hull was infused. Samples for burn testing would be very interesting. I believe even a field burn test would tell a lot. The few pics we've seen certainly have what looks like a dry layup, but a nice lean layup can look like that after heavy delamination. No way to tell for certain without burn testing. It also looks like there may be a lot of uni involved in the layup, which can lead to delam issues if not done right, especially in any resin system but epoxy. But it may just look that way due to where it delammed in the few pics I have seen. ....
Oyster uses infusion and almost for sure that boat was infused and not only infused but "single-resin-injection infused". They made some publicity, that now looks very silly, about the new 125ft Oyster going to be the world's largest infused structure.

Regarding delamination and the fibers looking dry a specialist in composites stated that it was probably due to huge stress on that area.
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Old 12-12-2015, 12:58   #387
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Re: Oyster Problems?

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Originally Posted by Polux View Post
Oyster uses infusion and almost for sure that boat was infused and not only infused but "single-resin-injection infused". They made some publicity, that now looks very silly, about the new 125ft Oyster going to be the world's largest infused structure.

Regarding delamination and the fibers looking dry a specialist in composites stated that it was probably due to huge stress on that area.


Yeah, I read all the same magazines. We all do. Not looking for "almost for sure". For instance, those "brackets" were almost certainly hand laminated, because it wouldn't be possible to infuse them in place all at one go.
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Old 12-12-2015, 13:08   #388
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Re: Oyster Problems?

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Originally Posted by minaret View Post
Very much so. But if scantlings aren't a critical part of the "method" of construction, I don't know what is. This is obviously not a case of a failed grid liner, but rather a case of a dramatically light build for a big boat. How does that mesh with your constant mockery of heavier layups? It's a ridiculous place to try to save weight in any case, just above the ballast keel. It really only saves the builder money, no reason not to put more material there, it would only make the boat stiffer. More glass, less ballast, same weight, no? It just goes to show that boat design, engineering, and construction is nothing like the space age science magazine readers like you are always trying to make it out to be on the forum. Especially when you start to look at bigger builds.
There is the design of the structure and there are the scantlings needed that can vary on similar structure for different boats. One of the problems here seems to be the use of a structure adapted for heavy or medium build in a relatively light boat.

I agree that it makes no sense to save on the boat structure and if they wanted a lighter boat that was not the more adapted structure.

I believe that they went on with the stub type keel for commercial reasons: It looks stronger on the eyes of their traditional customers....but then they made it light because they wanted a light boat since many of the owners indulge in friendly racing, like the ARC.

That was a bad mistake, or maybe two: making a light keel of that type and choosing that type of keel structure for a light boat. That one implies a thick hull and a very strong connection between the stub and the keel structure.
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Old 12-12-2015, 13:25   #389
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Re: Oyster Problems?

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Originally Posted by Dockhead View Post
I think we can all agree about that.

I think there has been a lot of confusion in this thread between criticism of methods, and criticism of execution of those methods. I think there might have even been some intentional obfuscation of these different issues.

I think in the case at hand, we have two fundamental issues -- scantlings (5mm brackets!), and construction quality (infusion quality). The rest of it is are related, and interesting, but different conversations.
Part of the confusion seemed to lie in the references to the other 825's that had already been built, suggesting a faulty design or build process throughout the model line. Especially with the admission that all 825's were built with the "new" method, and that Oyster is abandoning that method & henceforth returning to their "old" method. But the reinforcing done to the other boats could also just have been an effort to reassure the other owners and preserve co. reputation, and doesn't necessarily mean the problems weren't confined to the one boat.
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Old 12-12-2015, 14:58   #390
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Re: Oyster Problems?

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There is the design of the structure and there are the scantlings needed that can vary on similar structure for different boats. One of the problems here seems to be the use of a structure adapted for heavy or medium build in a relatively light boat.
What makes 825 a light boat in your opinion? I find it very heavy and can't understand where they put all that weight, if the skin is only 15 mm in the keel area.

10 tonnes heavier than Swan 86 from 1988 or 15 tonnes more than the S&S 76. Current Swans and many others are clearly lighter than those two.
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