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Old 19-12-2015, 05:13   #751
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Re: Oyster Problems?

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Originally Posted by jmaja View Post
My "study" was targetted to those who claimed that production boats are weak, because they save in the amount of GRP material used. There is no real difference in the way say HR and Bavaria are laminated, at least not in the favour of HR, which uses a lot of chopped, ortho and spray lay-up (at least a few years ago). It's quite hard to know what the weight consists of in detail. You know the ballast. There aren't going to be a big difference in the weight of the engine and the rig, which total to about 300 kg in that size. The rest is more difficult, but since HR and Contessa use heavy wood interior it is unlikely to be lighter than the production builts. They probably also use heavier steel tanks vs. plastic for production boats. So I really don't see how production boats wouldn't use (clearly) more GRP than HR and Contessa. But how much of that GRP is in hull and keel structures?
Yes, but HR hulls are fully cored, and the mass produced boats are not. So the strength of HR hulls cannot be compared to those of Benes on a kilo for kilo basis.

Mass produced boats using single skin hulls need to use a large amount of GRP, to achieve what any of us would consider to be reasonable degree of strength. From Minaret's photos, I think we can see that they don't, at least not in that particular example.
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Old 19-12-2015, 05:16   #752
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Re: Oyster Problems?

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Originally Posted by Sandero View Post
Considering how many hulls are manaufactured.. even one or two dropped keels seems way too high a percentage. No?
Certailnly for Oyster 825, but that wasn't even a cheap production builder.

For e.g. First 40.7 it's too high percentage, but is that beacause of a too weak design or neglect by the owner or the repairing/inspecting yard.

I think much more the latter two than the first. Yes the boat could have been desinged stronger, but not in the same price and performance combination.

If you looked at the MAIB report and the link Polux gave about what to do after a grounding it is clear that CR was not looked after as it should have been. I find it very surprising they didn't remove the keel when they repaired several bays of the grid. As one result corrosion can be clearly seen in the pictures after the accident. The boat also had several groundings after that repair without any decent inspection.

Isn't the percentage of delamination way too high for HR? And the owner had to fight for years before he got a compensation from HR. He was close to end up with a total loss while an owner of a 40.7 "only" needs to pay for the insurance or the yard to get his boat fixed after grounding.
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Old 19-12-2015, 05:19   #753
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Re: Oyster Problems?

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Originally Posted by jmaja View Post
. . .
Isn't the percentage of delamination way too high for HR? And the owner had to fight for years before he got a compensation from HR. He was close to end up with a total loss while an owner of a 40.7 "only" needs to pay for the insurance or the yard to get his boat fixed after grounding.
That was an awful story. I'm sure there were two sides to it, and we've only heard the owner's side, but nevertheless HR should never have let it get to that.
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Old 19-12-2015, 05:24   #754
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Re: Oyster Problems?

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Originally Posted by Dockhead View Post
Yes, but HR hulls are fully cored, and the mass produced boats are not. So the strength of HR hulls cannot be compared to those of Benes on a kilo for kilo basis.
Bavaria uses cored hull as well (to waterline), but the French not in those models. HR glues the grid to hull while Bavaria laminates.
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Old 19-12-2015, 05:26   #755
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Re: Oyster Problems?

What is a mass production boat? seriously? How many hulls in what time frame?
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Old 19-12-2015, 05:28   #756
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Re: Oyster Problems?

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Originally Posted by jmaja View Post
But founding one or two Beneteaus loosing keel in the net does make them prone to this problem although that's porpotionally much fewer examples? Well that was not the point and I did not say HR is not safe. The point was to compare weights of the similar size boats of different price classes build from about the same materials (no epoxy, carbon etc.). That comparison doesn't support the claim that modern cheap production boats are built with less material than more expensive ones or older ones in order to save costs. Less material would lead to smaller displacement, which is not the case. There were much lighter boats in the 80's like Selection 37 (3.4 t) or X-99 (3 t), both build without high tech materials. And even those have been sailing 30 years quite OK. Yes part of the low weight comes from less interior, but still the hulls are much lighter. So where are they (Oyster 825 and the cheap production boats) putting that weight, if you think that hull and keel structure are too lightly built? What is done differently with HR and Contessa to reach lighter weight from similar materials, if you think they have a much stronger structure? I would undertand, if they used more sandwhich (hull, bulkheads) or stronger materials (epoxy, carbon) like Dehler, X, Arcona etc. do to reach better strength to weight ratio.
There are other considerations in effect, like how and where the the material is distributed. Number of structural bulkheads and the height of the grid are couple of things which contribute a lot for hull rigidity so that the total amount of material can be less and still better structurally compared other 'similar' hull with lesser structural members. Of course such parts are labour insentive ie more expensive.
Let me say again this has not much to do with the displacement of the boat which should be what it was designed to be and the lines of the boat define. You could use the same mold and make different hulls, one solid grp, other solid grp with double the bulkheads some ringframes and higher grid and a third with cored CF. If all these boats were to meet the same level of sructural integrity their hull weight should quite different, still the diplacement should be same becouse it's allready determined by the hull lines. How the displacement is put together is another matter.

BR Teddy
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Old 19-12-2015, 05:30   #757
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Re: Oyster Problems?

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That was an awful story. I'm sure there were two sides to it, and we've only heard the owner's side, but nevertheless HR should never have let it get to that.
I have read all the district court trial papers (mostly in Swedish) so I have "heard" the both sides. The owner lost there, but made an appeal to next court level. Before that trial HR and the owner made an agreement and he got a new boat. The details of this agreement were not relieved so I don't know if money was used and in what direction. It would be interesting to know what happened to the boat. Maybe it is in use?
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Old 19-12-2015, 06:43   #758
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Re: Oyster Problems?

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Originally Posted by neilpride View Post
Amel use for their keel something really diferent in all the aspects, they are bolted to a stub , the stub its really thick compared to some others brands, and deep, most amels keels use lots of bolts, in a supermaramu the number is 22 keel bolts , wow.... the water tank is made on top of the keel bolts , its watertight and glassed to the hull, I mean its integral with the hull , kinda of a second stub on top of the keel.. I never see one with any kind of keel problem by the way , they are simple following what they do in the past, strong boats....
An Amel Maramu is a 26 year old design and you seem to think Amel continues to build the boats the same way they built 30 years ago. They, as everybody else, mover forward and the design evolved.

Look at the photos I have posted of a new Amel 64: You can see that there is a clean hull built in to halves, no structural or other parts being an integral part of the hull (laminated with it) and all structural parts are added later, bonded and tabbed to the hull.
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Old 19-12-2015, 06:47   #759
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Re: Oyster Problems?

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There are other considerations in effect, like how and where the the material is distributed. Number of structural bulkheads and the height of the grid are couple of things which contribute a lot for hull rigidity so that the total amount of material can be less and still better structurally compared other 'similar' hull with lesser structural members. Of course such parts are labour insentive ie more expensive.
Let me say again this has not much to do with the displacement of the boat which should be what it was designed to be and the lines of the boat define. You could use the same mold and make different hulls, one solid grp, other solid grp with double the bulkheads some ringframes and higher grid and a third with cored CF. If all these boats were to meet the same level of sructural integrity their hull weight should quite different, still the diplacement should be same becouse it's allready determined by the hull lines. How the displacement is put together is another matter.

BR Teddy

Hang on... the same hull shape and form weighing different amounts has the same displacement? Ha?
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Old 19-12-2015, 07:13   #760
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Re: Oyster Problems?

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Originally Posted by Dockhead View Post
Yes, but HR hulls are fully cored, and the mass produced boats are not. So the strength of HR hulls cannot be compared to those of Benes on a kilo for kilo basis.

Mass produced boats using single skin hulls need to use a large amount of GRP, to achieve what any of us would consider to be reasonable degree of strength. From Minaret's photos, I think we can see that they don't, at least not in that particular example.
I believe cored hulls are stronger but the difference in what regards different types of building (to Beneteau and Jeanneau) is probably not so big in what regards weight for strength. Beneteau and Jeanneau use an integral "contre moule" bonded to the hull that increase hull stiffness, they are not a simple single skin hull.

Regarding production boats Bavaria uses cored hulls above waterline, Hanse uses full cored hulls (only the smaller boats use a solid laminate hull) as well as Dehler, Elan uses full cored hulls and Salona uses cored hulls with some zones in single skin.

I wish to all a very nice Christmas. A bit early but I will receive this year my family in my house (about 20) and I will have to interrupt my participation here since there is lot's of things I have to do for properly receive them. So Merry Christmas to all
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Old 19-12-2015, 08:04   #761
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Re: Oyster Problems?

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Hang on... the same hull shape and form weighing different amounts has the same displacement? Ha?
It means you have to have something else to get to the design displacement. It might be of heavier keel, more amenities, tankage, bigger engine, battery bank or whatever..

BR Teddy
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Old 19-12-2015, 08:05   #762
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Re: Oyster Problems?

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But founding one or two Beneteaus loosing keel in the net does make them prone to this problem although that's porpotionally much fewer examples?
Seldom does hull lamination issues, blisters, etc. put the lives of the crew at risk.

I continue to be amazed at the inability (or unwillingness) to prioritize the relative importance of different problems. Does this inability run right through the yachting establishment? If so, then we have found the problem and it is us.
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Old 19-12-2015, 08:07   #763
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Re: Oyster Problems?

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So if we look at the boats in test in Yacht 16/2015
Which of these boats do you propose to cross an ocean in? According to Bob Perry the HR-310 is a coastal cruiser. We are not talking much about this class of boat in regards keel failure. We are talking about boats that are intended to safely take the crew far off shore.
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Old 19-12-2015, 08:13   #764
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Re: Oyster Problems?

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Nice indeed! and now the owner will be banging away on it with a great muddy chunk of steel... I hope you sold him a bottle of Brasso to keep it shiny!!

Jim

PS: How thick is the s/s on the plate? I made one that was too thin and it quickly got dented in.


Plenty thick. It's ready for ramming speed! I tried to sell them on some Mad Max spikes at the waterline, too, but it just wasn't their style.
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Old 19-12-2015, 08:34   #765
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Re: Oyster Problems?

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That's just crazy. That would surely shatter on impact even at 0.5 knots.

And I guess no water-tight bulkhead behind, either?

On the other hand, there are thousands of these boats sailing around, and you don't hear about dozens of sinkings.
Yes, that's why they had me do it. Last time the boat hit the dock at 1/2 knot, it did so much damage I had to grind a big hole right through the hull. Damn thing is fragile like an eggshell. It even has fractures from the anchor hitting the bow when it's coming up. Light Roberts Gray is a bear to match, they were tired of paying me to repair the bow of this boat over and over. I love it, boats like this are excellent job security!
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