I hate to do this...but

vyv_cox said:
The reason I replaced mine with a Rocna. Vliho Bay, Ionian Sea about three years ago. Very strong winds were forecast so we headed there as being a well sheltered anchorage, although the bottom is soft mud. Anchored as normal, winds arrived shortly and we were amazed to find ourselves dragging, first time in about 15 years on this anchor. Winds continued to increase and gust viciously, some of the worst I have ever experienced. The Delta was completely unable to cope, three further attempts all unsuccessful. Each time I hauled it there was no weed, just the soft mud. Many other boats around us were experiencing problems, although quite a few were soundly anchored.

Ultimately I went astern upwind towards some trees until we touched bottom and we took lines ashore to them. On reflection later I suspect that replacing the Delta with the Fortress would have been a good solution, but by this time I had trapped my finger in the windlass :eek: and didn't fancy the effort.

If not for that experience I would still use a Delta, otherwise excellent on a wide variety of bottoms from the Baltic to the eastern Med.
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My Delta, which has held well in a variety of bottoms and weather conditions is as much use as a fish hook in soft to liquid mud conditions. For that reason I carry a Fortress which is unbeatable in those conditions when assembled on the soft mud setting. OTOH there are plenty of circumstances where I wouldn't use a Fortress. No one anchor will suit all situations. See my 'How many anchors?' thread.
 
Ronca have always derided anything that may be similar to its anchor saying that nothing is like the original. They say that copies are just cutting costs and cannot match the Ronca.
Is the China version a copy of the original Ronca from NZ?
 
Delfin said:
Illustrating once again what a clever observer of human nature P.T. Barnum was...:)
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Heard of barnum but that's all so no idea what that means.

We are now arguing about semantics which will never be resolved.

On my boat a failure of the anchoring system means the boat is no long connected to the planet and ends up on the rocks.

A very bad day a failure is a bent shank, made exponentially worse if the makers were telling porkies about the grade of steel used, but that would only effect how much it would bend.

There is no reliable data from Venice, people on here will read whatever they want into it.

As far as I am aware there have been no documented failures of rocnas, online anyway.
Which doesn't mean much, being big chunks of metal anchors tend not to fail, other links in the system go first.
 
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Rigger Mortice said:
The Venice shank bent because the steel was below specification.

Guilty, M'lud.
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No it didn't. It bent because the force applied was greater than the strength of the shank could sustain. It might even have been that a Manson or a perfect Rocna would have done the same because we know nothing of the force, nor what was resisting it.

We have already established that, based on their own figures and those of the independent tester, a Fortress would have done the same, or worse. To say nothing of the stainless and aluminium versions of many of the other manufacturers.
 
vyv_cox said:
No it didn't. It bent because the force applied was greater than the strength of the shank could sustain. It might even have been that a Manson or a perfect Rocna would have done the same because we know nothing of the force, nor what was resisting it.

We have already established that, based on their own figures and those of the independent tester, a Fortress would have done the same, or worse. To say nothing of the stainless and aluminium versions of many of the other manufacturers.
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That was a totally false statement about our product. Thickness and proper machining of the metal will enable it to handle loads more efficiently.

Proof of this was evidenced by the extensive US Navy tests that were conducted several years ago. All of the steel Danforth anchors were completely destroyed in the test, and there was some surprise to this result, as it was noted in the report that the high grade of steel used in the Danforth anchors was stronger than the aluminum alloy used by Fortress, which was cause for this analysis in the test report:

"The fact that the Fortress anchors incurred no significant structural damage at such high holding ratios suggest that the anchors have been extensively engineered from both the hydrodynamic and structural standpoints."

I find a comparison of our product with Rocna to be, quite frankly, insulting as I cannot comprehend manufacturing and advertising a safety product to be made of a superior material, and then making it at a lower grade and with a higher possibility of failure. Absolutely unconscionable.

Brian
Fortress Marine Anchors
 
vyv_cox said:
No it didn't. It bent because the force applied was greater than the strength of the shank could sustain. It might even have been that a Manson or a perfect Rocna would have done the same because we know nothing of the force, nor what was resisting it.

We have already established that, based on their own figures and those of the independent tester, a Fortress would have done the same, or worse. To say nothing of the stainless and aluminium versions of many of the other manufacturers.
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Vyv

Bless you!

There is nothing like a professional engineer, totally without vested interest, to keep a thread to the key facts. I also think you are doing a good job in keeping one or two posters with vested interest on the straight and narrow!

I severely bent the shank of a CQR a few years ago - but it kept me off the rocks and I never regarded that as a failure either.

Rocna clearly have some questions to answer; but lets keep our feet on the ground until either they, or some other agency, back up the Manson Report with an independent analysis of a larger sample.

That work could also perhaps include testing a Rocna and rivals to destruction to find out what fails at what point. Indeed, to follow up your earlier point, it would be ironic if even a sub-standard Rocna outperformed some of its rivals in these tests!

Even as I develop this idea, it becomes clear to me that what we really need is a journalist, with a yachting and engineering background, to devise the tests, have them carried out scrupulously fairly, and publish the report in a yachting magazine.

A bit like that excellent article and tests you did with chain connectors a while ago .....Vyv.......;)

Go on - you know you want to despite the death threats that would result :eek:
 
Tradewinds said:
What a totally stupid comment (even if you meant it in jest) :(
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I put a silly face at the end of the comment to indicate it was a jest.;)

Its a pictorial way of saying don't take this seriously because all I am doing is making a bit of harmless fun about people who take things too seriously.:D

.....and then along you came and took it seriously <sigh>:(

But hey! It was my comment and I take full responsibility for it being stupid.:(

So thank you for your comment Tradewinds I shall try harder in future:rolleyes:
 
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silver-fox said:
I put a silly face at the end of the comment to indicate it was a jest.;)

Its a pictorial way of saying don't take this seriously because all I am doing is making a bit of harmless fun about people who take things to seriously.:D

.....and then along you came and took it seriously <sigh>:(

But hey! It was my comment and I take full responsibility for it being stupid.:(

So thank you for your comment Tradewinds I shall try harder in future:rolleyes:
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Thank you :)
 
Brian@Fortress said:
That was a totally false statement about our product. Thickness and proper machining of the metal will enable it to handle loads more efficiently.

Proof of this was evidenced by the extensive US Navy tests that were conducted several years ago. All of the steel Danforth anchors were completely destroyed in the test, and there was some surprise to this result, as it was noted in the report that the high grade of steel used in the Danforth anchors was stronger than the aluminum alloy used by Fortress, which was cause for this analysis in the test report:

"The fact that the Fortress anchors incurred no significant structural damage at such high holding ratios suggest that the anchors have been extensively engineered from both the hydrodynamic and structural standpoints."

I find a comparison of our product with Rocna to be, quite frankly, insulting as I cannot comprehend manufacturing and advertising a safety product to be made of a superior material, and then making it at a lower grade and with a higher possibility of failure. Absolutely unconscionable.

Brian
Fortress Marine Anchors
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Brian,

If you look back to the postings around #388 you'll see that Vyv had done some back of an envelope calculations based on his recollection of the sizes of his Racno and Fortress anchors which were not to hand. I must admit that I did not think that this had ended as a definitive and conclusive proof, it was more of a discussion point awaiting further information, but there it is.

However, it would be helpful if you could give some figures for the dimensions of your shanks so that some more objective comparisons can be made.

What I hope is not in doubt with people here is that if Fortress say their product is made from a particular grade of metal, then it will be.
 
vyv_cox said:
No it didn't. It bent because the force applied was greater than the strength of the shank could sustain. It might even have been that a Manson or a perfect Rocna would have done the same because we know nothing of the force, nor what was resisting it.

We have already established that, based on their own figures and those of the independent tester, a Fortress would have done the same, or worse. To say nothing of the stainless and aluminium versions of many of the other manufacturers.
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silver-fox said:
Vyv

Bless you!

There is nothing like a professional engineer, totally without vested interest, to keep a thread to the key facts. I also think you are doing a good job in keeping one or two posters with vested interest on the straight and narrow!
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Key facts? Having established that no one knows what the force applied to the Venice anchor was, vyv cox then goes on to conclude that this unknown force would certainly have been enough to bend (or worse) a Fortress, even though the designs and materials are completely different. Agnostic and open minded in the former, omniscient in the latter. Must be useful to be an engineer with such powers, but if lacking those powers, perhaps not so unvested, interest-wise, after all.

What is pertinent here is not the absolute tensile strength of materials in the abstract, but whether those materials are engineered and used in such a way that the end product performs as advertised. If Rocna is, as it appears, using steel they themselves claim is inadequate for anchor manufacturing, in a design they insist requires a higher grade of materials then they are scam artists. I don't need to be an engineer to know that to try to equate such a scam product to those made honestly to a particular design standard is dishonest and mis-leading. Shame on you, Mr. Cox.
 
Delfin said:
Key facts? Having established that no one knows what the force applied to the Venice anchor was, vyv cox then goes on to conclude that this unknown force would certainly have been enough to bend (or worse) a Fortress, even though the designs and materials are completely different. Agnostic and open minded in the former, omniscient in the latter. Must be useful to be an engineer with such powers, but if lacking those powers, perhaps not so unvested, interest-wise, after all.

What is pertinent here is not the absolute tensile strength of materials in the abstract, but whether those materials are engineered and used in such a way that the end product performs as advertised. If Rocna is, as it appears, using steel they themselves claim is inadequate for anchor manufacturing, in a design they insist requires a higher grade of materials then they are scam artists. I don't need to be an engineer to know that to try to equate such a scam product to those made honestly to a particular design standard is dishonest and mis-leading. Shame on you, Mr. Cox.
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The shank in question was 400mpa.
That fact was confirmed by the manufacturers.
It was my job to find the reason for all failures and to examine and report on all claims.
Faulty product was replaced
Excuses were given
Truth was hidden
 
Delfin said:
Having established that no one knows what the force applied to the Venice anchor was, vyv cox then goes on to conclude that this unknown force would certainly have been enough to bend (or worse) a Fortress, even though the designs and materials are completely different.
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Yup, that's the joy of two hundred years of stress analysis and materials engineering - we can compare the bending moments at failure of two different designs in two different materials.

http://en.wikipedia.org/wiki/Section_modulus#Elastic_section_modulus

That said, it's not just the material and shank design - there are aspects of anchor performance to consider as well. Perhaps a Fortress (or a CQR, or a Delta, or a Manson, or ...) would have pulled out / rotated / reset before putting enough sideways force on the shank to bend it.
 
Ubergeekian said:
That said, it's not just the material and shank design - there are aspects of anchor performance to consider as well. Perhaps a Fortress (or a CQR, or a Delta, or a Manson, or ...) would have pulled out / rotated / reset before putting enough sideways force on the shank to bend it.
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Perhaps. Perhaps not.

However, the man whose job it was to investigate these things is able to tell us that this shank bent because it was made from substandard materials.
He is telling us that, if it had been made to spec, it would not have bent.
He also reports that there was a cover up after the event.

All the theorising in the world cannot alter that.
 
Ubergeekian said:
Yup, that's the joy of two hundred years of stress analysis and materials engineering - we can compare the bending moments at failure of two different designs in two different materials.
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However, as vyv Cox noted, we do not know the force the Venice anchor was subjected to. Stress analysis requires that you know the stress. To make the statement without knowing that value or a test "that we have already established that" a completely different design made of completely different materials would certainly have failed is untrue, unprofessional and calls into question the objectivity of the person making the statement. I prefer engineers that deal in data, not speculation presented as fact.
 
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