Rocna Size

[Khagan1227]

One of the courses I was required to take in college was metallurgy, so the charpy tests and hardness tests were something we were required to both learn and the replicate in the lab at school. However, I am NOT in the metallurgy field.

That said, I can tell you if you perform tests on 100 items, none will have exactly the same results due to a number of reasons. However, if a manufacture of nuclear reactor vessels tells the Nuclear Regulatory Commission that a particular vessel has a minimum hardness of Brinell 200, the manufacture will ensure through testing that ALL vessels have at least 200.

We could go into a long winded discussion on standard deviations, six sigma, etc. but to cut to the chase; if a company wants to print a minimum hardness, they will usually pick a hardness number low enough that they can guarantee that any metal they plan to use in the manufacturing process will never fall below the number they are willing to guarantee if tested.

So in the case of Ronca, if their specification for the shank is 400MPa, then 697MPa would probably ensure they never fall below 400MPa. If they are going to guarantee 800, the number found "should be" well above 800MPa to avoid this type of discussion.

I do find a quote I took from Peter Smith's website to be of interest, since Mr. Smith made whilst comparing a Ronca to a Manson "knockoff":


Originals vs. Variants and Copies

Original anchors are generally superior to the copies, since the copies have limited ways in which to differentiate themselves in the market. The usual manner is to sell at a lower price, which requires reduced costs. Normally there is a good reason for the cost of the original; copies take obvious construction short-cuts, such as cheaper methods of fabrication, which the original manufacturer elected not to. These compromises result in a more attractive retail price, but the axiom “you get what you pay for” has never been truer.

About the Manson Supreme Anchor

[estarzinger]

Originally Posted by conachair

The northwest laboratories test results came out at 697MPa for the shank so something doesn't tally up there.

Just looking purely at the published test data . . .

We have three tested Rocna's:

NZ tested Rocna 10: tensile = 589 mPa
US tested Rocna 10: tensile = 697 mPa
NZ tested Rocna 25: tensile = 731 mPa

and two tested Manson's:

NZ tested Manson 25: tensile = 882 mPa
NZ tested Manson 45: tensile = 876 mPa

The tensile spec for Bisplate 80 is a range of 790 - 930, with a "typical" of 830. Based on the test results we can say with some reasonable degree of certainly that Manson is using this grade and that Ronca China is using a lesser material.

Purely looking at this test data, if Ronca is using a single grade of steel for the shank, the best fit to the test data is 600mPa spec from a supplier with lower quality consistency than Bisplate. The tensile spec for Bisplate 60 is a range of 590 - 730, with a "typical" of 640.

400mPa steel is NOT a good fit to this Rocna data, which would have a normal spec range of 395 - 485 and none of the test points fit in that range.

[Shawn67]

"I suppose the blameless in this is the Chinese factory that is making weaker-than-spec Rocnas exactly as they've been told to do."

If the above is true (400 MPa shanks) the Chinese factory is really building anchors that so far are testing out as stronger than specified.

The problem then would be that the specs they are building to may not be what they once were or are still advertised to be.

Shawn

[marinextreme]

the 400mpa referred to was YIELD strength minimum.

The minimum spec required to meet the design specs is 690mpa yield.

How much more simple can it be?

[marinextreme]

Originally Posted by Dockhead

So you're saying that ALL of the Chinese Rocnas were built with shanks of material specified at 400mpa by the parent company in New Zealand? All of them of all sizes?

Why didn't you say this earlier - that information was highly relevant to the whole conversation from the very beginning.

I had been waiting on legal advice regarding what I can say in open forum and what I cannot say without releasing what Bambury can claim is "Intellectual Property" and therefore has to be kept "secret" even at the expense of the "truth" coming out.

The result of this is that I now have a clear path to follow with any information released and also have the right to publicly respond to Bambury's claims regarding my supposed "behaviour" and can release any information I "discovered" through my own investigations during my time with them as opposed to any information that I was given as "confidential"
, in writing, by them.

I also can release any photos or video, any sound recordings of conversations and any emails I have sent to them and their responses to those communications.

As stated earlier, everything I say is backed by documented evidence, some of it confidential, some of it not, and they have the right to take legal action to shut me down or shut me up if they choose.

Quite frankly I wish they would take that course of action because the information I have can then be out in the open as a matter of public record.

[Delfin]

Originally Posted by estarzinger

The tensile spec for Bisplate 80 is a range of 790 - 930, with a "typical" of 830. Based on the test results we can say with some reasonable degree of certainly that Manson is using this grade and that Ronca China is using a lesser material.

Purely looking at this test data, if Ronca is using a single grade of steel for the shank, the best fit to the test data is 600mPa spec from a supplier with lower quality consistency than Bisplate. The tensile spec for Bisplate 60 is a range of 590 - 730, with a "typical" of 640.

400mPa steel is NOT a good fit to this Rocna data, which would have a normal spec range of 395 - 485 and none of the test points fit in that range.

That's pretty much the conclusion I have come to - Manson uses what Rocna says they use but don't - the equivalent to Bisplate 80. Rocna is actually using the equivalent of Bisplate 60, which would fit my test results. A pure speculation which I think is confirmed by what Grant has said (correct me if I am wrong, Grant), but it is possible that for a period of time, Rocna used a very low grade of steel that showed up in the Venice anchor, and probably the pretzel versions we have pictures of. That produced an anchor that was a joke, so they upgraded to a specification that still was below what they were advertising rather than spend the money on an appropriate grade.

Another confounder is something I pointed out from my test results that hasn't really been discussed, and that is that testing for tensile strength gives a maximum value for the steel if you pull it in line with the grain of the steel that is formed during the rolling process. If you don't determine the grain direction, the technician at the lab told me you would get a lower value. As a result, you can view my result as the maximum possible strength, and may be that the Rocna tested by Manson was not tested with the grain, giving a lower value even though it was the same grade of steel that was in my anchor. When laying out a sheet of steel to cut the shanks, they could be laid out so that the grain ran in the direction of the shank, or to maximize yield from a sheet of stock, could be laid out otherwise. If this is what Rocna is doing, you would have some variation in testing strength of anchors made of the same specification steel. The importance of my test is that it is the maximum for this steel, which rules out Rocna using the grade they promise, and people pay for, or the retailers they sell to expect.

[marinextreme]

Originally Posted by Delfin

That's pretty much the conclusion I have come to - Manson uses what Rocna says they use but don't - the equivalent to Bisplate 80. Rocna is actually using the equivalent of Bisplate 60, which would fit my test results. A pure speculation which I think is confirmed by what Grant has said (correct me if I am wrong, Grant), but it is possible that for a period of time, Rocna used a very low grade of steel that showed up in the Venice anchor, and probably the pretzel versions we have pictures of. That produced an anchor that was a joke, so they upgraded to a specification that still was below what they were advertising rather than spend the money on an appropriate grade.

Another confounder is something I pointed out from my test results that hasn't really been discussed, and that is that testing for tensile strength gives a maximum value for the steel if you pull it in line with the grain of the steel that is formed during the rolling process. If you don't determine the grain direction, the technician at the lab told me you would get a lower value. As a result, you can view my result as the maximum possible strength, and may be that the Rocna tested by Manson was not tested with the grain, giving a lower value even though it was the same grade of steel that was in my anchor. When laying out a sheet of steel to cut the shanks, they could be laid out so that the grain ran in the direction of the shank, or to maximize yield from a sheet of stock, could be laid out otherwise. If this is what Rocna is doing, you would have some variation in testing strength of anchors made of the same specification steel. The importance of my test is that it is the maximum for this steel, which rules out Rocna using the grade they promise, and people pay for, or the retailers they sell to expect.

Correct, the test results do indicate MAXIMUM strength before breakage and that is in a directional pull.

The new material signed off in March 2010 had an addition of chromium to add hardness to it.

Your photo of the stretched piece of metal shows just how far it will stretch before breaking. The bending point is far below that and this is where they are failing.

So the question needs to asked when assessing if it "fit for purpose" is if the anchor is still "fit for purpose" if it bends under sideways load or is "fit for purpose" only considered if it does not break.

Even the results from your own test show that the resistance to bending is severely compromised and as it is below the design parameters then it is not " fit for purpose". There can be no argument about it.

I have a test report on file that was done on a NZ manufactured unit to assess the problem of faulty galvanising in 2009 and it revealed that the metal in the shank was an equivalent specification to Bis80. It was the chemical makeup of the metal that was causing the galvanising issue as these hi tensile metals require special treatment during the galvanising process ( beadblasting). The important factor is that the NZ manufacturer was using the correct spec material and as such there should be no worry whatsoever about the strength of the NZ anchors, or of the Canadian ones.

[marinextreme]

Delphin,

The chinese factory use a multi million dollar , computor controlled water cutting machine to cut the plate.

The program lays out the cut of each sheet to maximise the return and minimise the wastage from every sheet.

There is no consideration applied for direction of grain.

[Exile]

How much cheaper is it to produce the Chinese anchors with lower tensile strength than with the metal used in the NZ & Canadian anchors? Presumably it's already cheaper to produce in China so I wonder what additional financial incentive Rocna may have had to use lower standard materials. Assuming this was willful on Rocna's part and not a failure on the mfg. end as alleged, it seems like an awful lot of risk for a company to take if the cost differences weren't substantial.

[marinextreme]

Originally Posted by Exile

How much cheaper is it to produce the Chinese anchors with lower tensile strength than with the metal used in the NZ & Canadian anchors? Presumably it's already cheaper to produce in China so I wonder what additional financial incentive Rocna may have had to use lower standard materials. Assuming this was willful on Rocna's part and not a failure on the mfg. end as alleged, it seems like an awful lot of risk for a company to take if the cost differences weren't substantial.

In a single word...huge.

I cannot release any financial information sorry.

[Exile]

How about an estimate of the difference in material cost only, and per anchor? Or is the cost difference based less on materials and more on more expensive mfg. processes to produce anchors with higher tensile steel?

[avb3]

I am learning more about anchors then I ever thought I would need to know. I had no idea that there was a grain involved in steel, and that it can impact intended performance in a manufactured item.

Delfin and Grant, thank you so much for your input on this. I suspect many who are reading this thread will have a whole new perspective of issues they will consider when making a decision on which anchor to obtain, and this will not be restricted only the negativity surrounding Rocna.

If I was the Smith's, I would be looking at what legal recourse I would have take back the product from the licensee. I would think that if the agreement was drawn up correctly, there is no reason that it can not be cancelled.

This development may even cause other anchor manufacturers to reconsider their own specs. Suffice it to say that I can't imagine anyone who has followed this would still consider a Rocna.

I would hope that large distributors like WM as well as magazines take a close look at this fiasco. I can only suggest that it is important to the sailing community that all players ensure that safety is number one.

The end result can only mean a better result for boat owners.

[estarzinger]

Originally Posted by Delfin

That's pretty much the conclusion I have come to
Manson uses . . . the equivalent to Bisplate 80. Rocna . . . Bisplate 60

it is possible that for a period of time, Rocna used a very low grade of steel that showed up in the Venice anchor, and . . . they (then) upgraded to (Bisplate 60) specification

Agreed. Your anchor and the ones Manson tested are all of recent vintage. It would be interesting to go back and test (publicly) a couple from the Venice vintage to see if the grade was lower then (I am sure Grant and Rocna know the answer but it does not appear anyone will make it public). I am not a material expert, but I believe you could do this with a non-destructive hardness test and get a sufficiently accurate answer to be useful.

We don't have many data points, but with my QA hat on, I am struck by the high standard deviation in the Rocna results and the tight consistency in the Manson results. The yield range for the Rocna anchors is 35% while it's 4% for Manson (statistical warning: extremely small sample sizes!). So there is a suggestion that either Rocna is using a steel supplier with low product consistency or they are sourcing from different suppliers with quite different specs. Neither is very good for process consistency.

I do wish we could get a better handle on the true number of bent Rocna anchors. If the number is actually 5, and the Chinese production has been 5000 = .1% = 4.6 sigma = not "world class" (Which would be greater than 5 sigma), but also not too bad (which would be less than 3 sigma).

[Delfin]

Originally Posted by estarzinger

The yield range for the Rocna anchors is 35% while it's 4% for Manson (statistical warning: extremely small sample sizes!). So there is a suggestion that either Rocna is using a steel supplier with low product consistency or they are sourcing from different suppliers with quite different specs. Neither is very good for process consistency.

I do wish we could get a better handle on the true number of bent Rocna anchors. If the number is actually 5, and the Chinese production has been 5000 = .1% = 4.6 sigma = not "world class" (Which would be greater than 5 sigma), but also not too bad (which would be less than 3 sigma).

I doubt if any steel manufacturer anywhere in the world would have that much variation in the physical characteristics of its product, so I assume that Rocna was using whatever steel the builder had on hand, as long as it was above some minimum - like 450 MPa yield - putting cost savings above boater safety. If they've used up the scrap heap to make anchors, they have to buy something, and what they appear to be buying now is steel in the range of Bis60. If so, they are still trying to pull the wool over everyone's eyes, even if it is better than the butter steel they were using for awhile.

Grant, do these suppositions match your experience on site? Also, didn't you indicate that there were many more bent anchors you dealt with than just the ones we have pictures of?

[estarzinger]

Originally Posted by Delfin

Grant, do these suppositions match your experience on site? Also, didn't you indicate that there were many more bent anchors you dealt with than just the ones we have pictures of?

I am trying to draw conclusions from the data we have publicly from independent sources to answer two questions that I would think a current owner of a Chinese Rocna would want answered:

1. Was the product sold with 'false and misleading' advertising? We clearly have what appear to be two direct lies - related to "full RINA certification" in official press releases, and related to steel grade on the web site, plus quite a number of misleading statements about the holding power and competitor's products.

In my mind this clearly gives any current owners the full right to return their anchor for a full refund. Some will want to return their anchor because they no longer trust it and some will want to because they don't want to have anything to do with such an apparently low integrity company.

But some of those owners, while disappointed about the integrity of the marketing, may still want to hold onto their anchor if it is 'suited to purpose'. So the second question . .

2. Does the anchor perform well enough and is it strong enough to trust? Related to performance - Those who conducted the SAIL anchor test believed overall it equalled the manson supreme (but did not outperform it as CS claimed), and the various owner feedback seems to support this. So I think we can say it has adequate performance, equal to its main competitors. Related to strength - we unfortunately have inadequate public data. I would like to see the actual sideway's shank yield forces for similar size Rocna, Manson and Delta (current production and Venice error production), and the actual real world shank bending rates. However, the limited data we have suggests that the rocna bending rate is probably higher (and their quality control lower) than manson but not excessively so by marine standards (since this story broke, we have certainly NOT seen a flood of owners reporting they have bent or broken their anchors). So, on both factors, with the public data we have, I conclude that the Rocna is clearly NOT superior but is probably adequate and if an owner likes it he is probably not facing any undue safety risk to use it.

That's what I conclude from the independent public data we have available.

That conclusion could/would change if we got hard independent facts that the steel used in multiple Venice era anchors was a much lower grade than used in any of the recently tested anchors and/or if the actual bending rate was much higher than we are currently aware of. But, again, given we have not heard from many owners about bending anchors since this became public, the size of this 'unknown known' is bounded and constrained, so that there are not any shocking surprises left.