Rocna Size

[Delfin]

Originally Posted by sailingaway221

Yes..... the reason it bent is because it is designed to bend and not to break.... If it had been heat treated as a chisel it would have been brittle and snapped...... bending your anchor shaft under extreme load isn't a bad thing... for it to bend like that it has a tremendous load on it..... and it did not fail...... it held. I would say this guy hooked something and bent the shaft around it...... however even after doing this the anchor did not " fail" ( break ) and set the boat free. Just a little point but the Rocna I have on my boat has a MUCH thicker shank on it than this. It looks like this guy has a small anchor that he loaded up with a lot of weight from a funny direction.... this is not a bad anchor ( under extreme load the shank held ) .... its a bad job of anchoring or retrieval.

Interesting perspective. Perhaps that was Rocna's thinking when they substituted mild steel for the much more expensive Bisalloy 80 quenched steel they advertise and that Peter Smith declares to be essential to the design. Without telling anyone, of course.

Like you, they may have thought that bent shafts are an attribute, not a fault.

[sailingaway221]

Not sticking up for them stating something on their website and doing something else if they are.... however I have 0 complaints about my anchor and I use it alot.... however if I pull it up one day and it is bent like that I would consider myself lucky that it bent and did not break... then go buy another one exactly the same again.

[Delfin]

Since this is a topic of general interest on a vital piece of safety equipment, I’m posting the below to the 4 sites I participate in, not to beat up on Rocna, but because most everyone with a boat needs an anchor, and sometimes one’s boat and the safety of the crew depends on the integrity of the anchor manufacturer. By way of full disclosure, I use a 176# Bruce type Claw on Delfin, and it has served me well, so far. I have zero financial interest in any anchor manufacturer or marine distributor.

I recently purchased a Rocna 22# anchor for testing because it seemed as if there were many opinions on the strength of this anchor, but not enough objective data to make a final conclusion.

To test my Rocna, I took it to NW Laboratories, who have been performing metal testing in the Seattle area since 1896. An initial hardness test was performed, since tensile strength can be correlated to hardness, and on the basis of that test the anchor was submitted to full testing to determine whether the steel used matched the grade of steel advertised by Rocna. By way of background on the importance of steel quality, here is what Rocna has to say about the steel it uses:

The shank on any anchor is a common failure point, normally bending when a high lateral load is applied (for instance, when the anchor fouls on a submarine obstacle and is jammed). For this reason, the shank on the Rocna is a high tensile quenched and tempered steel, with a grade of around 800 MPa. Its pure resistance to bending is around three times that of mild steel. This adds to the price of the anchor, but compromising this strength is not something we would entertain.- Anchor materials (Rocna Knowledge Base)

In this, Rocna is stating that their anchors will be more expensive than cheaper anchors because they want to avoid a “common failure point”, which would be the bending of anchor shanks with steel that had an Ultimate Tensile strength less than 800 Mega Pascals (MPa), or 120,000 psi. This type of steel meets the standards set in ASTM A514, has a Yield Tensile strength of 720 MPa and is available from Bisalloy Steel in Australia, as well as other companies worldwide, including sources in China where the Rocna is made.

In discussing why Rocna doesn’t manufacture an aluminum alloy anchor, they expand on the importance of and the reason for using 800 MPa high tensile steel in their anchors:

For example, an aluminum shank would not be able to possess the same tensile strength as the 800 grade steel we use without being significantly thicker, which would then affect setting performance in hard sea-beds. Anchor materials (Rocna Knowledge Base)

In other words, without high tensile 800 MPa steel in the shank their anchor would have to be thicker to withstand the loads typically imposed during normal usage, and this would affect the balance of the anchor adversely when it comes to setting ability.

Finally, in the User’s Guide that comes with each Rocna there is a statement that underscores how the Rocna anchor is superior to its competition because it addresses one of the shortcomings of most anchors – weakness in the shank:

"The Rocna was designed to address the limitations shared by all older and most newer anchors available. These designs suffer from ….. "insufficient strength in the shank or other load bearing components."

Clearly, Rocna believes that the unique design of the Rocna anchor requires the very best components, and competitive anchors that do not meet Rocna’s standards are suggested to be inadequate due to inherent “limitations”.

Attached in the first image below is a summary of the test results from NW Labs in the form of a summary comparison of the Rocna 22# I purchased to its closest analog – the Manson 25# Supreme. The test itself is in the second image. I chose the Manson to compare to mine for a number of reasons.

First, Manson says that they use 800 MPa, 120,000 psi steel in their anchor shanks, and have published tests confirming this. The link to those test results for the Manson 25 is here: http://manson-marine.co.nz/SitePages...018Apr11VB.pdf

The second reason is that the Manson has a similar design to that of the Rocna, and shows equivalent holding power in most tests.

The third reason is that the Manson is available in North America and the U.K. I don’t have the prices of the Manson in the U.K., but in the U.S., they are significantly less expensive than the Rocna.

The final reason is that according to Ned Wood, the manager of Manson “Honestly, I have never seen or had a complaint from a customer about a bent Supreme Shank, ever. Over 12,000 sold and I am fairly sure I would have heard of something but never have heard, nor has anyone here.” Since we have pictures of bent shanks on the Rocna, something is clearly going on, so I thought a careful comparison between the two products should shed some light. I can’t verify whether Mr. Wood’s statement is true, but I did ask him if I could quote him, so I assume it is the truth.

While the test results are self explanatory, here is the punch line, in my opinion. The Manson has about 14% more steel at the mid point of its shank compared to the Rocna. Increases in cross sectional area proportionally increases resistance to lateral bending, so the Manson would be 14% stronger than the Rocna based on this measurement even if they used the same steel. However, the Manson does use 800 MPa steel for its product, so the yield strength of the Manson is about 30% greater than the lesser steel used in the Rocna. Higher yield translates directly into bend resistance, so on the basis of these two data points, the Manson is half again stronger than the Rocna at 2/3 the price.

Because the shank of an anchor represents a lever, it is possible to put high loads on the shank with lateral loading that exceeds the yield strength (bend resistance) of the steel used. The materials used in the Rocna have resulted in bent shanks; of the Manson - not so much. Presumably Rocna well understands this potential failure point and how to avoid it with the right materials. They didn’t use those materials on my anchor, so it is de facto defective and a threat to my boat. Not good.

With anchors available from manufacturers of integrity and great holding power made of appropriate materials, like Fortress, Sarca, Manson and others, it is hard to understand why anyone would pay more for less by purchasing a Rocna, especially since by their own definition, their product is unsafe. Manufacturers of safety equipment should be held to a high standard of honesty, and retailers of those products should take care when promoting products that are known to be defective.

For those who haven’t had enough punishment from this thread yet, I’ll post the details of how the Rocna was tested, as well as other photos of the test subject. I’ll be returning my Rocna to West Marine for a refund based on the simple fact that it doesn’t meet the specs advertised by Rocna. I assume they’ll give me my money back, but we’ll see.

[Delfin]

More punishment for the truly geeky:



First, some term definitions from the above report. Ultimate Tensile Strength (UTS) is the force required to break a standard sample of the steel being tested. The first image below shows the shape of the standard sample which was subjected to a pulling force with the maximum force before breaking the sample recorded as the UTS. Rocna advertises 800 MPa UTS steel, in my anchor, they used 697 MPa.

Yield Tensile Strength (YTS) is the maximum force a sample will absorb and still spring back to its original shape. This is the measurement that matters to a boater, since resistance to side loading is a function of the YTS of the shank steel. Rocna advertises 690 MPa YTS steel, in my anchor, they used 626 MPa.

Elongation is the percent the metal stretches before it breaks.

MPa are mega pascals, a metric measurement of force. The English equivalent is pounds square inch. 800 MPa equals 120,000 psi.

To test the metal, the lab cut a couple of small pieces out of the shank, embedded them in a bonding media and examined them under the microscope to determine which direction the grain of the metal ran. A picture of this test piece is in the second image. Steel develops a grain along the direction flat steel plate is rolled. It will have higher strength when the force applied is in line with this ‘grain’, so to ensure that the results we got were the maximum possible for the anchor, the direction of the grain was determined before cutting out the standard sample shown in the first picture.
The reference standard for the metal was what Rocna says they use – 800 MPa steel. This is the same steel that Manson uses, and it meets ASTM A514 standards. The reference to Bisalloy 80 on the test is because it is 800 MPa, A514 steel and is used by Manson in their manufacture.

To accurately compare the Manson to the Rocna I consulted a friend who is a structural engineer to determine what changes in lateral bending force resulted from differences in the cross sectional area of the two anchors.

The Rocna and the Manson are designed to have as much of the total anchor weight on the tip as possible. To achieve this, the shank has to be fairly thin. Even mild steel (YTS 400+ MPa) would work just fine under pulling conditions only since the chain or rope rode would generally break before the steel reached its YTS. However, the length of the shank creates a lever that multiplies the lateral pulling in a side load to the point where the shank will easily bend unless it is made out of steel with a relatively high YTS steel. The Rocna is designed for this higher grade of steel, but for reasons unknown Rocna has elected to advertise one grade and use another. The result is an unsafe anchor, whose defects will remain hidden until the boater is depending the most on the integrity of the manufacturer.

Since I am not an engineer, I welcome any correction from more knowledgeable forumites on any mistakes in my analysis.

[cheoah]

Interesting stuff, thanks for posting. Curious to see what the manufacturer says, have you contacted them? I've read much about these new anchors, is it a fair summary to say that the Rocna's are:

1) More expensive than comparable traditional anchors

2) Set faster/more consistently in a range of seabeds

3) Have produced at least one anchor (and likely more) with steel other than advertised

thanks again-

csh

[Cormorant]

Delfin, thanks for that very thorough detective work. Pretty amazing. I can't claim any knowledge of metallurgy, but so far your case seems very strong. We'll all be interested to hear Rocna's response.

Cue rebuttal from Craig in 3 . . . 2 . . . 1 . . .

[Delfin]

Originally Posted by csh

Interesting stuff, thanks for posting. Curious to see what the manufacturer says, have you contacted them? I've read much about these new anchors, is it a fair summary to say that the Rocna's are:

1) More expensive than comparable traditional anchors

2) Set faster/more consistently in a range of seabeds

3) Have produced at least one anchor (and likely more) with steel other than advertised

thanks again-

csh

CSH, I think Rocna has made their position pretty clear through Craig Smith. Unfortunately, there is a bit of a pattern here for the company that doesn't give me a lot of confidence in anything they have to say. The holding test results they tout were deeply mis-leading and didn't say what they claimed they said, they don't actually have the RINA certification they say they have, and it's clear they don't use the steel they say the do, at least in my anchor and one purchased 9,000 miles away in NZ, nor presumably in the anchors pictured as bending under normal use that are cropping up all over the place.

The solution for Rocna is pretty simple. Remove all erroneous information from their web site, stop making things up about other company's products, use the steel they say they do, communicate to their retailers that they, and their customers have been punked and will receive replacement anchors that meet specs, and then begin the process of re-building the reputation of the company.

I'm not holding my breath on that sequence of events.

I think your summary might be modified as follows:

Rocna's are:

1) 1/3 More expensive than anchors having the same holding performance who use materials that will not expose the owners to a safety risk

2) Set fast and consistently in a range of seabeds, as do other similar designs as well as designs that are significantly different than the Rocna

3) Have produced anchors that have bent under normal use apparently because of sub-standard steel incorporated into a design requiring high quality steel.

I know I am being pretty harsh on this, mostly because it appears they were intentionally cheating on your safety for the sake of their profit. I don't like that.

[ActiveCaptain]

The price of a Rocna 10 seems to be about $350. Now I really like CruisersForum and everything but I can't see myself ever spending $350 to prove something about a series of threads here. The pictures show that the anchor was completely torn apart and made to be useless.

Could you explain where the money came from? Is anyone asking you to do this analysis? Is anyone paying you to do this analysis?

For someone who claims no bias, the text that I read show an incredible bias against Rocna that go beyond the steel analysis done.

[SailFastTri]

Originally Posted by ActiveCaptain

The price of a Rocna 10 seems to be about $350. Now I really like CruisersForum and everything but I can't see myself ever spending $350 to prove something about a series of threads here. The pictures show that the anchor was completely torn apart and made to be useless.

Could you explain where the money came from? Is anyone asking you to do this analysis? Is anyone paying you to do this analysis?

For someone who claims no bias, the text that I read show an incredible bias against Rocna that go beyond the steel analysis done.

Was thinking the same. Plus the lab fees must have been much greater than that!

Not something a "normal" consumer would do. Makes no economic sense. Likely another agenda (or some sort of OCD) at play.

[s/v 'Faith']

Originally Posted by ActiveCaptain

The price of a Rocna 10 seems to be about $350. Now I really like CruisersForum and everything but I can't see myself ever spending $350 to prove something about a series of threads here. The pictures show that the anchor was completely torn apart and made to be useless.

Could you explain where the money came from? Is anyone asking you to do this analysis? Is anyone paying you to do this analysis?

For someone who claims no bias, the text that I read show an incredible bias against Rocna that go beyond the steel analysis done.

He has posted here an elsewhere for a while....

let me get this straight... you doubt his motives simply because he wanted to test a Rocna and get his own answers?

[ActiveCaptain]

Originally Posted by s/v 'Faith'

let me get this straight... you doubt his motives simply because he wanted to test a Rocna and get his own answers?

I think it is extremely odd that anyone would go to this level of expense to test something that isn't appropriate for their own boat in any way.

[witzgall]

What strikes me odd is that the test results you posted say *Failed to meet minimum specified.

What was the minimum, specified where, and by whom? Did you provide them with the numbers you were expecting before the test? Why would you do that?

Also, do you really expect West Marine to give you your money back, on a product intentionally destroyed?

I am not going so far as to question your motives, but thought those two points warranted a comment.

Chris

[cwyckham]

Originally Posted by witzgall

What strikes me odd is that the test results you posted say *Failed to meet minimum specified.

What was the minimum, specified where, and by whom? Did you provide them with the numbers you were expecting before the test? Why would you do that?

Also, do you really expect West Marine to give you your money back, on a product intentionally destroyed?

I am not going so far as to question your motives, but thought those two points warranted a comment.

Chris

He stated in his post that he told the testing house that it was specified as 800 MPa, so they tested against that (that value is shown on the report from them). Actually, I'd expect my money back too if I bought something and then found out it wasn't as advertised. In fact, I believe there's a legal requirement to supply a product that matches what you represented. Rocnas are represented as having 800 MPa shanks. If his didn't, he should be able to get his money back.

[witzgall]

I asked the first question because it seems to be that if the test would be the most credible if the testing house was not told what values were being sought. Is that required, for technical reasons? If I was going to pay somebody to do destructive testing on a product, on my own dime, and I knew that a failed test would look bad for the product company - and I was going to publish it for the world to see, I would have done whatever I could do to make it look as impartial as possible. Was there some sort of control material tested at the same time, for instance?

I don't know enough about this sort of thing to know what constitutes a fair test. Does anyone know how this sort of thing should be handled, so that the test results can be taken by the general public to be valid?

Chris

Originally Posted by cwyckham

He stated in his post that he told the testing house that it was specified as 800 MPa, so they tested against that (that value is shown on the report from them). Actually, I'd expect my money back too if I bought something and then found out it wasn't as advertised. In fact, I believe there's a legal requirement to supply a product that matches what you represented. Rocnas are represented as having 800 MPa shanks. If his didn't, he should be able to get his money back.

[markpierce]

Originally Posted by ActiveCaptain

I think it is extremely odd that anyone would go to this level of expense to test something that isn't appropriate for their own boat in any way.

Odd? Don't you mean courageous?