Rocna Anchor Fail

[klem]

I agree with everyone who doesn't like the marketing that Rocna has done but continue to be extremely happy with the anchor that I have (a suncoast built one).

Has anyone actually determined whether it matters what the yield strength and ultimate tensile strength is for these anchors? The lowest yield strength for Rocna was 39 KSI (converting for those of us more used to crummy ips units) which isn't too bad for cast steel. There were yield strengths all the way up over 120 KSI which is pretty close to the upper limits of many types of steel before you have to worry about brittle fracture unless special treatments are done. Even these numbers do not matter, what matters is whether the anchor is likely to fail.

There are a lot of us engineers on the board, has anyone done a simple analysis to determine what the expected stress is in the materials? I am imagining taking the worst case loading (tip hooked on a rock) and applying a force from the chain and then seeing what the stress is. My guess is that the stress is way below any material limits. Even if you made really worst case fatigue and corrosion assumptions, it is most likely fine. It might be informative to do some analysis of veering as well. Sorry, I don't have time to do this myself right now, has anyone else done it?

[Tripod]

I've seen this before . . . .

For the record, I have a Manson Supreme, a Fortress, a Bruce, and two Danforths. When I chose the Manson, I was put off the (pre-China) Rocna by Rocna's marketing more than differences in quality or performance.

All these anchors do well if used correctly. Any anchor can fail under the right conditions. What matters is how the manufacturer deals with a failure.

A long time ago, on my parent's boat, we ripped a fisherman anchor into three pieces in a wind shift off Lahaina. That anchor was at least 20 years old and the manufacturer replaced it, no questions asked.

[CSY Man]

According to the Rocna snippet the shank material has a tensile of ~120,000 psi. The test coupon from the Manson website shows the shank tensile to be ~69,000 psi.

Hmmmmm, now I really wish somebody from Rocna would pipe up and say something. If Craig is away sailing or whatever, perhaps we should send a link to this thread over to the Rocna camp to make sure they get a chance to defend 'emselfs..

[capn_billl]

Originally Posted by David_Old_Jersey

That's why folks carry spare Anchors. and don't believe all advertising.........

That says it right there.

It seems to me that there is no perfect anchor. If it has large wide flukes, it will hold well in soft bottoms and mud, but have difficulty digging in on hard bottoms, and weeds.

If it has a sharp pointy bit, it will penetrate weeds, and hard bottoms, but not hold well in mud or loose sand.

Every anchor I've seen is a compromise between these two designs.

From an engineering perspective, "no anchor will stop your boat".

They provide a resistance, (friction) vs the force applied by the drag of the moving water and wind against the surface area of your hull, and rigging. Friction as a force only slows movement it does not stop. Unless snagged against a pipe, or coral while anchored and in the force of moving water and wind your boat is moving, (although it may be inches per day), as long as sustained winds or waves are coming from a consistant direction. The speed of the movement is inversely proportional to the mass of the displaced dirt being held times the total force applied. Experiments have shown the magnitude of the force can be several thousand pounds,.. so to keep movement to a reasonable amount, the anchor has to grip at least several thousand pounds of dirt. The harder the bottom, (more viscous), the slower the movement, and the less volume needs to be displaced to give equivalent creep. The density of dirt, (average as density varies with composition), is 120 lbs per cu foot, the density of sand is slightly less at 100 lbs per cu foot. So it would seem that the anchor should displace at least 10 cu foot of bottom to be effective at average boat sizes under moderate conditions.

AN anchor buried just to the top of the flukes with a 1 to 1 rode, (10ft rope at 10 ft depth), that has a single fluke 1 foot wide, and 2 ft long, would only have a holding power of 200-240 lbs in wet sand. A danforth design with two flukes would have a holding power of 400-480lbs in this situation.

A little more rode to a 10 to one scope, 2 * tan(^cos(10/100)) = 9 ft^2 gives 900 - 980 lbs or 1800 to 1960 lbs with the danforth.

The same anchor buried to the top of the shank would displace the volume of 2 ft^2 * (2 * sin45 * sqrt(2 *(4^2)) - (2 * sin45 * sqrt(2 *(4^2)) * density of mass displaced = 1200lbs.

A danforth may not penetrate to this depth in hard packed sand due to the limited angle of attack. But if it did it would give you 2400lbs.

The practical limits as I see them are increasing rode to at least 10 to 1 gives a big mechanical advantage as the lower the angle of attack the more dirt has to be displaced to pull the anchor free, (see tan curve), the downside is this curve goes to infinity, (8000mile rode anyone??), the second is assuming a hard enough bottom that the material displaced does not flow to the sides and escape, in soft mud a poor assumption, after (10 to 20) to 1 doubling rode only gives an increasingly smaller gains.

Second depth of penetration is an important factor that plow and spade anchors have an advantage in, that offsets their relatively small surface area in cases the bottom is rigid enough to resist flow.

An unbiased rule for anchor design would be 1. Area of flukes by size, (weight?). 2. Angle of attack 3. Force of penetration, (mass * specific gravity divided by area of leading edge) in pounds per sq inch. 4. Breaking & bending strength from point to ring on all three axis.

Any way that is my "lunch hour" analysis. I hope it illuminates, and feel free to critique.

[David_Old_Jersey]

I had a few run ins over the years with "Craig" of Rocna - albeit the "good stuff" was obviously on other forums .........but to be fair, in recent years he does seem to have become rational - I am guessing it is a different person(s) behind that name, realised how internet forums work (and stopped setting himself up for abuse )...........or he started taking his Meds

But nonetheless I long ago decided not to buy anything from a raving lunatic - and that includes something that I would rely on for a good nights kip.

[GMac]

This somewhat shocking revelation is only in relation the the Chinese made Rocnas. The ones with the name cast into the back of the foot. The Suncoast and NZ made ones don't have the name there and are made with good strong steels.

I wouldn't say this is a 'dodgy china made' thing. Yes they make some rubbish but they also make good stuff, if you want to pay for it that is. With items like this they will make to the exact specification you say with the exact material you say. What grade steel to use would have been specified by Holdfast, the Banburys company (Brian the owner and son Steve the CEO) that holds the rights to market the Rocna worldwide. The Chinese will be making exactly what they were told to make using what they were told to use, including steel quality.

Does this make the anchor dangerous?? For most I'd think No it doesn't as they just won't be pushing it that hard anyway. For some who do push their gear or have minimum sized gear, maybe. I doubt the anchor will fly to bits but it may change shape and become suddenly ineffective if loaded highly.

I don't know what the effects or possible downsides of the noted 'appear to be casting defects' maybe but my laymans head is thinking, not good at all.

Most countries have laws saying you can't sell something that is considerably different, in this case weaker, than advertised so if this makes you nervous about your Rocna speak to the local seller about a refund. I suppose that's about your only recourse.

While here I think, and in an unusual twist, I may have to stick up for Craig a bit. We have had many a head bash about his continual and what I regards as often suspect marketing methods not to mention continual banging on about all other anchor makers producing sub-standard gear. I do know he has been a right pain in the bum for the Banburys by constantly going on about holding the quality high. I suspect both Craig and Peter have had the wool pulled over their eyes, just like everyone else has, regarding the use of well below promoted steel strength being used. I do know Peter has always been very finicky about quality and keeping it 'up there'.

I do find it quite ironic that after years for Rocna continually rubbishing every other anchors design and build quality, it is actually the Rocna that has been found to be built well below what they say it is, in the area they say is highly important and most of the very competitors use that they have been attacking.

It's shame really as the design is a goodie for sure. To now find that they are being built out of low strength steel I find quite sad really. And at the same time damn annoying as we feel for the marketing tripe also and in doing so sold many on the premise they were strongly built.

[Factor]

Originally Posted by Joli

Disclaimer; my conversion from metric to english could well be wrong, if so, my apoligies. Could someone back check me?

Dunno about your maths but semantically you have a problem, Metric is a measurement system, english is a language or cultural heratige. I think you mean Metric to Imperial. (thought some levity would be good here)

[S/V Alchemy]

Originally Posted by GMac

It's shame really as the design is a goodie for sure. To now find that they are being built out of low strength steel I find quite sad really. And at the same time damn annoying as we feel for the marketing tripe also and in doing so sold many on the premise they were strongly built.

It would be foolish indeed to call the Rocna a bad anchor. Failures would abound in the real world as well as the "test bed" world, and that is not the case. Rocna may not be, however, as the more critical analyses are tending, the best anchor by a wide margin, as they have perennially claimed with notable boorishness, but perhaps not even the best anchor at all. Whether this is due to intrinsic design elements that are simply not as effective as claimed, or in concerns over manufacturing specs and practices, remains to be seen.

Doesn't mean it's bad. Not at all. But it does imply that it's got a lot of company in the top tier, and, as expected, there may be different anchors that do better in some situations than Rocna. I doubt, however, that the rampant slagging can continue no matter what is demonstrated. Their next model should be called the "Rocna Hubris". No matter how deep it digs, it can't hold on to honour.

[markpierce]

Originally Posted by sarafina

However on this thread the light at the end of the tunnel is NOT the train comin... it's my gimlet eye * -)

I've found the end of the tunnel.

[s/v 'Faith']

Gmac,

I am glad to hear from you in this thread. In sorting the feathers from the fluff, you (and Maine Sail) are a couple of the most credible.

I agree, that even the 'weaker then advertised' rocna (or a cinder block for that matter) will probably hold most boats...

Originally Posted by GMac

.....I do find it quite ironic that after years for Rocna continually rubbishing every other anchors design and build quality, it is actually the Rocna that has been found to be built well below what they say it is, in the area they say is highly important and most of the very competitors use that they have been attacking.....

Me too... this is the thing that strikes me. Marketing I can understand, I DO believe the 'new generation' anchors are an improvement... I don't think anyone using reasonable prudence, and needs to loose sleep.,,, it is Ironic just as you say.

[sailorboy1]

Originally Posted by markpierce

I've found the end of the tunnel.

That's not the end of the tunnel, just my flashlight

While CS has turned me off of Ronca, I wouldn't say it is a bad anchor. And that made in China thing isn't an issue. People have been saying stuff is crap because they were made in X (fill in a country name) for years just because of whatever.

And even if the metal is weaker, if it comes down to this you are probably in a lot bigger trouble.

Let's all be real!

[GordMay]

Originally Posted by Don Lucas

... And that made in China thing isn't an issue. People have been saying stuff is crap because they were made in X (fill in a country name) for years just because of whatever...

And, they’ve often been as right, as any* stereotypical generalization can be.
And, given time & progress, will some day be no longer true; just as with those earlier "X"s.

Why, for example, is ‘birds lay eggs’ true, while ‘birds are female’ is false? It is, after all, only the female birds that lay eggs.
Why is ‘mosquitoes carry the West Nile virus’ true, and ‘books are paperbacks’ false; given that less than one percent of mosquitoes carry the virus while over eighty percent of books are paperbacks?

[Joli]

Therein lies the problem, I are an engineer.

Seriously though; Rocna advertises the importance of making a shank with only high strength steel with subsequent heat treat to make it tough and strong only to discover it isn't?

Rocna advertised: 800 Mpa ~ 120,000 psi
Rocna as tested: 464 nmm2 ~ 67,000 psi

If Rocna feels a heat treated, high strength shank is important to the design of the anchor they should,,, maybe make the anchor with a high strength shank?

Having dealt in China for many years it is very easy to see how this happens. Maybe someone from Rocna should have been pulling testing cuopons from random samples prior to releasing funds to the maker?

Just saying.............?

Originally Posted by Factor

Dunno about your maths but semantically you have a problem, Metric is a measurement system, english is a language or cultural heratige. I think you mean Metric to Imperial. (thought some levity would be good here)

[Capitain Mike]

I am in the market for a new anchor and I am in Greece and so I have been studying the forums for weeks and not only on this one. I have found that you can't go by websites you don't know who owns what sites.

I have looked at Spade, Spade I don't know if it exists anymore the information from them stopped after 1 mail about Oceane, Sword, (Oceane and Sword do not exist anymore),

I made a Spade template it came from their website. The size recommended was enormous, I think because their length dimensions do not work to well with their weight values so they are pushing you towards a heavier anchor.

It was to large altogether my boat is only 8.68 metres and is 3.58 tons unladen add another ton for crew fuel food water outboard and all the bits and bobs. The Spade anchor recommended was for a 6 ton boat. Goodbye Spade.

Spade told me that their sword anchor was still available in a few sizes but not the complete range. Following my reply to Spade requesting price, carriage and availability I heard no more. Goodbye Sword

Oceane was taken over by Spade and Ocean anchors are no more.

Buegel from Germany (patent expired) is now WASI Bugel it was supplied with its powerball chain connector but everywhere I went it is now an extra. Very Very large and expensive.

WASI Buegel very hard to get hold of an original WASI Buegel VERY similar in many ways to Spade I did not like the write ups on the WASI Buegel though I know several people who have one and swear by them. There is one on a 30ft Sail boat in the local port now, but it is so large it cannot be brought in onto the foredeck over the bow roller. it just sits there with the powerball on the bow roller and swings.

Ultra, Ultra only do stainless steel and were in USA, that ruled them out.

Rocna and Manson, both very similar in design but Rocna always knocking Manson on the Forums as you all know very well.

Rocna's Mediterranean distributors are in Greece and Italy, Greece is Levkas in Lefkada in the Ionian me I am in the Cyclades.

I did not want to use the distributor in Levkas as I have used them before and I felt the results of our meeting left me in a very were undesirable position the reasons I won't go into here.

I contacted their Italian Distributor

I had mailed Rocna and told them and they suggested thie other distributor in Italy Indemar S.p.A.
So next stop was Italy,

The company Indemar S.p.A. Their email
Following to your request, please find here after our offer for:
1 x Rocna anchor 10kg. galvanised
Net price: Euro 265,00+20%VAT
Delivery time: at stock, subject to prior sales
Delivery terms: ex works (Incoterms 2000)
Transport costs with our courier TNT: Euro 153,00+20%VAT
Package: included
Payment: anticipate bank remittance

Looking forward to hearing from you soon,
Best regards

Cinzia Buffa
Indemar S.p.A.
Via Guido Rossa 42
16012 Busalla (GE)
Tel. +39 010 9641927
Fax +39 010 9641920
home
cbuffa@indemar.com

They wanted €153.00 + 20% VAT for the carriage alone, of a 10kg Rocnar and I would be responsible for the anchor as and when it left their premises with their courier TNT.

I mailed Rocna but they could not/would not help. I could buy the same anchor in UK and the carriage would be £35.00 to my home in Greece.
So no way would I purchase from them so goodbye Indemar and Rocna.

Meanwhile I was still scouring forums and websites for information. If you are a serious sailor and you’re not always tied up in a marina then your anchor is a very very important piece of equipment.

Manson were/are, I am still in contact very helpful both their MD Steve Mair and their VP/Sales & Marketing - Ned Wood could not do enough to help me. Polite, efficient, helpful and understanding, In my eyes Their Service makes them stand out above them all. Looking at their new website especially.
Independent metallurgic tests of both Manson and Rocna

Manson Anchors: Supreme Anchor high standards

Manson Anchors: the world's finest stainless steel and galvanised anchors
Manson Anchors: The world's leading anchor manufacturer
The Manson Supreme independent test results
Manson Anchors: Supreme Anchor high standards

I don't know if I have made complete sense. I am not saying that one anchor is better than another anchor you must draw your own conclusion I have only written here my findings as I see it. Remember “The customer is King”. Their profit is in your pocket you can always go somewhere else.

I have purchased a Manson.

I wish to add that I have no affiliation in any way directly or indirectly whatsoever with any of these companies.

[Dockhead]

Originally Posted by Kettlewell

I understand there may be some issues with regard to claims vs. reality in terms of material strength, but I do not have enough knowledge to know if these numbers are significant. In other words, as long as both anchors are strong enough, extra strength doesn't really matter other than bragging rights. Personally, I have always been a bit wary of all of these anchors that use a flat plate steel shank. You would think they would all be vulnerable to bending if the anchor was dug in sufficiently and the wind shifted direction. I have seen several examples of various anchors that have had bent shanks, so those types of loads are not impossible, though they must be rare. For that matter, I've seen several drop-forged CQR shanks that have been bent, and those things must be tremendously strong.

I believe that shanks get bent when anchors are stuck in rocks. In a normal bottom the forces required to turn in the anchor in the sea bed are much less than what will bend a shank of any reasonable material.