GrantKing
New member
Supply to Spain prior to mid 2009 was from Boyd Boats ( UK distributor) to Spain and was all Chinese stock of 420 shanked units
Rocna Anchors acquired by Canada Metal Pacific
- Thread starter Laura Nineham
- Start date
Supply to Spain prior to mid 2009 was from Boyd Boats ( UK distributor) to Spain and was all Chinese stock of 420 shanked units
GrantKing
New member
Simply use blutack to hold the ball and the bolt in place while you place it in the vice...and easy solution
Neeves
Well-known member
Someone who does this sort of thing daily, steel maker, was less anthusiastic about the idea of grease, or blutac - they thought it might influnece results. Doing it dry removes the issue.
Personally I have no idea, about blutak or grease.
Jonathan
Personally I have no idea, about blutak or grease.
Jonathan
vyv_cox
Well-known member
If the test was being done on a machine according to specification then it should not be lubricated. For a comparative test it would normally be done dry but as the lubricant has the same effect on both sample and standard I guess it should be OK. Bluetack seems like a good idea. Mine was done with grease, and I used a cut sample of shank, so it wasn't as difficult to position and balance as Jonathan's.
Neeves
Well-known member
Ex Solent Boy
You were querying the bending of a 420 anchor. I am glad you made the comment - the results were interesting.
In brief, and so as not to upset the publisher who has commissioned an article:
I have an ungalvanised 10kg Chinese Rocna, ex Linox. I'm guessing its from an (the) early production, as Linox were unceremoniously discarded in mid 2009. So it must come prior to mid 2009. I am unable to corroborate when it was made, other than comment from Linox. You will recall Brian Bambury confirmed a change of shank spec in Oct 2008 and this was confirmed by the factory, in Dec 2008, to be 420 for the first production run, of 844 anchors. One anchor, from this 844, that has been tested by an independent laboratory and was found to be a '400' quality. 300 of these early anchors came to the UK. The anchor independently tested was one that bent in the Bahamas.
I have conducted Vyv Cox' test on the shank of the (my) 10kg 'Linox' anchor and its a 400/420 shanked model. I cannot differentiate between 400 and 420. But its not 620, HSLA nor Bis80. The fluke is embossed with 'genuine Rocna' etc.
I drilled holes in the fluke and restrained it with masonary bolts in a reinfoced concrete pad. I stressed it using a 'chain' block and tackle (I think the block and tackle with chain has a name but do not recall but think its a 22:1 advantage). The end of the block and tackle was held by a chain to a reinforced concrete pillar. Basically the fluke and pillar were fixed. I used a normal shackle in the shackle hole in the shank. The load was applied at 90 degrees to the shank axis. The fluke was approximately horizontal.
I used a 2t load cell, I check the calibration by filling 200 litre drums with water. The display is accurate to 0.1kg.
I was a bit over-enthusiastic and stressed it initially to 134kg and found a minor, permanant bend, maybe 1 degree. What was extraordinary, to me, was the amount of elasticity, maybe 15 degrees. To produce any real and noticeable bend I needed to stress it toward 200kgs and at this level I was able to achieve a permanent 10/15 degree bend. To achieve the result I simply stressed in approx 20kg increments, took images, dropped the stress to zero, took images and re-stressed to plus 20kg etc. I am assuming, given that the model I had perfomed better than the theory (maybe my lever arm is incorrect?), possibly without validity, that a Bis80 shank would not have noticeable deformed until I applied a 300kg load, or thereabouts. (Sadly I do not have Bis80 shanked 10kg Rocna, otherwise I might try it!)
Theoretically
This 10kg anchor had an 11mm shank, the specification calls for 10mm
Assuming my arithmetic is upto scratch then: Based on the 11mm the load necessary to bend a:
450MPa shank is 154kg
420MPa shank is 143kg
357MPa shank is 122kg
690PMa shank is 236kg
357MPa shank (of 10mm) is 101kg
357MPa is the yield strength of the Bahamian anchor (and presumably some others of the 844 in the first shipment).
I worked on a 'lever' arm of 531mm - this might not be correct, but its the distance between the stress point and the inner surface of the 'thinnest', 90mm, point of the shank, just above the fluke. Theory is based on a straight 'shank' the Rocna, as with most anchors has bends in the shank - the theory does not account for the bend (but in the arithmetic calculations - its relative).
I now have a 10kg Rocna with a 10/15 degree bend in the shank. It looks not unlike the shank of the anchor bent in the Bahamas. When Sydney's weather looks less like Manchester's weather I'll try to set it.
If it sets with the current bend I might then re-stress until it does not set.
Again thanks to 'Ex Solent Boy' for providing motivation for the work.
Jonathan
You were querying the bending of a 420 anchor. I am glad you made the comment - the results were interesting.
In brief, and so as not to upset the publisher who has commissioned an article:
I have an ungalvanised 10kg Chinese Rocna, ex Linox. I'm guessing its from an (the) early production, as Linox were unceremoniously discarded in mid 2009. So it must come prior to mid 2009. I am unable to corroborate when it was made, other than comment from Linox. You will recall Brian Bambury confirmed a change of shank spec in Oct 2008 and this was confirmed by the factory, in Dec 2008, to be 420 for the first production run, of 844 anchors. One anchor, from this 844, that has been tested by an independent laboratory and was found to be a '400' quality. 300 of these early anchors came to the UK. The anchor independently tested was one that bent in the Bahamas.
I have conducted Vyv Cox' test on the shank of the (my) 10kg 'Linox' anchor and its a 400/420 shanked model. I cannot differentiate between 400 and 420. But its not 620, HSLA nor Bis80. The fluke is embossed with 'genuine Rocna' etc.
I drilled holes in the fluke and restrained it with masonary bolts in a reinfoced concrete pad. I stressed it using a 'chain' block and tackle (I think the block and tackle with chain has a name but do not recall but think its a 22:1 advantage). The end of the block and tackle was held by a chain to a reinforced concrete pillar. Basically the fluke and pillar were fixed. I used a normal shackle in the shackle hole in the shank. The load was applied at 90 degrees to the shank axis. The fluke was approximately horizontal.
I used a 2t load cell, I check the calibration by filling 200 litre drums with water. The display is accurate to 0.1kg.
I was a bit over-enthusiastic and stressed it initially to 134kg and found a minor, permanant bend, maybe 1 degree. What was extraordinary, to me, was the amount of elasticity, maybe 15 degrees. To produce any real and noticeable bend I needed to stress it toward 200kgs and at this level I was able to achieve a permanent 10/15 degree bend. To achieve the result I simply stressed in approx 20kg increments, took images, dropped the stress to zero, took images and re-stressed to plus 20kg etc. I am assuming, given that the model I had perfomed better than the theory (maybe my lever arm is incorrect?), possibly without validity, that a Bis80 shank would not have noticeable deformed until I applied a 300kg load, or thereabouts. (Sadly I do not have Bis80 shanked 10kg Rocna, otherwise I might try it!)
Theoretically
This 10kg anchor had an 11mm shank, the specification calls for 10mm
Assuming my arithmetic is upto scratch then: Based on the 11mm the load necessary to bend a:
450MPa shank is 154kg
420MPa shank is 143kg
357MPa shank is 122kg
690PMa shank is 236kg
357MPa shank (of 10mm) is 101kg
357MPa is the yield strength of the Bahamian anchor (and presumably some others of the 844 in the first shipment).
I worked on a 'lever' arm of 531mm - this might not be correct, but its the distance between the stress point and the inner surface of the 'thinnest', 90mm, point of the shank, just above the fluke. Theory is based on a straight 'shank' the Rocna, as with most anchors has bends in the shank - the theory does not account for the bend (but in the arithmetic calculations - its relative).
I now have a 10kg Rocna with a 10/15 degree bend in the shank. It looks not unlike the shank of the anchor bent in the Bahamas. When Sydney's weather looks less like Manchester's weather I'll try to set it.
If it sets with the current bend I might then re-stress until it does not set.
Again thanks to 'Ex Solent Boy' for providing motivation for the work.
Jonathan
Twister_Ken
Well-known member
Even now, someone at Rocna/CMP is writing a press release describing the 'deliberate' bending potential of the shank, such that in high winds a bend is induced which allows the anchor to screw itself into the seabed, thus saving the ship.
Probably called SSHP, Super Screw Holding Power.
Not to be confused with Super Screw-up Hanky Panky.
Probably called SSHP, Super Screw Holding Power.
Not to be confused with Super Screw-up Hanky Panky.
Morven
New member
As I said before: Bottom Adaptive Geometry! 
Ex-SolentBoy
New member
If an anchor is stuck in a rock, or something, a load is transmitted at an angle and I would expect it eventually to bend. Clearly Jonathan's test is helping to understand at what point this bend occurs.
For normal useage though, say when an anchor is embedded in mud or sand, wouldn't it swivel long before it bends? Aren't anchors designed to swivel until the load is directly in line with the shank?
The reason I ask is that I am trying to understand if this bendy shank thing is such a problem after all. If your anchor is stuck in a rock, whether it bends or not is hardly the biggest issue. In many respects it might be better if it bent and came unstuck than stayed stuck permanently. In the latter you might have to ditch the chain as well.
For normal useage though, say when an anchor is embedded in mud or sand, wouldn't it swivel long before it bends? Aren't anchors designed to swivel until the load is directly in line with the shank?
The reason I ask is that I am trying to understand if this bendy shank thing is such a problem after all. If your anchor is stuck in a rock, whether it bends or not is hardly the biggest issue. In many respects it might be better if it bent and came unstuck than stayed stuck permanently. In the latter you might have to ditch the chain as well.
Twister_Ken
Well-known member
Lest we forget...
The original rationale as espoused by Peter Smith was to use Bis80 (strong) so that the shank could be made thin, thus as light as possible, putting the max weight on the anchor's tip, to aid rapid penetration (oo-errr).
To match the strength of Bis80, weaker materials would need to be thicker (=heavier) thus making penetration more difficult to achieve.
The original rationale as espoused by Peter Smith was to use Bis80 (strong) so that the shank could be made thin, thus as light as possible, putting the max weight on the anchor's tip, to aid rapid penetration (oo-errr).
To match the strength of Bis80, weaker materials would need to be thicker (=heavier) thus making penetration more difficult to achieve.
misterg
Active member
Empirical evidence suggests that this is true for the original design (no bent anchors reported), but not for the ~4?0MPa shanks (several bent anchors reported) - the "Venice Anchor" was allegedly set in sand and not jammed on anything, depending on who you believe (there is a wide choice) - post#1759.
(Interesting result for Danny-Jo's anchor- I was puzzled by the results of his punch test, but all is now clear.)
....I can't believe I'm posting on this thread again
Andy
G12
Member
I can't believe this thread is still going! Surely it's easier to just go and buy an anchor you're happy with? I think I am correct in saying that nobody is forced to buy a Rocna.....
Neeves
Well-known member
Ex Solent Boy
I confess to have never used a Rocna as an anchor, tested it yes but never actually anchored). However I have used a Spade, Excel, SARCA and Supreme. One thing they all have in common is that if they are well set, you set with the engines in reverse or you enjoyed a fairly strong breeze, then when you come to lift them you need time. Simply put you will drag your bow down and your windlass will struggle (might even throw the circuit breaker). The only way to lift these modern anchors is to sit vertically over the anchor and let wave movement slowly break the anchor free.
In terms of the load on the shank at 90 degrees. Once the enchor is set it is actually very difficult to know how it is oreintated (come the following morning) and when lifting it would be very easy to lift it at an angle. The simply driving of the yacht forward, impatiently trying to lift it, might generate enough momentum to bend it - and given that Venice is meant to be mud and sand my money might be on that scenario. Though anchors should be built to withstand that level of momentum.
But think of being at anchor in one of those places that is sheltered but prone to large down drafts, or bullets from unpredictable directions or think of a storm cell passing over. The anchor will not have time to re-orientate. It can easily then be stressed at an angle to the shank direction. Not common but something many people will experiance. As a topical example, go to May 2012 YM, page 38, Loch Scavaig (bottom of second column and top of third). We have the same here at Refuge Cove, Wilson's Prom under SW Storms - so not unusual. Your yacht might not end up on the beach - but imagine lifting your Rocna at Loch Scavaig and finding it bent, tell me what would you do? and how would you feel. Wife and 2 kids looking at you for leadership - not a happy scenario.
The idea that anchors are designed to swivel - sadly its not a feature I recall being high on the attributes advertised of any anchor. In fact its not an attribute I recall being mentioned at all. Virtually all tests are straight line pulls. There are moves in the media to right this wrong but its incredibly time consuming as you need to do the straight line pull, to set the anchor, then reset the 'thing' you are using to generate the load at 90 degrees and then re-pull. You really need to test each anchor 3 times (it took us all day to test 8 anchors once!)
Finally no-one is forcing, or forced, anyone to buy a Rocna. Its the ones out there with off spec Rocnas on bow rollers that are unaware of the problem that are the issue. Basically only YM and this forum (brief mentions from PBO, ST, Segeln and Practical Sailor in America) that have tried to advertise the issue. sadly not everyone reads YM and most, understandably, do not read this thread. Maybe its a task for CMP or Rocna themselves (who still do not admit to the 400 odd offspec anchors proved to have come to the UK prior to the 50 they do accept). Go back in this thread only a few days and you will read of chandlers in Iberia who have no idea there is an issue at all!
Jonathan
I confess to have never used a Rocna as an anchor, tested it yes but never actually anchored). However I have used a Spade, Excel, SARCA and Supreme. One thing they all have in common is that if they are well set, you set with the engines in reverse or you enjoyed a fairly strong breeze, then when you come to lift them you need time. Simply put you will drag your bow down and your windlass will struggle (might even throw the circuit breaker). The only way to lift these modern anchors is to sit vertically over the anchor and let wave movement slowly break the anchor free.
In terms of the load on the shank at 90 degrees. Once the enchor is set it is actually very difficult to know how it is oreintated (come the following morning) and when lifting it would be very easy to lift it at an angle. The simply driving of the yacht forward, impatiently trying to lift it, might generate enough momentum to bend it - and given that Venice is meant to be mud and sand my money might be on that scenario. Though anchors should be built to withstand that level of momentum.
But think of being at anchor in one of those places that is sheltered but prone to large down drafts, or bullets from unpredictable directions or think of a storm cell passing over. The anchor will not have time to re-orientate. It can easily then be stressed at an angle to the shank direction. Not common but something many people will experiance. As a topical example, go to May 2012 YM, page 38, Loch Scavaig (bottom of second column and top of third). We have the same here at Refuge Cove, Wilson's Prom under SW Storms - so not unusual. Your yacht might not end up on the beach - but imagine lifting your Rocna at Loch Scavaig and finding it bent, tell me what would you do? and how would you feel. Wife and 2 kids looking at you for leadership - not a happy scenario.
The idea that anchors are designed to swivel - sadly its not a feature I recall being high on the attributes advertised of any anchor. In fact its not an attribute I recall being mentioned at all. Virtually all tests are straight line pulls. There are moves in the media to right this wrong but its incredibly time consuming as you need to do the straight line pull, to set the anchor, then reset the 'thing' you are using to generate the load at 90 degrees and then re-pull. You really need to test each anchor 3 times (it took us all day to test 8 anchors once!)
Finally no-one is forcing, or forced, anyone to buy a Rocna. Its the ones out there with off spec Rocnas on bow rollers that are unaware of the problem that are the issue. Basically only YM and this forum (brief mentions from PBO, ST, Segeln and Practical Sailor in America) that have tried to advertise the issue. sadly not everyone reads YM and most, understandably, do not read this thread. Maybe its a task for CMP or Rocna themselves (who still do not admit to the 400 odd offspec anchors proved to have come to the UK prior to the 50 they do accept). Go back in this thread only a few days and you will read of chandlers in Iberia who have no idea there is an issue at all!
Jonathan
GrantKing
New member
Empirical evidence suggests that this is true for the original design (no bent anchors reported), but not for the ~4?0MPa shanks (several bent anchors reported) - the "Venice Anchor" was allegedly set in sand and not jammed on anything, depending on who you believe (there is a wide choice) - post#1759.
(Interesting result for Danny-Jo's anchor- I was puzzled by the results of his punch test, but all is now clear.)
....I can't believe I'm posting on this thread again
Andy
Post #1760 tells exactly how it happened despite what CMP and Smith care to profess.
The original email file relating to this incident is being provided to Neeves and includes the source code in order to be verified as genuine. Electronic stamps on emails cannot be fabricated, unlike the continued misinformation being perpetuated in order to minimise the extent of the potential problem of bending.
Ex-SolentBoy
New member
Exactly. You assumed the anchor was trapped by something on the seabed as opposed to simply buried. That's my point.
Ex-SolentBoy
New member
Jeeves
Its a nice long post , but it doesn't answer the question. Yes, it wouldn't be nice to have a bent anchor, but in the scenario you mention I would simply fit my spare and sort the problem out when ashore.
My question was whether anyone had bent a Rocna without snagging it on something. The assumption made in the Venice incident was that it was snagged. Was that proven correct? I guess we will never know as no one dived on it.
I am not saying there are no weak shanked Rocnas. I am only questioning how big a problem it really is if they do not bend in normal useage. Surely by now there would be a load more warranty claims if that we're the case?
Its a nice long post , but it doesn't answer the question. Yes, it wouldn't be nice to have a bent anchor, but in the scenario you mention I would simply fit my spare and sort the problem out when ashore.
My question was whether anyone had bent a Rocna without snagging it on something. The assumption made in the Venice incident was that it was snagged. Was that proven correct? I guess we will never know as no one dived on it.
I am not saying there are no weak shanked Rocnas. I am only questioning how big a problem it really is if they do not bend in normal useage. Surely by now there would be a load more warranty claims if that we're the case?
Seven Spades
Well-known member
What we know is Bis80 = Good
Q400/420 = Bend
Q620=?
What we don't really know is if Q620 is up to the job or not. All anchors will eventually bend if stuck in a rock in which case the boat probably isn't going to move, but when you do free it the anchor will be useless.
I suspect that in normal usage the Q620 will work as good as nearly all other anchors. Some will use Bis80 on only a couple on the market do the rest will use a lower grade metal although no on here is questioning that.
The jury is still out on Q620 but as far as I can see there are no reports of failures of Q620 anchors.
The main problem is one of identification. CMP should immediately change the embossing to make it absolutely clear that any new anchors are CMP versions.
Q400/420 = Bend
Q620=?
What we don't really know is if Q620 is up to the job or not. All anchors will eventually bend if stuck in a rock in which case the boat probably isn't going to move, but when you do free it the anchor will be useless.
I suspect that in normal usage the Q620 will work as good as nearly all other anchors. Some will use Bis80 on only a couple on the market do the rest will use a lower grade metal although no on here is questioning that.
The jury is still out on Q620 but as far as I can see there are no reports of failures of Q620 anchors.
The main problem is one of identification. CMP should immediately change the embossing to make it absolutely clear that any new anchors are CMP versions.
Ex-SolentBoy
New member
Is a slightly bent anchor really useless?
FishyInverness
New member
No, but in the same way that a slightly corroded brakeline isn't useless....
GrantKing
New member
Yes I did assume that because at that point I was not aware that it was 420 shanked and expected it to be Bis80.
This was the start of the revelation and coverup of the change of metal.
Chris_Robb
Well-known member
According to Smith, they need to be absolutely symmetrical to pull in, otherwise they corkscrew.