Plastimo Kobra Anchors

Since this thread has used results from anchor tests, I would like (having been involved in field trials, though not ones relating to anchors) to state the obvious.
Different tests give different results for the same anchors. Given the number of variables involved, it's hardly surprising. Also, the results from tests do not always reflect real-life experience (the CQR being an obvious example - maybe it's no longer the best yacht anchor, but it still does the job for many users despite generally woeful results on various tests).
Which is not to say that tests are useless - each one gives some information and the results from many tests can be combined with experience.
What I don't think is reasonable is to say, on the basis of one test "Anchor A held up to an applied force of x kg/newtons/pounds/whatever while anchor B held up to a slightly greater force, therefore anchor B is better than anchor A". The next test can give quite different results. It would be more reasonable to say "Anchor C has given consistently fairly good results in all the well-conducted tests I have seen, also Anchor C has generally given good results in practice as evidenced by the number of satisfied users, so I have some confidence in Anchor C". Which is about as far as I think one can go.
Whether the Kobra is an anchor C is up to you to decide. The experience reported on the very forum will help you.

Much as one might like to see one, I don't think the evidence supports a "league table".
 
CAPTAIN FANTASTIC said:
It is a speculation that the Kobra has weak shank. However, I would prefer a shank that bends than a shanks that snaps due to strong but brittle material. Ductility in mild steel produces a very forgiving material; it's a compromise.
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Not entirely speculation I think and I don't think anyone has used the word 'weak' before. Heat treatment costs money, the Delta, that is pretty similar in most respects to the Kobra but does have a heat treated shank, is quite a lot more money as a consequence. The only brittle shanks I have seen are on cast copies of CQRs, I wrote an article in YM on one a couple of years ago. I don't think any plate shanks would be made from brittle materials as they would not weld.

Found the photo. Just about as bad as it could be from a metallurgical point of view. Must have been barely molten when it was cast.
1e097a951dc811c7c7475f9dcb6c4e10_zpsd29204f6.jpg
 
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Used a 16kg Kobra 2 for a few years now. Unlike our 35lb CQR, the Kobra has always set first time (except once in weed) - this was important for me as it was all done by hand. Superb anchor and held solidly in F8, plus the big gusts that come with it.
 
jordanbasset said:
I assume you mean the test referred to here

http://baatplassen.no/i/topic/61889-cqr-anker-ble-slaktet-i-ny-test/
'11 anchors tested on sea bottoms of sand and sand + mud:
Winner of the steel category is Spade, with an average holding in hard sand of 1905 kg and on sand + mud of 570 kg (value recorded before rupture of the fixation of the dynamometer).

The second is the Kobra 2 anchor from Plastimo with an average holding in hard sand of 1263 kg and on sand + mud of 1058 kg - the Kobra anchor represents the best compromise characteristic /price.

In third position comes the Bügel anchor with an average holding in hard sand of 1138 kg kg and on sand + mud of 999 kg

The fourth anchor of this comparative test is the Supreme with an average holding in hard sand of 1076 kg and on sand + mud of 631 kg. In spite of honourable results, this test confirms that the “Roll bar” anchors are not, and by far, the best .

In fifth position comes Brake, followed in sixth position by the Delta with an average holding in hard sand of 450 kg and on sand + mud of 662 kg. If these characteristics are sufficient to ensure the holding of a boat in more than 95% of the cases, the perfomances of the Delta are disapointing and far behind the best in the test

Come then Britany with passable results and the two last from the test with frankly bad results: anchor XYZ and the last, the CQR with an average holding in hard sand of 206 kg and on sand + mud of 363 kg

The conclusions of this test are:

- the aluminum anchors give as good performances as the steel models, with however the disadvantage of being more fragile.

- New technologies of anchor are definitely more powerful than their glorious elder, with double, to see triple values of holding.

- Spade, Kobra 2, Bügel and Manson Supreme are excellent anchors having significant differences compared to the traditional anchors'

The person posting does make the qualification that The bigest shortcoming of this test is that it is published in French. I do not plan to translate it totality , but for those which do not perfectly practise this language, I will try to report the general outlines: '
But from my memory of the test his translation does reflect what Voiles & Voiliers published in the 2009 article.
Yes the shaft of the Kbora 2 is probably not going to be as strong as the spade, but in real world conditions for most people that use them it appears strong enough. Also at a quarter of the price of the spade it is a good compromise. I have just bought a new boat (to me) and it has a delta on it, I will replace it with a Kobra 2 if I can source one locally in Greece.
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I am away from home and so I am speaking from memory. I don't think that that was the test I was referring to. There was a more recent comparative test, possibly by Voile magazine around 2012/2013 iirc.

Edit

Found it : http://www.stfeurope.com/pdf/Voile-Magazine-2012.pdf

The Fob Roc comments I now believe were in the comments in one of the Marine catalogues possibly Plastimo.
 
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vyv_cox said:
When Rocna made the mistake of stating on their website what material they used for their shanks, which when they subsequently bent proved to be untrue, the resulting furore sent the company into administration. The low cost of the Kobra suggests that their shank is made from similar stuff to that of the bendy Rocnas but of course, not having stated that they used high strength steel, nobody is the wiser. I have not seen a bent Kobra but when I do it will come as no surprise.
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If I remember correctly the original licence holder who used substituted steel went bust as a result of the scandal. As I understand it the new licence holder is making Rocna's using a high strength steel. I believe that it is a different specification to that originally heralded but the designer has approved it use and as far as I know there have not been any reports of bent Rocna's fabricated using this new specification.
 
Oddly enough mine was supplied new with a slight bend in the shank. It never seemed to affect performance which I thought was excellent.
 
I have no statistics but most of the anchors I have heard of that bent did so either because they got stuck in something immovable, tree trunk, rock, coral or because they were well set, say after a very hard blow, and the retrieval process was a bit aggressive. Taxing my memory - I know of lots of bent anchors but only one was during actual use, it bent when holding the yacht -it was a thunderstorm with a rapid and excessive change of wind direction. In most cases where I have sufficient detail there was never an indication the anchors were undersized (in fact - my classic case, the first anchor, correctly sized, was replaced by a bigger one - which also bent).

I have never heard of a shank bending, at all, when made from 800 MPa steel.

I don't know if my anecdotes are statistically sound but basically anchors bend because of the operator (during retrieval). This is not to excuse the anchor maker. I might add - most swivel and shackle failures occur at the same time.

The bent Kobra I saw at Preston - the shank was only slightly bent and I suspect the owner did not know or found it was not significant to performance. Mild steel shanks can be bent back to near the original orientation.

Jonathan
 
No, I do not know what steel Spade shanks are made from, except not an 800 MPa steel. If I had to guess I'd say a better quality mild steel, 350 maybe 400 MPa. The strength of the shank is in the construction - but today its a very expensive way of achieving strength (and not enough based on what you have seen). I do know the 15kg model uses 2 steel plates of 6mm each - so the steel thickness is the same as most 15kg anchors - 12mm (except it has the fillet to make the triangular box).

The stainless and alloy anchors are made the same way, same material thickness. I would say they are all equally strong, or weak :) though the steel one has better chance of being stronger, there being a whole range of steels from which to choose.

I have this vague idea Spade offer a lifetime warranty - if you know the owner tell them to contact Spade, or whoever they bought from. The warranty might only be valid in America - which is, I think, where I read it - though why America should be any different to the UK?? If they get, do not get, a replacement shank - it would be nice to know - either way.

It does reinforce the idea most anchors bend on retrieval, see Post #51 - this is particularly true of modern anchors that can be set so well, basically immediately immovable, they need time to break free (and time is not always available) and a rogue swell can snatch load an anchor - anchors should be built to accommodate this.



Jonathan

edit Maybe I should have read the thread first :( bit late to contact Spade 4 years later!! close edit.
 
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