KnoxAnchor - has anyone any experience of using one?

Hi, nice picture. You are right I got the size from the anchor size guide but turns out that isnt the fluke area! Just checked.
Intesting thats its bigger, it is a nice anchor the Mantus, we look forward to reading your write up. Its been on our mind to have a good test ourselves of as many different NGA's as we can, a land based visual test and as you are doing some setting and diving in real world test. We have a Manson, Delta and now the Knox locally to play with and maybe a Mantus soon.
Happy hooking.
 
I've been browsing the Knox Anchor site. Might as well pass on the link.http://www.knoxanchors.com/
And here for comparison is the Mantus site: http://mantusanchors.com/products-2/

I must say that the Knox looks like a bit of a camel!! A cross between a Danforth , Bugel and Spade. As usual the claims are extravagent and somewhat speculative.
I suspect the split blade is just to get a patent on that feature but, if it works it will have its enthusiasts just like any other anchor when deployed properly.
 
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noelex said:
Thanks for the report. It looks like a promising anchor.

I think you might have confused the fluke area for the anchors looking at kg for one and Lbs for the other. The Mantus blade area appears bigger from the specs by about 25%

Mantus have sent me an anchor at no charge and I have been testing it over the last five months. It has been performing very well, so far even a bit better than the Rocna. I have unfortunately no experience with the Knox.

This is a photo of its set where I am anchored at the moment. This is a typical excellent performance:

imagejpg1_zps302c72b3.jpg
Click to expand...

Most modern anchors set within their own shank length, the Mantus does not seem better in that respect than any of the others, it still needs a shank length to set. When you mention that it works well it merits mention that you are using, I think its a 60kg anchor (and the Rocna was 55kg), on a 46' yacht. I would expect anything of that weight to work well. I'm guessing most manufacturers would be recommending something round the 30kg-40kg for that size of yacht. Bigger might be better - but it should be mentioned so that people have a better understanding and are not misled.

I am sure you will correct my comments.

edit.

Anchors are not only about how they hold but also about how they perform overall.

A 60 kg Mantus has a very large fluke, have you ever tried sailing to windward in big seas with such a large protuberance.

close edit



Jonathan
 
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SHUG said:
I must say that the Knox looks like a bit of a camel!! A cross between a Danforth , Bugel and Spade. As usual the claims are extravagent and somewhat speculative.
I suspect the split blade is just to get a patent on that feature but, if it works it will have its enthusiasts just like any other anchor when deployed properly.
Click to expand...

There is perhaps a slight difference between the claims for the Knox and some others. Prof. John Knox has been testing anchors for many years using scientific methodology, so at the very least any figures he has produced may bear comparison with other anchors.

The flaw with all the tests, of course, is that they almost universally compare holding power, which is all very well but is only one item for consideration in the overall performance of an anchor. A large concrete block will hold very well in a straight pull but that doesn't make it a good anchor:)
 
arranite said:
Hi, nice picture. You are right I got the size from the anchor size guide but turns out that isnt the fluke area! Just checked.
Intesting thats its bigger, it is a nice anchor the Mantus, we look forward to reading your write up. Its been on our mind to have a good test ourselves of as many different NGA's as we can, a land based visual test and as you are doing some setting and diving in real world test. We have a Manson, Delta and now the Knox locally to play with and maybe a Mantus soon.
Happy hooking.
Click to expand...

Go to:-

http://www.cruisersforum.com/forums/f118/photos-of-anchors-setting-126073.html

where you'll find IMHO the most informative, factual thread I've ever found on anchors and anchoring - with lots of comparison data on various anchors.
No force-feeding of anyones' opinions, or marketing hype.

It's on the basis of this thread that I'm replacing my worn-out CQR with a Mantus at about 20% of the price of the Knox.
 
SHUG said:
I've been browsing the Knox Anchor site. Might as well pass on the link.http://www.knoxanchors.com/
And here for comparison is the Mantus site: http://mantusanchors.com/products-2/

I must say that the Knox looks like a bit of a camel!! A cross between a Danforth , Bugel and Spade. As usual the claims are extravagent and somewhat speculative.
I suspect the split blade is just to get a patent on that feature but, if it works it will have its enthusiasts just like any other anchor when deployed properly.
Click to expand...

That the claims might appear extravagant is up to the reader - however some of the supporting theory stands scrutiny - I think the Spade is the closest relative...
I'd second the concerns about mixing heat-treated steels in a hot-dip galvanised unit - those anchor shanks on Spade, Ultra etc are under enormous stress (and I've bent the forged shank of the CQR and that of the kedge Delta), neither of which are particularly high-power setters.
One of the reasons for going for the Mantus was the separate, replaceable shank.
 
J Neeves said:
I am sure you will correct my comments.
Click to expand...

Of course, this is an anchor thread :)

You have mentioned setting distance. This is one aspect of good anchor design. The ideal anchor sets rapidly. This has the advantage that the anchor is less likely to encounter adverse substrates such as patches of weed, isolated rock or debris while setting and perhaps more importantly when digging deeper in response to stronger wind.
I disagree the Mantus is average in this regard. Exceptionally good would be a better description.

However, the photo shows also other characteristics of an anchor that is performing well. The anchor has dug in its fluke rather than simply scraping along the bottom and piling up the sand for example.

Note the photo of the Mantus is just the latest in my current location. It is a typical performance from this anchor rather than a specially selected photo.

I have published photos of every single set of this anchor over the five month trial, as well as every other anchor I have encountered during this time so a comparison can be made.

The Mantus is 57kg, almost the same size as my Rocna that is 55kg. I used the Rocna for 5 years anchoring perhaps 300 days a year and diving on most of those sets. The anchor is oversized +1 to +2 over the recommended size. This considerably helps the holding, but a large anchor in relation to the size of the boat tends to set less deeply with the engine setting force than a smaller anchor. Therefore in terms of the photos it looks worse. However, the anchor size was not selected for the test, it was what I deem ideal for my boat.

This, for example is a typical performance from a Delta in a similar substrate. You can see the much longer setting distance and how the Delta is piling up the sand rather than the fluke digging down.

These photos are only a single examples of the Mantus and the Delta, but they are typical results rather than isolated atypical performances. I have posted all the results over the trial period so you can make up your own mind how the setting distance of the Mantus compares to other designs:


imagejpg1_zps7a2c4107.jpg


I have not had any problems bashing into wind with either the Rocna or the Mantus, but I do secure my anchors carefully. The fluke area is large, but the concave blade shape means the wave meets the convex underside of the blade which has less drag than the underside of of convex plough anchor. The roll bar also helps provide an additional securing point that is well above the centre of gravity, but I don't think something like the same weight Spade, which does not have a roll bar, would create any great problems. My chain is lightweight G7 chain so the total bow weight is less than a much smaller anchor with chain one size larger.

The Mantus has quite a long thin blade and a wide roll bar so you do need to check it fits.
 
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Another current thread of interest is attached:

http://www.trawlerforum.com/forums/s42/chesapeake-anchor-holding-power-test-15941.html

The testing was funded by Fortress and unsurprisingly the Fortress comes out well. However ignoring the Fortress superiority (and to a lesser extent that of Danforth) the tests do suggest that categorising anchors simply as 'concave' or 'convex' is fundamentally wrong (and to do so is a simply sign of ignorance or, worse, bias), and grossly misleading. Ostensibly the Ultra and Spade are similar but had factorially different performances, similarly Manson's Supreme has been 'accused' as being a copy of the Rocna (and again they perform in this test very differently), with the Mantus different again. Slight differences or nuances in design have enormous differences in performance - in this test seabed, soft mud.

Given the difference, found in this test, between the Rocna and Mantus the claims of Prof Knox look quite modest.

Most new anchors have a focus at setting in a hard seabed, I do not know what the seabed is like that John Knox used in Edinburgh, but I do not recall it as being 'hard' however if you anchors in soft sand or mud then the Chesapeake tests might make sobering reading.

For links to the results to the tests check the Fortress posts.

But the CF thread has some excellent images - just recall that the anchors (both the Rocna and Mantus) is slightly less than 2 times the weight of the anchor recommended for that size of yacht. Bigger might be better, but performance, an absence of dragging, based on an anchor 2 times the size looks to be drawing questionable conclusions (unless you are happy to, possibly unnecessarily, add to an anchor maker's bank balance).

Jonathan
 
The Knox anchor web site just refers to anchoring in sand.

But don't we need to know how it holds on other types of bottom?

I'm new to anchoring, coming from dinghies.

I will ask a question in another thread re "lunch" anchors
 
J Neeves said:
Another current thread of interest is attached:

http://www.trawlerforum.com/forums/s42/chesapeake-anchor-holding-power-test-15941.html

The testing was funded by Fortress and unsurprisingly the Fortress comes out well. However ignoring the Fortress superiority (and to a lesser extent that of Danforth) the tests do suggest that categorising anchors simply as 'concave' or 'convex' is fundamentally wrong (and to do so is a simply sign of ignorance or, worse, bias), and grossly misleading. Ostensibly the Ultra and Spade are similar but had factorially different performances, similarly Manson's Supreme has been 'accused' as being a copy of the Rocna (and again they perform in this test very differently), with the Mantus different again. Slight differences or nuances in design have enormous differences in performance - in this test seabed, soft mud.

Given the difference, found in this test, between the Rocna and Mantus the claims of Prof Knox look quite modest.

Most new anchors have a focus at setting in a hard seabed, I do not know what the seabed is like that John Knox used in Edinburgh, but I do not recall it as being 'hard' however if you anchors in soft sand or mud then the Chesapeake tests might make sobering reading.

For links to the results to the tests check the Fortress posts.

But the CF thread has some excellent images - just recall that the anchors (both the Rocna and Mantus) is slightly less than 2 times the weight of the anchor recommended for that size of yacht. Bigger might be better, but performance, an absence of dragging, based on an anchor 2 times the size looks to be drawing questionable conclusions (unless you are happy to, possibly unnecessarily, add to an anchor maker's bank balance).

Jonathan
Click to expand...

Here's a comment concerning Rocnas which I received yesterday:

http://www.morganscloud.com/2011/11/23/rocna-versus-spade-anchors/

Author: Don Joyce
Comment:
We have a 100 kg Rocna on our catamaran and have experienced dragging on two occasions: Both involve being set directly over the anchor by a thunderstorm related sudden wind shift, while being anchored in very thick mud. Apparently the anchor tripped and wouldn't reset because the center of balance was shifted back by the hoop-trapped mud. On both occasions, we could only reset the anchor after hauling it up and clearing all the mud off with our boat hook. Listening to the windlass as the anchor was being hauled convinced me that the mud and anchor together were on the order of 200 kg....yet we "sailed" through the anchorage...
 
Sybarite said:
Here's a comment concerning Rocnas which I received yesterday:

http://www.morganscloud.com/2011/11/23/rocna-versus-spade-anchors/

Author: Don Joyce
Comment:
We have a 100 kg Rocna on our catamaran and have experienced dragging on two occasions: Both involve being set directly over the anchor by a thunderstorm related sudden wind shift, while being anchored in very thick mud. Apparently the anchor tripped and wouldn't reset because the center of balance was shifted back by the hoop-trapped mud. On both occasions, we could only reset the anchor after hauling it up and clearing all the mud off with our boat hook. Listening to the windlass as the anchor was being hauled convinced me that the mud and anchor together were on the order of 200 kg....yet we "sailed" through the anchorage...
Click to expand...

I think you will find that many people do not believe that this sort of things happens. They neither believe that roll bar anchors, or some of them, might clog and they do not believe that anchors can be tripped -they believe and post that they only shuffle round. I think if you have the patience to read the CF thread you will find some mention of shuffling.

Anchors need to perform by re-setting in the case of a sudden change in load direction (the tropical thunderstorm is an example) and need to work, and be shown to work, in a cross section of seabeds, not just hard sand. If they do not work in some seabeds it is wise to know, its the sort of thing an anchor maker should declare?, in which they are poor performers.

Jonathan
 
It's interesting how boaters love to disagree about anchors. Perhaps we're all following the mirage of the perfect all-round-anchor, which IMHO does not exist.

As I see it there are 3 variables (apart from Wind & Tide), 1. the nature of the bottom, and I don't just mean the holding. 2. the competence of the anchorer and 3. the anchor design.
Few if any anchors will hold well in the fluid mud of Alvor, few anchors are good for Bardsey. or the W side of Porto Palo.

In the sandy Mediterranean bottom nearly all the "new age" anchors, Bugel, Mantus, Rocna, Spade, Ultra set reliably and well in a very short distance.
The much-maligned CQR is probably king in shingle and the Bruce claw better for thin sand on rock or on sheet rock.
So the cruiser needs a selection of anchors for the bottom and the stream conditions he's likely to meet. From the "pictures of anchors setting" the most ubiquitous weakness appears to be the competence of the anchorers.

If there's any lessons to be drawn from the evidence I've seen:-
1. There is no such thing as the perfect all-round anchor for every bottom you're likely to encounter. 2. There's always room to learn.
 
There is a comment on the Knox site in the Anchoring Technique page.

The professor says the following :

A good modern anchor should start embedment immediately and develop its maximum hold or UHC after it has ploughed a 5 to 10 metres. By that time it should have rotated to a vertical position, and should be completely buried.

On face value this seems to say that a NG anchor will continue to move after the initial set. This is not something I have experienced with either of the two techniques we use now with our Rocna. If the bottom is sand then we find no finesse is needed; drop anchor, drop back, dig in (fast or slow makes no difference, the anchor buries immediately). Things are different in a couple of soft muddy anchorages we use and I now use quite a few bursts of reverse to slowly dig the anchor in. You get a feel for what the anchor is doing and typically it will set in just a few metres but with each ever increasing amount of reverse it will move backwards but never more than a very few metres.

Am I reading the professor correctly, is he saying that to achieve a full set the anchor will move back 5 - 10m ? My feeling is that the only way our Rocna could move that far (once set) is for it to break out.

He also says the anchor ends up in a vertical position - can that be right ?
 
Something that would be interesting would be Noelex taking the recommended sized anchor (33kg for a Rocna?) and trying it, or them, for 5 months. Whilst Noelex is quite entitled to use any size anchor he desires - he is suggesting, implying (not sure which word is politically correct) that a Mantus sets and holds well and that his thread is a lesson to us all. However the thesis is based on an anchor the anchor maker does not recommend for that size of yacht and most people are going to rely on the anchor maker's recommendations (if the anchor maker does not know which anchor is suitable - who does).

The reality is, and charles_reed seems convinced that Mantus is the way to go - based on a thread limited to 'tests' of an anchor twice the size recommended and 'tests' basically conducted in a similar seabed type, hardish sand.

But Charles - I agree, horses for courses - anyone wh thinks you should carry one anchor (only, even if big - fine in one seabed type, but otherwise??

Jonathan
 
Storyline said:
Am I reading the professor correctly, is he saying that to achieve a full set the anchor will move back 5 - 10m ? My feeling is that the only way our Rocna could move that far (once set) is for it to break out.
Click to expand...

Anchors dig down deeper in response to stronger wind. To do so they have to move backwards. However there are very large differences between anchor designs in how far they take to do this. It is only one aspect of anchor performance, but it has received very little attention.

In many substrates moving 5-10m back as the anchor digs deeper is not a great problem, but in others there is a real risk of the anchor hitting a patch of thick weed, an isolated rock or some debris.


Both the Rocna and the Mantus move back minimally in response to stronger wind. Say from my setting force equivalent to about 25 knots of wind the anchor will have moved back only a few inches in when digging deeper in response to say 40 knots. So the total distance from the drop point is likely to be in order of 1-1.5m. The steel Spade is also very good.

A Delta will move back several metres under the same conditions for a total distance of about 5-10m (these distances will depend on the substrate and scope etc, but the numbers give you some idea what is typical in medium to hard sand).

I suspect you have not seen anything with the Rocna because the movement is too small to detect. I used to place small stones on the bottom as markers to estimate the distances anchor around me were moving, but since photographing all the anchors I can usually pick out landmarks.

Generally all the concave roll bar anchors set quickly. I have not seen the Knox, but would be surprised if it performed in a similar way to the Delta. I think Professor Knox is reporting something a bit different where the peak holding power is recorded after a very long drag. An anchor often starts dragging a long way as its absolute maximum ultimate holding force is approached, just before breaking out.

I place very little emphasis on manufacturers' tests results, but I did note that the graphs on the Knox website suggest the Knox moves back about 50% more than the Rocna, MS and Spade before it achieves its ultimate holding ability. Of course the graphs show the Knox has much higher holding power (why does that not surprise me :) ), so for the same force the Knox anchor was moving back less, but there may be some reason to suspect the Knox does move a more than other concave roll bar anchors as it approaches its ultimate limit.


Storyline said:
He also says the anchor ends up in a vertical position - can that be right ?
Click to expand...

I think he means "upright". The roll bar anchors generally set by starting on to their side. As the are pulled back the rotate upright. It is amazing to watch the better anchors do this with less than a metre movement backwards.
 
A number of things stand out with your anchor photos Noelex, the anchor you are comparing is enormous, weight overall will set way faster in sand than any comparison of an anchor of lesser weight regardless of design, this generous enormous extra weight will also create more resistance when setting and will dig into harder material than its smaller brother, further comments relating to pulling out, listing, heaping up of the sand is simply because the anchor is so large it cannot be dragged far enough for some of this to happen, try a smaller Mantus, a smaller Mantus will not bury any deeper, the further it is dragged the bigger pile of sand, Noelex you should also show a smaller Mantus with the same loads applied via a load sell and compare heaping up of the sand, setting distance, change of tide, excertra excetera, at least this may also show that as some of the anchors you are photo graphing in comparison are way smaller, this may have some bearing on their performance and not design. It would be fairer.

Further how can you compare anchor setting techniques, different people deploying different designs, not all the same size anchors, this could be 50 percent of any anchors design performance to look ordinary.

If you are going to compare design with a trusty camera it is extremely interesting, by not comparing apples with apples there is nothing to be learnt.

Noelex you dive on your anchor set, when you are not happy with what you see you then reset it again minimizing any chance of failure, almost every shot of your comparisons are made from boaters just dropping their anchors blind, I am sure if they dived they too would pay far more attention as to how to set an anchor.

Your thread is interesting for two reasons, it is enlightening to many to see how anchors work, how different techniques can interfere with a good set, and highlights the need for apples to apples testing.

NormaBrians contributions on the CF are refreshing and as different in results, commentary, and success rate as to yours as one anchor test to another.


John.
 
Noelex,

John Knox has been testing anchors since the 1990's, his first articles appear in PBO in the mid late 90s and continue for, at least, a decade. He compared anchors of equal weight and then compared those same designs in different weights in the same seabed and setting under identical conditions. He covered all the options. He did not take an anchor tested, or set, one way and then draw universal conclusions of the performance of that anchor (of different weights) set by different people. Furthermore he did not draw conclusions on anchor design and performance - he provided strong numerical data, nothing subjective, and allowed the reader to draw their own conclusions.

Professor Knox' work was not conducted as some abstract study, nor some dilettante with no life, he was a cruiser of some renown sailing in waters considered by many as inhospitable (unless St Kilda is one's home ground). He was able to transfer serious academic discipline to examining a problem considered by others as a simple marketing exercise.

To suggest that Professor Knox would show his anchor to have a performance that could not be substantiated shows complete ignorance of his work. Maybe you, as an expert in the field (and an academic), can take the time to check his articles for the decade from the late 1990's (all freely available) and then possibly you can substantiate your 'surprise' at his results.

Jonathan
 
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The Knox anchor is very new. Arranite's report is the first independent evidence I have read.

I have a high degree of cynicism concerning manufacturers' tests. If nothing else manufacturers naturally pick a substrate where their anchor does best. I don't see anything wrong with this, but I believe we should treat the results as more along the lines of marketing material rather than a true representation of how the anchor will perform in the real world.

If the claims by Knox Anchors are true it would be great. They show the anchor has 60% greater holding than the other top performers. The Spade and Rocna, closely followed by the Manson Supreme with the Danforth also doing well. I remain sceptical, but it would be great to see this anchor in action.

imagejpg1_zpsd2cea78b.jpg
 
Sybarite said:
Here's a comment concerning Rocnas which I received yesterday:

http://www.morganscloud.com/2011/11/23/rocna-versus-spade-anchors/

Author: Don Joyce
Comment:
We have a 100 kg Rocna on our catamaran and have experienced dragging on two occasions: Both involve being set directly over the anchor by a thunderstorm related sudden wind shift, while being anchored in very thick mud. Apparently the anchor tripped and wouldn't reset because the center of balance was shifted back by the hoop-trapped mud. On both occasions, we could only reset the anchor after hauling it up and clearing all the mud off with our boat hook. Listening to the windlass as the anchor was being hauled convinced me that the mud and anchor together were on the order of 200 kg....yet we "sailed" through the anchorage...
Click to expand...

Here is an additional comment received today:

Author: Don Joyce
Comment:
To be fair, we were on short scope around 4:1 to 5:1 due to limited swinging room. We usually have what late comers to an anchorage call "excessive" scope of at least 10:1. The excessive scope held us firm on the Rocna in Maine during Irene when several of the complainers around us dragged.

I did write to Rocna to suggest they need more weight in the tip. I will add some weight myself when we get the anchor galvanized.

A response to this comment:

http://www.morganscloud.com/2011/11/23/rocna-versus-spade-anchors/

Author: John
Comment:
Hi Don,

Thanks very much for coming up with that vital information. We are hearing of an increasing, albeit still small, number of these incidences with the Rocna. It's particularly disturbing that this happened with such a large anchor.

I think this danger is something that every Rocna owner needs to be aware of, so thanks again.

See all comments on this post here:
http://www.morganscloud.com/2011/11/23/rocna-versus-spade-anchors/#comments
 
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vyv_cox said:
There is perhaps a slight difference between the claims for the Knox and some others. Prof. John Knox has been testing anchors for many years using scientific methodology, so at the very least any figures he has produced may bear comparison with other anchors.

The flaw with all the tests, of course, is that they almost universally compare holding power, which is all very well but is only one item for consideration in the overall performance of an anchor. A large concrete block will hold very well in a straight pull but that doesn't make it a good anchor:)
Click to expand...

I am familiar with Knox's work on anchors but question his comparisons. His tests are generally made in rather artificial circumstances by using a vehicle to drag an anchor up a beach with a horizontal pull. I'm sure its a perfectly good anchor but this comarison business is best undertaken by independent organisations (as previously) in typical anchoring situations
 
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