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Old 14-03-2013, 17:43   #31
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Re: Knox anchor anyone?

The other thing about using a good bottom to test anchors is that is what many of us actually anchor in--I would venture to say that the vast majority of anchoring is not done by world cruisers in the Straights of Magellan or in the Tuamotus. So, anchor companies naturally want to make anchors that will sell well for the 98%+ of uses they will see, which I would venture to guess is a decent mud or sand or combination bottom. They don't really make anchors for world cruisers anchoring in the Straights of Magellan--there's no money in that.

That is one reason I found one of the WM tests so infuriating. They couldn't get the CQR and the Bruce to even hold, indicating to me that it was an unusual bottom. Even here on the CF anchor poll nearly 50% of the anchors are old school designs that were around long before anyone even dreamed of the Rocna or Spade. Outside of CF I bet it is way more than 80% of the anchors in use are old school. So, to publish a test where some of the most popular anchors of all time can't get a bite is ridiculous.

On the other hand, somebody needing an anchor that will work in oddball bottoms might be put off, but they have to realize that they are in the small minority of users.
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Old 14-03-2013, 17:50   #32
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Re: Knox anchor anyone?

Andrew,

Your point is valid. My experience suggests that to set a CQR you need to do so at short scope, 3:1. Really you need to get the weight off the shank or it lies on its side. Consequently if you try to measure its 'holding capacity at 7:1 it will be a disaster. Equally if you try to set a 10kg Bruce (copy) in a hard seabed it will simply not penetrate - its toe is too blunt (though it might actually work in a 20kg version). I hope we tried to address such issues, by pointing out the weakness of the technique and suggesting there might be some 'scale' issues.

The alternative to inadequate independent testing is manufacturers hype. You might be lucky in having opportunity to test a number of different designs - most people do not have that luxury and one hopes unrealistic though we may be that we do offer some balance to the 'exaggerated' claims of those with a financial interest in the success of one specific product.

But just because you do not agree with independence, because you do not think it meets your ideas of realism (and I'd agree with you - but we do try) there is no need to shoot the messenger - they are sincerely trying to provide balance. If you know of a better way, for those who want to make a choice on purchase - please advise.

In many respects its 'slightly' academic. Most modern, call them new gen, anchors have been tested and shown to work, well. Actual users confirm the results from actual usage. New designs might need looked at, Boss, Mantus but rehashing old results does not look too beneficial, though maybe look at different seabeds. But there are other issues now, do they re-orientate to a wind shift, are they strong enough to withstand loads etc, do they clog (or is that a phurphy), do they fit your bow roller, is that supplier galvanising as well as a competitor, does the much claimed 'sharp toe' withstand constant usage.
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Old 14-03-2013, 19:08   #33
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Re: Knox anchor anyone?

JonJo

I applaud your efforts and your commitment.

I should clarify that part of my reason for saying I don't "need" tests is that (in my experience) most anchors, and all reputable anchors, are perfectly good anchors.

They hold well enough in good holding (which is all that the tests cover), if they're suitably sized, they've got the weight of chain which suits them, and they're deployed in a way which plays to their strengths.

And my list of anchors I'm familiar with which work "well enough" for my purposes certainly includes such vastly different configurations as CQR, Northill, and even fisherman. *

So the considerably more subtle distinctions between various extremely similar New Gen anchors don't bother me greatly.


I don't mind any mild inconvenience involved in not being able to "set and forget", and I don't mind sometimes having to hedge my bets by changing anchors or putting out a second or even third one. I'm used to that, from the frequent situation of not-so-good holding.

I think that the modern preoccupations with progress and perfection tends to lead us to argue about differences which are not significant: people obsess about the perfect anchor, instead of making do with whatever they can get their hands on.


* I draw the line at Navy stockless, and I don't have much experience of oddball French anchors...

- - - - -

According to Knox's figures and formulae, a 40 foot cruising sailboat would continually drag a 15kg (33lb) Bruce in good holding, and on flat water, in a constant 24 knots of wind.

Doubling up to a 30kg Bruce would only "buy" a further eight knots of breeze.

These results are patently implausible.
An anchor so unfit for purpose would have made no impact on the market.

Given that he had long owned a Bruce, and his home waters were located in a windy part of the world, I just don't understand how he could not see something wrong here.
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Old 14-03-2013, 21:06   #34
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Re: Knox anchor anyone?

Andrew, I read your comments closely, they are clear, fair, and more than reasonable. Thanks for the "practical" view!
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Old 15-03-2013, 00:30   #35
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Re: Knox anchor anyone?

Congo here,

Didn’t think I could be bothered but I’m back, I am sure when it comes to anchor testing there may be a few here that can appreciate our efforts.

I have spent many thousands to address anchor testing methods, not just for, look, how much holding power we have but how our anchors react in varying types of sea bed, (most common types) I do have some knowledge in this area that may be of interest as our approach is totally different as to how we develop and test our anchor designs, whilst it is not perfect I think our method has opened a lot of eyes and is the reason we are getting results.

Andrew wrote: JonJo

I applaud your efforts and your commitment.

I should clarify that part of my reason for saying I don't "need" tests is that (in my experience) most anchors, and all reputable anchors, are perfectly good anchors.

Rex wrote:

Well Andrew I am glad someone appreciates the efforts from JonJo’s never ending efforts to find better anchors, difference being from JonJo's testing, our methods, our claims, are made from information supplied by a licenced independent anchor tester appointed by the N.M.S.C. National Marine Safety Committee, their responsibilities have since been taken over by A.M.S.A.

Some seven years back I was asked to be a member of many on the board of the N.M.S.C. during their discussions on new rules regulations to be drafted on chains ropes and anchors for commercial vessels, I was asked because we supplied many of our high holding power anchors for these vessels and believed my input amongst others could be value adding as to the outcome of these new regulations.

To cut a long story short we were discussing the field testing methods of anchors among many other issues that were thrown up in relation to the current regulations, at the time most anchor tests were still being carried out by large tug boats, their objective was to see if collectively we could come up with a better more accurate and less expensive method for anchor testing as they were now going to certify anchors with Super High Holding Power. Prior to the new regs S/H/H/P Certification was not available in Australia.

First part of the discussions relating to anchors was realistically any anchor manufacturer would struggle to pay for the operation of a tug boat, (16 thousand dollars a day) work that out over maybe 3 or four days, the second discussion was recognizing the possible flaws when testing from a tug boat, this was an interesting discussion, they found collective ally it is impossible to work out the variables that were created with such a field test, wave high, anchor Rhode weight, throttle response, undulations, softer or harder areas of substrate the list go on. A more accurate method if possible using a simpler device would, could address both of the above problems, cost and accuracy.

End result of all this collectively we did come up with a method that is far more accurate, allows you to test in proven varying types of sea bed, drops of all the variables resulting from tug boats, so much so the method is now approved by the N.M.S.C. as a new standard for testing of anchors, whether it be H/H/Power or S/H/H/Power/.

If anyone is interested I will show photos, test charts printed from the apparatus used, test certs as well if need be, I have given a considerable amount of time to this post and it will need a considerable more amount of my time to fill you in, not much point if those who pretend they want to know are going to throw stones. So indicate your interest and I would be happy to share with you some interesting stuff. Then if you want to throw stones be my guest.

There is one thing I find extremely odd and insulting to Brian of Fortress, how can anyone start a thread Fortress versus Mantus as a storm anchor? Need I say anymore, meaning the Mantus hasn’t even been properly tested yet but gets worthy comments against an anchor that has saved many lives, maybe its just me, but I find that comparison, this early is an insult.

Regards Rex.
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Old 15-03-2013, 06:46   #36
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Re: Knox anchor anyone?

Another thing that is lacking in the discussion of anchor holding power is how much is needed. There are some charts out there by organizations like ABYC and other standards organizations, but as far as I can tell they are mostly theoretical. Don Dodds did some interesting work on this too, as did Robert Smith, and more recently our own MaineSail and JonJo have made some measurements of real-world loads. But, I still think this is an area where we are mostly going by rules of thumb developed over many years. My own suspicion is that the actual loads at anchor are much lower than the predicted loads, at least much of the time.
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Old 15-03-2013, 06:58   #37
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Re: Knox anchor anyone?

Quote:
Originally Posted by congo View Post
There is one thing I find extremely odd and insulting to Brian of Fortress, how can anyone start a thread Fortress versus Mantus as a storm anchor? Need I say anymore, meaning the Mantus hasn’t even been properly tested yet but gets worthy comments against an anchor that has saved many lives, maybe its just me, but I find that comparison, this early is an insult.
Hi Rex,

No worries, mate!

After reading your post, I thought that it would have been nice if we had made contact several years ago when our late owner was in Australia during his circumnavigation, and you gents could have met there for a very lively chat.

As a fellow anchor designer/manufacturer, he shared your passion for testing and perfecting his product, whether it was conducting pull tests with a bulldozer along the south Florida sand beaches....or in the nearby muddy swamps of the Florida Everglades....or with destruction tests in "Black Maria." (Images below)

After those tests, it was back to the drawing board to figure out (oversimplying) how to machine the alloy in order to insure fast and deep penetration, but without compromising the structural integrity of the anchor.

Based on all I have read and heard about your anchors, you make a very fine product and I commend you for your efforts.

Sincerely,
Brian
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Old 15-03-2013, 07:16   #38
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Re: Knox anchor anyone?

I think I should clarify, I meant no disrespect for Jon Jo testing, our testing is done by an anchor tester as stated, that is a continuous static pull to satisfy the authorities that our anchors do in fact produce the required load for Super High Holding Power certification, if you want certification in multiple sea beds then you have to prove, test in multiple sea beds by an authorized tester.

Jon Jo testing is more of what you would expect in the real world of anchors behaviour, John Kettlewell I agree with, the loads that we are required to hit for the authorities is in most cases above what one will encounter in the real world.

That is probably why a well set CQR has a good reputation, once set has satisfied most yachters for many decades so have many other designs for that matter, regardless modern anchor technology has certainly improved anchors ability to set and reset in a variety of substrates that were far more unpredictable with the old style anchors, and yes all modern anchor testing has shown without a doubt that modern anchors do produce more holding power and in a shorter distance.

Regards Rex.
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Old 15-03-2013, 07:17   #39
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Re: Knox anchor anyone?

Concerning JonJo, I have closely followed his anchor test reports and I believe that he has been incredibly fair, honest and thorough.

His assessment of our product was not all glowing, but I was in full agreement with his findings.

I hope he continues on with his fine work.

Safe anchoring,
Brian
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Old 15-03-2013, 07:51   #40
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Re: Knox anchor anyone?

Hi Brian,

Thanks for those kind words, opposition companies complementing one another is a rarity these days, thanks for your understanding as only you could understand ones passion for achieving something at the same time making it safer for all.

And yes I agree, Jon Jo shares the same passion for his endless testing and sometimes extreme efforts to better understand and sought out just who is selling what, and is that what, what it is claimed to be, not sure whether I understand myself there, yes and we to have been in the firing line of Jon Jo if anyone wants to scroll back a few years.

Regards Rex.
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Old 15-03-2013, 08:12   #41
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Re: Knox anchor anyone?

So, has anybody actually seen or handled a Knox anchor?
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Old 15-03-2013, 10:37   #42
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Re: Knox anchor anyone?

Got a note from Knox. The 13 kg (about 29 lbs) model costs £400 including VAT, and they are only available direct at the moment.
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Old 15-03-2013, 15:08   #43
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Re: Knox anchor anyone?

I have known John Knox for years, we have compared notes, discussed results, discussed the inadequacies of testing etc

John tried to answer varies issues raised in this thread without success and has asked me to attempt to reply on his behalf. John has answered specific posts. I am simply copying and pasting.

Its not the neatest way for me to do it, but it was the simplest.

I had hoped to test the KA, but John is a new start up and sending anchors half way round the world is not cheap (and I cannot afford to buy one either! Hopefully we can get some user experiences in the fullness of time

Someone did comment that 'there was a lot of welding' - any weld if done correctly should be as strong, or stronger, than the strongest of the metals being welded. There is no point in using hi-tensile steel if the weld is not as strong as the steel.



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#1
Professor John Knox has written some very interesting articles about anchors and anchor tests, and apparently he is now producing and selling an anchor of his own design. There is more information on his website. Looks to be a new-generation type concave anchor with a rollbar, but it also seems to share some design features with the Super Sarca. Of course, like all anchor companies, he has a lot of claims of superiority. One thing to note is that he has apparently tested his anchor against the competition and is publishing some results on the site.


WEBSITE and PUBLICATIONS by JHK:
Website
<knoxanchors.com>
Publications by J H Knox:
“How Anchors Work” Royal Highland Yacht Club Journal 201259-64
“Anchors aware” PBO, 538 Aug 2011 pp81-87
“Snatching at Anchors”PBO, 386 Feb 1999 133-135
“Will my Anchor Hold” Pt1: PBO 427 July 2002 78-81. Pt2: PBO 428 Aug 2002 99-104

“Anchoring by Numbers” Yachting Monthly1092 August 1997 24-28


Yesterday, 00:34 #2

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#2
Thanks for the link.
It's an interesting design that has the elements that generally result in a good modern anchor. Although it looks like there is a lot weight at the roll bar end of the anchor, which is generally not helpful.
The deep shank means that it may fit boats where normal roll bar anchors do not. Modifying the bow roller to take a roll bar anchor, which is sometimes necessary can be difficult and the Spade, which solves the problem is very expensive.
Also produced in the UK may give a price advantage to European customers.

The big question is how it performs. It's a pity some the anchor manufacturers make such exaggerated claims. 50 % better than the best anchors we have at the moment ( MS, Rocna and Spade) seems unlikely.
It would be nice to get a new round of tests as a starting point to show which of these new anchor designs show promise.




JHK Comments: The 50% improvement in performance is the minimum improvement established in my tests covering a range of anchors includinhg the SPADE, Rocna and Manson Supreme. I have acquired a large amount of data over the last year or two – a lot more than has been published. The location of the tests is Londgniddry Bay (Gosford Bay) on the south side of the Firth of Forth where the seabed is medium-hard sand. While other sea beds will undoubtedly produce different absolute results it seems unlikely that there will be substantial differences in the order of performance of different anchors. However it is important that other independent tests are carried out in different locations. I would strenuously maintain that the 50% improvement is genuine and not an advertiswing gimmick!
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#3
Professor Knox is an academic and scientist of considerable renown and is highly respected in his field. He has also spent the last, at least, 15 years independently testing anchors and has had a series of of meticulous articles published in the UK, YM and PBO. To suggest that he has exaggerated any claims, without substance for the use of the word 'exaggeration' is an insult to Professor Knox' integrity and simply shows a lack of courtesy.

When other workers have had opportunity to assess Professor Knox' claims we might then be able to comment - in the mean time his results are 'claims' and one should not denigrate without real evidence. I, for one, hold Professor Knox in very high regard and hope that his claims can be substantiated - it will be to the benefit to us all.

It merits mentioning that oil rig anchors, some developed from the lowly Bruce, are factorially more efficient than anything we use and a 50% improvement is nothing in their terms.

JHK Comments: Yes, of course my tests have been carried out by a single individual supported by family members and friends. They undoubtedly need to be confirmed by other interested experimenters to establish their reliability. Although they have all been carried out in a single location, there was significant variation in the hold for the same anchor when tested on different occasions due to changes in the properties of the sand over time. Standardization was therefore essential. I used a 5.0kg SPADE. A standard test with the 5kg SPADE was therefore carried out along with the anchor under test. The holds measured for the test anchor were then corrected to a standard hold for the SPADE.
50% may not be a huge improvement but it is significant. Of course we do not really know whether the efficiencies (Hold/weight) of these large anchors can reliably be extrapolated to 5-50kg size __________________

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Re: Knox anchor anyone?
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It merits mentioning that oil rig anchors, some developed from the lowly Bruce, are factorially more efficient than anything we use and a 50% improvement is nothing in their terms.

Yes but they generally weigh 20T
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JHK Comments: See above.

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Yesterday, 04:12 #6

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Quote:
Originally Posted by Pacey16
It merits mentioning that oil rig anchors, some developed from the lowly Bruce, are factorially more efficient than anything we use and a 50% improvement is nothing in their terms.

Yes but they generaly weigh 20T

If you check with Vryhof they use little models, about the size of our anchors, before they make the bigger ones. I understand that its cheaper and they think the results scale up. My point was only - it is in the realms of possibility so do not deny the possibility without checking.

JHK comments. It is clearly cheaper to test small anchors when seeking a new design, but it is important to test the appropriate size before going into production whatever the final use – leisure yacht or oil-rig
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It is worth it hunting up Knox's articles, if you can find them. He has a list on his site, but not copies of them, which is a shame. But, here's one. In any case, he has some interesting test apparatus that measures actual loads on the anchor rode. Somewhere amongst his writings are some notes I found interesting, where he indicates that certain size anchors are not as good as other sized anchors of the same design--actual evidence of a scaling effect that some have speculated on.

JHK comments I define the efficiency of an anchor as its Ultimate Holding Capacity DIVIDED by its weigh, or more briefly hold/weight. Broadly speaking the efficiency of anchors of a gived type but of different weights ismore or less constant from say 2 to 20 kg weight. In more detail there are minor differences, and there is the question of whether stainless steel anchors give higher efficiencies than galvanizes steel anchors. This needs to be tested.__________________
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Wondering why the slot? Seems like it makes folding back one of the flukes more likely. I noticed also he picked the comparison anchors to suit his study. If you compared the danforth type in efficiency/weight something like the fortress would blow away others, where was delta in efficiency and why left out?

JHK Comments: Experiments were initially carried out with an undivided fluke. Following tests with a Danforth-type anchor, which gave a remarkable efficiency, I decided to try a divided fluke. This provided a substantially higher efficiency then the one-piece fluke.
In my tests of a range of anchors, the delta provided very modest efficiency (hold/weight) of around 10 compared to the KA of around 45.
The strength of the half-flukes to bending satisfies the IACS test.
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#9 He had concluded in earlier tests that the Delta wasn't as good as the new-gen anchors so he left it out of this comparison. Not sure about the Fortress. Is it possible that the Fortress is not widely distributed in Europe?
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JHK comment: see above. A full test of the Delta is tobe found in our website <www.knoxanchors.com>


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Re: Knox anchor anyone?
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#10 Quote:
Originally Posted by JonJo
To suggest that he has exaggerated any claims, without substance for the use of the word 'exaggeration' is an insult to Professor Knox' integrity and simply shows a lack of courtesy.
No, it's not an insult, and it doesn't show any lack of courtesy. The plain fact is that exaggerated claims are the standard in the anchor industry. It is what we have grown accustomed to, and come to expect. I'm sure the good professor knows that, and understands that people are going to be dubious of his claims until they have been proven over some period of time in real-life conditions.

What's more, noelex never said that Dr. Knox's claims were exaggerated. He simply pointed out that anchor manufacturers make exaggerated claims (which they do) and then said that 50% better seemed unlikely to him. Seems unlikely to me, too. This is no knock against Dr. Knox's integrity, and if he takes some healthy skepticism as a personal insult then he is very definitely in the wrong business.

I think it would be wonderful if this new anchor turns out to be that much better than anything else that is currently available. But I am not going to be convinced by laboratory tests, or engineering equations. I will be convinced only when real-life experiences, over a period of time, and in a wide range of conditions, proves out the design. In the meantime, I wait, I hope, and I reserve just a bit of skepticism.

JHK comments: I am not offended by the comments referred to. Claims which are not independently verified are always suspect, especially when made in a commercial context. Perhaps someone with the necessary equipment (primarily a load cell) would check them out.
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#11 Quote:
I would perhaps worry that something (like the chain) could get stuck in the slot.
Or a rock, a quahog shell, or whatever trash is on the bottom.
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JHK comments. We are now putting a bar across the tips of the half flukes to prevent this happening. This bar has no effect on the anchor efficiency.

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Re: Knox anchor anyone?
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#12
The lowly Bruce is an awesome anchor and I want 3 more, so when you all buy these new fangled things, please send me your 30 kg Bruce anchors....
thankyou.


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JHK comment: see comment below on entry 13.

Yesterday, 06:37 #13

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#13 Quote:
The lowly Bruce is an awesome anchor and i want 3 more, so when you all buy these new fangled things, please send me your 30 kg Bruce anchors....
thankyou.
And, there is the perfect counterexample to all the anchor tests that indicate the Bruce is one of the worst anchors for holding power. Yet, experienced boaters seem to like them, at least in larger sizes. I've noticed two things about Bruce anchors, and I am not a fan. One is that those who use very large ones seem to get better results. Two, they seem to perform better in hard, difficult anchoring situations, like are often found in the Caribbean or the Pacific, where cruisers tend to go. Judging from how often I have had a Bruce-anchored boat drag into me, they do not perform so well in areas with good holding ground--deep mud, deep sand, etc.

My point being, that anchor tests are usually concentrated on maximum holding power, which is not the only thing. After all, how many nights at anchor is your anchor tested for holding power? Very few. Yet, virtually every time you use it setting ability is tested.
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JHK Comments: When we bought our first cruiser (a 35 ft Hustler 35) around 1985, I immediately bought a 15 kg Bruce which was strongly recommended and which we used without incident for many years until we replaced it by a SPADE, and now by a KNOX. I therefore expected to find it gave excellent holding power when I began testing various anchors. I was extremely surprised at its poor performance. I have now tested Bruce anchors from 2 to 15 kg and they all perform similarly in terms of efficiency (Hold/weight). Compared witgh other anchors they give somewhat lesser efficiency than the CQRs and Deltas. Interestingly, a 2 kg stgainless steel Bruce does perform well giving agbout twice the hold of a galvanized 2 kg Bruce. A Chinese copy of the original Bruce gave an exceptionally poor hold. Maybe the hold of the Bruce is particularly susceptible to the surface finish or to the exact details of the dimensions. At the very least, beware of imitations!
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Re: Knox anchor anyone?
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#14
Anchor testing is done in a controlled environment, not in reality.
and my Bruce is not too big for my boat. is perfect. works well in this stuff called Mexican bottom sand and rocks and mud. If they drag so much, why are the oil rigs not dragging allover gom......

Never had a boat anchored with a Bruce drag onto me. Only the rocna user who couldnt anchor in rocks, and a cqr who was plowing the corn fields below the surface, and my own cqr that drug when my chain dropped into a channel.
There are many new fangled anchors that all look the same and donot fit on older bow rollers and sprits without modifications.
I willstick with my Bruce and cqr, thankyou.

JHK COMMENTS: You are welcome to stick the Bruce and CQR. In my opinion they are both poor anchors compared with the more modern one. The CQR is particularly dangerous as it will roll out if forced to plough.
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Yesterday, 11:24 #15

Kettlewell
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Join Date: Jul 2006
Posts: 2,585 Re: Knox anchor anyone?
#15
One of the problems people are having today is that real Bruce anchors are scarce, and some of the cheap knock-offs don't seem to be very strong or have the right shape. I suspect the originals were better. Also, you need a bigger size than other anchors in order to get decent holding power, though I wouldn't want one after seeing all the draggers with them. Here's a photo of one going up on the reef to my portside in the San Blas.

JHK comments- (copied from above): When we bought our first cruiser (a 35 ft Hustgler 35) around 1985, I immediately bought a 15 kg Bruce which was strongly recommended and which we used without incident for many years until we replaced it by a SPADE, and now by a KNOX. I therefore expected to find it gave excellent holding power when I began testing various anchors. I was extremely surprised at its poor performance. I have now tested Bruce anchors from 2 to 15 kg and they all perform similarly in terms of efficiency (Hold/weight). Compared with other anchors they give somewhat lesser efficiency than the CQRs and Deltas. Interestingly, a 2 kg stainless steel Bruce does perform well giving about twice the hold of a galvanized 2 kg Bruce. A Chinese copy of the original Bruce gave an exceptionally poor hold. Maybe the hold of the Bruce is particularly susceptible to the surface finish or to the exact details of the dimensions. At the very least, beware of imitations!
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Old 16-03-2013, 02:10   #44
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Re: Knox anchor anyone?

Quote:
Originally Posted by Andrew Troup View Post
JonJo

According to Knox's figures and formulae, a 40 foot cruising sailboat would continually drag a 15kg (33lb) Bruce in good holding, and on flat water, in a constant 24 knots of wind.

Doubling up to a 30kg Bruce would only "buy" a further eight knots of breeze.

These results are patently implausible.
An anchor so unfit for purpose would have made no impact on the market.

Given that he had long owned a Bruce, and his home waters were located in a windy part of the world, I just don't understand how he could not see something wrong here.
Knox's figures are valid: Wind load is proportional to the square of wind speed. 32x32 / 24x24 = 1.78
Thats getting close to doubling the size of the anchor and when you factor in the extra wave height from a stronger wind going from 15kg to 30kg for 33.3% extra wind speed seems pretty fair to me.

Irrelevant for storm force winds & cruisers of course.
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Old 16-03-2013, 03:08   #45
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Re: Knox anchor anyone?

DumnMad:

You misunderstand me. I was pointing out that, according to Knox's direct measurements, a particular boat with a particular anchor in good holding would drag in 24 knots.
This is not realistic, or remotely close to it.

In case anyone might dismiss this, thinking that anchor was too small for that boat, I applied the square law (which Knox had confirmed he considered was applicable), and it was me who calculated the wind speed he would predict for an anchor of twice the weight, which anyone would consider to be more than big enough for that boat. That windspeed was also very clearly unrealistically low.

So it was not the eight knot difference I was questioning, it was the two values of windspeed.

Note also that his predictions are based on flat water.
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