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.
Kettlewell
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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
noelex 77
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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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Yesterday, 02:00 #3
JonJo
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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 __________________
Yesterday, 03:18 #4
Pacey16
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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.
Yesterday, 03:32 #5
__#5
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Yesterday, 04:12 #6
JonJo
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#6
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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#7
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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Yesterday, 05:43 #8
forsailbyowner
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#8
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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Yesterday, 06:00 #9
Kettlewell
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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>
Yesterday, 06:01 #10
denverd0n
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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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Yesterday, 06:07 #11
Kettlewell
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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.
Yesterday, 06:23 #12
zeehag
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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.
life is an adventure meant to be LIVED!!!!!!!
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JHK comment: see comment below on entry 13.
Yesterday, 06:37 #13
Kettlewell
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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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Yesterday, 06:50 #14
zeehag
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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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#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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