Anchor design and misnomers

[Factor]

There two anchors look the same, therefore they are just as good as each other, one is 50 bucks where I live - the other $700, but they look the same therefore they are the same.

[Kettlewell]

Does anyone know if those Kobra II anchors from Plastimo are available in North America? Never seen one, and they don't appear on the USA distributor's website as far as I can tell. They seem to get some good reviews in Europe, and at least one magazine test indicated they were better than a Delta.

[downunder]

Originally Posted by Factor

There two anchors look the same, therefore they are just as good as each other, one is 50 bucks where I live - the other $700, but they look the same therefore they are the same.

You must be right then.

[Delfin]

Originally Posted by Kettlewell

Does anyone know if those Kobra II anchors from Plastimo are available in North America? Never seen one, and they don't appear on the USA distributor's website as far as I can tell. They seem to get some good reviews in Europe, and at least one magazine test indicated they were better than a Delta.

I don't think so.

Remember, this anchor is built in France, so it is likely to leak oil.

[Kettlewell]

this anchor is built in France, so it is likely to leak oil.

Probably extra virgin olive oil though.

[Snowpetrel]

Originally Posted by Kettlewell

The Vryhof manual referenced in the BIB post has some interesting information on holding power and soil failure at maximum holding power. Take a look at page 27. Their bottom line seems to be that the more streamlined an anchor is the better, for deeper diving, which is what they are touting about their anchors. The deeper the dive the better for holding power.

The other thing this manual clearly shows at the end in the graphs. Pg 185ish from memory is that the heavier anchors dive deeper than the smaller anchors.

Acording to these graphs the holding power of the anchor increases nearly linearly with weight. Not surface area like I would have expected. This might be due to the deeper set. And also the lower proof loads needed for bigger anchors meaning they can be built lighter with more surface area.

The Bruce anchor site also has some very interesting videos, including one showing them using a clear gel for model testing.

[Andrew Troup]

I should perhaps clarify that, to the best of my understanding, the word "improvements", in patent law, does not imply that the later patented item will necessarily perform better than the earlier one.

It means the examiner acknowledged that it was different, and in their judgement those differences are significant.

The wording of the patent will try to establish how and why it improves on the earlier patent, but I don't think the examiner makes a value judgement (that is not practicable), but instead ticks off on the question of plausibility ... in other words, it's an arguable proposition that the differences constitute an improvement.

- - - - -

I'm not arguing that the Excel does not improve on the Delta: I'm not qualified to judge that. I wish I had the time and the money to explore that question... (I do see a place for plough-type anchors, and would like to carry one)

I must say, however, that I'm very impressed by the patent, and I wish I understood Rex's posts better -- I generally cannot make head nor tail :-(

because I'm inclined to the view, from what I see, (including the photos of the actual product) that he's a gifted designer, certainly at the detail level.

Rex - if you wanted at some future date to use my idea (which you commented favourably about) of hard-facing the point with stainless weldmetal prior to galv, so it can be resharpened without impairing corrosion resistance, I'd be flattered rather than annoyed.

Naturally it's in the public domain, (and in any case it's unlikely it's original), so anyone's free to use it.

[Andrew Troup]

Originally Posted by Snowpetrel

The other thing this manual clearly shows at the end in the graphs. Pg 185ish from memory is that the heavier anchors dive deeper than the smaller anchors.

Acording to these graphs the holding power of the anchor increases nearly linearly with weight. Not surface area like I would have expected. This might be due to the deeper set. And also the lower proof loads needed for bigger anchors meaning they can be built lighter with more surface area.

The Bruce anchor site also has some very interesting videos, including one showing them using a clear gel for model testing.

Curiouser and curiouser ..... !

Scaling different factors is notoriously intractable:

eg while the viscosity of the seafloor remains the same regardless of anchor size; volume (and, if proportions are maintained, mass also) scales as the cube while area scales only with the square of linear dimensions ---

As Stephen Jay Gould observed, the design 'features' of an insect are completely inapplicable to a creature the size of a large animal, for these sort of reasons. Small insects can breathe through a relatively smooth exoskeleton without the need for lungs, for instance, whereas bigger insects need crinkles or 'invaginations' (!) in their casing to get the outside air within percolating distance of their inner organs.

- - - - - -

As to your last point: Note to self: be sure to use the Bruce if confronted with a seafloor of clear gel;

--- Note to 'downunder': only kidding !

as Factor, I'm pretty sure, was, in the post you responded to with banghead frustration -

[cwyckham]

Originally Posted by Andrew Troup

Curiouser and curiouser ..... !

Scaling different factors is notoriously intractable:

eg while the viscosity of the seafloor remains the same regardless of anchor size; volume (and, if proportions are maintained, mass also) scales as the cube while area scales only with the square of linear dimensions ---

As Stephen Jay Gould observed, the design 'features' of an insect are completely inapplicable to a creature the size of a large animal, for these sort of reasons. Small insects can breathe through a relatively smooth exoskeleton without the need for lungs, for instance, whereas bigger insects need crinkles or 'invaginations' (!) in their casing to get the outside air within percolating distance of their inner organs.

... -

This is a very, very important point. Looking at oil rig anchors is not very relevant to small yacht anchors unless one understands the scaling issues (which nobody here does, but somebody, somewhere might)!

To use the insect example again: There are many insects which can easily walk on water. That doesn't mean that people can walk on water.

[Wassa]

I was disappointed that the last thread closed because I had reported that I had bought a Sarca Excel and was about to try it out on a trip to Wilsons Prom. Now I find this new thread, so I can do so.

I have just returned to the Gippsland Lakes after spending several days at Refuge Cove on my Clansman 30 yacht. I had my recently purchased #4 excel as did my mate on his 35 ft trimaran. While there, we had a couple of fronts come through and saw gusts of 45 knots. The first night, the first front, we maintained an anchor watch all night because we were not sure how well the anchor would hold. Need not have worried as we did not move an inch. For the second front, we had moved to the other end of RC just off a lee shore and slept like babies as we had already proven how well they hold. As well as how the anchors held, some observations.
1. Even after the strongest blows, it was very easy to pull the anchor up.
2. One night there was a poor bugger who had to motor around RC for most of the night because his anchor dragged four times. I think he said it was a 10kg plough and he only had about 10 metres of chain which would have contributed, but we saw similar last year at Deal and Flinders Islands when we had to reset our plough a number of times in much less wind. The two other yachts we were with on that trip both had Excels and both could set once and forget.
3. My mate on the tri set a second anchor one night, the Excel and a plough, which did not work too well because they tangled. The plough dragged but the excel stayed put. From then on, he set only the Excel

It was my first experience with the anchor in angry conditions and its performance was excellent.

[Delfin]

Originally Posted by Andrew Troup

I should perhaps clarify that, to the best of my understanding, the word "improvements", in patent law, does not imply that the later patented item will necessarily perform better than the earlier one.

It means the examiner acknowledged that it was different, and in their judgement those differences are significant.

The wording of the patent will try to establish how and why it improves on the earlier patent, but I don't think the examiner makes a value judgement (that is not practicable), but instead ticks off on the question of plausibility ... in other words, it's an arguable proposition that the differences constitute an improvement.

- - - - -

Good description. The examiner only cares about whether the application is covered by prior art or is novel, and the task of the patent attorney is understanding what that prior art claims so that the application can make new and novel claims. The patents I have required educating the examiner on what the heck we were going on about, and pointing out how the prior art the examiner claimed incorporated our claims didn't apply. You could patent an improved ass kicking machine if you want to, and whether it really is a better device for the purpose is beyond the examiner's vision or interest.

[Andrew Troup]

Originally Posted by estarzinger

. . . Two differences have now been described vs the delta. (A) One is the change from two angles/bends in the delta rear flukes to one angle/bend in the excel rear flukes. I am honestly surprised that's an improvement, it sounds and looks more like a cost reduction. And (B) that it has an improved cutting edge. As I said above, this is likely a useful improvement in hard sand, but may be a vulnerable/less durable feature...

Evans

If you look at this photo of the Excel, the fluke difference is clearly a sophistication, rather than a cost-saving measure: there's a corner where three faces meet, due to the addition of the lateral extensions (22 and 32 in the patent drawings)

These lateral extensions were not in the Delta: the flukes were a simple pressing (edges only, no corners, no welds required)

This is a quite significant different in terms, not just of production cost, but potentially of performance, it seems to me ....

I'm guessing the obtuse internal corner creates triaxial compression in the mud at that point.

It further occurs to me that the strength of the compressed material is possibly assisted by preferential extrusion of any resulting low-viscosity component (like when you squeeze pulp in an orange squeezer) through the slots, particularly in the case of squishy mud.

It doesn't seem to me a far-fetched proposition that the slots might do something along those lines because they, too, are not cost-free.

Particularly (but not exclusively) with a shallow soft mud layer over a harder underlying pan, it seems to me beneficial if the anchor could build a mound of material, whose viscosity has been slightly increased, above and ahead of it.

By selectively bleeding the ooze through into the trench, and trapping higher strength mud, with which it increases its own sectional frontal area by "bulking itself up" as it travels, it seems to me this objective could be favoured.

I don't know if it works, but it seems novel, and plausible that it could work.

I'm reminded of certain (much-loved) wooded coves, where there's an optimum 'porosity' of trees which ensure the best wind barrier: far better than a solid wall could ever be, because pressure bleeds through the gaps into the cove, preventing the main windstream eddying down into it capriciously....

It seems to me by analogy that the flow of mud over porous flukes would be qualitatively different (possibly beneficially) in comparison with solid flukes. This is a different argument from the selective improvement to the viscosity, and perhaps more open to question.

- - - -

I can also see that the lateral fluke extensions 22 and 32 might influence roll stability, although I'm not qualified to judge whether it would be beneficial or detrimental.

It's sobering to reflect how small changes seem to prevent knock-offs performing as well as the anchor they copy, so it must surely be the case that small changes could alternatively be beneficial -

and I think the "Rocnagate" emails

(almost but not quite freshly minted coinage )

suggest that (say) detailing at the tip might be disproportionately important.

All things considered, including the more sophisticated tip profile, I feel it's entirely possible that this could be a game-changing improvement on the Delta, in a way the Kobra and other fixed-plough designs were not.

[JonJo]

The Kobra is a great design, much better in my humble opinion than the Delta. Develops hold quickly and the hold is high. Its is completely let down by use of a 'low' strength steel in the shank. There is little point in an anchor that develops very high holding power if at the least opportunity the shank has the potential to fold like wet cardboard.

Its not just about design, or shape, its also about the materials used (which are seldom mentioned). Its also about testing, how many people are using anchors that have been Proof Tested? How many people are using anchors the steel of which has no specification? It is contradictory to be negative about an Excel (whose steel is openly declared that has gone through a series of independent tests, as does the Supreme) and be using something for which there are no tests and made from an unknown steel (that might vary from batch to batch).

[estarzinger]

Originally Posted by JonJo

>>Primarily because you comment first off was 'it looks like a Delta' which sounded disparaging.

Well, I am sorry, but that's just simply a true statement and going to be one of the first thought to many prospective buyers. It does look like a delta. You might acknowledge I also explicitly said that I thought the delta was a decent anchor. And that an "improved delta" would obviously be even better.

>> You are effectively calling us liers

No, I certainly never said or implied that. I just don't find testimonials very compelling. In marketing generally they are known to have a strong self-selection bias. That does not mean any of them are untrue or lies. In anchors in particular they rarely seem to identify anchor weaknesses, until the anchors have been around for a decade or so. They certainly did not with the Rocna.

I am in the market for a new anchor, to replace the hole in my inventory created by taking the rocna off. Rex is making the rather dramatic claim that this anchor has twice the holding power of a supreme or rocna. If that's true I am quite interested. But you should certainly understand why "trust me" is not very satisfactory after rocna. So, I was simply asking the very most obvious question to see if there was some product design reason to believe this claim. If you don't like me asking a probing question about a product I am interest in buying, then tough, suck it up and man up. If you don't know that's perfectly fine. Getting all hostile is not helpful.

Now some other people did provide some useful information. The practical sailor test suggests there is more surface area which will certainly help, and the patient suggests a key feature is the shank location on the flukes providing a more balanced loading. That's useful information in trying to understand the anchor performance.

...........

[JonJo]

Originally Posted by Snowpetrel

The other thing this manual clearly shows at the end in the graphs. Pg 185ish from memory is that the heavier anchors dive deeper than the smaller anchors.

Acording to these graphs the holding power of the anchor increases nearly linearly with weight. Not surface area like I would have expected. This might be due to the deeper set. And also the lower proof loads needed for bigger anchors meaning they can be built lighter with more surface area.

The Bruce anchor site also has some very interesting videos, including one showing them using a clear gel for model testing.

The Vryhof manual has been available for years and when I last looked there was a section on correlation of surface area with weight. Basically as weight increases so does surface area (or vice versa). The weight only increases because the larger anchor need withstand bigger loads and you need more steel to make it stronger. They used to say somewhere that it was surface area that was important, not weight, but weight is often quoted because that is what everyone is used to. By use of different steels they can alter the weight:surface area relationship - as per Fortress.

The Bruce website has that lovely video of one of their anchors as a test model (I know people think its a waste of time modelling in tanks and testing on the beach but if its good enough for Bruce, Vryhof and the oil exploration and exploitation industries its good enough for me). But to return to the Bruce vid, it did show one of their anchors in a 'transparent' synthetic seabed. They were demonstrating a shear release of the shank to enable the anchor to be retrieved backwards - but it demonstrates admirably a diving anchor.

Jonathan