Which resetting anchor should I go for ??

[Chris_Robb]

Not so! just making an assumed comment as you did when you said 'in all likelihood"

In my experience of life i learned that it was fatal to make any unsupported assumptions when designing anything particularly when sitting in an armchair commenting in a forum .There is black and white and various shades of grey in the real world depending on the circumstances and there are a lot of variables to look at .
For instance nothing is infinitely stiff and all things deflect under load . so a shaft can bend sideways under load and return unscarred unless the load is big enough to induce permanent set . So one has to be specific about what one means about bending

In consequence I might want to ask my self the following questions to get a better picture of the prevailing conditions in any one circumstance
1 what is the difference in strength of the stock material under bending between the original specification and the Chinese steel - 5%. 10% 20% ?
2 is it under impact loading or continuous pull ?
3 When do any of these become significant enough to influence the design purpose of the anchor and even its individual bits ?
4 if such a side ways load does cause permanent set at one point then the anchor is stable up to that point because the shaft will just spring back with out deformation and on that basis the rest of the anchor even when deflected does not need to reset because it had a strong enough holding to resist the pull in the first case .
5 looking it another way on the anchor as a whole with design spec steel a side ways load when applied will cause the shaft to deflect in the same way and if resetting there is a case for it doing so under load with the shaft still deflected but not set so what is the difference between one set of bending and another ?
6 and how do you know that it will not fully align itself in the direction of pull on some degree of bending . It must be capable of doing that other wise the design is rubbish

7 is there any evidence to support your argument that an anchor with any degree of deflection in its shaft will not reset ? CQR's have a hinge

So if you have any specific data to refute the above completely then I will revert

cheers

Oh god! This must be a troll....... Can't be bothered to reply. However its a free world and anyone can go and buy an anchor made of any substandard rubbish they wish, and pay for good stuff. - its up to them

Bye bye

 

[GHA]

If it is a hoop anchor, its ability to reorient when the hoop is buried is limited by the resistance of the hoop to rotation, increasing the chance that the side loading will result in deflection. This is probably why Peter Smith used to say that Bisalloy 80 - very springy steel - was mandatory for his design. Until it wasn't. Manson still considers it so, which is why they use it.

Is there any evidence to back up those 3 statements?

 

[Delfin]

Is there any evidence to back up those 3 statements?

Yes, Troll. The Rocna website before they were caught lying about their steel. Then it changed. Troll elsewhere, please.

p.s. Love the Wayback machine. Helps identify trolls, and find the tracks people hide when they say one thing and do another. Enjoy!

View attachment 33861View attachment 33862

p.p.s. Regarding Manson's material, I suggest you look at their website. For the question of whether a buried hoop in sand resists rotation along the 'x' axis, I suggest you consult Newtonian physics.

You're on you own now....

 

[GHA]

For the question of whether a buried hoop in sand resists rotation along the 'x' axis, I suggest you consult Newtonian physics.

You're on you own now....

the second 2statements were in regard to your assertion that a hoop anchor buried is LIMITED by the hoop resistance to rotation, a request for evidence of this came up with nothing. as the hoop has a circular profile and has a very small surface area compared with the shank and flukes it seems unlikely for the hoop to have a significant additional resistance to rotation. Certainly nowhere near a limiting factor. Unless you have evidence to prove otherwise.

A quick search through both the rocna and Manson sites came up with nothing about higher tensile grade steel being used in the shank because of the hoop creating extra resistance to rotation.

If you keep making authoritarian statements with nothing to back them up don't be surprised if you get pulled up about it.

 

[Delfin]

the second 2statements were in regard to your assertion that a hoop anchor buried is LIMITED by the hoop resistance to rotation, a request for evidence of this came up with nothing. as the hoop has a circular profile and has a very small surface area compared with the shank and flukes it seems unlikely for the hoop to have a significant additional resistance to rotation. Certainly nowhere near a limiting factor. Unless you have evidence to prove otherwise.

A quick search through both the rocna and Manson sites came up with nothing about higher tensile grade steel being used in the shank because of the hoop creating extra resistance to rotation.

If you keep making authoritarian statements with nothing to back them up don't be surprised if you get pulled up about it.

Having demonstrated a certain inability to put together a coherent English sentence, I guess it's not surprising you also have difficulty reading the language as well. I'll leave you to your studies troll, and best wishes.

 

[GHA]

Having demonstrated a certain inability to put together a coherent English sentence, I guess it's not surprising you also have difficulty reading the language as well. I'll leave you to your studies troll, and best wishes.

As you haven't even tried to back up assertion below with either evidence or basic physics it seems prudent to treat it with caution. This is one way urban myths begin.

If it is a hoop anchor, its ability to reorient when the hoop is buried is limited by the resistance of the hoop to rotation, increasing the chance that the side loading will result in deflection.

 

[vyv_cox]

As you haven't even tried to back up assertion below with either evidence or basic physics it seems prudent to treat it with caution. This is one way urban myths begin.

Is it not self-evident that if I take two identical hoop anchors, cut the hoop off one, dig them into the sand and then try to turn them, the one with the hoop will offer greater resistance to rotation than the one without?

 

[GHA]

Is it not self-evident that if I take two identical hoop anchors, cut the hoop off one, dig them into the sand and then try to turn them, the one with the hoop will offer greater resistance to rotation than the one without?

That certainly is, but having the hoop as a limiting factor to resistance isn't so obvious. Even a simple visualisation suggests wouldn't do much, looking at the ratio of the hoop area to the rest of the anchor. How much the hoop might increase the rotational resistance anyone's guess, quite possibly insignificant. But I've been wrong many times so asking if there is some evidence around didn't seem that out of order. A simple no would have been fine. Or a yes would have been interesting and we all might have learned something. Looks like no.

 

[vyv_cox]

I cannot argue with that. AFAIK the hoop's primary purpose is to restore the anchor to the upright position if it should fall on its back. Like you, I cannot believe that it offers a lot of resistance to rotation, particularly as mine is rarely below the surface. In soft mud it certainly has been but in this case the conditions necessary for shank bending are probably not present.

 

[catmandoo]

Yes, Troll. The Rocna website before they were caught lying about their steel. Then it changed. Troll elsewhere, please.

p.s. Love the Wayback machine. Helps identify trolls, and find the tracks people hide when they say one thing and do another. Enjoy!

View attachment 33861View attachment 33862

p.p.s. Regarding Manson's material, I suggest you look at their website. For the question of whether a buried hoop in sand resists rotation along the 'x' axis, I suggest you consult Newtonian physics.

You're on you own now....

A lot of hot air on this thread including some hot collars

however I have a Rocna and am quite satisfied with its performance , not ideal but what anchor is ? Its slipped a few times mainly on sand over rock and recently diving down I saw it scudding over the bottom on its side at best making a shallow groove on the substrate .
(Rock No ?) I also have three other types as back up and once laid the Bruce by jumping over board with it in my arms and submerging it in the right direction in a hole I dug in the sand in 4 metres of water . Even my CQR is not trustworthy

too many variables to get the ideal one



I'm a troll , bowly roll ,
I'm a troll , bowly roll
And I''l eat you for my supper

 

[Delfin]

Is it not self-evident that if I take two identical hoop anchors, cut the hoop off one, dig them into the sand and then try to turn them, the one with the hoop will offer greater resistance to rotation than the one without?

One would think so, yes. The degree to which a hoop puts additional stress on a shank in rotation is going to depend on the seabed and how deeply the anchor is buried. If completely submerged, the sea bed will support the shank, which is one reason I favor a burying anchor without a hoop. The worst case is probably in conditions where the flukes are submerged and the shank not. I suppose it was in anticipation of those conditions that Smith specified the essential need for Bisallow 80, or equivalent, as I understand your older Rocna has. When they veered from that spec, they ran into problems. Whether the weaker, but still pretty robust steel they are using now will also present problems is unknown, but time will tell. I would be less concerned about a hoopless anchor shank made of Q620, like the Tern, than I would a hoop style, for the self evident reasons noted.

I suppose the hoop design is also a factor in the degree to which it would contribute to the potential for bending. I remember corresponding with Rex Francis about his hoop anchor, the Super Sarca. His shank on that anchor is not Bis 80, like the Excel, but he pointed out how thin the hoop was; designed to offer less resistance to burying and less resistance to rotation. I believe he feels that the convex fluke design of the Super Sarca also assists in getting it buried, which ultimately will support the shank if side loaded. The Mantus seems like the weakest of the lot, and Practical Sailor recently made similar observations. Its hoop is really big; the anchor bites in and holds well, but the cross section of an already large hoop will, in some conditions, no doubt offer a lot of resistance to rotation. With a mild steel shank I have to think you're going to see some bent Mantus anchors. We'll see.

 

[GHA]

I cannot argue with that. AFAIK the hoop's primary purpose is to restore the anchor to the upright position if it should fall on its back. Like you, I cannot believe that it offers a lot of resistance to rotation, particularly as mine is rarely below the surface. In soft mud it certainly has been but in this case the conditions necessary for shank bending are probably not present.

End of the day they all do their job very well and there is so little data on bent shanks that it's impossible to know if a hoop has ever been involved or not. Better off in the bar talking about favorite anchorages there are things to worry about which might actually happen