Which resetting anchor should I go for ??

[Ariadne]

This is now the Rocna lovers/haters willy waving thread , thank you for your comments, take it to PM kids.

Leave the thread for people who are not polarised in their opinions about anchors....

 

[GHA]

This is now the Rocna lovers/haters willy waving thread , thank you for your comments, take it to PM kids.

Leave the thread for people who are not polarised in their opinions about anchors....

Fair call. Well worth keeping an open mind.

Now what was the question again :-D.

 

[catmandoo]

This is now the Rocna lovers/haters willy waving thread , thank you for your comments, take it to PM kids.

Leave the thread for people who are not polarised in their opinions about anchors....

i too have had experience of thixotropic mud with anchor slipping after a steady load had ben applied for some time .

On the subject of Rocna anchors , I have one! as well as a CQR , a Bruce and and a Danforth all about the same dead weight ; but I prefer the Rocna over all the others which I keep as backups with the exception of the 'genuine" Bruce which I am currently trying to get rid of as SWMBO keeps tripping over it .

If I was worried about the Rocna shaft bending then I might be inclined to weld stiffeners at 90 degrees down the middle of both sides of the shaft to counteract any bending moment that might be applied due to constant sideways pull , shock or otherwise ; or maybe I will sink under the weight of all the anchors .

However surely as long as it holds in an extreme case I don't care if its bent or not . I would just replace it with a new one or with a stronger ( heavier?)one or having learned its limitations just replace it as before and just let out more chain to absorb shock loads due to heavy swell in heavy weather .

(Interestingly early this year some boats in the Dodecanese when tied to buoys with concrete blocks below on short ropes to the deck in an unexpected Southerly 40 knots and and heavy swell applied such an up ward load to the concrete that it slipped and started to slide along the seabed)

Any way to return to an anchor I wonder in the case of a stronger shaft what value the sideways load should be to design this stronger one against ?

Does anybody have a value per boat length or windage area or is it just as we all suspect a rule of thumb and a feeling in the water ( excuse the pun)

Seems to me that there are a lot more factors to consider than only a material specification - anchor weight , length and size of chain , type of bottom ,depth, wind and height of swell etc etc

 

[Delfin]

i too have had experience of thixotropic mud with anchor slipping after a steady load had ben applied for some time .

On the subject of Rocna anchors , I have one! as well as a CQR , a Bruce and and a Danforth all about the same dead weight ; but I prefer the Rocna over all the others which I keep as backups with the exception of the 'genuine" Bruce which I am currently trying to get rid of as SWMBO keeps tripping over it .

If I was worried about the Rocna shaft bending then I might be inclined to weld stiffeners at 90 degrees down the middle of both sides of the shaft to counteract any bending moment that might be applied due to constant sideways pull , shock or otherwise ; or maybe I will sink under the weight of all the anchors .

However surely as long as it holds in an extreme case I don't care if its bent or not . I would just replace it with a new one or with a stronger ( heavier?)one or having learned its limitations just replace it as before and just let out more chain to absorb shock loads due to heavy swell in heavy weather .

(Interestingly early this year some boats in the Dodecanese when tied to buoys with concrete blocks below on short ropes to the deck in an unexpected Southerly 40 knots and and heavy swell applied such an up ward load to the concrete that it slipped and started to slide along the seabed)

Any way to return to an anchor I wonder in the case of a stronger shaft what value the sideways load should be to design this stronger one against ?

Does anybody have a value per boat length or windage area or is it just as we all suspect a rule of thumb and a feeling in the water ( excuse the pun)

Seems to me that there are a lot more factors to consider than only a material specification - anchor weight , length and size of chain , type of bottom ,depth, wind and height of swell etc etc

As noted above, if you have a Rocna, it is either one of those made in NZ of Bisalloy 80, one made in China of varying strengths, but none as strong as Bis 80, or one of the new ones, still not as strong as Bis 80, but within 15% or so. Shank bending isn't a problem with any anchor until it is, then as you say, you can get another anchor. For those buying a new hoop anchor the choice is between a (hopefully) cheaper but weaker Rocna, or a stronger Manson Supreme. Both are fine anchors and in a straight pull, both will hold up as well as the other. Unfortunately, anchoring isn't always a matter of straight pulling.....

Regarding "value per boat length or windage", Alain Fraysee's Excel spread sheet lets you do the calculations yourself to determine what you need in ground tackle. These values compensate for windage and displacement and seem accurate to me. Since the force that any decently set 3rd generation anchor will provide is vastly greater than the force required to bend a shank, shank strength does become a factor to be considered. The recent Practical Sailor article details how trivial the loading has to be to deform a shank. I don't know for sure, but I believe that any hoop increases the likelihood of shaft bending because the hoop resists rotation during wind shifts. If you want the strongest shank, the Knox is your choice. After that, lots of choices and designs. Sounds like with your collection, you pretty much have the field covered....

 

[NormanS]

Or, if you're really concerned about the shank bending, above all else, get a CQR. After all, the hinge must make it very difficult to have it bend.

 

[vyv_cox]

Or, if you're really concerned about the shank bending, above all else, get a CQR. After all, the hinge must make it very difficult to have it bend.

Quite difficult to bend the shank of an anchor that will not set in the bottom, unless, of course, it snags between some rocks. In that case you won't recover it, something of a problem as it is so extremely expensive.

 

[NormanS]

Quite difficult to bend the shank of an anchor that will not set in the bottom, unless, of course, it snags between some rocks. In that case you won't recover it, something of a problem as it is so extremely expensive.

Glad to see that your post has a smiley, because as you very well know, it's nonsense. Generations of sailors have used CQRs sucessfully. There may be more modern anchors which may be better, but there are lots of boats still using CQRs.

 

[catmandoo]

. Since the force that any decently set 3rd generation anchor will provide is vastly greater than the force required to bend a shank, shank strength does become a factor to be considered. The recent Practical Sailor article details how trivial the loading has to be to deform a shank. I don't know for sure, but I believe that any hoop increases the likelihood of shaft bending because the hoop resists rotation during wind shifts. If you want the strongest shank, the Knox is your choice. After that, lots of choices and designs. Sounds like with your collection, you pretty much have the field covered....

so whats all the fuss about shaft bending then as any shaft will as you say bend at some level or other before the set gives way . Up to that instance it becomes part of the chain / flexible tackle and still holds fast

 

[catmandoo]

seriously though the load limitation of the shank should really be equivalent to its maximum holding capacity what ever that is . I would not expect it to be less regardless of what material was used in the shank .

on the other hand the resulting deflection of a bent shaft under extreme conditions might also be considered to be a good thing by some designers as it might result in favourable re- distribution of the load path

 

[Delfin]

Or, if you're really concerned about the shank bending, above all else, get a CQR. After all, the hinge must make it very difficult to have it bend.

If you Goggle 'bent CQR', you'll come up with some examples of why that may not be the case.

 

[Delfin]

seriously though the load limitation of the shank should really be equivalent to its maximum holding capacity what ever that is . I would not expect it to be less regardless of what material was used in the sha
on the other hand the resulting deflection of a bent shaft under extreme conditions might also be considered to be a good thing by some designers as it might result in favourable re- distribution of the load path

I'm afraid youre going to be dissapointed if you think you can find many anchors whose resistance to the shank bending is anywhere close to the holding capacity. The Sarca Excel qualifies, but I don't know of another. Consult the recent Practical Sailor article on the subject for details.

Regarding a bendable shank as a design benefit, that's a bit like saying an exploding Space Shuttle is a design feature because it reduces the wear and tear on the runway.

 

[Cariadco]

No problem, it's at least three weeks since the last one, we did flag etiquette last week so it's catamaran vs monohull next

...or Bavarias....

 

[sailorman]

If you Goggle 'bent CQR', you'll come up with some examples of why that may not be the case.

cast iron copies of the CQR will break rather than bend like the genuine drop forged CQR that will bend without breaking the shank

 

[catmandoo]

I'm afraid youre going to be dissapointed if you think you can find many anchors whose resistance to the shank bending is anywhere close to the holding capacity. The Sarca Excel qualifies, but I don't know of another. Consult the recent Practical Sailor article on the subject for details.

Regarding a bendable shank as a design benefit, that's a bit like saying an exploding Space Shuttle is a design feature because it reduces the wear and tear on the runway.

Not necessarily an item can bend ie deflect and even take up some permanent set but not necessarily part company with the rest of the construction

 

[Chris_Robb]

Not necessarily an item can bend ie deflect and even take up some permanent set but not necessarily part company with the rest of the construction

The point about the Manson Rocna etc is that if they are not symmetrical in their shape, the anchor will simply not set and will role out. Indeed even Rocna had to reject quite a few chinese jobs that were not built straight.....

So it is not about bending being ok, its about bending making the anchor useless.

 

[catmandoo]

The point about the Manson Rocna etc is that if they are not symmetrical in their shape, the anchor will simply not set and will role out. Indeed even Rocna had to reject quite a few chinese jobs that were not built straight.....

So it is not about bending being ok, its about bending making the anchor useless.

There is a fallacy there because the anchor bent because it would not move due to a sideways thrust . I would accept your statement if the anchor then gave way and could not reset because of a bent stock .

in either case the anchor is not reusable but in the former case it still held

 

[Delfin]

There is a fallacy there because the anchor bent because it would not move due to a sideways thrust . I would accept your statement if the anchor then gave way and could not reset because of a bent stock .

in either case the anchor is not reusable but in the former case it still held

Entirely speculative. In a wind shift and if the shaft of a hoop anchor bends there is far less likelihood that it will hold since the leverage is now at an oblique angle to the throat angle of the flukes. It may continue to hold, it may not, probably depending on whether it bent because it was rock jammed or whether the hoop prevented free rotation. The point is that to argue that a bent shank somehow has no impact on holding is spurious at best.

 

[Chris_Robb]

There is a fallacy there because the anchor bent because it would not move due to a sideways thrust . I would accept your statement if the anchor then gave way and could not reset because of a bent stock .

in either case the anchor is not reusable but in the former case it still held

Did it still hold..... You seem to have missed my point. Once the stock is bent, the anchor is no longer in symmetry and in all likelihood will role out especially with a change of direction, but also with a straight pull.

You seem to be set on defending the indefensible!

 

[catmandoo]

deflection and distortion etc

Did it still hold..... You seem to have missed my point. Once the stock is bent, the anchor is no longer in symmetry and in all likelihood will role out especially with a change of direction, but also with a straight pull.

You seem to be set on defending the indefensible!

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

 

[Delfin]

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% ?

15% minimum for the current production, 40% or so for the period of time that Rocna was using whatever steel they wanted while lying to people about what they were using.

2 is it under impact loading or continuous pull ?

Clearly both. If the steel is weaker it is weaker at all times under all loads.

3 When do any of these become significant enough to influence the design purpose of the anchor and even its individual bits ?

You might as well ask how long a piece of string is. Weaker becomes important when weaker becomes important.

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 .

Pretty much incoherent. And no, just because an anchor deforms does not mean it is 'stable'. As has been explained a few times, once deformed, the anchor is probably toast and is not going to stay put in the current set unless it is jammed under a rock or something. However, much will depend on the degree of bend, which is why the question doesn't mean much.

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 ?

Also incoherent. I have no idea what this means.

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

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.

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

Don't think anyone said that, but again, how long is a piece of string? How bent? What anchor design? The CQR doesn't perform well at all in resetting during wind shifts, at least according to the tests I have seen.