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-   -   Poor little anchor (https://www.cruisersforum.com/forums/f118/poor-little-anchor-236765.html)

Izikalvo 10-07-2020 03:01

Poor little anchor
 
1 Attachment(s)
bumped into this photo in one of the FB groups.

Different metals are different in strength and their metallurgical quality, these factors are defined in the factory where they are made as raw material from the initial form of iron.
The mechanical process (casting, forging, milling, and such) while processing the metal can also have a large impact on metal characteristics, behavior, and quality.
Choosing the right steel to build anchors is a compromise, the grade of the steel, the weight, and the price, higher tensile metals are a lot more expensive and are harder to cut, bend and weld.
The shank on any anchor is a common failure point,. The most venerable and weak issue is bending it when a high lateral load is applied to the anchor. This can happen, for example, when the wind direction suddenly changes, pushing the boat sideways.
Looking to minimize the occurrence of such events, we should use only high-grade high-tensile steel made anchors. Due to their design (new generation anchors) the higher the tension on the anchor increases the burial of the anchor leaving less or no shank exposed. If there is a lateral tension applied our shanks, being buried, act as a vertical fluke supported by the seabed.

OloteleMtn 10-07-2020 03:42

Re: Poor little anchor
 
A little hammer and anvil action will set it right.

Group9 10-07-2020 03:44

Re: Poor little anchor
 
Well, on the positive side, it does look like it was dug in well!

Izikalvo 14-07-2020 08:33

Re: Poor little anchor
 
This round bend is very unusual and due to its shape I suspect this shank and maybe the whole anchor is made of aluminum, carbon steel almost always bends more on its weakest point when too much force is sideloaded.

dfelsent 14-07-2020 08:52

Re: Poor little anchor
 
Looks like stainless steel to me with that highly polished finish.

BlackHeron 14-07-2020 09:29

Re: Poor little anchor
 
Looks like a soft stainless steel like what silverware is made of. This is probably what happens when materials are chosen for cosmetic reasons over strength and rigidity.

Shrew 14-07-2020 09:38

Re: Poor little anchor
 
I assume the fluke was caught on something, like a rock to cause this to occur. The anchor should be designed to do this. There is a balance where too strong also becomes too brittle.

Would it be preferable to break rather than bend??

barnakiel 14-07-2020 09:47

Re: Poor little anchor
 
I prefer a bend. You are still anchored. If it breaks, you may end up on the rocks.


Just looking at the image you can see the shank is under-dimensioned. imho


(edited)


barnakiel

Bill O 14-07-2020 10:03

Re: Poor little anchor
 
Quote:

Originally Posted by Shrew (Post 3185795)
I assume the fluke was caught on something, like a rock to cause this to occur. The anchor should be designed to do this. There is a balance where too strong also becomes too brittle.

Would it be preferable to break rather than bend??


Agree it had to be hung up on something solid and would rather it come up looking like a pretzel rather than break.

Shrew 14-07-2020 10:17

Re: Poor little anchor
 
I've seen a number of these pics before. I am continually surprised that an anchored boat would be able to exert this much force on the anchor shank. There are really only two ways this could occur on anchor...Wind...or Windlass.

In the case of either wind or windlass, the boats hull was able to secure itself against the water to be able to bend the shank? My windlass certainly doesn't have this much pulling power. I'd be surprised if the wind did as well.

Id' be more apt to speculate that this was the result of a docking mishap. Boat running into a seawall, piling or another boat. I've seen plenty of anchors and bow pulpits tweaked in these scenarios.

I have to wonder if this is an example of a real-world anchoring scenario or something else. As Paul Harvey used to say "......the rest of the story".

Dockhead 14-07-2020 13:59

Re: Poor little anchor
 
Quote:

Originally Posted by Izikalvo (Post 3182498)
bumped into this photo in one of the FB groups.

Different metals are different in strength and their metallurgical quality, these factors are defined in the factory where they are made as raw material from the initial form of iron.
The mechanical process (casting, forging, milling, and such) while processing the metal can also have a large impact on metal characteristics, behavior, and quality.
Choosing the right steel to build anchors is a compromise, the grade of the steel, the weight, and the price, higher tensile metals are a lot more expensive and are harder to cut, bend and weld.
The shank on any anchor is a common failure point,. The most venerable and weak issue is bending it when a high lateral load is applied to the anchor. This can happen, for example, when the wind direction suddenly changes, pushing the boat sideways.
Looking to minimize the occurrence of such events, we should use only high-grade high-tensile steel made anchors. Due to their design (new generation anchors) the higher the tension on the anchor increases the burial of the anchor leaving less or no shank exposed. If there is a lateral tension applied our shanks, being buried, act as a vertical fluke supported by the seabed.


It's a fool's errand trying to solve that problem with better metal. That construction -- a simple piece of flat plate for a shank -- is not made to resist side pulls. You will only get an incremental improvement with better metal.


If you want the anchor shank to resist a side pull, then you need to build it up in three dimensions the way Spade and Ultra do. This is basic mechanical engineering.



I've bent a couple of anchor shanks designed like that -- one Rocna, and one Delta. The only reason to build an anchor that way is that it is cheap to simply cut it out of flat plate steel. Cheap, but not good.

Cheechako 14-07-2020 14:09

Re: Poor little anchor
 
The good news: That fluke shape holds well enough the shank bends instead of the anchor losing it's grip!
The bad news: Shank built too thin! It will be work hardened when you straighten it out and be stronger! Better yet, weld a strip on the top of the shank making it a T shape.... giving some lateral strength.

barnakiel 14-07-2020 14:15

Re: Poor little anchor
 
Quote:

Originally Posted by Shrew (Post 3185842)


In the case of either wind or windlass, the boats hull was able to secure itself against the water to be able to bend the shank? My windlass certainly doesn't have this much pulling power. I'd be surprised if the wind did as well.



Look again.


I bet it was bent while the chain was tight and the boat lifted on a swell.


The material used is simply not man enough in this direction - make a simple model then pull the shank upwards. What happened? It twisted just like this, eh?


There is a mechanical word for this (failure mode) that I cannot recall (warp???). But it is a simple question of pulling this kind of under sized shank UP-wards.


b.

Jim Cate 14-07-2020 14:26

Re: Poor little anchor
 
Quote:

If you want the anchor shank to resist a side pull, then you need to build it up in three dimensions the way Spade and Ultra do.
But, of course, when you do this the anchor becomes harder to bury. One of the reasons that Manson and other mfgs use Bisaloy 80 or other very stiff alloys for their shanks. Stiffness does matter...

And looking at the example shown upthread, hard to believe that bend was made by a upward pull on a stuck anchor. Had it been done so, the shank would be twisted as well as bent sideways. Actually looks kinda phony to me... too perfect a bend to have just happened in nature! Wouldn't bet the farm on it, though.

Jim

Dockhead 14-07-2020 15:16

Re: Poor little anchor
 
Quote:

Originally Posted by Jim Cate (Post 3186030)
But, of course, when you do this the anchor becomes harder to bury. . .


I don't think so. Look at a Spade or Ultra shank and tell me how that is so much harder to bury. It does not require much increase in volume, to get structural strength.



For that matter, look at the shank of the hated CQR -- it's a forged I-beam construction, also strong.



All of this is inherently stronger and better than the simple cut out flat plates of many modern anchors. The ONLY reason to build them like that is cheap and easy manufacturing.


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