wearing out anchor

[seandepagnier]

I have worn out anchors where the shackle attaches to the anchor. Essentially the metal on the anchor wears away until there is very little remaining.

So I end up cutting this off and drilling a hole further up the shank to attach a shackle. unless this is a slot I then need two shackles to attach to chain and this could also reduce the performance of the anchor.


In any case... now with a new anchor, I put lashings here to protect the anchor metal from wear. Can anyone comment on this? I thought to somehow use aluminum, or lashing, but I am afraid the aluminum could actually eat away at the zinc galvanizing on the anchor and shackle. I may try something with aluminum on the fortress anchor, but for a galvanized anchor should I use zinc or? How can you protect the anchor from wearing out?

[Muaddib1116]

How long is it taking to wear out these anchors?

[JebLostInSpace]

I also want to know how quickly you are wearing them out! In about 15 months of nightly anchoring I didn't make any noticeable wear, although it did get pretty rusty.

As for protecting the hole or slot, I would imagine anything that you can fit in there securely will do the job. The difference will be in how often you have to replace. Lashings are easy to replace but won't last very long. A metal insert (aluminum or otherwise) will be much more difficult to make and install, but likely last much longer. My galvanized anchor rusted much more quickly than the attachment hole wore out, so not sure if the aluminum-steel reaction will make a meaningful difference.

For my money, I'd rather replace the lashings weekly. I always have scrap twine, but making/having made custom metal inserts is a challenge in some places. Also probably more expensive, but that's just a guess. It would depend on the relative wear rates.

I wonder if you would have the room to get a bit of pvc pipe to slip over the ring of the shackle. That might be more durable than a lashing but still be cheap if it would sit in place well.

Probably best to start cheap and simple, and see how long things last. If it's not a huge burden to replace lashings, there's no reason to go more complicated.

[kapnd]

Using a shackle that is close to the same size as the hole will likely reduce wear, if the shackle is rattling around in the bore, and not pulling straight.
Increasing the length/weight of the chain may help too, especially in lively conditions.

[seandepagnier]

Thanks for the responses.

It took 10 years of continuous anchoring until there was 1/8" of metal remaining and failure was imminent. By 6-7 years this was potentially a weak point though. This is in many storms etc. The anchor itself was also very rusted with large flakes falling off, however there was still metal for it to work.

Regardless, I do not want to wear out the anchor at all, or cause it to start rust at the wear point if possible.

I do use a shackle the proper size. I do not wish to use much chain on my anchor as this adds overall weight. I prefer to use larger anchor and more scope. I understand the tradeoffs with this, but I dont ust use more anchor.

Dyneema lashings did not last more than a few weeks at best. I could try adding many layers? I dont think pvc or even delrin would work that well because it will just get squeezed out from the force. Any ideas on this? I replace lashings but they just don't last. Perhaps some kind of zinc insert?

[Jammer]

Originally Posted by seandepagnier

I have worn out anchors where the shackle attaches to the anchor. Essentially the metal on the anchor wears away until there is very little remaining.

Which anchor? How many uses? First I've heard of such a thing.

So I end up cutting this off and drilling a hole further up the shank to attach a shackle. unless this is a slot I then need two shackles to attach to chain and this could also reduce the performance of the anchor.

Why not weld the hole shut and re-drill it? A simple procedure that takes all of 20 minutes in a capable shop, and preserves the original geometry and therefore performance.

[JebLostInSpace]

Dyneema for the lashings seems unnecessarily expensive. Any cheap twine would, I'm guessing, last approximately as long.

For the pvc idea, I was imagining it would slip over the shackle, and be long enough that it couldn't slide once the shackle is closed. It's possible the pvc would not be able to bend enough to follow the curve of the shackle. Maybe a bit of rubber hose?

It still feels strange to me that you are wearing them out so quickly. My anchor was about 5 years old when I bought the boat, although it didn't get a lot of use during that time. After 15 months of anchoring every night (well, just about every night), I'm definitely not 1/6 or even 1/10 of the way worn through. Maybe that's just the difference the chain makes, as I am typically anchored on all chain.

[kapnd]

You could use a bearing or bushing, but constant greasing would be required.
I’d likely just cut it off, drill a new hole, and forget about it for another decade!

[seandepagnier]

Originally Posted by JebLostInSpace

. My anchor was about 5 years old when I bought the boat, although it didn't get a lot of use during that time. After 15 months of anchoring every night (well, just about every night), I'm definitely not 1/6 or even 1/10 of the way worn through. Maybe that's just the difference the chain makes, as I am typically anchored on all chain.

I don't think after 15 months I would notice anything.. Also, not sure about pvc as it will just squeeze out.

I think you underestimate how much I anchored for 10 years in places like wellington new zealand, for example with the boat submarine at anchor going under waves. I anchored hundreds of days in gale force winds with 8ft waves and larger... and this was a cheap bruce knockoff anchor so maybe the metal itself is a softer steel than used in better anchors... After buying a rocna I just want to preserve it and avoid any wear completely if possible.

Originally Posted by kapnd

You could use a bearing or bushing, but constant greasing would be required.
I’d likely just cut it off, drill a new hole, and forget about it for another decade!

Yes.. but then the shank length is reduced which could reduce the effectiveness of the anchor. What I dont understand is why the anchors dont add extra meat in the metal there to anticipate the hole gradually working its way toward the end of the shank. There is enough space afforded by the shackle to double the amount of metal on the rocna design for example.

I also think the issue is more severe on a fortress aluminum anchor, so I definitely want to protect it.

[JebLostInSpace]

We must not be understanding each other on the pvc/rubber hose idea. The way I'm thinking of it, it would be impossible for it to "squeeze out." I'm thinking of a length of tubing that the entire bow of the shackle would go inside of. With the tube cut so that its two ends are tight against the pin of the shackle, I don't see how it could move. But admittedly that is asking for an awful lot of bend from pvc, hence the secondary idea of rubber hose.

Fair enough on why your anchors are wearing out btw. It's not like you're imagining it, I'm just surprised to hear about it is all. I certainly am not anchoring in such extreme conditions as you describe *shudder* that sounds absolutely miserable.

[seandepagnier]

I mean the shear force squeezing the plastic in compression would force it out. It simply cannot handle the compression for the area given. For example, there can be thousands of pounds of force, over a small area that even delrin can only support 2500lbs. So maybe, delrin could work for a while, until a major storm or something.

[JebLostInSpace]

I'm still not convinced you're getting my pvc concept, but I'll drop it since it has the bending issue I'm not sure how to solve.

Another idea I had though: Take a couple ~6" lengths of steel flat bar, say 1.5"x .25" or therabouts. Drill a hole through the anchor shank ~4" from the shackle hole, and bolt one end of each flat bar to the shank. Then drill holes in the other end of the flat bars to match up with the position of the shackle hole. You have essentially added stock to the shank in the worrisome location.

Once the hole wears a tiny bit, the load should distribute between the shank and the new flat bar material pretty evenly. The load on the flat bars will transfer to the bolt. Wear from the plain tension on the rode will be split between the bolt hole and the shackle hole. Wear from the rotation and rubbing of the shackle will be split between the shackle hole and the flat bars. Won't eliminate wear but probably doubles your lifespan at a guess.

[sailorboy1]

Originally Posted by seandepagnier

It took 10 years of continuous anchoring until there was 1/8" of metal remaining and failure was imminent.

you waited that long on a boat critical item

My anchor is 12 years old and the last 5.5 years I have been full time on it. I don't see any wear at the shackle location.

[PippaB]

How about a sleeve made of Monel tubing? That's how my chainplates were built 20+ years ago. The stuff is expensive, but you need, what, 1/2"-1" (1-2cm)? The difficulty would be finding the right OD to match the hole in the shank. McMaster has 1/2" OD, a foot length is $30-40. Make up a dozen bushings/sleeves and change them out every couple of years - last you a lifetime.

[Muaddib1116]

Originally Posted by seandepagnier

I think you underestimate how much I anchored for 10 years in places like wellington new zealand, for example with the boat submarine at anchor going under waves. I anchored hundreds of days in gale force winds with 8ft waves and larger...

Sounds terrible. I probably would have moved somewhere more protected.

Originally Posted by seandepagnier

What I dont understand is why the anchors dont add extra meat in the metal there to anticipate the hole gradually working its way toward the end of the shank. There is enough space afforded by the shackle to double the amount of metal on the rocna design for example.

The reason is that it makes it hard/impossible to get the shackle bow through the slot. Most people prefer to have the shackle bow through the shank slot rather than the shackle pin. That being said, check out the Sarca Excel, they have extra material at the shank slot. I had to use a bolt and steel plate to spread the bow of my Crosby shackle apart to get it wide enough to fit.

Originally Posted by JebLostInSpace

I'll drop it since it has the bending issue I'm not sure how to solve.

Heat gun.