Poor little anchor

[a64pilot]

My point is, if you bent an anchor in anything except extremely unusual conditions, say anchored in a hurricane for instance, you have either a poorly made or constructed anchor, or its undersized. Most I don’t think about size = strength, just holding ability.

We seem to want to size anchors based on their holding ability alone, however it’s pretty safe to say that the modern anchors can when weights are equal, develop significantly more holding power than traditional designs, I mean that’s why we buy them, right?

However maybe they can develop so much holding power that in unusual circumstances they can exceed their ultimate strength, and bend or break.

About the only thing a consumer can control about anchors is size, so what I’m saying is that maybe choosing anchor sizing also is a function of Ultimate strength as well as ultimate holding.

According to my anchors manufacturer, my anchor on a boat my size is good for up to 60 metric tons, but my boats weight is roughly 10 metric tons, also according to the manufacturer, I should be using 7/16” chain, but I use 5/16”.
It’s unlikely that I can / will bend a shank, or stretch or break chain either.

There will always be a weak link, the trick is to move the ultimate failure point of the weakest link to outside of the realistic load.

Currently it would seem that the anchor shank is that weak link, so I’m saying increase the strength of that link until it’s outside of the loads your capable of generating.

Or accept the fact that once in a blue moon, it’s possible that your going to bend a shank if you don’t want excess weight on the bow.
Or buy an alloy anchor

[BlackHeron]

Shock loads can be controlled with longer snubbers and longer scope. A 30' nylon snubber can reduce shock loads by 60% or more. And yes, these shock loads can bend anchor shanks.

The shank, pulling at an angle can become the spot that gives when a heavy displacement vessel is lifted by a wave a few feet with a taught chain and the whole boat, say 30,000 pounds maybe needs to be jerked forward a few feet as it goes up with the water.

This is simple right-triangle geometry. If the depth goes up very quickly the distance between the boat and the anchor must shrink accordingly over that same time period. The shorter the scope the more the boat needs to scoot forward to compensate for being lifted. How much force does it take to move a 30,000lb boat forward a few feet in the space of a couple of seconds?

[Manateeman]

So would someone please help me out here. The original poster is a guy who manufactures Viking anchors...post a photo of a bent anchor by what looks like another manufacturer...then adds his opinion on metallurgy, and anchor design.
Subsequently, lots on other opinions are posted.
So...what’s the point...I think it’s : buy an anchor with real strength in the shank.
Ok but when I get rid of my two main anchors and buy a 1,000 lb Dor-Mor, two things are going to happen. First, I’ll have to add 1,000 lbs of lead in the stern.
Second, I’ll have to pay a huge fine for disturbing the habitat of Federally protected manatees.
Yup. Dor-Mor = snore more.
Mark a snooze worthy manatee.

[barnakiel]

There is no need to make shanks in flimsy sheet metal and justify this as 'penetrating better'.


Any old Bruce anchor has its shank wedge shaped - narrow section down, wide part up. Penetrates as good or better than a sheet metal shank, and DOES NOT BEND.


b.

[a64pilot]

I don’t think anyone uses sheet metal. But I did have a rather strange anchor, a Danforth HT anchor.
Odd ball anchor, I think HT must have stood for High Tensile?
Anyway the shank on this thing couldn’t have been much more than 1/8” thick, maybe 1/4”. I’m pretty certain that it was essentially spring steel and that you could put enough force on it and it would bend over, and then recover when the force was released, I believe it was essentially a leaf spring from a car.
So that’s one way, another is of course the knuckle joint in a CQR.

But neither is main stream, why? Well it’s my belief that bending an anchor is pretty uncommon, so to cover those unlikely events if your really a quality manufacturer and want to keep a stellar reputation, you have a warranty that says, you bend it or break it in any manner, and we will replace it, no questions asked. Other wise your designing and manufacturing for a 1 in a million event, or 1 in 100,000 whatever.

I have a back up plan though, this is it, if I get it hung, I’ll dive it, tie on a line and pull it up backwards. Or if I’m anchoring where I know there are abandoned moorings or other trash that can trap an anchor I tie the line on before I anchor.
I’ve only done that once because I’d rather avoid an area like that.

[Don C L]

Originally Posted by noelex 77

A larger anchor tends to be more difficult to retrieve in my experience. There is generally not any need to use any more force, unless the wind has been very strong, but you have to wait longer with steady pressure.

Yes, I guess in the sense that you are trying to lift more sand given the greater surface area of the flukes? But then a really deeply buried smaller anchor is trying to lift a lot too... hmmm interesting...more testing needed perhaps?

[barnakiel]

Originally Posted by a64pilot

I don’t think anyone uses sheet metal.

(...)

I see. But how do you call the material used in the #1 and in Rocnas, Mansons shanks, then? Plate?


To me, they look cut out from plain piece of flat rolled steel. Which I tend (perhaps mistakenly) to call sheet steel or plate steel.


?



b.

[barnakiel]

Originally Posted by Don C L

Yes, I guess in the sense that you are trying to lift more sand given the greater surface area of the flukes? But then a really deeply buried smaller anchor is trying to lift a lot too... hmmm interesting...more testing needed perhaps?

I noticed something maybe odd and would like to hear what you say.


Namely, when the anchor is well dug in, we tend to get right over it then lock the rode.


From this point, many boats will put slowly in forward (most cruisers and charters lift anchors under power).


However, I grew up sailing boats (engine-less that is) and today also in a boat with engine, I tend to do the opposite - put in REVERSE.


Oddly enough, never seem to fight it, or bend anything - the anchor tends to come out smooth and easy.


So, to sum it, is there any reason to force it out in forward gear while a very gentle tug backwards does exactly the same job?


Regards,
barnakiel

[rslifkin]

To break an anchor out, I typically get the rode vertical, let the windlass pull it tight-ish, and just sit and wait a minute. A slight bump on the windlass up button confirms if it's free or re-tensions, then sit for another minute. In my experience, something like a Fortress or Danforth typically needs some boat movement in some direction or another to break it free. For many others, if there's a little bit of wave action or some boat wakes, that's usually enough, engines only needed for break out in dead calm conditions.

Breaking or bending stuff happens when you get impatient and start trying to get it out quickly, rather than letting it dig itself back to the surface.

[noelex 77]

Originally Posted by Don C L

Yes, I guess in the sense that you are trying to lift more sand given the greater surface area of the flukes? But then a really deeply buried smaller anchor is trying to lift a lot too... hmmm interesting...more testing needed perhaps?

Anchor theory indicates that for any given setting force, the weight of substrate in the failure wedge should be the same.

This suggests that the difficulty breaking out the anchor should be the same irrespective of the anchor size (ignoring the dead weight of the larger anchor and providing a smaller anchor does not exceed its ultimate holding power for the particular substrate ). However, larger anchor sizes are less likely to skip, jump and drag when setting, as well as efficiently penetrating difficulty substrates such as weed. In other words they more effectively translate the setting force generated by the boat directly into increasing the size of substrate failure wedge, creating a heavier failure wedge. This will be more difficult to break out. This is what is seen in practice.

This is especially true after stronger wind. As the smaller anchor starts to approach its ultimate holding power, the anchor will tend to become very inefficient at translating the force into diving deeper into the substrate, sometimes slowly dragging or at least moving a long way through the substrate while only digging in slightly deeper. Eventually it will have reached its ultimate holding power and maximum diving depth and it will break out (it is very easy to retrieve at this stage ) . The larger anchor will (hopefully) not have reached its higher ultimate holding ability and will still will be at the stage where a higher force is efficiently translated into diving deeper.

The substrate failure wedge is well illustrated in the photo below from the Vryhof anchor manual.

[Don C L]

Originally Posted by barnakiel

I noticed something maybe odd and would like to hear what you say.


Namely, when the anchor is well dug in, we tend to get right over it then lock the rode.


From this point, many boats will put slowly in forward (most cruisers and charters lift anchors under power).


However, I grew up sailing boats (engine-less that is) and today also in a boat with engine, I tend to do the opposite - put in REVERSE.


Oddly enough, never seem to fight it, or bend anything - the anchor tends to come out smooth and easy.


So, to sum it, is there any reason to force it out in forward gear while a very gentle tug backwards does exactly the same job?


Regards,
barnakiel

I think that is right. If you are right over the anchor I think it should be easier on the anchor and just as fast to pull in reverse, though that may seem counterintuitive. Even pulling straight up on the anchor, being right over it and cleating off or locking the rode can put a huge strain on the shank unnecessarily if the bow is bobbing with a swell. Pulling in reverse is still going to dislodge the anchor without trying to bend the shank, I'd say.

[Don C L]

Originally Posted by noelex 77

Anchor theory indicates that for any given setting force, the weight of substrate in the failure wedge should be the same.

This suggests that the difficulty breaking out the anchor should be the same irrespective of the anchor size (ignoring the dead weight of the larger anchor and providing a smaller anchor does not exceed its ultimate holding power for the particular substrate ). However, larger anchor sizes are less likely to skip, jump and drag when setting, as well as efficiently penetrating difficulty substrates such as weed. In other words they more effectively translate the setting force generated by the boat directly into increasing the size of substrate failure wedge, creating a heavier failure wedge. This will be more difficult to break out. This is what is seen in practice.

This is especially true after stronger wind. As the smaller anchor starts to approach its ultimate holding power, the anchor will tend to become very inefficient at translating the force into diving deeper into the substrate, sometimes slowly dragging or at least moving a long way through the substrate while only digging in slightly deeper. Eventually it will have reached its ultimate holding power and maximum diving depth and it will break out (it is very easy to retrieve at this stage ) . The larger anchor will (hopefully) not have reached its higher ultimate holding ability and will still will be at the stage where a higher force is efficiently translated into diving deeper.

The substrate failure wedge is well illustrated in the photo below from the Vryhof anchor manual.

Interesting, thanks for that. I was thinking in terms of the volume of material directly over the flukes, the "B" in the diagram, as being the only factor when pulling straight up.