Shackle to anchor connection video

[rslifkin]

In my mind, good short scope behavior matters as it gives you options. If the anchor is a bit oversized and also has good short scope performance, you can tuck into a tighter spot a short scope in moderate weather, but still have the ability to add more scope in worse weather.

For what it's worth, the last time I short scoped my Vulcan for a daytime stop in a tight spot, I had 3:1 out in 15-20 kts of wind (fairly steady, minimal gusts). 19 feet of water, so 25 feet to the bow roller. I stopped at 50 feet to attach a snubber and while I was doing that let the boat blow back a bit. It set with 2:1 scope out, which I increased to 3:1 with the snubber. It held a 900 rpm back down (2 engines) just fine as well, which pulls the rode tighter than I've seen in 30 kts of wind.

 

[Nomad Willy]

Simi,
That was a snarky remark I shouldn't have said.

My Supreme was slow to set. But it never failed before my mods or after.

rslifkin,
Thanks for the informative report.
I had wondered if the short scope hole was passed on to the Vulcan.
Obviously not. Good to hear.
The Vulcan may have the strongest shank in the industry.

 

[rslifkin]

I don't know how strong the Vulcan shank actually is, but it certainly gives the impression of being beefy.

 

[Nomad Willy]

rslifkin,
It’s an I beam. Strong by shape.

 

[Greg S]

Greg,
I suspected but now I know. The shackle has lettering embossed on it’s sides. And I would imagine the shackle and bolt are rated separately but they need compatible threads and size. But it could be otherwise.

Yes, it's otherwise. Only use the shackle pin/bolt of the same manufacture as the shackle. They are rated together. Many different grades as well.

Greg S

 

[Nomad Willy]

While I’ve got you here Greg are they rated for dependability, strength or both?

As previously stated I’ve not bent a shackle (or even seen one) and I think many of my shackles are not rated. I see many new boats have Claw anchors. Do you think they have non-rated shackles? Does a Nordhavn have a rated shackle?

On TF many things are overdone. A car buff will scorn the tires on his new car and get high end tires right away. The same kind of guys lurk on boating forums. And w boats and cars either may receive a wide range of usage. Some boat anchors on new boats never even get used. And some may buy a popular anchor to be seen (assumably) to know “his way around”.

But does the average guy on TF need a rated anchor shackle?
My first rated shackle may have come w the XYZ anchor.

 

[O C Diver]

But does the average guy on TF need a rated anchor shackle?
My first rated shackle may have come w the XYZ anchor.

Eric, the simple answer is to look at the cost as part of the equation. I may not need a $30,000 suite of new electronics, but for most people a $19 shackle on a boat that uses 3/8" anchor chain seems a pretty trivial expense in the relative cost of owning that boat. The other question would be, "If the shackle of unknown quality fails, how bad physically or financially could the consequences be".

Ted

 

[Nomad Willy]

Ted,
Yes it always seems to gravitate to money, insurance, liability and lawyers.
But once a boat becomes used ..... and most will be used most of their lives.

Do you remember the thread 7 or so years ago about which way is best ... putting the shackle end through the slot or the shackle bolt through the hole .. or slot?
It was (as I remember) considered by more than not to put the shackle end through the slot as “best practice”. And in Steve G’s vid putting the bolt through shank was not even considered .. and/or mentioned.
Anchor manufacturers more or less need to offer the slot as there are many that consider the bolt hole to be “old school” and thus undesirable.
But as I recall there was a specific reason floated to indicate “best practice”. Obviously using the slot is only available when it’s offered. And anchor manufacturers may mostly offer the slot so buyers of either mindset will buy their product. So the existence of the slot is not evidence that it is a superior method of attachment.

CQR, Max, ForFjord and XYZ all offer only the bolt hole .. no slot. Obviously these manufacturers consider the bolt through the shank as preferable. They may also be assuming most will find the round hole or the slot to be both acceptable. There may be other modern anchors in this category.

But what I’m after is the reason why more felt the putting the end of the shackle through a slot was/is better practice. Side loading is a possibility .. I think someone mentioned that. And that could be all there is to it. What do you think?

 

[rslifkin]

Putting the bow end of the shackle through the anchor should gain some strength through reduced side loading. Depending on how the gear is sized, it may or may not matter. Putting the bow through the anchor and pin through the chain does offer another advantage, however. It allows use of a single shackle rather than 2.

 

[DDW]

First, you have to recognize that scope requirements change with depth. None of the anchors he tested would have reset if he were doing the test in 10' of water with 3.5:1 scope. There wouldn't have been enough chain weight to keep them on the bottom.

Secondly I would guess that doing those tests in 100' of water would have yielded very different results as the rode would have more resembled a steep curve instead of a straight line because of the weight of the chain.

The difference between the 10 pound Sarca and 100 pound Rocna is surface area of the fluke. When you get to a reasonable scope, there are other considerations that make one anchor hold better than another. The difference in size was to demonstrate that point in an obvious way. The 100 pound Rocna would do better at 7:1 because of its substantially larger fluke.

Ted

The answer to your scope hypothetical is, if I don't have enough chain or space for 7:1, then I want the one that will at least set at what I have regardless of brand or weight. If it doesn't set, then you can leave it at home with the same result. 7:1 scope is great on the Bahamas or Florida. In BC or Newfoundland you will find few places to anchor.

Regarding chain and angle of pull, Steve has done a video on that as well. All of his anchor tests, in addition to the reset tests, test maximum hold up to the ability of his engine, which he has quantified.

One should view his tests - and all anchor tests - as simply another data point, not THE definitive one which renders all others superfluous. I know Steve views his that way.

 

[Nomad Willy]

Not sure about the “bow end of the shackle”. That (if I got it right) would put the shackle at a 30 degree (or so) to the tension/pull and that would also tend to put the load on one side of the shackle. So perhaps 75% of the load would be on one side of the shackle. But if you put the shackle pin through the hole in the shank the load would much more likely be in-line w the shank and shackle arms.
And putting the shackle pin through the shank would always be w one shackle. Unless it was an unplanned hook-up of what you have in a box.

 

[Nomad Willy]

DDW,
I know what way Steve would support. He does it that way in his tests. Puts one of the eyes that receive the shackle pin/bolt through the slot.

Again my question is what way is the best shackle hook-up? I know the most popular way is as Steve does it ... the pin contacts the anchor chain and the inside center (roughly) of the shackle takes the load on the anchor shank. But theres nothing to align the shackle to that end. So the shackle ends up taking full load at about a 30 degree angle. Not as a shackle was designed ... IMO.

I content that the above is not the right way to use a shackle. The shackle should take the load through the holes for the pin/bolt. The bolt is designed to be in sheer load. And the shackle arms in tension .. in a straight line.

 

[trawlercap]

DDW,
I know what way Steve would support. He does it that way in his tests. Puts one of the eyes that receive the shackle pin/bolt through the slot.

Again my question is what way is the best shackle hook-up? I know the most popular way is as Steve does it ... the pin contacts the anchor chain and the inside center (roughly) of the shackle takes the load on the anchor shank. But theres nothing to align the shackle to that end. So the shackle ends up taking full load at about a 30 degree angle. Not as a shackle was designed ... IMO.

I content that the above is not the right way to use a shackle. The shackle should take the load through the holes for the pin/bolt. The bolt is designed to be in sheer load. And the shackle arms in tension .. in a straight line.

Shackles are great, until you have to downsize them to fit chain, the pins need to be wired and will bend in a side load. Ever have to cut a shackle off because the pin won't back out? It's rusted and probably bent. It has threads to secure the pin, not cool after a year or two.
Hammerlocks excell as chain connectors over anything available. More secure, no threads, stronger and really sexy. If anything was better we would have used it.

 

[O C Diver]

The answer to your scope hypothetical is, if I don't have enough chain or space for 7:1, then I want the one that will at least set at what I have regardless of brand or weight. If it doesn't set, then you can leave it at home with the same result. 7:1 scope is great on the Bahamas or Florida. In BC or Newfoundland you will find few places to anchor.

Regarding chain and angle of pull, Steve has done a video on that as well. All of his anchor tests, in addition to the reset tests, test maximum hold up to the ability of his engine, which he has quantified.

One should view his tests - and all anchor tests - as simply another data point, not THE definitive one which renders all others superfluous. I know Steve views his that way.

I'm not trying to convince you to use 7:1 scope. You can probably use a lot less based on your experience.

3.5:1 scope won't survive a current reversal or heavy weather in 10' of water. Based on my observations of boaters dragging anchor in shallow water with good holding bottom.

The scope requirement changes with depth.

What you need in scope at 120' is very different than 10'. Because of the curve of the rode based on depth and weight of the chain, the scope (3.5:1) that may work in 120' won't work in 10'. To say a test in 26' of water equals the results in 120' or 10' of water is scientifically flawed at best.

The one final thought I will offer is that powering the boat in a straight line without slack of the rode doesn't replicate an anchor reversal or or current switch. Most boats go beam to the seas, current, or wind and the anchor travels in jumps coming to a stop with the anchor and some chain resting on the bottom, not a continuous even pull with zero slack. When the hook grabs, the slack straightens and the bow swings toward the anchor, so full drag force isn't instantaneous.

While I have somewhat limited experience sand anchoring, I have anchored over 3,000 times. 30+ years as a scuba charter boat captain hooking shipwrecks with 1.25:1 scope. Whether you're hooking shipwrecks or sand, boats drift the same way dragging anchors. And yes I have watched anchors drag across the bottom while on scuba, to understand the dynamics of their movement.

I don't fault Steve for his method (He wasn't trying to sell anything), it generated the same flawed effects as the Fortress anchor tests (Imo, they engineered a test to make their product look good). A more realistic approach would have been to drift in a two knott tidal current.

Ted

 

[Simi 60]

Shackles are great, until you have to downsize them to fit chain,

Downsize them?

We run 13mm chain with a working load of 1.7 tonne

The shackles we use on our chain (Van Beest green pin) have a 16mm pin and have a working load of 2 tonne and a breaking load of 5x that.
Shackles are stronger than chain

Unfortunately, throat on that shackle isn't wide enough for anchor so we need to use a shackle 2 sizes up again

Ever have to cut a shackle off because the pin won't back out? It's rusted and probably bent.

Nope, they would have been replaced well before they got anything like that

 

[trawlercap]

Downsize them?

We run 13mm chain with a working load of 1.7 tonne

The shackles we use on our chain (Van Beest green pin) have a 16mm pin and have a working load of 2 tonne and a breaking load of 5x that.
Shackles are stronger than chain

Unfortunately, throat on that shackle isn't wide enough for anchor so we need to use a shackle 2 sizes up again



Nope, they would have been replaced well before they got anything like that

I've yet to see a shackle that fit an anchor also fit inside the attaching chain link. They are always a few sizes different. That is what I meant by downsizing to fit. You end up with two connections...and I've never seen it matter, just bugs me is all.

 

[trawlercap]

Plenty of options in the industrial/work world. I would sleep soundly with my anchor snapped to this....



Or shoot... give yourself a swivel. Lots of options, could snap on a second anchor after you get some chain out with the first one.

 

[MurrayM]

Plenty of options in the industrial/work world. I would sleep soundly with my anchor snapped to this....

View attachment 111866

In rock climbing, when a locking carabiner is called for but isn't available, two carabiners with gates opposed can be used.

There are situations where a single carabiners gate can be opened, such as by objects or the rope (anchor chain in this case) crossing and opening the gate.

Looks like this gate opens the opposite way, but it's something to think about.

 

[trawlercap]

In rock climbing, when a locking carabiner is called for but isn't available, two carabiners with gates opposed can be used.

There are situations where a single carabiners gate can be opened, such as by objects or the rope (anchor chain in this case) crossing and opening the gate.

Looks like this gate opens the opposite way, but it's something to think about.

Those are locking hooks, we use them to rig massive nets set to 600 fathoms. In wicked winter conditions. They don’t fail. I posted them for fun, I kinda don’t think they are too yacht like?

 

[MurrayM]

Those are locking hooks, we use them to rig massive nets set to 600 fathoms. In wicked winter conditions. They don’t fail. I posted them for fun, I kinda don’t think they are too yacht like��

Well, there you go. Since it's locking, my post is moot.

Haven't you noticed? This anchoring business is serious bad ass stuff

 

[trawlercap]

Well, there you go. Since it's locking, my post is moot.

Haven't you noticed? This anchoring business is serious bad ass stuff

Murray anchoring is as real as it gets yes. We’ve all seen anchor threads go the way of oil threads. Like you gotta find what you like and works for you. That’s cool, It’s one great thing about our boats, we pour ourselves into them, and get so much in return.

 

[MurrayM]

Murray anchoring is as real as it gets yes. We’ve all seen anchor threads go the way of oil threads. Like you gotta find what you like and works for you. That’s cool, It’s one great thing about our boats, we pour ourselves into them, and get so much in return.

It's also fraught with peoples interpretations of what's actually going on down there, which might be completely different than reality

 

[rslifkin]

I've yet to see a shackle that fit an anchor also fit inside the attaching chain link. They are always a few sizes different. That is what I meant by downsizing to fit. You end up with two connections...and I've never seen it matter, just bugs me is all.

According to Rocna's specs, the shackle slot on my 73lb Vulcan is designed to accept a 3/8 or 7/16 shackle with the bow through the anchor. I went with the 3/8, as it fit the 5/16 chain and already had a higher working load than the chain. So I figured the 3/8 shackle isn't the weak link, provided it's in good condition. At that point, going bigger won't gain me anything, so I might as well put the thought, effort, or money into something with more room for improvement.

 

[O C Diver]

According to Rocna's specs, the shackle slot on my 73lb Vulcan is designed to accept a 3/8 or 7/16 shackle with the bow through the anchor. I went with the 3/8, as it fit the 5/16 chain and already had a higher working load than the chain. So I figured the 3/8 shackle isn't the weak link, provided it's in good condition. At that point, going bigger won't gain me anything, so I might as well put the thought, effort, or money into something with more room for improvement.

Think your approach is very sound! Picking a load rated shackle that exceeds your chain's load rating pretty much covers the requirements. If I had a commercial vessel where shackles were in hard to inspect locations or inspections were months to years apart, it might make more sense to look at alternatives. In my own situation, I have to remove the safety retainer before deploying my anchor. At that time, it's easy to check the shackle and safety wire. Since the anchor is only deployed for at most a few days, it's very easy to stay current with the condition of the shackle.

Ted

 

[tozz]

Plenty of options in the industrial/work world. I would sleep soundly with my anchor snapped to this....

Which begs the question...how did we end up with shackles as the defacto "standard" in the pleasure boating world?

-tozz

 

[DDW]

To say a test in 26' of water equals the results in 120' or 10' of water is scientifically flawed at best.
....
The one final thought I will offer is that powering the boat in a straight line without slack of the rode doesn't replicate an anchor reversal or or current switch. Most boats go beam to the seas, current, or wind and the anchor travels in jumps coming to a stop with the anchor and some chain resting on the bottom, not a continuous even pull with zero slack. When the hook grabs, the slack straightens and the bow swings toward the anchor, so full drag force isn't instantaneous.
....
A more realistic approach would have been to drift in a two knott tidal current.

Ted

Two thoughts: I'd say the anchor doesn't know how deep the water is provided the angle of pull is the same. The angle of pull depends on the catenary which in turn depends on load, depth, weight of chain. With that point firmly in mind it is not scientifically flawed - it is as I said a data point and a valid one.

On resetting, one can hope that you are anchored in conditions where the boat swings slowly and in an orderly fashion, and chose an anchor which only does well in those circumstances. I sleep much better with an anchor that passes Steve's (extreme) test in case circumstances are less orderly than I had hoped. Would I trade that for less ultimate holding power? Perhaps, but I don't have to: many anchors demonstrate both excellent resetting and excellent holding power (even on short scope), as Steve's tests prove.

 

[psneeld]

I can't exactly explain why, but everything I have read agrees that higher scope ratios should be used in shallow water.

While correct that if the last few feet of chain are on the bottom the angle in any depth is zero...but the working issue is that maybe 5 knots of wind will pick up those last few feet if you only have 25 feet of chain out versus 150 feet of chain due to weight.

 

[rslifkin]

I'm almost positive that the shallow vs deep scope difference is related to the effect of waves. If you get hit with a 3 foot wave in 10 feet of water, that makes a significant difference to your angle of pull. In 50 feet of water, that 3 foot wave has very little effect.

The shock loads from that same 3 foot wave are a lot higher in shallow water as well. In 10 feet of water (so let's assume 15 feet from the roller) with 5:1 scope out (75 feet of rode), to rise up that 3 foot wave (so roller height momentarily increases to 18 feet from the bottom), the boat needs to move forward 8.1 inches (assuming no stretch in the rode). In the process, the angle of pull at the anchor goes from 11.5* to 13.9* as well.


If we move the boat into 40 feet of water (45 feet roller height), still at 5:1 scope, the numbers look very different. We now have 225 feet of rode out. Rising over that 3 foot wave now only requires the boat to move forward 7.6 inches. That doesn't seem like a big difference, but it's 6% less forward movement against the wind, with accordingly less force required. On top of that, the angle only changes from 11.5* to 12.3* in this situation.


For a more extreme comparison, with a roller height of 12 feet from the bottom and 4:1 scope (48 feet of rode), we see an angle change of 14.5* to 18.2*. And the boat has to move forward 10.5 inches to gain enough slack to ride over the wave. Change this to a roller height of 80 feet, still at 4:1 scope (320 feet of rode) and the angle change is only 14.5* vs 15*. And we only need to move forward 9.5 inches (9.5% less) to get over the wave.


To get the 80 foot roller height situation to look as bad as the 12 foot roller height in terms of peak rode angle at the top of the wave, we'd have to shorten the rode from 320 feet to 266 feet, or 3.3:1 scope. To match the forward motion to ride over the wave, we'd end up with 290 feet of rode out, or 3.6:1 scope. Even in the 3.6:1 scenario, we'd still be better off than in the shallow water at 4:1. Despite the loads from pulling the boat forward to rise over the wave being equal, the peak angle on the rode would still be lower (16.6*), so we'd still be in an easier anchoring scenario.

These calculations are all based on no stretch, so once you add in increased catenary from more chain weight in deep water and/or increased stretch from a longer length of rope rode deployed, the deep water scenario starts to look even better. I remember reading an analysis that determined that catenary was more effective in deep water vs shallow, although I don't remember the details of it or the reason why.

In general, it all comes down to this: anchoring in deep water is easier and can use less scope (but still more total rode length) than shallow water.

 

[psneeld]

Never heard it related to waves, but it is certainly also a factor.

Probably any and all forces affect the shorter rode more.

 

[Simi 60]

Its great not having to worry about scope
If we anchor in 10 ft of water under keel we let it run to the first red rope marker (150ft)
If we anchor in 20 we do the same.
And in 30 same again.
Simple

More depth I'd run it out to second marker of 250ft

I think some over think the numbers to much, more is better.
Chain doesn't work if sitting in a locker.