Anchor not holding- advice please?

[wakeup]

Which is why I am surprised OP is having a problem.

In the Bristol channel we have big tidal movements that will put the anchor under a lot of strain. When setting the anchor you have to be extra vigilant with scope and set. I either get rock and no holding or mud and excellent holding, you can hear the anchor and chain pinking along the ground when it is about to lose set. Scope is key of course and that is made more comfortable with a heavier gauge chain. I always tend to put out 4x rather than 3x and always scope and always do a pull test to ensure it is properly set. Not something you necessarily have to do elsewhere in the world. When the tide changes inevitably with such a strong tidal current then I need to reset the anchor. Only on neaps do I not have to do this.

I suspect that the OPs delta is fine, is it simply experience of setting and expectation that he will have to do this over and over in such a high tidal flow area.

 

[jfm]

My rig is a 20 kilo CQR on 10 mm chain for a 17 tonne boat. This year I've been playing with attaching 20m of loose chain to the lead of the shank on the anchor before I drop. The logic being that the chain holds the anchor on the bottom and counteracts the tendency of the cattinery to lift the anchor up. When I've done it the anchor hasn't moved and sets immediately. Haven't tried it in extreme conditions yet, so if someone else tries it please publish

You mean you attach one end of a 20m length of chain to your anchor shank? And the 20m length of chain just sits randomly on the seabed? I cannot see how that does anything useful. The anchor shank will only "feel" the weight of the first few links of chain and the other 19.9m is doing nothing at all. Sorry if I'm misunderstanding or missing something. 20m of 10mm chain weighs over 40 kilos; you'd be better just doubling the size of your anchor

 

[piratos]

My rig is a 20 kilo CQR on 10 mm chain for a 17 tonne boat. This year I've been playing with attaching 20m of loose chain to the lead of the shank on the anchor before I drop. The logic being that the chain holds the anchor on the bottom and counteracts the tendency of the cattinery to lift the anchor up. When I've done it the anchor hasn't moved and sets immediately. Haven't tried it in extreme conditions yet, so if someone else tries it please publish

QUOTE You mean you attach one end of a 20m length of chain to your anchor shank? And the 20m length of chain just sits randomly on the seabed? I cannot see how that does anything useful. The anchor shank will only "feel" the weight of the first few links of chain and the other 19.9m is doing nothing at all. Sorry if I'm misunderstanding or missing something. 20m of 10mm chain weighs over 40 kilos; you'd be better just doubling the size of your anchor [/QUOTE]

Well I understood it so that the anchorchain was extended with 10 mm chain right at the anchor and the standard chain was less than 10 mm ??
- anyway, I have a smaller boat weight ard 10-12 tons only, but although I have a 45 kilo CQR I am not satisfied with the anchor.
I am situated in the Baltic, and anchoring is normally in fairly sheltered areas with nor real tide, current in anchorages is very little, only the wind may disturbe something.Depths where we anchor is normally between 5 and 10 meters. Its just so that only the weight of the anchor and chain holds the boat. when I have been diving the anchor has always been capsized on the seabead with no digging in ! and with say 10-15 meters of chain lying on the seabead in from of the anchor. I have a spare anchor onboard with just 15 kg, and some 5 meters of chain. It has been nescessary to use this second anchor to hold the boat. Nobody carry several anchors to suit all kind of seabeds, but anchors are different, and in the end weight of anchor counts.

 

[MapisM]

Well I understood it so that the anchorchain was extended with 10 mm chain right at the anchor and the standard chain was less than 10 mm ??

Nah, how could the winch handle say an 8mm chain with the last 20m of 10mm chain?
Besides, Bertramdriver said "loose chain", which makes me understand the same as jfm. Whose doubts I fully agree with, fwiw.

Re. your 45kg anchor, that's a helluva hook for a 12T boat.
Based on what you are saying, I suspect that you are not reversing properly after releasing the anchor, to "force" it to dig in the seabed.
In any case, it's totally unrealistic that a 15kg anchor with 5m of chain can hold the boat wherever a 45kg CQR (with at least 8mm chain I suppose, if not 10) doesn't.

 

[Bertramdriver]

You mean you attach one end of a 20m length of chain to your anchor shank? And the 20m length of chain just sits randomly on the seabed? I cannot see how that does anything useful. The anchor shank will only "feel" the weight of the first few links of chain and the other 19.9m is doing nothing at all. Sorry if I'm misunderstanding or missing something. 20m of 10mm chain weighs over 40 kilos; you'd be better just doubling the size of your anchor

You're compltely ignoring the effect of drag from the loose chain if the anchor fails to set. Just try dragging 20 metres of 10 mm chain across the boatyard some time and then apply the knowledge you've gained to a sea bed.
Having heavier rig is fine if you're hale and hearty enough to haul it up if it snags or you have windless problems. For older and less athletic members more creative solutions are required. The additional chain just acts as a multiplier. Try it.

 

[piratos]

Nah, how could the winch handle say an 8mm chain with the last 20m of 10mm chain?
Besides, Bertramdriver said "loose chain", which makes me understand the same as jfm. Whose doubts I fully agree with, fwiw.

Re. your 45kg anchor, that's a helluva hook for a 12T boat.
Based on what you are saying, I suspect that you are not reversing properly after releasing the anchor, to "force" it to dig in the seabed.
In any case, it's totally unrealistic that a 15kg anchor with 5m of chain can hold the boat wherever a 45kg CQR (with at least 8mm chain I suppose, if not 10) doesn't.

hmm - you may be right : just read the figures on anchor saying 45 - could as well be lbs, which means 20 kilos. Sorry.
and yes - I am reversing till boats doesnt move backwards, which should be sufficient.... Point is however that if you dive to the anchor it lies capsized at the bottom and has NOT dig in. Thus boat is held only by weight of anchor and chain. The spare anchor I have (15 kg Seagrip by the way) has always dig into the seabed, and this even with only 5 m chain plus line for the rest.

As to Bertramdrivers chain extention or not - just saw the answer, so you are right (again)

 

[MapisM]

You're compltely ignoring the effect of drag from the loose chain if the anchor fails to set.

Yes, jfm analysis ignores that, but rightly so IMO.
When the anchor does NOT fail to set, which in my experience is true for the large majority of anchorages (the only exceptions being when I just don't care, for instance when dropping the hook in glorious weather, with no tide and wind, and just for a short stop), the loose chain effect is close to none.

 

[MapisM]

could as well be lbs

Well, that does make a difference!
The fact that you reverse till the boat stops, and still find the anchor laying capsized afterwards, that's rather weird though...

 

[Deleted User YDKXO]

You mean you attach one end of a 20m length of chain to your anchor shank? And the 20m length of chain just sits randomly on the seabed? I cannot see how that does anything useful. The anchor shank will only "feel" the weight of the first few links of chain and the other 19.9m is doing nothing at all. Sorry if I'm misunderstanding or missing something. 20m of 10mm chain weighs over 40 kilos; you'd be better just doubling the size of your anchor

I'm not sure what Bertramdriver means either but Yachting Monthly used to have a very effective demonstration at LIBS every year of the catenary effect of the anchor chain where they flaked out an anchor and chain in a long sand pit and measured the force required to pull it out out of the sand. Then they attached increasingly heavier weights to the anchor chain, tied back to the 'boat' end and allowed the weight to slide about halfway down the section of chain not sitting on the sand. Then they remeasured the force required to pull the anchor and that force increased relative to the size of weight suspended from the chain. I'm guessing that Bertramdriver is trying to achieve a similar effect but maybe I'm wrong

 

[Bertramdriver]

Yes, jfm analysis ignores that, but rightly so IMO.
When the anchor does NOT fail to set, which in my experience is true for the large majority of anchorages (the only exceptions being when I just don't care, for instance when dropping the hook in glorious weather, with no tide and wind, and just for a short stop), the loose chain effect is close to none.

Absolutely agree. In easy weather there's no need for extra measures so who wants the grief. But when your heart is racing and you need a quick solution to keep your boat under control then extra chain might help.

The idea arose after trying tandom anchoring with my 18 kilo fortress linked in tandom to the CQR. The problems I had lifting the fortress after securing the cqr in the roller convinced me I could never manage to do it under pressure. So I tried dropping just 10 mm chain without any anchor and found that in moderate conditions the chain slowed down the boats response to the wind surprisingly well. The rest was just playing around but I've not tried it above a 6/7.

 

[Deleted User YDKXO]

Yes, jfm analysis ignores that, but rightly so IMO.
When the anchor does NOT fail to set, which in my experience is true for the large majority of anchorages (the only exceptions being when I just don't care, for instance when dropping the hook in glorious weather, with no tide and wind, and just for a short stop), the loose chain effect is close to none.

I believe we've had this discussion before Mapism and I don't agree with you. The chain has a certain weight, it has resistance generated by friction with the seabed and it has a catenary effect to overcome so no, I don't accept that the chain has little or no effect in holding the boat

 

[MapisM]

Hang on folks (Betramdriver+Deleted User), the forces and the geometries involved with the "normal" anchor chain, and even more with tandem anchors along the same chain, are a completely different kettle of fish vs. any length of LOOSE chain attached ONLY to the anchor shank in parallel, so to speak, with the "normal" chain, but only attached on one end.
I fully agree that both tandem anchors and a heavy chain (the "normal" one, I mean) can be very effective.
But I'm skeptic that the loose bit of chain can do a lot, or anything at all, for the reason jfm already explained.

 

[Deleted User YDKXO]

Hang on folks (Betramdriver+Deleted User), the forces and the geometries involved with the "normal" anchor chain, and even more with tandem anchors along the same chain, are a completely different kettle of fish vs. any length of LOOSE chain attached ONLY to the anchor shank in parallel, so to speak, with the "normal" chain, but only attached on one end.
I fully agree that both tandem anchors and a heavy chain (the "normal" one, I mean) can be very effective.
But I'm skeptic that the loose bit of chain can do a lot, or anything at all, for the reason jfm already explained.

Agree entirely. I was not referring to Bertramdriver's suggestion about attaching a length of chain to the anchor shank. I don't see the point of that either. I was referring to the well known concept of suspending a weight (kellet) from the hanging section of the chain

 

[pondfish]

When I had a 21ft Antares 620 I used 7.5kg bruce with 32ft of 8mm chain then 12mm rope never failed in the Bristol channel out of Cardiff, I now have a 25ft Antares 760 with 12kg fortress and 48ft of 10mm chain then 14mm rope and that works great no problems, If I was the op I would go to a 10kg or even a 12kg anchor because I feel the one he is using is too light

 

[jfm]

Hang on folks (Betramdriver+Deleted User), the forces and the geometries involved with the "normal" anchor chain, and even more with tandem anchors along the same chain, are a completely different kettle of fish vs. any length of LOOSE chain attached ONLY to the anchor shank in parallel, so to speak, with the "normal" chain, but only attached on one end.
I fully agree that both tandem anchors and a heavy chain (the "normal" one, I mean) can be very effective.
But I'm skeptic that the loose bit of chain can do a lot, or anything at all, for the reason jfm already explained.

Tee hee. These threads are funny. I'm on the same page as you MM. Deleted User is engaging keyboard before reading carefully enough the posts he is replying to

 

[jfm]

You're compltely ignoring the effect of drag from the loose chain if the anchor fails to set.

I was indeed, because you yourself said "logic being that the chain holds the anchor on the bottom and counteracts the tendency of the cattinery [sic] to lift the anchor up.". Now you have switched tack and say the benefit is the drag/friction of the 20m of loose chain as the anchor slips and is pulled along the seabed, which is an entirely different phenomenon.

Just try dragging 20 metres of 10 mm chain across the boatyard some time and then apply the knowledge you've gained to a sea bed... Try it.

You try it. The drag of that 30kg of loose chain is tiny compared with the drag of a 30kg anchor and compared with the forces that have already made your main anchor start slipping

Having heavier rig is fine if you're hale and hearty enough to haul it up if it snags or you have windless problems. For older and less athletic members more creative solutions are required.

If the issue is windlass/human limitations, then this loose chain idea becomes even more questionable. Except in v shallow water, the weight of chain being hauled up by the windlass or human is greater than the weight of the anchor. When you spec an anchor winch, you mostly spec it for the weight of chain - you can almost ignore the anchor. That 20m of 10mm chain is 30kg; if you added just 10kg to the weight of your anchor you'd get better holding AND less effort for the winch/human - a win-win

 

[benjenbav]

You're all wrong. The answer's blimmin' obvious: it's the Mersey; some scouse scally came along and nicked the hook.

 

[benjenbav]

...Or else, as others have said, the thing was skipping along the seabed and the problem can be fixed by a bit of retardation whilst trying to set it; or a heavier hook, if you insist on a high speed approach.

 

[James L]

If you were moving at 7 or 8 knots, I think you're lucky the anchor didn't hold...
Imagine if it did bite and brought you to a sudden halt, I would think your winch and anything else tied to it would be sitting on the river bed.

Be careful if you change the anchor, you might get one that will bite at that speed.

It will be tricky to control, your speed into a flow like that and remain going backwards enough to make sure the chain doesn't pile up but I'm sure you'll get the hang of it.

Actually this is one case where the pile of extra chain or maybe a small grapple anchor in line might be enough to slow you down before the main anchor hits the bottom.

 

[mtb]

I had a few anchoring mishaps in the early days, and as I was using my anchor mostly for overnights on the hook, it was pretty important to get it right!

So I bought a book that helped in understanding the techniques and science behind anchoring. Since then, I've had no problems.

Have a look on Amazon for a book called "Staying Put: The Art of Anchoring".

how much did the book weigh ;-)