How should I anchor?

Fascadale

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Hypothetically,

At low tide a yacht anchors in 7 metres of water where the tidal range is 1 metre. The bottom is sandy. The yacht anchors in the middle of the anchorage with plenty of swinging room and no other vessels present. Shallow reefs extend to a distance from the shore that prevents the use of lines ashore.

The anchorage is sheltered all round by low lying land offering protection from the seas but not from the wind.

The wind is forecast to blow from between the NW and SW at around 40kts (F8) gusting higher. This is in a part of the world where the forecast can be unreliable, particularly regarding wind strength.

The heavy displacement long fin keeled 35ft yacht is equipped with a 16kg Manson Supreme on 50 metres of chain and 30 metres of multi plait, a 15kg Fisherman’s anchor on 10 m of chain and 40 m of multi plait, a 24lbs CQR on 10 m of chain and 40 m of multi plait and a 10 kg Bruce.

What would be the recommended anchoring strategy in this situation?

I’m thinking about Vathi, Ithaca earlier this year when a friend who was on a boat that survived the storm told me that other yachts were reported wind speeds of over 100kts

Thanks
 

cmedsailor

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My favourite way of anchoring is to drop the main anchor at the bow and run a line not ashore but on the bottom of the sea (chain around a rock and line to the boat). But this only when possible. I find it safe and I also don’t like the boat swinging around the anchor.
 

noelex

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The Manson Supreme is a great anchor and is reasonably sized for your hypothetical situation. With this anchor in 40 knots at a scope of a little less than 9:1 (at high tide after making an allowance for the bow roller height) on a mixed rode I would be reasonably happy providing the holding ground is reasonable and there is reasonable wave protection.

However, there is not a great deal of safety margin if the wind proves much stronger than forecast, the holding is poor or there is significant wave action.

The other available anchors do not have as high holding power, and deploying multiple anchors does not generally significantly increase the available holding power, as the force is not equally distributed. This typically causes each anchor to alternatively drag as they are subject to full load. Multiple anchors do help slightly in reducing the swing and this can sometimes justify their deployment despite the complications of tangling the two rodes and swinging differently if any other boats decide to share the anchorage at the last minute. The CQR is perhaps the best secondary alternative and given a potentially marginal situation this would be worth considering, but personally I would keep it simple.

The most wind I have experienced at anchor is 82 knots. At these extreme levels of wind security is far from guaranteed even if everything is in your favour such as a good holding ground, excellent oversized anchor, long scope etc etc. Over 100 knots is another level again and all you can do is swing the odds in your favour with the best equipment, techniques, and selection of anchorage location.

Finally, I understand your example is hypothetical but while Vathi on Ithica has an excellent substrate it has a reasonably fetch with a North westerly wind so there could be some wave action depending on the exact wind direction.
 

mainsail1

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The Manson supreme should be fine with 50m of 8mm chain and some of the rope to give shock absorption. Multiple anchors deployed leads to multiple problems and I would never do that. I would always have an anchor watch and my engine at standby to take some of the strain if necessary in strong winds.
Clearly winds of 100 knots would leave you in the lap of the Gods whatever you do.
 

Kelpie

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Some people swear by anchoring in line, I think the theory is that the force is more evenly distributed between all of the anchors.
 

Neeves

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I would suggest you extend your inventory with a nylon snubber, or 2.

Your main rode is chain and multiplait. If the multi plait is matched to the chain it will lack elasticity, as to offer the same strength as the chain it will be beefy and beefy rope is not very elastic. As you will be deploying both chain and the multi plait you need to devise a way of attaching the snubber to the multi plait, rolling hitch or prussic knot come to mind.

The snubber needs to be elastic and I'd suggest you go to your nearest climbing gym and ask if you can recycle some of their 12mm retired dynamic ropes. They are not allowed to sell them, they must ensure they are not used for height safety - most go to land fill. Offer to replenish their tea or Xmas fund. You need a snubber something like 3 times deck length to be effective. Start the snubber at the transom, run up the side deck, find a way to get from the side deck to the rode so that you minimise abrasion, 'barber hauls' on the foredeck work well. If you start at the transom you can route the 'tail' through a turning block to a sheet winch and then shorten or lengthen from the comfort of the cockpit. Ideally you want to devise a bridle, 2 snubbers up each side deck, see pdf offer below.. If you want to buy new climbing rope it comes at a price of about US$3/m. It is impossible to knot, sewing loops is common place or as halyard knot. We now buy new and I have loops sewn (and tested). If you are looking at re-cycling try to find a gym with high walls, say 15m (often in warehouses on industrial estates) you then have the chance of long, 3 x deck length, ropes (12mm kermantle dynamic rope). Some gyms are quite low and you can only source short ropes - so ask around. If you are uncomfortable about recycling - just remember a snubber is not your back stop - the rode is the back stop.

Also - always use some form of chain hook. Snubbers, or bridles fail. You do not want your snubber failing the tension immediately transferred to the windlass. We use a chain hook from the lifting industry and a dyneema strop attached to a strong point.

If you are confident with the forecast of SW to NW I would also deploy 2 anchors (every time).

I can see no earthly reason why a wind varying between NW to SW will cause the 2 rodes to tangle. If the wind is to vary between NW and SE - that's a different story - but not one you suggest. So stick to reality and use reality to offer the best solution.

2 anchors is not to give double the hold - but to reduce veering and to give each anchor opportunity to offer its maximum hold. You Supreme will offer the potential of 2,000kg - that's the hold I've measured in decent sand. You will never, ever develop that tension you rode - but it may still drag - because it is loaded from the side and because the sheer strength of the seabed has been reduced.

Your hypothetical anchorage will enjoy wind sheer as the wind passes over low land and will gust between trees and valleys to windward. Your yacht will then yaw and the anchor will be constant loaded in different directions as it turns to meet the wind. The anchor will thus be constantly moving tugged this way and then another. Its potential hold is now academic as it is dug into a constantly moving bit of seabed. If you deploy 2 anchors and they are roughly aligned to the variations of the wind direction then each will be orientated such that the tension on the rode will be more constant and the anchors less likely to move. If the anchorage is subject to chop then you need to deploy as much rode as possible to keep the chain portion on the seabed. That chain is a perfect conductor of movement, every move the yacht makes is transmitted down the rode and, again, the seabed will lose shear strength.

To give an example - wet concrete and a trowel. Wet concrete looks quite dry if left to stand, put a trowel in the concrete and wiggle it about and the concrete liquifies - same as your anchor twitching, stop the twitching (by steadying the yacht) higher seabed sheer strength, more hold.

There are other practical things you can employ - get the dinghy off the bow (it will increase veering). Remove you Bimini etc, they increase windage. lower the boom as low as possible, remove the furled headsail. Have goggles handy - if you have high wind and rain you will not be able to open your eyes.

If you are worrying about 100 knot winds then I'd check your anchor shackles, make sure you have no 316 stainless in the rode and that your shackles are Crosby G209a (it has a WLL for a 3/8th" shackle of 2t) - anything less might deform. I'd check your chain hook (if you use one).

Also remember that if the seabed is cloying and a concave anchor drags that it will not reset until suites as the fluke has cleared (be dragging itself across the seabed)

Anchor Resetting Tests - Practical Sailor

I would suggest reconsidering your quiver of anchors. We carry a Spade, Excel and 2 x Fortress. I note you don't mention a Fortress but in the environment you describe, wind in a fairly constant direction, sand seabed then it is ideal. It is also light and easy to deploy from a dinghy (as soon as you hear the forecast). Jimmy Green may stock Excels in the future but in the meantime wait for reports on the Epsilon - it looks good on paper. But wait till other report back - I see no need to be a guinea pig (though someone might need to be :( ). I would not suggest buying either of the Mantus anchors nor the Vulcan, the M1 is all hype, the M2 and Vulcan don't seem to have made any waves.

Here is some further background reading for you

How to: Dealing with Snatch Loads in an Anchorage

Anchor Snubber Tips

Know how: Expanding your Anchoring Repertoire

Know how: Ground Tackle

The art of snubbing, in the nicest possible way - MySailing.com.au

There is an unfortunate amount of repetition in the articles.

If you, or anyone else, would like my latest developments in rigging a bridle, send me a PM with your email address and I will send you a pdf. The articles are published but are behind a paywall - so no point in sending you a link.

If you have queries, post them here, there is plenty of knowledge and lots of experience here - knowledge is better shared


And

Best wishes for New Year, let us hope 2021 starts to return us to some semblance of the lives we used to live.

Jonathan
 

JumbleDuck

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The heavy displacement long fin keeled 35ft yacht is equipped with a 16kg Manson Supreme on 50 metres of chain and 30 metres of multi plait, a 15kg Fisherman’s anchor on 10 m of chain and 40 m of multi plait, a 24lbs CQR on 10 m of chain and 40 m of multi plait and a 10 kg Bruce.

What would be the recommended anchoring strategy in this situation?
I'd use the Manson plus all the chain.
 

JumbleDuck

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I would suggest you extend your inventory with a nylon snubber, or 2.
I think that depends entirely on whether the skipper knows of any issues with snatching. Since it's an older design it seems likely that there are none, in which case bouncing around like a demented yo-yo has no major benefits, save giving the boat more of a run at pulling out the anchor in gusts.

If the boat is one which snatches then by all means snub.
 

Seven Spades

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In wind over tide situations my boat sometimes sails up the chain and the snubber drops off when it goes slack. What is the best way to deal with this issue?
 

Neeves

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In wind over tide situations my boat sometimes sails up the chain and the snubber drops off when it goes slack. What is the best way to deal with this issue?

If you use a chain hook with a clevis pin then its easy to use the clevis as a hinge and simply hang a gate from the pin so that it sits snug within the jaw of the hook. I've made a few such gates and I notch the end of the gate, that is in the jaw, so there is an active mechanism to stop the lock rotating but it can be released one handed, the hand holding the hook and simply flip the gate with your thumb. I have not found an easy way to lock a claw. I make my own bridles plates )and have a design that is being copied) and I make sure the slot is sufficiently long that the chain does not slip out.

If you use my methodology of starting the snubber at the transom you have a deck length of active snubber down your side deck, say 10m. You can then have say 2m forward of the bow (so you are now using 12m) but the 2m forward of the bow is too short to reach the seabed - so the hook never drags and the weight of the chain always keeps the hook the right way up. If you want your snubber to be longer and the wind picks up - deploy more snubber and the tension in the rode, from the wind, keeps the hook off the seabed. If the wind drops, winch the snubber in a bit.

An advantage of my system is - if you want to deploy a storm snubber, for that 100 knot wind :( , you can winch the snubber in, add your storm snubber, take the 'normal' snubber off if you want, or deploy both. If you attach your snubber at the bow and extend outboard its difficult to retrieve to allow you to attach a storm snubber and having 10m forward of the bow means that it is inevitable that sometimes the chain hook will be on the seabed.

If anyone has noticed a severe yo yo effect from using a snubber - I'd be delighted to hear - having used long snubbers for years now - its one of those facts (that is not in fact a fact) but become more true by its constant repetition. Yes you move back and forth - as you do as catenary 'operates'. The advantage of a snubber is - it will work until it fails, absorbing the energy of gusts, catenary slowly loses that ability to absorb energy as it straightens (unless of course you carry 200m of 12mm chain in a 36' yacht).

Jonathan
 

Neeves

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Some people swear by anchoring in line, I think the theory is that the force is more evenly distributed between all of the anchors.

If Thinwater comes along he may comment.

He tried in line tandem anchoring.

First off its difficult to set 2 anchors in line connected together. Secondly if the furthest anchor holds then as the rode tightens, or straightens it results in a vertical component on the inner anchor (the one nearer the yacht) and simply lifts it out. You then have one anchor holding the yacht and the other simply acting as a kellet. Finally its difficult to retrieve two anchors joined together in line.

If you know the wind is going to be 'fairly' constant you could deploy and set two anchors on 2 independent rodes roughly next to each other. If the rodes are very similar, so same chain size, same length then they will perform similarly and you will have twice the hold of one anchor (assuming the 2 anchors are the same design). However though using a high holding anchor offers advantages (they also seem to resist veering better - though quantifying this advantage has so far defeated - everyone) it is not an absence of hold that is the issue.

There is some other mechanism that allows anchors to drag - in the absence of another idea I'm putting my money on the the movement of the yacht causing twitching at the anchor and this resulting in a lowering of shear strength of the seabed and thus lowering actual hold. So my focus is on keeping the yachts movement to a minimum and introducing elasticity to the rode (which absorbs energy, snatch loads and introduces a part of the rode that does not transmit so well the yachts movement to the anchor and seabed).

An idea to bear in mind - Morgans Cloud removed their recommendations for concave anchors ( or those like Rocna and Supreme), but continue to use a Spade as their primary. The implication is that despite the high hold of a Rocna (twice that of a Delta).........

they still dragged.


An experiment, like my cement and trowel experiment above. Take a bit of anchor chain and string it between 2 trees, does not matter if its tight or droopy, but not touching the ground. Have your finger touching one end (and stretch your imagination and pretend your finger is an anchor). Now (you have proven you have a good imagination so now assume that a hammer or mallet is like a yacht!) have someone hit the other end with a hammer, even a rubber mallet. You will feel the impact - no matter how long the chain. Now attach one end with your nylon snubber and repeat hitting the snubber with the same hammer/mallet. The impact is dampened. Same as your anchor. Chain is a, almost, perfect transmitter of movement - so every sea saw of your yacht every gentle straightening of your chain is immediately transferred to your anchor (unless you use a decent snubber).

Using elasticity and catenary to minimise movement and snatch loads is not very clever. Your car uses a variety of mechanisms to smooth out bumps, shock absorbers, springs, tyres, foam in the upholstery - the idea that catenary can do everything does seem a bit simplistic - especially as we have other mechanisms available to us. A snubber does not work by itself, catenary is still there.

Jonathan
 

duncan99210

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The first thing I’d have done is leaving Vathi for somewhere else if it was at all possible! It’s a notorious wind hole when there’s north in the wind as it channels through the hills leading into the harbour.
However, if you’re there then the holding is good and the wind is usually directionally stable, so you don’t have to worry about it changing direction. I’ve not seen a 1 metre tidal range there, it’s usually much less than half that but there’s no current as theres no flow through the basin.
As to the anchoring, I‘d have all the chain and part of the rope out. I’d also have the CQR on deck with the rode from both it and the fisherman ready to deploy if needed. One of the problems of Vathi is that if you do have the anchor dragging, there’s not much space to give you the time to sort things out, hence having a second anchor ready to launch if needed. I’d also have the engine running at tickover in case it was needed, not that you'd be able to motor into the predicted wind but it could help to buy time.
 

Stemar

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I’d also have the engine running at tickover in case it was needed, not that you'd be able to motor into the predicted wind but it could help to buy time.
If the wind does get up to stupid speeds, would there be any advantage to using the engine to drive the boat towards the anchor? - not enough to move forward, even if you can, just to reduce swinging and relieve the strain in gusts. After all, it's not as if anyone's going to be sleeping.

I'd also have my passage plan out at the ready, even if it is only "Our Father which art in heaven..."
 

JumbleDuck

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Using elasticity and catenary to minimise movement and snatch loads is not very clever. Your car uses a variety of mechanisms to smooth out bumps, shock absorbers, springs, tyres, foam in the upholstery - the idea that catenary can do everything does seem a bit simplistic - especially as we have other mechanisms available to us. A snubber does not work by itself, catenary is still there.
Given that some boats and situations clearly benefit from snubbers ...

You need to include the dynamic and damping effects of the boat as well. It acts both as a spring (when the bow is pulled down it tries to rise and vice versa) and as a shock absorber (all that displaced water sloshing around)

Chain is a, almost, perfect transmitter of movement - so every sea saw of your yacht every gentle straightening of your chain is immediately transferred to your anchor (unless you use a decent snubber).

How different do you think the forces are at the two ends of a snubber?
 

mainsail1

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If the wind does get up to stupid speeds, would there be any advantage to using the engine to drive the boat towards the anchor? - not enough to move forward, even if you can, just to reduce swinging and relieve the strain in gusts. After all, it's not as if anyone's going to be sleeping.

I'd also have my passage plan out at the ready, even if it is only "Our Father which art in heaven..."

Yes, I have done just that in wind speeds gusting 55/60 knots. Most of the time I just left the engine at very slow ahead to take some of the strain off the anchor but if I saw the boat moving ahead I went to neutral and if it dropped back too far I increased revs.
In wind speeds above that I think the Lords Prayer is the only thing left.
The point someone made about removing windage items before the storm arrives is a good one.
 

Fascadale

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Thank you for the thoughtful and comprehensive replies

The boat is equipped with snubbers, I should have mentioned that in the OP. However they are shorted than those suggested by Mr Neeves............room for improvement there.

A secondary, backup, method of securing the chain.................... room for improvement there.

I like the wet cement analogy.

The "quiver of anchors".................the CQR, the Bruce and the Fisherman are legacy anchors. Indeed the CQR is the only anchor that will fit into its bespoke anchor locker. The fisherman has the advantage of folding flat and I regard the Bruce almost as an angel although for many years it served well as the primary anchor on Scotlands west coast. If I were to replace one it would be the Fisherman with a Mantus ( Unfortunately Scotland's greatest maker of anchors does not currently produce a "fold up" model")

In the Vathi storm the yacht in question dragged into deeper water, twice, so I suspect the wind was funneling out of the SE

However, given the equipment in the original post' "a 16kg Manson Supreme on 50 metres of chain and 30 metres of multi plait, a 15kg Fisherman’s anchor on 10 m of chain and 40 m of multi plait, a 24lbs CQR on 10 m of chain and 40 m of multi plait and a 10 kg Bruce." how would it best be deployed?

Two rodes at 45°to each other, one rode with the Manson and all the chain, the second rode with the CQR and Fisherman in tandem, on chain 10 metres apart then the chain and rope rode? Or one rode with up to three anchors in series and perhaps using the Bruce as an angel?

I think I would also be thinking about attempting to dampen the veering : a riding sail perhaps.

Here is an interesting YouTube illustrating a tandem anchor strategy for hurricane survival

And here is another yacht surviving a hurricane with one anchor, allbeit at 105lbs Mantus on a double rode

Lots to think about.
 
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