Dragging of anchors

[sailaboutvic]

How long does it take to set an anchor .

The noise you can hear is the boat starting to vibrating and shake as the power is increased and the boat is unable to move, it took all of a few minutes from start to finish , no tea involved .



Sorry quality not that good .


https://youtu.be/nlIEQ-zOuMM

 

[GHA]

Oh dear! Anchoring used to be so much simpler before we had to worry about all these formulae.

Still simple, no need to worry about any equations

The universe behaves the same as it ever did, there's just a little maths here and there which describes roughly how it behaves.

 

[Robin]

Perhaps it's modern lighter boats surging around faster and imposing bigger shock loadings on anchors which has driven the adoption of both modern anchors and snubbers?

Isn't 3x scope still plenty, with chain?

We estimate depth at high water, plus the bow height and initially let out 3 x that of chain to do the initial set, even if we arrive at Low water. Then when dug in will let out more chain if we think it advisable for the anticipated conditions during our stay, then we fit the snubber line and let out a little more chain so that the load is transferred from the windlass to the snubber line. Those using a mostly warp rode will undoubtedly use a greater multiple of depth and wander around more, possibly imposing more frequent snatch loads in the process? I feel that if the anchor will not initially set using 3 x depth scope that something is not quite right and needs sorting then and there not left until later, like trying a different spot clear of weed or with a more favourable bottom type maybe. Rarely did/does a 3 xHW scope as described above not result in a set. I see no merit in optimistically letting a load more chain out willy nilly to achieve an initial set when clearly something isn't going right..
,

 

[NormanS]

"Three times the depth" is a slightly misleading statement. Assuming that we are talking about overnight anchoring, and assuming an all chain rode, it would normally be inadequate in shallow water. Conversely, in deep water, less than three times is more than adequate. However, given plenty of space, and impending bad weather, even ten times the depth wouldn't seem excessive. In other words, it all depends.

 

[30boat]

"Three times the depth" is a slightly misleading statement. Assuming that we are talking about overnight anchoring, and assuming an all chain rode, it would normally be inadequate in shallow water. Conversely, in deep water, less than three times is more than adequate. However, given plenty of space, and impending bad weather, even ten times the depth wouldn't seem excessive. In other words, it all depends.

In theory the more the better if you have the swinging room.

 

[sailaboutvic]

What is suggested by someone we have never had met or something we have read, and what we do knowing that it works are two very different things.
We never drop less than 4:1 but more than likely it's 5:1
If we in for. Blow and we have the room it more than likely to be 7 or 8:1 more if need be.

 

[Robin]

I have been using snubbers for more than 20 years. Certainly not new to me

Nor me and in true BLue Peter/PBO fashion I and several friends back in my small boat days msade up snubbers from multiple lengths of bungy cord whipped together as one 'sausage' with hooks each end, simply inserted into a slack bight of the then 1/4 inch chain, crude but cheap and effective on +/-20ft boats. I didn't get into the nylon plus dogbone specials until we had boats with a windlass, initially a manual, later electric ones. Still adds up to more than 27 years ago.

 

[JumbleDuck]

"Three times the depth" is a slightly misleading statement. Assuming that we are talking about overnight anchoring, and assuming an all chain rode, it would normally be inadequate in shallow water.

Golly. Even with a modern anchor?

Incidentally, I find that my boat sheers about far more if there is a lot of chain out - comes of having less restoring force when the bow displaces sideways.

 

[Neeves]

We estimate depth at high water, plus the bow height and initially let out 3 x that of chain to do the initial set, even if we arrive at Low water. Then when dug in will let out more chain if we think it advisable for the anticipated conditions during our stay, then we fit the snubber line and let out a little more chain so that the load is transferred from the windlass to the snubber line. Those using a mostly warp rode will undoubtedly use a greater multiple of depth and wander around more, possibly imposing more frequent snatch loads in the process? I feel that if the anchor will not initially set using 3 x depth scope that something is not quite right and needs sorting then and there not left until later, like trying a different spot clear of weed or with a more favourable bottom type maybe. Rarely did/does a 3 xHW scope as described above not result in a set. I see no merit in optimistically letting a load more chain out willy nilly to achieve an initial set when clearly something isn't going right..
,[/QUOTe

+1

If the anchor does not set at 3:1, and modern anchors set at short scopes, then there is something seriously wrong, something in the fluke, wrong seabed. We would move and try again. Only once the anchor sets would we deploy more, min of 5:1 (depends, as mentioned by others). One reason for the 3:1 initial set (other than it should work) if it does not set there is less to take in before the next attempt and taking in more than 25m means the chain towers in the locker and jambs the windlass - so part driven by laziness.

Jonathan

 

[Robin]

We estimate depth at high water, plus the bow height and initially let out 3 x that of chain to do the initial set, even if we arrive at Low water. Then when dug in will let out more chain if we think it advisable for the anticipated conditions during our stay, then we fit the snubber line and let out a little more chain so that the load is transferred from the windlass to the snubber line. Those using a mostly warp rode will undoubtedly use a greater multiple of depth and wander around more, possibly imposing more frequent snatch loads in the process? I feel that if the anchor will not initially set using 3 x depth scope that something is not quite right and needs sorting then and there not left until later, like trying a different spot clear of weed or with a more favourable bottom type maybe. Rarely did/does a 3 xHW scope as described above not result in a set. I see no merit in optimistically letting a load more chain out willy nilly to achieve an initial set when clearly something isn't going right..
,[/QUOTe

+1

If the anchor does not set at 3:1, and modern anchors set at short scopes, then there is something seriously wrong, something in the fluke, wrong seabed. We would move and try again. Only once the anchor sets would we deploy more, min of 5:1 (depends, as mentioned by others). One reason for the 3:1 initial set (other than it should work) if it does not set there is less to take in before the next attempt and taking in more than 25m means the chain towers in the locker and jambs the windlass - so part driven by laziness.

Jonathan

We think so much alike it is spooky..
Our current chain (bow)locker has access from on deck but the windlass itself is on the deck and the chain drops through a hawse pipe into it. It does volcano pile but I bought a telescopic fishing gaff so I can easily hook it from a comfortable standing position and pull some away periodically towards the emptier forward part of the locker, thus clearing space for more to arrive down from the windlass. I have seen vaious gizmos and ideas to divert incoming chain from volcanoing and tried a few home made ideas that failed too. Hand manipulation seems most effective and at least in our case it does not involve climbing in through a small access hole in the forward cabin bulhead!

Probably because we use the 3x(HWdepth plus bow height) formula yet in practice rarely arrive at HW max depth, we are setting ours at nearer 4:1 initially before finally settling on something in excess of that especially if much wind is expected later. Since moving to the skinny waters hereabouts we are highly unlikely to run short of chain (we have 150ft in one continuous length) but can easily add an extra 150ft of nylon ( made up ready) if needs be the option of less scope in deep waters is not needed. Oh and the high snatch loads in shallow waters in a swell is something when I was a mooring meister I was well aware of as some other clubs in my then area had experienced riser chain breakages as a result. With a deep draught boat anchoring in true shallows was never a likely scenario anyway. Our draught now is just over 5ft so I will look for nearer 10ft min at LW to anchor in if I can, skinny enough but not anorexic..

. .

 

[Neeves]

We have no simple solution to the chain towering - except what you do, attack it manually. By hand, no big stick. I lie on the deck and push the chain about.

I retrieve and I know when (roughly), in terms of length of rode retrieved, the tower is going to jamb the hawser pipe. I simply stop the windlass, foot pedals on the bow, prior to the point of jambing and knock the tower over and then push the whole mass of chain sideways to give an empty space for the next lot of chain. Our chain locker is quite big, but not deep, and as we only use 8mm chain a pile of 20m is not that heavy and can be pushed about. The base of the locker is completely flat. I push the first 20m into one corner and then fill successive corners.

Our windlass is mounted below deck, which gives a clear deck but does inpinge on the fall of the chain. It is a vertical windlass, which further reduces the height of any tower. The windlass foot pedals and the windlass are only about 500mm apart, so its not a difficult operation.

Another of the many compromises.

 

[charles_reed]

Scope - is dependent upon the anchor - an experienced yottie I know swears by (not at) the Brittany (FOB), but always with 6:1.

I find both CQR and Delta need 4 to 5:1 and a a boat length to set.

The advantage of new-age anchors is the fact that they don't seem to need more than 3:1 scope and set it metres rather than boat-lengths, in soft sand.

I'm referring here to depths of 6-10m, at which most people seem to anchor.

One disadvantage of the large fluke area of new anchors is that in a lively sea, they are easily carried away even if tied down in the roller. It was blowing 35 knots with Med seas to match when I came round Sounion on Thursday morning, the lashing on the front of the Mantus was carried away as the anchor acted as a hydrovane. It's probably better to stow them or hang them vertically.

 

[Neeves]

Anchor lockers tend to be minimalist in modern yachts and difficult to house even an anchor of the recommended size. With the current fashion to upsize the anchor, strongly advocated by many - it would be impossible to stow an oversized modern anchor in the locker. Lashing them even more securely will be an answer but it will not alter the fact that their flukes are hardly an asset when sailing to windward in seas - as you aptly point out.

Charles - all credit to you, the issue has been raised in the past but yours is the first user comment on the topic I have seen.

Jonathan

 

[JumbleDuck]

Anchor lockers tend to be minimalist in modern yachts and difficult to house even an anchor of the recommended size.

I wonder if one of the reasons for satisfaction with modern anchors is that new boats frequently come with grossly undersized ones - of whatever design - and so moving to the right size of anything would be an improvement.

 

[Neeves]

I do not know if new yachts carry , or are sold with, undersized anchors but it is certainly true, or has been in the past, that many who 'upgrade' (and I know you will not like the word but I'm not needling anyone) do so with a modern anchor of a size(s) bigger than the pre-modern they had previously. Their ecstasy then has to be tempered, by anyone reading their glowing testimonials, with the idea that maybe if they had just bought a bigger model of their existing design at the local jumble they might have also been pleased (and saved a wallet full of money). The other problem and worse is that many extol the virtues of their choice but omit to mention the modern anchor is much bigger. Some carry 'bigness' to the extreme.

Few of us downsized when we went modern - but I can assure you it was a positive move for us.

I have noted that some new yachts have removable bow roller, they swing over with the anchor into an anchor locker). Its a neat idea as the bow roller no longer protrudes (and neither does the anchor). But there is, must be, a finite size of anchor and maybe restricted design, this assembly will take. The yachts I have seen with this feature invariably have a Delta. I have this nasty idea at the back of my mind that a yacht builder who fits out his yacht with pre-modern anchors lacks some credibility - but I'm just a cynic.

Jonathan

 

[sailaboutvic]

Scope - is dependent upon the anchor - an experienced yottie I know swears by (not at) the Brittany (FOB), but always with 6:1.

I find both CQR and Delta need 4 to 5:1 and a a boat length to set.

The advantage of new-age anchors is the fact that they don't seem to need more than 3:1 scope and set it metres rather than boat-lengths, in soft sand.

I'm referring here to depths of 6-10m, at which most people seem to anchor.

One disadvantage of the large fluke area of new anchors is that in a lively sea, they are easily carried away even if tied down in the roller. It was blowing 35 knots with Med seas to match when I came round Sounion on Thursday morning, the lashing on the front of the Mantus was carried away as the anchor acted as a hydrovane. It's probably better to stow them or hang them vertically.

We must had just missed each other coming around Sounion Thursday , we only sew one other yacht , crazy weather . Sailing by the seat of our pants .

 

[Robin]

I do not know if new yachts carry , or are sold with, undersized anchors but it is certainly true, or has been in the past, that many who 'upgrade' (and I know you will not like the word but I'm not needling anyone) do so with a modern anchor of a size(s) bigger than the pre-modern they had previously. Their ecstasy then has to be tempered, by anyone reading their glowing testimonials, with the idea that maybe if they had just bought a bigger model of their existing design at the local jumble they might have also been pleased (and saved a wallet full of money). The other problem and worse is that many extol the virtues of their choice but omit to mention the modern anchor is much bigger. Some carry 'bigness' to the extreme.

Few of us downsized when we went modern - but I can assure you it was a positive move for us.

I have noted that some new yachts have removable bow roller, they swing over with the anchor into an anchor locker). Its a neat idea as the bow roller no longer protrudes (and neither does the anchor). But there is, must be, a finite size of anchor and maybe restricted design, this assembly will take. The yachts I have seen with this feature invariably have a Delta. I have this nasty idea at the back of my mind that a yacht builder who fits out his yacht with pre-modern anchors lacks some credibility - but I'm just a cynic.

Jonathan

I was not happy with the 33lb claw we inherited with our boat but just my thought not from actual poor experiences. I thought hard about a new type but aside from the practical problem of them fitting on our single bow roller, for the same cost by buying a Delta I could increase the anchor size by two over the norm recommended for our boat size. That and having many satisfactory years (with a one size undersized Delta on a previous boat influence my decision to upgrade from the inherited 33lb claw on a 36 footer to a new 45lb Delta. I could have gone up another size for the money but chose not to as we were also switching to all 3/8 chain rode, from 30ft of same plus warp to 150ft of all chain, so weight in the bow was part of the overall consideration also. From a race trim viewpoint It may be imperfect, but it also compensated in part for the RIB in davits that we added at the back end at the same time thus doubly against the race trim pundits advices!

All things boating are compromises at least at my paygrade! :ambivalence:

 

[noelex]

I have noted that some new yachts have removable bow roller, they swing over with the anchor into an anchor locker). Its a neat idea as the bow roller no longer protrudes (and neither does the anchor). But there is, must be, a finite size of anchor and maybe restricted design, this assembly will take. The yachts I have seen with this feature invariably have a Delta. I have this nasty idea at the back of my mind that a yacht builder who fits out his yacht with pre-modern anchors lacks some credibility - but I'm just a cynic.

The last cruising boat I saw with this feature had an hydraulically controlled carbon fibre bow roller that magically folded out. I watched it open out wondering what exotic anchor could be on the end of such a mechanism.

It was a CQR .

The retractable bow rollers look fragile to my eyes and I suspect it places a lot of restrictions on the choice of anchor design and size. Personally, I hope it is not a trend that grows in popularity on cruising yachts.

At the absolute opposite end of the scale is something like Steve Dashew's FPB.

Now that's a bow roller for a serious cruising boat.

It has been designed by someone who has anchored in tough conditions and has seen what works. Maybe a bit of overkill, but I like it. That is a 240 lb (110 kg) Rocna on a 64 foot boat.

 

[Sybarite]

That is complete nonsense. The whole idea of the hinge is so that the tip hinges down into the seabed. If the anchor is lying on its side, which is how it will almost certainly land, it just means that it hasn't had any pull on it yet.

This was verified by underwater video in the tests I referred to above. If the whole thing is rigid there is a better chance that it will be pulled onto the point. The fact that it is on a hinge on the CQR means that irrespective of what way the shank is pulled the plough head can remain stable on its side.

These video tests look pretty conclusive, at least to my satisfaction:

SPADE
https://www.youtube.com/watch?v=apY89Qz9yDA
https://www.youtube.com/watch?v=xjuif0HCVi4

CQR
https://www.youtube.com/watch?v=d_2MJsNruAA

Rocna V. CQR
https://www.youtube.com/watch?v=kyd-trE0Xqw

 

[vyv_cox]

This was verified by underwater video in the tests I referred to above. If the whole thing is rigid there is a better chance that it will be pulled onto the point. The fact that it is on a hinge on the CQR means that irrespective of what way the shank is pulled the plough head can remain stable on its side.

The primary design feature of NG anchors is that the emphasis is on maximising tip loading. Spade achieves 50%, Rocna about 35%, whereas CQR is only 14%. The knuckle of the CQR is a greater proportion of its overall weight than the tip, hence its tendency not to set as well, particularly in harder seabeds.