Anchoring overnight (peacefully)

[sarabande]

The thinner your chain the less it resists burying.
Jonathan

A suggestion which needs examining.

Axiomatically your kryptonite piano wire would therefore bury itself down to the rocky sub-strate.

Burying is a function of mass and (half) the surface area of the flat link; the ratio of mass to cross-sectional area is in favour of big thick chain.

 

[Neeves]

Weight in the rode does have some positive effects.

Catenary helps the anchor to set and increases the holding power in some very poor substrates and deep anchorages. It also enables a shorter scope to be used in some circumstances.

The problem is that it takes a great deal of chain weight for a minor improvement. Weight that would be much more efficient added to increasing the size of the anchor. There are also some minor negative effects to holding such as reducing the anchor's ability to dive in some circumstances.

If you have too big an anchor it cannot be set sufficiently deeply withe engine power of an auxiliary engine of most yachts that the chain is buried - so chain size is irrelevant.

Arguably chain on the surface subjects the anchor directly to veering and hobby horsing. Chain that is buried in the seabed is cushioned from the anchor and does not impact so much.

It does not matter how big your anchor is - if the windage of your yacht develops a rode tension of XXXkg then that is the hold the anchor will develop, big or small (unless its too small). If you think the big anchor develops more hold - you can make a fortune as you are developing energy from nothing. Though some of the tension is needed to bury more chain of the smaller anchor and the bigger anchor enjoys more direct attention.

That debate should be - do you want a big anchor shallower set with less buried chain at XXXkg or a smaller anchor more deeply set with more buried chain at XXXkg.

Jonathan

 

[Neeves]

A suggestion which needs examining.

Axiomatically your kryptonite piano wire would therefore bury itself down to the rocky sub-strate.

Burying is a function of mass and (half) the surface area of the flat link; the ratio of mass to cross-sectional area is in favour of big thick chain.

????

Please explain why mass allows a bar tight chain to bury.

Jonathan

 

[RupertW]

One thing I have noticed with the Delta, and this was observed when we were stuck in Astypalea for 5 days with a screaming Melteme, that the deltas on two yachts around us, gradually crept in and had to have a meter or so chain taken in every day. Contrast with the Manson Supreme, Rockna and Spade types, they just disappeared below the surface towards Australia. Holding was firm sand.

Certainly agree that Delta doesn't bury as deeply and I wouldn't be surprised if they did drag a meter on the first day of strong winds as I find I have to drop the anchor at least 2m upwind of where I want it to set, assuming I slowly build up reverse from low to high revs to fully set it. However as we rarely stay in an anchorage more than two nights you may well be right.

Many times each year the Delta fails to set first time but seems rock solid once set. Diving down after a failed set almost always shows weed or debris. Skyros near a fish farm was the worst for this. Nets and heavy bags and cans and all sorts of filth just 100m off a little resort beach full of swimmers.

 

[Chris_Robb]

Certainly agree that Delta doesn't bury as deeply and I wouldn't be surprised if they did drag a meter on the first day of strong winds as I find I have to drop the anchor at least 2m upwind of where I want it to set, assuming I slowly build up reverse from low to high revs to fully set it. However as we rarely stay in an anchorage more than two nights you may well be right.

Many times each year the Delta fails to set first time but seems rock solid once set. Diving down after a failed set almost always shows weed or debris. Skyros near a fish farm was the worst for this. Nets and heavy bags and cans and all sorts of filth just 100m off a little resort beach full of swimmers.

The Manson seems to go in within 1 foot of where it is dropped. If it drags on weed - it has to be brought to the surface and cleared as it chokes up. This instant set is a good feature as you are less likely to pick up other fouling on the bottom. The CQRs seem to drag many meters before setting - so catching any rogue ground chain in existence!

 

[prv]

Advantage of weight in the rode:
1. In lighter winds, slows down swinging and movement of the boat as the wind changes - not an advantage if the boat next is on lighter chain and swings into you.

I cant think of any more advantages.

I'll suggest one more - if you end up drifting around the anchor instead of pulling on it (typically at the turn of the tide), a rope rode can end up wrapped round the keel. Chain will hang straight down and avoid the problem. Since we switched to mostly rope (as above, due to weight issues under way) I've carried a small chum to send down the warp in places where swirling seems likely. When the boat is lying to the anchor it does nothing, but when things are slack it carries the rope straight down to a point below the keel.

Pete

 

[prv]

The Manson seems to go in within 1 foot of where it is dropped. If it drags on weed - it has to be brought to the surface and cleared as it chokes up. This instant set is a good feature as you are less likely to pick up other fouling on the bottom. The CQRs seem to drag many meters before setting - so catching any rogue ground chain in existence!

I'll second that, though my similar experience is with a Spade rather than the Manson. Snorkelling in warm places, CQRs that are set (often they're not set, just lying on their sides...) are almost always at the end of a ploughed furrow several meters long.

Pete

 

[Boo2]

Ah you are back to the catenery effect again which will get you into all sorts of discussions between those who have experience and maths and those who just have experience. I guess the question from your post is - "What advantage do you think weight in the rode gives?"

I was not talking about catenary, I meant weight of chain piled up, or stretched out along, the bottom. If you have enough mass on the bottom then that will resist motion on its own, no ?

Boo2

 

[Chris_Robb]

I'll suggest one more - if you end up drifting around the anchor instead of pulling on it (typically at the turn of the tide), a rope rode can end up wrapped round the keel. Chain will hang straight down and avoid the problem. Since we switched to mostly rope (as above, due to weight issues under way) I've carried a small chum to send down the warp in places where swirling seems likely. When the boat is lying to the anchor it does nothing, but when things are slack it carries the rope straight down to a point below the keel.

Pete

I well remember waking up at East Head at 2 in the morning with an out going spring tide - on my Sadler 25, using all warp rode. Broadside and drifting rapidly to the next boat, with rode between the fin a skeg, a quick solution was needed - no not the knife - Let all the rode go and tie the end to a fender. Motored round picked up the fender and rode. After that I had a heavy weight I lowered down the rode.

With larger boats I just would not consider using rope rode as chain is just so much easier to deal with (provided you have a winch!).

 

[Chris_Robb]

I'll second that, though my similar experience is with a Spade rather than the Manson. Snorkelling in warm places, CQRs that are set (often they're not set, just lying on their sides...) are almost always at the end of a ploughed furrow several meters long.

Pete

Having snorkeled on many anchors over the years, I have yet to see a CQR buried and not half buried on its side. I always wondered how they did not drag like that......... But then the wind would come and.........

 

[RupertW]

I was not talking about catenary, I meant weight of chain piled up, or stretched out along, the bottom. If you have enough mass on the bottom then that will resist motion on its own, no ?
Boo2

Yes in winds of a couple of knots certainly, but many times watching chain and anchor as I snorkel in crowded anchorages I can see that it takes a very light wind to stretch out a chain, and even a short moderate gust lifts it up as the boat is blown backwards slowly, so I don't think the weight can make any difference when it matters - ie when there is more than a few knots of wind.

 

[geem]

We don't need luck, we have at least some understanding of the different forces involved and make choices on the things that help keep us secure, not imaginary catenery effects under load or excessive scope that just gives a degree or two better angle when the angle is already fine.

+1

 

[GHA]

That debate should be - do you want a big anchor shallower set with less buried chain at XXXkg or a smaller anchor more deeply set with more buried chain at XXXkg.

I'd like an anchor capable of lots and lots of holding personally.

So a biggish one half buried that hasn't really started showing its full potential and will dig in further and really start biting if the force is applied rather than a smaller one already well one its way to max holding.

(Edit - actually, a big (bit oversize, not one off the QE2) anchor well set beats both )

 

[KellysEye]

>Take your head out of the sand and get a good snubber setup, far more effective at reducing forces on the anchor when the wind pipes up

A snubber works to a small extent but a riding sail attached to the backstay, or in our case the mizzen topping lift, works significantly better. It the reduces the the snatch load cuttng the swinging angle, that can reach 90 degrees, to 35 to 40 degrees. We bought one from Sailrite but I never saw another one on the 800+ boats I saw at anchor and always wondered why they didn't use one. http://www.sailrite.com/Anchor-Riding-Sail-Kit-12-5-Sq-Feet No doubt the majority will disagree with this post as usual.

 

[thinwater]

I was not talking about catenary, I meant weight of chain piled up, or stretched out along, the bottom. If you have enough mass on the bottom then that will resist motion on its own, no ?

Boo2

Just for fun, I dragged some chain (1/4" and 3/8") around with a load cell on it once. It depends on the bottom and the chain, but about 1-pounds per foot is a reasonable starting point. Since with any real load on the chain three sill be no more than 10-20 feet on the bottom, the direct contribution (ignoring for the moment important contributions to scope and surge buffering) is at best a few percent of the total. This makes sense, if you imagine dragging a little chain on the beach. So no, the chain doesn't hold anything directly. It is rather like an optical illusion. If you added an extra 200-300 feet it would help, but the other sailors would lynch you for taking up the entire harbor.

 

[thinwater]

I'd like an anchor capable of lots and lots of holding personally.

So a biggish one half buried that hasn't really started showing its full potential and will dig in further and really start biting if the force is applied rather than a smaller one already well one its way to max holding.

One exception may be a pivoting fluke anchor; a large one that is not buried can trip in a wind shift, while a smaller anchor that is deeply set will not. I've experienced both cases.

Also, a well set anchor cannot be tripped by the rode, a shallow set anchor can. Seen it happen.

I'm not sayin' bigger isn't better, only that there are common sense limits.

 

[GHA]

A snubber works to a small extent but a riding sail attached to the backstay, or in our case the mizzen topping lift, works significantly better. It the reduces the the snatch load cuttng the swinging angle, that can reach 90 degrees, to 35 to 40 degrees. We bought one from Sailrite but I never saw another one on the 800+ boats I saw at anchor and always wondered why they didn't use one. http://www.sailrite.com/Anchor-Riding-Sail-Kit-12-5-Sq-Feet No doubt the majority will disagree with this post as usual.

No,a riding sail is sensible,I made one to the Piota vee design.
It's the belief that a catinery will actually much good when the forces really get up that's been thrown out.
Do the maths and you'll see a good snubber setup will reduce loads on the anchor significantly there are large dynamic forces involved.

 

[GHA]

I'm not sayin' bigger isn't better, only that there are common sense limits.

Completely agree.

 

[NormanS]

>Take your head out of the sand and get a good snubber setup, far more effective at reducing forces on the anchor when the wind pipes up

A snubber works to a small extent but a riding sail attached to the backstay, or in our case the mizzen topping lift, works significantly better. It the reduces the the snatch load cuttng the swinging angle, that can reach 90 degrees, to 35 to 40 degrees. We bought one from Sailrite but I never saw another one on the 800+ boats I saw at anchor and always wondered why they didn't use one. http://www.sailrite.com/Anchor-Riding-Sail-Kit-12-5-Sq-Feet No doubt the majority will disagree with this post as usual.

My anchor sail is a bit more sophisticated than that. It is a twin sail, with slides on the luff to use the track on the mizzen, and the (two) clews sheeted out to the corners of the taffrail. With a relatively heavy (10mm) all chain rode on an 11m long keeled boat, I don't experience all this yawing about that others seem to find so troublesome, and which apparently subject their anchors to overwhelming loads.

However, different ships, different long splices. People have different ways of anchoring, and as long as they get good and consistent results, that's fine. There is no one absolutely correct and exclusive method.

 

[thinwater]

It's the belief that a catinery will actually much good when the forces really get up that's been thrown out.
Do the maths and you'll see a good snubber setup will reduce loads on the anchor significantly there are large dynamic forces involved.

No. It is the belief that catenary is not enough in water <30-40 feet with short scope that has been thrown out. I've done snubber testing for a magazine article (I use on 35' long) and I like high grade chain.

However, it is also easy to prove (calcultation or observation) that in 40 feet with 5:1 scope the chain will stay very near the bottom and that there is some curve to absorb shock. The point at which it is not enough depends on wind strength, depth, chain grade (weight), scope, exposure to waves, and how much shock is acceptable, with no single simple solution. Of course, since most of us anchor in <20 feet, the point is moot. I generally anchor in <7 feet, so I use a long snubber.