Dragging of anchors

[Motor_Sailor]

. . . but one good yank and all that nice elasticity has gone.

Climbing ropes are fully elastic and do recover. Each one has to specify the number of full falls that it can stand. The test is at almost their maximum load (Fall Factor 1.8) and the minimum is 5 with no increase in resultant loads, most are around ten and many of the thicker 11mm ropes are way in excess of that.

Reduce the loads to half it's breaking strain (ie 1.1kN) , and this figure goes up to the hundreds of time.

 

[thinwater]

Only up to a point. Climbing rope is designed to extend plastically (ie non-recoverably) after a major fall, because the climber on the end of it need to lose a lot of energy and not bounce around like Gromit cleaning windows. As long as you load it lightly your should be fine, but one good yank and all that nice elasticity has gone. How much of a yank? Well, a 70kg human falling 20m has 14kJ to get rid off, which is the same as a 4-tonne yacht moving at 2.6kt, so well inside a believable ballpark....

Please show us the data. Please explain how some of the climbing ropes are rated for as many as 20 UIAA falls. As for severe yanks on your yacht, a UIAA fall is different in several very important ways:
* It is fast (a fall) rather than slow. This is a major difference in how the fibers adjust during impact.
* It is over a sharp 160 degree bend. That is where the rope always fails. As others have pointed out, a climbing rope snubber is always used with considerable attention to this bend.
* No non-climbing rope can pass the test at all.

I will also add that the forces are on the order of 25% of BS (up to 30% is permitted by the standard). The SWL of nylon rope is given as 12% by ABYC and engineering standards; if you are operating beyond that stress no rope will last, but a climbing rope will reduce stresses more than other types.

The boat might be moving upwards rapidly for a short distance, but to imply a yacht will be drifting backwards at 2.6 knots conflicts mightily with observation. That number appears to have been snatched out of the air.

The arguments seem reasonable at first, but upon examination by their parts, appear to be contrived. I'm guessing you have not tried climbing rope snubbers nor worked with climbing rope in a systematic way. I have tested such ropes over long periods, in the field, in the lab, and even tested sections after long service using lad cells to measure both strnegth and elasticity. Yes, there is degradation, but not as you describe. There is much field experience that it works. Climbing ropes seem to have 3 vulnerabilities in the field: UV, chafe, and the fact that they are not available in sizes larger than 11mm, which if used as a long snubber, has proven quite suitable up to about 45 feet LOA. They are a consumable item, replaced after a few hundred nights, depending on the weather.

And everything that Motor Sailor said. On my last boat I used one of my retired ice climbing ropes (8mm) as a bridle. I knew the fall history, which for ice climbing means some rappelling and no leader falls (you really try hard not to fall leading ice). It simply had more seasons on it than I was happy with.

Curiously, the bridle on my new boat is Dyneema. I use a nylon rode so I do not need shock absorption. In fact, an all-nylon rode can stretch too much, and the non-stretch bridle reduces yawing because it does not distort in a side load. Different ropes for different purposes.

 

[JumbleDuck]

Climbing ropes are fully elastic and do recover. Each one has to specify the number of full falls that it can stand.

If there is a limited number of falls then there must be some plastic deformation going on. Remember that plastic deformation doesn't prohibit later elastic behaviour - it just limits it a bit.

 

[JumbleDuck]

Please show us the data. Please explain how some of the climbing ropes are rated for as many as 20 UIAA falls.

Why shouldn't they be? The important thing to note is that there is a limit.

The boat might be moving upwards rapidly for a short distance, but to imply a yacht will be drifting backwards at 2.6 knots conflicts mightily with observation. That number appears to have been snatched out of the air.

I gave the calculation leading to 2.6kt. I don't use an anchor snubber, but in bouncy conditions at a pier I think it's very common for the boat t be moving at a slow walking pace - or more- when brought up by ropes.

Climbing ropes seem to have 3 vulnerabilities in the field: UV, chafe, and the fact that they are not available in sizes larger than 11mm

... and the wholly intentional plastic damage caused by shock loading. As other have described in detail.

 

[thinwater]

Why shouldn't they be? The important thing to note is that there is a limit....

But how is this a surprise or relevant to the conversation? The test is extremely severe and the impact limit is provably much higher than higher than any other nylon rope. Of course there is a limit. Chain would have failed the test. Dyneema fails easily. Webbing fails (sometimes it passes one drop).

Others have described plastic damage without presenting any data. We'll return to that when we see it. I doubt they will see any within the WLL that is not related to fiber wear. Yup, I've researched it.

We're not talking about a pier, are we? (By the way, climbing rope is a poor choice for dock lines because of poor chafe resistance.) I would also suggest that if the boat is moving that much at the dock it is not tied up terribly well. Springlines, fore aft on both sides, should be properly adjusted to reduce the bouncing. Even with tides, you can do much to control slack.

But mostly we're off the point and nit picking the science. Climbing rope as a snubber is well proven in the field. We could try to understand this repeated observation in light of theory, potentially growing a more accurate theory and understanding in the process. Ropes are very complicated. This process is called science.

 

[zoidberg]

I've been trying hard to follow most of this, and to translate the wisdom into 'what should I be doing' without getting in a tizzy. I nod to the 'currency of know-how' which has emerged on here - it is valuable, and simply wasn't available before now, before e-forums like this and YouTube. There's virtually nothing useful about anchoring, as I recall, in the RYA Syllabus..... That may reflect the observation that many in the RYA Training World are dinghy and dayboat sailors, as are the 'editors' of saily mags.... i.e. they know where to buy an anchor if they ever want one......

Like Thinwater, Neeves, and others I've done a wee bit of climbing here and there and picked up on some of the realities of rope. I, too, "really try( ed) hard not to fall leading ice" or leading anything else.... although that wasn't always a free choice way back when UIAA and climbing walls weren't invented. You got it right first time. It was rare you got to discuss your mistakes.

I marvel at the lateral thinking of the likes of Bill Tilman, who'd anchor into the ice in the protective lee of a large ice-floe - or Bob Shepton, who's driven pitons into a 2000-foot vertical rock wall to secure his boat alongside for the night. Ay caramba! That perhaps feeds my attitude to 'extreme anchoring', but I'm happy to read of others doing it. Not for me the crucial choice of which comfy nook in a Carib mangrove swamp one jump ahead of a hurricane, nor tucking in behind a clay-and-boulders islet out of the path of wind-driven bergy bits coming off the next-door glacier while sweating blood that the wind doesn't shift.

For me, the most challenging situation I s'pose I'll encounter is being secured alongside a rusty old trawler in a harbour like Fishguard, Newlyn or Ilfracombe, with long lines fore and aft out to the quayside, while 'surging and scending' hard as the storm-driven seas roll in, then roll right around the harbour and take us again from the rear. That could cost a few bob in new ropes.

Here are a few vids I've found, of late, to ask difficult questions and provide some of the answers.....

and very much also https://www.youtube.com/watch?v=52vu7bbvqC0

( We're permitted only 2 vids directly )

 

[noelex]

Tie up to rocks? That’s for wimps .

Real men secure their boat by freezing it into the ice .

 

[zoidberg]

Tie up to rocks? That’s for wimps .

Real men secure their boat by freezing it into the ice .

Aye, laddie! But some of them didnae intend it!

 

[LittleSister]

I think the best method of determining anchor performance is simply observing how the anchor behaves on the seabed.

I don't doubt the principle, but since sailing on England's East Coast I've never seen the sea bed! ( Despite it usually being within boathook prodding distance. )

 

[Neeves]

I don't doubt the principle, but since sailing on England's East Coast I've never seen the sea bed! ( Despite it usually being within boathook prodding distance. )

Much more common than being able to see it!

There is also a suggestion that when you arrive your anchorage at 2am the first thing you need to do, once the anchor is deployed, is get out there in the dark and check the anchor. In the real world you are enjoying a quick drink and congratulating your selves on have arrived before the strong winds - and then you go to bed.

Jonathan

 

[noelex]

I don't doubt the principle, but since sailing on England's East Coast I've never seen the sea bed! ( Despite it usually being within boathook prodding distance. )

I was anchored off the east coast of the UK a couple of weeks ago and I must admit that I did not much feel like going for dive .

Observing how anchors work underwater takes quite a bit of effort even in ideal conditions, but with cheap waterproof cameras that can strapped to the anchor, lowered from the tender, or even attached to an underwater drone, it is now possible to see what is happening even in unfavorable conditions.

I do not see many boat owners going to this trouble, but if you are interested in anchors it is great way to learn how they are performing in real life. If the photos and videos are shared, everyone can benefit.

There are a very diverse range of conflicting opinions and advice on anchor threads, but photos and videos provide some objective evidence that people can judge for themselves. I hope more people can become involved.

 

[Neeves]

Snubbers,

The interesting facet, that those that do not use snubbers will not think about, is the amount of elasticity that can develop. Having a 10m snubber, stretch of 1m is not unusual. The snubber is stretching 1m simply because it is absorbing the kinetic energy of the moving yacht - and if the snubber was not there then that same energy would be lifting the chain, each time, and if not enough chain the energy would be imposed on the bow roller and anchor. Keeping the chain as stable as possible, not lifting and falling, will reduce the amount of twitching of the anchor - and in the extreme, in partnership with the chain, will ensure the anchor does not suffer shock loads.

Having a 2m snubber is keeping the load of the windlass - but it is too short to absorb much energy. The fear of long snubbers is that they tend to be far forward of the bow (and the hook fall off in light wind as it scrapes on the seabed) - attach at the transom.

I mention above 1m stretch is not unusual and cognisant of the idea you do not want to over stretch your snubber - this is the reason to have snubbers you can extend, rather than using a storm snubber. If the 10m snubber stretches 1m then a 20m snubber will also stretch 1m, but one is 10% of length, the other 5% of length.

It i a common question, what to do in strong wind, in term of snubbers. One idea is a heavy duty snubber, the problem is how to attach, and when. You could use 2 snubbers, one everyday and one storm, allowing the storm snubber to come into play, at say, 30 knots. But this seems overly fiddly and storm snubber will have less elasticity (for a given tension) - possibly introducing unnecessary shock loads. If you extend your snubber you also extend the chain, so you double up on the ability to absorb that energy, more chain and more snubber - and its easy to do.

There is no suggestion that snubbers, of any sort, do not wear. They are consumables, which is why we carry a spare set. Recycling from a gym fits neatly with, (recycling - where they would go to landfill) and consumables - as you are more inclined to retire them and use a new, recycled set.

Before we started using climbing rope we had 2 fail - when they fail - you know - its like a gunshot.

As Thinwater said 11m climbing rope is good for upto about a 45' yacht - and our cat, 38', has the same windage (but about half the weight) as a 45' monohull (I've measured it). Strarzinger on Hawk used climbing rope and Hawk was about 45'(?). Climbing rope as a snubber is not new and is very well tested. You could source rope larger than 11mm - but it would need to be specially made. I did look at the idea (when I wondered about storm snubbers) but you need to be willing to buy a rather long length- and its easier to use longer lengths of recycled 11mm. For a bigger yacht you could alway use 2 x 11mm climbing ropes

The odd thing about 10m (or thereabouts) snubbers is their lack of acceptance. I see 2m snubbers, but not that often, I see people with nothing, or nothing you can see (they might have a chain lock or a 500mm length of rope) but maybe nothing at all. I very seldom see long snubbers.

Jonathan

 

[zoidberg]

...... but since sailing on England's East Coast I've never seen the sea bed! ( Despite it usually being within boathook prodding distance. )

That's odd! In my limited experience of the East Coast labyrinths, the sea bed shows itself very extensively, with unflagging regularity, at least twice a day.... hence some of Mike Peyton's favourite cartoons.....

 

[Neeves]

I was anchored off the east coast of the UK a couple of weeks ago and I must admit that I did not much feel like going for dive .

Observing how anchors work underwater takes quite a bit of effort even in ideal conditions, but with cheap waterproof cameras that can strapped to the anchor, lowered from the tender, or even attached to an underwater drone, it is now possible to see what is happening even in unfavorable conditions.

I do not see many boat owners going to this trouble, but if you are interested in anchors it is great way to learn how they are performing in real life. If the photos and videos are shared, everyone can benefit.

There are a very diverse range of conflicting opinions and advice on anchor threads, but photos and videos provide some objective evidence that people can judge for themselves. I hope more people can become involved.

Not all of us own a personal bank - have you looked at the cost of underwater drones? Camera on the anchor?, at 2am. Most anchors when well set are buried (you will need a lot of disposable cameras) and in murky waters a camera on a stick is going to be no better than no camera. It is better to use an anchor on which you can rely than have the need to dive on it every time you use it.

Sadly - in the real world - the need to check your anchor every time you deploy it - will not happen.

There are some great underwater images of anchors - as you well know good image do not make good anchors neither do they result in the correct interpretation. I believe there will be an article in Practical Sailor with considerable quantitative data to back it up correcting some glorious misinterpretations in the next few months - something to look forward to. Better using a reliable anchor, and there are enough models from which to choose.

Jonathan

 

[Uricanejack]

When the wind gets up, I check my anchor by feeling the cable.

If there is a problem you will feel it. Works for spiders

 

[Uricanejack]

I was anchored off the east coast of the UK a couple of weeks ago and I must admit that I did not much feel like going for dive .

Observing how anchors work underwater takes quite a bit of effort even in ideal conditions, but with cheap waterproof cameras that can strapped to the anchor, lowered from the tender, or even attached to an underwater drone, it is now possible to see what is happening even in unfavorable conditions.

I do not see many boat owners going to this trouble, but if you are interested in anchors it is great way to learn how they are performing in real life. If the photos and videos are shared, everyone can benefit.

There are a very diverse range of conflicting opinions and advice on anchor threads, but photos and videos provide some objective evidence that people can judge for themselves. I hope more people can become involved.

Many years ago studying physics in school I learned about some strange obsessive chap. Rutherford I think. Who spent his life drip drops of oil through a hole and measuring the deflection caused by a magnetic field. To determine the charge on 1 electron. One of the most important scientific advancements of his day.

My thought at the time "Bloody hell" there got to be more to life than that. Like beer and girls. What an edgit?

No doubt the anchor watchers are making a very significant contribution to yachting.
However. Watching videos of my anchor give me the same impression.

 

[noelex]

I mention above 1m stretch is not unusual and cognisant of the idea you do not want to over stretch your snubber - this is the reason to have snubbers you can extend, rather than using a storm snubber. If the 10m snubber stretches 1m then a 20m snubber will also stretch 1m, but one is 10% of length, the other 5% of length.

I don't think this is correct. A longer snubber of the same diameter and material will stretch a longer distance than a shorter snubber when subject to same force.

 

[noelex]

My thought at the time "Bloody hell" there got to be more to life than that. Like beer and girls.

OK, you have got me there.
Agreed. Beer and girls are better than anchors .

 

[Neeves]

I don't think this is correct. A longer snubber of the same diameter and material will stretch a longer distance than a shorter snubber when subject to same force.

I think you are correct, but can you quantify 'longer' in longer distance, and thank you for the correction. In fact the 2 stretch the same length, though there might be a slight difference depending on the reduction in cross sectional area (don't know). I glossed over the detail, see below

I think you are quoting Hooke's Law but you are ignoring the concept that as the snubber stretches it (and the chain) are absorbing the kinetic energy of the moving yacht and the force imposed on the short snubber and that on the long one are not constant nor the same (they start the same). But the short snubber is used with less chain and to deploy more snubber you, in the way we use it, must deploy more chain. This is because the longer snubber, (with chain) results in the need to extend more chain and you need to introduce the additional benefit of the longer chain catenary. Frankly the maths is far beyond me (but JD possibly has the answers at his finger tips) but in practice the longer snubber of 2 x length, with commensurate increase in chain deployed (extra snubber length + stretch), stretches much less than the shorter one 1 x length).

Snubbers do not work in isolation - they work with the chain, both the snubber stretches and the catenary straightens I'm guessing they stretch and straighten at different rates and times and these vary by the amount of straightening and stretching already imposed - very movable feasts. If the chain is already pretty taut then the snubber will need to do more work - one hope to have enough chain that they can continue to share the work.

I just quote what I see.

Jonathan

 

[Neeves]

diving on anchors

Issues in Australian waters with regard to being eaten are in keeping on an anchor thread where the idea of casting doubts on safety are commonplace.

This little snippet may give food for thought, maybe food is the wrong word

https://www.theguardian.com/environ...-decades-spotted-near-spains-balearic-islands

Jonathan