The quickest way to start a brawl is to walk into a bar full of sailors and yell:
Who believes that chain catenary improves anchor holding?
The fight usually breaks into two opposing gangs: those who believe that having a lot of chain on the bottom increases holding, and those who have actually observed an all chain rode being pulled bar straight in strong winds who cry “bullshit”.
But the reality is much more nuanced, and understanding that can help us anchor more safely…and avoid bloody noses in bar brawls.
Let’s turn our attention to the former: how to use catenary to help us anchor, and when not to rely on it.
The Governing Theory
First off, a bit of theory. I’m sure most of us know this, but it’s worth revisiting, because it’s the basis of everything else I’m going to write about:
(By the way, Danforth-type anchors, including the Fortress, are, as far as I know, the only exception to the rule. They set better if the stock is lifted off the bottom a bit.)
Let’s leave ultimate holding out of it for a bit (we will come back to it later) and focus on setting.
There are three ways we can decrease the pull angle and thereby help our anchor to set:
- Increase the scope.
- Increase the catenary.
- A combination of both.
I’m going to dive into all three in more detail, but first a story.
A Lesson Learned
About 20 years ago, we changed from a CQR to a SPADE anchor, both set on 7/16″ (~ 11mm) G40 (high test) chain. The new anchor worked so well that we got a little slap happy about our anchoring technique:
- Drop anchor.
- Let the chain run to 5:1 scope before putting any load on it.
- Wait for the breeze to straighten the boat out.
- Back down hard to set.
- Have tea.
In thousands of sets, over some 15 years, from the Bahamas to Greenland, our SPADE only failed to set a few times, and we never dragged it once set.
Then, six years ago, we changed to 3/8″ (~ 10 mm) G70 (heat treated) chain, both to reduce the weight in the bow and to increase the amount of chain we could carry from 340 to 400 ft (103 to 122 m)—in the high latitudes, where anchorages are often deep, there is no such thing as too much rode.
Suddenly we were experiencing more failures to set, particularly in soupy soft holding. At first we were totally perplexed. What the heck? Had we forgotten how to anchor?
And then the light went on:
Hi John.
Since I’ve been participating on AAC a few years now, and learned a lot from it, the conclusions in this article come as no surprise, and they all fit with my understanding and experiences. That, however, hasn’t always been the case.
Some years ago I was a firm believer in the importance of the catenary curve to get good holding power. I also frequently gave advice accordingly. When I had to do some math to explain why a steel wire wasn’t as good as chain, (specific question), I found, to my frustration, that I was completely wrong. Then, I started looking around on the internet to find more opinions and thinking about what I’d been observing a lot of times at anchor in heavy weather; a chain with no real curve.
Then I realised that I’d been filtering what I observed. My beliefs made me overlook the proof I was looking straight at. Yet another illustration of the animal species Homo sapiens, whose “pure logic” is often lacking so many elements in its foundations it’s anything but logic. This realization led to a somewhat embarrassing complete change of “opinion”. I’m happy that I’m still not too mentally rigid to do that exercise.
Hi Stein,
Don’t feel bad, I did exactly the same thing…or maybe we should both feel bad. Seriously, it’s just so damned easy to let our preconceived notions blind us to reality.
You guys are not alone, I did it as well. Growing up it was always mixed rodes and then I went to boats with large chain and no snubbers anchoring in deep water and with very different motions. When I switched to cruising size boats with all chain, I was a big believer in the chain weight until that first real storm when I realized how wrong I was and started looking at the numbers. Looking back, I think that in certain conditions, even the boats with large chain may have benefited from snubbers. The piece of the puzzle that is still missing to me is the damper in the system, we have figured out springs but to have a stable system you need damping and pulling the boat through the water seems inadequate to me (the people who tail drogues off the stern may be onto something here).
Eric
Hi Eric,
That’s interesting. Could you expand a bit on the difference between damping and springs? I think I get it, but certainly not clearly.
Hi John,
A perfect spring is basically an energy storage device. If you were to attach a weight to the spring and drop the weight, it will oscillate back and forth each time returning to the original height of the weight. Where people may be aware of this is when they have a car with worn out shocks, when you hit a bump, it keeps bouncing for quite a while. On a boat with a perfect spring for a snubber, think of driving over your anchor on a calm day at 2 knots, assuming the anchor didn’t drag at all and you cut the engine power right before the rode took up load, you would bounce back and end up going backwards at 2 knots (this ignores resistance from the water on the hull).
Since a spring is simply an energy storage device, sometimes you want to actually take energy out of the system, usually in the form of heat and this is called a damper. The damper takes energy out so that you don’t bounce back doing exactly the opposite of what you had been doing going in. In a car, we have shocks which keep the car from bouncing for a while after a bump, they allow some bounce to absorb the impact but then quickly dampen out further oscillations. On an anchored boat, if you are underdamped the boat will come up towards the anchor too much when it rebounds. This allows the bow to fall off and it allows the boat to get reverse speed before it is met with resistance from the anchor rode. Snubbers and chain are not perfect springs but on their own, they are underdamped and for most boats, I don’t think that the water resistance is sufficient damping. How much damping is required is very dependent on the boat design (boats that sail around at anchor would require more), the rode design and the conditions. Some of the better behaved boats actually probably would not benefit from a damper in a measurable way but a significant population of boats appears underdamped when I watch them.
For most conditions, a damper would simply serve to keep the boat better behaved and lessen shock loading. In gusty winds from different angles, a damper that is independent of the anchor rode (like a stern drogue) could actually keep the boat from getting significant speed up before fetching up at the end of the rode. The drogue setup that colin uses is a form of a damper but because it is outboard of the snubber, it is only damping the spring of the chain (catenary and stretch). A drogue attached tight to the bow but held in the water would be a decent form of a damper but I am not sure how you would implement it in practice.
Eric
Hi Eric,
Thank you, I am much clearer in my mind now…at least about that damping and springs!
This also explains something I have long observed: past a certain point, adding more spring to the anchoring system seems to be counter productive since the boat just ends up surging around more and loads go up, not down. Have to think more on that.
Very interesting thread thank you guys,
Two years ago we were sheltering at anchor on the tip of the Coromandel Peninsula in NZ, in a beautiful bay called Port Jackson. A 30 knot SW wind was alternating from coming straight over the lower part of the headland, to hugging the bluff at the Western end and gate crashing the anchorage from seawards. This resulted in alternating gusts hitting us from the port bow and then the starboard bow and we were skating around accordingly. Dusk was coming and we were looking at a disturbed night with anchor watches. I had anchored as close into the shore as was seamanlike in about 4.5m of water and was using only about 6 to one scope in case the wind veered in the night and drove us further towards the sandy beach. If I had anchored any further offshore, we would have been in the wave action from the wind coming around the bluff.
So we had all chain rode (10mm) and a 7 metre nylon snubber in place. But how to stop the boat from sailing around to her anchor so avidly? Without knowing it, I needed a dampener.
My experience as navigator on commercial ships was that catenary does act as a great dampener and the first response to yawing was always to let out more chain. The catenary takes up the slack in the chain, then eases it out again. But in the shallow water chain induced catenary was not going to happen for us. I wanted to be instantly ready to retrieve the anchor and head out to sea, so adding any weight to the chain was not an option (having John’s sage words on kellets ringing in my ears).
What we ended up doing was setting our snubber and then paying out a further 20 metres of chain from the bow roller creating a ~ 5m bight lying on the flat sandy bottom. It worked rather well in two ways, the weight restoring a moderate catenary between gusts acted as a dampener – have I got that right Eric? Secondly, the drag on the sea bed slowed the bow from yawing to the extremes of the rode. So much so, we set the anchor alarm, went to bed and slept soundly. This will obviously work only for a shallow anchorage with a clear seabed and chain wear may not be good over longer stays.
I like that this requires no special setting/retrieval method – just the windlass and snubber. Anyone else experimented with this dampening “hack”? We have used it quite a few times since but never in full gale conditions and would be keen for some feedback.
Rob
Hi Rob, I love your “out of the box” thinking. Thanks for sharing.
Dick Stevenson, s/v Alchemy
Hi Rob,
That’s certainly interesting. Using my knew knowledge from Eric, I would say that you had created a damper, which is really interesting, and, I think, far more use in this situation than any sort of spring.
That said, one worry that immediately jumps to my paranoid little mind is if the bight were to catch on any sort of obstruction on the bottom there might be a huge shock load on the gear, and one side of that shock would be transmitted directly to the gear without benefit of the snubber. And further, if the chain stayed caught in the obstruction one would then be in a very nasty situation trying to deal with it as huge shocks were coming up the chain. Add in a few waves caused by a wind shift, and I get a real case of the horrors.
In these kinds of cases, Phyllis and I have done well with a shorefast to the land to windward and our best bower set, at a large angle, to the shorefast to keep us off the land. Not only have we had some comfortable nights this way, but if the wind shifts, dropping the shorefast is easy and quick.
Hi Rob,
You had indeed introduced a damper in a clever way that had never occurred to me. Your experience also highlights that the forces of the damper are necessarily lower than the forces of the spring and it appears that in your case, the relatively low forces of the chain dragging on the bottom and being pulled through the water were sufficient. By the way, catenary acts as a spring and the only damper associated with it is the resistance of the water on the chain.
There is a technique known as a hammerlock (thanks to Drew for teaching me the name) that goes a little further and uses an anchor dragging around on the bottom at very short scope instead of your lazy loop of chain. This similarly acts as a damper and people report good results with it, I have only used the technique once but it did work in that case.
I often do simplified calculations of stuff associated with sailing and find it to be very helpful to getting my thinking in the right ballpark. Unfortunately, dampers are a tricky subject and the math involves differential equations so it is not something that I have ever taken the time to try to play with
Eric
Hi Rob,
As said, I like your “out of the box” thinking, although what John said about having a drooped chain looking for trouble on the seabed concerned me also.
I was wondering whether a weight dropped straight to the seabed with a bit of slack might have the same results: say a small diameter nylon line with a weight attached. At first, I was thinking of one of those mushroom anchors the chandleries sell for dinghies, but then I thought of the kellet I carry anyway which also has more weight.
The kellet would be quite unlikely to foul on the bottom and were it to do so, would not be a huge loss the way fouling the bower rode would be.
I am also thinking that hanging it off the stern might have even more of a dampening effect than off the bow.
Random thoughts.
My best, Dick Stevenson, s/v Alchemy
Hi Dick,
The sole time I can remember trying the hammerlock, we used a small bruce on a nylon rode equivalent in diameter to the snubber. For us, this worked well, I believe Drew may have given more thought to actually what the “anchor” should be. With the snubber sized nylon, it wasn’t stretching much at all at the low load so we didn’t add another spring but it would have provided give had it snagged. One thing to keep in mind with this is that you will be forced to constantly adjust the rode length in an area with any real tide as otherwise your scope will vary a lot and it really need to be short scope. While the hammerlock is probably the best damper that I am aware of, it is far from an elegant solution and I wish there was a good way to implement one without the complication. It feels to me like a damper reacting to the water would be ideal much like Colin’s drogue except not on the far end of the snubber. I wonder if anyone with a waterline fitting at the bow has ever tried a drogue?
Regarding stern versus bow placement, I believe that bow should be superior for a damper. The reason is that I don’t like the spring force and the damper force being separated by something that can become a lever. If we think about the relatively simplistic example of a boat surging forwards due to the snubber recoiling, with a small stern damper, the speed is kept low which is good. However, once you start going backwards again, the damper is now providing a forward damping force to the stern so that as soon as the bow has fallen off and is not straight anymore, it is a torque that wants to spin the boat 180. If you have the damper attached at the same place as the snubber, it is just as effective as you go backwards but when you rebound forwards, it is not trying to spin the boat around. Also, it provides much needed damping in the yaw direction.
Eric
Hi Dick,
I was intrigued by the idea of having the chain looped down behind the snubber, and Johns cautionary comments had me as well. I especially like your idea of using either a small secondary anchor that wouldn’t set, or a kellet if you happen to have one on board.
However I personally wouldn’t advocate mounting the “damper” at the stern as this might have the bow go to one side which then is leeward, and the stern doesn’t completely follow, creating a windward side. One effect would be that the boat stops sailing around, which is good, but then it would always present a broadside to the wind – which doesn’t matter a lot in light winds but might be counterproductive during a blow. Having such a “damper” at the bow would effectively slow the lateral bow movement while allowing the hull to align itself with the wind.
Hi Eric and Ernest,
My my, I do like having these random thoughts responded to by thoughtful people. Thanks for your comments and I agree that the stern deployment has that possibility/likelihood that I had not considered: I was only thinking of the yawing, not the surging.
My best, Dick
Hi everyone,
Thanks for the responses. Firstly to Eric, haha yes it’s obvious now – the catenary acts as a spring in the forwards direction. What I meant was my observation was that catenary acted to calm yaw action noticeably, reducing an otherwise violent pull from a bar tight chain that precipitated a counter movement of the bow with ever more extreme gyrations until the anchor broke out. But this must be the action of a spring, not a dampener, to the speed and direction of the yaw.
And a wonderful example of constructive paranoia from John, exactly what makes this site so valuable. I thought I had been careful to add there should be no obstructions on the seabed and to be fair, mostly these can be spotted over sand in shallow water. But I guess we could pick up an unseen abandoned anchor or such like with serious consequences – I will need to give that some more thought.
However, I’m equally not keen on shore-fasts for lying off a beach, no matter how golden and inviting the sand. Especially one that could quickly become a surf beach with a wind change – too hard to recover quickly.
Similarly, I am just not keen on any kind of weight, line or drogue attached to the chain rode (other than the snubber) that needs to be remembered and dealt with trying to exit an anchorage at 02:00hrs.
Finally, I am not keen on any kind of drogue attached on the bow, no matter how effective that would likely be. I just don’t fancy having to remember to remove it in a hurry, even if I could rig some kind of easy release.
And nor do I like anything in the water attached at the stern. What Eric explained so well scientifically, bears out my experience that to do so delays the stern in coming back into line with the wind. This exacerbates “sailing” at anchor rather than reduces it – I know, I tried it.
We don’t seem to be any closer to a fool-proof dampening solution that reduces yaw for a monohull. I should mention in normal conditions Bonnie Lass lies beautifully at anchor, but in storm force gusts from a violent cold front we need all the dampening we can get. Look forward to more on this valuable topic.
Rob
Hi Rob,
Good analysis. With those factors in mind, I always come back to a fundamental truth: keep it simple.
That said, getting out of a shorefast situation can be very quick if set up right: Just drop the shorefast (come back for it later) and then we are instantly anchored only, but with said anchor further from the beach than it would be in a situation where we were trying to get in the lee, but did not use a shorefast. Reminds me that I must write about shorefasts some time.
They are not something we like to use often, but in certain situations they can be very useful.
Hi Dick, Ernest,
I just saw the comment about using a mushroom type anchor or kellet, which I think you intend would be set directly from the bow itself?
I am not sure this would have the same effect – having a longish snubber (7 metres) means that the chain bight was stretched out ahead of the vessel and acted to dampen the movement of the bow and the chain itself – in much the same way Colin’s drogue set from the snubber hook did here: https://www.morganscloud.com/2015/02/23/stop-swinging-around/
Keen to hear any results if you try it (in a strong blow say 30+ knots). Still not sure about having another thing to remember in the middle of the night.
Rob
Hi Rob,
I guess in an emergency when we had to leave, I would rather being dealing with Colin’s small drogue than another anchor hanging off the bow.
Rob,
We’ve been doing similar things routinely. If anchored in 15ft of water, we’d typically put out about 5:1 scope plus a further 25ft snubber and then drop a deep loop of chain – probably another 15 – 20ft so that when all is said and done we’ve probably got about 125 – 150ft of chain involved.
I don’t typically look for the chain to touch bottom as you did/do, though it might occasionally, but the deep loop certainly reduces the sailing we would otherwise do. (We still do too much in my mind.)
I can see the danger in snagging the loop on the seabed – but then the main rode can also get snagged during a lull and while that would be protected by the snubber, the loop would also be half protected by a long snubber – wouldn’t it? If something major caught on the side without snubber, one could always let out even more rode and another snubber if needs be! (My wife already thinks I’m crazy with the amount of chain I use to anchor!)
Thanks Bill,
Nice to have validation that the technique is working for others.
In deeper water, I have set the anchor with a bight well off the bottom, and find it especially useful in a constrained anchorages where you may only be able to anchor on 3:1 or 5:1 scope. We have dropped 20 metres of chain with the bight off the bottom and it really does calm the boat down (we have quite high clipper bows susceptible to wind gusts). It suggest to me that the dual action of the spring and dampener (chain moving through the water column as Eric suggests) is doubly effective.
But I also think John is correct and the main snubber would provide you no protection in the event of a snag, but you are most certainly correct in your assertion that you could veer more chain and attach a secondary snubber using a rolling hitch – sorting the whole mess out in the morning.
Having wrapped a chain figure of 8 around a Pacific coral bomb in 18 metres of water, in my first anchorage attempt in the Pacific Islands, I consider myself somewhat qualified in such matters. Since that event, we have religiously trolled over deeper or murky anchorage grounds using the fish finder in our Raymarine MPS (who knew such things had a use on a yacht), to provide a continuous image of the seabed before dropping our hook. Once I learned that hack, I haven’t snagged the bottom again, even with laying out a large bight of chain as we have on numerous occasions.
Cheers, Rob
Very well written! Let me add a few more variables:
Depth. I am particularly sensitive to this, since as a multihull sailor I think 4-5 feet is plenty (if no large waves). Really, catenary is as much about the amount of chain out as the scope. In other words, 5-1 scope in 4 feet is about 35 feet of chain. It straightens out even earlier than you mentioned and is basically useless by 15 knots. On the other hand, in 40 feet of water that would be 215 feet of chain, which may work to 25 knots at least. But at 60 knots they are both pretty straight. But what about 400 feet of chain? It is really quite hard to straighten that unless there is considerable wave exposure.
Straight vs. “still on the bottom.” An interesting exercise is to calculate the difference in length between a chain that is just lifting off the bottom and one that is straight. Generally it is less than you think, only a foot or so. Many sailors believe that because they can see some curve that means it’s still working. In fact, the difference in length and the force required to straighten it may have rendered it ineffective. The graph above is a nice illustration of how abruptly the catenary cushion ends.
Rode angle vs. anchor holding. I did a bunch of tests relating to holding capacity vs. up-lift angle. It is not the same for all anchors. Fortress holds well with considerable up-lift, once deeply set. Anyone who has tried to break out a Fortress after a blow knows this! Anchors with more shallow angles–Claw, Mantus, and Spade–lose holding capacity fast at short scope. Others–Manson and Rocna–are just a little better, but nothing like Fortress. The setting behavior of plow types is so dependent on the bottom general rules were tough, but generally not so good.
Scope vs. Setting. The other thing to remember is that although an anchor is set and holding at short scope, that short scope may prevent it from digging deeper as the storm builds. Put another way, an anchor at long scope will dig until the rode prevents it from going deeper, but an anchor at short scope will be robbed of that chance to go deeper. when in doubt, set at VERY long scope before shortening up. A correlarly is to add scope as soon as the wind starts. Once the wind is up, all boats will swing the same way. In this way the anchor gets the best chance to dig. Adding scope later, once the anchor starts t move, won’t do as much.
Soil vs. liquefaction. Some soils will consolidate around the anchor if allowed to set quietly, after which deeper setting is possible. Some times a series of increasing pulls, 20 minutes apart makes a huge difference. This is typical of soft Chesapeake mud. Other soils can be very prone to liquefying if the anchor is twitched by the rode. Coral sand and silt are bad this way. One more reason to stop yawing!
It’s really complicated. Every anchor, every rode, every boat, and every bottom combine to change the math. I can change the rank-ordering in anchor anchor test program by changing the expereiment. Isn’t that depressing.
Hi Drew,
Sounds like we are on the same page right across the board, except that I, to keep things simple, deliberately did not get into the effect of depth. That said, you are, of course, right that catenary does have more effect in deeper water, assuming the same scope ratio. I didn’t go there because that doesn’t alter the conclusions materially since even in very deep water with a lot of chain out, the effect of catenary is very small by the time its blowing hard enough to the generate loads that would drag a well set modern anchor.
And, as you say, all of this is complicated. The great news is that my experience is that with a modern anchor upsized at least one size and preferably two, as we recommend, these complications matter little in whether of not we get successfully anchored a good 99% of the time. And, as I said in the post, since we have had the SPADE, we have never dragged, once set. Although that’s a lot because we set the hell out of it with the engine, as you recommend. More on that in a future chapter.
Yeah, the engineer in me loves to make things complicated. As you say, 98% of the time, good fundamentals are all you need. Really, anchoring is dead simple… once you get the right set-up.
There is a reason, however, for my obsessive view. I think I read once that one of the very few places your Spade ever dragged was in the Chesapeake Bay, in Solomons Island (please correct me if it was someone else). The bottom is pudding, or as the locals say, “the water is just thicker at the bottom.” I recall that short scope was part of the problem. In fact, some of my favorite places are even worse; you can barely feel the bottom with a paddle. In testing, I only ranked the bottom as “very soft” if I could easily push a paddle in 3 feet with one extended arm (no fair leaning a shoulder over it). The other problem is plant and shell debris that clogs anchors and reduces holding. Often sticks under the rode prevent the anchor from settling into thicker layers. In recent testing, 45-pounds anchors by Spade, Rocna, Manson and others generally held 500-600 pounds near Solomons, which just aint’ much. Were they well-set? Probably not long enough. But there are worse places. I could move along, but some of the world’s finest saltwater marsh paddling is in such areas. So that experience has influenced my practice.
Curiously, if you have a Fortress in through a major thunderstorm, getting it back up is a project. They can bury 4-6 feet in minutes. Better than dragging… just barely.
You don’t break stuff here, you just ooze away….
Hi Drew,
No, not us, we have anchored several times at Solomons without trouble. On one occasion we had a full on fall storm, and again no problems.
The secret with the SPADE in soft mud is lots of chain while setting and a very gentle hand on the throttle. Treated this way it just keeps on digging deeper and deeper (like the Fortress) and I can still remember that pulling it after the blow just about stalled our massive Ideal windlass (as it often does). Said windlass can pull 3000 pounds and we are talking vertical rode angle here, so who knows how far down the anchor had gone into the mud. Clearly far enough to get into some good stuff.
I don’t know this for sure, but my theory is that the absence of a roll bar on the SPADE allows it to just keep going down until it finds good stuff. Supporting this view, I have dived on the SPADE after setting, and even in the the really hard sand of the Bahamas and Caicos islands the anchor had totally disappeared from view.
As far as the SPADE not holding well at Solomons, you may be thinking of the tests done by Fortress some years ago. But their protocol was deeply flawed for any other anchor than there own, and so not very meaningful. (They used a wire rode and a constant pull/speed from a huge hydraulic winch. And to make it worse, the pulling boat was using massive engines driven by a geostationary system, so at soon as an anchor tried to set, the system would kick in and yank the boat back on station. No way a SPADE, (or a Rocna) was going to get through the soup with that happening.
All that said, where the SPADE does struggle to set is in a very small anchorage with very soft mud. In this case we can’t get enough scope to get it through the soup, and on two occasions in the Chesapeake, we have had to move to a larger place. (If we had really wanted to stay, we would have used our Fortress with mud palms and the high angle option.)
Agree with points made, but from “helicopter” viewpoint surprised there wasn’t more discussion of shock load reduction. As you say, a good snubber is important – we always set a long snubber back to the midship cleat. Always because you never know for sure what’s going to happen with the weather. We also always set our V shaped fin delta riding sail. I suspect that jerks on the anchor from sailing back and forth are often more problematic that straight line pull holding issues. One time in Vliho Bay, Lefkas, Greece an unforecast afternoon storm with multi-directional gusts over 40 knots had many boats dragging their anchors. We were fine until another boat with no crew on it dragged down onto us. The other boat got caught alongside us, basically a raft up but we held both ourselves and the other boat until the other boat crew got back. So we were very happy with our combination of spade anchor, long snubber and riding sail. Who knows how much each element contributed to the good outcome, but I suspect in that situation all the elements were important.
Hi Bob,
I agree that shock loading and shearing are vital subjects. I did not go there in this piece because it is just one chapter in a complete online book on anchoring and I have found that things are made clearer by focusing on one important issue at a time. Otherwise we tend to end up with a bad case of TL,DR.
That said, we need to add more on just the subjects you mention (it’s on the list) and when we do I hope we will benefit from your experience, particularly with the riding sail.
Hi John,
This is really interesting and I don’t necessarily share your conclusions, though it is a very complex field. We design moorings for buoys, and though these use much larger chain (42mm) the calculations around chain length for a given depth are highly complex, and if inadequate can result in a 3.5t dump dragging in storm conditions. We use modelling software to determine the correct ratios, it is called Orcaflex. I’d like to give this more thought before commenting further.
Hi Dan,
I agree, it’s complicated, and, as I say in the post, I have definitely simplified it. That said, I think this level of simplification is fine for our purposes: getting and staying anchored. See my comment to Drew for more of my thinking on that: https://www.morganscloud.com/2018/12/10/anchor-chain-catenary-when-it-matters-and-when-it-doesnt/comment-page-1/#comment-274822
Also, while I kept things simple, I based a lot of what I wrote on Smith’s excellent article (see Further Reading) (no point in reinventing the wheel) and his is more nuanced as well as being based on yet another, and even more detailed study, including mathematical modelling, that I read prior to writing this.
Bottom line, to add all the underlying information would have resulted in an article three of four times longer that few would have read. And nor would they need to, given that delving that deep would not have any material effect on their anchoring success.
Hi John,
I continually get confused about G40 (G4) and G43. I can find them both listed, yet some describe them as the same. Above you refer to G40, but the first reference you give on chain grades in Further Reading only refers to G43. And there is potentially a gypsy issue if not identical.
Thanks
Hi Michael,
Yes, it’s complicated and confusing. G43 and G40 are the same grade and strength. That said, while I think that the link dimensions are the same for both across manufactures, I don’t know that for sure, so the best bet, if there is any doubt when buying chain, is to get a short length and check it on your windlass before buying a full rode—I have always done this.
Windage/vessel weight + rode weight/type + anchor weight/type + depth + scope + bottom topography/type = secure/successful anchoring, or a lack thereof. Coral hard pan with a few inches of sand, nothing works. Stony cobble, not so good. Sandy with thick grass, good luck. Anchoring, like much else on a boat, is more a matter of intuition/luck than analysis. Enjoyed your article on this endlessly debated subject, but there are so many variables that anchoring rules, analyses, and equations are rendered meaningless by real world situations.
Hi Reed,
I can certainly see how it can feel that way. In fact anchoring felt exactly like that (totally hit and miss) to me too up until 15 years ago when we got our first SPADE anchor. That was quite a small one, to use as a second anchor to the CQR we had a as a best bower. But even so, anchoring suddenly got a lot more predictable and reliable. A year later we got our 120 lb SPADE and ditched the CQR and things got better again. And we also started really thinking about out technique and other details covered in this online book.
Since then we must have anchored at least 1500 times in every substrate imaginable from the rocky kelp filled coves of Greenland to the loose soup of the Chesapeake Bay and on to the hard sand of the Bahamas. In all that time we have only failed to get set less than 20 times (tops), (including those detailed in the post) and have never dragged once set. So that is 98.6% setting success rate and a 100% anchoring security rate.
I’m not trying to be argumentative here, but just to point out there is good news: Anchoring problems can be solved with the right gear and a bit of, not difficult to learn, technique.
Hi Reed,
I had just finished the opening paragraph when John’s post popped up: and he said all I wished to say well.
So, in short, I will say I followed a similar path to his: first Spade in 2007 and anchoring became far less worrisome and then bumped up a size (35kg on a 40-foot boat) and continued to not have a problem as we moved into more challenging anchoring situations. I very much do not believe that the guidelines/suggestions of John (and the multitude of others who recognize the advances made in the last decade+ in anchoring techniques/equipment) are in any way rendered meaningless by real world situations: in fact, I believe they have been rendered meaningful and have been validated by all the real-world situations I have encountered (and heard about) this last decade and longer. I think I am close now to saying that for any cruiser who wanders widely and anchors frequently to not have a new generation anchor borders, for me, on a willful ignoring of the accumulated reported experience and presents an unnecessary danger to his vessel and crew and to other boats around. The new anchors are a safety jump in the ballpark of AIS and inflatable life vests and the like.
My best, Dick Stevenson, s/v Alchemy
Hi John,
I think that your conclusions are good. The points made in the comments about depth are also very valuable, when setting in deep water you can set on much shorter scope than when setting in shallow water. And like you, our setting technique has gotten much quicker and sloppier than it once was. It is probably worth noting that the graph was made with the snubber being a 3/4″X30′ piece of 3 strand nylon.
Your article got me thinking about moorings which have the same energy absorption problems as anchoring. I plugged in 50′ of 5/8″ chain (around here most harbors would require half the rode in 1/2″ and half in 3/4″ for a 40’er) and a 15’X1″ nylon pendant. The results were not good, energy absorption was less than half of the anchored example that you used. Even though the chain is about 2.5 times heavier per unit length than the graph in your post, the short length of chain meant that its energy absorption from catenary is pretty small (even at 500 lb load, it had only 4″ of give left from catenary, the 3/8″X200′ of anchor chain hits that point at 1500 lbs load, chain length scales nonlinearly to force). Also, the short length combined with the much stiffer construction means that chain stretch is not much of a contributor. For the sizing that I used, you end up with the vast majority of your energy absorption coming from that short nylon pendant unless you are in really deep water. To me, this highlights the need for the pendant to be as long as possible, changed regularly (we do 5 years with 5 months a year of usage but I haven’t done anything to prove whether this is too long or not), and out of suitable line (Novabraid double braid nylon is our choice for the portion before the chock). It also suggests that mooring in deeper water is beneficial. Think that we can talk Drew into looking at mooring specs as his next project?
Eric
Hi Eric,
Good to hear it all works for you.
And yes, as you say moorings can be a problem scope wise. One of the nice things about being in Nova Scotia is that there is still more room for moorings, even in really snug coves like ours, so we can get away with more scope.
Our storm mooring is in 18 feet of water at high springs and has 30′ of 1.5″ ground chain and 20′ of .75″ up chain, and then a 15 1.25″ Dacron single pennant. So a bit over 3:1 scope at high water. We have ridden out three cat 1 hurricanes on it, and I don’t remember any excessive shock loading, but then our longest fetch is only .75 miles, and we get no swell at all, only chop.
I agree, hopefully Drew will take a look at this for PS.
Hi John,
Not knowing the exact specs on either the chain or the line, I plugged in generic numbers for both and your mooring provides interesting results. Your heavy chain ends up having energy absorption from catenary that looks a lot like the 200′ of 3/8″ chain despite being about twice the weight underscoring just how important the length of chain out is in this calculation. The energy absorption due to chain stretch is quite low because the chain is short and is a very stiff cross section compared to the loads. Taking a generic 2.6% stretch at 20% load type of Dacron pendant, you end up not absorbing much energy there, it is actually below the chain catenary for much of the range that you highlighted. Using this stretch number, your pendant would only have stretched 2.7″ at 5000 lbs whereas an equivalent length of nylon would have stretched 12.1″, still not a lot of energy absorption (energy is in this case is simply the area under the force/distance curve). If the loads go much higher than the indicated range, then the picture is not particularly good as the chain catenary will be basically used up and there are not many other good energy absorbers.
I suspect that the reason your boat does so well is that it is inherently a well behaved boat. I believe that you have previously stated that it does not sail much at anchor which obviously is a big deal. Also, it is long enough that I suspect it does not pitch much in the chop that you get whereas a 25 footer might find its bow going up and down multiple feet. Interestingly, one form of energy absorption is vertical movement of the bow when the pendant pulls down on it.
Eric
Hi Eric,
That all agrees with what we have observed. Makes me wonder if I would be better off with Nylon, (We changed to Dacron some years ago because of the risk (perceived?) of heating and fatigue with nylon.)
Anyway, as you rightly point out, having a boat that is well behaved and not being in an area with much fetch or large waves trumps all of this stuff.
Hi John,
It is hard to argue with success. That said, if I had no knowledge of that success and were creating a mooring for your boat, I would have picked the nylon. Your fears of fatigue are unfortunately well founded and in my opinion not well understood by most in the sailing world where people want a single safety factor to apply everywhere. For nylon, ABYC uses a safety factor of 8 to encompass this and other losses of strength which seems very reasonable to me. An 8X safety factor on 1 1/4″ New England Ropes double braid nylon would be 6500 lbs, slightly more than ABYC’s permanent mooring recommendation for a 60’er. In addition to not taking fatigue into account, it is my belief that most don’t understand that pendants have finite lives. We generally replace based on a schedule which should account for UV degredation but we would also replace if we ever had a storm which put the system near its design point for a significant period of time. It is my belief that heat is a bit of a red herring. If we take the 15′ X 1 1/4″ nylon pendant cycling from 0-5000 lbs every 4 seconds, the energy absorbed is only 800W and much of this is returned to the rode which is not a lot for something that large in surface area and constantly getting wet. Where you do have problems is the rapid sawing action around the tight bends of chocks and this is the reason that I believe the nylon should not come on board but rather a piece of dyneema like a cyclone mooring pendant or similar. I also happen to be an advocate of 2 unequal length pendants but I dislike the approach of making them identical as my feeling is that once the first has failed, you have likely proved that its design was inadequate and it is time to shift the equation more towards pendant survival although that also means the loads will likely go up as shock absorption has decreased.
Just to really stir the pot, I compared the 3/8 chain in your graph to 5/16″ G70, a decision many people with 40-50′ boats would be faced with. The interesting thing is that the smaller G70 actually has slightly more incremental energy absorption up in the range you have highlighted. The energy absorption from catenary is lower as you would expect but the stretch is enough greater to more than make up for it once the load gets over ~1500 lbs. The reason for this is that the modulus of elasticity, engineers’ term for how much something stretches for a given stress level, has only small variation across all steels and heat treatments so since G70 chain with a smaller cross section operates at higher stress, it will stretch more at the same applied load. Of course, the snubber will still provide much better energy absorption than either chain option. The 3/8″ G40 chain will provided somewhat better damping due to its larger drag through the water but I am not sure how much effect this will actually have.
Your comment about Billings’ moorings is interesting. I know that at least some of the moorings in Burnt Coat have the same construction although that bottom is mud and that weird stringy weed as far as I know.
Eric
Hi Eric,
That’s interesting on the mooring. I will have to think about going back to Nylon particularly since that now we have the option of using Dyneema at the chocks and cleats I’m a lot more comfortable with Nylon for the rest, than I was. (I have seen way too many boats on the rocks with the remains of a Nylon bridle sawed through at the chocks.) So thanks very much for running the numbers.
Also, fascinating about the chain shock absorption. Really reinforces one of the most important lessons I have learned while running this site: a lot of truths in the real world are counterintuitive.
Eric,
I share your concern about the typical harbor mooring. Much more scope in the form of chain is needed generally (imo). Some gridded harbors have shortened up scope and increased weight to provide more moorings.
With the additional chain scope, an extra large mooring ball and adding extra and significant pendent length should help avoid shock loading on both the boat and the mooring, by utilizing the excess buoyancy of the ball to provide “give” between waves and wind surges. The extra pendent length provides an angle to utilize the ball’s buoyancy as the ball is pulled below the water.
I have not quantified the physics of this, but I believe it does work. It would be interesting if someone would provide the math.
I think the question is if this reduces the catenary too much (but for a mushroom that is 6′ in the muck that might not be as significant), because it is pretty clear to me that reduced shock will be a benefit (should also be confirmed mathematically).
I am surprised that a good anchor setup would be better than a good mooring setup due to the larger weights (helical piles excepted) used by most good moorings, but as you point out scope is a critical factor. I wonder if the newer bungy cord rodes used with helical piles will ever be adapted to anchoring and traditional mushroom mooring anchors.
All of this gear has consequences when you consider barnacles and weed growth which can cut line (and bungy) and affect strength.
Elastic Moorings. Google “StormSoft” and “Florida” and you will find that they got some real lessons during the 2017-18 season. The storm that crossed the Keys plowed right over one field. At this point it seems they are the real deal. The boats were attached to 1-inch nylon pendants (15′ I think) and less than 1% of those failed. What DID fail was the attachment to the boat. Rigging the pendant to the boat is a good article topic.
Based on this experience, and experiences with the system in New England, my feeling is that this is the new state-of-art.
Hi Drew,
I suspect that you are right that something like the StormSoft system will eventually be considered the gold standard. 10 years ago when it was time to refresh our mooring for a different sized boat, I looked into what the options were and at that time I believe it was either the Hazelett or the boatmoorings.com options. I called both and tried to get more info and eventually decided that I did not have the confidence to go that route. With Hazelett, I did not like the answers I was getting on how to deal with our 10 foot tides and felt that they were putting my Dor-Mor anchor at unreasonably short scopes and I also did not like the stainless hardware. With both options, I felt that they failed to provide any real analysis or testing to back up their designs. They provided a small list of areas installed and it did not appear that those areas had been challenged by really bad weather so I felt like I was being a guinea pig for a design that may or may not have had sufficient analysis and testing put into it. I was unaware of the test that the StormSoft system got in Florida but it sounds like the test I was looking for may finally have happened.
All that said, I really like the concept and I don’t see any reason that it can’t be implemented well. Mooring chain is not great for shock absorption, it is quite expensive and does not last long. Before the mooring requirements that came as a result of Hurricane Bob, all 3 moorings that our family has used a nylon top line sized to never touch the bottom and then very heavy bottom chain. The issue with this setup was of course growth but otherwise they worked great.
Eric
Hi Eric and Drew,
That all makes sense to me, particularly in areas with crowded mooring fields resulting in short scopes.
One thing to add to the mix. Some years ago my friends at Billings Deisel changed all of their moorings over to massive (1-1/2″ if memory serves) 3 strand rope from the buoy to the ground chain, which is also massive (2″ I think). Their mooring field is quite exposed (Eric will know it) and this has proved to be a great change. That said, shock absorption was not their goal, but rather dealing with the very quick wastage of the up chain that they were getting before. They tell me that the new nylon moorings are lasting 5 years at least and showing no signs of chafe, even though the bottom is rocky there.
Anyway, this does show that we don’t necessarily need chain for durability.
Hi John, Eric, Stein and all the engineering minded types that frequent this site:
Here is an alternative concept to conventional chain anchor systems for you to analyze/critique;
1- Given that the primary reason for using all chain rode is abrasion resistance on the seabed.
2- And given that the shock absorption capabilities of the catenary effect decrease radically once you really load up the system.
3- And given that one of the major contributors of degraded sailing performance on cruising boats is loading the bow down with hundreds of pounds of chain:
Do modern materials offer a better approach?
A— Up size the anchor by two full sizes to increase its unassisted setting and holding capability.
B— Replace the first 30′ chain leader with oversize Dynema sourced from non-yachty commercial sources. — well proven as abrasion resistant trawl lines for offshore fishing
C— Splice in the remaining (250′–600′) rode from smaller light weight Dynema.
D—Design a custom 30′ snubber using the StormSoft principle to provide engineered elasticity.
E— Replace the conventional chain windlass with an electric self tailing winch.
F– Store the line on a portable drum or flake in a figure 8.
I can think of several disadvantages. Bring on yours!
1- How does one design a removable device to attach the snubber to a small diameter and very slippery anchor line?
Hi Richard,
I think that there is promise in your idea but there are a few things to be worked out. The potential space, weight and cost savings are definitely intriguing.
As you say, attaching a snubber would be a real challenge and the snubber is absolutely critical. One idea that I know of is to have splices every so often that you could hook into, Of course, this would be a challenge with many winches. I suppose you could also make the first 50′ a piece of double braid nylon inside a very good chafe protector like the ones they use for diver umbilicals or the dyneema ones used on large ships. Then, you would never use a snubber and would just have to use a million turns on a cleat. I also like this idea for the safety that is presents in not overloading the system as otherwise, you shock loads could be enormous if the system loads up during setting or retrieval.
For people who anchor long term, growth could be a real issue. Any line, even with a tight cover, will have some issues with growth but if single braid were used, you will get large mussels inside the braid after a little while. Maybe you need 2 anchor rodes and switch each week? Also, I am not sure how dyneema would hold up in truly tough bottoms like some of the sharp corals, maybe someone knows?
Getting it to sink certainly seems doable but could be annoying. I have heard people mention putting wire through the center but don’t know anything more than that.
As John mentioned, the place where catenary really helps, is during initial setting so something would need to be done about that as you wouldn’t want to always use 7:1 when setting regardless of depth. Maybe a short length of pretty heavy chain. In truth, this could be really short and just really heavy, unlike shock absorption, you just want to take out the vertical force so it doesn’t need to be done over a long length of chain.
None of this stuff seems like a show stopper to me. I would love for someone to try it and report back. I am not dying to be the guinea pig, our ground tackle is working fine and the current chain is only 5 years old so I am not in the mode of replacing anything. If I remember right, we had a member a while ago asking about how to deal with his reel winch style windlass and I suggested that this was one possible solution but I don’t know if they ever did it. For that matter, a reel winch might be the best windlass solution with your idea.
Eric
Hi Richard,
One more thought having had a bit more time to think about it. If you did put your spring (nylon or elastic) on the anchor side of most of the dyneema, then a drogue such as Colin runs would be an excellent damper as it would be on the correct side of the spring. Unfortunately, you would once again have the issues of how to attach it. If you were willing to give up some performance for yawing, you could actually put it at the connection of the spring and the dyneema rode and it would be quite effective at damping longitudinal surge at least.
This actually applies to more than just Richard’s suggestion. If we ignore all of the usability aspects and simply wanted the best performance with a conventional chain/snubber setup, you would probably get the best performance by putting the snubber from chain to chain somewhere underwater and then have a small drogue on the boat side of that with only the chain coming aboard.
Eric
Hi Eric,
A couple more thoughts– mostly on the disadvantage side:
1- Your point about mussel growth– even inside the line— may be the deal breaker.
2- My concept was to use 5/8 or 3/4 DUX as the initial leader to provide the maximum abrasion resistance where it is most likely. That precludes putting the snubber at the anchor end.
3- It would be easy to splice in a soft eye for attachment of a “Colin Drogue” at that point or further up.
4- Using a self tailing winch rather than a windlass would save money but preclude using a chain leader.
5- I suspect replacing a 60# anchor with an 85# would aid initial setting as much as adding 25# of chain leader. Depends upon how strong the tendency of the line to float is.
6- Using a bi-component engineered snubber on the SoftSet principle allows one to to fine tune it to the boat weight and windage far better than just adding a length of stretchy line.
7- re the snubber attachment problem: Perhaps design a 2-3X long line clutch that could be clamped on and removed at any point?
8- The tendency for the line to float would be a killer in any crowded anchorage or during wind and tide shifts. Deal breaker #2 unless there is a smart solution.
Hi Richard,
Yeah, growth might be the deal breaker. Maybe this solution is really for people pushing the performance envelope and not planning to be at anchor long term. It would seem that the buoyancy issue is solvable to me.
I have no experience with them but wonder whether dyneema based chafe gear would be compatible with something that has signficant stretch? For example, could you put something along the lines of Samson DC Moor-Gard (https://www.samsonrope.com/chafe-protection/dc-moor-gard-s/) around a piece of double braid nylon to get the toughness you are looking for in point 2 and the snubber in the easiest to handle place? If they are compatible, that could be really interesting for replacing top chain on permanent moorings too.
Regarding point 5, the trade-off is interesting. If we assume that the downward force on the end of the shank from the anchor’s weight is about 25% (my guess), then the difference between an 85# and 60# anchor shank end weight would only be about 6 lbs. So strictly from the point of keeping the shank down, the chain would be better. However, there is no question that bigger anchors have an advantage in tip pressure and I don’t know whether this would overcome the tendency to lift the shank. If we assume 5:1 scope and 25% shank tip weight, then an 85 lb anchor would start to lift the shank at 106 lbs of rode tension with no chain, barely enough force to get the anchor moving so it would seem that some weight would be useful if you want to avoid extreme scope. On a skiff, we have successfully used danforths with no chain and 4:1 type scopes but I have no experience at larger sizes and modern anchors,.
Your point 6 got me looking at elastic moorings again and it was interesting. I posted what I found elsewhere but I see some promise and also some mildly scary marketing. From an anchoring standpoint, the systems that seem better to me become quite large.
Eric
I had a few minutes so did a bit more digging on these elastic mooring systems and not everything that I found was encouraging. The good news is that boatmoorings.com and Hazelett both publish force/deflection curves. I couldn’t quickly find any information on Stormsoft (are they still in business?) and couldn’t find a curve for Seaflex.
I started by looking at energy and immediately was alarmed by the Eco Mooring system from boatmoorings.com. They tout stretch from 13-19′ but the working range is really more like 17.5-18.5′. At 16′, you are only at 10lbs which means it is basically useless below that point. If we look at it up to 5000 lbs, its total energy capacity is about equivalent to the stretch of 200′ of 3/8″ chain and less than the catenary of that chain, not good. From an incremental standpoint, it is similar to the total combined for the chain, not nothing but not a lot. If you look at their video of the Big E storm pendant, you can see this in action, it is a pretty calm day and it is stretching through much of its range at low loads. My suspicion is that the elastic inside is far too weak and while it provides a nice cushy ride in calm conditions, the outer rope layer takes over when conditions get boisterous. To me, claiming large amounts of energy storage capability is similar to when people claim that the tethers with bungees inside them will cushion a hard fall. This solution might be enough for very limited fetch areas but is not what I would consider an elastic mooring. I do think that having a non-linear force deflection curve could be advantageous but not in the way done in this system.
Hazelett was much more promising to me. However, I had questions about their sizing. Taking 30% of ABYC from Drew which he says is the wind load for a 40′ boat gives 1080 lbs for 60 knots (technically he says 25-30% I believe). Hazelett says that you should not operate normally above 30% stretch and brief elongation of 50% is okay with elongation beyond 50% only acceptable for brief excursions during extreme weather. Using 30% as the design point, you would end up at ~375 lbs per element This would mean you need 3 elements for a 40′ boat in 60 knots. It was tricky to find their sizing but what I could find suggested that this 40′ boat should use only 2 which means that it is not even sized for 60 knots, a not unreasonable occurrence in many places. Hazelett, like Seaflex, can incorporate a load limiting line which unfortunately takes out most of your spring and suddenly the loads will go up a lot just when you don’t want that (at least 1 manufacturer actually advertises how great spectra is for this which would put a real knee if the force/deflection curve). That said, the performance of the elastic looks excellent below these values especially if you use one of the longer lengths and I like the look of the construction of the elements better than some others. It has the best spring properties of any of the options we have discussed including a 30′ snubber by a fair margin (dampers are different and I would need to think on that). It seems promising but would need to have them convince me that they are sizing for appropriate conditions.
I continue to be nervous about the materials used also. Seaflex specifically advertises stainless while Hazelett has gone more towards galvanized but uses stranded galvanized wire which I am uncomfortable with as once the galvanizing wears through, it looses strength super quickly.
Moorings is an area where I see large room for improvement and it may be that Hazelett or Seaflex has a good system but from the publicly available information, I am not yet convinced to change over from a “conventional” mooring. For a “conventional” mooring in deeper areas or areas with really smooth bottoms, I could see having a very heavy piece of nylon replacing the upper chain being superior.
Eric
Good information! I had read various differing accounts in the past and this helps explain the underlying mechanisms.
I do have a question. I’m using a rope rode with a boat length of chain (currently I am just coastal cruising in fairly the protected waters of Mahone Bay and rarely out in nasty weather because we not that far from home base). Would you recommend using a kellet on the chain to improve the anchor angle for setting? Or just using more rode to get the set – then drawing some back in?
I know I’ve had a few times where I had problems getting a good set – typically when I was trying to set my Rocna on a sloped bottom. I assumed at the time that I was pulling the anchor up out of the bottom as the angle of pull from my rode was creating too much of an angle relative to the bottom.
Mark
Hi Mark,
Interesting question. I really don’t like kellets. Two reasons.
First off they must be very heavy to do anything useful for ultimate holding (same reason as chain).
And second, retrieving them when it’s blowing can be really dangerous. (As the rode pulls tight in the gusts they fly around in some really scary ways.)
That said, at least in theory, a kellet might help setting on short scope, but I think the disadvantages outweigh that. Better to just use more rode to get set, and then shorten up, as you say. One caveat, it’s important to test the set with the engine after shortening up.
Another option would be to do as we do and carry a Fortress since it does well on short scope and in soft mud. That is as long as you have the mud palms on. (I tried it without in Scott Cove, and it was useless.)
For all chain, as John pointed out, more chain is always the better choice. At most, the kellet weighs as much as 20-30 feet of chain, so just use more chain. Even with rope, the kellet will lift before it helps with holding, and to some extent, setting. Better to use more scope.
But all rope rode has two other problems a kellet does help with; rode fouling the keel or rudder (which can cause it to cut–I’ve seen this), and swinging differently from boats using chain. The problem, of course, is that dealing with a kellet is a big pain. So I’ve been trying something different; a small coil of chain.
I’ve taken about 15 feet of 1/4-inch chain (for 24-foot trimaran–scale up as needed), doubled it twice, and attached it to the rode with a soft shackle through the links and prussik loop around the rope. This can be recovered over the bow roller and even left on the rode in the locker, with practically no handling problems. With it, I swing like boats on all chain. I’ve taken to just leaving it on the rode, it is so easy.
Something to try. You can probably get some old chain from the dumpster, since neither size or strength matter, only getting the weight right. It’s not going to make rope behave like all-chain, but it may help. Experiment.
I should mention that I’ve taken to using much less chain than other folks, in part to allow me to expereiment with chafe guards for rope. But that is a different subject.
Hi Drew,
Interesting idea, and I can certainly see benefit. That said, I have to caution, particularly those with larger boats and therefore more chain in the weight, that retrieving any sort of weight attached to the rode can be a real problem, and potentially dangerous, once the wind gets up: As the boat surges back and forth the weight will be thrown around making getting it under control and back on deck a real problem.
Bottom line, I just don’t like to see these kinds of added complications in anchoring since we just never know if something will happen that requires us to move in a hurry, and in that case we need to be able to get the anchor aboard quickly and without messing with added gear
Agreed completely. In my mind, boats over about 35 feet will probably have all-chain, snubbers, and a windlass, as I did on my last boat. What I offered was intended as a small boat solution intended to solve two specific problems (wandering and keel fouling). I don’t know the nature of Mark’s boat.
It also helps that I’m not really talking about a big coil per se, just 4 lengths. This comes up much like chain. A big coil would be a mess. However, all things considered, I’d just leave it off if I was expecting a really big wind or a lot of waves. Like any kellet, more bother and little benefit.
It’s a smaller boat trick.
This discussion has had me thinking over the last several days.
I understand that the chain offers very little benefit with regards to caternary – that’s fine. Plus I can see how a typical kellet is also counter productive.
But what about the setting benefits? John you specifically note how the lighter chain has forced you to be more subtle with your anchor setting techniques — not being as aggressive backing down on the anchor and starting with a longer scope. What happens in a wind shift or a tidal reversal where you don’t control the speed? I imagine most times the wind shift would be somewhat gradual and allow the anchor to reset under gradually increasing pressure, but not always.
If an anchor needs “special care” to get a solid set is that not in and of itself a safety issue? Is it worth adding heavier chain to get that more trustworthy set? Or in my case maybe a longer/heavier length of initial chain that will help give the anchor a better initial setting angle?
Of course – leaving out a longer scope is another option – but not always feasible.
Mark
Hi Mark,
Sure there are tradeoffs. But let’s not overthink this. The setting problems we had with lighter chain only occurred 3-4 times out of at least 50 sets, and were pretty much cured by me being a little less aggressive with the throttle. Point being that there is no “special care” here. Rather more yours truly getting lazy and slap happy with the heavier chain.
Also, heavier chain will not, at least the way I see it, give you a more “trustworthy set” since that’s ultimate holding.
Does that mean that there will never be a time where I will wish that I stuck with heavier chain? Beats me. But then again, how many times will I bless having more chain and less weight in the bow? I’m guessing that latter beats the former by an order of magnitude, at least for me with my interest in places with very deep anchorages.
And let’s not forget that a heavier anchor will always beat heavier chain on both setting and ultimate holding. So if you have weight to spare, getting a bigger anchor is always the best use of that weight.
All that said, for those that are concerned, as I said in the post, G40 is probably the sweet spot.
Some boats store the chain midships in the bilge where the weight is a benefit, rather than higher in the bow where it harms sailing performance. Does low mid-ship chain storage change the recommendation?
ps. Looking forward to the article on shorefasts.
Hi Paul,
Good question. An amidships storage certainly means that weight is less of an issue. But if it were me I would use that benefit to carry more chain, not make the chain heavier. My thinking being that, as Eric’s analysis shows, even with massive mooring ground chain, the spring benefit from catenary is small, so going up one or two sizes on chain to get more weight is really not doing anything useful for us.
What a great and informative thread this is. I can’t express how I am benefitting from these observations and experiences. I particularly find the switch in throttle practices when backing down to be very useful, as the “findings” with lighter chain suggested a different mechanism of action was at work.
I have switched from a 45 lb/20 kg CQR with a 33 lb./15 kg Bruce as a secondary to a 66 lb./30 kg SPADE as a primary, with a 21 lb./10 kg Fortress as a secondary and a Fortress the next size down as a stern anchor. This is for a 15-tonne steel pilothouse cutter of 12 metre/42 feet LOA. I anticipate going to 250 feet/80 metres of 3/8″/10 mm G43 before we leave for Nova Scotia on our shakedown cruise next summer. My only comment here is that I’ve found the Fortress buries itself very aggressively in certain sandy/silty conditions with a large chain leader on a 3/4″/8 mm nylon rode, to the point where it is, in easy weather, the go-to for short stops. In this sense, it has an opposing action to the SPADE, relying as it does on fluke area rather than tip weight to bury effectively. So I am finding confirmation that one’s secondary anchor can be of benefit if it works in an opposing fashion to one’s main anchor. Our real test will be in tidal waters with current against wind, I think, when I’ll want to experiment with dampening as we have more windage than most.
Something that I haven’t read in this string is the poor ability of higher tensile chains to hold galvanizing. A few years back we switched to G40 chain and after 4 years of 6 months per year use it is so rusty as to need replacement. This despite being rinsed with fresh water before storage. Other cruisers we have spoken with have had the same experience.
On another subject I have to put in a good word for our 30 kg. (genuine) Bruce anchor which has served us very well for 30 years from the Eastern Med to the Western Pacific. It sets reliably on short scope and the only bottom that it really does not like is thick eel grass. Our boat is a 24000lbs/45′ cutter.
This year we tried using 11mm dynamic climbing line as our anchor spring and were impressed with it. How long it will last I cannot say but it shows no obvious wear after 6 months. Having a boat that hunts fairly aggressively at anchor we tried Collin’s drogue idea and found that it definitely reduced our shearing around. I am in the process of converting an old storm staysail into a backstay riding sail and will try it out next year.
Hi Rupert,
Who made the G40 chain you had galvanizing problems with? I ask, because, like Dick, I have had good experience with Acco chain and so I suspect that you suffered a manufacturing problem, not something that’s intrinsic to high test chain.
As to the Bruce, many of those who have ’em, love ’em. And there is no question that they are very good on short scope, I think. That said there is also compelling evidence, both from testing and real world experience, that the Bruce has much lower ultimate holding than an equivalent sized modern anchor and a much greater tendency to drag very quickly once it does start dragging.
Good to hear that Colin’s idea worked for you and I will be interested to hear about your experience with a riding sail.
Hi Rupert,
I am sorry for your experience with G40 chain.
Perhaps all G40 is not alike. I don’t know, but I am continually amazed at the longevity of my ACCO G40 which is close to 20 years now and has one re-galvanizing in Turkey in 2010. We put a caliper on the most depleted looking links and determine that we are good to go for another season. We have anchored a lot on this chain and it gets little special treatment: rinsing when we can, turn end for end, good ventilation in the well.
On the other hand, I could never make my Bruce anchor work for me.
Go figure.
My best, Dick Stevenson, s/v Alchemy
John and Dick,
Our G40 chain came from ACCO via Port Supply so I can’t account for the difference in performance. Anecdotally, however, others I spoken with have had the same issue. I see that in their catalogue Fisheries Supply note that “high test….is slightly less resistant to corrosion” and that they recommend that it be rinsed in fresh water and stored dry!
Dick, I’m sorry that you could not get along with your Bruce. I think I read that the Spade you have is a 35kg, a goodly size for you boat. Was your Bruce the same weight?
Hi Rupert,
On the chain, that’s interesting and obviously a concern since we recommend Acco G43. I went online and could not find that warning in the fisheries supply catalog for the galvanized chain: https://www.fisheriessupply.com/martyr-grade-43-high-test-windlass-chain
Could it be that the warning is for the non-galvanized, which is what fishing boats generally use?
I did find this: https://shop.sailboatowners.com/prod.php?67/Grade+43+High+Test+Anchor+Chain
But no source is cited and I wonder if they might be confused with non-galvanized.
All that said, I can see that once the galvanized has rubbed off, maybe the high test chain alloy would be more susceptible to rust. But even so our experience with our old G43 where an accurate dial calliper showed no measurable wastage even in places near the anchor where the chain was very rusty and had been so for years indicates that there is no strength problem here.
Sorry to be so pedantic, but I’m always concerned to make sure that these kinds of things are indeed true and not just legends that have grown up with repetition. For example, for years cruisers all agreed (me too) that high test was “brittle” but that turned out not to be true at all.
https://www.morganscloud.com/2011/05/11/things-to-know-about-anchor-chain/
Hi Rupert,
That is weird that your chain went so fast. My ACCO G40 has had many seasons where it only gets a couple of fresh water rinses and is always piled salt-wet in the locker where it does dry, but I am sure not quickly. It is not nice to think that ACCO may vary in their QC.
My boat came with 2 bow rollers and the PO sported a 45 lb CQR on one roller and a 45 lb Bruce on the other, a common cruising pair back when. I was pleased and thought I had it covered: when the CQR did not work, I could use the Bruce. Generally, when the CQR did not work, neither did the Bruce, but, again generally, the CQR worked more consistently than the Bruce, so I put it in the locker as a spare and went to a 65 lb CQR as the bower. This was better, but there were still too many times when I could not get the CQR to set in areas from Central America to the Med. I bought my 30 kg Spade in 2007 and was immediately very pleased at what a difference it made. It got really rusty, so Spade spotted me a new anchor in 2014 and I paid the difference to upgrade to a 35kg as I was looking at anchoring situations in even more marginal locations. It was a good move. The rusty 30 kg is broken apart in storage and the CQR and Bruce found new homes long ago. I believe the 35 kg Spade with 5/16” G40 to hit the sweet spot for my cruising purposes.
It is my observation that Bruce anchors improve more quickly with weight than others so the bigger Bruce anchors are more functional per weight.
My best, Dick Stevenson, s/v Alchemy
Hi Dick,
That makes sense. It’s pretty well documented in both testing and the real world that the Bruce is particularly weak in smaller sizes but things get better as they get larger. The few people I know that still use the Bruce have massive ones. That said, I have never yet met, or even heard, of anyone who regrets changing to a SPADE, or other modern pattern anchor, from a CQR of Bruce.
John,
The quote regarding G40 chain comes from the Fisheries catalogue (not sure of the date, it has a photo of Mukilteo Lighthouse on the cover), page 41, “Acco – High Test, Grade 40, Galvanized Anchor Chain”
I see, too, that on the next page under BBB chain they say that “silicon rich steel promotes better bonding of the zinc coating to the iron”. Better than what is not stated but it does beg the question. Perhaps some materials scientist in the readership could weigh in on this?
Dick, I’m interested that you use 5/16″ chain on a vessel of a similar size to ours. As we have to replace ours (in Tahiti of all places to be obliged to buy chain! Sources are either France or NZ) I should consider buying High Test of that dimension. I wonder if you originally had 3/8″ and if so did you notice any difference, beyond the obvious, in going to the smaller size? Did the boat sheer around more, for instance, or surge back and forth more noticeably?
Hi Rupert,
Yes, I use 5/16s and it has been on the boat since I bought it so I have no comparison. I would buy the same again. In an article in the pipeline, I argue that one should buy chain based on strength considerations over weight. It covers much the same territory that John’s recent article on catenary covers, but I would be happy to send you a copy if you contact me off-site at (alchemy128(at)gmail.com).
I do not know availability, but, if ACCO is not available or you wish to swap brands, I have heard excellent reports of Maggi Aqua G4 (Italy) which can be had in 5/16ths as well as their standard metric sizes.
My best, Dick Stevenson, s/v Alchemy
Hi Rupert,
That sounds convincing. As you say it would be interesting to hear from someone who understands the science…Drew?
I’ve never read a study of G43 vs. G30 and galvanized durability that I felt was properly controlled; use and galvanizing practices are huge variables.
What I do know is that when I have ordered structural galvanized steel for refinery projects, it is designated G30, G40, G60, or G90, for 0.3 ounces through 0.9 ounces of zinc per square foot respectively. This “G” rating has no relationship, at all, to chain strength ratings. Curiously, chain manufacturers do not report the coating thickness in a similar way. I’ve always felt this is the heart of the problem; some chains are simply not well coated, for a variety of reasons.
In my experience, G30 and G43 chain seem to corrode in a similar time period, but too many variables to say. However, I would bet lunch that steel alloy is far down the list of variables.
Hi Drew,
That makes a lot of sense. Talking of “a variety of reasons” I seem to remember that during my chat with an engineer at Acco he said that the biggest part of getting galvanizing to bond properly is the preparation bath process.
Anyway,I will not be taking the other side of that bet.
Dick,
Thanks for the input.
I don’t think any Italian chain is brought into Tahiti. The choices are limited to FOB (a well known French brand) and chain from NZ — not sure of the manufacturer.
https://chainsropesandanchors.co.nz/ (New Zealand) supply Maggi chain and Spade anchors.
Hi Guys,
I was reading through the posts and was wondering if anyone has tried ‘backing the bower’….???
We have been in some big winds at anchor from time to time and find this old sailor’s technique has worked very well. It essentially keeps the short piece of chain attaching the second (or backing anchor) to the bower at a much reduced angle .
Piece of mind at night or when going to shore.
Snubbers are essential!
Have always let out an additional 7-10 meters of chain to keep my chain hook engaged and never considered the ‘damping effect’ this extra weight and length provided. Good to know others have enjoyed similar success.
Merry Christmas/Happy Holidays everyone!!
Hi Devon,
I have written about the use of two anchors, including “backing the bower” in this chapter: https://www.morganscloud.com/2012/12/14/one-anchor-or-two/
Hi John,
When you say that you wait for the breeze to straighten the boat out before backing down, I presume you’re using power/rudder to prevent the bow from wandering too far afield while drifting back? Or you do let the bow swing out?
I’m pondering what could go wrong if I let my bow wander far off the wind as I drift back back while anchoring single-handedly.
I was, of course, taught to keep the bow to wind when anchoring. Sailing single-handedly, with no windlass controls at the helm (yet), I anchor from the bow. I minimize drifting off the wind with periodic “stopping points,” allowing chain tension to straighten the boat a number of times before I reach full scope and let the boat settle. My SPADE hasn’t dragged under the practice, but I now see the benefit of paying out more scope before allowing initial tension on the anchor chain; however, that would require allowing the bow to swing out, probably perpendicular to the wind, while drifting back.
Windlass controls at the helm is the easy answer, and that’s on the project list. But I’d still find it helpful to hear what others think about allowing the bow to swing far off the wind while paying out scope (aside from spectators thinking I’ve hit the post-sailing libations a bit early). I wouldn’t want to do it when sailing onto anchor. It’ll also be a factor the day my electric windlass fails. But otherwise?
Regards,
Ed Sitver, s/v Ventus
Hi Ed,
We really don’t worry if the bow drifts off. In fact most of the time we end up beam on to the wind by the time the rode pulls tight. Does not seem to be a problem, and I’m not sure it’s even possible to keep the bow up in the wind with power and rudder.
And further, we don’t in any way check the boat with the rode until we have the full scope out. I just don’t like to put any load on the anchor until we have the desired rode angle.
As to windlass controles at the helm, we prefer to run the chain by releasing the clutch since that reduces the change of dragging the anchor back and getting loaded with mud before it has enough scope to truly set: https://www.morganscloud.com/2011/08/07/boat-windlass-requirements/
Backing the Bower. The modern term is in-line tandem. Every anchor manufacture other than Rocna will tell you it does not work. Spade is emphatic about this. Oil field anchors use 2 rodes or at least a link that ties them BEFORE the shackle. I’ve done a lot of testing, and it nearly always reduced the actual holding power. I have an open chaleng to anyone who can show me a picture of both anchors actually set after a 20 degree change in wind direction. Over 5 years, no one has challenged me on it. The Rocna photos were very carefully staged (there was no direction change, the anchors are actually on the verge of unsetting, and they certainly are not deep). I’m not all negative. I’d like to see how it works. But In many dozens of real-world tests, if you dive on the anchor after a minor shift you will find the bower on its side and the smaller backing anchor is all that is holding. The bower is prevented from resetting by the back tension of the backing anchor, which completely changes the bower’s geometry.
The one exception is shingle and other impenetrably bottoms, where you rely on friction and marginal hooking. Moving somewhere else is a better plan.
There are cases for 2 anchors, but as John has eluded, they are specialty situations and they are not rigged in-line.
Letting the bow fall off. I’ve played with it both ways, since on my cruising cat it was easy to control (twin engines). But it makes no difference at all, since the initial set is light. In fact, the tendency to drift beam-one slows the process, which is generally good (I could drift straight back faster than I would like to set the anchor).
Hi Drew,
Good analysis and I appreciate your referring to other authorities such as anchor manufacturers and tests done. It is always nice to hear what others think and have done.
In pre-Spade times, I was preparing for a hurricane while wandering around the Chesapeake and we picked a spot to weather whatever was coming. We could not get our then CQR (and later failed with our similarly sized Bruce) to stick in the impressive silt over hard clay (I would guess). I some desperation, I hung our Fortress off the back of our CQR and found a good stick which held in what turned out to be a tropical storm.
I also might consider in-line tandem anchors were I clear that the winds were to be primarily from one direction as sometimes occurs in hurricanes depending on the quadrant. Then again, I may not, as the equipment I am using now is so far superior to what was available 20 years ago. Especially after your reporting that as little as a 20-degree wind shift might compromise the setting of the anchors.
At some point anchoring for a big blow starts to approach establishing a mooring, especially if you are not planning on staying aboard.
My best, Dick Stevenson, s/v Alchemy
Hi Dick,
I’m with Drew on this.
And I’m near certain that the only reason that tandem worked for you in the case above is that you had changed to the Fortress. The CQR was just acting as a kellet.
As you know, CQR anchors pretty much always have to drag back quite a ways to set, whereas the Fortress tends to set with little or no dragging. Given that, there is no way, at least in my mind, that the CQR was set.
Also, if we want to discuss this further, it would be better done on this chapter: https://www.morganscloud.com/2012/12/14/one-anchor-or-two/
That way everyone’s wisdom will be where people interested in two anchor options will benefit.
Hi John,
Now that you mention it, I suspect you are right that the CQR never set. I am (now doubly) glad the system moderated to a TS.
It is impressive how much of a head-set change has taken place for me: I remember an important consideration on choosing our anchoring spot was to have soft-ish spots to blow onto if/when we dragged. Sort-of like nowadays, on road trips, I almost do not worry about flat tires as I used to.
Nothing further to add, but I will keep in mind to go to the other chapter.
My best, Dick
Regarding dampening. We have an all chain rode and used to use a rubber snubber. We yawed a lot at anchor due to recoil as described by Eric Klem. Some years ago I read a white paper about the energy absorption of plait rope and it’s virtues for being able to absorb a lot of energy w/o a lot of stretch and subsequent recoil.
5 years ago we switched to using an 8 plait snubber (or it might be 12 plait, I’ll have to look next time) of 30′ in length (boat is 41′) and it solved our recoil problem . We’ve experienced about 20 to 25 kts of wind at anchor with subsequent sea state and the chain was tight (maybe not bar tight?) but the snubber seemed to provide reasonable shock absorption.
Comments about weakness in this system are welcome!
Hi Frank,
Thanks for the link. Interesting paper. That said, I think that it’s a bit misleading for Yale to claim that the rope actually “absorbs energy”. As Eric explains above, to actually get rid of energy (damping) said energy must be converted to heat. (As Newton figured out, energy can’t just go away.) That might be happening a bit with Brait, but I doubt that it’s as significant amount of the energy as that first absorbed by the rope in elongation and then given back when the load comes of (spring).
My guess is that the rope works better than the rubber snubber because it gives the energy back more slowly, not because it actually gets rid of more energy.
Eric?
Hi Frank and John,
I had not seen that whitepaper before. At first while reading it I thought that they were simply being sloppy with their language but as I read further, I decided that it was deceiving whether in an intentional way or not. I find it unfortunate as I have generally liked Yale products and prior to going to our current setup, used to recommend their mooring pendants to people.
It is very easy to be sloppy with language and is something that I am often guilty of too. Calling it energy absorption potentially makes one think that the energy has been converted and removed from the system (thinking about this makes me not want to use the term shock absorption anymore which I used to use a lot). More accurately, most of the energy is being stored as potential energy which will then be returned to the system while a small portion has gone to heat which is not recoverable into the system. In a sense this is energy absorption but the key point is that it can then be returned to the system which is the behavior of a spring. I saw no mention of damping in their article, only of the spring. They actually take a dig at 3 strand nylon for internal heating and if they have less of it, then they would provide less damping too. Another place that bothers me where they are sloppy is that they provide recommendations for line and chain sizing without any mention of what conditions that is for. I am guessing that this is for a “lunch hook” as they recommend 1/4″ chain (what grade?) and 1/2″ brait for our 36′ boat, something that I believe is quite light. They also use a 5:1 safety factor for their WLL and have no discussion of fatigue properties which are known to be critical for nylon and it would be useful to know how construction affects this.
The numbers that I find troubling are in the 2 addendums. In the graph where they compare 3 strand and brait, they claim an area where brait is capable of extra energy absorption. They had just previously said that you couldn’t use that part of the curve for 3 strand so why are they suddenly claiming superior energy absorption based on parts of the curve they said you should never operate in? I dislike that they have normalized the data as energy is based on absolute numbers so you can’t compare areas unless the Y-axis is equivalent which their numbers suggest they think isn’t. Looking at addendum 2, they are claiming higher breaking strength numbers for brait than for “premium” 3 strand (7875 lbs vs 5750 lbs) but looking up New England Ropes 3 strand nylon which has been out for quite a while and is very popular, it is rated at 7500 lbs a greater than 30% difference.
All of that said, if we assume that the stress strain curve is linear for the portion that we are discussing, if you have 2 equal strength lines with equal WLL and 1 line stretches more, it will be able to store more potential energy which will lower peak loads provided there is no issue with dynamics. As to how this affects its use as a snubber, unfortunately I don’t think that we have enough info from the paper to know. Frank’s experience is certainly interesting and promising but we would need to know exactly what the snubber was before and after and if any other changes were made.
Eric
Exactly. I wrote just about the same things, but then deleted it before posting because it felt accusatory towards Yale. But now I feel OK about it. One way or the other, it is exaggerated.
The other thing that bothers me is chafe. I’ve tested plaited rope against 3-strand over rough (cinder block) surfaces using a heavily weighted pendelum (seemed more like yawing at anchor than the standard length-wise tests). 3-strand wears better, and chafe is the most common cause of failure.
That said, non-rotational behavior is very important on single line snubbers. The cover photo on my anchoring book shows a snubber with the chain over it, the result of rotation under load. It was a friend’s boat, so I know the whole story. The snubber was ruined in a single trade wind night. Thus, I’m not sure I favor 3-strand for single line snubbers, though a long lazy loop might prevent this. I’m sure it is geometry-specific. I used 3-strand, but as a catamaran sailor, I always used a bridle (no rotation).
I appreciate Jay’s comments (farther down); the motion of a small boat is different.
Hi Eric,
Thank you for your thoughtful comments.
To fill in the gaps, we used an EPDM rubber snubber with 3 strand nylon. Maybe better for docklines than anchoring as they do stretch a lot but we were still trying to figure out a system. When we switched to the brait the snubber length remained the same and there were no other changes to the anchoring system.
Hi Eric,
The paper made me uncomfortable too, but I don’t have the knowledge to clearly explain why. Thanks for filling that in.
Re: Old Style Anchors mentioned above…. one cannot discount/underestimate the value of the ‘old style’ i.e CQR….. In 1997 whilst delivering volunteer aid on the island of Niuatoputapu we had Cyclone Keli pass right over us! It was the first recorded post-season tropical cyclone to form in June within the South Pacific Ocean. Big surprise for us. Niuatoputapu is not a good place to be for something like this. I have a photo of our boat taken from another boat in the bay just as the eye was passing over…. only 40knots of wind in the eye! Not sure how to upload photos to the blog?
Anyway…. at over 60 knots it becomes a white-out … the chop/spray on the crests of the waves becomes vaporised and you are sitting in very, very loud fog. One must trust their gear… This is all before Spade anchors became available as mass produced items .. there were a few Germans we met who had fabricated on their own versions of what was to later become the Rocna.
Anyway… the CQR (our bower at the time) we sat out the Cyclone with buried so deeply in the sand we had a hell of a time retrieving it and when we did, the Forged shank was curved/bent! Our peak recorded gust was 93knots…. just a walk in the park for some, but for us it scared us a lot: at the time, in 93 knots one does not know how much worse it could still get.
We were very glad for our CQR at the time.
In-Tandem, Backing the Bower…. here in New Zealand we have been some severe weather at anchor…. In 1998 in Pomare Bay (In the Bay of Islands)…. I do snorkel and check my anchoring… we had notice that a big blow was coming so we brought up our bower (at the time a 45lb CQR) and ‘backed’ it with 30 feet of chain and a 45lb Bruce. When the 50knot plus winds came, everything was secure and even when the wind shifted almost 180 degrees, things remained secure. After the blow I snorkelled the anchors and found them BOTH buried in the muddy bottom…. reaching into the mud to feel the orientation of the anchor shanks confirmed they were aligned one behind the other (and 30feet apart) despite the wind shift. One did not ‘trip’ over the other as I thought could happen. I don’t know where the data came from that the other member posted, regarding a 20 degree shift in wind direction causing the anchors to loose traction…this empirically has been our first hand experience when there is a lot of wind around. This scenario has proven true repeatedly for us… Maybe it something we are doing different??
Steve Dashew wrote about backing the bower on his boats back in the 1970’s and 80’s and vouches that this was his standard arrangement when at anchor someplace and they were going ashore…… same thing for us…. peace of mind…..
We have never had trouble retrieving the anchors when leaving the anchorage… just need to be organised and methodical.
We recently purchased a spade anchor…. a 25kg Manson Supreme… yes… it is better in New Zealand conditions…. We still use the CQR though in loose sand when in the Pacific Islands.
Hi Devon,
Much of what you write matches my experience.
And I was very happy with the performance of my CQR over a few decades: it basically never let me down once I got it set even in hurricane conditions. It even re-set under many major wind shifts.
The trouble was, for me, when I moved to cruise in areas where it was hard to find soft sand or mud: getting the CQR a good stick became an ordeal and moving to the similarly sized Spade made establishing a good stick in the seabed far easier to accomplish and was a huge relief.
So, experientially, my Spade anchor is most important for me for its ability to get into a wide range of seabeds and find a good stick in the more marginal anchoring situations.
My best, Dick Stevenson, s/v Alchemy
Hi Devon,
No question that the CQR can develop some impressive holding once set in a bottom type that works for it, but the big problem with the CQR is the limited bottom types it does like. For example, from bitter experience I can say that it’s totally useless (won’t set at all) in hard sand or if there is any weed or kelp around. The other issue is that if it does start to drag in a blow, it does not easily reset, again bitter experience talking here. Bottom line, the modern anchors are just better all rounders and also I have never seen a pull test that rated a CQR ahead of a SPADE or Rocna in any bottom type. Not saying it couldn’t happen, but I think it’s so rare as to be inconsequential.
As to tandem anchoring, again, I just don’t see the point now that we have better anchors: https://www.morganscloud.com/2012/12/14/one-anchor-or-two/
Just better to use one big modern anchor and more reliable too. And much safer to retrieve.
Just found a very impressive video where a Rocna gets tested for set and reset against a plow type anchor: https://www.youtube.com/watch?v=kyd-trE0Xqw
And I wouldn’t like to have my boat hooked up like this (CQR on sand/gravel) as well: https://www.youtube.com/watch?v=d_2MJsNruAA
Hi Ernest
I thought this was a good video and that this could be a good representation of the difference beteeen a CQR and a Rocna. But I’m not sure it is representative of what happens in real situations with a Rocna.
I thought the Rocna was pulled at a rate much slower than the plow and much slower than one would drift with a reset of the anchor in strong wind conditions. My experience with an 88 lb Rocna is that it would not set if backing at more than 1 1/4 knots. This Rocna was pulled VERY slowly. This is why I switched to a Spade.
Best wishes,
Charles
s/v Dawnpiper
Snubbers!!! A must have!
During Cyclone Keli in 1997 we heard a noise like a gunshot above the howl of the wind…. the 3 strand rope we were using then for our snubber exploded where it was attached to the chain hook….
I had to put on a mask and snorkel and crawl to the foredeck to replace it with a spare (have it ready!) …. full rpm’s on the motor to give me some limited help!
We use longer and longer snubbers (on 8 stand plait these days) as the wind picks up… like a longer and longer ‘rubber band’ to absorb the loads. Coincidentally this also increases the catenary/weight effect of the extra chain let out which I had not considered until this post……….
Having been a long-time lurker on this web site, this is my first comment. I have greatly enjoyed the varied ideas and practices on this topic based on both science and actual experience. It can easily be said that anchoring topics are probably one of the most over-analyzed part of boating.
A perspective that hasn’t been heard that may have some value for some, is that of anchoring large ships. My background includes 60 years in recreational boating, 28 years in towing vessels and 22 years as a ship pilot. Anchoring large vessels (300′ to 1200′ LOA) in depths of 10-45 fathoms is a common pilot assignment.
Obviously, anchors and chain rodes on these large vessels weigh thousands of pounds (And we don’t get to choose the gear!). But we use most of the same techniques to safely anchor: Lowering the anchor to near the bottom before laying out the rode, backing the ship to set the anchor, and monitor.
Vessels of these sizes have no snubbers, our first tool to ease the strain on the rode is to veer more chain if conditions require and permit. In Gale and Storm winds, the catenary can easily be eliminated, the next set of tools includes putting out a second anchor in what we call a “short stay” (our term for Hammerlock). A rode of 2x the depth is common. This reduces yawing and sailing to the anchor, and helps the primary anchor by keeping the vessel’s profile turned away from the strength of the winds. Other options include heaving anchor and moving to another anchorage that may be more protected from the winds, or use of the ship’s propulsion or tugs to help maintain position.
Some of these vessels do not have enough chain onboard to safely veer in case it is needed. While most large vessels have 10-12 shots (90 feet each), we don’t usually put out more than 9 shots in 45 fathoms depth: A 3:1 ratio. When we get into shallower waters, we will put out 5 shots in 15 fathoms: A 5:1 ratio.
It is amazing the number of large ships in a deep-water anchorage that don’t drag anchor in Gale winds. While I think that the weight of the chain and anchor are significant factors in this (and leaving anchor design out of the issue), they don’t scale appropriately to smaller vessels. Large vessel anchor components are comparatively undersized.
So what is it that makes a 3:1 all chain rode work for large vessels anchored in deep water? I think that one of the main reasons is that the dynamic loading does not stay very high for very long. The profile of a large cruise or containership creates significant wind loading (tons and tons), but if a second anchor on a “short stay” is deployed, the effect is to help keep the vessel headed into the wind. This drastically lowers the amount of rode strain, and the amount of time that rode strain is maximized.
So I like the idea of a loop of chain off of the bow roller, especially if deploying a second anchor is not as practical. The important thing, especially if your boat is lively to the anchor, is to have some solution for minimizing yaw, given the normal boat/anchor/rode/crew/anchoring area/bottom conditions variables.
A quick comment on chain. I’ve had excellent service from my galvanized G43 Acco chain, but a recent purchase of less expensive imported chain required re-galvanizing after only 1 year. The galvanizing shop said they were seeing a few orders to re-galvanize new and unused imported chain.
Jay N
Hi Jay,
Very interesting info. I had not heard the term “short stay” before and it is interesting to note that it is in the bag of tricks that you guys use. Out of curiosity, do you ever gently back down against the anchor to try to limit yawing? I know that the US Navy recommended it and I have tried it on a small boat to good effect although it took a fair amount of reverse. For larger vessels with very limited rpm control, I would imaging that you might actually have the opposite problem and it may require a CPP to be able to modulate the thrust as desired. I have other issues with the technique for cruising boats but was just curious whether people actively use this old recommendation.
I think that shear size has an interesting effect on dynamics that I certainly have never taken the time to properly understand. One thing that I have noticed is that larger vessels tend not to have issues with pitching in the way that smaller ones do provided you are not anchored in really large waves. I have been anchored in conditions in a boat as little as 100′ that was sitting very quietly while 40′ cruising sailboats were pitching through 40+ degrees right next to us. I would think that the key has to do with the relationship between your waterline length and the wavelength but I don’t know exactly where the critical point lies.
Regarding your scope comments, the scopes you mention are similar to what I have experienced on somewhat smaller commercial vessels and they don’t seem unreasonable for anything short of a full storm given the depths you are in. If we ignore the dynamics side of things for a minute, you can define adequate scope as the last link of chain before the anchor being horizontal and in really deep water, it takes less scope to get there.
Eric
Hi Eric. I have not backed a ship’s engine/propulsion while anchored, nor have I heard of anyone else doing it. In practice, ships generally do not want to operate their machinery at anchor, engine room must be staffed, captain on the bridge, etc. Also, most ships with fixed pitch propellers have a limited number of air starts, and recovery is also limited. I can visualize the potential effect of the vessel reacting to reverse along with the propeller torque, but doubt that it would remain steady enough to provide anchoring security without constant attention.
Yes, large vessels in protected anchorages do not have to contend with the impact of large waves. On my own 12 meter power boat, I have anchored in storm winds that produced 3-4′ waves that obviously added to the dynamic forces on the rode. On the other hand, deeply loaded tankers (50′ drafts) may almost ignore strong winds if in the influence of strong tidal currents.
Hi Jay (and Eric), interesting observations thanks for posting.
A few years ago I posted on AAC about dragging anchor in Wellington harbour (can’t find the post now) – I was the officer of the watch on a large container ship. This event was preceded by the ship yawing 20 degrees either side of the true wind. Wish I had known about the “short stay” method, as it certainly wasn’t taught to us in Nautical College. I guess there may have been concern about the short stay anchor fouling the bottom – has this caused issues in your experience? Do you scan the sea bed before anchoring?
Eric, we never once used backing down on the engine, but then none of our ships had VPP that I recall. That said, I would worry about prop walk making the yawing worse, not better. Most times if the anchorage got untenable we just steamed away and in the case of the above incident, whilst dragging the anchor behind us until safe and clear.
Rob
Hi Rob. The usual large vessel anchorages in my pilotage district have been used for many years. Obstructions are known and avoided, occasionally a NOAA survey vessel will come through the area to check on the bottom, but otherwise the assumption is made that the bottom is clear.
I don’t recall any anchored ship using a second anchor in “short stay” having any problem in retrieval. Of course, as soon as the wind abates, the second anchor is retrieved so often it may only stay down for 4-5 hours or so which is the common duration in our area of gale/storm force winds.
Interesting comment about steaming away with the anchor. Many older ships do not have sufficient power at the windlass to retrieve 9 shots if the anchor is off the bottom in deep water. I recall one instance of having to steam into shallower water, haul in 2-3 shots, then run into even shallower water to finish bringing the rode/anchor aboard. Fortunately, more modern ships are better engineered/equipped.
Hi Jay and Rob,
Thanks for the info, I have always been curious if this technique was ever actually used.
Around our home waters, the famous concern about ships dragging anchors is that when they built a 10 mile sewage outflow tunnel, the contractor refused to pull the safety plugs for the risers at the end of the tunnel out of concern that a ship dragging anchor could rupture one flooding the tunnel. No anchor ever damaged a riser but there were unfortunately deaths due to the initial way that they tried to remove the safety plugs.
Eric