Anchor rode question.....again

[Marin]

RTF--- You could start a new thread about the sex life of the Edwardian earthworm and if you managed to include the word "anchor" in it, it would end up being some 600 posts long just like all the other ones. The first post would be about the earthworm and the rest would be about anchors.

In the 27,762.5 posts about anchors on this forum so far, I personally think the ONLY one that has any real validity (besides all of mine, of course), is one Eric Henning made at one point.

I'm paraphrasing, but he said that the chances of the typical recreational boater ever experiencing conditions that would seriously tax whatever anchor setup his/her boat has are minimal.

Based on the efforts most [intelligent] recreational boaters go to to avoid being put in dangerous situations, I believe Eric's statement is right on the money. Which means that as long as a boater selects an anchor with a proven track record, the chances are it's going to do just fine almost all the time.

There will be exceptions, of course, like our experience with the Bruce we used to have. But whether one chooses a Rocna, a Manson, a Sarca, a Bruce/Claw, a Danforth/Fortress, a CQR, a Spade, etc., the chances are very high that the boater will never have a real problem.

Sure, they may have to make a couple of tries every now and then to get the anchor to set properly in a squirrely bottom. (It would have been interesting to see how the results of Fortress' mushy mud test would have differed had the anchors that didn't set or didn't set well in the test had been tried again, or tried again using a different setting technique, or tried again in a slightly different place.)

So I agree with Eric, and I think that for the most part the thousands of posts about this, that, or the other anchor and this, that, or the other rode are mostly armchair theorizing and opinionating. Which is loads of fun to do but can be confusing as hell to the poor schmuck who's trying to figure out what to put on the bow of his boat.

So the bottom line for him is, I think, that in recreational boating's real world-- which is the only one that counts--- all of the proven designs seem to work just fine 99 percent of the time if they are used intelligently.

'Intelligently," by the way, includes taking into account the conditions under which the anchor will be used and selecting one that has been proven to do well in those conditions.

 

[eyschulman]

Marin and Eric I agree and since this PO asked about chain and rode I think the same reasoning about the real world anchoring applies. It matters not chain or rode just so long as intelligently used. If people feel more secure with 400 ft of chain fine but there are others who do well without all that chain actually except for chafe can do with no chain a 10 ft piece of wire would do fine.

 

[Nomad Willy]

Thanks for the nice words Marin. I have this idea that our differences (re anchors) may be rooted in the fact that usually I think I'm talking about anchors for the fun of it. What if we changed this or that. What design features promote what kind of performance ect ect. But you and most others are trying to plug in "real world" facts (frequently presumed) and placing heavy importance on what anchor is best or what we should be using. The idea that only a "modern" anchor should be used and it's stupid to use anything else is disgusting to me and I tend to fight that when it pops up .... and it pops often. Our culture worships the latest things and what's popular to the extent that most objectivity is lost and most people have this burning NEED to be on the bandwagon w the coolest and latest things from how to talk .... remember "far out"? And how often do you hear "AWSOME"?

I think we should strive for clear thinking and objectivity ... especially in our boating decisions.

And yes I did say those things Marin. That almost always anchoring goes well. And the reason for it is that we only very seldom have the misfortune to put our ground tackle to a real test. I can count on one hand the number of times I've anchored in winds over 40knots or about 45mph. So this anchoring isn't all that important unless you get very unlucky.

I'll bet most of us have learned a great deal about anchoring and the gear on TF. I know I have. I find it very interesting and tend to spill my brains on it and seek others to do the same. I'm a "P" type personalty ... preferring things undecided leaving "possibilities" whereas probably most are "J" types that like things decided .. and aren't happy until that comes to pass.

 

[Nomad Willy]

Marin and Eric I agree and since this PO asked about chain and rode I think the same reasoning about the real world anchoring applies. It matters not chain or rode just so long as intelligently used. If people feel more secure with 400 ft of chain fine but there are others who do well without all that chain actually except for chafe can do with no chain a 10 ft piece of wire would do fine.

Yes I strongly suspect that once the anchor is set it really dosn't matter if the rode's chain or line. The only reason for chain over line seems to be the benifits of catenary. And in a strong blow the catenary is gone from the chain and of course the line rode.

 

[Noelex]

Yes I strongly suspect that once the anchor is set it really dosn't matter if the rode's chain or line. The only reason for chain over line seems to be the benifits of catenary. And in a strong blow the catenary is gone from the chain and of course the line rode.

.+1 A great summary

Many people have a hard time believing the catenary effectively disappears in stronger wind, so hopefully a picture will help.

This is a photo of a 15kg Rocna being set by a 34 foot sailboat. The force of the engine alone is enough to practically eliminate all the catanery as you can see. It was in 17 feet of water the scope was 4:1 and it was 8mm chain.

Sailboat engines are only small (this one was 27 HP) and with the engine run at 2500 rpm the force is the equivalent of about 25-30 knots of wind.

 

[Djbangi]

.+1 A great summary

Many people have a hard time believing the catenary effectively disappears in stronger wind, so hopefully a picture will help.

This is a photo of a 15kg Rocna being set by a 34 foot sailboat. The force of the engine alone is enough to practically eliminate all the catanery as you can see. It was in 17 feet of water the scope was 4:1 and it was 8mm chain.

Sailboat engines are only small (this one was 27 HP) and with the engine run at 2500 rpm the force is the equivalent of about 25-30 knots of wind.

It might be a more interesting image than simply showing the lack of catenary.

If you look carefully you will see that the chain is twisted. This is an anchor that is being set, so its been deployed and loaded (by the 27hp engine). There is no obvious reason why the chain should be twisted.

I stand to be corrected but I think the owner of this yacht had been using a swivel (when the image was taken) which might suggests swivels do not work. But why is the chain twisted in the first place, swivel or not. But there is also a 'lot' of twist.

The chain is deployed through the gypsy/wildcat/chain wheel and I cannot see this causing a twist, maybe the bow roller itself? the anchor acts in some hydrodynamic manner and rotates? The phenomena is not unusual.

I have no ideas - just the question.

edit - further, if anyone agrees that there seems to be a 'lot' of twist for a newly deployed anchor then the suggestion is that swivels are unnecessary as this anchor appears to be setting without that twist having any impact at all. close edit

 

[FF]

The usual rule of thumb is a good prop will create 20lbs of thrust .

A 27 hp engine in reverse will not get that number as props are picked for the vessels normal cruise speed ,

Not for static bollard pull in reverse..

At best the photo shows 500 lbs of pull , and of course the chain is bar tight at the same angle all nylon line would be.

The difference is in a blow , where if not over sized,, the nylon can stretch 10% or more , easing the load on the anchor.

Chain just gets bar tight and transmits any shock load directly to the anchor, as a steel cable would.

 

[Noelex]

If you look carefully you will see that the chain is twisted. This is an anchor that is being set, so its been deployed and loaded (by the 27hp engine). There is no obvious reason why the chain should be twisted.

Yes good observation.

The chain often appears twisted when I see anchors underwater, even if the anchor is recently deployed. I have not noticed any correlation between the presence or absence of a swivel, but I will look more closely in future.

The photo below shows a Kobra anchor (one of the convex plow anchors) that I was watching change direction with a 180 degree shift in light wind. You can see at this stage the anchor has not moved, but the chain is leading back in the opposite direction.

The real reason for including the photo is that it shows a long length of chain and, as you can see, it appears twisted. You can also see the catenary that is present in light or light/moderate wind. It is a pity this is lost in stronger wind when it is really needed.

I am reasonably sure the Rocna in my previous post did not have a swivel and this Kobra did. The Rocna had only just been dropped and I think from memory the boat with the Kobra had been anchored for about 24 hours.

 

[Nomad Willy]

Interesting mystery. Just a thought ... perhaps many other anchors rotate through the water like a maple leaf as they descend. It's common knowledge that the Danforth types do but I thought it was limited to them as I've not heard any talk of others doing the rotation fall. Anyone seen that happen ... in clear water perhaps?

Also in that soft sand you'd think the anchors would be deeper in the sand. Both of the shanks are still visible. One would be inclined to belive in a harder bottom even less penetration would result. I've seen the Kobra in European anchor tests and it performs very well there.

 

[RCook]

I'm really pleased with my Rocna which replaced a smaller genuine Bruce. Over the last three summers of anchoring in SE Alaska, it self-launches, sets quickly, holds like crazy, and resets without complaint when the wind shifts.

All terrific, with one exception: I never had significant chain twisting with the Bruce, and now I do with the Rocna. Maybe the Rocna, having bigger fluke area, and maybe being built very slightly asymetrical or welded just the tiniest bit crooked (??) just does that.

Enough so that last year I added an apparently robust Suncor SS swivel. It helps quite a bit, but does not totally get rid of the twisting.

 

[ksanders]

I'm really pleased with my Rocna which replaced a smaller genuine Bruce. Over the last three summers of anchoring in SE Alaska, it self-launches, sets quickly, holds like crazy, and resets without complaint when the wind shifts.

All terrific, with one exception: I never had significant chain twisting with the Bruce, and now I do with the Rocna. Maybe the Rocna, having bigger fluke area, and maybe being built very slightly asymetrical or welded just the tiniest bit crooked (??) just does that.

Enough so that last year I added an apparently robust Suncor SS swivel. It helps quite a bit, but does not totally get rid of the twisting.

I'm really pleased with my Bruce Anchor Over the last 14 summers of anchoring in Alaska, it self-launches, sets quickly, holds like crazy, and resets without complaint when the wind shifts.

 

[Alaskan Sea-Duction]

Lucky for you, this is the shortest month. You won't have to wait too long for the next month to reset the spending clock.

That's right! Honey I need a few more boat dollars!!!!

 

[eyschulman]

So is twisting another reason not to use so much chain? Can that be added to the expense-the weight in the bow-rusting-shock loading-hard to clean mud off-noisy-restricts deeper bury of anchor-and now twisting.

 

[psneeld]

Anyone know why some chain twist is a problem?

If twist is an issue under load....that's where a swivel may start to work better....at least till the strain becomes to great for any friction.

 

[Nomad Willy]

Don't recall anyone saying it was a problem Scott but I hear your (subtle and nicely done) implication that it was presented as such.

But I sure don't see it as a problem. Never seen anyone put a swivel on a line rode. No one complains about twist in nylon line and like a tea bag it should find it's equilibrium as the rode is hauled in. Same w chain. Mystery?

Can anybody's confirm that twisted rode is a problem?

 

[RT Firefly]

Greetings,
Mr. mb. "Can anybody's confirm that twisted rode is a problem?" Only problem I can see is if it untwists the factory installed twist.

 

[Larry M]

...anchored in 300ft in...typical rode for Alaska is 600'

...550' of anchor chain and new windlass...

Anchoring and retrieving in those depths will put most windlasses to the task. The standard windlass motor is high torque, short rated and not for continues duty. You'll probably get a few nuisance trips at the breaker. Nothing to worry about, that's what the breaker is for, if the system is wired correctly. Don't ask me how I know.

 

[eyschulman]

Can anybody's confirm that twisted rode is a problem?

Twist as long as it does not become kink is no problem for me, but I suppose it might be for somebody who needs all his blocks lined up in perfect precision. Functionally I see no issue if the anchor on the way up has to spin a bit maybe beneficial if it helps shed mud otherwise it will take care of itself.

 

[Larry M]

I had posted this in a previous thread.

I measured 2 feet of 3/8" G4 HT, about 20 links. I then twisted it to see what happens. I easily twisted the chain 1 complete revolution with no kinking. If I had to say what is the average amount of road we put out when anchoring it would be ~150 feet. So that says the boat could rotate/twist 75 times without the chain kinking?

 

[eyschulman]

550 ft of chain. There are many boats in the 40-50 ft size that would suffer with the bow weight. I suppose a heavy FD boat with a wide entry and plenty of bow buoyancy could handle it with grace, still it would add something to hobby horse tendency although it might be small effect. I tried 250 ft 0f 3/8 th chain in my 48 ft 34,000 lb boat and it was a noticeable problem. By going to 150 chain and then rode and some lead in the stern could balance the boat. If I were on east coat the whole chain would go. I keep the chain because in most of the anchorages I use it lies on the bottom which in PNW can be rocky and hard chafe wise on rode.

 

[Marin]

We have a 44 pound Rocna. It replaced a Bruce some seven or eight years ago. We eliminated the swivel from our setup a good 14 years ago when we learned about the problems a swivel can create. We use the same all-chain rode today that we used with the Bruce. We usually anchor in 20 to 30 feet of water on a 5:1 to 7:1 scope. We use the setting process with the Rocna that we did with the Bruce which includes the use of reverse to set the anchor. This always pulls all the catenary out of the chain. It's not bar tight; there is always a bit of sag from the weight, but not much.

And in every instance where I've bothered to notice, there has always been a bit of a twist in the chain when we pull it straight. With the Bruce and with the Rocna. No difference. Maybe a quarter turn in the chain we can see. I've observed this on land when I've used long lengths of chain to pull hard on something. Along the length it will twist a bit and then the twist comes out at the other end. I'm not talking a full turn, but enough to face the flat side of the alternate links in the middle in the same direction as the flat side of the other alternate links near the ends.

I think it's just the nature of chain to sometimes do this over a long distance suspended under pressure.

And we have never had a problem with our rode twisting or kinking on retrieval even after several days at anchor with the current changes moving the boat all around the anchor more or less continuously. This was as true with the Bruce as it is with the Rocna.

In other words, changing anchor types has had zero impact on our anchoring process or the behavior of our swivelless all-chain rode.

 

[Nomad Willy]

I suspect there may be a glitch in the inside ends of the links caused in the chain manufacture like a cast parting line. I'll look at some chain when I get home. But even if there was such a glitch the chain link would have IMO a 50/50 chance of settling one way or the other so they would average out and not twist. Thinking in text.

It would seem much more likely to be revolving anchors. Do most trawler skippers lower an anchor faster than I would by hand? I've seen many a windlass advertised as "free fall" and that gives me visions of anchors descending very fast indeed and spiraling down.

I would think an anchor hung by any length of chain say less than 1000' should hang freely w/o any twist.

And yes RT I Remember the twist.

I don't care if it twists or not. It's just interesting to speculate on.

 

[Djbangi]

I am very apologetic if I implied chain twist was a problem. I simply meant to observe there was twist and I then opened up the question as to how it happened.

Now, whether twist is a problem. Thousands obviously think so or why else would they spend good money introducing a swivel with extra connections (each swivel having 3 connections). A clevis pin at each end and the swivelling device itself. Swivels are not designed to be particularly efficient under load, in fact in my experience they are not particularly efficient at all. (I'm not keen on swivels).

People who use swivels come out with the story - its there to untwist the chain in a change of tide or wind - the image shows many more twists than would ever occur in a change of tide and those twists do not appear to alter the performance of the anchor. The anchor might not have been set deeply, which if it was soft sand and it had been loaded to 500lb (a load with which I'd agree) is simply not deep (in my book its not set 'properly' - but if its hard sand, different result). But 500lb on a 35' yacht, maybe 30 knots of wind.

But again ignoring the depth of the set the anchor looks square, it does not appear to be influenced by the twist in the chain.

So why do people use swivels.

But I'm still interested in how the twists develop.

 

[Sailor of Fortune]

Don't recall anyone saying it was a problem Scott but I hear your (subtle and nicely done) implication that it was presented as such.

But I sure don't see it as a problem. Never seen anyone put a swivel on a line rode. No one complains about twist in nylon line and like a tea bag it should find it's equilibrium as the rode is hauled in. Same w chain. Mystery?

Can anybody's confirm that twisted rode is a problem?

DO NOT use a swivel with a 3 strand soft (line) rode , you will be sorry. I don't know if it will work with Brait line or not.
Twist in an all chain rode isn't a problem as long as you don't expect the windlass/winch to pull your boat ahead, against the strain .let anchor and chain come off the bottom (motor ahead/slack) and let the chain untwist on its own. Some patience required

 

[Larry M]

...Do most trawler skippers lower an anchor faster than I would by hand? I've seen many a windlass advertised as "free fall" and that gives me visions of anchors descending very fast indeed and spiraling down...

We free fall our anchor to the bottom every time. We have the ability to lower the anchor either from the pilot house or deck electrically but by the time we've picked our spot and get the anchor to the bottom we have drifted or been blown off where we want it to go. The anchor (s) we use do not spiral down. They do sail or plane thru the water but not far from our intended target. Our windlass is a Lighthouse 1501, one of the better windlasses out there IMHO, but it's slow. Retrieval is ~37 fpm at 12 VDC and going down electrically isn't much faster.

 

[Djbangi]

I had not thought about it - but depends on which way the chain twists and how 3 strand (or which way) 3 strand is twisted (or laid) but potentially in a blow and with the chain tight, or tightish, then a twisted chain would unravel 3 strand.


edit I believe some windlass manufacturers recommend the use of swivels (though I have never heard why). The apparent phenomena might be the reason (to recommend a swivel) - if anyone is close (knows) to a windlass maker it might merit a question. close edit

 

[psneeld]

DO NOT use a swivel with a 3 strand soft (line) rode , you will be sorry. I don't know if it will work with Brait line or not.
Twist in an all chain rode isn't a problem as long as you don't expect the windlass/winch to pull your boat ahead, against the strain .let anchor and chain come off the bottom (motor ahead/slack) and let the chain untwist on its own. Some patience required

I believe the first time I ever remember the warning of swivels and 3 strand is from old Chapman's dating back into the 60s. I believe the warning was against the line from developing hockles due to it twisting a lot under load and needing that pressure to retwist as the boat springs back when unloaded. Then again Chapman's goes on to say swivels SHALL be used with all chain to prevent it from snarled up.

I'm trying one this year...less about chain twist as aligning the anchor into my pulpit.

....playing around with it confirmed that under relatively lightto moderate loading, they (even the cheapo galvanized one I have) swivel just fine. Except in the most extreme situations...the rode goes from heavy to moderate loading as the boat tugs back and forth with catenary and spring generated by the snubber...so as the load lessens...I'm confident it reaches a range where swiveling can take place.

 

[Marin]

II believe some windlass manufacturers recommend the use of swivels (though I have never heard why). The apparent phenomena might be the reason (to recommend a swivel) - if anyone is close (knows) to a windlass maker it might merit a question.

As one data point, there was no mention of swivels pro or con in the installation/operations manual for the Lofrans Tigres windlass we installed on our boat a number of years ago.

 

[BruceK]

I fitted a traditional type swivel between the sliding slot shackle (of my Sarca) and the chain, largely to prevent the chain fouling around the shackle.
Identifying the cause of chain twist may be solved with a video of the anchor drop, from leaving the pulpit to set. Break out the popcorn...

 

[Marin]

Do most trawler skippers lower an anchor faster than I would by hand?

Eric-- Our windless has power out, power in. So we lower our anchor at the speed our windlass runs, which in this case is a pretty good clip.

Watching the anchor go down there is no swiveling or rotating action on the part of the anchor as far as I can see it going down. We do not believe in swivels in anchor rodes so all there is between the end of the chain and the anchor shank is a single shackle.

And when we retrieve the anchor, by the time it gets up enough for me to see, there is no swiveling/rotating movement at all. It is usually not aligned with the bow roller as it hangs down by the forefoot, but it's not rotating as it hangs there.