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Old 01-31-2018, 11:09 AM   #1
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How Much Chain

How Much Chain

Iíve thought for some time that the real advantage of some chain is to help the anchor get a grip on the bottom and set. Getting the fwd end of the shank down to the sea floor is almost a must for most anchors.

Most of us have seen vids of anchors trying to set w/o any chain. The line obviously pulls the shank up (not down) and most anchors w a line rode will just skid along the sea floor w very little resistance. Steveís vids shows a Claw doing that but most other anchors will. This can largely be avoided w a long scope but who wants to let out that much line?

Somewhere in our TF anchoring archives thereís been more than one discussion about where along the line is the weight of chain most beneficial? I think Marin Fare was involved in one that according to some scientific study w or w/o marine interest (may have had nothing to do w anchoring) that to force catenary in a line whereas one end is considerably higher than the other the point along the line is rather close to the lower end. I think the spot was determined to be about 6í ahead of the anchor on a typical rode.

This would mean that where one would place an anchor Kellet (weight) along oneís rode would be about 6í from the anchor. There are several ways to optimize the catenary effect.
1. Use a chain of considerable weight attached to the anchor shank about 12í long.
2. Use a weight attached to the rode about 6í ahead of the anchor.
3. Deploy a kellet to the rode about 6í ahead of the anchor.
4. Tandem anchor w one anchor being about 6í ahead of the other.

Thatís about it for opitimizing the weight along the rode to maximize the amount of catenary w a given amount of rode weight.
All chain is a terrible waste of rode weight in that the upper part of the rode does little or nothing to aid catenary. If you had a 300# chain rode and changed to a combination rode of the same weight youíd have far more catenary. And according to most much more anchor performance. There are variables that would make this untrue like if you had a 1000í chain rode. But itís very true for most all or all anchor rodes.

So the ideal rode should be w about 12í of chain or to make one sure for good measure .. 20 to 25í of chain.
But most of the above is based on my recollection of something I read on TF a long time ago.
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Old 01-31-2018, 11:26 AM   #2
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I'm sure the anchoring engineers will weigh in shortly....

In real life experience, I've never Not had my anchor set almost immediately. 10' of stainless chain attached to a 7.5kg Stainless Trefoil anchor (Bruce clone).
Admittedly, I'm usually in 5-15' of water and usually a Mud bottom. We anchor out a lot.

Your mileage may vary..
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Old 01-31-2018, 11:33 AM   #3
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I have 300í all chain, Fortress FX-37 for ground tackle. The main reason is I go out alone a lot and the windlass has a chain wheel on one side a capstan on the other. Being on the river I do not want to use the toe switches on the bow with no one at the helm. With all chain I use the switch at the upper helm while I man the helm. I normally anchor in a depth of 20í or less.
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Old 01-31-2018, 12:03 PM   #4
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I am always slightly in awe of boaters who anchor in 10-30' of water, that's less than the tidal range up here. If I don't have 40' under me and around me when I drop anchor then I am only there for lunch and at short scope. If I have more than 150' under me then I am fishing and at very short scope.

The angles that the bottom here usually drops away is an issue, and you don't want to swing into shallow water with a tide change or wind shift and find yourself aground as the tide goes out.

I traveled with a Fisher 32 owner last summer around the Kenai Fiords, he was all chain and had to anchor in so close to shore to find water shallow enough to get any scope that it looked like he was on the beach :-) He did mention that all through Prince William Sound he had to work to find an anchorage due to his all chain rode. He also planned to "upgrade" to a mixed rode in the future for that reason.

I think for coastal cruising and anchoring in protected places a mixed rode is perfect, if I were a world traveler and had to anchor in open anchorages all chain would be preferred. Wind and current seldom load my anchor line to any extent in the places I frequent.
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Old 01-31-2018, 11:41 PM   #5
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I used 50' of chain with 200' of nylon three strand. My boat was a relatively light weight planing hull, so I didn't want to put a big lump of chain up forward. Worked well for me and my fortress FX16
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Old 02-01-2018, 12:08 AM   #6
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wouldn't the ideal placement of the kellet depend on the bottom, or more specifically, the resistance provided to the anchor ? There are a number of dynamic forces at play here. When you first start to back down on the anchor....the anchor is sliding along the bottom. A hard smooth bottom that provides no resistance will have the catenary a certain shape. Now if you go to a sandy spot, where the anchor is dragging in loose sand...the line will have a different shape....and the ideal size and location of the kellet is probably different. Once the anchor bites and you back down on it to set it, there is almost no catenary as the line should be straight, ( assuming your boat has the power to lift all the chain )

Also, once everything is static...or as static as things can be on a boat .....the weight of the chain provides a smoothing function. with 30-50 feet of chain on the bottom.....wind and wave action will left some of that up and smooth out the action of the boat, rather than tug on the anchors bite on the bottom.
Then there's also the greater resistance to chaffing on rocks for chain.

I guess all I'm saying is its possible there are no universal truths for all boats and bottoms.
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Old 02-01-2018, 07:24 AM   #7
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I'd guess there's no single "best" length of chain.

Influencing factors from the anchor design would likely be things like how much of the anchor's weight is in the shank, the normal/typical landing attitude as the anchor hits the sea bottom, the angle the flukes require for follow-on digging in (usually that's available in manufacturer recommendations, often expressed as scope to aim for while setting), current sea states (e.g., surface wind and/r currents impacting catenary), and so forth.

IOW, I'd suspect it may be 6' for anchor A, 10' for anchor B, 25' for anchor C, etc. Those may also benefit from a range of chain length instead of a specific length: 6-8' for A, 8-14' for B, etc...

An entirely unscientific thought process...

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Old 02-01-2018, 08:08 AM   #8
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You can analyze the physics and conclude as Eric postulates that 12' of heavy chain, say 1/2" will do almost as much good as 100% chain.

But all chain does a couple of more things than just keeping the shank down towards the bottom:

Chain doesn't chafe and the catenary keeps the rode down below the keel when the boat swings. Not so important for trawlers but for sailboats with fin keels it is very important. I once watched a sailboat chew through its rode in a wind against current situation in Nantucket.

But the most important advantage to an all chain rode that trumps all others is a single, smooth way to haul up the chain with a windless. A chain/nylon splice may pass over the windless gypsy ok but will your nylon rode easily drop down your hawse hole from the windless? None that I have seen will do that. Once you start hauling up nylon, it bunches up and has to be pushed in the hawse hole manually.

That is why I will always use all chain rode with a windless.

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Old 02-01-2018, 08:51 AM   #9
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Posts 1-5 point out that there’s lots of variables on how much chain one should use. Fo me I use chain two sizes bigger than is normally used for my boat. I pull the rode w the capstan but that’s not good for chain. So I stop before the chain is up and hand over hand the rest. So I like it short. But it’s the same weight as if it were longer. One could even call it cheating. But IMO as long as I can get the anchor set well I need no more .. chain.

Wayfarer has a light boat so using more than is needed is a bad choice.

AKDoug anchors deep often and at very short scope.

River Cruiser needs to stay at the helm.

ranger42c is looking for scientific thought. And Benthic2 is thinking a lot like me.

I wasn’t thinking of any variables in the boating application at all. Just establishing the best place on the rode for weight. And excluding variables like scope and bottoms ect. I was looking for a rule of thumb for average scopes used. I was even excluding chain weight and length of rode.

I also think that weight high on the rode of an all chain rode actually reduces catenary at the anchor. I suspect it’s a small amount that dosn’t need to be considered.

Over the years many talk a lot about maximizing catenary and stress it’s importance.

Beyond corral and other bottom abrasion one needs only “a short length of chain” as Chapman says. But Chapman is mostly for lighter and smaller boats than trawlers. More variables.

And then there’s the boat size. I myself would use all chain on a 60’ boat w a full bow like on a Willard 36 or the GH.

Applying weight to the rode is the primary (by far) function of chain. And catenary is the desired function of the chain and it’s weight. And my question is to reveal that there’s little or no benefit to rode weight half way (or more) up the rode. 99% of the need for weight is at a point on the rode very close to the anchor.

IMO many boats on this forum should have all chain. But most should have less. And smaller boats (30 some feet) should minimize chain weight by length or size. And lighter boats yet should use HT chain.
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Old 02-01-2018, 08:57 AM   #10
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David,
Sounds like you have a 3strand problem w the feed through the hole. Do you have brait line? May be the answer to the line bunching at the hole.
What size chain do you use?
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Old 02-01-2018, 09:20 AM   #11
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It really isn't a problem with my boat or any of the ones I have owned as they all have all chain rodes. But I chartered a Camano 31 once with a short chain and all nylon after that and my buddy's CHB45 has a horizontal Muir? windless where the rode drops down into the hawse hole and he has a short chain followed by nylon.

The Camano did not have a windless and I had to haul the anchor up by hand. It was impossible to feed the rode into the hawse hole as I pulled up the anchor due to kinking so I just let it pile up on deck and stuffed it down afterwards. On my buddy's boat we have to stop every 10-20' and feed the nylon back into the hawse hole.

Both boats have/had three strand nylon rode and on my buddy's boat the nylon was old and stiff. Brait is certainly more flexible and might solve the problem on my buddy's boat.

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Old 02-01-2018, 10:19 AM   #12
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David,
I remember stuffing the nylon down a hole in the deck on our Albin 25. PITA. The Willard came w the same oblong hole (can’t remember what it’s called). I said no not that again. My rode has been on deck ever after. We had rode stink some too. But most are too vain to have an anchor rode on deck. Mine’s in a plastic box .. ugly. Could make a teak box and oil it but so much to do.

I almost went w a gypsy windlass this last time I changed my gear but got another capstan. Honestly I wish I had gone w the windlass as I have since had a rotater cuff operation and I haven’t tried the capstan since. We’ll see.

Starting this thread I was only thinking of the ideal place for weight re catenary. Was hoping someone would know where to find the study I refered to in post#1.

David w your system how often do you have trouble w the chain pile? Or do you anchor so shallow it’s not an issue? I keep forgetting all that east coast shallow water.
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Old 02-01-2018, 10:27 AM   #13
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I have the same setup as when I bought the boat except that I replaced a manual windlass with an electric one. 30' of 5/16" G4 chain and 150' of line spliced together. I would have a bit more line but for a communication failure at West Marine. No big deal, I've never used it all (yet).

When talking about chain, there is chain and there is chain. Depending on the thickness and type, there can be a pretty big variation in weight.

So the above rode and a 33 lb. claw anchor has held me securely for hundreds of nights along the USA east coast.
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Old 02-01-2018, 10:59 AM   #14
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Quote:
Originally Posted by AKDoug View Post
I am always slightly in awe of boaters who anchor in 10-30' of water, that's less than the tidal range up here. If I don't have 40' under me and around me when I drop anchor then I am only there for lunch and at short scope. If I have more than 150' under me then I am fishing and at very short scope.

The angles that the bottom here usually drops away is an issue, and you don't want to swing into shallow water with a tide change or wind shift and find yourself aground as the tide goes out.

I traveled with a Fisher 32 owner last summer around the Kenai Fiords, he was all chain and had to anchor in so close to shore to find water shallow enough to get any scope that it looked like he was on the beach :-) He did mention that all through Prince William Sound he had to work to find an anchorage due to his all chain rode. He also planned to "upgrade" to a mixed rode in the future for that reason.

I think for coastal cruising and anchoring in protected places a mixed rode is perfect, if I were a world traveler and had to anchor in open anchorages all chain would be preferred. Wind and current seldom load my anchor line to any extent in the places I frequent.
I am with you AKDoug. East Coast guys have it easy.

I carry 550 feet of chain. Normally, like you I am in 40-60 feet of water when dropping the hook, plus the 20-30 foot tide change. There were times when I was in a 100 feet at the end of a bay. We have found 3:1 was the normal rode in Alaska. There were a few times I had 400 feet out due to wind. Oh and I forgot to mention heavy current in SE.

Yep east coast guys have it easy....
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Old 02-01-2018, 11:09 AM   #15
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A lot of what is being propounded simply isn't the case in real life. Repeated observation will confirm this, along with common sense. Think of the rode as a comprising a weight that the boat has to lift in order to move backwards. This is one reason for using a long bridle for your chain snubber and letting out a long "lazy loop" behind the hook: more weight to lift.

In the relatively benign conditions that people are anchored in 90% of the time. the heavy chain rode keeps a greater length laying on the sea bottom. In most mud or sand conditions, the rode will bury itself in the bottom, sometimes quite deeply. Remember the end of the rode has followed the shank of the anchor down into the mud, furthering this effect. So when forces such as current or wind act on the boat to move it a different direction, you will often times find yourself laying to the rode, sometimes solely with the anchor firmly where it was originally set. The first time I observed this was on a sand bottom, when I noticed my anchor off my aft port quarter one morning, with the rode running forward well beyond the bow. Leaving the chart plotter on with track displayed will illustrate this too in combination with observing how the boat moves over times shown on the track. Any of us who have had to spend a long long time washing mud off a length of deeply buried chain will attest to the phenomena, particulary as the windlass battles lifting what looks like a vertical chain well before getting to where the anchor is.

I can't estimate how many times we were laying quietly and moving slowly while adjacent boats were snapping violently at their rope rodes and horsing much more dramatically than we. But it is a lot.
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Old 02-01-2018, 11:34 AM   #16
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OK, let me address the physics/geometry question posed in Eric's first post.

If you have say 50 lbs of weight that could be placed anywhere as either a kellet or 30' of 3/8" chain, then I think that the best use of that weight would be as a kellet mounted to the eye of the anchor shank. All 50 lbs is pushing down on that shank. If you use 50 lbs of chain then part of its weight bears on the anchor eye and part of it is borne by the nylon that leads up to the boat. How much is borne by the boat depends on the length of the rode and the depth of the water.

All of which suggests that an improved anchor would be one with a heavy bulb of metal around the eye. Also a longer anchor shank lets that weight whether it is chain or kellet operate more effectively to keep it down.

So the very best anchor would have a long thin shank with 50 lbs of weight at the eye. Hey I just invented a new anchor. But will it sell????

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Old 02-01-2018, 02:33 PM   #17
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Haha David you just described an old anchor I have. Dreadnought. Iím at a coffee shop now so canít post a pic. It has the longest shank Iíve ever seen and itís round .. the shank. But itís not the ideal anchor for a number of reasons mostly that it lacks blade/fluke area.

ďKellet mounted to the eye of the anchor shankĒ
Yes thatís what I thought too but the study I refer to says no. The optimum spot was said to be 3-8í ahead of the anchor eye. Not at the end of the shank. Some things that seem obvious .... arenít. Unless it is of course. I (of course) donít know but now it seems or feels like ďthe spotĒ should be up the rode a bit.
Canít prove it of course but I can prove (in my mind) that weight applied to the rode 3/4 of the way up toward the boat will actually reduce catenary. Weight placed high on the rode well above the center would push the rode down at that point and I believe that the rode 1/4 of the way up should RISE. IF .. that is true then the weight of an all chain rode re the benefits catenary is far from ideally distributed or placed on or along the rode. Am I making any sense? Any lights going on? Or can anyone say thatís not true because ......

I could prove this w a rope strung between two trees w a weight hung on it in various places. Cold and wet outside though. Hmmmm

David the anchor you just invented is a genuine Danforth w a forged shank. I have a pic of that at home too.
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Old 02-01-2018, 02:51 PM   #18
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caltexflanc,
That’s interesting and well enough described that I understand it. An anchor rode that had a chain starting 1/4 up the rode and ending at the 1/2 mark would do that big time especially if it was heavy chain.
Never heard of that happening before though. Obviously it wouldn’t happen to me w so little chain. Don’t see how it would limit sailing though.
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Old 02-01-2018, 02:59 PM   #19
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benthic2 wrote;
“wouldn't the ideal placement of the kellet depend on the bottom, or more specifically, the resistance provided to the anchor ? There are a number of dynamic forces at play here. When you first start to back down on the anchor....the anchor is sliding along the bottom. A hard smooth bottom that provides no resistance will have the catenary a certain shape. Now if you go to a sandy spot, where the anchor is dragging in loose sand...the line will have a different shape....and the ideal size and location of the kellet is probably different. Once the anchor bites and you back down on it to set it, there is almost no catenary as the line should be straight, ( assuming your boat has the power to lift all the chain )”

Yes indeed. One of the more important variables.
Remember w Steve’s vids when he attached a nylon line to a Claw and tried to set it. The shank stayed up and the anchor just skidded along on it’s bottom like it had places to go.

There’s a wide range of tensions, scopes and rodes. And hence a wide range of catenary angles.
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Old 02-01-2018, 04:38 PM   #20
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ranger42c is looking for scientific thought. And Benthic2 is thinking a lot like me.

Yep. I used a very scientific approach to our own rode.

Had all chain when we came back north from FL. Noted how long it takes to clean the Chesapeake mud from all chain. Decided that was too much work. Changed all chain to a 25' lead section, turned the rest into 300' of 8-plait rope. All good.

And very scientific.



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