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Old 25-04-2016, 14:56   #1
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Chain Stopper Vs Devil's Claw

Thinking about my still hypothetical future boat, and about the ground tackle handling arrangements.

I'm for sure going to have a massive horizontal windlass with a vertical warping drum, and a sturdy samson post, stronger than the breaking strength of whatever chain I'm using.

But what's the best way to belay the chain? A chain stopper is the obvious answer, but it seems to me that it might be hard to achieve the desired level of strength, since it's just bolted to the foredeck. Maybe it's better to use a devil's claw made off at the samson post? That's certainly the way it would be done on a commercial vessel. Add a hyfield lever to it and it will also hold the anchor in the roller. A bit more work than a chain stopper, though.

What do you guys think?
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Old 26-04-2016, 03:05   #2
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Re: Chain Stopper Vs Devil's Claw

I like the idea of a chain claw secured to a strong samson post. If its heavy nylon it will have a small amount of give that will significantly reduce any shock loadings, and in an emergency it can be cut away to slip the cable or increase scope.

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Old 26-04-2016, 04:21   #3
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Re: Chain Stopper Vs Devil's Claw

Quote:
Originally Posted by Snowpetrel View Post
I like the idea of a chain claw secured to a strong samson post. If its heavy nylon it will have a small amount of give that will significantly reduce any shock loadings, and in an emergency it can be cut away to slip the cable or increase scope.

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I don't have a samson post, but what I have now is a length of stainless chain made off to my inner forestay chainplate, with a chain hook on the other end.

I don't really like chain hooks and never use them on snubbers, and I don't really like using the forestay chainplate for ground tackle -- not what it's made for, although it's strong enough, strongly anchored to the watertight bulkhead aft of the chain locker.

With a samson post this would already be better, and maybe some different type of hook or claw which is more secure, maybe the Mantus chain hook or maybe someone makes a yacht-sized devil's claw in stainless.

I wouldn't use nylon here because it wouldn't be long enough to give any shock protection, and you don't want any risk of chafe at this particular attachment, which is your last ditch in case the SHTF.

So why don't you like chain stoppers? The advantage is that this is less work to deploy.
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Old 26-04-2016, 05:05   #4
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Re: Chain Stopper Vs Devil's Claw

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Originally Posted by Dockhead View Post
I wouldn't use nylon here because it wouldn't be long enough to give any shock protection, and you don't want any risk of chafe at this particular attachment, which is your last ditch in case the SHTF.
The way I figure it, in this scenario any stretch is significantly better than the nearly inelastic chain. Ive broken an anchor chain twice, the snatch was like the boat hitting rocks as the chain lot all catenary. If you had 1 meter of nylon its going to stretch 10-20% safely, giving 100-200mm of stretch. Chafe isnt a big issue, as it shouldnt rub on anything, and even can be covered in chafe gear/anti uv over its whole length.

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So why don't you like chain stoppers? The advantage is that this is less work to deploy.
They jam closed under load. Maybe you could rig a line back to a winch and take the tension off it, but in the worst case scenario thats going to be hard, as the load will be extreme. Especially if you are singlehanded.

A rope can be cut easily in this scenario. Admittedly it is a pretty unlikely scenario if you practise decent seamanship and avoid getting caught on a nasty lee shore in hurricane conditions with a failed windlass!

Also it can be hard to set up a chain stopper that leads fair onto some windlasses, and its another fitting to buy, maintain, stub you toe on, leak etc.
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Old 26-04-2016, 06:48   #5
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Re: Chain Stopper Vs Devil's Claw

most . real cruising yachtsmen I See use some sort Of nylon Bridal on their anchor chain. this greatly reduces the stress on the boat and makes your boat more comfortable at anchor. I am not in love with the Devil's claw as I don't believe they're that strong. But there are several good chain hooks on the market
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Old 26-04-2016, 07:03   #6
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Re: Chain Stopper Vs Devil's Claw

Skip Novak has a video that shows the sampson post being used to take the load off the windlass...
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Old 26-04-2016, 07:09   #7
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Re: Chain Stopper Vs Devil's Claw

Quote:
Originally Posted by Dockhead View Post
I don't really like using the forestay chainplate for ground tackle...
I'm not familiar with your foredeck, so I don't know why you would even mention this. I agree with you, and would not attach ground tackle to this chainplate.

Quote:
Originally Posted by Dockhead View Post
With a samson post this would already be better, and maybe some different type of hook or claw which is more secure, maybe the Mantus chain hook or maybe someone makes a yacht-sized devil's claw in stainless.

I wouldn't use nylon here because it wouldn't be long enough to give any shock protection, and you don't want any risk of chafe at this particular attachment
The Mantus chain hook is a very secure means of attaching to the chain. We have the unit for half-inch chain and it is a massively strong piece of gear.

I like snubbers, and use a bridle of 5/8 inch three strand secured to cleats on deck. I keep two lengths of firehose on the bridle for chafe protection where the line goes through the fairleads.

I'm trying to visualize how a snubber would be attached to a samson post on your boat, and maybe this is your concern. I can see that attaching three strand to your samson post will expose the rode to chafe on the forestay, bow pulpit, anchor roller, and whatever else is up there. Perhaps you can explain this in more detail.

Cheers!

Steve
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Old 26-04-2016, 07:37   #8
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Re: Chain Stopper Vs Devil's Claw

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Originally Posted by motion30 View Post
most . real cruising yachtsmen I See use some sort Of nylon Bridal on their anchor chain. this greatly reduces the stress on the boat and makes your boat more comfortable at anchor. I am not in love with the Devil's claw as I don't believe they're that strong. But there are several good chain hooks on the market
Good point, but we are assuming in this case that the normal snubber, or bridle has broken, so our last line of defence is some sort of chain stopper, backup short snubber or the windlass itself. And if the snubbers broken its pretty nasty, so the shock loads get pretty extreme, enough to break chains, bend shafts on windlasses or worse.

I am just doing some back of envelope calc's now.

With a 7000kg boat moving at 1.5 knots backwards we have to absorb near 2000joules of energy.

50 meters of bar tight 8mm chain will stretch approx 0.25m This will only absorb about 1400 joules. Thats if the rough E number of 55gpa is close and it doesn't yeild which it probably will as its going to see about 2700kg of load. (It also assumes my calcs are vaguely correct and I havent made some stupid mistake!)

A 1 meter length of 16mm nylon used as a short backup snubber will stretch about 20% at this load (about half its break strain)so add another 0.2m. So its stretch will nearly double the energy absorbed over what the chain alone can cope with.

Hopefully in the real world the catenary will soak up much of the energy, and also the anchor will slip slightly as well diving deeper to also soak up some more, and our gear will survive apparently unharmed, but probably with some of its fatigue life used up.
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Old 26-04-2016, 07:50   #9
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Re: Chain Stopper Vs Devil's Claw

Quote:
Originally Posted by Snowpetrel View Post
The way I figure it, in this scenario any stretch is significantly better than the nearly inelastic chain. Ive broken an anchor chain twice, the snatch was like the boat hitting rocks as the chain lot all catenary. If you had 1 meter of nylon its going to stretch 10-20% safely, giving 100-200mm of stretch. Chafe isnt a big issue, as it shouldnt rub on anything, and even can be covered in chafe gear/anti uv over its whole length.



They jam closed under load. Maybe you could rig a line back to a winch and take the tension off it, but in the worst case scenario thats going to be hard, as the load will be extreme. Especially if you are singlehanded.

A rope can be cut easily in this scenario. Admittedly it is a pretty unlikely scenario if you practise decent seamanship and avoid getting caught on a nasty lee shore in hurricane conditions with a failed windlass!

Also it can be hard to set up a chain stopper that leads fair onto some windlasses, and its another fitting to buy, maintain, stub you toe on, leak etc.
OK, very useful!

All of these comments seem very reasonable! Duly absorbed, thanks.
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Old 26-04-2016, 07:52   #10
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Re: Chain Stopper Vs Devil's Claw

Quote:
Originally Posted by motion30 View Post
most . real cruising yachtsmen I See use some sort Of nylon Bridal on their anchor chain. this greatly reduces the stress on the boat and makes your boat more comfortable at anchor. I am not in love with the Devil's claw as I don't believe they're that strong. But there are several good chain hooks on the market
No one suggested using a chain stop (or devil's claw) as a substitute for a snubber.

Two very different functions, which cannot be performed by the same device!
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Old 26-04-2016, 08:07   #11
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Re: Chain Stopper Vs Devil's Claw

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Originally Posted by steve77 View Post
I'm not familiar with your foredeck, so I don't know why you would even mention this. I agree with you, and would not attach ground tackle to this chainplate.



The Mantus chain hook is a very secure means of attaching to the chain. We have the unit for half-inch chain and it is a massively strong piece of gear.

I like snubbers, and use a bridle of 5/8 inch three strand secured to cleats on deck. I keep two lengths of firehose on the bridle for chafe protection where the line goes through the fairleads.

I'm trying to visualize how a snubber would be attached to a samson post on your boat, and maybe this is your concern. I can see that attaching three strand to your samson post will expose the rode to chafe on the forestay, bow pulpit, anchor roller, and whatever else is up there. Perhaps you can explain this in more detail.

Cheers!

Steve
I didn't mention the snubber at all, which is a completely different subject, but since you asked:

On my present boat I do cow-hitch the snubber onto my inner forestay chain plate and lead it over the second bow roller. There's no chafe on anything -- it works pretty well.

Unless I need some spring off the chain, in which case the snubber goes over the rail via a bow cleat. Still no chafe except at the rail, where there are simple stainless rub strips instead of fairleads, which I consider to be poor. The next boat will have short bulwarks and chocks or freeing ports and proper fairleads, and the snubber will be lead through those.


This is entirely separate from the devil's claw arrangement I have to belay the chain. This is a short length of stainless chain shackled to the inner forestay chainplate, with a forged chain hook at the other end, which grabs the chain between the windlass and bow roller.

This also works pretty well, but I don't feel completely secure with the chain hook (it's strong but could fall off if the chain goes way slack), and now on top of that I've absorbed Snowy Petrel's comments about snatch loads and being able to cut it away in an emergency, so I think I'm going to change to a short very strong strop made of nylon rope. It would need to be 24mm, and I guess I could splice thimbles on both ends, but I'd like to find a better hook to use.
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Old 26-04-2016, 08:23   #12
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Re: Chain Stopper Vs Devil's Claw

I have a chain stopper that I have yet to install, I think it's the Lewmar on, but may be Maxwell.
Anyway even if I drill all the way through my bowsprit and use a backing plate, I don't see it being capable of doing much more than ensuring the anchor stays in place. I originally bought it to be used as a lunch hook kind of thing, as in I'm only anchoring for a couple of hours and don't want to bother with the snubber.

Now I'm wondering truthfully if it has much use at all, since I now tie the anchor roll bar to the rail cause it fell off in a knock down once.
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Old 26-04-2016, 08:33   #13
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Re: Chain Stopper Vs Devil's Claw

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I have a chain stopper that I have yet to install, I think it's the Lewmar on, but may be Maxwell.
Anyway even if I drill all the way through my bowsprit and use a backing plate, I don't see it being capable of doing much more than ensuring the anchor stays in place. I originally bought it to be used as a lunch hook kind of thing, as in I'm only anchoring for a couple of hours and don't want to bother with the snubber.

Now I'm wondering truthfully if it has much use at all, since I now tie the anchor roll bar to the rail cause it fell off in a knock down once.
Just be sure to attach the chain strongly to the boat. The snubber doesn't do that (it is subject to chafe, and it is anyway not as strong as your chain). So you need another means, if not a chain stopper, then a strong strop like we've been discussing here.
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Old 26-04-2016, 08:36   #14
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Re: Chain Stopper Vs Devil's Claw

I don't have a chain stopper. There isn't room for one on my foredeck.

Instead I have a strop made of a short length of heavy nylon rope with a chain hook on one end and a spliced loop on the other end. The loop goes to a convenient cleat that is securely backed and the chain hook grabs the chain about 24 inches behind the bow roller. With the strop in place and a bit of slack between the windlass and the chain hook the load is removed from the windlass.

It dead simple and inexpensive.


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Old 26-04-2016, 08:50   #15
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Re: Chain Stopper Vs Devil's Claw

Burst strength for 5/8 nylon three stand I think is about 12,000 lbs. I run two lines but I know load is not always split evenly.
I believe the WLL for grade 43 5/16" chain that I have is 3,900 lbs and that breaking point for grade 43 chain is three times WLL? If so that means my chain is only good for 11,700 lbs. or about the same as the line.
Either way I don't think a stopper will hold against anything that will burst the nylon line, gotta think the shock load would rip it out if nothing else?
I would think a second line would be the way to go, first line bursts, second catches it, allowing you to set a third?
I wonder if the average dock cleat would hold? If a Sampson post were very well secured, surely nothing would be stronger than that?
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