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Old 25-04-2016, 17:53   #61
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Re: Chain Stopper Installation Questions

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Old 25-04-2016, 18:08   #62
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Re: Chain Stopper Installation Questions

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Originally Posted by Jim Cate View Post
Are you quite sure about this bonding issue? I'd think that one could bond a chunk of 6061 Al quite securely, and that it would make a fine mounting pad or backing plate. I've used such before without problems, although an isolating gasket between s/s and the alloy is a good idea.

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Jim,

No question you can use aluminium plate though I would go with a higher corrosion resistance alloy than 6061 and take the trade off for the rigidity.

But..... And this is nit pickie...

G10 is better in compression lighter, has no corrosion comparability with stainless bolts, is cheaper, and can be tapped.

I have installed a lot of aluminium and stainless backing plates over the years, but by preference I won't use anything but G10 or the equivilant carbon plates anymore. It's just so good at what it does it has become hard to justify using anything else. Luckily it has become so ubiquitous that you can find it laying around as scrap in most boat yards.


I am not sure why there is so much general resistance to the stuff. It's almost textbook ideal as a backing plate. It's so good, even carbon plate is difficult to justify in most applications, the few grams of weight and the marginal stiffness gained isn't worth the conductive issues of carbon. Which is why A-Cats generally use G-10 as backers.
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Old 25-04-2016, 19:13   #63
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Re: Chain Stopper Installation Questions

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We just use a chain hook attached to a cleat with a few feet of dyneema.
What a snubber should do is stretch under load. Dyneema does not stretch like nylon 3 strand. Should be a lot longer as well.
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Old 25-04-2016, 19:17   #64
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Re: Chain Stopper Installation Questions

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Originally Posted by mitiempo View Post
What a snubber should do is stretch under load. Dyneema does not stretch like nylon 3 strand. Should be a lot longer as well.
He did not speak of a snubber at all so must be a chain stopper. I agree that his setup is better than what most suggest, which are (sacrificial) snubbers.
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Old 25-04-2016, 20:39   #65
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Re: Chain Stopper Installation Questions

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What a snubber should do is stretch under load. Dyneema does not stretch like nylon 3 strand. Should be a lot longer as well.

The dynemma/hook is just our chain stopper. We still use a snubber/hook to limit shock load.

Here's our anchor process:

Release anchor to seabed
Slowly reverse while paying out chain
Hook the dyneema/hook to chain
Back down on anchor
Let off throttle which typically unloads the chain
Unhook dyneema/hook stopper
Attach snubber/hook
Let more chain out until loop of chain between windlass and snubber
reattach dyneema/hook stopper
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Old 25-04-2016, 21:01   #66
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Re: Chain Stopper Installation Questions

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Originally Posted by funjohnson View Post
The dynemma/hook is just our chain stopper. We still use a snubber/hook to limit shock load.

Here's our anchor process:

Release anchor to seabed
Slowly reverse while paying out chain
Hook the dyneema/hook to chain
Back down on anchor
Let off throttle which typically unloads the chain
Unhook dyneema/hook stopper
Attach snubber/hook
Let more chain out until loop of chain between windlass and snubber
reattach dyneema/hook stopper
I understand.
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Old 25-04-2016, 23:05   #67
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Re: Chain Stopper Installation Questions

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Snip

I am using oak as that is the most suitable wood I have handy - is there a better material to use that is fairly easy to obtain (small town Vancouver Island but Home Depot not too far away)?
One of the most under rated pieces of load spreading materials is cheap nylon breadboards available at most two dollar shops. They are very tough, relatively cheap and require no ongoing painting, sanding or polishing. One or two (laminated) of them might be a very easy option.
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Old 26-04-2016, 07:29   #68
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Re: Chain Stopper Installation Questions

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Originally Posted by funjohnson View Post
We just use a chain hook attached to a cleat with a few feet of dyneema.

++1.
Same on my boat. Why complicate things with another piece of hardware? Much more comfortable having dyneema, a chain hook, and a well supported bow cleat as a backup in case snubber breaks. That rare but possible incidence is exactly when you need a bulletproof, not questionable, attachment


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Old 26-04-2016, 07:31   #69
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Re: Chain Stopper Installation Questions

And yes the above is a stopper as backup for snubber. I only use it alone for a quick stop in clear weather and no significant breeze or chop


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Old 26-04-2016, 08:02   #70
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Re: Chain Stopper Installation Questions

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Originally Posted by ozskipper View Post
One of the most under rated pieces of load spreading materials is cheap nylon breadboards available at most two dollar shops. They are very tough, relatively cheap and require no ongoing painting, sanding or polishing. One or two (laminated) of them might be a very easy option.
The reason why not to use them is spelled out in some detail in posts above... These plastic cutting boards are HDPE and are junk in this application.

They do make great skid plates for dragging the anchor chain around however.
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Old 26-04-2016, 08:06   #71
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Re: Chain Stopper Installation Questions

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Originally Posted by s/v Jedi View Post
He did not speak of a snubber at all so must be a chain stopper. I agree that his setup is better than what most suggest, which are (sacrificial) snubbers.
Snubbers are only sacrificial if poorly designed. They should be sized long enough (nearly a boat length) to reduce all loads to within a working load they can endure for years. Chafe is also reduce by the reduced load, and chafe gear manages the rest. Rather like calling tires sacrificial because they only last a few years. Functional would be more apt.

Short snubbers tend to be sacrificial, since they are not long enough to dissipate energy. They chafe, heat, and fail. Very predictable, in fact, unless they are monsterouly strong and used as stoppers, which is also smart and has been suggested.

The thing is to remember that there are 3 classes of snubbers:
1. long and shock absorbent.
2. short, not extending beyond the chocks or rollers and used as stoppers
3. snubbers that are going to fail from chafe or heating

Using a sort bit of Dyneema as a stopper is a completely different case.
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Old 26-04-2016, 21:05   #72
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Re: Chain Stopper Installation Questions

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Originally Posted by thinwater View Post
Snubbers are only sacrificial if poorly designed. They should be sized long enough (nearly a boat length) to reduce all loads to within a working load they can endure for years. Chafe is also reduce by the reduced load, and chafe gear manages the rest. Rather like calling tires sacrificial because they only last a few years. Functional would be more apt.

Short snubbers tend to be sacrificial, since they are not long enough to dissipate energy. They chafe, heat, and fail. Very predictable, in fact, unless they are monsterouly strong and used as stoppers, which is also smart and has been suggested.

The thing is to remember that there are 3 classes of snubbers:
1. long and shock absorbent.
2. short, not extending beyond the chocks or rollers and used as stoppers
3. snubbers that are going to fail from chafe or heating

Using a sort bit of Dyneema as a stopper is a completely different case.
No, your snubber will be ripped to shreds in minutes during hurricane conditions. The chafing is internal, inside the rope, amongst the fibers themselves as the snubber stretches. This melts the nylon or polyester until the outer layer of fibers is too thin for the load and it snaps. This is documented many times and everybody should know it and make sure they are secure.
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Old 26-04-2016, 21:27   #73
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Re: Chain Stopper Installation Questions

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Originally Posted by s/v Jedi View Post
No, your snubber will be ripped to shreds in minutes during hurricane conditions. The chafing is internal, inside the rope, amongst the fibers themselves as the snubber stretches. This melts the nylon or polyester until the outer layer of fibers is too thin for the load and it snaps. This is documented many times and everybody should know it and make sure they are secure.
Again, it comes down to proper sizing. I said that the rope had to be working within the correct range. What you have described is a design error. If the line is working hard enough to heat, obviously it is either too short to absorb the energy (very common fault--one boat length required) or undersized. This is obvious.

I've not anchored in a hurricane, but I have worked with oil equipment moorings in hurricanes, and they are fiber, not chain. It is all about the design.
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Old 27-04-2016, 00:43   #74
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Re: Chain Stopper Installation Questions

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Originally Posted by thinwater View Post
Again, it comes down to proper sizing. I said that the rope had to be working within the correct range. What you have described is a design error. If the line is working hard enough to heat, obviously it is either too short to absorb the energy (very common fault--one boat length required) or undersized. This is obvious.

I've not anchored in a hurricane, but I have worked with oil equipment moorings in hurricanes, and they are fiber, not chain. It is all about the design.
I'm not attempting to be flippant with the following, but rather, would genuinely like to know. Where does one look to find the (proven) math, in order to design such?
As common sense would dictate that a snubber which well in 40kts, won't do so in 60kts or 80kts. And one can't easily (if at all) go & swap them out in such conditions.

Especially if it involves, say, snaking out onto the thin bows of a tri's amas under such conditions, in order to switch to a different bridle. Or to replace one which has failed, or is about to.

I know that Yale (& some others) have specially designed mooring pendants for attaching one's boat to a mooring in heavy weather. But that's a bit different than a snubber. In terms of both; design, & materials used.
Not to mention the cost of said pendants. Ouch!
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Old 27-04-2016, 07:10   #75
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Re: Chain Stopper Installation Questions

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I'm not attempting to be flippant with the following, but rather, would genuinely like to know. Where does one look to find the (proven) math, in order to design such?
As common sense would dictate that a snubber which well in 40kts, won't do so in 60kts or 80kts. And one can't easily (if at all) go & swap them out in such conditions.

Especially if it involves, say, snaking out onto the thin bows of a tri's amas under such conditions, in order to switch to a different bridle. Or to replace one which has failed, or is about to.

I know that Yale (& some others) have specially designed mooring pendants for attaching one's boat to a mooring in heavy weather. But that's a bit different than a snubber. In terms of both; design, & materials used.
Not to mention the cost of said pendants. Ouch!
Exactly, if the snubber survives hurricane conditions, then it does not do it's job during "normal" conditions. It must stretch to absorb the shocks and this stretch is what does the internal chafing. If you go up in size, or change to Dyneema, then it may not break during a hurricane but it also doesn't do it's shock absorbing in 20-25 knots of wind.
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