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Old 18-05-2011, 15:02   #1
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Chain Snubber

Our boat is about 20,000 lbs loaded, and I have a couple of questions about snubber.

What size and length of line should be used for chain snubber?

Nylon or braided?

Good types of chain hooks?

Is there a general rule of how much slack should be used in the line to the chain?
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Old 18-05-2011, 15:15   #2
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Re: Chain Snubber

Use a LONGER snubber (± 50'), of 3-strand Nylon, 1 or 2 sizes smaller than your appropriate rope rode.
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Old 18-05-2011, 15:17   #3
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Re: Chain Snubber

We use two Shockles and a plate with a notch for the chain and about 10 feet of line on each side. About four feet of chain hangs loose inside this set up.
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Old 18-05-2011, 15:23   #4
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Re: Chain Snubber

I prefer NER Mega braid nylon for its high stretch and great handling. About 30' is a balance between stretch and practicality, and assuming you have the chain fixed on deck as a backup, you could go as small a 1/2", unless it is a severe blow. If you go too large on your snubber, it looses elasticity. (You could have a larger one for when really bad weather is predicted). For attachment, use a rolling hitch or chain FORK, as it keeps the links from turning sideways, like a chain hook does. (Photo is safety).
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Old 18-05-2011, 15:24   #5
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Re: Chain Snubber

There are many different opinions on what makes the best snubber, here is my take on it. The snubber serves two purposes, to take the load off of the windlass and to provide shock absorption in conditions requiring it.

To take the load off of the windlass, any line and hook combination that will not fail will do the trick. This is a matter of having sufficiently heavy duty components and having good enough shock absorption to lower the loads.

For shock absorption, the key is to have sufficient stretch in the system. The factors that effect the force/deflection curve of a line are the line type (braided vs 3 strand), the line material, the line diameter and the line length. 3 strand nylon has good stretch characteristics and it is relatively cheap. Smaller diameter lines have greater stretch for a given force as do longer length lines. Personally, I advocate having 2 snubbers, a regular use one and a storm one. The regular use one could be something like 1/2-5/8" and be something like 30-40' long. This will work for almost all conditions strengthwise and if you let it all out, it will have enough stretch. For storm conditions, I like to have a line that would be the equivalent diameter (3/4-1") to the anchor line that I would use if I had a combination rode so that it is sufficiently strong. Since the line will be relatively stiff at this larger diameter, make sure that you have enough of it (50'+ isn't a bad idea). If you have too lightweight of a setup and a storm comes, you will part your snubber putting the load on the windlass (unless you have a chain stopper) and eliminating all shock absorption. However, this storm setup is overkill in most conditions and doesn't absorb shock well. Having extra length will never hurt you, you don't need to put it out and you can tune the snubber for the given conditions.

If you want to get technical, you can look up force/deflection data for different line types and then play around with how much length you need to get a given stretch at a given load. There are a few online rode calculators that you can do this with and just simply plug in a combination rode.

There are many types of chain hooks but the best type if you can find a suitable one is a devil's claw. If you don't mind constantly fighting rust, using a high quality alloy chain hook from someone like McMasterCarr works well also. Some of the hooks that are sold specifically for the marine market are undersized and will bend under a large load.
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Old 21-05-2011, 16:54   #6
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Re: Chain Snubber

What do you think of those rubber Mooring Snubbers that are used on dock lines? Would they help any with snubber lines?
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Old 22-05-2011, 00:45   #7
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Re: Chain Snubber

my favourite design:







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Old 22-05-2011, 00:50   #8
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Re: Chain Snubber

I have another question regarding windlass specs. My SL-Horizon 900 windlass specs says that it has a Maximum Pull of 900 lbs, and a Recovery Load of 110 lbs. If my chain, rode, and anchor weighs 300 lbs will this windlass do the job?
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Old 22-05-2011, 01:18   #9
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Re: Chain Snubber

I have three strops on board. One long heavy snubber for rougher conditions, one light shorter snubber for lighter conditions, and one safety line.

The heavy snubber is I think 22mm nylon octoplait, about 10 meters long, and the light snubber is 16mm nylon octoplait and 6 meters long. The safety line is two meters of regular three-strand nylon with a chain hook. My boat displaces 44,000 pounds light ship.

I do not personally believe in chain hooks on snubbers. I feel that a rolling hitch is more secure, and it passes over the bow roller so it can be rigged and unrigged on deck. Chain hooks on snubbers are solutions to problems which do not exist, IMHO.

I do use a chain hook for my safety line, which I attach to the chain between the windlass and the bow roller to make sure that loads don't get to the windlass in case the snubber breaks (which has happened to me). The necessity of a safety line irritates me -- when did they stop putting samson posts on cruising boats? I wish I had a samson post and a big horizontal windlass, instead of the namby-pamby cruising boat setup I have.

I have 100 meters (330 feet) of 12mm anchor chain and I have found that the catenary of this heavy chain (I'm used to 8mm) has a strong dampening effect. So perhaps the snubber is less crucial, the heavier the chain. I spent all night at anchor in a storm once and didn't notice that the snubber had broken. I had a lot of chain out and the sheer weight of it (the whole rode weighs almost 800 pounds) seems to have dampened the snatching enough.

But still, I snub religiously, and will put on both of them if the conditions are dodgy.

Be careful about chafe on your snubber (don't ask me how I know!). I have learned (the hard way) to lead mine over the second bow roller.
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Old 22-05-2011, 01:46   #10
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Re: Chain Snubber

Quote:
Originally Posted by JiffyLube View Post
I have another question regarding windlass specs. My SL-Horizon 900 windlass specs says that it has a Maximum Pull of 900 lbs, and a Recovery Load of 110 lbs. If my chain, rode, and anchor weighs 300 lbs will this windlass do the job?
The rule of thumb many peope use is that the windlass maximum pull should be at least three times the total weight of your ground tackle. It sounds like you are barely within that guidline. Lewmar, however, says 4x. Since Lewmar exaggerate the "maximum pull" of their windlasses, this factor may be unique to them. My Ocean 3 windlass has advertised maximum pull of 1700kg and my ground tackle weighs 385kg so I'm inside the 4x limit with a bit of margin. In fact it works ok -- seems powerful enough.

I don't know what "recovery load" is. Actual practical working load? You will not typically be pulling up the entire weight of your anchor and entire chain since you will not likely have it all out in water deeper than the length of your chain, so perhaps there is no contradiction here.

I think you'll probably just have to live with your windlass a new ground tackle for a while and see if the windlass seems powerful enough in real life.
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Old 22-05-2011, 02:49   #11
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Re: Chain Snubber

Hooks can and do come undone when the boat moves around. I used a hook recently and it just let go when a squall came through. As a result, the chain started going out slowly again. I kept the brake slightly loose to allow for this just in case, and it happened. I much prefer a rolling hitch. Never known to let go.

I snub the chain to a mooring cleat from the side to avoid putting load on the bowsprit. I use a lot of chain all the time so there is a lot of damping by the sheer weight of the chain (as dockhead above explains) , but much better sailors than me tell me it is best to use nylon rope for this function.
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Old 22-05-2011, 06:17   #12
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Re: Chain Snubber

I have about a meter of 3 strand nylon over the bow roller. I don't like the rope being in the water as its used so much that I don't want barnicles (etc) to grow inside it and weaken it.
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Old 22-05-2011, 10:12   #13
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Re: Chain Snubber

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Originally Posted by Dockhead View Post
The rule of thumb many peope use is that the windlass maximum pull should be at least three times the total weight of your ground tackle. It sounds like you are barely within that guidline. Lewmar, however, says 4x. Since Lewmar exaggerate the "maximum pull" of their windlasses, this factor may be unique to them. My Ocean 3 windlass has advertised maximum pull of 1700kg and my ground tackle weighs 385kg so I'm inside the 4x limit with a bit of margin. In fact it works ok -- seems powerful enough.

I don't know what "recovery load" is. Actual practical working load? You will not typically be pulling up the entire weight of your anchor and entire chain since you will not likely have it all out in water deeper than the length of your chain, so perhaps there is no contradiction here.

I think you'll probably just have to live with your windlass a new ground tackle for a while and see if the windlass seems powerful enough in real life.
I did a search for the words "Recovery Load" myself before asking, and some of the links pointed me to the Lewmar website and their manuals. I was thinking that maybe "Recovery Load" was the same thing as "Working Load", so that got me wondering if it was or not.

One site dealing with Deck Machinery defined Recovery Load as "the maximum rope pull (in kN), measured at the drum commences to rotate in the direction of haul, the prime mover being set for maximum torque under automatic control and the rope being wound on the drum in a single layer."
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Old 22-05-2011, 10:33   #14
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Re: Chain Snubber

My boat is around 22,000 and I have always used a 3/8" three-strand nylon snubber and it has never broken--used in up to 56 knots so far. Gives a lot of stretch in a short length. Typically, if nothing more than 20-30 knots is expected I only let out enough snubber to just reach the water, and that is all I need. I make sure that there is a big loop of chain so that there is no snatching back on the chain. In greater winds I'll let out a longer length of snubber line, but rarely more than about 20 feet or so. With the 3/8" nylon that gives me all the bounce I need in even pretty severe conditions. Rolling hitch works great, but I also use a chain hook for its speed of use. If the snubber is short enough to stay off the bottom the chain hook doesn't come loose as the weight of the chain will keep it secure.

On my previous boat, a 32-foot cat, I used the same 3/8" snubber line for more than 10 years, left outside on deck in the sun 365 days a year, and no chafing gear! Went through a hurricane, a tornado, numerous gales, etc. in that time. It ended up being an experiment in how long it would last. I eventually moved the same old snubber to my new boat and it eventually broke right at the chain hook--I had just passed the line through the eye of the hook with no thimble or anything, tied it on with a bowline. This indicates to me that anchor loads are a lot lower than the ABYC guidelines.
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Old 22-05-2011, 11:05   #15
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Re: Chain Snubber

Third using a rolling hitch to attach the snubber. Tried a chain hook but it kept coming undone unless I lashed it to the chain which defeated the whole purpose of the hook. Went to rolling hitch which worked without a problem for 24/7/52 anchoring for more than a year.
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