Chain snubbers

[capta]

I spliced my own dyneema loops (sling) for this purpose, and use them to form a prussik knot on the anchor rode and attach the loops with a large stainless spring-gated hook on the bridle/snubber lines. (1/4" dyneema has a breaking strength >5,000 pounds)
The hooks I use are more reliable than the D-shackle @thinwater shows, and quick to use one-handed. I use the largest size Wichard snap hook (it has a 3168 pound WLL)
This works on chain or rope rode, I use more than one loop wrap on the prussik when using rope rode, to avoid slippage.

What's the elasticity of the Dyneema? With nylon running @ around 30% there's little to no shock as the boat comes up tight on the tackle. Strength is not what I'm looking for in a snub line, but rather elasticity so that strength becomes secondary.
In your post it seems you are adding a weak link in the whole setup, even with the largest size Wichard snap hook, that is still thousands of pounds inferior to the Dyneema.

 

[dLj]

Really excellent discussion. I'm very much enjoying it and there is a lot of information here.

@Stu Jackson - easy now, I wasn't talking about letting out more scope if another boat is dragging down onto me. Only if my anchor is not holding correctly - likely due to insufficient scope. See @thinwater post above. Spot on!

I am really liking the - not sure what to call it - the secure wrap around the chain. One thing I really like is I can use that and then play with a single line snubber or two lines in a bridal on my boat and see which works best. I currently have a 3 strand nylon line that is 100 meters long and is about 7/8 inch. It's actually metric and I don't remember the size. I bought it years ago in Europe, it's a very high quality line. I've used it infrequently in all the years I've owned it so its still in very good condition. I would feel it would be a great line to cut in two and begin using it as my snubber using the system both @thinwater and @dlochner have shown. I only need to make that attachment piece. I can then play with attaching if in the bridal form to both my bow cleats, and my midships cleats to see which works better. Nice!!!! And of course, if the single line is better, or good, I can just stop there and I'd have a backup snubber. Sounds win-win to me!

dj

 

[Davidasailor26]

Really excellent discussion. I'm very much enjoying it and there is a lot of information here.

I’m learning a lot too and rethinking the options available for my chain/rope combination and windlass.

 

[Captain Larry-DH]

What's the elasticity of the Dyneema? With nylon running @ around 30% there's little to no shock as the boat comes up tight on the tackle. Strength is not what I'm looking for in a snub line, but rather elasticity so that strength becomes secondary.
In your post it seems you are adding a weak link in the whole setup, even with the largest size Wichard snap hook, that is still thousands of pounds inferior to the Dyneema.

You didn’t understand what I’m doing...
First, the dyneema loops are only about 12” long. They are used to form a prussic knot around the rode, and the snap hook is spliced to the (nylon) bridle permanently, to attach the dyneema loops - easy to snap on and off the loops. One loop for each side of the bridle, and one hook for each loop. (It could be done with a single hook spliced to both legs of the bridle, but that’s not the way I have used it).
Second, let’s discuss WLL. Grade 43 anchor chain in 3/8” has a WLL about 5400#. 5/16” Grade 43 high test chain is about 3900#. A pair of snap hooks such as I used is equal to the task, (either type of chain) at a WLL of 3100# each. x2=6400#
If my anchor is able to hold well enough to test those limits I’d be very thankful. At that point I’d be more concerned about my life (if aboard), and my insurance coverage than anything else.

 

[Blitz]

Why would you put a snubber on rope rode?

I would think the snubber on a rope rope would allow the use of a bridle to go to each of your deck cleats in lieu of going straight over your roller. rollers beak....

 

[Captain Larry-DH]

I would think the snubber on a rope rope would allow the use of a bridle to go to each of your deck cleats in lieu of going straight over your roller. rollers beak....

…And more importantly to relieve the pull on the windlass.

 

[Bob S]

I have been using a soft shackle for the past three seasons and it will pass through my windlass if I needed to retrieve it in a hurry. I am using three strand nylon. Curious if there is a rule of thumb on your snubber length? Does the soft shackle or chain hook need to go below the waterline? In my case, would it be better to use a thimble or just an eye splice to attach a soft shackle?

 

[jssailem]

Curious if there is a rule of thumb on your snubber length?

Funny you should ask this question.

Not sure about a rule of thumb. I considered a reasonable length to get the chain away from the bow, and have enough nylon to cushion the action. Ended up with a number 25-35 ft. on my 35ft boat.

Then I read this by John Harries on his Attainable Adventure Cruising website morganscloud.com.

"So I recommend a 30-foot snubber, regardless of boat size. Note that the snubber itself should be about 45 feet long to allow for knotting and cleating."​

The info might work for you.

 

[capta]

You didn’t understand what I’m doing...
First, the dyneema loops are only about 12” long. They are used to form a prussic knot around the rode, and the snap hook is spliced to the (nylon) bridle permanently, to attach the dyneema loops - easy to snap on and off the loops. One loop for each side of the bridle, and one hook for each loop. (It could be done with a single hook spliced to both legs of the bridle, but that’s not the way I have used it).
Second, let’s discuss WLL. Grade 43 anchor chain in 3/8” has a WLL about 5400#. 5/16” Grade 43 high test chain is about 3900#. A pair of snap hooks such as I used is equal to the task, (either type of chain) at a WLL of 3100# each. x2=6400#
If my anchor is able to hold well enough to test those limits I’d be very thankful. At that point I’d be more concerned about my life (if aboard), and my insurance coverage than anything else.

I've always been curious why anyone would buy any chain other than anchor chain, BBB, made exclusively as anchor chain. Under no circumstances can any chain we put on our vessels be strong enough to hold our boats, high test or not. Without a snub, in the right circumstances, our chain will break. I've had it happen, under relatively mild circumstances (wind shift onshore in Hanalei Bay). Thereafter I've always used a snub on all but line rode.

 

[sesmith]

Curious if there is a rule of thumb on your snubber length?

Here's the Practical Sailor take on that. I bet thinwater could probably comment on any questions.

One thing I did notice is I believe the weight in the line diameter formula should be weight in 1000 lb increments not weight in pounds. (or I'd need a pretty hefty snubber for our boat).

What is Ideal Snubber Size? - Practical Sailor

Since 1974, Practical Sailor’s independent testing has taken the guesswork out of boat and gear buying.

www.practical-sailor.com

 

[Bob S]

As I understand a 30-40' snubber is appropriate but if I'm anchored in 15-20' (4' tide) you would lay out 20-25' which means it will be lying on the bottom in calm conditions.

 

[Captain Larry-DH]

I've always been curious why anyone would buy any chain other than anchor chain, BBB,

The reason I cited WLLs for Grade 43 is because it's stronger than standard grades of steel chain, and you were questioning my choice of snap hook based on strength. I like them because they are quick to use one-handed, and they work. You can use whatever. There are so many variables to keeping one's boat in place in the real world that any discussion is academic.

 

[thinwater]

A bunch of things.

• Roller vs. chocks. This depends on the boat. However, if the roller is not strong enough to withstand anchoring loads (break-out is more than storm loads) then it is weak and you should route things through the chocks. But I think this is a boat-specific decision that depends on geometry and construction details. Alos, obviously, whether chocks or roller has no influence on unloading the windlass; the snubber is not secured to the windlass in either case. A misunderstanding, I think.
• Dyneema attachments. I hope it is obvious that Dyneema bits used to grab the chain or fight chafe are only a tiny portions of the length and have little effect on shock absorption. They are only 1-2 feet long, so add 1-2 feet of snubber.
• Snubber touching the bottom. First, if a multihull with a proper bridle (typically beam-long legs, so it hangs 10-20 feet below the boat) anchors in shallow water (often as little as 5-8 feet), the bridle will ALWAYS touch in slack winds. We use a locking attachment and it is not a problem. There is no chafe in no wind. It lifts the instant there is a 2-knot breeze. Remember, the snubber has no mass and it does not take much to lift 2 links of chain. Simply, this has proven not to be an issue. Second, no one said the 45 feet of snubber had to be secured to the bow chocks. Attach it to the mid-ships or stern cleats and add some chafe gear (the rope slides inside the gear) where it passes over the bow chocks. I did this on my PDQ cat for many years. Neeves turned me on to the idea. He actually uses pulleys.
• Type of chain. High strength chains actually have considerably MORE ability to absorb impact than grade 30/BBB. This is why only high grade chains are permitted for transport and overhead lifting. Seem obvious. They are stronger steel, that can flex like a spring, before breaking. The notion that high grade chain is somehow brittle is incorrect and counter to industrial and regulatory history. BBB is traditionally anchor chain... but most likely that tradition is becoming obsolete as high grade chains become more available. There is a LOT more industrial experience, in extremely abusive fields like logging, than there is in sailing. If BBB held up better, you know they would use it. It does not.

 

[dLj]

As I understand a 30-40' snubber is appropriate but if I'm anchored in 15-20' (4' tide) you would lay out 20-25' which means it will be lying on the bottom in calm conditions.

Precisely why I do not like the hook option.

dj

 

[NotCook]

(1/4" dyneema has a breaking strength >5,000 pounds)
The hooks I use are more reliable than the D-shackle @thinwater shows, and quick to use one-handed. I use the largest size Wichard snap hook (it has a 3168 pound WLL)

This raises a point that has always been unclear to me. How does one know what forces are placed on anchor chains and moorings? How do vessel size and/or displacement relate to the forces in ground tackle?

 

[thinwater]

This raises a point that has always been unclear to me. How does one know what forces are placed on anchor chains and moorings? How do vessel size and/or displacement relate to the forces in ground tackle?

Not a simple question. ABYC H40 table 1 (Google) is the max in a worst case (no snubber, shallow water, non-breaking wave exposure, and some yawing) and 1/4 of that figure is about the wind load (and rode tension is always more than that).

 

[thinwater]

Snubber hooks/soft shackles etc. need to match the snubber, not the rode. If you use a fat snubber this might be the same, but for most of us it is somewhat less.

 

[dLj]

This raises a point that has always been unclear to me. How does one know what forces are placed on anchor chains and moorings? How do vessel size and/or displacement relate to the forces in ground tackle?

To @thinwater point above, I posted the tables from H1 here:

Anchoring systems

As I'm in the midst of rebuilding my entire anchoring system, I went to the ABYC Standard H40 "Anchoring, Mooring, and Strong Points". For my boat, I need to be using design loads of 4800 pounds. Nothing about this boat seemed to demand anything "unusual". But when I read the standard and...

forums.sailboatowners.com

(Hope that link works)

dj

 

[thinwater]

Originally the columns were labeled 15 knots, 30 knots, and 42 knots, but that designation was changed about 20 years ago.This was sustained wind, not gusts. Since force ~ V^2, you will see this fits the numbers. (30^2/15^2) is 4 times. (42^2/30^2) is 1.96, or about double.