What's the right amount of chain loop with a snubber?

[Paul L]

Pelagic,
Interesting thought to dump excess chain to dampen the bow slewing around. I have seen the chain get wrapped around the 3 strand snubber. The excess could get bundled up on itself as the winds go up and down. I'll try it some time.

[Paul L]

Originally Posted by a64pilot

Given slack chain and enough velocity you could pull the bow off the boat.
But I'm not understanding where the slack would come from? My little storm anchoring experience suggests things get tight and stay that way.
I do like the idea of the secondary anchor to control sailing though, sailing is an issue with my boat and I can see how if it got bad, that loads could go through the roof.

BTW, a 5/8" bridle of three strand nylon assuming both share the load, exceeds the breaking strength of my chain slightly, so I don't see the logic in going to larger line, except maybe chafing of course.

I have asked and asked, so far nobody can tell me about their chain parting, it seems as if that is a very rare event

That's true about chain, but a parting snubber is relatively common. Sometimes it's chafe, sometimes age and sometimes conditions.

[sailorboy1]

I never would worry about having enough slack chain out so that the snubber could get to max stretch. If fact in my mind that's a bad idea and all I expect my snubber to do is take the sudden loads off the system. So far as slack goes my goal really is to just be sure the hook is going to stay on the chain.

[Paul L]

Originally Posted by sailorboy1

I never would worry about having enough slack chain out so that the snubber could get to max stretch. If fact in my mind that's a bad idea and all I expect my snubber to do is take the sudden loads off the system. So far as slack goes my goal really is to just be sure the hook is going to stay on the chain.

If all you want to do is keep the hook on, then get rid of the hook and use a dyneema soft shackle. Easy to make, stronger than the snubber or the chain. Simple to put on and take off.

[four winds]

A64pilot, where the slack chain comes from?.......

It would be the remaining unused/unsnubbed chain still in the locker. After all set and snubbed, payout slack chain straight to the bottom to drag back and forth.

I have used a second anchor off the bow straight down (hammerlock) to reduce hunting with success. But don't do it regularly, most likely because of the extra work deploying two sets of gear.

Using the spare slack chain it seems could be a less labor intensive alternative. And is a benefit to quicker egress if needed.

[Calypseau]

I like the idea of "snubbers" to lessen "sailing" and jerking when at anchor - to save my sleep and my windlass. But what exactly are the parts involved? West Marine, for instance, sells "Snubber hooks" but evidently not the whole snubber system. Is it just a line tied to a snubber hook hooked on the chain at one end, and tied to a bow cleat on the other, permitting a "loop" of loose anchor chain? What is the recommended length of snubber line? Strength of line? Proper setting? My boat is 28 tons displacement; I have 200 ft of 5/16 chain. Thanks!

[boatman61]

Depends on conditions and length of snubber I have out.. if really windy I'll increase my snubber length to near max (25ft) and then drop enough chain for the weight to lower the 'pull angle' then tie a chain stopper on a bight attached to the bow deck cleats.
Normal conditions.. 10ft snubber and just enough chain to touch the water.

[thinwater]

Originally Posted by Paul L

I was sitting at anchor in the Hauraki Gulf, NZ on inauguration Eve listening to the met service up their forecast from 35kts NE gusting 45kts, to 45kts gusting 55kts. The last time we anchored in one these it turned into a true Charlie Foxtrot. There were probably 200 boats in the area and a good 30 dragged. This time we are in a Bay with 3 other boats. Anchored in 25-30ft with 225ft of chain out and a 20-25ft snubber.
This got me thinking about what is the best length of chain loop to make the snubber affective. I see 3 options.
1. Set the chain so it is just short of the max stretch length of the snubber. The chain would take affect just before the snubber broke.
2. Set the chain just longer than #1. You'd get all the snubber could give you.
3. Set a large loop way longer than #2. No real need to estimate how much real stretch the snubber has. If the snubber breaks, the boat might get some serious acceleration before the chain snaps taunt- not a good thing.

I probably end up somewhere between 2 and 3 when anchoring for a serious blow. Measuring the right length for 1 or 2 could be tough.
( in the end the winds in the anchorage we overnighted in only made it into the 30's and there was no drama. Had to move in the morning as the winds clocked and stayed high).

Interesting idea. A64 gets it, but a few do not.

The core idea is that nylon will only fail from chafe (prevent that), extreme age (prevent that) or fatigue (prevent cycling over ~ 12-15% BS). It is this latter we are discussing.

As for a hook coming off, obviously there are several ways around that (camel hitch, hocking hook, soft shackle). Since I often anchor where the hook touching the bottom is a possiblity, a non-locking system is unacceptable.

One clarification. The chain should take effect just past the fatigue limit of nylon. This is about 8-12% stretch, depending type of rope. 12-15% slack might be a good starting point. With a 30' snubber this is 3.5-4.5 feet.

As for serious acceleration, not really. Even with a large lazy loop we are talking about 2-3 feet, and the keel will be resisting. Not a concern.

As for ripping the bow off, there are 4 reasons this is not a concern:

1. The snubber will have absorbed 70-99% of the energy already in stretching to 15%. The boat will have stopped.
2. The boat will only have a short distance to accelerate.
3. The chain will still be attached to a short snubber, or could be. This snubber will be about 2x chain BS and keeps the load off the windlass. Of course, if you use a chain lock...
4. Chain stretches. Although only about 1-2% at the WLL, if you have 200 feet out, this is a few feet. This is also combined with the anchor dragging (it will move) and the snubber that stretched.

I think the OP has a very good idea, though the devil is in the details. A second snubber might be better. But as an every day practice, it makes sense; it will give you and idea of how much load is on the anchor too.

Remember that how snubbers are used and how much is needed depends very strongly on how deep the water is and how much scope is out. In shallow water (me most of the time) you need a long snubber. In deep water (over 20 feet) the chain does more and more, and by 40 feet with a lot of scope, a snubber is fading in importance. The weight of chain also matters.

Interesting.

----
Four Winds. Thee should NEVER be unsnubbed chain in the locker. When a snubber is used in strong weather the chain is always secured by either a chain lock or short snubber. Always.

[thinwater]

Nobody, not even for an anchor thread?

I thought the OP struck on something interesting.

[s/v Jedi]

parts involved:

[AiniA]

Could it be that we are over-thinking here? We use two snubbers each with its own chain hook. Chain is 3/8 BBB and snubbers are each about 30' long and attach to deck clears on either side of the bow so there is no load at all on the windlass. In 'normal' conditions, say up to 20 knots) we let out enough snubber(s) so that chain hooks are just above water level. When wind is stronger or it is rougher I let out more snubber length until the boat just feels comfortable. I have enough loose chain out in all situations that it is impossible for chain to ever get tight above the chain hooks. Seems to work well with a 40,000 lb boat anchored is anything from 6 to 80 feet of water including in terrible anchorages, eg. Easter Island.

[newhaul]

I use about 4 ft double snubber bridal and.about the.same loop of chain to ensure the.chain stays hooked on. I have had the chain grab hooks I see many use drop.the chain with a couple.good gusts and.steep waves.

[four winds]

Thinwater, I think and certainly hope you misunderstood my meaning re unsnubbed chain.

I'm tired, so won't try to state it differently.

[four winds]

Originally Posted by newhaul

I use about 4 ft double snubber bridal and.about the.same loop of chain to ensure the.chain stays hooked on. I have had the chain grab hooks I see many use drop.the chain with a couple.good gusts and.steep waves.
Attachment 141023

That's the same as my setup.

If stormy, I'll add a backup snubber with a rolling hitch to catch it if the bridle or hook fails.

[thinwater]

Originally Posted by four winds

Thinwater, I think and certainly hope you misunderstood my meaning re unsnubbed chain.

I'm tired, so won't try to state it differently.

What I understood, very possibly incorrect, is that if the snubber breaks, the rest of the chain in the locker will stream out.

What I was suggesting is that a back-up of some sort (chain lock, chain on samson post, short snubber) is standard procedure to prevent that. Normally I use a chain lock. In severe storm I would deploy a back-up snubber of heavier rope (I carry it any way--it has a different hook on it for mooring balls, saving a little work). But I though the OPs question was thought provoking, which is a good thing for forums. The idea of preventing the snubber from failing by providing a back-up near the fatugie limit is clever, and not without president.

My greatest concern with letting the slack come out of the chain as a back-up is chafe. I have seen people use too short a lazy loop and end up with the chain over the snubber (3-strand twists when it stretches unless both ends are constrained). It would work for me because I have a cat and the chain and bridle follow very different paths.