Trying to Make a Better Anchor Snubber

[James Diego]

My first thread, although I view the Forum frequently.

While cruising to Avalon, Catalina Island, California, USA in the Michelle, Formosa 41 ketch and rocking to exceptionally pushy rollers while at anchor off the Casino, I deployed my anchor snubber with 2-1/2" lines, a metal claw and fire hose chafing protection. The snubber only lasted 30 minutes before both lines snapped simultaneously and I lost my metal claw, which shocked me.

That was a good teaching experience because now I am on a quest to design a substantial anchor snubber that can handle very heavy seas for the Michelle, a heavy, long-time live-aboard, Taiwan ketch.

If anyone has a minute to send me a note on which lines, rubber shocks, metal claws and any thoughts would help me in this quest, it would be appreciated!

Respectfully,
James Diego

[CrustyChief]

Try Top Knots, mooringlines.com

[GordMay]

Greetings and welcome aboard the CF, James.

[exMaggieDrum]

Do a search on CF. There was a very good set of posts within the last 6 months and some even better referenced in that for earlier posts. You should find everything covered and give you ideas on how to go forward.

I decided to build my own snubbers out of high modulus line after several suggestions.

[evm1024]

You might take a look at the Mantus Bridle and chain hook.

Even if your snubber lines parted the Mantus chain hook would still be attached to your chain. That would be a win.

Regards!

Disclaimer - I sell mantus anchors for fun and (well not yet) profit when I'm not doing my day job.

[Cap Erict3]

I use a rolling hitch with a 50' 10 mm dynamic rope. I am a big fan.

http://www.bethandevans.com/pdf/knots_rollinghitch.pdf

https://en.m.wikipedia.org/wiki/Dynamic_rope




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Looking for another pretty place to work on the boat.

[evm1024]

Sounds like your snubbers failed due to internal heat buildup. this is why I like larger diameter snubbers of a longer length.

[Mike OReilly]

You don't say how long the snubber lines were James. 1/2" diameter seems small to me for a boat of your size. My standard snubber consists of two - 30' of 1" nylon. My storm snubbers are 1-1/2". Like Eric, I use a rolling hitch. I did use a couple of different chain hooks, but was never happy with them.

[thinwater]

Not nearly enough information about the failure.

• Water depth and scope.
• Wind strength.

Was the chain snatching up tight with each roller? It sounds like it was.

• How long was the snubber? Anything lass than a boat length and it is simply not going to be able to absorber the energy in stretch. Depending on the size of the rollers, the boat may have need 2-4 feet of movement in the snubber, which is only practical if the snubber is 10x that length (10% stretch is as much as you can ask and have it last).
• How old was the snubber? How many hours in this sort of conditions? It may have lost elasticity.

My guess is that you misunderstand the forces involved, the true nature of chain in a wind load + rollers (no stretch, catenary straightened out), and had a snubber that is far too short. However, going up one size might be good to; heavy boat.


For example, I use twin 1/2" x 25' snubbers on a 34' x 8500-pound catamaran and feel they are reasonable, though I will go a little longer and thinner next time. I use a Mantus hook and am satisfied, but I also like a soft shackle.

[James Diego]

Good idea to use the larger line! Thx for the suggestion!


James Diego

[med]

I use about 10m of 22mm nylon mooring warp as my snubber. I attach it with a bowline to a loop made by passing a small nylon cord several times through a chain link. (I never successfully got a rolling hitch to not come undone).

I then pass the warp along the exact same path as the anchor chain (i.e. over the bow roller) and then attach to a bollard close to the bow.

I then simply let out a few more metres of chain so the mooring warp is taking the full load. If the warp detaches, or chafes through, the chain is of course still there.

10m of 22mm nylon gives the right elasticity for me (52ft LOD, 67ft LOS, 32 tonnes). You can obviously use a smaller/large diameter and a longer/shorter length to tune the elasticity to what you need - although I think it is almost impossible to have too much.

I have never had significant chafe on the warp. It is only a cheap bit of nylon rope so I do not worry about chafe protection or anything else to protect it.

[autumnbreeze27]

We were over at Avalon last week with the big swell. We like Avalon in the winter when you get a deal on the mooring and they have happy hours in town. That was a nasty swell though!

We just replaced our dock lines, so we used old dock lines and a shockle snubber on one side (because I only have one) on the bow, and then rigged a flopper stopper on the main boom to port and a flopper stopper on the mizzen boom to starboard.

We still rolled pretty good every 10-20 minutes when that big set would roll in.

[RainDog]

What was the failure mode? How long were they? Those lines should be plenty is they were properly rigged and long enough. Did they chafe through at the bow roller or deck fitting?

I think a snubber should have no stretch for the part that touches the boat. I like way oversized Dyneema from the clear to just outside the roller/hawse then quality three strand from there to the chain. This almost eliminates chafe as a possible source of failure.

[med]

Originally Posted by RainDog

What was the failure mode? How long were they? Those lines should be plenty is they were properly rigged and long enough. Did they chafe through at the bow roller or deck fitting?

I think a snubber should have no stretch for the part that touches the boat. I like way oversized Dyneema from the clear to just outside the roller/hawse then quality three strand from there to the chain. This almost eliminates chafe as a possible source of failure.

You are of course right - best to have a length of no stretch whatever for the part which touches the boat. The other way is to attach the end of the stretchy thing (e.g. warp to the top of the chain just before it goes over the roller). A bit fiddly of course.

However, I have never had a really serious problem of the warp chaffing - and it is just cheap nylon stuff so is no big deal if it needs to be dumped.

[wrwakefield]

Originally Posted by James Diego

My first thread, although I view the Forum frequently.

While cruising to Avalon, Catalina Island, California, USA in the Michelle, Formosa 41 ketch and rocking to exceptionally pushy rollers while at anchor off the Casino, I deployed my anchor snubber with 2-1/2" lines, a metal claw and fire hose chafing protection. The snubber only lasted 30 minutes before both lines snapped simultaneously and I lost my metal claw, which shocked me.

That was a good teaching experience because now I am on a quest to design a substantial anchor snubber that can handle very heavy seas for the Michelle, a heavy, long-time live-aboard, Taiwan ketch.

If anyone has a minute to send me a note on which lines, rubber shocks, metal claws and any thoughts would help me in this quest, it would be appreciated!

Respectfully,
James Diego

Hi James,

I used various chain hooks and paws over the years, then went to tying the snubbers on with a rolling hitch. One time when I was trying to let out more chain in inclement conditions I realized the rolling hitch adds a degree of unwelcome complexity in the moment. [high wind, horizontal rain/hail, steep swell, dark of night, the usual...]

Since I have always rigged 2 snubbers, I decided to try a simple cow-hitch. That was 20 years ago, and it has yet to fail me. Simple to do with one long snubber line [mine is 75ft of 1/2" nylon 3-strand for a 50 ft LOA 44k lb ketch...]

The cow hitch still holds if one of two snubber lines break [e.g., chafe at the bow]. It is easy to loosen [never locks] and let more chain out sliding through the loosened cow-hitch in inclement conditions, and can be left on the chain with the snubber tails flaked and secured in a quick bail-out situation... [no knot to untie first, just loosen the cow-hitch a bit and let the chain slip through the noose...]

And you can loosen and re-set an existing cow-hitch one handed when adjusting chain length...

I have yet to have one chafe at the chain attachment point. I always planned to put a sleeve of tubular webbing or the like at the hitch in situations where there is a higher likelihood of chafing, but haven't needed to yet...

I also have a soft Spectra/Dynema [UHMWPE] shackle for the chafe resistant chain attachment point, attaching a 3-strand snubber to it using a reinforced eye in the middle of the snubber line, but haven't needed to use that yet either. It is my spare snubber for the time being...

KISS works for me so far.

Have fun experimenting.