July 28, 2014

A better anchor snubber

If your anchor rode is all chain, or a lot of chain, you should (must?) use an anchor snubber. For sailors that anchor mostly with rope, an anchor snubber is a short length of rope which you attach to your chain. It is used to take the direct anchor load off the windlass and to add a bit of elasticity to your rode and reduce shock loads.

It's the "attach to your chain" part of things that gets tricky. We've always used a simple galvanized metal chain hook. It has a few drawbacks - after a while it gets to look like the picture. Because we have a catamaran, our snubber is a bridle arrangement that goes to both bows and meets in the middle at the chain.  The legs of each bridle section are about 25' long.  I'd dutifully hook my chain hook to the chain, let out more chain until the bridle snubber took the load and call it good. If  we were anchored in less than 25' of water, and the weather was calm, the hook would end up on the bottom, and more often than not, it would detach from the chain. This was a headache to put it mildly.

So I've started using a Better soft shackle made from 1/4" spectra rope (fits inside 5/16" chain). It's easy to open and close, and never lets go of the chain. You can do it up on deck and the snubber won't pop off the chain as it goes over the bow roller. People test these shackles at well over the breaking strength of 1/4" spectra - about 7500 lbs. So it will be strong enough for a snubber. And it's cheap, never rusts, and is easy to replace if I drop the shackle in the water!

Two closing thoughts - I'm using dynamic climbing rope for the snubber. Fantastic stuff and you can easily watch it stretch 20% of more in a blow. Much stretchier than 3 strand nylon.  It really absorbs the force of a wind gust at anchor and reduces that dynamic loading on the anchor rode. This type of rope can't be easily spliced so the eye in the middle is just a seizing.

2nd thought - If you're a monohull, without a bridle, you can ignore this part. Our anchor rode is a mixture of about 160' of chain and about 160' of rope spliced to it. We don't really need a snubber when we get to the rope portion but we do use one; the bridle keeps our boat pointing straight into a strong wind when the monohulls nearby are shearing back and forth. To attach a snubber to the anchor rope, I use a 3/8" prussik loop and then attach the snubber soft shackle to the prussik. The prussik doesn't slide up the anchor rode when tightened a bit.

- Evan


Ed Z said...

I have been wondering about a solution for a catamaran with chain+rope anchor line. The bridle+chain hook seems to be the standard, but I have never really liked chain hooks, and as you point out it doesn't do much if you are scoped out past the end of the chain!

Love the soft shackle idea - question though:

When you are talking about the prussik loop - do you mean you take a separate piece of line, and use that to make the loop around the anchor rode, then attach the shackle/bridle to that loop? Does that present any issues with chafe?

Diane, Evan and Maia said...

Yes, exactly correct about the prussik. The prussik doesn't move so no real issues with chafe.

In reality, 90% of the time we're using just the 160' of chain before we get to the rope part of the rode.